Scientific Output

Over 10.000 scientific papers have been published by members of the Materials Chain since the foundation of the University Alliance Ruhr in 2010. This tremendous output is proof of the excellent environment the Ruhr Area provides for research in the field of materials science and technology.

Below, you can either scroll through the complete list of our annually published material, or search for a specific author or term via the free text search to get to know our research strengths. You can also review the publication record of every Materials Chain member via his or her personal member’s page.

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  • 2022 • 1394 The consistent coupling boundary condition for the classical micromorphic model: existence, uniqueness and interpretation of parameters
    d’Agostino, M.V. and Rizzi, G. and Khan, H. and Lewintan, P. and Madeo, A. and Neff, P.
    Continuum Mechanics and Thermodynamics 34 1393-1431 (2022)
    We consider the classical Mindlin–Eringen linear micromorphic model with a new strictly weaker set of displacement boundary conditions. The new consistent coupling condition aims at minimizing spurious influences from arbitrary boundary prescription for the additional microdistortion field P. In effect, P is now only required to match the tangential derivative of the classical displacement u which is known at the Dirichlet part of the boundary. We derive the full boundary condition, in adding the missing Neumann condition on the Dirichlet part. We show existence and uniqueness of the static problem for this weaker boundary condition. These results are based on new coercive inequalities for incompatible tensor fields with prescribed tangential part. Finally, we show that compared to classical Dirichlet conditions on u and P, the new boundary condition modifies the interpretation of the constitutive parameters. © 2022, The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.
    view abstractdoi: 10.1007/s00161-022-01126-3
  • 2022 • 1393 On Scattering of Finite-Size and Finite-Volume One-dimensional Photonic Crystal Resonator Tag for THz Identification
    Abbas, A.A. and Zantah, Y. and Kaiser, T.
    2022 5th International Workshop on Mobile Terahertz Systems, IWMTS 2022 (2022)
    doi: 10.1109/IWMTS54901.2022.9832453
  • 2022 • 1392 Performance and characteristics of modified PES-based membranes upon exposure to harsh cleaning conditions by sodium hypochlorite
    Abdel-Karim, A. and El-Kalliny, A.S. and Ahmed, S.I.A. and Souaya, E.R. and Badawy, M.I. and Ulbricht, M. and Gad-Allah, T.A.
    Egyptian Journal of Chemistry 65 315-325 (2022)
    Overcoming the increased protein fouling of polymeric polyethersulfone-based membranes (e.g. PES-PVP, PES-pluronic, and PES-Tetronic) is an essential target for wider ultrafiltration-based applications of such fabricated membranes. Hence, this study has been actively devoted to trace both performance and characteristics changes of modified PES-based membranes upon exposure to harsh cleaning conditions by sodium hypochlorite (400 ppm for 10 days). Simultaneously, different characterization tools have been adopted to study such purposes as SEM, FTIR, tensile strength, performance patterns. SEM analysis has proved the increment in pore size after contacting the fabricated membranes with NaOCl agent. However, tensile strength, contact angle, and overall porosity criteria showed a slight change. For instance, overall porosity ranged between 70-80 %, contact angle difference was about 3-4 deg, and tensile strength decrement was negligible. Further, AFM data proved that the relative roughness of all membranes did not dramatically. what is more, performance patterns in terms of pure water permeability is boosted two-three fold compared to untreated membranes with preserving BSA rejection ability (e.g. maximum BSA rejection loss is recorded for PES-T904 membrane; decrease from 70 % to about 55 %; about 21 % loss). Such preserved ultrafiltration behaviour may be ascribed to the more formed negative charge, and preservation hydrophilic nature even after NaOCl exposure. to end with, the fabricated modified PES membranes showed a preserved ultrafiltration performance after such harsh cleaning conditions. ©2022 National Information and Documentation Center (NIDOC)
    view abstractdoi: 10.21608/EJCHEM.2021.86400.4180
  • 2022 • 1391 Hydride-based thermal energy storage
    Adams, M. and Buckley, C.E. and Busch, M. and Bunzel, R. and Felderhoff, M. and Heo, T.W. and Humphries, T.D. and Jensen, T.R. and Klug, J. and Klug, K.H. and Møller, K.T. and Paskevicius, M. and Peil, S. and Peinecke, K. and She...
    Progress in Energy 4 (2022)
    doi: 10.1088/2516-1083/ac72ea
  • 2022 • 1390 Observation of optical coherence in a disordered metal-molecule interface by coherent optical two-dimensional photoelectron spectroscopy
    Aeschlimann, M. and Brixner, T. and Cinchetti, M. and Feidt, M. and Haag, N. and Hensen, M. and Huber, B. and Kenneweg, T. and Kollamana, J. and Kramer, C. and Pfeiffer, W. and Ponzoni, S. and Stadtmüller, B. and Thielen, P.
    Physical Review B 105 (2022)
    doi: 10.1103/PhysRevB.105.205415
  • 2022 • 1389 Analyzing the evolution of tool wear area in trochoidal milling of Inconel 718 using image processing methodology
    Agarwal, A. and Potthoff, N. and Shah, A.M. and Mears, L. and Wiederkehr, P.
    Manufacturing Letters 33 373-379 (2022)
    Nickel-based superalloys belong to a category of material employed for extreme conditions and exhibit high strength properties at elevated temperatures that result in poor machinability. Machining such difficult-to-cut materials like Inconel 718 leads to a high rate of tool wear, and therefore trochoidal milling toolpath is used to improve productivity and tool life. The current study analyzes the evolution of the flank wear area of the tool during trochoidal milling of Inconel 718 using an image processing methodology. It is attempted by performing experimental studies until tool failure occurs at several cutting conditions. The machining is performed through several iterations on an identical cutting path, and the number of iterations to failure is recorded. The microstructural image of a flank wear area is captured upon each iteration and processed using an image processing algorithm. It is realized that the evaluation of flank wear area can be an effective parameter to analyze tool wear. Also, the image processing methodology works effectively and can be extended during real-time machining. © 2022
    view abstractdoi: 10.1016/j.mfglet.2022.08.002
  • 2022 • 1388 Isotope effects on the dynamics of amorphous ices and aqueous phosphoric acid solutions
    Ahlmann, S. and Hoffmann, L. and Keppler, M. and Münzner, P. and Tonauer, C.M. and Loerting, T. and Gainaru, C. and Böhmer, R.
    Physical Chemistry Chemical Physics 24 14846-14856 (2022)
    doi: 10.1039/d2cp01455f
  • 2022 • 1387 Quantum Zeno manipulation of quantum dots
    Ahmadiniaz, N. and Geller, M. and König, J. and Kratzer, P. and Lorke, A. and Schaller, G. and Schützhold, R.
    Physical Review Research 4 (2022)
    doi: 10.1103/PhysRevResearch.4.L032045
  • 2022 • 1386 Poly(oxanorbornene)s bearing triphenylphosphonium and PEGylated zinc(ii) phthalocyanine with boosted photobiological activity and singlet oxygen generation
    Ahmetali, E. and Galstyan, A. and Süer, N.C. and Eren, T. and Şener, M.K.
    Polymer Chemistry 14 259-267 (2022)
    doi: 10.1039/d2py01297a
  • 2022 • 1385 PVDF membranes modified with diblock copolymer PEO-b-PMMA as additive: Effects of copolymer and barrier pore size on filtration performance and fouling in a membrane bioreactor
    Ahsani, M. and Oghyanous, F.A. and Meyer, J. and Ulbricht, M. and Yegani, R.
    Chemical Engineering Research and Design 184 678-691 (2022)
    In the present work, filtration performance and fouling behavior of four poly(vinylidene difluoride) (PVDF) membranes with different composition and molecular weight cut-off (MWCO) were investigated in a lab-scale submerged membrane bioreactor (MBR) system, treating real pharmaceutical wastewater. Poly(ethylene oxide)-block-poly(methyl methacrylate) (PEO-b-PMMA) diblock copolymer or FeCl2 or the combination of PEO-b-PMMA and FeCl2 were used as special additives during membrane formation. A 30-day filtration experiment was performed using four membranes in the same aeration tank simultaneously, and filtration performance of the membranes was investigated over the entire filtration period. Fouling parameters were calculated for all membranes and the TMP-step method was used to determine the critical flux of the membranes. Formed cake layers onto the surface of the membranes at the end of each filtration run were collected and extracellular polymeric substances (EPSs), excitation and emission matrix (EEM) fluorescence spectroscopy, and Fourier transform infrared (FTIR) spectroscopy analyses were performed for the cake layers. Collected cake layers after EPSs extraction were dried and their masses were measured to estimate anti-biofilm formation potential of the membranes. Obtained results revealed that incorporation of the PEO-b-PMMA diblock copolymer into the PVDF membrane accompany with FeCl2 salt which tailors the MWCO and prevents the increment of the pore size improves membrane performance and reduces its fouling propensity, in a way that membrane with smaller MWCO containing copolymer revealed lower flux decline, higher critical flux, higher flux recovery ratio (FRR) and lower biofilm mass per area. Moreover, EPS and EEM analyses revealed that membrane surface chemistry has considerable effect on the composition of the cake layers. Finally, chemical oxygen demand (COD) removal efficiency proved that MWCO does not have obvious effect on effluents’ quality. The present study confirms the importance of the surface chemistry and MWCO on fouling behavior of the membranes in the MBR system and reveals that the addition of the PEO-b-PMMA diblock copolymer to the PVDF membrane improves antifouling property of the membrane considerably. © 2022
    view abstractdoi: 10.1016/j.cherd.2022.05.051
  • 2022 • 1384 Nanoalloy catalysis and magnetic and optical properties: general discussion
    Aikens, C. and Amara, H. and Amendola, V. and Baletto, F. and Barcikowski, S. and Barrabés, N. and Caps, V. and Chen, F. and Cheng, D. and Chinnabathini, V.C. and Cottancin, E. and Daniel, I.T. and De Knijf, K. and Fortunelli, A....
    Faraday Discussions 242 522-541 (2022)
    doi: 10.1039/d2fd90088b
  • 2022 • 1383 Nanoalloy magnetic and optical properties, applications and structures: general discussion
    Aikens, C. and Alloyeau, D. and Amendola, V. and Amiens, C. and Andreazza, P. and Bakker, J.M. and Baletto, F. and Barcikowski, S. and Barrabés, N. and Bowker, M. and Chen, F. and Daniel, I.T. and Ernst, W.E. and Ferrando, R. and...
    Faraday Discussions 242 389-417 (2022)
    doi: 10.1039/d2fd90087d
  • 2022 • 1382 Nanoalloy structures and catalysis part 2: general discussion
    Aikens, C. and Alloyeau, D. and Amara, H. and Amendola, V. and Amiens, C. and Andreazza, P. and Baletto, F. and Barcikowski, S. and Bowker, M. and Calvo, F. and Chen, F. and Cottancin, E. and Ernst, W.E. and Farris, R. and Ferrand...
    Faraday Discussions 242 212-230 (2022)
    doi: 10.1039/d2fd90086f
  • 2022 • 1381 Controlling ambidextrous mirror symmetry breaking in photosensitive supramolecular polycatenars by alkyl-chain engineering
    Alaasar, M. and Cai, X. and Kraus, F. and Giese, M. and Liu, F. and Tschierske, C.
    Journal of Molecular Liquids 351 (2022)
    Liquid crystalline (LC) photo sensitive materials capable of forming mirror-symmetry broken mesophases are of great interest to produce nano-structured materials for optical and photonic applications. Herein we report how mirror-symmetry breaking could be controlled in photo sensitive supramolecular polycatenars by alkyl chain engineering. For this purpose, three new series of supramolecular photo-switchable multi-chain complexes (polycatenars) formed by intermolecular hydrogen bonding interaction between azopyridines with one variable terminal chain as the proton-acceptors and Y-shaped or taper shaped benzoic acids having either two or three terminal chains as the hydrogen bond-donors were synthesized. The LC self-assembly of these supramolecules was characterized by differential scanning calorimetry (DSC), polarized optical microscopy (POM) and X-ray diffraction (XRD). Depending on the number and length of terminal chains spontaneously chiral isotropic liquid (Iso1[*]) as well as two different types of three dimensional (3D) bicontinous cubic phases are observed, which are either chiral (Cubbi[*]/I23) or achiral (Cubbi/Ia3¯d). Moreover, UV light irradiation leads to the first fast and reversible photoinduced transformation between chiral and achiral 3D cubic phases as well as between a chiral crystalline and a chiral cubic liquid crystalline phase. © 2022 The Authors
    view abstractdoi: 10.1016/j.molliq.2022.118597
  • 2022 • 1380 MEAM interatomic potentials of Ni, Re, and Ni-Re alloys for atomistic fracture simulations
    Alam, M. and Lymperakis, L. and Groh, S. and Neugebauer, J.
    Modelling and Simulation in Materials Science and Engineering 30 (2022)
    Second nearest neighbor modified embedded atom method (2NN-MEAM) interatomic potentials are developed for the Ni, Re, and Ni-Re binaries. To construct the potentials, density functional theory (DFT) calculations have been employed to calculate fundamental physical properties that play a dominant role in fracture. The potentials are validated to accurately reproduce material properties that correlate with material's fracture behavior. The thus constructed potentials were applied to perform large scale simulations of mode I fracture in Ni and Ni-Re binaries with low Re content. Substitutional Re did not alter the ductile nature of crack propagation, though it resulted in a monotonous increase of the critical stress intensity factor with Re content. © 2021 The Author(s). Published by IOP Publishing Ltd.
    view abstractdoi: 10.1088/1361-651X/ac3a15
  • 2022 • 1379 Fe3+ -hosting carbon phases in the deep Earth
    Albers, C. and Sakrowski, R. and Libon, L. and Spiekermann, G. and Winkler, B. and Schmidt, C. and Bayarjargal, L. and Cerantola, V. and Chariton, S. and Giordano, N. and Gretarsson, H. and Kaa, J. and Liermann, H.-P. and Sunderma...
    Physical Review B 105 (2022)
    Iron-bearing carbonates play an important role in Earth's carbon cycle. Owing to their stability at mantle conditions, recently discovered iron carbonates with tetrahedrally coordinated carbon atoms are candidates for carbon storage in the deep Earth. The carbonates' iron oxidation and spin state at extreme pressure and temperature conditions contribute to the redox conditions and element partitioning in the deep mantle. By laser heating FeCO3 at pressures of about 83 GPa, Fe43+C3O12 and Fe22+Fe23+C4O13 were synthesized and then investigated by x-ray emission spectroscopy to elucidate their spin state, both in situ and temperature quenched. Our experimental results show both phases in a high-spin state at all pressures and over the entire temperature range investigated, i.e., up to 3000 K. The spin state is conserved after temperature quenching. A formation path is favored where Fe43+C3O12 forms first and then reacts to Fe22+Fe23+C4O13, most likely accompanied by the formation of oxides. Density functional theory calculations of Fe22+Fe23+C4O13 at 80 GPa confirm the experimental findings with both ferric and ferrous iron in high-spin state with antiferromagnetic order at 80 GPa. As the intercrystalline cation partitioning between the Fe-bearing carbonates and the surrounding perovskite and ferropericlase depends on the spin state of the iron, an understanding of the redox conditions prevalent in subducted slab regions in the lower mantle has to take the latter into account. Especially, Fe22+Fe23+C4O13 may play a key role in subducted material in the lower mantle, potentially with a similar role as silicate perovskite. © 2022 American Physical Society.
    view abstractdoi: 10.1103/PhysRevB.105.085155
  • 2022 • 1378 Non-resonant and resonant X-ray emission at high pressure using a von Hámos setup: The case of FeO
    Albers, C. and Thiering, N. and Sakrowski, R. and Gretarsson, H. and Kaa, J. and Sundermann, M. and Tolan, M. and Wilke, M. and Sternemann, C.
    Journal of Physics: Conference Series 2380 (2022)
    doi: 10.1088/1742-6596/2380/1/012128
  • 2022 • 1377 State of the art energy conversion at the nanointerface: general discussion
    Albrecht, T. and Bohn, P. and Buckingham, M.A. and Cao, X.E. and Chen, D. and Chen, Q. and Corva, M. and Edwards, M.A. and Kamali, A.R. and Kanoufi, F. and Krause, S. and Linfield, S. and Liu, X. and Ma, H. and Mao, B.-W. and Pand...
    Faraday Discussions 233 112-121 (2022)
    doi: 10.1039/d2fd90002e
  • 2022 • 1376 Electrochemical data mining: from information to knowledge: general discussion
    Albrecht, T. and Cao, X.E. and Chen, D. and Corva, M. and Edwards, M.A. and Ewing, A. and Fornasaro, S. and Gooding, J.J. and Gundry, L. and Hirano-Iwata, A. and Jeffcoat, G. and Kamali, A.R. and Kanoufi, F. and Lemay, S.G. and Li...
    Faraday Discussions 233 58-76 (2022)
    doi: 10.1039/d2fd90001g
  • 2022 • 1375 Millimeter-Wave Retro-Directive Frequency Coded Lens by Curved One-Dimensional Photonic Crystal Resonator
    Alhaj Abbas, A. and Zantah, Y. and Abuelhaija, A. and Kaiser, T.
    IEEE Access 10 132988-133000 (2022)
    doi: 10.1109/ACCESS.2022.3226124
  • 2022 • 1374 Terahertz Band Data Communications using Dielectric Rod Waveguide
    Ali, M. and Tebart, J. and Rivera-Lavado, A. and Lioubtchenko, D. and Garcia-Muñoz, L.E. and Stöhr, A. and Carpintero, G.
    Optics InfoBase Conference Papers (2022)
    A terahertz data link is presented using dielectric rod waveguide (DRW) at 300 GHz and complex modulations for speeds up to 120 Gbps. Performance comparison with WR-3 rectangular waveguide validates the low-dispersion behaviour of DRW. © Optica Publishing Group 2022, © 2022 The Author(s)
    view abstract
  • 2022 • 1373 Electrochemical Reduction of CO2 on Au Electrocatalysts in a Zero-Gap, Half-Cell Gas Diffusion Electrode Setup: a Systematic Performance Evaluation and Comparison to an H-cell Setup**
    Alinejad, S. and Quinson, J. and Wiberg, G.K.H. and Schlegel, N. and Zhang, D. and Li, Y. and Reichenberger, S. and Barcikowski, S. and Arenz, M.
    ChemElectroChem 9 (2022)
    doi: 10.1002/celc.202200341
  • 2022 • 1372 Spray-flame-synthesized Sr- and Fe-substituted LaCoO3perovskite nanoparticles with enhanced OER activities
    Alkan, B. and Braun, M. and Landrot, G. and Rüdiger, O. and Andronescu, C. and DeBeer, S. and Schulz, C. and Wiggers, H.
    Journal of Materials Science 57 18923-18936 (2022)
    doi: 10.1007/s10853-022-07738-z
  • 2022 • 1371 Nanoalloy structures and catalysis part 1: general discussion
    Alloyeau, D. and Amendola, V. and Amiens, C. and Andreazza, P. and Bakker, J. and Baletto, F. and Barcikowski, S. and Barrabés, N. and Bowker, M. and Chen, F. and Cottancin, E. and Ernst, W.E. and Ferrando, R. and Förster, G.D. ...
    Faraday Discussions 242 106-128 (2022)
    doi: 10.1039/d2fd90085h
  • 2022 • 1370 Identification of non-traditional coordination environments for iron ions in nickel hydroxide lattices
    Alsaç, E.P. and Zhou, K. and Rong, W. and Salamon, S. and Landers, J. and Wende, H. and Smith, R.D.L.
    Energy and Environmental Science 15 (2022)
    The uniformity in electrochemical behavior of FexNi1−x(OH)2 is remarkable given the diversity in published fabrication protocols, composition-dependent structural changes, and multitude of electrochemical reaction mechanisms proposed. We use complementary techniques to show that multiple unique Fe(iii) coordination environments exist in FexNi1−x(OH)2 synthesized by alkaline precipitation. Samples synthesized with formamide added to the reaction vessel yield Mössbauer and Raman spectra consistent with Fe(iii) successfully incorporated into the Ni(OH)2 lattice. Additional spectroscopic features emerge for samples synthesized in the absence of formamide, revealing a second Fe(iii) coordination environment. Correlations in structural information derived from the numerous characterization techniques suggest that the secondary environment sits atop the 2-dimensional Ni(OH)2 sheets. X-ray diffraction and X-ray absorption spectroscopy fail to resolve this second site, but show that Fe(iii) induces a non-uniform structural contraction that distorts the Ni(OH)2 lattice for all samples. Electrocatalytic oxygen evolution is qualitatively similar for both sample series, but samples synthesized in the presence of formamide consistently outperform those from conventional pH precipitation. Iron ions within the Ni(OH)2 lattice are therefore deemed to be the catalytically relevant structural feature. The identification of a secondary iron site demonstrates that qualitative similarities in electrochemical behavior mask quantitative differences in structure and electrocatalytic competence. © 2022 The Royal Society of Chemistry.
    view abstractdoi: 10.1039/d2ee00396a
  • 2022 • 1369 COMPARATIVE STUDY ON THE EFFECT OF SELECTED DISPERSION TECHNOLOGIES FOR FUEL CELL INK PREPARATION ON THE OVERALL PEMFC PROCESS CHAIN
    Amin, A.S. and Özcan, F. and Segets, D.
    Proceedings of WHEC 2022 - 23rd World Hydrogen Energy Conference: Bridging Continents by H2 733-735 (2022)
  • 2022 • 1368 Trendbericht Organische Chemie 2022
    Andexer, J.N. and Beifuss, U. and Brasholz, M. and Breinbauer, R. and Breugst, M. and Dumele, O. and Ernst, M. and Ganardi, R. and Giese, M. and Gulder, T.A.M. and Hüttel, W. and Kath-Schorr, S. and Körber, K. and Kordes, M. and...
    Nachrichten aus der Chemie 70 42-69 (2022)
    doi: 10.1002/nadc.20224122453
  • 2022 • 1367 Metallographic preparation methods for the Mg based system Mg-Al-Ca and its Laves phases
    Andre, D. and Freund, M. and Rehman, U. and Delis, W. and Felten, M. and Nowak, J. and Tian, C. and Zubair, M. and Tanure, L. and Abdellaoui, L. and Springer, H. and Best, J.P. and Zander, D. and Dehm, G. and Sandlöbes-Haut, S. a...
    Materials Characterization 192 (2022)
    doi: 10.1016/j.matchar.2022.112187
  • 2022 • 1366 Spin helices in GaAs quantum wells: Interplay of electron density, spin diffusion, and spin lifetime
    Anghel, S. and Poshakinskiy, A.V. and Schiller, K. and Yusa, G. and Mano, T. and Noda, T. and Betz, M.
    Journal of Applied Physics 132 (2022)
    doi: 10.1063/5.0097426
  • 2022 • 1365 A chiral one-dimensional atom using a quantum dot in an open microcavity
    Antoniadis, N.O. and Tomm, N. and Jakubczyk, T. and Schott, R. and Valentin, S.R. and Wieck, A.D. and Ludwig, A. and Warburton, R.J. and Javadi, A.
    npj Quantum Information 8 (2022)
    In a chiral one-dimensional atom, a photon propagating in one direction interacts with the atom; a photon propagating in the other direction does not. Chiral quantum optics has applications in creating nanoscopic single-photon routers, circulators, phase-shifters, and two-photon gates. Here, we implement chiral quantum optics using a low-noise quantum dot in an open microcavity. We demonstrate the non-reciprocal absorption of single photons, a single-photon diode. The non-reciprocity, the ratio of the transmission in the forward-direction to the transmission in the reverse direction, is as high as 10.7 dB. This is achieved by tuning the photon-emitter coupling in situ to the optimal operating condition (β = 0.5). Proof that the non-reciprocity arises from a single quantum emitter lies in the photon statistics—ultralow-power laser light propagating in the diode’s reverse direction results in a highly bunched output (g(2)(0) = 101), showing that the single-photon component is largely removed. © 2022, The Author(s).
    view abstractdoi: 10.1038/s41534-022-00545-z
  • 2022 • 1364 Hansen parameter evaluation for the characterization of titania photocatalysts using particle size distributions and combinatorics
    Anwar, O. and Bapat, S. and Ahmed, J. and Xie, X. and Sun, J. and Segets, D.
    Nanoscale 14 13593-13607 (2022)
    Titania photocatalysts have great potential as remediators of air pollution. Although various aspects of photocatalyst synthesis, adsorption and photoactivity have been investigated, a thorough understanding of the particle surface behavior has not yet been fully realized. In order to learn more about the principles behind the surface behavior, we investigate the Hansen solubility/similarity parameters (HSPs) for analyzing and evaluating three photocatalysts synthesized by the gas phase method, solvothermal reaction and sol-gel method, respectively. A particle size distribution-based categorization scheme is introduced for characterizing each material's Hansen parameters based on its interaction with a list of selected probe liquids. The latter was deduced from particle size distributions assessed by analytical centrifugation. Subsequent comparison of the Hansen parameters of the investigated materials shows how HSPs can potentially be used as a model for predicting the pollutant adsorption behavior on the photocatalyst surface. This serves as a first step in heading towards an improved understanding of the particle behavior and translating it into a knowledge-based design, i.e., synthesis and hybridization of novel photocatalysts. © 2022 The Royal Society of Chemistry.
    view abstractdoi: 10.1039/d2nr02711a
  • 2022 • 1363 Depth-Adjustable Magnetostructural Phase Transition in Fe60V40Thin Films
    Anwar, M.S. and Cansever, H. and Boehm, B. and Gallardo, R.A. and Hübner, R. and Zhou, S. and Kentsch, U. and Rauls, S. and Eggert, B. and Wende, H. and Potzger, K. and Fassbender, J. and Lenz, K. and Lindner, J. and Hellwig, O. ...
    ACS Applied Electronic Materials 4 3860-3869 (2022)
    Phase transitions occurring within spatially confined regions can be useful for generating nanoscale material property modulations. Here we describe a magneto-structural phase transition in a binary alloy, where a structural transition from short-range order (SRO) to body centered cubic (bcc) results in the formation of depth-adjustable ferromagnetic layers, which reveal application-relevant magnetic properties of high saturation magnetization (Ms) and low Gilbert damping (α). Here we use Fe60V40binary alloy films which transform from initially Ms= 17 kA/m (SRO structure) to 747 kA/m (bcc structure) driven by atomic displacements caused by penetrating ions. Simulations show that an estimated ∼1 displacement per atom triggers a structural transition, forming homogeneous ferromagnetic layers. The thickness of a ferromagnetic layer increases as a step-like function of the ion fluence. Microwave excitations of the ferromagnetic/non-ferromagnetic layered system reveals an α = 0.0027 ± 0.0001. The combination of nanoscale spatial confinement, low α, and high Msprovides a pathway for the rapid patterning of magnetic and microwave device elements. © 2022 American Chemical Society.
    view abstractdoi: 10.1021/acsaelm.2c00499
  • 2022 • 1362 A new dual matrix burner for one-dimensional investigation of aerosol flames
    Apazeller, S. and Gonchikzhapov, M. and Nanjaiah, M. and Kasper, T. and Wlokas, I. and Wiggers, H. and Schulz, C.
    Proceedings of the Combustion Institute (2022)
    In spray-flame synthesis of nanoparticles, a precise understanding of the reaction processes is necessary to find optimal process parameters for the formation of the desired products. Coupling the chemistries of flame, solvent, and gas-phase species initially formed from the particle precursor in combination with the complex flow geometry of the spray flame means a special challenge for the modeling of the reaction processes. A new burner has been developed that is capable to observe the reaction of precursor solutions frequently used in spray-flame synthesis. The burner provides an almost flat, laminar, and steady flame with homogeneous addition of a fine aerosol and thus enables detailed investigation and modeling of the coupled reactions independent of spray formation and turbulent mixing. With its two separate supply channel matrices, the burner also enables the use of reactants that would otherwise react with each other already before reaching the flame. These features enable the investigation of a wide range of flame-based synthesis methods for nanoparticles and, due to the flat-flame geometry, kinetics models for these processes can be developed and validated. This work describes the matrix burner development and its gas flow optimization by simulation. Droplet-size distributions generated by ultrasonic nebulization and their interaction with the burner structure are investigated by phase-Doppler anemometry. As an example for nanoparticle-forming flames from solutions, iron-oxide nanoparticle-generating flames using iron(III) nitrate nonahydrate dissolved in 1-butanol were investigated. This effort includes measurements of two-dimensional maps of the flame temperature by a thermocouple and height-dependent concentration profiles of the main species by time-of-flight mass spectrometry. Experimental data are compared with 1D simulations using a reduced reaction mechanism. The results show that the new burner is well suited for the development of reaction models for precursors supplied in the liquid phase usually applied in spray-flame synthesis configurations. © 2022 Elsevier Ltd. All rights reserved.
    view abstractdoi: 10.1016/j.proci.2022.07.166
  • 2022 • 1361 Entangling a Hole Spin with a Time-Bin Photon: A Waveguide Approach for Quantum Dot Sources of Multiphoton Entanglement
    Appel, M.H. and Tiranov, A. and Pabst, S. and Chan, M.L. and Starup, C. and Wang, Y. and Midolo, L. and Tiurev, K. and Scholz, S. and Wieck, A.D. and Ludwig, Ar. and Sørensen, A.S. and Lodahl, P.
    Physical Review Letters 128 (2022)
    Deterministic sources of multiphoton entanglement are highly attractive for quantum information processing but are challenging to realize experimentally. In this Letter, we demonstrate a route toward a scaleable source of time-bin encoded Greenberger-Horne-Zeilinger and linear cluster states from a solid-state quantum dot embedded in a nanophotonic crystal waveguide. By utilizing a self-stabilizing double-pass interferometer, we measure a spin-photon Bell state with (67.8±0.4)% fidelity and devise steps for significant further improvements. By employing strict resonant excitation, we demonstrate a photon indistinguishability of (95.7±0.8)%, which is conducive to fusion of multiple cluster states for scaling up the technology and producing more general graph states. © 2022 American Physical Society.
    view abstractdoi: 10.1103/PhysRevLett.128.233602
  • 2022 • 1360 Parallel shape divergence between ecotypes of the limpet Nacella concinna along the Antarctic Peninsula: a new model species for parallel evolution?
    de Aranzamendi, M.C. and Martínez, J.J. and Held, C. and Sahade, R.
    Zoology 150 (2022)
    Parallel phenotypic divergence is the independent differentiation between phenotypes of the same lineage or species occupying ecologically similar environments in different populations. We tested in the Antarctic limpet Nacella concinna the extent of parallel morphological divergence in littoral and sublittoral ecotypes throughout its distribution range. These ecotypes differ in morphological, behavioural and physiological characteristics. We studied the lateral and dorsal outlines of shells and the genetic variation of the mitochondrial gene Cytochrome Oxidase subunit I from both ecotypes in 17 sample sites along more than 2,000 km. The genetic data indicate that both ecotypes belong to a single evolutionary lineage. The magnitude and direction of phenotypic variation differ between ecotypes across sample sites; completely parallel ecotype-pairs (i.e., they diverge in the same magnitude and in the same direction) were detected in 84.85% of lateral and 65.15% in dorsal view comparisons. Besides, specific traits (relative shell height, position of shell apex, and elliptical/pear-shape outline variation) showed high parallelism. We observed weak morphological covariation between the two shape shell views, indicating that distinct evolutionary forces and environmental pressures could be acting on this limpet shell shape. Our results demonstrate there is a strong parallel morphological divergence pattern in N. concinna along its distribution, making this Antarctic species a suitable model for the study of different evolutionary forces shaping the shell evolution of this limpet. © 2021 Elsevier GmbH
    view abstractdoi: 10.1016/j.zool.2021.125983
  • 2022 • 1359 The effect of Caspian Sea water on mechanical properties and durability of concrete containing rice husk ash, nano SiO 2 , and nano Al 2O 3
    Arasteh-Khoshbin, O. and Seyedpour, S.M. and Ricken, T.
    Scientific Reports 12 (2022)
    doi: 10.1038/s41598-022-24304-4
  • 2022 • 1358 Competing Effects in the Hydration Mechanism of a Garnet-Type Li7La3Zr2O12 Electrolyte
    Arinicheva, Y. and Guo, X. and Gerhards, M.-T. and Tietz, F. and Fattakhova-Rohlfing, D. and Finsterbusch, M. and Navrotsky, A. and Guillon, O.
    Chemistry of Materials 34 1473-1480 (2022)
    Li-ion conducting oxides (Li7La3Zr2O12, LLZO) with a cubic garnet-type structure are among the most promising candidates to be used as solid electrolytes in all-solid-state Li batteries. However, the environmental instability of the electrolyte, induced by interaction between the material and gas molecules commonly found in air, namely, water and carbon dioxide, poses challenges for its manufacture and application. Herein, a combined experimental kinetic and thermodynamic study was performed as a function of temperature to clarify the mechanism of hydration of a garnet-type LLZO electrolyte in moist air. It was found that the kinetics of LLZO hydration is diffusion-limited and the hydration mechanism at room temperature and at higher temperatures differs. The hydration of LLZO increases up to 200 °C. Above this temperature, stagnation of water uptake is observed due to the onset of a competing dehydration process. The dehydration of LLZO takes place up to 400 °C. The partial pressure of water significantly affects the extent of hydration. Expanding this combined kinetic and thermodynamic approach to LLZO materials with a variety of chemical compositions and morphologies would allow prediction of their reactivity in a humid atmosphere and adjustment of the processing conditions accordingly to meet the requirements of technological applications. © 2022 American Chemical Society
    view abstractdoi: 10.1021/acs.chemmater.1c02581
  • 2022 • 1357 Novel insights into PORCN mutations, associated phenotypes and pathophysiological aspects
    Arlt, A. and Kohlschmidt, N. and Hentschel, A. and Bartels, E. and Groß, C. and Töpf, A. and Edem, P. and Szabo, N. and Sickmann, A. and Meyer, N. and Schara-Schmidt, U. and Lau, J. and Lochmüller, H. and Horvath, R. and Oktay,...
    Orphanet Journal of Rare Diseases 17 (2022)
    Background: Goltz syndrome (GS) is a X-linked disorder defined by defects of mesodermal- and ectodermal-derived structures and caused by PORCN mutations. Features include striated skin-pigmentation, ocular and skeletal malformations and supernumerary or hypoplastic nipples. Generally, GS is associated with in utero lethality in males and most of the reported male patients show mosaicism (only three non-mosaic surviving males have been described so far). Also, precise descriptions of neurological deficits in GS are rare and less severe phenotypes might not only be caused by mosaicism but also by less pathogenic mutations suggesting the need of a molecular genetics and functional work-up of these rare variants. Results: We report two cases: one girl suffering from typical skin and skeletal abnormalities, developmental delay, microcephaly, thin corpus callosum, periventricular gliosis and drug-resistant epilepsy caused by a PORCN nonsense-mutation (c.283C > T, p.Arg95Ter). Presence of these combined neurological features indicates that CNS-vulnerability might be a guiding symptom in the diagnosis of GS patients. The other patient is a boy with a supernumerary nipple and skeletal anomalies but also, developmental delay, microcephaly, cerebral atrophy with delayed myelination and drug-resistant epilepsy as predominant features. Skin abnormalities were not observed. Genotyping revealed a novel PORCN missense-mutation (c.847G > C, p.Asp283His) absent in the Genome Aggregation Database (gnomAD) but also identified in his asymptomatic mother. Given that non-random X-chromosome inactivation was excluded in the mother, fibroblasts of the index had been analyzed for PORCN protein-abundance and -distribution, vulnerability against additional ER-stress burden as well as for protein secretion revealing changes. Conclusions: Our combined findings may suggest incomplete penetrance for the p.Asp283His variant and provide novel insights into the molecular etiology of GS by adding impaired ER-function and altered protein secretion to the list of pathophysiological processes resulting in the clinical manifestation of GS. © 2022, The Author(s).
    view abstractdoi: 10.1186/s13023-021-02068-w
  • 2022 • 1356 Improving the separation of guaiacol from n-hexane by adding choline chloride to glycol extracting agents
    Arroyo-Avirama, A.F. and Ormazábal-Latorre, S. and Jogi, R. and Gajardo-Parra, N.F. and Pazo-Carballo, C. and Ascani, M. and Virtanen, P. and Garrido, J.M. and Held, C. and Mäki-Arvela, P. and Canales, R.I.
    Journal of Molecular Liquids 355 (2022)
    doi: 10.1016/j.molliq.2022.118936
  • 2022 • 1355 IoT-PROD 2022: First International Workshop on Internet of Things Pervasive Real-World Deployments - Welcome and Committees: Welcome Message
    Artemenko, A. and Bicocchi, N. and Picone, M. and Weis, T. and Zdankin, P.
    2022 IEEE International Conference on Pervasive Computing and Communications Workshops and other Affiliated Events, PerCom Workshops 2022 i-ii (2022)
    doi: 10.1109/PerComWorkshops53856.2022.9767276
  • 2022 • 1354 Influence of Mo/Cr ratio on the lamellar microstructure and mechanical properties of as-cast Al0.75CoCrFeNi compositionally complex alloys
    Asabre, A. and Gemagami, P. and Parsa, A.B. and Wagner, C. and Kostka, A. and Laplanche, G.
    Journal of Alloys and Compounds 899 (2022)
    The Al0.75CoCrFeNi alloy (Al16Co21Cr21Fe21Ni21 in at.%) presents a lamellar microstructure in the as-cast state consisting of a spinodally-decomposed B2/BCC matrix and Widmanstätten-type FCC plates. In this study, to retain the lamellar microstructure and improve tensile strength, Al16Co21Cr21-xFe21Ni21Mox alloys with x ≤ 10 at.% were investigated. For x = 2 at.%, the Widmanstätten microstructure changed into a vermicular one due to the stabilization of the BCC phase. With increasing the Mo/Cr ratio, the BCC phase transformed into topologically close-packed (TCP) phases, i.e., σ phase for x = 4 at.% and R phase for x ≥ 6 at.%, whose volume fractions increases with x. The as-cast alloys with x = 10 and 4 at.% presented the largest microhardness of ~600 HV0.5. The former had the highest volume fraction in TCP phases, which are hard and brittle while the latter presented the finest microstructure (enhanced phase boundary strengthening). While the alloys with x > 4 at.% were too brittle to machine tensile specimens, the others were tested between 20 and 700 °C. The ultimate tensile strength increased with increasing x up to ~1460 MPa for x = 4 at.% at 400 °C. At 700 °C, the strength of all alloys significantly decreased due to the softening of the B2 phase. Most of them had limited ductility and showed intergranular fracture except for x = 4 at.% presenting pronounced necking with ~38% ductility. The latter effect was attributed to the occurrence of interfacial sliding resulting in cavitation at grain boundaries and interphase boundaries. © 2021 The Author(s)
    view abstractdoi: 10.1016/j.jallcom.2021.163183
  • 2022 • 1353 Tensile strength deterioration of PVC coated PET woven fabrics under single and multiplied artificial weathering impacts and cyclic loading
    Asadi, H. and Uhlemann, J. and Stranghoener, N. and Ulbricht, M.
    Construction and Building Materials 342 (2022)
    This paper investigates the tensile strength degradation of architectural PVC coated PET woven fabrics exposed to single and combined artificial weathering impacts and cyclic loading. The uniaxial tensile strength sensitivity to different weathering stressors such as UV light, humidity, and temperature plus cyclic loading was determined. Furthermore, the physicochemical changes were traced by Fourier transform infrared spectroscopy and scanning electron microscopy. The results reveal the key role of photodegradation on the tensile strength deterioration of PET yarns, while incorporation of cyclic loading cannot exacerbate this degradation rate remarkably. Weathering impacts decrease the stiffness (Esecant) either individually or collectively while a single impact of humidity or temperature leads to comparably low changes of the tensile strength. Strength modification factors based on the draft standard prCEN/TS 19102:2022-05 have been calculated covering all surveyed artificial weathering test results. The presented study provides a better understanding of the weathering performance of PET-PVC fabrics under various attacks. © 2022 Elsevier Ltd
    view abstractdoi: 10.1016/j.conbuildmat.2022.127843
  • 2022 • 1352 Weathering-induced ageing strength modification factors for PET-PVC-fabrics
    Asadi, H. and Uhlemann, J. and Stranghoener, N.
    IABSE Symposium Prague, 2022: Challenges for Existing and Oncoming Structures - Report 963-969 (2022)
    The design process of tension fabric structures must consider changes of the material properties due to long-term exposure to the environment. In line with the harmonized view of the Ultimate Limit State verification which is currently developed in the framework of a novel European design standard for membrane structures, a strength modification factor considering ageing effects is proposed to describe the deterioration arising from environmental impacts. The objective of this paper is to broaden the data basis for the long-term behaviour of a typical structural membrane made of PET-PVC material for environmental impacts. In this way, an overview about different data achieved from two practical applications and experimental artificial weathering tests is presented for the destructive effect of weathering on tensile strength of coated woven fabrics. Finally, related weathering-induced ageing modification factors are derived. © 2022 IABSE Symposium Prague, 2022: Challenges for Existing and Oncoming Structures - Report. All rights reserved.
    view abstract
  • 2022 • 1351 Calculation of Multiphase Equilibria Containing Mixed Solvents and Mixed Electrolytes: General Formulation and Case Studies
    Ascani, M. and Sadowski, G. and Held, C.
    Journal of Chemical and Engineering Data 67 1972-1984 (2022)
    doi: 10.1021/acs.jced.1c00866
  • 2022 • 1350 Prediction of pH in multiphase multicomponent systems with ePC-SAFT advanced
    Ascani, M. and Pabsch, D. and Klinksiek, M. and Gajardo-Parra, N. and Sadowski, G. and Held, C.
    Chemical Communications 58 8436-8439 (2022)
    doi: 10.1039/d2cc02943j
  • 2022 • 1349 Selective Disruption of Survivin's Protein-Protein Interactions: A Supramolecular Approach Based on Guanidiniocarbonylpyrrole
    Aschmann, D. and Vallet, C. and Tripathi, S.K. and Ruiz-Blanco, Y.B. and Brabender, M. and Schmuck, C. and Sanchez-Garcia, E. and Knauer, S.K. and Giese, M.
    ChemBioChem 23 (2022)
    Targeting specific protein binding sites to interfere with protein-protein interactions (PPIs) is crucial for the rational modulation of biologically relevant processes. Survivin, which is highly overexpressed in most cancer cells and considered to be a key player of carcinogenesis, features two functionally relevant binding sites. Here, we demonstrate selective disruption of the Survivin/Histone H3 or the Survivin/Crm1 interaction using a supramolecular approach. By rational design we identified two structurally related ligands (LNES and LHIS), capable of selectively inhibiting these PPIs, leading to a reduction in cancer cell proliferation. © 2022 The Authors. ChemBioChem published by Wiley-VCH GmbH
    view abstractdoi: 10.1002/cbic.202100618
  • 2022 • 1348 Genomic palaeoparasitology traced the occurrence of Taenia asiatica in ancient Iran (Sassanid Empire, 2th cent. CE–6th cent. CE)
    Askari, Z. and Ruehli, F. and Bouwman, A. and Shariati, V. and Naddaf, S.R. and Otranto, D. and Mas-Coma, S. and Rezaeian, M. and Boenke, N. and Stöllner, T. and Aali, A. and Mobedi, I. and Mowlavi, G.
    Scientific Reports 12 (2022)
    Palaeoparasitology investigates parasitological infections in animals and humans of past distance by examining biological remains. Palaeofaeces (or coprolites) are biological remains that provide valuable information on the disease, diet, and population movements in ancient times. Today, advances in detecting ancient DNA have cast light on dark corners that microscopy could never reach. The archaeological site of the Chehrabad salt mine of Achaemenid (550–330 BC) and Sassanid (third–seventh century AD) provides remains of various biotic and abiotic samples, including animal coprolites, for multidisciplinary studies. In the present work, we investigated coprolites for helminth eggs and larvae by microscopy and traced their biological agents’ DNA by Next Generation Sequencing. Our results revealed various helminths, including Taenia asiatica, the species introduced in the 1990s. Implementing advanced modern molecular techniques like NGS gives a paramount view of pathogenic agents in space and time. © 2022, The Author(s).
    view abstractdoi: 10.1038/s41598-022-10690-2
  • 2022 • 1347 Statistical Quantification of Differential Privacy: A Local Approach
    Askin, O. and Kutta, T. and Dette, H.
    Proceedings - IEEE Symposium on Security and Privacy 2022-May 402-421 (2022)
    doi: 10.1109/SP46214.2022.9833689
  • 2022 • 1346 Does carbon price volatility affect European stock market sectors? A connectedness network analysis
    Aslan, A. and Posch, P.N.
    Finance Research Letters 50 (2022)
    We investigate how the volatility of carbon emission allowance (EUA) prices affects European stock market sectors. We employ a connectedness network analysis on prices of EUA futures and FTSE stock market sector indices and find that the EUA is mostly a net receiver of volatility connectedness and significantly receives volatility across most sectors during the recent European energy crisis. © 2022 Elsevier Inc.
    view abstractdoi: 10.1016/j.frl.2022.103318
  • 2022 • 1345 How Do Investors Value Sustainability? A Utility-Based Preference Optimization
    Aslan, A. and Posch, P.N.
    Sustainability (Switzerland) 14 (2022)
    doi: 10.3390/su142315963
  • 2022 • 1344 Three-dimensional phase-field modeling of brittle fracture using an adaptive octree-based scaled boundary finite element approach
    Assaf, R. and Birk, C. and Natarajan, S. and Gravenkamp, H.
    Computer Methods in Applied Mechanics and Engineering 399 (2022)
    doi: 10.1016/j.cma.2022.115364
  • 2022 • 1343 Simultaneous Multi-Property Probing During Magneto-Structural Phase Transitions: An Element-Specific and Macroscopic Hysteresis Characterization at ID12 of the ESRF
    Aubert, A. and Skokov, K. and Gomez, G. and Chirkova, A. and Radulov, I. and Wilhelm, F. and Rogalev, A. and Wende, H. and Gutfleisch, O. and Ollefs, K.
    IEEE Transactions on Instrumentation and Measurement 71 (2022)
    We present a new instrument for advanced magnetic studies based on the high field X-ray magnetic circular dichroism (XMCD) end-station developed at the beamline ID12 of the European Synchrotron Radiation Facility (ESRF, Grenoble, France). It offers a unique possibility to measure simultaneously element-specific and macroscopic properties related to magnetic, electronic, and structural degrees of freedom of magnetic materials. Under strictly the same experimental conditions, one can measure the XMCD response, macroscopic magnetization, volume changes, and caloric properties of a magnetic material as a function of magnetic field (up to 17 T) and temperature (5-325 K). To illustrate the performance of this new instrument, we present a case study of an equiatomic FeRh alloy across the first-order magneto-structural transition. This development is the first step toward a new fully dedicated end-station based on a 7 T split-coil superconducting magnet with an additional capability to perform X-ray diffraction experiments. © 1963-2012 IEEE.
    view abstractdoi: 10.1109/TIM.2022.3157001
  • 2022 • 1342 Origin of the different reactivity of the high-valent coinage-metal complexes [RCuiiiMe3]− and [RAgiiiMe3]− (R=allyl)**
    Auth, T. and Stein, C.J. and O'Hair, R.A.J. and Koszinowski, K.
    Chemistry - A European Journal 28 (2022)
    High-valent tetraalkylcuprates(iii) and -argentates(iii) are key intermediates of copper- and silver-mediated C−C coupling reactions. Here, we investigate the previously reported contrasting reactivity of [RMiiiMe3]− complexes (M=Cu, Ag and R=allyl) with energy-dependent collision-induced dissociation experiments, advanced quantum-chemical calculations and kinetic computations. The gas-phase fragmentation experiments confirmed the preferred formation of the [RCuMe]− anion upon collisional activation of the cuprate(iii) species, consistent with a homo-coupling reaction, whereas the silver analogue primarily yielded [AgMe2]−, consistent with a cross-coupling reaction. For both complexes, density functional theory calculations identified one mechanism for homo coupling and four different ones for cross coupling. Of these pathways, an unprecedented concerted outer-sphere cross coupling is of particular interest, because it can explain the formation of [AgMe2]− from the argentate(iii) species. Remarkably, the different C−C coupling propensities of the two [RMiiiMe3]− complexes become only apparent when properly accounting for the multi-configurational character of the wave function for the key transition state of [RAgMe3]−. Backed by the obtained detailed mechanistic insight for the gas-phase reactions, we propose that the previously observed cross-coupling reaction of the silver complex in solution proceeds via the outer-sphere mechanism. © 2021 The Authors. Chemistry - A European Journal published by Wiley-VCH GmbH
    view abstractdoi: 10.1002/chem.202103130
  • 2022 • 1341 3D modeling of generalized Newtonian fluid flow with data assimilation using the least-squares finite element method
    Averweg, S. and Schwarz, A. and Schwarz, C. and Schröder, J.
    Computer Methods in Applied Mechanics and Engineering 392 (2022)
    In this contribution we present a least-squares finite element formulation to model steady-state flow of incompressible, non-Newtonian fluids in three dimensions including data assimilation. The approach is based on the incompressible Navier–Stokes equations and the nonlinear viscosity is considered by means of the Carreau–Yasuda viscosity model, which can account for shear-thickening and shear-thinning behavior of generalized Newtonian fluids. We outline the procedure how to integrate given data into the numerical solution of flow problems without additional computational cost using the least-squares FEM. Assimilation of experimental data provides the opportunity to reduce model errors resulting in a solution which more closely approximates reality. Furthermore, the preprocessing of the available data using Kriging interpolation is also described briefly. The presented formulation is first validated by investigating the flow in a cube with an exact solution without data assimilation. Convergence is evaluated based on the error in velocities and pressure compared to the exact solution. Then the effect of data assimilation is shown by modeling blood flow through a carotid bifurcation model and integrating data either along lines or over entire cross-sectional areas. The improvement of the numerical solution by means of data assimilation is revealed by comparing the calculated velocity profiles with experimental and numerical reference values. © 2022
    view abstractdoi: 10.1016/j.cma.2022.114668
  • 2022 • 1340 Effect of microstructural heterogeneity on fatigue strength predicted by reinforcement machine learning
    Awd, M. and Münstermann, S. and Walther, F.
    Fatigue and Fracture of Engineering Materials and Structures 45 3267-3287 (2022)
    The posterior statistical distributions of fatigue strength are determined using Bayesian inferential statistics and the Metropolis Monte Carlo method. This study explores how structural heterogeneity affects ultrahigh cycle fatigue strength in additive manufacturing. Monte Carlo methods and procedures may assist estimate fatigue strength posteriors and scatter. The acceptable probability in Metropolis Monte Carlo relies on the Markov chain's random microstructure state. In addition to commonly studied variables, the proportion of chemical composition was demonstrated to substantially impact fatigue strength if fatigue lifetime in crack propagation did not prevail due to high threshold internal notches. The study utilizes an algorithm typically used for quantum mechanics to solve the complicated multifactorial fatigue problem. The inputs and outputs are modified by fitting the microstructural heterogeneities into the Metropolis Monte Carlo algorithm. The main advantage here is applying a general-purpose nonphenomenological model that can be applied to multiple influencing factors without high numerical penalty. © 2022 The Authors. Fatigue & Fracture of Engineering Materials & Structures published by John Wiley & Sons Ltd.
    view abstractdoi: 10.1111/ffe.13816
  • 2022 • 1339 Mechanism of coupled phase/morphology transformation of 2D manganese oxides through Fe galvanic exchange reaction
    Aymerich-Armengol, R. and Cignoni, P. and Ebbinghaus, P. and Linnemann, J. and Rabe, M. and Tschulik, K. and Scheu, C. and Lim, J.
    Journal of Materials Chemistry A 10 24190-24198 (2022)
    doi: 10.1039/d2ta06552e
  • 2022 • 1338 Cross-relaxation interactions in ZnO:Mn2+: The ground state optical pumping
    Azamat, D.V. and Badalyan, A.G. and Romanov, N.G. and Hrabovsky, M. and Jastrabik, L. and Dejneka, A. and Yakovlev, D.R. and Bayer, M.
    Applied Physics Letters 120 (2022)
    A steady-state population inversion in the ground state of Mn2+ in ZnO was detected by application of continuous microwave and circularly polarized optical pumping in the temperature range of 3-6 K. Multiple spin-flip processes occur in view of a simultaneous saturation in the harmonically related transitions of Mn2+ spins. It is found that an additional relaxation channel arises at 2.7 K due to dynamic polarization of the 55Mn nuclei through the saturation of the first order electron-nuclear forbidden transitions. The transient populations are created between 55Mn nuclear sublevels. © 2022 Author(s).
    view abstractdoi: 10.1063/5.0078442
  • 2022 • 1337 Unexpectedly High Capacitance of the Metal Nanoparticle/Water Interface: Molecular-Level Insights into the Electrical Double Layer
    Azimzadeh Sani, M. and Pavlopoulos, N.G. and Pezzotti, S. and Serva, A. and Cignoni, P. and Linnemann, J. and Salanne, M. and Gaigeot, M.-P. and Tschulik, K.
    Angewandte Chemie - International Edition 61 (2022)
    The electrical double-layer plays a key role in important interfacial electrochemical processes from catalysis to energy storage and corrosion. Therefore, understanding its structure is crucial for the progress of sustainable technologies. We extract new physico-chemical information on the capacitance and structure of the electrical double-layer of platinum and gold nanoparticles at the molecular level, employing single nanoparticle electrochemistry. The charge storage ability of the solid/liquid interface is larger by one order-of-magnitude than predicted by the traditional mean-field models of the double-layer such as the Gouy–Chapman–Stern model. Performing molecular dynamics simulations, we investigate the possible relationship between the measured high capacitance and adsorption strength of the water adlayer formed at the metal surface. These insights may launch the active tuning of solid–solvent and solvent–solvent interactions as an innovative design strategy to transform energy technologies towards superior performance and sustainability. © 2021 The Authors. Angewandte Chemie International Edition published by Wiley-VCH GmbH
    view abstractdoi: 10.1002/anie.202112679
  • 2022 • 1336 Design Principles for Industrial Data-Driven Services
    Azkan, C. and Moller, F. and Iggena, L. and Otto, B.
    IEEE Transactions on Engineering Management 1-24 (2022)
    The continuously growing availability and volume of data pressure companies to leverage them economically. Subsequently, companies must find strategies to incorporate data sensibly for internal optimization and find new business opportunities in data-driven business models. In this article, we focus on using data and data analytics in product-oriented industrial companies. Although data-driven services are becoming increasingly important, little is known about their systematic design and development in research. Surprisingly, many companies face significant challenges and fail to create these services successfully. Against this background, this article presents findings from a multicase based on qualitative interviews and workshops with experts from different industrial sectors. We propose ten design principles and corresponding design features to successfully design industrial data-driven services in this context. These design principles help practitioners and researchers to understand the peculiarities of creating data-driven services more in-depth on a conceptual, technical, and organizational level. Author
    view abstractdoi: 10.1109/TEM.2022.3167737
  • 2022 • 1335 Microstructure analysis of single-lip deep hole drilled bores by electron backscatter diffraction and magnetic Barkhausen noise
    Baak, N. and Nickel, J. and Biermann, D. and Walther, F.
    Procedia CIRP 108 740-745 (2022)
    doi: 10.1016/j.procir.2022.03.114
  • 2022 • 1334 Full wafer property control of local droplet etched GaAs quantum dots
    Babin, H.-G. and Bart, N. and Schmidt, M. and Spitzer, N. and Wieck, A.D. and Ludwig, Ar.
    Journal of Crystal Growth 591 (2022)
    We present strategies for controlling growth parameters of local droplet etched GaAs quantum dots. We manage the local QD density and emission wavelength by gradient material deposition. We find regions with no light-emitting quantum dots sharply separated from regions with strong quantum dot luminescence. Close to this transition, we expect the lowest quantum dot densities possible under the used parameters. The maximum wavelength shift achieved due to a variation of GaAs hole filling level on a single 3-inch wafer ranges from 731 to 795 nm. By locally controlling the surface roughness, a profound additional influence on the emission wavelength and density is found. We show how to control this modulation on a millimeter-scale over the whole wafer. © 2022 Elsevier B.V.
    view abstractdoi: 10.1016/j.jcrysgro.2022.126713
  • 2022 • 1333 Efficient reconstruction of prior austenite grains in steel from etched light optical micrographs using deep learning and annotations from correlative microscopy
    Bachmann, B.-I. and Müller, M. and Britz, D. and Durmaz, A.R. and Ackermann, M. and Shchyglo, O. and Staudt, T. and Mücklich, F.
    Frontiers in Materials 9 (2022)
    The high-temperature austenite phase is the initial state of practically all technologically relevant hot forming and heat treatment operations in steel processing. The phenomena occurring in austenite, such as recrystallization or grain growth, can have a decisive influence on the subsequent properties of the material. After the hot forming or heat treatment process, however, the austenite transforms into other microstructural constituents and information on the prior austenite morphology are no longer directly accessible. There are established methods available for reconstructing former austenite grain boundaries via metallographic etching or electron backscatter diffraction (EBSD) which both exhibit shortcomings. While etching is often difficult to reproduce and strongly depend on the investigated steel’s alloying concept, EBSD acquisition and reconstruction is rather time-consuming. But in fact, though, light optical micrographs of steels contrasted with conventional Nital etchant also contain information about the former austenite grains. However, relevant features are not directly apparent or accessible with conventional segmentation approaches. This work presents a deep learning (DL) segmentation of prior austenite grains (PAG) from Nital etched light optical micrographs. The basis for successful segmentation is a correlative characterization from EBSD, light and scanning electron microscopy to specify the ground truth required for supervised learning. The DL model shows good and robust segmentation results. While the intersection over union of 70% does not fully reflect the model performance due to the inherent uncertainty in PAG estimation, a mean error of 6.1% in mean grain size derived from the segmentation clearly shows the high quality of the result. Copyright © 2022 Bachmann, Müller, Britz, Durmaz, Ackermann, Shchyglo, Staudt and Mücklich.
    view abstractdoi: 10.3389/fmats.2022.1033505
  • 2022 • 1332 Solvent effect investigation on the acid-catalyzed esterification of levulinic acid by ethanol aided by a Linear Solvation Energy Relationship
    Baco, S. and Klinksiek, M. and Ismail Bedawi Zakaria, R. and Antonia Garcia-Hernandez, E. and Mignot, M. and Legros, J. and Held, C. and Casson Moreno, V. and Leveneur, S.
    Chemical Engineering Science 260 (2022)
    doi: 10.1016/j.ces.2022.117928
  • 2022 • 1331 Scalable, inexpensive, one-pot, facile synthesis of crystalline two-dimensional birnessite flakes
    Badr, H.O. and Montazeri, K. and El-Melegy, T. and Natu, V. and Carey, M. and Gawas, R. and Phan, P. and Qian, Q. and Li, C.Y. and Wiedwald, U. and Farle, M. and Colin-Ulloa, E. and Titova, L.V. and Currie, M. and Ouisse, T. and B...
    Matter 5 2365-2381 (2022)
    doi: 10.1016/j.matt.2022.05.038
  • 2022 • 1330 ANALYSIS AND ASYMPTOTIC REDUCTION OF A BULK-SURFACE REACTION-DIFFUSION MODEL OF GIERER-MEINHARDT TYPE
    Bäcker, J.-P. and Röger, M.
    Communications on Pure and Applied Analysis 21 1139-1155 (2022)
    We consider a Gierer-Meinhardt system on a surface coupled with a parabolic PDE in the bulk, the domain confined by this surface. Such a model was recently proposed and analyzed for two-dimensional bulk domains by Gomez, Ward and Wei (SIAM J. Appl. Dyn. Syst. 18, 2019). We prove the well-posedness of the bulk-surface system in arbitrary space dimensions and show that solutions remain uniformly bounded in parabolic Hölder spaces for all times. The cytosolic diffusion is typically much larger than the lateral diffusion on the membrane. This motivates to a corresponding asymptotic reduction, which consists of a nonlocal system on the membrane. We prove the convergence of solutions of the full system towards unique solutions of the reduction. © 2022 American Institute of Mathematical Sciences. All rights reserved.
    view abstractdoi: 10.3934/cpaa.2022013
  • 2022 • 1329 Cup positioning and its effect on polyethylene wear of vitamin E- and non-vitamin E-supplemented liners in total hip arthroplasty: radiographic outcome at 5-year follow-up
    Baghdadi, J. and Alkhateeb, S. and Roth, A. and Jäger, M. and Busch, A. and Alkhateeb, S. and Landgraeber, S. and Serong, S. and Haversath, M. and vonWasen, A. and Windhagen, H. and Flörkemeier, T. and Budde, S. and Kubilay, J. ...
    Archives of Orthopaedic and Trauma Surgery (2022)
    doi: 10.1007/s00402-022-04424-2
  • 2022 • 1328 Chemo-mechanical phase-field modeling of iron oxide reduction with hydrogen
    Bai, Y. and Mianroodi, J.R. and Ma, Y. and da Silva, A.K. and Svendsen, B. and Raabe, D.
    Acta Materialia 231 (2022)
    The reduction of iron ore with carbon-carriers is one of the largest sources of greenhouse gas emissions in the industry, motivating global activities to replace the coke-based blast furnace reduction by hydrogen-based direct reduction (HyDR). Iron oxide reduction with hydrogen has been widely investigated both experimentally and theoretically. The HyDR process includes multiple types of chemical reactions, solid state and defect-mediated diffusion (of oxygen and hydrogen species), several phase transformations, as well as massive volume shrinkage and mechanical stress buildup. However, studies focusing on the chemo-mechanical interplay during the reduction reaction influenced by microstructure are sparse. In this work, a chemo-mechanically coupled phase-field (PF) model has been developed to explore the interplay between phase transformation, chemical reaction, species diffusion, large elasto-plastic deformation and microstructure evolution. Energetic constitutive relations of the model are based on the system free energy which is calibrated with the help of a thermodynamic database. The model has been first applied to the classical core-shell (wüstite-iron) structure. Simulations show that the phase transformation from wüstite to α-iron can result in high stresses and rapidly decelerating reaction kinetics. Mechanical stresses create elastic energy in the system, an effect which can negatively influence the phase transformations, thus causing slow reaction kinetics and low metallization. However, if the elastic stress becomes comparatively high, it can shift the shape of the free energy from a double-well to a single-well case, speed up the transformation and result in a higher reduction degree compared to the low-stress double-well case. The model has been applied to simulate an experimentally characterized iron oxide specimen with its complex microstructure. The observed microstructure evolution during reduction is well predicted by the model. The simulation results also show that isolated pores in the microstructure are filled with water vapor during reduction, which can influence the local reaction atmosphere and dynamics. © 2022
    view abstractdoi: 10.1016/j.actamat.2022.117899
  • 2022 • 1327 Lagrangian filtered density function modeling of a turbulent stratified flame combined with flamelet approach
    Baik, S.-J. and Inanc, E. and Rieth, M. and Kempf, A.M.
    Physics of Fluids 34 (2022)
    To simulate turbulent flames with high accuracy at low computational cost, Rieth et al. ["A hybrid flamelet finite-rate chemistry approach for efficient LES with a transported FDF,"Combust. Flame 199, 183-193 (2019)] have developed a hybrid method combining a combustion sub-grid model with assumed filtered density function (FDF) with a transported FDF approach. The present paper extends the hybrid approach to a stratified flame from the Cambridge stratified flame series. In contrast to the conventional Lagrangian FDF transport approach, the hybrid model applies Lagrangian particles to solve FDF transport only in selected regions, while an assumed FDF is applied in the remaining domain. With the hybrid model, the overall number of particles is strongly reduced compared to the conventional Lagrangian FDF transport model, promising great savings in computational cost. To provide a basis for the comparisons, simulations with assumed FDF or transported FDF only have also been performed. The present work aims to show the advantage of the Lagrangian transported FDF and the hybrid approach for a highly stratified flame, one of the most challenging members of the well-known Cambridge stratified flame series. Different criteria are tested for triggering the switch-over between the methods to maximize the efficiency of the hybrid approach, where basic flame quantities such as mixture fraction were predicted well with the assumed FDF model, and the temperature and mass fraction of carbon monoxide were predicted better by the hybrid method, featuring the transported FDF technique. © 2022 Author(s).
    view abstractdoi: 10.1063/5.0093942
  • 2022 • 1326 Oxidation kinetics of atmospheric plasma sprayed environmental barrier coatings
    Bakan, E. and Vaßen, R.
    Journal of the European Ceramic Society 42 5122-5128 (2022)
    Three different Si/Yb-silicate environmental barrier coating systems (EBCs) were atmospheric plasma sprayed using various spray currents (275, 325, 375 A) for Yb-silicate deposition. The EBCs were thermally cycled between room temperature and 1300 °C up to 1000 h in air. Additionally, bare Si coatings were tested under isothermal and thermal cycling conditions in the as-sprayed state and after polishing at 1300 °C in air. Parabolic oxidation kinetics were observed and oxidation protection provided by Yb-silicate was found to be influenced by the spray conditions, i.e. only at 325 A, Yb-silicate was effectively protecting the bond coat. The controlling mechanism was attributed to densification in the Yb-silicate layer during thermal cycling, which was quantified via image analysis. The surface finish of the Si coating was also found to be influencing the oxidation rate. The TGO was thinner and less cracked on polished APS Si coating in comparison with the as-sprayed Si coating surface. © 2022 Elsevier Ltd
    view abstractdoi: 10.1016/j.jeurceramsoc.2022.05.003
  • 2022 • 1325 A review of the metastable omega phase in beta titanium alloys: the phase transformation mechanisms and its effect on mechanical properties
    Ballor, J. and Li, T. and Prima, F. and Boehlert, C.J. and Devaraj, A.
    International Materials Reviews (2022)
    Since its discovery in 1954, the omega (ω) phase in titanium and its alloys has attracted substantial attention from researchers. The β-to-ω and ω-to-α phase transformations are central to β-titanium alloy design, but the transformation mechanisms have been a subject of debate. With new generations of aberration-corrected transmission electron microscopy and atom probe tomography, both the spatial resolution and compositional sensitivity of phase transformation analysis have been rapidly improving. This review provides a detailed assessment of the new understanding gained and related debates in this field enabled by advanced characterization methods. Specifically, new insights into the possibility of a coupled diffusional-displacive component in the β-to-ω transformation and key nucleation driving forces for the ω-assisted α phase formation are discussed. Additionally, the influence of ω phase on the mechanical properties of β-titanium alloys is also reviewed. Finally, a perspective on open questions and future direction for research is discussed. © This material is authored by Battelle Memorial Institute with the US Department of Energy under Contract No. DE-AC05-76RL01830. The US Government retains for itself, and others acting on its behalf, a paid-up, non-exclusive, and irrevocable worldwide license in said article to reproduce, prepare derivative works, distribute copies to the public, and perform publicly and display publicly, by or on behalf of the Government.
    view abstractdoi: 10.1080/09506608.2022.2036401
  • 2022 • 1324 Automated and manual classification of metallic nanoparticles with respect to size and shape by analysis of scanning electron micrographs [Automatisierte und manuelle Klassifizierung metallischer Nanopartikel nach Größe und Form aus rasterelektronenmikroskopischen Aufnahmen]
    Bals, J. and Loza, K. and Epple, P. and Kircher, T. and Epple, M.
    Materialwissenschaft und Werkstofftechnik 53 270-283 (2022)
    Automated image analysis has been applied to scanning electron micrographs (transmission mode; STEM) of metallic nanoparticles (silver and gold; about 10 nm to 20 nm). For a reliable particle identification, scanning electron microscopic images must be recorded with distinct contrast and resolution parameters. The particles were separated from the background and classified according to shape and size by machine learning (machine learning). Training images were created with model particles cut out of real electron microscopic images. The automated analysis of the particle size (expressed as area) was well possible, but overlapping particles could not be safely separated. The assignment of particle to six different shape classes (sphere, triangle, square, pentagon, hexagon, rod) by automated analysis was difficult. The fact that real particles never have an ideal geometrical shape but are always distorted or have rough edges or cropped tips is the fundamental reason of this problem. This effect also occurred with human image evaluators and poses a considerable obstacle in the training process for machine learning. Image analysis by machine learning techniques is difficult if different human evaluators disagree on the shape assignment of given particles because a proper training cannot be provided. © 2022 The Authors. Materialwissenschaft und Werkstofftechnik published by Wiley-VCH GmbH.
    view abstractdoi: 10.1002/mawe.202100285
  • 2022 • 1323 Unravelling Composition–Activity–Stability Trends in High Entropy Alloy Electrocatalysts by Using a Data-Guided Combinatorial Synthesis Strategy and Computational Modeling
    Banko, L. and Krysiak, O.A. and Pedersen, J.K. and Xiao, B. and Savan, A. and Löffler, T. and Baha, S. and Rossmeisl, J. and Schuhmann, W. and Ludwig, Al.
    Advanced Energy Materials 12 (2022)
    High entropy alloys (HEA) comprise a huge search space for new electrocatalysts. Next to element combinations, the optimization of the chemical composition is essential for tuning HEA to specific catalytic processes. Simulations of electrocatalytic activity can guide experimental efforts. Yet, the currently available underlying model assumptions do not necessarily align with experimental evidence. To study deviations of theoretical models and experimental data requires statistically relevant datasets. Here, a combinatorial strategy for acquiring large experimental datasets of multi-dimensional composition spaces is presented. Ru–Rh–Pd–Ir–Pt is studied as an exemplary, highly relevant HEA system. Systematic comparison with computed electrochemical activity enables the study of deviations from theoretical model assumptions for compositionally complex solid solutions in the experiment. The results suggest that the experimentally obtained distribution of surface atoms deviates from the ideal distribution of atoms in the model. Leveraging both advanced simulation and large experimental data enables the estimation of electrocatalytic activity and solid-solution stability trends in the 5D composition space of the HEA system. A perspective on future directions for the development of active and stable HEA catalysts is outlined. © 2022 The Authors. Advanced Energy Materials published by Wiley-VCH GmbH
    view abstractdoi: 10.1002/aenm.202103312
  • 2022 • 1322 Conservation of Nickel Ion Single-Active Site Character in a Bottom-Up Constructed π-Conjugated Molecular Network
    Baranowski, D. and Cojocariu, I. and Sala, A. and Africh, C. and Comelli, G. and Schio, L. and Tormen, M. and Floreano, L. and Feyer, V. and Schneider, C.M.
    Angewandte Chemie - International Edition 61 (2022)
    On-surface chemistry holds the potential for ultimate miniaturization of functional devices. Porphyrins are promising building-blocks in exploring advanced nanoarchitecture concepts. More stable molecular materials of practical interest with improved charge transfer properties can be achieved by covalently interconnecting molecular units. On-surface synthesis allows to construct extended covalent nanostructures at interfaces not conventionally available. Here, we address the synthesis and properties of covalent molecular network composed of interconnected constituents derived from halogenated nickel tetraphenylporphyrin on Au(111). We report that the π-extended two-dimensional material exhibits dispersive electronic features. Concomitantly, the functional Ni cores retain the same single-active site character of their single-molecule counterparts. This opens new pathways when exploiting the high robustness of transition metal cores provided by bottom-up constructed covalent nanomeshes. © 2022 The Authors. Angewandte Chemie International Edition published by Wiley-VCH GmbH.
    view abstractdoi: 10.1002/anie.202210326
  • 2022 • 1321 Temperature Dependent Dielectric Characterization With Partially Loaded Waveguides
    Barengolts, I. and Schenkel, F. and Schulz, C. and Barowski, J. and Rolfes, I.
    2022 German Microwave Conference, GeMiC 2022 228-231 (2022)
    In this paper, a method for the characterization of the dielectric parameters as a function of temperature is presented. The effects of temperature on the polarizability of the materials are measured. To obtain accurate results, the effects of the heating process investigated on the measurement system must be taken into account and be corrected. Correction methods based on the adjustment of the calibration plane or the adaptation of the propagation constant are shown. The impact of the thermal expansion is investigated and the robust functionality of the implemented algorithm is verified in a test setup. The test setup is based on waveguides that enable nearly perfect boundary conditions and a simple correction of different thermal influences. Measurements are carried out in a frequency range from 8.4 GHz to 12.5 GHz with PTFE as the material under test (MUT) in a temperature range from 24°C to 106°C. This frequency range corresponds to the X-band and allows an easy realization of the measurement system. © 2022 IMA.
    view abstract
  • 2022 • 1320 Comparison of Radar-based Distance Measurements in Overmoded Waveguides Using TE11- and TE01-Mode
    Barengolts, I. and Schulz, C. and Rolfes, I.
    Asia-Pacific Microwave Conference Proceedings, APMC 2022-November 949-951 (2022)
  • 2022 • 1319 Wafer-scale epitaxial modulation of quantum dot density
    Bart, N. and Dangel, C. and Zajac, P. and Spitzer, N. and Ritzmann, J. and Schmidt, M. and Babin, H.G. and Schott, R. and Valentin, S.R. and Scholz, S. and Wang, Y. and Uppu, R. and Najer, D. and Löbl, M.C. and Tomm, N. and Javad...
    Nature Communications 13 (2022)
    Precise control of the properties of semiconductor quantum dots (QDs) is vital for creating novel devices for quantum photonics and advanced opto-electronics. Suitable low QD-densities for single QD devices and experiments are challenging to control during epitaxy and are typically found only in limited regions of the wafer. Here, we demonstrate how conventional molecular beam epitaxy (MBE) can be used to modulate the density of optically active QDs in one- and two- dimensional patterns, while still retaining excellent quality. We find that material thickness gradients during layer-by-layer growth result in surface roughness modulations across the whole wafer. Growth on such templates strongly influences the QD nucleation probability. We obtain density modulations between 1 and 10 QDs/µm2 and periods ranging from several millimeters down to at least a few hundred microns. This method is universal and expected to be applicable to a wide variety of different semiconductor material systems. We apply the method to enable growth of ultra-low noise QDs across an entire 3-inch semiconductor wafer. © 2022, The Author(s).
    view abstractdoi: 10.1038/s41467-022-29116-8
  • 2022 • 1318 On embedding a traditional mechanical engineering course in a constructivist learning environment
    Bartel, T.
    2022 IEEE German Education Conference, GeCon 2022 (2022)
    doi: 10.1109/GeCon55699.2022.9942745
  • 2022 • 1317 Object Recognition in High-Resolution Indoor THz SAR Mapped Environment
    Batra, A. and Sheikh, F. and Khaliel, M. and Wiemeler, M. and Gohringer, D. and Kaiser, T.
    Sensors 22 (2022)
    doi: 10.3390/s22103762
  • 2022 • 1316 Fusion of Optical and Millimeter Wave SAR Sensing for Object Recognition in Indoor Environment
    Batra, A. and Hark, T. and Schorlemer, J. and Pohl, N. and Rolfes, I. and Wiemeler, M. and Gohringer, D. and Kaiser, T. and Barowski, J.
    2022 5th International Workshop on Mobile Terahertz Systems, IWMTS 2022 (2022)
    doi: 10.1109/IWMTS54901.2022.9832438
  • 2022 • 1315 Investigation of THz SAR Through-Wall Sensing in Indoor Environment
    Batra, A. and Sheikh, F. and Wiemeler, M. and Gohringer, D. and Kaiser, T.
    AMTA 2022 - Proceedings: 2022 Antenna Measurement Techniques Association Symposium (2022)
    doi: 10.23919/AMTA55213.2022.9954947
  • 2022 • 1314 Geometrical Shapes Detection in High-Resolution THz SAR Image
    Batra, A. and Wiemeler, M. and Gohringer, D. and Kaiser, T.
    2022 19th European Radar Conference, EuRAD 2022 213-216 (2022)
    doi: 10.23919/EuRAD54643.2022.9924669
  • 2022 • 1313 Conductivity enhancement of Al- and Ta-substituted Li7La3Zr2O7 solid electrolytes by nanoparticles
    Bauer, A. and Ali, M.Y. and Orthner, H. and Uhlenbruck, S. and Wiggers, H. and Fattakhova-Rohlfing, D. and Guillon, O.
    Journal of the European Ceramic Society 42 1033-1041 (2022)
    A nanopowder consisting of La2Zr2O7 particles with lithium containing species on their surface was prepared by spray flame synthesis and subsequently added to Li7La3Zr2O12 powder obtained by a conventional solid-state reaction. The spray flame synthesis method utilized in this work yields nanoparticles with a small size of approximately 5 nm, which is unprecedented within the scope of oxide-based ionic conductors for solid-state batteries. Remarkably, the addition of nanoparticles for sintering at a relatively low temperature of 1000 °C significantly improved the ionic conductivity by 50 %. In contrast, there was no influence of incorporating nanoparticles on the conductivity at sintering temperatures at or above 1100 °C, which is the typical temperature range applied for conventional sintering of Li7La3Zr2O12. Compared to prior published work with analogous materials, a more than twofold improvement in conductivity was demonstrated while the sintering temperature was decreased by 100 °C. © 2021 Elsevier Ltd
    view abstractdoi: 10.1016/j.jeurceramsoc.2021.11.029
  • 2022 • 1312 Geometry modifications of single-lip drills to improve cutting fluid flow
    Baumann, A. and Oezkaya, E. and Biermann, D. and Eberhard, P.
    International Journal of Advanced Manufacturing Technology 121 1689-1695 (2022)
    doi: 10.1007/s00170-022-09400-z
  • 2022 • 1311 Linear shrinkage of hydrogel coatings exposed to flow: Interplay between dissolution of water and advective transport
    Baumli, P. and Hauer, L. and Lorusso, E. and Aghili, A.S. and Hegner, K.I. and D'Acunzi, M. and Gutmann, J.S. and Dünweg, B. and Vollmer, D.
    Soft Matter 18 365-371 (2022)
    doi: 10.1039/d1sm01297e
  • 2022 • 1310 Bioelectrocatalytic CO2Reduction by Redox Polymer-Wired Carbon Monoxide Dehydrogenase Gas Diffusion Electrodes
    Becker, J.M. and Lielpetere, A. and Szczesny, J. and Junqueira, J.R.C. and Rodríguez-Maciá, P. and Birrell, J.A. and Conzuelo, F. and Schuhmann, W.
    ACS Applied Materials and Interfaces 14 46421-46426 (2022)
    The development of electrodes for efficient CO2reduction while forming valuable compounds is critical. The use of enzymes as catalysts provides the advantage of high catalytic activity in combination with highly selective transformations. We describe the electrical wiring of a carbon monoxide dehydrogenase II from Carboxydothermus hydrogenoformans (ChCODH II) using a cobaltocene-based low-potential redox polymer for the selective reduction of CO2to CO over gas diffusion electrodes. High catalytic current densities of up to -5.5 mA cm-2are achieved, exceeding the performance of previously reported bioelectrodes for CO2reduction based on either carbon monoxide dehydrogenases or formate dehydrogenases. The proposed bioelectrode reveals considerable stability with a half-life of more than 20 h of continuous operation. Product quantification using gas chromatography confirmed the selective transformation of CO2into CO without any parasitic co-reactions at the applied potentials. © 2022 American Chemical Society. All rights reserved.
    view abstractdoi: 10.1021/acsami.2c09547
  • 2022 • 1309 Assembling a Low-volume Biofuel Cell on a Screen-printed Electrode for Glucose Sensing
    Becker, J.M. and Lielpetere, A. and Szczesny, J. and Ruff, A. and Conzuelo, F. and Schuhmann, W.
    Electroanalysis 34 1629-1637 (2022)
    An enzymatic biofuel cell is integrated on a screen-printed electrode as a basis for a self-powered biosensor. A glucose/O2 biofuel cell consisting of a pyrroloquinoline quinone-dependent glucose dehydrogenase embedded within an Os-complex modified redox polymer bioanode to oxidize glucose and a non-limiting bilirubin oxidase-based gas diffusion biocathode in the direct-electron transfer regime for the reduction of O2 showed a glucose-dependent current and power output. For full integration on a single screen-printed electrode, a miniaturized agar salt bridge was introduced between the two bioelectrodes to ensure operation of the assembly in a two-compartment configuration with each electrode operating at optimal conditions. © 2022 The Authors. Electroanalysis published by Wiley-VCH GmbH.
    view abstractdoi: 10.1002/elan.202200084
  • 2022 • 1308 Validation of the Powder Metallurgical Processing of Duplex Stainless Steels through Hot Isostatic Pressing with Integrated Heat Treatment
    Becker, L. and Lentz, J. and Kramer, B. and Rottstegge, A. and Broeckmann, C. and Theisen, W. and Weber, S.
    Materials 15 (2022)
    Duplex stainless steels exhibit an excellent combination of corrosion resistance and strength and are increasingly being manufactured through powder metallurgy (PM) to produce large, near-net-shaped components, such as those used for offshore applications. Hot isostatic pressing (HIP) is often used for PM production, in which pre-alloyed powders are compacted under high pressures and temperatures. Recent developments in HIP technology enable fast cooling as part of the process cycle, reaching cooling rates comparable to oil quenching or even faster. This enables the integrated solution annealing of duplex stainless steels directly after compaction. In contrast to the conventional HIP route, which requires another separate solution annealing step after compaction, the integrated heat treatment within the HIP process saves both energy and time. Due to this potential gain, HIP compaction at a high pressure of 170 MPa and 1150 °C with integrated solution annealing for the production of duplex stainless steels was investigated in this work. Firstly, the focus was to investigate the influence of pressure on the phase stability during the integrated solution annealing of the steel X2CrNiMoN22-5-3. Secondly, the steel X2CrNiMoCuWN25-7-4, which is highly susceptible to sigma phase embrittlement, was used to investigate whether the cooling rates used in the HIP are sufficient for preventing the formation of this brittle microstructural constituent. This work shows that the high pressure used during the solution heat treatment stabilizes the austenite. In addition, it was verified that the cooling rates during quenching stage in HIP are sufficient for preventing the formation of the sigma phase in the X2CrNiMoCuWN25-7-4 duplex stainless steel. © 2022 by the authors.
    view abstractdoi: 10.3390/ma15186224
  • 2022 • 1307 Quantification of extremely small-structured ferritic-austenitic phase fractions in stainless steels manufactured by laser powder bed fusion
    Becker, L. and Boes, J. and Lentz, J. and Cui, C. and Uhlenwinkel, V. and Steinbacher, M. and Fechte-Heinen, R. and Theisen, W. and Weber, S.
    Materialia 22 (2022)
    This work investigated processing of stainless steel powders and powder mixtures using powder bed fusion - laser beam/metal (PBF-LB/M), which produced different ferritic and austenitic phase fractions in the as-built state. The rapid cooling and solidification rates in the PBF-LB/M process led to the formation of an extremely small-structured microstructure in which the austenitic phase was found on the grain boundaries and as acicular Widmanstätten austenite (width < 1 µm) within the primary δ-ferritic solidified matrix. This work shows that the time-saving quantification of the ferritic and austenitic phase fractions of these particular microstructures is nontrivial. Common time-efficient phase quantification methods such as image analysis of etched cross-sections or magneto-inductive methods (Feritscope®) have proven to be inaccurate. On the other hand, electron backscattered diffraction (EBSD) investigations proved to be extremely time-consuming in order to resolve the small microstructural constituents sufficiently well and to obtain a reliably large sample section. The highest accuracy was achieved with X-ray diffraction. Two different methods were considered: the Debye-Scherrer method, which was characterized by short measuring times, and the Bragg-Brentano method (quantification using Rietveld refinement), which showed the highest accuracy for the entire range of ferritic-austenitic phase fractions. © 2022 Acta Materialia Inc.
    view abstractdoi: 10.1016/j.mtla.2022.101393
  • 2022 • 1306 Role of Surface Adsorbates on the Photoresponse of (MO)CVD-Grown Graphene-MoS2Heterostructure Photodetectors
    Beckmann, Y. and Grundmann, A. and Daniel, L. and Abdelbaky, M. and McAleese, C. and Wang, X. and Conran, B. and Pasko, S. and Krotkus, S. and Heuken, M. and Kalisch, H. and Vescan, A. and Mertin, W. and Kümmell, T. and Bacher, G.
    ACS Applied Materials and Interfaces 14 35184-35193 (2022)
    doi: 10.1021/acsami.2c06047
  • 2022 • 1305 Nudging to Improve Human-AI Symbiosis
    Becks, E. and Weis, T.
    2022 IEEE International Conference on Pervasive Computing and Communications Workshops and other Affiliated Events, PerCom Workshops 2022 132-133 (2022)
    The goal of human-AI symbiosis is a mutual benefit for humans and AI. The challenges of gaining a human-AI symbiosis are manyfold. One challenge is what is communicated to humans and when. Too frequent inquiries by an AI will cause the human to feel distracted, which can lead to negative experiences. However, if the AI takes over some or all of the task solving for humans, there is a risk that humans will become dependent on the technology and loose skills. The right type of communication between humans and AI is important. The goal of our PHD research is to develop a method to optimize human-AI symbiosis through appropriate interaction and explainability. Our approach is to use AI to encourage humans through nudging to discover solution strategies on their own. In this way, the cognitive performance of a human is aimed to be preserved as much as possible. This could also counteract common problems in modern AI systems such as parameter drift. Therefore, we will study the effect of nudging in human-AI interactions and gain insights into what would happen if the machine nudges a human in the wrong direction. For this purpose, a user study will be conducted in which the human interaction with an AI is simulated. Afterwards an AI will be developed that uses nudging mechanisms that reliably nudge the user towards the correct solution without losing the human's own cognitive effort. The AI should support humans unobtrusively and thus be integrated into daily working life. © 2022 IEEE.
    view abstractdoi: 10.1109/PerComWorkshops53856.2022.9767539
  • 2022 • 1304 Ferromagnetic Europium Sulfide Thin Films: Influence of Precursors on Magneto-Optical Properties
    Beer, S.M.J. and Muriqi, A. and Lindner, P. and Winter, M. and Rogalla, D. and Nolan, M. and Ney, A. and Debus, J. and Devi, A.
    Chemistry of Materials 34 152-164 (2022)
    Europium sulfide (EuS) thin films are appealing as ferromagnetic semiconductors and luminescent and optomagnetic materials owing to their unique functional properties. With the emerging field of spintronics and magneto-optical devices, chemical vapor deposition (CVD) offers a versatile platform to tune the material properties and the method to fabricate device structures needed for such applications. Herein, we report the growth of high-quality cubic EuS via a versatile CVD process where the new Eu(III) precursors employed facilitate the formation of the target EuS layers under moderated process conditions. Based on the prior evaluation of the physicochemical properties of these precursors using thermal analysis and density functional theory studies, adequate volatility, thermal stability, and sufficient reactivity toward potential co-reactants, namely, elemental sulfur, could be inferred. Thus, the use of toxic hydrogen sulfide generally needed for sulfide film depositions could be avoided, which is a significant advantage in terms of simplifying the deposition process. The as-deposited thin films were analyzed in terms of the structure, composition, and morphology, revealing highly oriented polycrystalline and stoichiometric EuS films. UV/vis measurements yielded a band gap of around 1.6 eV, and Raman spectroscopy exhibited a coupling between the phonons and electron spin systems of EuS. These findings, together with the soft ferromagnetic character of the films derived from semiconducting quantum interference device measurements, signify the potential of CVD-grown EuS for future technological applications. © 2021 American Chemical Society.
    view abstractdoi: 10.1021/acs.chemmater.1c02958
  • 2022 • 1303 FEM SIMULATIONS FOR THIXO-VISCOPLASTIC FLOW PROBLEMS; WELLPOSEDNESS RESULTS
    Begum, N. and Ouazzi, A. and Turek, S.
    World Congress in Computational Mechanics and ECCOMAS Congress (2022)
    doi: 10.23967/eccomas.2022.119
  • 2022 • 1302 Fabrication and characterization of inner selective antibiofouling forward osmosis hollow fiber membranes for simultaneous wastewater treatment and desalination
    Behboudi, A. and Mohammadi, T. and Ulbricht, M.
    Separation and Purification Technology 300 (2022)
    Forward osmosis (FO) hollow-fiber membranes were prepared by in situ thin layer assembly of polyethyleneimine (PEI) on antifouling PES-based porous nanocomposite membranes during membrane formation by spinning and phase inversion, via incorporation of surface-modified silver nanoparticles (NPs) in the dope solution and addition of PEI in the bore liquid; after cross-linking with glutaraldehyde the FO selective layer was obtained at the lumen surface while the shell surface had ultrafilter (UF) properties. This design enabled the utilization of the FO membranes in active layer facing draw solution (DS) orientation to employ maximum effective osmotic pressure, while the UF layer in combination with the antibacterial NPs was supposed to reduce fouling by the wastewater used as feed solution (FS). The quality of the active layer assembly was characterized using atomic force microscopy and scanning electron microscopy analyses, as well as salt rejection, structural parameter (S), and molecular weight cut-off (MWCO) measurements. The separation performance of these membranes was evaluated in an osmotic membrane bioreactor (OMBR) system, showing for the best FO nanocomposite membranes less than 10% fouling and flux reduction over 5 cycles of operation over a total period of 5 days. The best-suited membrane showed promising separation performance in the OMBR system by providing 43.4 LMH water flux and only around 0.2 g/l specific reverse salt flux (SRSF) with 1 M NaCl and DI water serving as DS and feed, respectively. This study focused also on distinctive performance criteria in combined FO and OMBR systems, such as the membrane's potential in a pretreatment step of brine streams (used as DS) to provide proper feed composition for RO units and introduced a new specific performance index (SPI) for better characterization of FO membranes which summarizes all essential characteristics of the membrane application, instead of using existing structural parameter equations for membrane characterization. The best-suited FO membrane offered an SPI of 778.2 gl−1 m−2 h−1, meaning 778.2 g/l reduction of TDS in DS per unit membrane surface area per hour. © 2022 Elsevier B.V.
    view abstractdoi: 10.1016/j.seppur.2022.121795
  • 2022 • 1301 Layer thickness controlling in Direct Energy Deposition process by adjusting the powder flow rate
    Behlau, F. and Thiele, M. and Maack, P. and Esen, C. and Ostendorf, A.
    Procedia CIRP 111 330-334 (2022)
    doi: 10.1016/j.procir.2022.08.033
  • 2022 • 1300 The radiosensitizing effect of platinum nanoparticles in proton irradiations is not caused by an enhanced proton energy deposition at the macroscopic scale
    Behrends, C. and Bäcker, C.M. and Schilling, I. and Zwiehoff, S. and Weingarten, J. and Kröninger, K. and Rehbock, C. and Barcikowski, S. and Wulff, J. and Bäumer, C. and Timmermann, B.
    Physics in Medicine and Biology 67 (2022)
    doi: 10.1088/1361-6560/ac80e6
  • 2022 • 1299 Effects of Silica Modification (Mg, Al, Ca, Ti, and Zr) on Supported Cobalt Catalysts for H2-Dependent CO2Reduction to Metabolic Intermediates
    Belthle, K.S. and Beyazay, T. and Ochoa-Hernández, C. and Miyazaki, R. and Foppa, L. and Martin, W.F. and Tuÿsüz, H.
    Journal of the American Chemical Society 144 21232-21243 (2022)
    doi: 10.1021/jacs.2c08845
  • 2022 • 1298 Ultrastrong Poly(2-Oxazoline)/Poly(Acrylic Acid) Double-Network Hydrogels with Cartilage-Like Mechanical Properties
    Benitez-Duif, P.A. and Breisch, M. and Kurka, D. and Edel, K. and Gökcay, S. and Stangier, D. and Tillmann, W. and Hijazi, M. and Tiller, J.C.
    Advanced Functional Materials 32 (2022)
    The exceptional stiffness and toughness of double-network hydrogels (DNHs) offer the possibility to mimic even complex biomaterials, such as cartilage. The latter has a limited regenerative capacity and thus needs to be substituted with an artificial material. DNHs composed of cross-linked poly(2-oxazoline)s (POx) and poly(acrylic acid) (PAA) are synthesized by free radical polymerization in a two-step process. The resulting DNHs are stabilized by hydrogen bridges even at pH 7.4 (physiological PBS buffer) due to the pKa-shifting effect of POx on PAA. DNHs based on poly(2-methyl-2-oxazoline), which have a water content (WC) of around 66 wt% and are not cytotoxic, show biomechanical properties that match those of cartilage in terms of WC, stiffness, toughness, coefficient of friction, compression in body relevant stress conditions and viscoelastic behavior. This material also has high strength in PBS pH 7.4 and in egg white as synovial liquid substitute. In particular, a compression strength of up to 60 MPa makes this material superior. © 2022 The Authors. Advanced Functional Materials published by Wiley-VCH GmbH.
    view abstractdoi: 10.1002/adfm.202204837
  • 2022 • 1297 Surface Diffusion Aided by a Chirality Change of Self-Assembled Oligomers under 2D Confinement
    Bera, A. and Henkel, S. and Mieres-Perez, J. and Andargie Tsegaw, Y. and Sanchez-Garcia, E. and Sander, W. and Morgenstern, K.
    Angewandte Chemie - International Edition 61 (2022)
    Chirality switching of self-assembled molecular structures is of potential interest for designing functional materials but is restricted by the strong interaction between the embedded molecules. Here, we report on an unusual approach based on reversible chirality changes of self-assembled oligomers using variable-temperature scanning tunneling microscopy supported by quantum mechanical calculations. Six functionalized diazomethanes each self-assemble into chiral wheel-shaped oligomers on Ag(111). At 130 K, a temperature far lower than expected, the oligomers change their chirality even though the molecules reside in an embedded self-assembled structure. Each chirality change is accompanied by a slight center-of-mass shift. We show how the identical activation energies of the two processes result from the interplay of the chirality change with surface diffusion, findings that open the possibility of implementing various functional materials from self-assembled supramolecular structures. © 2022 The Authors. Angewandte Chemie International Edition published by Wiley-VCH GmbH.
    view abstractdoi: 10.1002/anie.202212245
  • 2022 • 1296 In Situ Growth and Bias-Dependent Modification of NaBr Ionic Layers on Ag(111)
    Bera, A. and Morgenstern, K.
    Journal of Physical Chemistry C 126 10610-10617 (2022)
    Although the formation of insulating ionic layers on metal surfaces has been well studied, their growth mechanisms are still controversial. Here, we report several innovative approaches to trigger in situ growth to understand this growth mechanism. The modification of the layer and its in situ growth is followed by time-lapsed scanning tunneling microscopy at room temperature with atomic resolution. The NaBr molecules form bilayer and trilayer islands when deposited at room temperature. These stable layers begin to disintegrate when the voltage exceeds the threshold voltage during scanning. The molecules released from the modified layer subsequently attach to the preexisting layer in a predefined scan region. Scanning of two neighboring trilayer islands traps the mobile molecule between them, leading to their coalescence. Time-lapsed measurements offer a step-by-step realization of the in situ controlled growth of an ionic layer at the atomic scale. © 2022 American Chemical Society.
    view abstractdoi: 10.1021/acs.jpcc.2c03582
  • 2022 • 1295 Avoiding process vibrations by suppressing chip segmentation during machining of aerospace alloy Ti6Al4V
    Berger, S. and Brock, G. and Saelzer, J. and Biermann, D.
    Procedia CIRP 115 89-94 (2022)
    doi: 10.1016/j.procir.2022.10.055
  • 2022 • 1294 Impact of Thermophysical Properties of High-Alloy Tool Steels on Their Performance in Re-Purposing Applications
    Berger, A. and Benito, S. and Kronenberg, P. and Weber, S.
    Materials 15 (2022)
    doi: 10.3390/ma15238702
  • 2022 • 1293 A methodology to integrate process-induced subsurface characteristics into a digital twin-based framework for the evaluation of machining processes
    Bergmann, J.A. and Wöste, F. and Wiederkehr, P.
    Procedia CIRP 107 125-130 (2022)
    The consideration of process-induced subsurface characteristics as an essential quality parameter of manufactured components is of primary relevance. An established means for the prediction of these characteristics such as residual stress, hardness or phase transformations is the use of finite element analysis, which can be used to model changes in the material for defined process configurations and engagement scenarios. However, due to high simulation times and in many cases limited model sizes, only selected scenarios can be evaluated. Process simulation systems which model the cutting process using empirical models and geometric representations of the tool and workpiece to predict the process forces and, e. g., deflections, offer the possibility to simulate entire machining processes efficiently. In this contribution, a methodology is presented to integrate process-induced alterations of the subsurface during milling into the workpiece model of a process simulation system. For the evaluation of these alterations, finite element analyses can be used for representative engagement and process scenarios, which have to be selected a priori based on each process. By extending the digital-twin of the workpiece with this information, the influence of complex machining operations with time-variant engagement conditions can be evaluated continuously. As a result, the presented framework thus provides a basis for predicting the resulting quality of the manufactured component with respect to subsurface characteristics. © 2022 The Authors. Published by Elsevier B.V.
    view abstractdoi: 10.1016/j.procir.2022.04.021
  • 2022 • 1292 Integration of Hot Isostatic Pressing and Heat Treatment for Advanced Modified γ-TiAl TNM Alloys
    Bernal, D. and Chamorro, X. and Hurtado, I. and Lopez-Galilea, I. and Bürger, D. and Weber, S. and Madariaga, I.
    Materials 15 (2022)
    The conventional processing route of TNM (Ti-Nb-Mo) alloys combines casting and Hot Isostatic Pressing (HIP) followed by forging and multiple heat treatments to establish optimum properties. This is a time-consuming and costly process. In this study we present an advanced alternative TNM alloy processing route combining HIP and heat treatments into a single process, which we refer to as IHT (integrated HIP heat treatment), applied to a modified TNM alloy with 1.5B. A Quintus HIP lab unit with a quenching module was used, achieving fast and controlled cooling, which differs from the slow cooling rates of conventional HIP units. A Ti-42.5Al-3.5Nb-1Mo-1.5B (at.%) was subjected to an integrated two HIP steps at 200 MPa, one at 1250◦ C for 3 h and another at 1260◦ C for 1 h, both under a protective Ar atmosphere and followed by cooling at 30 K/min down to room temperature. The results were compared against the Ti-43.5Al-3.5Nb-1Mo-0.8B (at.%) thermomechanically processed in a conventional way. Applying IHT processing to the 1.5B alloy does indeed achieve good creep strength, and the secondary creep rate of the IHT processed materials is similar to that of conventionally forged TNM alloys. Thus, the proposed advanced IHT processing route could manufacture more cost-effective TiAl components. © 2022 by the authors. Licensee MDPI, Basel, Switzerland.
    view abstractdoi: 10.3390/ma15124211
  • 2022 • 1291 Nucleation and growth studies of large-area deposited WS2 on flexible substrates
    Berning, T. and Becher, M. and Wree, J.-L. and Jagosz, J. and Kostka, A. and Ostendorf, A. and Devi, A. and Bock, C.
    Materials Research Express 9 (2022)
    doi: 10.1088/2053-1591/ac9bd0
  • 2022 • 1290 Interplay of Halogen and Weak Hydrogen Bonds in the Formation of Magic Nanoclusters on Surfaces
    Bertram, C. and Miller, D.P. and Schunke, C. and Kemeny, I. and Kimura, M. and Bovensiepen, U. and Zurek, E. and Morgenstern, K.
    Journal of Physical Chemistry C 126 588-596 (2022)
    Halogen bonding has recently been recognized as an interaction whose relevance is on par with hydrogen bonding. While observed frequently in solution chemistry, the significance of halogen bonds in forming extended supramolecular structures on surfaces is less explored. Herein, we report on the self-assembly of chlorobenzene molecules adsorbed on the Cu(111) surface into nanosized clusters at submonolayer coverages, where the molecular planes are close to parallel to the surface. A comprehensive study of the role of intermolecular interactions through both halogen and weak hydrogen bonds on nanocluster formation is presented, gained by combining the results of temperature-programmed desorption, reflection-absorption infrared spectroscopy, scanning tunneling microscopy, and density functional theory calculations. Based on an unprecedented precise determination of the molecules’ orientation within the clusters, the binding motifs that lead to the formation and stability of nanoclusters with magic sizes are identified and explained. A complex and delicate interplay of halogen bonds with weak hydrogen bonds, van-der-Waals forces, and surface–adsorbate interactions leads to a preference for hexamers and tetramers with an observable propensity for halogen bonding over weak hydrogen bonding when adsorbed to the Cu(111) surface. © 2021 American Chemical Society
    view abstractdoi: 10.1021/acs.jpcc.1c08045
  • 2022 • 1289 Stress Equilibration for Hyperelastic Models
    Bertrand, F. and Moldenhauer, M. and Starke, G.
    Lecture Notes in Applied and Computational Mechanics 98 91-105 (2022)
    Stress equilibration is investigated for hyperelastic deformation models in this contribution. From the displacement-pressure approximation computed with a stable finite element pair, an H(div ) -conforming approximation to the first Piola-Kirchhoff stress tensor is computed. This is done in the usual way in a vertex-patch-wise manner involving local problems of small dimension. The corresponding reconstructed Cauchy stress is not symmetric but its skew-symmetric part is controlled by the computed correction. This difference between the reconstructed stress and the stress approximation obtained directly from the Galerkin approximation also serves as an upper bound for the discretization error. These properties are illustrated by computational experiments for an incompressible rigid block loaded on one half of its top boundary. © 2022, The Author(s), under exclusive license to Springer Nature Switzerland AG.
    view abstractdoi: 10.1007/978-3-030-92672-4_4
  • 2022 • 1288 Quantification of the Influence of ConcreteWidth per Fiber Strand on the Splitting Crack Failure of Textile Reinforced Concrete (TRC)
    Beßling, M. and Orlowsky, J.
    Polymers 14 (2022)
    The composite material textile reinforced concrete (TRC) requires a high bond performance between the fiber strand and the concrete matrix. While the influence of the textile on bond behavior is well known, in this publication the influence of the concrete matrix is investigated by means of single-sided pull-out tests. The results of the presented study show dependence between the concrete strength and bond performance of the composite material. When a concrete of a higher-strength class is used, the bond-flow–pull-out distance curve shifts upward independent of the textile geometry and the yarn impregnation. A simplified model is presented to predict the occurrence of a crack along the fiber strand. This model serves as a basis to investigate the correlation between concrete width per fiber strand and resistance against a splitting crack. The effective concrete tensile strength decreases to about 35% when the concrete width is increased from 10 mm to 50 mm. To quantify the decrease, a mathematical relationship, which describes the test results independent of textile and concrete type, is proposed. © 2022 by the authors.
    view abstractdoi: 10.3390/polym14030489
  • 2022 • 1287 Repair and Protection of Existing Steel-Reinforced Concrete Structures with High-Strength, Textile-Reinforced Mortars
    Beßling, M. and Groh, M. and Koch, V. and Auras, M. and Orlowsky, J. and Middendorf, B.
    Buildings 12 (2022)
    Numerous concrete monuments built in the High Modern Era (turn of the 20th century until the 1970s) must now be repaired for preservation. Traditional concrete repair according to current guidelines involves considerable material removal, changing the appearance of the existing structure. With a combination of the material properties of high-/ultra-high-performance concrete (HPC/UHPC) with its dense microstructure and corrosion-free textile reinforcement (carbon and basalt), a high-performance mortar repair system can be developed. Such a system allows for concrete repairs with minimal material loss by using very thin layers that are durable and do not change the architectural character of the repaired monument. For the investigation of the load-bearing behaviour of a structural repair system using textile-reinforced, high-performance mortar, 20 mm thick slabs were produced and mechanically characterized. In the next step, the proposed repair system was applied to 70 mm thick old concrete slabs. The results show that a high surface tensile strength of 2.9 MPa was obtained. In a further step, the system will be applied to concrete pillars of transmission tower in Berus, adapted in terms of colour and structure and installed for long-term monitoring. © 2022 by the authors.
    view abstractdoi: 10.3390/buildings12101615
  • 2022 • 1286 Quantification of the Transversal Fiber Strand Stiffness of Textiles Used in Textile-Reinforced Concrete via Shore Hardness
    Beßling, M. and Manko, L. and Orlowsky, J.
    Buildings 12 (2022)
    doi: 10.3390/buildings12112038
  • 2022 • 1285 Layer-Specific Damage Modeling of Porcine Large Intestine under Biaxial Tension
    Bhattarai, A. and May, C.A. and Staat, M. and Kowalczyk, W. and Tran, T.N.
    Bioengineering 9 (2022)
    The mechanical behavior of the large intestine beyond the ultimate stress has never been investigated. Stretching beyond the ultimate stress may drastically impair the tissue microstructure, which consequently weakens its healthy state functions of absorption, temporary storage, and transportation for defecation. Due to closely similar microstructure and function with humans, biaxial tensile experiments on the porcine large intestine have been performed in this study. In this paper, we report hyperelastic characterization of the large intestine based on experiments in 102 specimens. We also report the theoretical analysis of the experimental results, including an exponential damage evolution function. The fracture energies and the threshold stresses are set as damage material parameters for the longitudinal muscular, the circumferential muscular and the submucosal collagenous layers. A biaxial tensile simulation of a linear brick element has been performed to validate the applicability of the estimated material parameters. The model successfully simulates the biomechanical response of the large intestine under physiological and non-physiological loads. © 2022 by the authors.
    view abstractdoi: 10.3390/bioengineering9100528
  • 2022 • 1284 Automatic welding robot offline programming with adaptive automation level
    Bickendorf, J.
    54th International Symposium on Robotics, ISR Europe 2022 34-41 (2022)
  • 2022 • 1283 A combustion chemistry study of tetramethylethylene in a laminar premixed low-pressure hydrogen flame
    Bierkandt, T. and Hemberger, P. and Obwald, P. and Gaiser, N. and Hoener, M. and Krüger, D. and Kasper, T. and Köhler, M.
    Proceedings of the Combustion Institute (2022)
    The combustion chemistry of tetramethylethylene (TME) was studied in a premixed laminar low-pressure hydrogen flame by combined photoionization molecular-beam mass spectrometry (PI-MBMS) and photoelectron photoion coincidence (PEPICO) spectroscopy at the Swiss Light Source (SLS) of the Paul Scherrer Institute in Villigen, Switzerland. This hexene isomer with the chemical formula C6H12 has a special structure with only allylic CH bonds. Several combustion intermediate species were identified by their photoionization and threshold photoelectron spectra, respectively. The experimental mole fraction profiles were compared to modeling results from a recently published kinetic reaction mechanism that includes a TME sub-mechanism to describe the TME/H2 flame structure. The first stable intermediate species formed early in the flame front during the combustion of TME are 2-methyl-2-butene (C5H10) at a mass-to-charge ratio (m/z) of 70, 2,3-dimethylbutane (C6H14) at m/z 86, and 3-methyl-1,2-butadiene (C5H8) at m/z 68. Isobutene (C4H8) is also a dominant intermediate in the combustion of TME and results from consumption of 2-methyl-2-butene. In addition to these hydrocarbons, some oxygenated species are formed due to low-temperature combustion chemistry in the consumption pathway of TME under the investigated flame conditions. © 2022 Elsevier Ltd. All rights reserved.
    view abstractdoi: 10.1016/j.proci.2022.07.205
  • 2022 • 1282 Similarity of competing risks models with constant intensities in an application to clinical healthcare pathways involving prostate cancer surgery
    Binder, N. and Möllenhoff, K. and Sigle, A. and Dette, H.
    Statistics in Medicine 41 3804-3819 (2022)
    doi: 10.1002/sim.9481
  • 2022 • 1281 Data Mining in Urology: Understanding Real-world Treatment Pathways for Lower Urinary Tract Systems via Exploration of Big Data
    Binder, N. and Dette, H. and Franz, J. and Zöller, D. and Suarez-Ibarrola, R. and Gratzke, C. and Binder, H. and Miernik, A.
    European Urology Focus 8 391-393 (2022)
    doi: 10.1016/j.euf.2022.03.019
  • 2022 • 1280 Magnetostatic simulations with consideration of exterior domains using the scaled boundary finite element method
    Birk, C. and Reichel, M. and Schröder, J.
    Computer Methods in Applied Mechanics and Engineering 399 (2022)
    doi: 10.1016/j.cma.2022.115362
  • 2022 • 1279 Dislocation-enhanced electrical conductivity in rutile TiO2 accessed by room-temperature nanoindentation
    Bishara, H. and Tsybenko, H. and Nandy, S. and Muhammad, Q.K. and Frömling, T. and Fang, X. and Best, J.P. and Dehm, G.
    Scripta Materialia 212 (2022)
    Dislocation-enhanced electrical conductivity is an emerging topic for ceramic oxides. In contrast to the majority of present studies which focus on large-scale crystal deformation or thin film fabrication to introduce dislocations, we use a nanoindentation “pop-in stop” method to locally generate 〈011〉 edge-type dislocations at room temperature, without crack formation, on the (100) surface of a rutile TiO2 single-crystal. Ion beam assisted deposition of microcontacts allowed for both deformed and non-deformed zones to be locally probed by impedance spectroscopy. Compared to the dislocation-free region, a local enhancement of the electrical conductivity by 50% in the dislocation-rich regions is found. The study paves the way for local “mechanical-doping” of ceramics and oxide materials, allowing for the use of dislocations to tune the local conductivity with high spatial resolution. © 2022 The Author(s)
    view abstractdoi: 10.1016/j.scriptamat.2022.114543
  • 2022 • 1278 Effect of hybridization in PdAlY-(Ni/Au/Ir) metallic glasses thin films on electrical resistivity
    Bishara, H. and Kontis, P. and Dehm, G. and Schneider, J.M. and Evertz, S.
    Scripta Materialia 214 (2022)
    doi: 10.1016/j.scriptamat.2022.114681
  • 2022 • 1277 Concomitant appearance of conductivity and superconductivity in (111) LaAlO3/SrTiO3 interface with metal capping
    Bisht, R.S. and Mograbi, M. and Rout, P.K. and Tuvia, G. and Dagan, Y. and Yoon, H. and Swartz, A.G. and Hwang, H.Y. and Li, L.L. and Pentcheva, R.
    Physical Review Materials 6 (2022)
    In epitaxial polar-oxide interfaces, conductivity sets in beyond a finite number of monolayers (ML). This threshold for conductivity is explained by accumulating sufficient electric potential to initiate charge transfer to the interface. Here we experimentally and theoretically study the LaAlO3/SrTiO3 (111) interface where a critical thickness tc of nine epitaxial LaAlO3 ML is required to turn the interface from insulating to conducting and even superconducting. We show that tc decreases to 3 ML when depositing a cobalt overlayer (capping) and 6 ML for platinum capping. The latter result contrasts with the (001) interface, where platinum capping increases tc beyond the bare interface. Our density functional theory calculations with a Hubbard U term confirm the observed threshold for conductivity for the bare and the metal-capped interfaces. Interestingly, conductivity appears concomitantly with superconductivity for metal/LaAlO3/SrTiO3 (111) interfaces, in contrast with the metal/LaAlO3/SrTiO3 (001) interfaces where conductivity appears without superconductivity. We attribute this dissimilarity to the different orbital polarization of eg′ for the (111) versus dxy for the (001) interface. © 2022 American Physical Society.
    view abstractdoi: 10.1103/PhysRevMaterials.6.044802
  • 2022 • 1276 Hydrogen Diffusion in Clinopyroxene at Low Temperatures (195°C–400°C) and Consequences for Subsurface Processes
    Bissbort, T. and Lynn, K.J. and Becker, H.-W. and Chakraborty, S.
    Geochemistry, Geophysics, Geosystems 23 (2022)
    doi: 10.1029/2022GC010520
  • 2022 • 1275 A hybrid approach for the efficient computation of polycrystalline yield loci with the accuracy of the crystal plasticity finite element method
    Biswas, A. and Kalidindi, S.R. and Hartmaier, A.
    Modelling and Simulation in Materials Science and Engineering 30 (2022)
    Direct experimental evaluation of the anisotropic yield locus (YL) of a given material, representing the zeros of the material's yield function in the stress space, is arduous. It is much more practical to determine the YL by combining limited measurements of yield strengths with predictions from numerical models based on microstructural features such as the orientation distribution function (ODF; also referred to as the crystallographic texture). For the latter, several different strategies exist in the current literature. In this work, we develop and present a new hybrid method that combines the numerical efficiency and simplicity of the classical crystallographic yield locus (CYL) method with the accuracy of the computationally expensive crystal plasticity finite element method (CPFEM). The development of our hybrid approach is presented in two steps. In the first step, we demonstrate for diverse crystallographic textures that the proposed hybrid method is in good agreement with the shape of the predicted YL estimated by either CPFEM or experiments, even for pronounced plastic anisotropy. It is shown that the calibration of only two parameters of the CYL method with only two yield stresses for different load cases obtained from either CPFEM simulations or experiments produces a reliable computation of the polycrystal YL for diverse crystallographic textures. The accuracy of the hybrid approach is evaluated using the results from the previously established CPFEM method for the computation of the entire YL and also experiments. In the second step, the point cloud data of stress tensors on the YL predicted by the calibrated CYL method are interpolated within the deviatoric stress space by cubic splines such that a smooth yield function can be constructed. Since the produced YL from the hybrid approach is presented as a smooth function, this formulation can potentially be used as an anisotropic yield function for the standard continuum plasticity methods commonly used in finite element analysis. © 2022 The Author(s). Published by IOP Publishing Ltd.
    view abstractdoi: 10.1088/1361-651X/ac4a24
  • 2022 • 1274 Manipulation of Liquid Crystalline Properties by Dynamic Covalent Chemistry-En Route to Adaptive Materials
    Blanke, M. and Postulka, L. and Ciara, I. and D'Acierno, F. and Hildebrandt, M. and Gutmann, J.S. and Dong, R.Y. and Michal, C.A. and Giese, M.
    ACS Applied Materials and Interfaces 14 16755-16763 (2022)
    doi: 10.1021/acsami.2c03241
  • 2022 • 1273 Tuning the Fluorescence in Dynamic Covalent Bonded Liquid Crystals
    Blanke, M. and Neumann, T. and Gutierrez Suburu, M.E. and Prymak, O. and Wölper, C. and Strassert, C.A. and Giese, M.
    ACS Applied Materials and Interfaces 14 55864-55872 (2022)
    doi: 10.1021/acsami.2c16209
  • 2022 • 1272 Charge dynamics in magnetically disordered Mott insulators
    Bleicker, P. and Hering, D.-B. and Uhrig, G.S.
    Physical Review B 105 (2022)
    With the aid of both a semianalytical and a numerically exact method, we investigate the charge dynamics in the vicinity of half-filling in the one- and two-dimensional t-J model derived from a Fermi-Hubbard model in the limit of large interaction U and hence small exchange coupling J. The spin degrees of freedom are taken to be disordered. So we consider the limit 0<J«T«W, where W is the bandwidth. We focus on evaluating the local spectral density of a single hole excitation and the charge gap that separates the upper and the lower Hubbard band. We find indications that no band edges exist if the magnetic exchange is taken into account; instead of band edges, Gaussian tails seem to appear. A discussion of the underlying physics is provided. © 2022 American Physical Society.
    view abstractdoi: 10.1103/PhysRevB.105.085121
  • 2022 • 1271 Simple shear in nonlinear Cosserat micropolar elasticity: Existence of minimizers, numerical simulations, and occurrence of microstructure
    Blesgen, T. and Neff, P.
    Mathematics and Mechanics of Solids (2022)
    Deformation microstructure is studied for a 1D-shear problem in geometrically nonlinear Cosserat elasticity. Microstructure solutions are described analytically and numerically for zero characteristic length scale. © The Author(s) 2022.
    view abstractdoi: 10.1177/10812865221122191
  • 2022 • 1270 Biodegradable open-porous scaffolds made of sintered magnesium W4 and WZ21 short fibres show biocompatibility in vitro and in long-term in vivo evaluation
    Bobe, K. and Willbold, E. and Haupt, M. and Reebmann, M. and Morgenthal, I. and Andersen, O. and Studnitzky, T. and Nellesen, J. and Tillmann, W. and Vogt, C. and Vano-Herrera, K. and Witte, F.
    Acta Biomaterialia 148 389-404 (2022)
    Open-porous scaffolds made of W4 and WZ21 fibres were evaluated to analyse their potential as an implant material. WZ21 scaffolds without any surface modification or coating, showed promising mechanical properties which were comparable to the W4 scaffolds tested in previous studies. Eudiometric testing results were dependent on the experimental setup, with corrosion rates differing by a factor of 3. Cytotoxicity testing of WZ21 showed sufficient cytocompatibility. The corrosion behavior of the WZ21 scaffolds in different cell culture media are indicating a selective dealloying of elements from the magnesium scaffold by different solutions. Long term in-vivo studies were using 24 W4 scaffolds and 12 WZ21 scaffolds, both implanted in rabbit femoral condyles. The condyles and important inner organs were explanted after 6, 12 and 24 weeks and analyzed. The in-vivo corrosion rate of the WZ21 scaffolds calculated by microCT-based volume loss was up to 49 times slower than the in-vitro corrosion rate based on weight loss. Intramembranous bone formation within the scaffolds of both alloys was revealed, however a low corrosion rate and formation of gas cavities at initial time points were also detected. No systemic or local toxicity could be observed. Investigations by μ-XRF did not reveal accumulation of yttrium in the neighboring tissue. In summary, the magnesium scaffold´s performance is biocompatible, but would benefit from a surface modification, such as a coating to obtain lower the initial corrosion rates, and hereby establish a promising open-porous implant material for load-bearing applications. Statement of significance: Magnesium is an ideal temporary implant material for non-load bearing applications like bigger bone defects, since it degrades in the body over time. Here we developed and tested in vitro and in a rabbit model in vivo degradable open porous scaffolds made of sintered magnesium W4 and WZ21 short fibres. These scaffolds allow the ingrowth of cells and blood vessels to promote bone healing and regeneration. Both fibre types showed in vitro sufficient cytocompatibility and proliferation rates and in vivo, no systemic toxicity could be detected. At the implantation site, intramembranous bone formation accompanied by ingrowth of supplying blood vessels within the scaffolds of both alloys could be detected. © 2022 Acta Materialia Inc.
    view abstractdoi: 10.1016/j.actbio.2022.06.005
  • 2022 • 1269 Efficient parametrization of the atomic cluster expansion
    Bochkarev, Anton and Lysogorskiy, Yury and Menon, Sarath and Qamar, Minaam and Mrovec, Matous and Drautz, Ralf
    Physical Review Materials 6 (2022)
    The atomic cluster expansion (ACE) provides a general, local, and complete representation of atomic energies. Here we present an efficient framework for parametrization of ACE models for elements, alloys, and molecules. To this end, we first introduce general requirements for a physically meaningful description of the atomic interaction, in addition to the usual equivariance requirements. We then demonstrate that ACE can be converged systematically with respect to two fundamental characteristics—the number and complexity of basis functions and the choice of nonlinear representation. The construction of ACE parametrizations is illustrated for several representative examples with different bond chemistries, including metallic copper, covalent carbon, and several multicomponent molecular and alloy systems. We discuss the Pareto front of optimal force to energy matching contributions in the loss function, the influence of regularization, the importance of consistent and reliable reference data, and the necessity of unbiased validation. Our ACE parametrization strategy is implemented in the freely available software package pacemaker that enables largely automated and GPU accelerated training. The resulting ACE models are shown to be superior or comparable to the best currently available ML potentials and can be readily used in large-scale atomistic simulations. ©2022 American Physical Society
    view abstractdoi: 10.1103/PhysRevMaterials.6.013804
  • 2022 • 1268 Multilayer atomic cluster expansion for semilocal interactions
    Bochkarev, A. and Lysogorskiy, Y. and Ortner, C. and Csányi, G. and Drautz, R.
    Physical Review Research 4 (2022)
    doi: 10.1103/PhysRevResearch.4.L042019
  • 2022 • 1267 Bone tunnel placement influences shear stresses at the coracoid process after coracoclavicular ligament reconstruction: a finite element study and radiological analysis
    Bockmann, B. and Dankl, L. and Kucinskaite, G. and Kumar, A. and Timothy, J.J. and Meschke, G. and Venjakob, A.J. and Schulte, T.L.
    Archives of Orthopaedic and Trauma Surgery (2022)
    Introduction: Coracoid fractures after arthroscopic treatment of acromioclavicular (AC) joint separations lead to poor clinical outcomes. In this study, different configurations of bone tunnels in the lateral clavicle and coracoid were examined concerning the amount of stress induced in the coracoid. Methods: An authentic 3D finite element model of an ac joint was established. Three 2.4 mm bone tunnels were inserted in the lateral clavicle, which were situated above, medially and laterally of the coracoid. Then, two 2.4 mm bone tunnels were inserted in the latter, each simulating a proximal and a distal suture button position. Von Mises stress analyses were performed to evaluate the amount of stress caused in the coracoid process by the different configurations. Then, a clinical series of radiographs was examined, the placement of the clavicle drill hole was analyzed and the number of dangerous configurations was recorded. Results: The safest configuration was a proximal tunnel in the coracoid combined with a lateral bone tunnel in the clavicle, leading to an oblique traction at the coracoid. A distal bone tunnel in the coracoid and perpendicular traction as well as a proximal tunnel in the coracoid with medial traction caused the highest stresses. Anatomical placement of the clavicle drill hole does lead to configurations with smaller stresses. Conclusion: The bone tunnel placement with the smallest amount of shear stresses was found when the traction of the suture button was directed slightly lateral, towards the AC joint. Anatomical placement of the clavicle drill hole alone was not sufficient in preventing dangerous configurations. Level of evidence: Controlled laboratory study. © 2022, The Author(s).
    view abstractdoi: 10.1007/s00402-022-04382-9
  • 2022 • 1266 A scalable twin surface dielectric barrier discharge system for pollution remediation at high gas flow rates
    Böddecker, A. and Bodnar, A. and Schücke, L. and Giesekus, J. and Wenselau, K. and Nguyen-Smith, R.T. and Oppotsch, T. and Oberste-Beulmann, C. and Muhler, M. and Gibson, A.R. and Awakowicz, P.
    Reaction Chemistry and Engineering (2022)
    In this work, a modular, multi-electrode surface dielectric barrier discharge system for the decomposition of polluted air streams at high volumetric flows, necessary for industrial applications, is designed and constructed. The system is demonstrated for the decomposition of butoxyethanol and n-butane in ambient air flows of up to almost 500 slm (standard litres per minute) (≙ 30 m3 h−1) at concentrations between 50 ppm and 1000 ppm. With an energy density of (78.3 ± 3.6) J L−1 a maximum relative conversion of about 27% of butoxyethanol is achieved. n-Butane was used to enable comparison with previous studies. Here it could be demonstrated that the scaled-up source achieved higher conversion at lower energy densities in comparison to the original design used at lower volumetric flow rates. Additionally, the density of ozone, which is a toxic by-product of the overall process, was measured in the exhaust gas under different operating conditions and its degradation with activated carbon filters was studied. At an energy density of 79.6 J L−1 a maximum ozone molecule flow of (9.02 ± 0.19) × 1018 s−1 was measured which decreases with increasing energy density, because among other possible effects the rising temperature accelerates its decay. One of the activated carbon filters was able to reduce the concentration of toxic ozone by 100% under conditions where a preheated airstream is used. © 2022 The Royal Society of Chemistry.
    view abstractdoi: 10.1039/d2re00167e
  • 2022 • 1265 ELECTRODEPOSITION OF A Ni-Mo ALLOY CATALYST WITH OPTIMIZED Mo-CONTENT FOR HYDROGEN EVOLUTION REACTION IN AEM-ELECTROLYSIS
    Böhm, L. and Thielker, K. and Kazamer, N. and Wirkert, F. and Rost, U. and Marginean, G. and Apfel, U.-P. and Brodmann, M.
    Proceedings of WHEC 2022 - 23rd World Hydrogen Energy Conference: Bridging Continents by H2 207-209 (2022)
  • 2022 • 1264 Nematicity and nematic fluctuations in iron-based superconductors
    Böhmer, A.E. and Chu, J.-H. and Lederer, S. and Yi, M.
    Nature Physics 18 1412-1419 (2022)
    doi: 10.1038/s41567-022-01833-3
  • 2022 • 1263 Open Wilson chain numerical renormalization group approach to Green's functions
    Böker, J. and Anders, F.B.
    Physical Review B 105 (2022)
    doi: 10.1103/PhysRevB.105.235127
  • 2022 • 1262 Microstructure and Properties of a Novel Carbon-Martensitic Hot Work Tool Steel Processed by Laser Additive Manufacturing without Preheating
    Boes, J. and Röttger, A. and Mutke, C. and Escher, C. and Weber, S.
    Steel Research International (2022)
    Laser additive manufacturing (LAM) techniques, such as laser-powder bed fusion (L-PBF) or laser-directed energy deposition (L-DED), allow for the production of complex-shaped parts by either the local melting of a metallic powder bed by a laser beam (L-PBF) or a local application and laser beam melting of powder material by a nozzle (L-DED). In the case of carbon-martensitic tool steels, their cold crack susceptibility limits their LAM processability and is usually counteracted by substrate preheating. As preheating can increase the oxygen take-up of the powder and alter the part microstructure, it can be disadvantageous for part quality and powder reusability. In this study, it is investigated a carbon-martensitic steel designed for the production of parts with low crack density by LAM without preheating, focusing on the microstructure and hardness of the L-PBF- and L-DED-manufactured steel. The steel can be LAM-processed without preheating, resulting in specimens with low crack densities and martensitic microstructure with retained austenite. The hardness of the as-built material (L-PBF: 542HV30 and L-DED: 623HV30) is increased by quenching and tempering up to 693HV30. Direct tempering of the as-built specimen without previous quenching leads to a shift of the secondary hardness maximum from 500 to 530 °C. © 2022 The Authors. Steel Research International published by Wiley-VCH GmbH.
    view abstractdoi: 10.1002/srin.202200439
  • 2022 • 1261 Feedback of Non-Local dxy Nematicity on the Magnetic Anisotropy in FeSe
    Bötzel, S. and Eremin, I.M.
    Frontiers in Physics 10 (2022)
    doi: 10.3389/fphy.2022.919784
  • 2022 • 1260 Thickness-dependent slow light gap solitons in three-dimensional coupled photonic crystal waveguides
    Bohley, C. and Jandieri, V. and Schwager, B. and Khomeriki, R. and Schulz, D. and Erni, D. and Werner, D.H. and Berakdar, J.
    Optics Letters 47 2794-2797 (2022)
    doi: 10.1364/OL.457044
  • 2022 • 1259 Retrodirective Rectenna Arrays for passive SHF-RFID Transponders
    Boller, S. and Grenter, T. and Hennig, A. and Grabmaier, A.
    PRIME 2022 - 17th International Conference on Ph.D Research in Microelectronics and Electronics, Proceedings 165-168 (2022)
    doi: 10.1109/PRIME55000.2022.9816744
  • 2022 • 1258 Quantum Dot Molecule Devices with Optical Control of Charge Status and Electronic Control of Coupling
    Bopp, F. and Rojas, J. and Revenga, N. and Riedl, H. and Sbresny, F. and Boos, K. and Simmet, T. and Ahmadi, A. and Gershoni, D. and Kasprzak, J. and Ludwig, Ar. and Reitzenstein, S. and Wieck, A. and Reuter, D. and Müller, K. an...
    Advanced Quantum Technologies 5 (2022)
    Tunnel-coupled pairs of optically active quantum dots—quantum dot molecules (QDMs)—offer the possibility to combine excellent optical properties such as strong light-matter coupling with two-spin singlet–triplet ((Formula presented.)) qubits having extended coherence times. The (Formula presented.) basis formed using two spins is inherently protected against electric and magnetic field noise. However, since a single gate voltage is typically used to stabilize the charge occupancy of the dots and control the inter-dot orbital couplings, operation of the (Formula presented.) qubits under optimal conditions remains challenging. Here, an electric field tunable QDM that can be optically charged with one (1h) or two holes (2h) on demand is presented. A four-phase optical and electric field control sequence facilitates the sequential preparation of the 2h charge state and subsequently allows flexible control of the inter-dot coupling. Charges are loaded via optical pumping and electron tunnel ionization. One- and two-hole charging efficiencies of (93.5 ± 0.8)% and (80.5 ± 1.3)% are achieved, respectively. Combining efficient charge state preparation and precise setting of inter-dot coupling allows for the control of few-spin qubits, as would be required for the on-demand generation of 2D photonic cluster states or quantum transduction between microwaves and photons. © 2022 The Authors. Advanced Quantum Technologies published by Wiley-VCH GmbH.
    view abstractdoi: 10.1002/qute.202200049
  • 2022 • 1257 Dissecting Mechanochemistry III
    Borchardt, L. and Hernández, J.G.
    Beilstein Journal of Organic Chemistry 18 1454-1456 (2022)
    doi: 10.3762/bjoc.18.150
  • 2022 • 1256 On-Demand Plasmon Nanoparticle-Embedded Laser-Induced Periodic Surface Structures (LIPSSs) on Silicon for Optical Nanosensing
    Borodaenko, Y. and Syubaev, S. and Khairullina, E. and Tumkin, I. and Gurbatov, S. and Mironenko, A. and Mitsai, E. and Zhizhchenko, A. and Modin, E. and Gurevich, E.L. and Kuchmizhak, A.A.
    Advanced Optical Materials 10 (2022)
    doi: 10.1002/adom.202201094
  • 2022 • 1255 Measuring and Modeling Water Sorption in Amorphous Indomethacin and Ritonavir
    Borrmann, D. and Danzer, A. and Sadowski, G.
    Molecular Pharmaceutics 19 998-1007 (2022)
    The amorphous state of an active pharmaceutical ingredient (API) enhances its water solubility compared to its crystalline state. However, it is well known that amorphous substances can absorb significant amounts of water therewith inducing API recrystallization. This work explores methods to obtain reliable information about water sorption in amorphous APIs and its modeling. Experimental water-sorption curves over a broad humidity range were obtained by measuring the mass increase of well-defined films of amorphous APIs. Water-sorption isotherms modeled using perturbed-chain statistical associating fluid theory (PC-SAFT) showed better accordance with the experimental data than those obtained using the Flory-Huggins model. Crank's diffusion equation was used to describe the water-sorption kinetics providing Fickian diffusion coefficients of water in indomethacin and in ritonavir. Stefan-Maxwell diffusion coefficients were obtained by converting Fickian diffusion coefficients using water activity coefficients obtained from PC-SAFT. Finally, the free-volume theory was applied to explain the persistent water concentration dependency of the Stefan-Maxwell diffusion coefficients. © 2022 American Chemical Society. All rights reserved.
    view abstractdoi: 10.1021/acs.molpharmaceut.1c00984
  • 2022 • 1254 Anomalous Water-Sorption Kinetics in ASDs
    Borrmann, D. and Danzer, A. and Sadowski, G.
    Pharmaceutics 14 (2022)
    Anomalous water-sorption kinetics in amorphous solid dispersions (ASDs) are caused by the slow swelling of the polymer. In this work, we used a diffusion–relaxation model with the Williams–Landel–Ferry (WLF) equation and the Arrhenius equation to predict the anomalous water-sorption kinetics in ASDs of poly(vinyl-pyrrolidone)-co-vinyl-acetate (PVPVA) and indomethacin (IND) at 25 °C. These predictions were based on the viscosities of pure PVPVA and pure IND, as well as on the water-sorption kinetics in pure PVPVA. The diffusion–relaxation model was able to predict the different types of anomalous behavior leading to a qualitative and quantitative agreement with the experimental data. Predictions and experiments indicated more pronounced anomalous two-stage water-sorption behavior in the ASDs than in pure PVPVA. This was caused by a higher viscosity of glassy ASD–water mixtures compared to glassy PVPVA–water mixtures at the same distance from their glass transition temperature. These results suggest that this ASD swells more slowly than the polymer it is composed of. The modeling approach applied in this work can be used in the future for predicting diffusion-controlled release behavior or swelling-controlled release behavior of ASDs. © 2022 by the authors.
    view abstractdoi: 10.3390/pharmaceutics14091897
  • 2022 • 1253 Predicting the Water Sorption in ASDs
    Borrmann, D. and Danzer, A. and Sadowski, G.
    Pharmaceutics 14 (2022)
    Water decreases the stability of amorphous solid dispersions (ASDs) and water sorption is, therefore, unwanted during ASD storage. This work suggests a methodology to predict the water-sorption isotherms and the water-sorption kinetics in amorphous pharmaceutical formulations like ASDs. We verified the validity of the proposed methodology by measuring and predicting the water-sorption curves in ASD films of polyvinylpyrrolidone-based polymers and of indomethacin. This way, the extent and the rate of water sorption in ASDs were predicted for drug loads of 0.2 and 0.5 as well as in the humidity range from 0 to 0.9 RH at 25 °C. The water-sorption isotherms and the water-sorption kinetics in the ASDs were predicted only based on the water-sorption isotherms and water-sorption kinetics in the neat polymer on the one hand and in the neat active pharmaceutical ingredient (API) on the other hand. The accurate prediction of water-sorption isotherms was ensured by combining the Perturbed-Chain Statistical Association Theory (PC-SAFT) with the Non-Equilibrium Thermodynamics of Glassy Polymers (NET-GP) approach. Water-sorption kinetics were predicted using Maxwell–Stefan diffusion coefficients of water in the ASDs. © 2022 by the authors. Licensee MDPI, Basel, Switzerland.
    view abstractdoi: 10.3390/pharmaceutics14061181
  • 2022 • 1252 Water Sorption in Glassy Polyvinylpyrrolidone-Based Polymers
    Borrmann, D. and Danzer, A. and Sadowski, G.
    Membranes 12 (2022)
    Polyvinylpyrrolidone (PVP)-based polymers are excellent stabilizers for food supple-ments and pharmaceutical ingredients. However, they are highly hygroscopic. This study measured and modeled the water-sorption isotherms and water-sorption kinetics in thin PVP and PVP-co-vinyl acetate (PVPVA) films. The water sorption was measured at 25 °C from 0 to 0.9 RH, which comprised glassy and rubbery states of the polymer-water system. The sorption behavior of glassy polymers differs from that in the rubbery state. The perturbed-chain statistical associating fluid theory (PC-SAFT) accurately describes the water-sorption isotherms for rubbery polymers, whereas it was combined with the non-equilibrium thermodynamics of glassy polymers (NET-GP) approach to describe the water-sorption in the glassy polymers. Combined NET-GP and PC-SAFT modeling showed excellent agreement with the experimental data. Furthermore, the transitions between the PC-SAFT modeling with and without NET-GP were in reasonable agreement with the glass transition of the polymer-water systems. Furthermore, we obtained Fickian water diffusion coefficients in PVP and in PVPVA from the measured water-sorption kinetics over a broad range of humidities. Maxwell-Stefan and Fickian water diffusion coefficients yielded a non-monotonous water concen-tration dependency that could be described using the free-volume theory combined with PC-SAFT and NET-GP for calculating the free volume. © 2022 by the authors. Licensee MDPI, Basel, Switzerland.
    view abstractdoi: 10.3390/membranes12040434
  • 2022 • 1251 Very high cycle fatigue durability of an additively manufactured single-crystal Ni-based superalloy
    Bortoluci Ormastroni, L.M. and Lopez-Galilea, I. and Pistor, J. and Ruttert, B. and Körner, C. and Theisen, W. and Villechaise, P. and Pedraza, F. and Cormier, J.
    Additive Manufacturing 54 (2022)
    A single crystalline (SX) nickel-based superalloy additively manufactured (AM) by electron beam-based powder bed fusion (PBF-E) was investigated under very high cycle fatigue (VHCF) at 1,000 °C in fully reversed conditions (Rε = −1). Specimens processed using a classical Bridgman solidification route and the impact of a hot isostatic pressing (HIP) treatment were also considered. It is shown that the fatigue lifetime of the AM specimens is higher or in the same range of the Bridgman processed ones with the same chemical composition. All defect-free AM samples fail by surface initiation with very long VHCF lives. In the absence of metallurgical defects such as grain boundaries or pores, the superalloy chemical stability against oxidation governs VHCF failure. © 2022 Elsevier B.V.
    view abstractdoi: 10.1016/j.addma.2022.102759
  • 2022 • 1250 Advancing Critical Chemical Processes for a Sustainable Future: Challenges for Industry and the Max Planck–Cardiff Centre on the Fundamentals of Heterogeneous Catalysis (FUNCAT)
    Bowker, M. and DeBeer, S. and Dummer, N.F. and Hutchings, G.J. and Scheffler, M. and Schüth, F. and Taylor, S.H. and Tüysüz, H.
    Angewandte Chemie - International Edition (2022)
    Catalysis is involved in around 85 % of manufacturing industry and contributes an estimated 25 % to the global domestic product, with the majority of the processes relying on heterogeneous catalysis. Despite the importance in different global segments, the fundamental understanding of heterogeneously catalysed processes lags substantially behind that achieved in other fields. The newly established Max Planck–Cardiff Centre on the Fundamentals of Heterogeneous Catalysis (FUNCAT) targets innovative concepts that could contribute to the scientific developments needed in the research field to achieve net zero greenhouse gas emissions in the chemical industries. This Viewpoint Article presents some of our research activities and visions on the current and future challenges of heterogeneous catalysis regarding green industry and the circular economy by focusing explicitly on critical processes. Namely, hydrogen production, ammonia synthesis, and carbon dioxide reduction, along with new aspects of acetylene chemistry. © 2022 The Authors. Angewandte Chemie International Edition published by Wiley-VCH GmbH.
    view abstractdoi: 10.1002/anie.202209016
  • 2022 • 1249 Role of Anionic Backbone in NHC-Stabilized Coinage Metal Complexes: New Precursors for Atomic Layer Deposition**
    Boysen, N. and Philip, A. and Rogalla, D. and Karppinen, M. and Devi, A.
    Chemistry - A European Journal (2022)
    Cu and Ag precursors that are volatile, reactive, and thermally stable are currently of high interest for their application in atomic-layer deposition (ALD) of thin metal films. In pursuit of new precursors for coinage metals, namely Cu and Ag, a series of new N-heterocyclic carbene (NHC)-based CuI and AgI complexes were synthesized. Modifications in the substitution pattern of diketonate-based anionic backbones led to five monomeric Cu complexes and four closely related Ag complexes with the general formula [M(tBuNHC)(R)] (M=Cu, Ag; tBuNHC=1,3-di-tert-butyl-imidazolin-2-ylidene; R=diketonate). Thermal analysis indicated that most of the Cu complexes are thermally stable and volatile compared to the more fragile Ag analogs. One of the promising Cu precursors was evaluated for the ALD of nanoparticulate Cu metal deposits by using hydroquinone as the reducing agent at appreciably low deposition temperatures (145–160 °C). This study highlights the considerable impact of the employed ligand sphere on the structural and thermal properties of metal complexes that are relevant for vapor-phase processing of thin films. © 2022 The Authors. Chemistry - A European Journal published by Wiley-VCH GmbH.
    view abstractdoi: 10.1002/chem.202103798
  • 2022 • 1248 High-Performance Iridium Thin Films for Water Splitting by CVD Using New Ir(I) Precursors
    Boysen, N. and Wree, J.-L. and Zanders, D. and Rogalla, D. and Öhl, D. and Schuhmann, W. and Devi, A.
    ACS Applied Materials and Interfaces 14 52149-52162 (2022)
    doi: 10.1021/acsami.2c13865
  • 2022 • 1247 Influence of a Partial Substitution of Co by Fe on the Phase Stability and Fatigue Behavior of a CoCrWC Hard Alloy at Room Temperature
    Brackmann, L. and Schuppener, J. and Röttger, A. and Weber, S.
    Metallurgical and Materials Transactions A: Physical Metallurgy and Materials Science 53 2708-2723 (2022)
    The deformation-induced phase transition from fcc to hcp causes local embrittlement of the metal matrix in Cobalt-base alloys, facilitating subcritical crack growth under cyclic loading and reducing fatigue resistance. Our approach to increasing the fatigue life of Co-based hard alloys is to suppress the phase transition from fcc to hcp by an alloy modification that increases the stacking fault energy (SFE) of the metal matrix. Therefore, we substitute various contents (15, 25, and 35 mass pct) of Co by Fe and analyze the effect on the fatigue life and resistance against subcritical crack growth. Subcritical crack growth in the specimens takes place in a cyclic load test. The proceeding crack growth and the occurrence of phase transformations are monitored by scanning electron microscope (SEM) investigations and electron backscatter diffraction (EBSD). We determined an SFE of 35 mJ/m2 at an iron content of 35 mass pct, which leads to a change of the main deformation mechanism from deformation-induced martensitic transformation to deformation twinning. Analysis of cyclically loaded specimens revealed that the resistance against subcritical crack growth in the metal matrix is facilitated with increasing Fe content, leading to a significant increase in fatigue life. © 2022, The Author(s).
    view abstractdoi: 10.1007/s11661-022-06700-7
  • 2022 • 1246 Effective hyperelastic material parameters from microstructures constructed using the planar Boolean model
    Brändel, M. and Brands, D. and Maike, S. and Rheinbach, O. and Schröder, J. and Schwarz, A. and Stoyan, D.
    Computational Mechanics (2022)
    We construct two-dimensional, two-phase random heterogeneous microstructures by stochastic simulation using the planar Boolean model, which is a random collection of overlapping grains. The structures obtained are discretized using finite elements. A heterogeneous Neo-Hooke law is assumed for the phases of the microstructure, and tension tests are simulated for ensembles of microstructure samples. We determine effective material parameters, i.e., the effective Lamé moduli λ∗ and μ∗, on the macroscale by fitting a macroscopic material model to the microscopic stress data, using stress averaging over many microstructure samples. The effective parameters λ∗ and μ∗ are considered as functions of the microscale material parameters and the geometric parameters of the Boolean model including the grain shape. We also consider the size of the Representative Volume Element (RVE) given a precision and an ensemble size. We use structured and unstructured meshes and also provide a comparison with the FE2 method. © 2022, The Author(s).
    view abstractdoi: 10.1007/s00466-022-02142-5
  • 2022 • 1245 Electrooxidation of Alcohols on Mixed Copper–Cobalt Hydroxycarbonates in Alkaline Solution
    Braun, M. and Behrendt, G. and Krebs, M.L. and Dimitri, P. and Kumar, P. and Sanjuán, I. and Cychy, S. and Brix, A.C. and Morales, D.M. and Hörlöck, J. and Hartke, B. and Muhler, M. and Schuhmann, W. and Behrens, M. and Andronescu, C.
    ChemElectroChem 9 (2022)
    doi: 10.1002/celc.202200267
  • 2022 • 1244 SUSTAINABILITY OF CONCRETE PAVEMENTS CONSIDERING TRAFFIC AND DE-ICING AGENTS
    Breitenbücher, R. and Przondziono, R.
    Acta Polytechnica CTU Proceedings 33 45-51 (2022)
    doi: 10.14311/APP.2022.33.0045
  • 2022 • 1243 Indirect Electrooxidation of Methane to Methyl Bisulfate on a Boron-Doped Diamond Electrode
    Britschgi, J. and Bilke, M. and Schuhmann, W. and Schüth, F.
    ChemElectroChem 9 (2022)
    Although highly desired and studied for decades, direct methane functionalization to liquid products remains a challenge. We report an electrochemical system using a boron-doped diamond (BDD) anode in concentrated sulfuric acid that is able to convert methane to methyl bisulfate and methanesulfonic acid without the use of a catalyst by indirect electrochemical oxidation. Due to its high material stability, BDD can be operated at high current densities. High temperature (140 °C) and pressure (70 bar) support the formation of methyl bisulfate to concentrations as high as 160 mM in 3 h and methanesulfonic acid to concentrations of up to 750 mM in 8 h. We present a novel way of catalyst-free electrochemical methane oxidation and show general trends and limitations of this reaction. © 2021 The Authors. ChemElectroChem published by Wiley-VCH GmbH
    view abstractdoi: 10.1002/celc.202101253
  • 2022 • 1242 Electrochemically Initiated Synthesis of Methanesulfonic Acid
    Britschgi, J. and Kersten, W. and Waldvogel, S.R. and Schüth, F.
    Angewandte Chemie - International Edition (2022)
    The direct sulfonation of methane to methanesulfonic acid was achieved in an electrochemical reactor without adding peroxide initiators. The synthesis proceeds only from oleum and methane. This is possible due to in situ formation of an initiating species from the electrolyte at a boron-doped diamond anode. Elevated pressure, moderate temperature and suitable current density are beneficial to reach high concentration at outstanding selectivity. The highest concentration of 3.7 M (approximately 62 % yield) at 97 % selectivity was reached with a stepped electric current program at 6.25–12.5 mA cm−2, 70 °C and 90 bar methane pressure in 22 hours. We present a novel, electrochemical method to produce methanesulfonic acid, propose a reaction mechanism and show general dependencies between parameters and yields for methanesulfonic acid. © 2022 The Authors. Angewandte Chemie International Edition published by Wiley-VCH GmbH.
    view abstractdoi: 10.1002/anie.202209591
  • 2022 • 1241 Structure-Performance Relationship of LaFe1-xCoxO3 Electrocatalysts for Oxygen Evolution, Isopropanol Oxidation, and Glycerol Oxidation
    Brix, A.C. and Dreyer, M. and Koul, A. and Krebs, M. and Rabe, A. and Hagemann, U. and Varhade, S. and Andronescu, C. and Behrens, M. and Schuhmann, W. and Morales, D.M.
    ChemElectroChem 9 (2022)
    Mitigating high energy costs related to sustainable H2 production via water electrolysis is important to make this process commercially viable. Possible approaches are the investigation of low-cost, highly active oxygen evolution reaction (OER) catalysts and the exploration of alternative anode reactions, such as the electrocatalytic isopropanol oxidation reaction (iPOR) or the glycerol oxidation reaction (GOR), offering the possibility of simultaneously lowering the anodic overpotential and generating value-added products. A suitable class of catalysts are non-noble metal-based perovskites with the general formula ABO3, featuring rare-earth metal cations at the A- and transition metals at the B-site. We synthesised a series of LaFe1-xCoxO3 materials with x=0–0.70 by automated co-precipitation at constant pH and subsequent calcination at 800 °C. X-ray diffraction studies revealed that the phase purity was preserved in samples with x≤0.3. The activity towards the OER, iPOR, and GOR was investigated by rotating disk electrode voltammetry, showing a relation between structure and metal composition with the activity trends observed for the three reactions. Additionally, GOR product analysis via high-performance liquid chromatography (HPLC) was conducted after 24 and 48 h electrolysis in a circular flow-through cell setup, pointing out a trade-off between activity and selectivity. © 2022 The Authors. ChemElectroChem published by Wiley-VCH GmbH
    view abstractdoi: 10.1002/celc.202200092
  • 2022 • 1240 Effect of composition and nanostructure on the mechanical properties and thermal stability of Zr100-xCux thin film metallic glasses
    Brognara, A. and Best, J.P. and Djemia, P. and Faurie, D. and Dehm, G. and Ghidelli, M.
    Materials and Design 219 (2022)
    doi: 10.1016/j.matdes.2022.110752
  • 2022 • 1239 Rejuvenation in Deep Thermal Cycling of a Generic Model Glass: A Study of Per-Particle Energy Distribution
    Bruns, M. and Varnik, F.
    Materials 15 (2022)
    We investigate the effect of low temperature (cryogenic) thermal cycling on a generic model glass and observe signature of rejuvenation in terms of per-particle potential energy distributions. Most importantly, these distributions become broader and its average values successively increase when applying consecutive thermal cycles. We show that linear dimension plays a key role for these effects to become visible, since we do only observe a weak effect for a cubic system of roughly one hundred particle diameter but observe strong changes for a rule-type geometry with the longest length being two thousand particle diameters. A consistent interpretation of this new finding is provided in terms of a competition between relaxation processes, which are inherent to glassy systems, and excitation due to thermal treatment. In line with our previous report (Bruns et al., PRR 3, 013234 (2021)), it is shown that, depending on the parameters of thermal cycling, rejuvenation can be either too weak to be detected or strong enough for a clear observation. © 2022 by the authors. Licensee MDPI, Basel, Switzerland.
    view abstractdoi: 10.3390/ma15030829
  • 2022 • 1238 Enhanced dynamics in deep thermal cycling of a model glass
    Bruns, M. and Varnik, F.
    Journal of Chemical Physics 156 (2022)
    We investigate the effect of low temperature (cryogenic) thermal cycling on dynamics of a generic model glass via molecular dynamics simulations. By calculating mean squared displacements after a varying number of cycles, a pronounced enhancement of dynamics is observed. This rejuvenation effect is visible already after the first cycle and accumulates upon further cycling in an intermittent way. Our data reveal an overall deformation (buckling of the slab-shaped system) modulated by a heterogeneous deformation field due to deep cryogenic thermal cycling. It is shown via strain maps that deformation localizes in the form of shear-bands, which gradually fill the entire sample in a random and intermittent manner, very much similar to the accumulation effect observed in dynamics. While spatial organization of local strain may be connected to the specific geometry, we argue that the heterogeneity of the structure is the main cause behind rejuvenation effects observed in the present study. © 2022 Author(s).
    view abstractdoi: 10.1063/5.0094024
  • 2022 • 1237 Cobalt Oxide Nanowires with Controllable Diameters and Crystal Structures for the Oxygen Evolution Reaction
    Budiyanto, E. and Tüysüz, H.
    European Journal of Inorganic Chemistry 2022 (2022)
    Herein, mesoporous cobalt oxides with nanowire morphology were size-selectively synthesized via nanocasting and used as a model system to reveal the impact of diameter, pore, and crystal structures toward the alkaline water electrolysis. A range of Co3O4 nanowires with variable diameters was prepared by replication of SBA-15 silica with different degree of interconnectivity and pore sizes. These nanowires could be further transformed to CoO rock-salt structure through a selective reduction process by keeping the initial morphology and textural parameters. The electrocatalytic screening showed that CoO with the smallest nanowire diameter and open pore structure showed superior activity in the electrochemical oxygen evolution reaction (OER) due to the higher amount of available active centers and defect sites. The overpotential to reach 10 mA/cm2 drops from 392 to 337 mV after reduction of Co3O4 to CoO. An in situ Raman spectroscopy investigation showed that Co3O4 retained its bulk crystalline spinel phase while CoO faced an irreversible phase transformation into a distorted spinel structure after OER. © 2022 The Authors. European Journal of Inorganic Chemistry published by Wiley-VCH GmbH.
    view abstractdoi: 10.1002/ejic.202200065
  • 2022 • 1236 Phase Segregation in Cobalt Iron Oxide Nanowires toward Enhanced Oxygen Evolution Reaction Activity
    Budiyanto, E. and Salamon, S. and Wang, Y. and Wende, H. and Tüysüz, H.
    JACS Au 2 697-710 (2022)
    doi: 10.1021/jacsau.1c00561
  • 2022 • 1235 Structurally characterised intermediate of the oxidative addition of a heteroleptic germylene to gallanediyle
    Bücker, A. and Wölper, C. and Haberhauer, G. and Schulz, S.
    Chemical Communications 58 9758-9761 (2022)
    Bond activation reactions using main group metal complexes are gaining increasing interest. We report on reactions of LGa (L = HC[C(Me)N(Ar)]2, Ar = Dipp = 2,6-i-Pr2C6H3,) with heteroleptic tetrylenes L′ECl (E = Ge, Sn; L′ = N(SiMe3)Ar), yielding the donor-acceptor complex LGa-Sn(Cl)L′ (1) or the oxidative addition product L(Cl)GaGeL′ (3). The reaction with DMPGeCl (DMP = 2,6-Mes2C6H3, Mes = 2,4,6-Me3C6H2) yielded LGa(μ-Cl)GeDMP (2), which represents an intermediate of the oxidative addition reaction. 1-3 were characterized by NMR and IR spectroscopy as well as by single crystal X-ray diffraction (sc-XRD), while their electronic nature was analyzed by quantum chemical calculations. © 2022 The Royal Society of Chemistry.
    view abstractdoi: 10.1039/d2cc03561h
  • 2022 • 1234 Structure-activity correlation in aerobic cyclohexene oxidation and peroxide decomposition over CoxFe3−xO4 spinel oxides
    Büker, J. and Angel, S. and Salamon, S. and Landers, J. and Falk, T. and Wende, H. and Wiggers, H. and Schulz, C. and Muhler, M. and Peng, B.
    Catalysis Science and Technology 12 3594-3605 (2022)
    Nanoparticulate CoxFe3−xO4 (0 ≤ x ≤ 3) catalysts were prepared by spray-flame synthesis and applied in liquid-phase cyclohexene oxidation with O2 as oxidant. The catalysts were characterized in detail using N2 physisorption, XRD, TEM, XPS, FTIR, Raman, and Mössbauer spectroscopy. A volcano plot was obtained for the catalytic activity in cyclohexene oxidation as a function of the Co content with a maximum at x = 1. Thus, CoFe2O4 achieved the highest degree of cyclohexene conversion and the fastest decomposition rate of the key intermediate 2-cyclohexene-1-hydroperoxide. Kinetic studies and a stability test were performed over CoFe2O4, showing that cyclohexene oxidation follows first-order kinetics with an apparent activation energy of 58 kJ mol−1. The catalytic hydroperoxide decomposition during cyclohexene oxidation was further investigated using H2O2 and tert-butyl hydroperoxide as simpler surrogates resulting in similar volcano-type correlations. The increase in catalytic activity with increasing Fe content with a maximum at x = 1 is ascribed to the increasing concentration of octahedrally coordinated Co2+ cations in the spinel structure leading to the presence of coordinatively unsaturated Co3c2+ surface sites, which are identified to be the most active sites for 2-cyclohexene-1-hydroperoxide decomposition in cyclohexene oxidation. © 2022 The Royal Society of Chemistry
    view abstractdoi: 10.1039/d2cy00505k
  • 2022 • 1233 Microfiltration of polymeric microgels as soft model colloids through sterile filter membranes
    Büning, D. and Ennen-Roth, F. and Netke, T. and Schumacher, J. and Ulbricht, M.
    Journal of Membrane Science 649 (2022)
    In this work, filtration studies were performed with particles of soft or super-soft nature, made from polyacrylamide copolymers, and hard polystyrene reference particles, all having average diameters between 180 and 200 nm, at relatively high particle concentrations and different transmembrane pressures under stirred and non-stirred dead-end filtration conditions in order to evaluate the separation and fouling behavior of a commercially available high-flux microfiltration membrane (experimentally determined barrier pore diameter 210 nm). In order to identify the underlying fouling processes the dependencies of the flux on cumulative volume or time were analyzed in the frame of established models. It was found that low transmembrane pressures of 0.1 bar lead to immediate filter cake formation, that facilitates a high retention of the particles and leads to less fouling that cannot be removed by external washing. Medium to high pressures (0.5–2.0 bar) resulted in a pronounced penetration of microgel particles into the membrane structure and pore blocking in the first phase (I) of the filtration, before entering the cake formation phase (II); the particle rejection in phase I was lower and the extent of fouling remaining after washing was larger. Super-soft microgels showed a significantly more pronounced pore blocking phase (I), compared to their soft counterparts or the hard sphere reference particles. The results of the study yield deeper insights into retention and blocking mechanisms during filtrations of deformable microgels as model colloids with a benchmark sterile filtration membrane. This is relevant for purification of such polymeric materials after their synthesis or for the development of test systems mimicking the removal of microorganisms by sterile filtration. © 2022 Elsevier B.V.
    view abstractdoi: 10.1016/j.memsci.2022.120364
  • 2022 • 1232 A CutFEM based framework for numerical simulations of machine driven tunnels with arbitrary alignments
    Bui, H.-G. and Schillinger, D. and Zendaki, Y. and Meschke, G.
    Computers and Geotechnics 144 (2022)
    We describe a novel computational framework based on the cut finite element method (CutFEM) for process-oriented simulation in mechanized tunneling. The framework incorporates all relevant components required for the simulation of the tunnel advance process, namely the ground, the staged installation of the lining support, the tail void grouting and the tunnel boring machine. We demonstrate that CutFEM concepts can significantly facilitate the modeling, discretization and coupling of the different components, while maintaining the same accuracy as the standard boundary-fitted finite element method. The proposed CutFEM technology, which is being applied and investigated in the context of advancement simulations in mechanized tunneling for the first time, enables the seamless analysis of an arbitrary number of different tunnel alignment variants on the same structured background mesh without the need to set up a new model for each variant. This is a shift of paradigm in simulation-supported tunnel design, as the CutFEM based framework considerably facilitates a direct integration of geometric, building information and simulation models in early stages of a tunnel project. The simulation model allows for the damage assessment of the buildings during tunnel advancement with regards to different excavation scenarios, as shown in the numerical examples in this paper. © 2022 Elsevier Ltd
    view abstractdoi: 10.1016/j.compgeo.2022.104637
  • 2022 • 1231 The key features of SARS-CoV-2 leader and NSP1 required for viral escape of NSP1-mediated repression
    Bujanic, L. and Shevchuk, O. and von Kügelgen, N. and Kalinina, A. and Ludwik, K. and Koppstein, D. and Zerna, N. and Sickmann, A. and Chekulaeva, M.
    RNA 28 766-779 (2022)
    SARS-CoV-2, responsible for the ongoing global pandemic, must overcome a conundrum faced by all viruses. To achieve its own replication and spread, it simultaneously depends on and subverts cellular mechanisms. At the early stage of infection, SARS-CoV-2 expresses the viral nonstructural protein 1 (NSP1), which inhibits host translation by blocking the mRNA entry tunnel on the ribosome; this interferes with the binding of cellular mRNAs to the ribosome. Viral mRNAs, on the other hand, overcome this blockade. We show that NSP1 enhances expression of mRNAs containing the SARS-CoV-2 leader. The first stem–loop (SL1) in the viral leader is both necessary and sufficient for this enhancement mechanism. Our analysis pinpoints specific residues within SL1 (three cytosine residues at the positions 15, 19, and 20) and another within NSP1 (R124), which are required for viral evasion, and thus might present promising drug targets. We target SL1 with the antisense oligo (ASO) to efficiently and specifically down-regulate SARS-CoV-2 mRNA. Additionally, we carried out analysis of a functional interactome of NSP1 using BioID and identified components of antiviral defense pathways. Our analysis therefore suggests a mechanism by which NSP1 inhibits the expression of host genes while enhancing that of viral RNA. This analysis helps reconcile conflicting reports in the literature regarding the mechanisms by which the virus avoids NSP1 silencing. © 2022 Bujanic et al.
    view abstractdoi: 10.1261/RNA.079086.121
  • 2022 • 1230 Development of polysulfone ultrafiltration membranes with enhanced antifouling performance for the valorisation of side streams in the pulp and paper industry
    Burts, K.S. and Plisko, T.V. and Bildyukevich, A.V. and Rodrigues, G. and Sjölin, M. and Lipnizki, F. and Ulbricht, M.
    Colloids and Surfaces A: Physicochemical and Engineering Aspects 632 (2022)
    One-stage method of polysulfone (PSf) membrane modification by the addition of polyacrylic acid (PAA, Mn = 250 kg·mol−1) to the coagulation bath during membrane preparation via non-solvent induced phase separation (NIPS) was proposed. The effect of PAA concentration on the membrane structure, hydrophilicity, zeta potential, separation performance and antifouling stability in ultrafiltration of lysozyme, polyvinylpyrrolidone (PVP K-30, Mn = 40 kg mol−1) and humic acid model solutions as well as thermomechanical pulp mill process (ThMP) water was studied. Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM), atomic force microscopy (AFM), measurements of the tangential flow streaming potential and water contact angle were used for membrane characterization. It was found that addition of PAA into coagulation bath resulted in decreasing pore size and porosity of the selective layer as well as the formation of a thicker and denser selective layer. Water contact angle of the modified membranes was found to decrease significantly and zeta potential of the selective layer was shown to become more negative in the studied pH range 3–10, all compared to the reference membrane. It was revealed that pure water flux (PWF) decreased and lysozyme and PVP K-30 rejection increased with the increase in PAA concentration in the coagulation bath. It was found that membranes modified with PAA demonstrated better antifouling stability in ultrafiltration of humic acid solution and ThMP process water. Modified membranes were found to have higher flux, fouling recovery ratio and hemicelluloses rejection in ThMP process water ultrafiltration compared to the reference PSf membrane that allows application of these membranes for hemicelluloses concentration and purification. © 2021 Elsevier B.V.
    view abstractdoi: 10.1016/j.colsurfa.2021.127742
  • 2022 • 1229 Development of Antifouling Polysulfone Membranes by Synergistic Modification with Two Different Additives in Casting Solution and Coagulation Bath: Synperonic F108 and Polyacrylic Acid
    Burts, K.S. and Plisko, T.V. and Sjölin, M. and Rodrigues, G. and Bildyukevich, A.V. and Lipnizki, F. and Ulbricht, M.
    Materials 15 (2022)
    This study deals with the development of antifouling ultrafiltration membranes based on polysulfone (PSF) for wastewater treatment and the concentration and purification of hemicellulose and lignin in the pulp and paper industry. The efficient simple and reproducible technique of PSF membrane modification to increase antifouling performance by simultaneous addition of triblock copolymer polyethylene glycol-polypropylene glycol-polyethylene glycol (Synperonic F108, Mn =14 × 103 g mol−1) to the casting solution and addition of polyacrylic acid (PAA, Mn = 250 × 103 g mol−1) to the coagulation bath is proposed for the first time. The effect of the PAA concentration in the aqueous solution on the PSF/Synperonic F108 membrane structure, surface characteristics, performance, and antifouling stability was investigated. PAA concentrations were varied from 0.35 to 2.0 wt.%. Membrane composition, structure, and topology were investigated by Fourier-transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM), and scanning electron microscopy (SEM). The addition of PAA into the coagulation bath was revealed to cause the formation of a thicker and denser selective layer with decreasing its pore size and porosity; according to the structural characterization, an interpolymer complex of the two additives was formed on the surface of the PSF membrane. Hydrophilicity of the membrane selective layer surface was shown to increase significantly. The selective layer surface charge was found to become more negative in comparison to the reference membrane. It was shown that PSF/Synperonic F108/PAA membranes are characterized by better antifouling performance in ultrafiltration of humic acid solution and thermomechanical pulp mill (ThMP) process water. Membrane modification with PAA results in higher ThMP process water flux, fouling recovery ratio, and hemicellulose and total lignin rejection compared to the reference PSF/Synperonic F108 membrane. This suggests the possibility of applying the developed membranes for hemicellulose concentration and purification. © 2022 by the authors. Licensee MDPI, Basel, Switzerland.
    view abstractdoi: 10.3390/ma15010359
  • 2022 • 1228 Assessing the NLRP3 Inflammasome Activating Potential of a Large Panel of Micro- and Nanoplastics in THP-1 Cells
    Busch, M. and Bredeck, G. and Waag, F. and Rahimi, K. and Ramachandran, H. and Bessel, T. and Barcikowski, S. and Herrmann, A. and Rossi, A. and Schins, R.P.F.
    Biomolecules 12 (2022)
    doi: 10.3390/biom12081095
  • 2022 • 1227 Metal Artefact Reduction Sequences (MARS) in Magnetic Resonance Imaging (MRI) after Total Hip Arthroplasty (THA): A non-invasive approach for preoperative differentiation between periprosthetic joint infection (PJI) and aseptic complications?
    Busch, A. and Jäger, M. and Beck, S. and Wegner, A. and Portegys, E. and Wassenaar, D. and Theysohn, J. and Haubold, J.
    BMC Musculoskeletal Disorders 23 (2022)
    doi: 10.1186/s12891-022-05560-x
  • 2022 • 1226 Ion-induced secondary electron emission of oxidized nickel and copper studied in beam experiments
    Buschhaus, R. and Prenzel, M. and Von Keudell, A.
    Plasma Sources Science and Technology 31 (2022)
    Ion-induced secondary electron emission at a target surface is an essential mechanism for laboratory plasmas, i.e. magnetron sputtering discharges. Electron emission, however, is strongly affected by the target condition itself such as oxidation. Data of oxidized targets, however, are very sparse and prone to significant systematic errors, because they were often determined by modeling the complex behavior of the plasma. Thus, it is difficult to isolate the process of ion-induced electron emission from all other plasma-surface-interactions. By utilizing ion beams, the complex plasma environment is avoided and electron yields are determined with higher accuracy. In this study, ion-induced secondary electron emission coefficients (SEECs) of clean, untreated (air-exposed), and intentionally oxidized copper and nickel surfaces were investigated in such a particle beam experiment. Pristine and oxidized metal foils were exposed to beams of singly charged argon ions with energies of 0.2 keV-10 keV. After the ion beam treatment, the surface conditions were analyzed by ex-situ X-ray photoelectron spectroscopy measurements. Further, a model for the electron emission of a partly oxidized surface is presented, which is in agreement with the experimental data. It was found, that oxidized and untreated/air-exposed surfaces do not show the same SEEC: for intentionally oxidized targets, the electron yields were smaller by a factor of 2 than for untreated/air-exposed surfaces. SEECs of oxides were found to be between the values for clean and for untreated metal surfaces. Further, the SEEC was at maximum for untreated/air-exposed surfaces and at minimum for clean surfaces; the electron yields of untreated/air-exposed and clean surfaces were in agreement with values reported in the literature. © 2022 The Author(s). Published by IOP Publishing Ltd.
    view abstractdoi: 10.1088/1361-6595/ac4c4c
  • 2022 • 1225 Combustion of Straw Pellets in an Agitated Fuel Bed: Experiments and DEM/CFD Simulations
    Buss, F. and Wirtz, S. and Scherer, V.
    Combustion Science and Technology 194 195-212 (2022)
    The influence of bed agitation during the combustion of biomass pellets was investigated experimentally and numerically. In the experiments, a bulk of straw pellets was burnt in a batch-operated reactor. The reactor allows for air staging and mixing of the fuel bed by vertically moveable mixing elements. The primary to secondary air ratio was varied and the reactor was operated either in the agitated (moving mixing elements) or the static mode (mixing elements at rest). The overall mass of the bulk was measured continuously during the combustion process. The results show a significant increase of the mass loss rate by almost 60% when the bed was agitated compared to the static case. Samples of the residual material of the pellets reveal a totally different amount of molten and agglomerated ash particles for the different operational conditions. Decreased primary to secondary air ratios as well as agitation of the fuel bed did lead to less agglomeration of the ash. The Discrete Element Method (DEM) was coupled with a Computational Fluid Dynamics (CFD) simulation. Coupled DEM/CFD simulations of the batch reactor were performed to get access to bulk internal data of the solid material and the fluid phase. Simulations identified that a reduced amount of ash exposed to the volatile flame through agitation of the fuel bed was the main reason for minimized ash agglomeration. © 2019 Taylor & Francis Group, LLC.
    view abstractdoi: 10.1080/00102202.2019.1678844
  • 2022 • 1224 Strain rate dependent deformation behavior of BCC-structured Ti29Zr24Nb23Hf24 high entropy alloy at elevated temperatures
    Cao, T. and Guo, W. and Lu, W. and Xue, Y. and Lu, W. and Su, J. and Liebscher, C.H. and Li, C. and Dehm, G.
    Journal of Alloys and Compounds 891 (2022)
    The mechanical behavior and deformation mechanisms of a body-centered cubic (BCC) Ti29Zr24Nb23Hf24 (at%) high entropy alloy (HEA) was investigated in temperatures and strain rates from 700° to 1100 °C and 10−3 to 10 s−1, respectively. The HEA exhibits a substantial increase in yield stress with increasing strain rate. The strain rate sensitivity (SRS) coefficient is ~3 times that of BCC alloy Nb-1Zr and even ~3.5 times that of pure Nb. This high SRS is attributed to the high Peierls stress of the HEA, which is about twice the Peierls stress of pure Nb. On the other hand, the flow stress exhibits a tendency from strain softening to strain hardening with the increase of strain rate especially at the relatively low temperatures. This behavior is explained by a change in dislocation motion from climbing to multiple slip with the increase of strain rate. Taking the specimen subjected to 800 ºC for example, dislocation walls formed at the early stage of deformation and at low strain rate of 10−3 s−1. In this case there is sufficient time to activate dislocations climb, which results in discontinuous dynamic recrystallization, and strain softening. However, when the strain rate amounts to 1 s−1, thermally activated processes such as dislocation climb are too sluggish. As a consequence, multiple slip systems are activated, and the dislocation interactions lead to the evolution of deformation bands, leading to strain hardening. © 2021 Elsevier B.V.
    view abstractdoi: 10.1016/j.jallcom.2021.161859
  • 2022 • 1223 Real-Time Risk Assessment of Tunneling-Induced Building Damage Considering Polymorphic Uncertainty
    Cao, B.T. and Obel, M. and Freitag, S. and Heußner, L. and Meschke, G. and Mark, P.
    ASCE-ASME Journal of Risk and Uncertainty in Engineering Systems, Part A: Civil Engineering 8 (2022)
    The risk assessment of tunneling-induced damage in buildings is a challenging task in geotechnical and structural engineering. It is important to consider the soil-structure interaction during the tunnel construction process. In this paper, finite-element (FE) simulation models of mechanized tunneling processes are combined with FE models of buildings to predict tunneling-induced damage. The soil-structure interaction is taken into account by considering the building stiffness in the tunneling process simulation model and by applying the computed foundation settlements as boundary conditions of the building model. The building damage risk is assessed by means of strains in the structural members and a corresponding category of damage is determined. Uncertainties of the geotechnical parameters and the structural parameters are quantified as random variables and intervals in the framework of polymorphic uncertainty modeling. For real-time predictions, the FE simulation models are approximated by artificial neural networks. This makes it possible to predict the structural damage risk according to scenarios of the operational tunneling process parameters in order to assist machine drivers during tunnel construction. © 2021 American Society of Civil Engineers.
    view abstractdoi: 10.1061/AJRUA6.0001192
  • 2022 • 1222 Annealing-Dependent Morphotropic Phase Boundary in the BiMg0.5Ti0.5O3–BiZn0.5Ti0.5O3 Perovskite System
    Cardoso, J.P.V. and Shvartsman, V.V. and Pushkarev, A.V. and Radyush, Y.V. and Olekhnovich, N.M. and Khalyavin, D.D. and Čižmár, E. and Feher, A. and Salak, A.N.
    Materials 15 (2022)
    The annealing behavior of (1-x)BiMg0.5Ti0.5O3–xBiZn0.5Ti0.5O3 [(1-x)BMT–xBZT] perovskite solid solutions synthesized under high pressure was studied in situ via X-ray diffraction and piezoresponse force microscopy. The as prepared ceramics show a morphotropic phase boundary (MPB) between the non-polar orthorhombic and ferroelectric tetragonal states at 75 mol. % BZT. It is shown that annealing above 573 K results in irreversible changes in the phase diagram. Namely, for compositions with 0.2 &lt; x &lt; 0.6, the initial orthorhombic phase transforms into a ferroelectric rhombohedral phase. The new MPB between the rhombohedral and tetragonal phases lies at a lower BZT content of 60 mol. %. The phase diagram of the BMT–BZT annealed ceramics is formally analogous to that of the commercial piezoelectric material lead zirconate titanate. This makes the BMT–BZT system promising for the development of environmentally friendly piezoelectric ceramics. © 2022 by the authors.
    view abstractdoi: 10.3390/ma15196998
  • 2022 • 1221 Free, flexible and fast: Orientation mapping using the multi-core and GPU-accelerated template matching capabilities in the Python-based open source 4D-STEM analysis toolbox Pyxem
    Cautaerts, N. and Crout, P. and Ånes, H.W. and Prestat, E. and Jeong, J. and Dehm, G. and Liebscher, C.H.
    Ultramicroscopy 237 (2022)
    doi: 10.1016/j.ultramic.2022.113517
  • 2022 • 1220 Interfacial Properties of Deep Eutectic Solvents by Density Gradient Theory
    Cea-Klapp, E. and Gajardo-Parra, N. and Aravena, P. and Quinteros-Lama, H. and Held, C. and Canales, R.I. and Garrido, J.M.
    Industrial and Engineering Chemistry Research 61 2580-2591 (2022)
    Deep eutectic solvents (DES) are room-temperature liquid mixtures constituted of a hydrogen-bonding acceptor (HBA) and a hydrogen-bonding donor (HBD). They have high practical potential due to their versatility, quick preparation, and wide applications. Therefore, it is appropriate to have robust models to predict their properties. In this work, the density gradient theory has been combined with the perturbed-chain statistical associating fluid theory to model and understand the interfacial behavior in systems of deep eutectic solvents. DESs were modeled as mixtures of their constituents, and a methodology is proposed for estimating the chemical potential of DESs to extend their study to the interfacial properties. Available experimental data of hydrophilic and hydrophobic DESs were used to calculate the influence parameters, providing a way to linearize them in terms of the molecular parameters of HBDs and their molar ratio between HBD and HBA. This treatment has made it feasible to predict the thermal dependence of surface tension in most of the DESs analyzed with an average absolute relative deviation of 1.26%. Furthermore, density gradient theory and perturbed-chain statistical associating fluid theory were applied to predict the vapor-liquid surface tension in mixtures of organic compounds with DES. In particular, we have calculated the surface tension in mixtures of ChCl-glycerol and ChCl-lactic acid with water, ethanol, propanol, phenol, acetone, and ethyl acetate without fitting binary interaction parameters. The behavior of density profiles suggests that the surface is enriched with DES components for the DES + water mixtures. In contrast, it is enriched with diluent for the other ternary systems (ethanol, isopropanol, phenol, acetone, and ethyl acetate). © 2022 American Chemical Society
    view abstractdoi: 10.1021/acs.iecr.1c03817
  • 2022 • 1219 Aerosol-Based Synthesis of Multi-metal Electrocatalysts for Oxygen Evolution and Glycerol Oxidation
    Cechanaviciute, I.A. and Bobrowski, T. and Jambrec, D. and Krysiak, O.A. and Brix, A.C. and Braun, M. and Quast, T. and Wilde, P. and Morales, D.M. and Andronescu, C. and Schuhmann, W.
    ChemElectroChem 9 (2022)
    doi: 10.1002/celc.202200107
  • 2022 • 1218 Formation of tungsten carbide by focused ion beam process: A route to high magnetic field resilient patterned superconducting nanostructures
    Chakraborti, H. and Joshi, B.P. and Barman, C.K. and Jain, A.K. and Pal, B. and Barik, B.C. and Maiti, T. and Schott, R. and Wieck, A.D. and Prasad, M.J.N.V. and Dhar, S. and Pal, H.K. and Alam, A. and Das Gupta, K.
    Applied Physics Letters 120 (2022)
    A scale for magnetic field resilience of a superconductor is set by the paramagnetic limit. Comparing the condensation energy of the Bardeen-Cooper-Schrieffer (BCS) singlet ground state with the paramagnetically polarized state suggests that for an applied field μ 0 H > 1.8 T c (in SI), singlet pairing is not energetically favorable. Materials exceeding or approaching this limit are interesting from fundamental and technological perspectives. This may be a potential indicator of triplet superconductivity, Fulde-Ferrell-Larkin-Ovchinnikov (FFLO) pairing, and other mechanisms involving topological aspects of surface states and may also allow Cooper pair injection at high magnetic fields. We have analyzed the microscopic composition of such a material arising from an unexpected source. A microjet of an organo-metallic gas, W [(CO) 6], can be decomposed by a gallium ion-beam, leaving behind a track of complex residue of gallium, tungsten, and carbon with remarkable superconducting properties, like an upper critical field, H c 2 > 10 T, above its paramagnetic limit. We carried out atomic probe tomography to establish the formation of nano-crystalline tungsten carbide (WC) in the tracks and the absence of free tungsten. Supporting calculations show that for Ga distributed on the surface of WC, its s,p-orbitals enhance the density of states near the Fermi energy. The observed variation of H c 2 (T) does not show features typical of enhancement of critical field due to granularity. Our observations may be significant in the context of some recent theoretical calculation of the band structure of WC and experimental observation of superconductivity in a WC-metal interface. © 2022 Author(s).
    view abstractdoi: 10.1063/5.0085961
  • 2022 • 1217 Microstructure and residual stress evolution in nanocrystalline Cu-Zr thin films
    Chakraborty, J. and Oellers, T. and Raghavan, R. and Ludwig, A. and Dehm, G.
    Journal of Alloys and Compounds 896 (2022)
    Grazing incidence X-ray diffraction (GIXRD) and scanning transmission electron microscopy (STEM) combined with energy dispersive X-ray spectroscopy (EDS) were employed to study the microstructure evolution and stress development in the nanocrystalline Cu100−X-ZrX (2.5 at% ≤ x ≤ 5.5 at%) alloy thin films. Small Zr additions to Cu led to significant lattice parameter anisotropy in the as-deposited Cu-Zr thin films both due to macroscopic lattice strain and stacking faults in the Cu matrix. Strain free lattice parameters obtained after the XRD stress analysis of Cu-Zr thin films confirmed formation of a supersaturated substitutional Cu-Zr solid solution. For the first time, the study of film microstructure by XRD line profile analysis (XLPA) confirmed progressive generation of dislocations and planar faults with increasing Zr composition in Cu-Zr alloy films. These microstructural changes led to the generation of tensile stresses in the thin films along with considerable stress gradients across the films thicknesses which are quantified by the traditional dψhkl−Sin2ψ and GIXRD stress measurement methods. The origin of tensile stresses and stress gradients in the Cu-Zr film are discussed on the basis of film growth and heterogeneous microstructure with changing Zr composition. © 2021
    view abstractdoi: 10.1016/j.jallcom.2021.162799
  • 2022 • 1216 Diffusion chronometry of volcanic rocks: looking backward and forward
    Chakraborty, S. and Dohmen, R.
    Bulletin of Volcanology 84 (2022)
    doi: 10.1007/s00445-022-01565-5
  • 2022 • 1215 Adsorbate-Induced Modifications in the Optical Response of the Si(553)–Au Surface
    Chandola, S. and Sanna, S. and Hogan, C. and Speiser, E. and Plaickner, J. and Esser, N.
    Physica Status Solidi - Rapid Research Letters 16 (2022)
    doi: 10.1002/pssr.202200002
  • 2022 • 1214 Persister state-directed transitioning and vulnerability in melanoma
    Chauvistré, H. and Shannan, B. and Daignault-Mill, S.M. and Ju, R.J. and Picard, D. and Egetemaier, S. and Váraljai, R. and Gibhardt, C.S. and Sechi, A. and Kaschani, F. and Keminer, O. and Stehbens, S.J. and Liu, Q. and Yin, X....
    Nature Communications 13 (2022)
    Melanoma is a highly plastic tumor characterized by dynamic interconversion of different cell identities depending on the biological context. Melanoma cells with high expression of the H3K4 demethylase KDM5B (JARID1B) rest in a slow-cycling, yet reversible persister state. Over time, KDM5Bhigh cells can promote rapid tumor repopulation with equilibrated KDM5B expression heterogeneity. The cellular identity of KDM5Bhigh persister cells has not been studied so far, missing an important cell state-directed treatment opportunity in melanoma. Here, we have established a doxycycline-titratable system for genetic induction of permanent intratumor expression of KDM5B and screened for chemical agents that phenocopy this effect. Transcriptional profiling and cell functional assays confirmed that the dihydropyridine 2-phenoxyethyl 4-(2-fluorophenyl)-2,7,7-trimethyl-5-oxo-1,4,5,6,7,8-hexa-hydro-quinoline-3-carboxylate (termed Cpd1) supports high KDM5B expression and directs melanoma cells towards differentiation along the melanocytic lineage and to cell cycle-arrest. The high KDM5B state additionally prevents cell proliferation through negative regulation of cytokinetic abscission. Moreover, treatment with Cpd1 promoted the expression of the melanocyte-specific tyrosinase gene specifically sensitizing melanoma cells for the tyrosinase-processed antifolate prodrug 3-O-(3,4,5-trimethoxybenzoyl)-(–)-epicatechin (TMECG). In summary, our study provides proof-of-concept for a dual hit strategy in melanoma, in which persister state-directed transitioning limits tumor plasticity and primes melanoma cells towards lineage-specific elimination. © 2022, The Author(s).
    view abstractdoi: 10.1038/s41467-022-30641-9
  • 2022 • 1213 Feature extraction and neural network-based multi-peak analysis on time-correlated LiDAR histograms
    Chen, G. and Landmeyer, F. and Wiede, C. and Kokozinski, R.
    Journal of Optics (United Kingdom) 24 (2022)
    Time correlated single photon counting is a statistical method to generate time-correlated histograms (TC-Hists), which are based on the time-of-flight information measured by photon detectors such as single-photon avalanche diodes. With restricted measurements per histogram and the presence of high background light, it is challenging to obtain the target distance in a TC-Hist. In order to improve the data processing robustness under these conditions, the concept of machine learning is applied to the TC-Hist. Using the neural network-based multi-peak analysis (NNMPA), introduced by us, including a physics-guided feature extraction and a distance prediction process, the analysis is focused on a small number of critical features in the TC-Hist. Based on these features, possible target distances with correlated certainty values are inferred. Furthermore, two optimization approaches regarding learning ability and real-time performance are discussed. In particular, variants of the NNMPA are evaluated on both synthetic and real datasets. The proposed method not only has higher robustness in allocating the coarse position ( ±5% ) of the target distance in harsh conditions, but also is faster than the classical digital processing with an average-filter and noise suppression. Thus, it can be applied to improve the system robustness, especially in the case of high background light and middle-range detections. © 2022 The Author(s). Published by IOP Publishing Ltd.
    view abstractdoi: 10.1088/2040-8986/ac486d
  • 2022 • 1212 Improving the intermediate- and high-temperature strength of L12-Co3(Al,W) by Ni and Ta additions
    Chen, Z. and Kishida, K. and Inui, H. and Heilmaier, M. and Glatzel, U. and Eggeler, G.
    Acta Materialia 238 (2022)
    doi: 10.1016/j.actamat.2022.118224
  • 2022 • 1211 Spanning Fermi arcs in a two-dimensional magnet
    Chen, Y.-J. and Hanke, J.-P. and Hoffmann, M. and Bihlmayer, G. and Mokrousov, Y. and Blügel, S. and Schneider, C.M. and Tusche, C.
    Nature Communications 13 (2022)
    The discovery of topological states of matter has led to a revolution in materials research. When external or intrinsic parameters break symmetries, global properties of topological materials change drastically. A paramount example is the emergence of Weyl nodes under broken inversion symmetry. While a rich variety of non-trivial quantum phases could in principle also originate from broken time-reversal symmetry, realizing systems that combine magnetism with complex topological properties is remarkably elusive. Here, we demonstrate that giant open Fermi arcs are created at the surface of ultrathin hybrid magnets where the Fermi-surface topology is substantially modified by hybridization with a heavy-metal substrate. The interplay between magnetism and topology allows us to control the shape and the location of the Fermi arcs by tuning the magnetization direction. The hybridization points in the Fermi surface can be attributed to a non-trivial mixed topology and induce hot-spots in the Berry curvature, dominating spin and charge transport as well as magneto-electric coupling effects. © 2022, The Author(s).
    view abstractdoi: 10.1038/s41467-022-32948-z
  • 2022 • 1210 Electrocaloric cooling - From materials to devices
    Chen, X. and Shvartsman, V.V. and Lupascu, D.C. and Zhang, Q.M.
    Journal of Applied Physics 132 (2022)
    doi: 10.1063/5.0132533
  • 2022 • 1209 Transient THz Emission and Effective Mass Determination in Highly Resistive GaAs Crystals Excited by Femtosecond Optical Pulses
    Chen, G. and Chakraborty, D. and Cheng, J. and Mikulics, M. and Komissarov, I. and Adam, R. and Bürgler, D.E. and Schneider, C.M. and Hardtdegen, H. and Sobolewski, R.
    Crystals 12 (2022)
    doi: 10.3390/cryst12111635
  • 2022 • 1208 Out-of-plane longitudinal sound velocity in SnS2determined via broadband time-domain Brillouin scattering
    Cheng, M. and Pichugin, K. and Maas, A. and Schleberger, M. and Sciaini, G.
    Journal of Applied Physics 132 (2022)
    Here, we report time-resolved broadband transient reflectivity measurements performed in a single crystal of SnS2. We made use of time-domain Brillouin scattering and a broadband probe to measure the out-of-plane longitudinal sound velocity, υ L = (2950 ± 100) m s - 1, in this semiconducting two-dimensional metal dichalcogenide. Our study illustrates the potential of this non-invasive all-optical pump-probe technique for the study of the elastic properties of transparent brittle materials and provides the value of the elastic constant c 33 = (39 ± 3) GPa. © 2022 Author(s).
    view abstractdoi: 10.1063/5.0103224
  • 2022 • 1207 Theory of inertial spin dynamics in anisotropic ferromagnets
    Cherkasskii, M. and Barsukov, I. and Mondal, R. and Farle, M. and Semisalova, A.
    Physical Review B 106 (2022)
    doi: 10.1103/PhysRevB.106.054428
  • 2022 • 1206 On the Tunability of Mode Locked Laser Diodes for Use as Local Oscillators in Photonic Terahertz Systems
    Cherniak, V. and Zander, M. and Moehrle, M. and Rehbein, W. and Brenner, C. and Hofmann, M. and Balzer, J.C.
    International Conference on Infrared, Millimeter, and Terahertz Waves, IRMMW-THz 2022-August (2022)
    doi: 10.1109/IRMMW-THz50927.2022.9895884
  • 2022 • 1205 A Study of the Usability of Monolithically Integrated Photonic Oscillators for Wireless Millimeter Wave and Terahertz Communication
    Cherniak, V. and Endemann, W. and Frischkorn, B. and Kleemann, N. and Brenner, C. and Hofmann, M. and Balzer, J.C.
    International Conference on Infrared, Millimeter, and Terahertz Waves, IRMMW-THz 2022-August (2022)
    doi: 10.1109/IRMMW-THz50927.2022.9895519
  • 2022 • 1204 A comprehensive study of the structure and piezoelectric response of biodegradable polyhydroxybutyrate-based films for tissue engineering applications
    Chernozem, R.V. and Pariy, I.O. and Pryadko, A. and Bonartsev, A.P. and Voinova, V.V. and Zhuikov, V.A. and Makhina, T.K. and Bonartseva, G.A. and Shaitan, K.V. and Shvartsman, V.V. and Lupascu, D.C. and Romanyuk, K.N. and Kholkin...
    Polymer Journal 54 1225-1236 (2022)
    The results of comprehensive research on the thermal behavior and molecular and crystalline structures of poly(3-hydroxybutyrate) (PHB) and poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHB-HV) films of different thicknesses, their molecular weights (Mw) and 3-hydroxyvalerate (3-HV) contents are reported. Increasing film thickness from 30 to 100 µm resulted in an isotropic crystal orientation, reducing the crystallite size of the orthorhombic α-phase in the b direction from 22 to 17 nm and increasing the degree of crystallinity of the PHB films without affecting their thermal behavior. Furthermore, despite resulting in the same degree of crystallinity and roughness, an ~8-fold decrease in PHB Mw from 803 kDa to 102 kDa resulted in a decreased number of piezoactive domains. The addition of 5.9% 3-HV resulted in anisotropy in the PHB crystalline structure and increased D(020) from 19 nm to 24 nm. Additionally, a further increase in the 3-HV content to 17.5% in the PHB-HV films led to a decrease in the melting temperature and a decrease in the degree of crystallinity from 57% to 23%, which resulted in the absence of local piezoresponse. Notably, the decrease in the Mw of PHB-HV (~17%) from 1177 kDa to 756 kDa resulted in an increase in the degree of crystallinity from 23% to 32%. Moreover, the PHB-HV films became smoother with increasing 3-HV content. © 2022, The Author(s), under exclusive licence to The Society of Polymer Science, Japan.
    view abstractdoi: 10.1038/s41428-022-00662-8
  • 2022 • 1203 Inhibition of Src but not Syk causes weak reversal of GPVI-mediated platelet aggregation measured by light transmission aggregometry
    Cheung, H.Y.F. and Moran, L.A. and Sickmann, A. and Heemskerk, J.W.M. and Garcia, Á. and Watson, S.P.
    Platelets 33 1293-1300 (2022)
    Src tyrosine kinases and spleen tyrosine kinase (Syk) have recently been shown to contribute to sustained platelet aggregation on collagen under arterial shear. In the present study, we have investigated whether Src and Syk are required for aggregation under minimal shear following activation of glycoprotein VI (GPVI) and have extended this to C-type lectin-like receptor-2 (CLEC-2) which signals through the same pathway. Aggregation was induced by the GPVI ligand collagen-related peptide (CRP) and the CLEC-2 ligand rhodocytin and monitored by light transmission aggregometry (LTA). Aggregation and tyrosine phosphorylation by both receptors were sustained for up to 50 min. The addition of inhibitors of Src, Syk or Bruton’s tyrosine kinase (Btk) at 150 sec, by which time aggregation was maximal, induced rapid loss of tyrosine phosphorylation of their downstream proteins, but only Src kinase inhibition caused a weak (~10%) reversal in light transmission. A similar effect was observed when the inhibitors were combined with apyrase and indomethacin or glycoprotein IIb-IIIa (GPIIb-IIIa) antagonist, eptifibatide. On the other hand, activation of GPIIb-IIIa by GPVI in a diluted platelet suspension, as measured by binding of fluorescein isothiocyanate-labeled antibody specific for the activated GPIIb-IIIa (FITC-PAC1), was reversed on the addition of Src and Syk inhibitors showing that integrin activation is rapidly reversible in the absence of outside-in signals. The results demonstrate that Src but not Syk and Btk contribute to sustained aggregation as monitored by LTA, possibly as a result of inhibition of outside-in signaling from GPIIb-IIIa to the cytoskeleton through a Syk-independent pathway. This is in contrast to the role of Syk in supporting sustained aggregation on collagen under arterial shear. © 2022 The Author(s). Published with license by Taylor & Francis Group, LLC.
    view abstractdoi: 10.1080/09537104.2022.2069235
  • 2022 • 1202 Viscous effects on squat
    Chillcce, G. and el Moctar, O.
    Applied Ocean Research 125 (2022)
    doi: 10.1016/j.apor.2022.103252
  • 2022 • 1201 Probabilistic-based fatigue reliability assessment of carbon steel coil spring from random strain loading excitation
    Chin, C.H. and Abdullah, S. and Singh, S.S.K. and Ariffin, A.K. and Schramm, D.
    Journal of Mechanical Science and Technology 36 109-118 (2022)
    This paper aims to assess the fatigue reliability of random loading signals of a suspension coil spring using probabilistic approaches. Strain time histories were acquired while the car was travelling on different road conditions (i.e., in a rural area, in an industrial area, on a university campus, on a highway and on a newly constructed road). Fatigue lives were predicted from the strain histories and fitted into probability density functions. Lognormal distribution was found to be an appropriate way to represent fatigue data. Next, the reliability function and mean-cycles-to-failure (MCTF) were determined. The results indicated that fatigue reliability rapidly deteriorated under rural road conditions, which resulted in a short MCTF of 104 cycles. Meanwhile, the new road signals had the longest MCTF of about 108 cycles. Accordingly, this is due to the rural road having the most surface irregularities, which caused more severe fatigue damage to the coil spring. This study contributed to a greater in-depth understanding of the effect of loading signals on fatigue reliability. This is essential in determining the appropriate service life of the coil spring during its production to ensure vehicle safety and reduce maintenance costs. © 2021, The Korean Society of Mechanical Engineers and Springer-Verlag GmbH Germany, part of Springer Nature.
    view abstractdoi: 10.1007/s12206-021-1209-5
  • 2022 • 1200 Phase transformations and microstructure evolution during combustion of iron powder
    Choisez, L. and van Rooij, N.E. and Hessels, C.J.M. and da Silva, A.K. and Filho, I.R.S. and Ma, Y. and de Goey, P. and Springer, H. and Raabe, D.
    Acta Materialia 239 (2022)
    To successfully transition from fossil-fuel to sustainable carbon-free energy carriers, a safe, stable and high-density energy storage technology is required. The combustion of iron powders seems very promising in this regard. Yet, little is known about their in-process morphological and microstructural evolution, which are critical features for the circularity of the concept, especially the subsequent reduction of the combusted oxide powders back to iron. Here, we investigated two iron powder combustion pathways, one in air and one with the assistance of a propane pilot flame. Both processes resulted in spherical hollow particles composed of a complex microstructure of wüstite, magnetite and/or hematite. Partial evaporation is indicated by the observation of nanoparticles on the micro-sized combustion products. The associated gas production inside the liquid droplet could be the origin of the internal porosity and micro-explosion events. Cracking at the end of the combustion process results in mostly open porosity, which is favorable for the subsequent reduction process. With this study, we aim to open the perspective of iron metal fuel from macroscopic combustion analysis towards a better understanding of the underlying microscopic thermodynamic, kinetic, microstructural and thermomechanical mechanisms. © 2022 Acta Materialia Inc.
    view abstractdoi: 10.1016/j.actamat.2022.118261
  • 2022 • 1199 Strong Stationarity for Optimal Control of Variational Inequalities of the Second Kind
    Christof, C. and Meyer, C. and Schweizer, B. and Turek, S.
    International Series of Numerical Mathematics 172 307-327 (2022)
    This chapter is concerned with necessary optimality conditions for optimal control problems governed by variational inequalities of the second kind. The so-called strong stationarity conditions are derived in an abstract framework. Strong stationarity conditions are regarded as the most rigorous ones, since they imply all other types of stationarity concepts and are equivalent to purely primal optimality conditions. The abstract framework is afterward applied to four application-driven examples. © 2022, Springer Nature Switzerland AG.
    view abstractdoi: 10.1007/978-3-030-79393-7_12
  • 2022 • 1198 Model-free data-driven simulation of inelastic materials using structured data sets, tangent space information and transition rules
    Ciftci, K. and Hackl, K.
    Computational Mechanics 70 425-435 (2022)
    doi: 10.1007/s00466-022-02174-x
  • 2022 • 1197 Monolithic n+-InGaAs Thin Film Resistor from DC up to 0.5 THz
    Clochiatti, S. and Yavari, P. and Schmidt, R. and Hauser, P. and Mutlu, E. and Preus, C. and Prost, W. and Weimann, N.
    2022 5th International Workshop on Mobile Terahertz Systems, IWMTS 2022 (2022)
    We report on the design, fabrication, and characterization of a monolithically integrated epitaxial thin-film resistor for THz applications. The device is made of an n+-InGaAs layer grown lattice-matched on an insulating InP:Fe substrate. In this study, on-wafer vector scattering parameter characterization up to 500 GHz is carried out, the calibration is performed by means of the multiline TRL method. The InGaAs thin-film resistor shows very flat frequency response in the range from 100 GHz to 500 GHz. An experiment designed to investigate the resistor's temperature dependence and stability up to 120 °C has also been carried out. © 2022 IEEE.
    view abstractdoi: 10.1109/IWMTS54901.2022.9832445
  • 2022 • 1196 On-Wafer Characterization and Modelling of InP Resonant Tunnelling Diodes up to 500 GHz
    Clochiatti, S. and Schmidt, R. and Mutlu, E. and Dieudonne, M. and Prost, W. and Schreurs, D. and Weimann, N.
    2022 52nd European Microwave Conference, EuMC 2022 282-285 (2022)
    doi: 10.23919/EuMC54642.2022.9924370
  • 2022 • 1195 Distortion-driven spin switching in electron-doped metal porphyrins
    Cojocariu, I. and Carlotto, S. and Jugovac, M. and Floreano, L. and Casarin, M. and Feyer, V. and Schneider, C.M.
    Journal of Materials Chemistry C 10 9748-9757 (2022)
    Electron injection into electrode-supported metal complexes allows for charge redistribution within the molecule to be controlled. Here we show, for the first time, how the structural flexibility in electron-doped porphyrins is critical in defining charge localization by following the evolution of the spin state and charge distribution in the thermodynamically favored structure as a function of dopant dose and relaxation time. Two flexible transition metal-containing molecules are used as model systems, nickel and cobalt tetraphenylporphyrin, studied by combining a wide range of spectroscopic techniques with detailed DFT calculations. © 2022 The Royal Society of Chemistry.
    view abstractdoi: 10.1039/d2tc01253g
  • 2022 • 1194 Semiconductor Halogenation in Molecular Highly-Oriented Layered p–n (n–p) Junctions
    Cojocariu, I. and Jugovac, M. and Sarwar, S. and Rawson, J. and Sanz, S. and Kögerler, P. and Feyer, V. and Schneider, C.M.
    Advanced Functional Materials (2022)
    Organic p–n junctions attract widespread interest in the field of molecular electronics because of their unique optoelectronic singularities. Importantly, the molecular donor/acceptor character is strongly correlated to the degree of substitution, e.g., the introduction of electron-withdrawing groups. Herein, by gradually increasing the degree of peripheral fluorination on planar, D4h−symmetric iron(II) phthalocyanato (FePc) complexes, the energy level alignment and molecular order is defined in a metal-supported bilayered Pc-based junction using photoemission orbital tomography. This non-destructive method selectively allows identifying molecular levels of the hetero-architectures. It demonstrates that, while the symmetric fluorination of FePc does not disrupt the long-range order and degree of metal-to-molecule charge transfer in the first molecular layer, it strongly impacts the energy alignment in both the interface and topmost layer in the bilayered structures. The p–n junction formed in the bilayer of perhydrogenated FePc and perfluorinated FeF16Pc may serve as an ideal model for understanding the basic charge-transport phenomena at the metal-supported organic–organic interfaces, with possible application in photovoltaic devices. © 2022 The Authors. Advanced Functional Materials published by Wiley-VCH GmbH.
    view abstractdoi: 10.1002/adfm.202208507
  • 2022 • 1193 Large strain flow curve identification for sheet metal
    Coppieters, S. and Traphöner, H. and Stiebert, F. and Balan, T. and Kuwabara, T. and Tekkaya, A.E.
    Journal of Materials Processing Technology 308 (2022)
    doi: 10.1016/j.jmatprotec.2022.117725
  • 2022 • 1192 Biocatalyst and continuous microfluidic reactor for an intensified production of n-butyl levulinate: Kinetic model assessment
    Cordier, A. and Klinksiek, M. and Held, C. and Legros, J. and Leveneur, S.
    Chemical Engineering Journal 451 (2022)
    doi: 10.1016/j.cej.2022.138541
  • 2022 • 1191 Experimental characterization techniques for plasmon-assisted chemistry
    Cortés, E. and Grzeschik, R. and Maier, S.A. and Schlücker, S.
    Nature Reviews Chemistry 6 259-274 (2022)
    Plasmon-assisted chemistry is the result of a complex interplay between electromagnetic near fields, heat and charge transfer on the nanoscale. The disentanglement of their roles is non-trivial. Therefore, a thorough knowledge of the chemical, structural and spectral properties of the plasmonic/molecular system being used is required. Specific techniques are needed to fully characterize optical near fields, temperature and hot carriers with spatial, energetic and/or temporal resolution. The timescales for all relevant physical and chemical processes can range from a few femtoseconds to milliseconds, which necessitates the use of time-resolved techniques for monitoring the underlying dynamics. In this Review, we focus on experimental techniques to tackle these challenges. We further outline the difficulties when going from the ensemble level to single-particle measurements. Finally, a thorough understanding of plasmon-assisted chemistry also requires a substantial joint experimental and theoretical effort. [Figure not available: see fulltext.] © 2022, Springer Nature Limited.
    view abstractdoi: 10.1038/s41570-022-00368-8
  • 2022 • 1190 Differential Tafel Analysis: A Quick and Robust Tool to Inspect and Benchmark Charge Transfer in Electrocatalysis
    Corva, M. and Blanc, N. and Bondue, C.J. and Tschulik, K.
    ACS Catalysis 13805-13812 (2022)
    doi: 10.1021/acscatal.2c03581
  • 2022 • 1189 Three-dimensional detonation structure and its response to confinement
    Crane, J. and Lipkowicz, J.T. and Shi, X. and Wlokas, I. and Kempf, A.M. and Wang, H.
    Proceedings of the Combustion Institute (2022)
    doi: 10.1016/j.proci.2022.10.019
  • 2022 • 1188 Effective decoupling of ferromagnetic sublattices by frustration in Heusler alloys
    Cugini, F. and Chicco, S. and Orlandi, F. and Allodi, G. and Bonfá, P. and Vezzoni, V. and Miroshkina, O.N. and Gruner, M.E. and Righi, L. and Fabbrici, S. and Albertini, F. and De Renzi, R. and Solzi, M.
    Physical Review B 105 (2022)
    doi: 10.1103/PhysRevB.105.174434
  • 2022 • 1187 Laser Additive Manufacturing of Duplex Stainless Steel via Powder Mixture
    Cui, C. and Becker, L. and Gärtner, E. and Boes, J. and Lentz, J. and Uhlenwinkel, V. and Steinbacher, M. and Weber, S. and Fechte-Heinen, R.
    Journal of Manufacturing and Materials Processing 6 (2022)
    Laser additively manufactured duplex stainless steels contain mostly ferrite in the as-built parts due to rapid solidification of the printed layers. To achieve duplex microstructures (ferrite and austenite in roughly equal proportions) and, thus, a good combination of mechanical properties and corrosion resistance, an austenitic stainless steel powder (X2CrNiMo17-12-2) and a super duplex stainless steel powder (X2CrNiMoN25-7-4) were mixed in different proportions and the powder mixtures were processed via PBF-LB/M (Laser Powder Bed Fusion) under various processing conditions by varying the laser power and the laser scanning speed. The optimal process parameters for dense as-built parts were determined by means of light optical microscopy and density measurements. The austenitic and ferritic phase formation of the mixed alloys was significantly influenced by the chemical composition adjusted by powder mixing and the laser energy input during PBF-LB/M. The austenite content increases, on the one hand, with an increasing proportion of X2CrNiMo17-12-2 in the powder mixtures and on the other hand with increasing laser energy input. The latter phenomenon could be attributed to a slower solidification and a higher melt pool homogeneity with increasing energy input influencing the phase formation during solidification and cooling. The desired duplex microstructures could be achieved by mixing the X2CrNiMo17-12-2 powder and the X2CrNiMoN25-7-4 powder at a specific mixing ratio and building with the optimal PBF-LB/M parameters. © 2022 by the authors. Licensee MDPI, Basel, Switzerland.
    view abstractdoi: 10.3390/jmmp6040072
  • 2022 • 1186 Analytical model of the in-plane torsion test
    Cwiekala, N. and Traphöner, H. and Haupt, P. and Clausmeyer, T. and Tekkaya, A.E.
    Acta Mechanica 233 641-663 (2022)
    In research and industry, the in-plane torsion test is applied to investigate the material behaviour at large plastic strains: a sheet is clamped in two concentric circles, the boundaries are twisted against each other applying a torque, and simple shear of the material arises. This deformation is analysed within the scope of finite elasto-plasticity. An additive decomposition of the Almansi strain tensor is derived, valid as an approximation for arbitrary large plastic strains and sufficiently small elastic strains and rotations. Constitutive assumptions are the von Mises yield criterion, an associative flow rule, isotropic hardening, and a physically linear elasticity relation. The incremental formulation of the elasticity relation applies covariant Oldroyd derivatives of the stress and the strain tensors. The assumptions combined with equilibrium conditions lead to evolution equations for the distribution of stresses and accumulated plastic strain. The nonzero circumferential stress must be determined from the equilibrium condition because no deformation is present in tangential direction. As a result, a differential-algebraic-equation (DAE) system is derived, consisting of three ordinary differential equations combined with one algebraic side condition. As an example material, properties of a dual phase steel DP600 are analysed numerically at an accumulated plastic strain of 3.0. Radial normal stresses of 3.1% and tangential normal stresses of 1.0% of the shear stresses are determined. The influence of the additional normal stresses on the determination of the flow curve is 0.024%, which is negligibly small in comparison with other experimental influences and measurement accuracies affecting the experimental flow curve determination. © 2022, The Author(s).
    view abstractdoi: 10.1007/s00707-021-03129-8
  • 2022 • 1185 Selective Anodic Oxidation of Solketal as Acetal-Protected Glycerol over Nickel Boride in Alkaline Media to Glyceric Acid**
    Cychy, S. and Lechler, S. and Muhler, M.
    ChemElectroChem 9 (2022)
    Alkaline anodic oxidation of glycerol suffers from facile C−C bond cleavage, especially when using non-precious metal electrocatalysts, which limits the yield of more valuable C3 oxygenates. Usually, a high C3 selectivity is a tradeoff with conversion for most catalysts. Thus, we used solketal as the reactant, which is acetal-protected glycerol with acetone. CV experiments showed that solketal is oxidized over nickel boride (NixB) at potentials where NiOOH is formed. Electrolysis over NixB in a thin-film spectroelectrochemical flow cell at 1.58 V vs. RHE to avoid pronounced oxygen evolution showed a stable current density of ca. 6 mA cm−2. Simultaneously recorded ATR-FTIR spectra revealed solketal conversion to solketalate and formate. Indeed, 59 % conversion and 77 % selectivity to glyceric acid were determined by HPLC after acidic cleavage of the acetal, resulting in a yield of 45 %. Therefore, solketal is a promising reactant for the selective electrosynthesis of glyceric acid. © 2021 The Authors. ChemElectroChem published by Wiley-VCH GmbH.
    view abstractdoi: 10.1002/celc.202101214
  • 2022 • 1184 Charge and spin supercurrents in magnetic Josephson junctions with spin filters and domain walls
    Dahir, S.M. and Volkov, A.F. and Eremin, I.M.
    Physical Review B 105 (2022)
    doi: 10.1103/PhysRevB.105.094517
  • 2022 • 1183 Evaluation of Range Doppler Processing Algorithms for Tank Level Probing Radar
    Dahl, C. and Hammes, M. and Vogt, M. and Schulz, C. and Rolfes, I.
    2022 German Microwave Conference, GeMiC 2022 37-40 (2022)
    In this contribution, the performance of different algorithms for range Doppler processing are compared and discussed for application in tank level probing radar. Algorithms using the fast Fourier transform and the keystone transform have been evaluated by simulations and measurements regarding the accuracy and the reliability of measuring the filling level of a liquid inside a tank. In addition the impact of waves on the surface of the liquid has been investigated. It is shown, that the keystone transform is capable to improve the performance of measurements in tank level scenarios. © 2022 IMA.
    view abstract
  • 2022 • 1182 A Pure and Indistinguishable Single-Photon Source at Telecommunication Wavelength
    Da Lio, B. and Faurby, C. and Zhou, X. and Chan, M.L. and Uppu, R. and Thyrrestrup, H. and Scholz, S. and Wieck, A.D. and Ludwig, Ar. and Lodahl, P. and Midolo, L.
    Advanced Quantum Technologies 5 (2022)
    On-demand single-photon sources emitting pure and indistinguishable photons at the telecommunication wavelength are critical assets toward the deployment of fiber-based quantum networks. Indeed, single photons may serve as flying qubits, allowing communication of quantum information over long distances. Self-assembled InAs quantum dots embedded in GaAs constitute an excellent nearly deterministic source of high-quality single photons, but the vast majority of sources operate in the 900–950 nm wavelength range, precluding their adoption in a quantum network. A quantum frequency conversion scheme is presented here for converting single photons from quantum dots to the telecommunication C band, around 1550 nm, achieving 40.8% end-to-end efficiency, while maintaining both high purity and a high degree of indistinguishability during conversion with measured values of (Formula presented.) and (Formula presented.), respectively. © 2022 The Authors. Advanced Quantum Technologies published by Wiley-VCH GmbH.
    view abstractdoi: 10.1002/qute.202200006
  • 2022 • 1181 Covalent coupling of HIV-1 glycoprotein trimers to biodegradable calcium phosphate nanoparticles via genetically encoded aldehyde-tags
    Damm, D. and Kostka, K. and Weingärtner, C. and Wagner, J.T. and Rojas-Sánchez, L. and Gensberger-Reigl, S. and Sokolova, V. and Überla, K. and Epple, M. and Temchura, V.
    Acta Biomaterialia 140 586-600 (2022)
    doi: 10.1016/j.actbio.2021.12.022
  • 2022 • 1180 Mechanical and hydrodynamic characteristics of emerged porous Gyroid breakwaters based on triply periodic minimal surfaces
    Dang, B.-L. and Nguyen-Van, V. and Tran, P. and Wahab, M.A. and Lee, J. and Hackl, K. and Nguyen-Xuan, H.
    Ocean Engineering 254 (2022)
    doi: 10.1016/j.oceaneng.2022.111392
  • 2022 • 1179 Temperature dependence of the local electromagnetic field at the Fe site in multiferroic bismuth ferrite
    Dang, T.T. and Schell, J. and Boa, A.G. and Lewin, D. and Marschick, G. and Dubey, A. and Escobar-Castillo, M. and Noll, C. and Beck, R. and Zyabkin, D.V. and Glukhov, K. and Yap, I.C.J. and Mokhles Gerami, A. and Lupascu, D.C.
    Physical Review B 106 (2022)
    In this paper, we present a study of the temperature-dependent characteristics of electromagnetic fields at the atomic scale in multiferroic bismuth ferrite (BiFeO3 or BFO). The study was performed using time differential perturbed angular correlation (TDPAC) spectroscopy on implanted In111 (Cd111) probes over a wide temperature range. The TDPAC spectra show that substitutional In111 on the Fe3+ site experiences local electric polarization, which is otherwise expected to essentially stem from the Bi3+ lone pair electrons. Moreover, the TDPAC spectra show combined electric and magnetic interactions below the Néel temperature TN. This is consistent with simulated spectra. X-ray diffraction (XRD) was employed to investigate how high-temperature TDPAC measurements influence the macroscopic structure and secondary phases. With the support of ab initio DFT simulations, we can discuss the probe nucleus site assignment and can conclude that the In111 (Cd111) probe substitutes the Fe atom at the B site of the perovskite structure. © 2022 authors. Published by the American Physical Society.
    view abstractdoi: 10.1103/PhysRevB.106.054416
  • 2022 • 1178 The Local Exploration of Magnetic Field Effects in Semiconductors
    Dang, T.T. and Schell, J. and Beck, R. and Noll, C. and Lupascu, D.C.
    Crystals 12 (2022)
    This study reports on the local exploration of magnetic field effects in semiconductors, including silicon (Si), germanium (Ge), gallium arsenide (GaAs), and indium phosphide (InP) using the time differential perturbed angular correlation (TDPAC) technique. TDPAC measurements were carried out under external magnetic fields with strengths of 0.48 T and 2.1 T at room temperature, and 77 K following the implantation of111 In (111 Cd) probes. Defects caused by ion implantation could be easily removed by thermal annealing at an appropriate temperature. The agreement between the measured Larmor frequencies and the theoretical values confirms that almost no intrinsic point defects are present in the semiconductors. At low temperatures, an electric interaction sets in. It stems from the electron capture after-effect. In the case of germanium and silicon, this effect is well visible. It is associated with a double charge state of the defect ion. No such effects arise in GaAs and InP where Cd contributes only a single electronic defect state. The Larmor frequencies correspond to the external magnetic field also at low temperatures. © 2022 by the authors. Licensee MDPI, Basel, Switzerland.
    view abstractdoi: 10.3390/cryst12040560
  • 2022 • 1177 Hybrid additive manufacturing of metal laminated forming tools
    Dardaei Joghan, H. and Hahn, M. and Sehrt, J.T. and Tekkaya, A.E., (1)
    CIRP Annals 71 225-228 (2022)
    Deep drawing dies are manufactured using metal sheets. Laser metal deposition is used for bonding the sheets and smoothening the edges. The strength and surface finish of the dies are the key challenges. Milling, roller burnishing, and laser treatment are applied as post-processing for improving the surface finish. A semi-analytical model is developed for selecting the sheet combination for sufficient strength. The new rapid prototyping process offers high flexibility for complex die geometries. The evaluation by deep drawing experiments using DC06 and high-strength HC380LA blanks revealed the feasibility of the new manufacturing routes regarding deep drawability and surface finish. © 2022 CIRP
    view abstractdoi: 10.1016/j.cirp.2022.03.018
  • 2022 • 1176 X-ray scattering at beamline BL2 of DELTA: Studies of lysozyme-lysozyme interaction in heavy water and structure formation in 1-hexanol
    Dargasz, M. and Bolle, J. and Faulstich, A. and Schneider, E. and Kowalski, M. and Sternemann, C. and Savelkouls, J. and Murphy, B. and Paulus, M.
    Journal of Physics: Conference Series 2380 (2022)
    doi: 10.1088/1742-6596/2380/1/012031
  • 2022 • 1175 Coupled Cluster Molecular Dynamics of Condensed Phase Systems Enabled by Machine Learning Potentials: Liquid Water Benchmark
    Daru, J. and Forbert, H. and Behler, J. and Marx, D.
    Physical Review Letters 129 (2022)
    Coupled cluster theory is a general and systematic electronic structure method, but in particular the highly accurate "gold standard"coupled cluster singles, doubles and perturbative triples, CCSD(T), can only be applied to small systems. To overcome this limitation, we introduce a framework to transfer CCSD(T) accuracy of finite molecular clusters to extended condensed phase systems using a high-dimensional neural network potential. This approach, which is automated, allows one to perform high-quality coupled cluster molecular dynamics, CCMD, as we demonstrate for liquid water including nuclear quantum effects. The machine learning strategy is very efficient, generic, can be systematically improved, and is applicable to a variety of complex systems. © 2022 American Physical Society.
    view abstractdoi: 10.1103/PhysRevLett.129.226001
  • 2022 • 1174 Elastic energy of multi-component solid solutions and strain origins of phase stability in high-entropy alloys
    Darvishi Kamachali, R. and Wang, L.
    Scripta Materialia 206 (2022)
    The elastic energy of mixing for multi-component solid solutions is derived by generalizing Eshelby's sphere-in-hole model. By surveying the dependence of the elastic energy on the chemical composition and lattice misfit, we derive a lattice strain coefficient λ*. Studying several high-entropy alloys and superalloys, we propose that most solid solution multi-component alloys are stable when λ*&lt;0.16, generalizing the Hume-Rothery atomic-size rule for binary alloys. We also reveal that the polydispersity index δ, frequently used for describing strain in multi-component alloys, directly represents the elastic energy (e) with e=qδ2, q being an elastic constant. Furthermore, the effects of (i) the number and (ii) the atomic-size distribution of constituting elements on the phase stability of high-entropy alloys were quantified. The present derivations and discussions open for richer considerations of elastic effects in high-entropy alloys, offering immediate support for quantitative assessments of their thermodynamic properties and studying related strengthening mechanisms. © 2021
    view abstractdoi: 10.1016/j.scriptamat.2021.114226
  • 2022 • 1173 Effect of Doping, Photodoping, and Bandgap Variation on the Performance of Perovskite Solar Cells
    Das, B. and Aguilera, I. and Rau, U. and Kirchartz, T.
    Advanced Optical Materials 10 (2022)
    Most traditional semiconductor materials are based on the control of doping densities to create junctions and thereby functional and efficient electronic and optoelectronic devices. The technology development for halide perovskites had initially only rarely made use of the concept of electronic doping of the perovskite layer and instead employed a variety of different contact materials to create functionality. Only recently, intentional or unintentional doping of the perovskite layer is more frequently invoked as an important factor explaining differences in photovoltaic or optoelectronic performance in certain devices. Here, numerical simulations are used to study the influence of doping and photodoping on photoluminescence quantum yield and other device relevant metrics. It is found that doping can improve the photoluminescence quantum yield by making radiative recombination faster. This effect can benefit, or harm, photovoltaic performance given that the improvement of photoluminescence quantum efficiency and open-circuit voltage is accompanied by a reduction of the diffusion length. This reduction will eventually lead to inefficient carrier collection at high doping densities. The photovoltaic performance may improve at an optimum doping density which depends on a range of factors such as the mobilities of the different layers and the ratio of the charge carrier capture cross sections. © 2022 The Authors. Advanced Optical Materials published by Wiley-VCH GmbH.
    view abstractdoi: 10.1002/adom.202101947
  • 2022 • 1172 Recent Advances in Understanding Diffusion in Multiprincipal Element Systems
    Dash, A. and Paul, A. and Sen, S. and Divinski, S. and Kundin, J. and Steinbach, I. and Grabowski, B. and Zhang, X.
    Annual Review of Materials Research 52 383-409 (2022)
    Recent advances in the field of diffusion in multiprincipal element systems are critically reviewed, with an emphasis on experimental as well as theoretical approaches to determining atomic mobilities (tracer diffusion coefficients) in chemically complex multicomponent systems. The newly elaborated and augmented pseudobinary and pseudoternary methods provide a rigorous framework to access tracer, intrinsic, and interdiffusion coefficients in alloys with an arbitrary number of components. Utilization of the novel tracer-interdiffusion couple method allows for a high-throughput determination of composition-dependent tracer diffusion coefficients. A combination of these approaches provides a unique experimental toolbox to access diffusivities of elements that do not have suitable tracers. The pair-exchange diffusion model, which gives a consistent definition of diffusion matrices without specifying a reference element, is highlighted. Density-functional theory-informed calculations of basic diffusion properties mdash asrequired for the generation of extensive mobility databases for technological applications mdash are also discussed. © 2022 Annual Reviews Inc.. All rights reserved.
    view abstractdoi: 10.1146/annurev-matsci-081720-092213
  • 2022 • 1171 Membrane Structure Obtained in an Experimental Evolution Process
    Dávila, M.J. and Mayer, C.
    Life 12 (2022)
    Recently, an evolution experiment was carried out in a cyclic process, which involved periodic vesicle formation in combination with peptide and vesicle selection. As an outcome, an octapeptide (KSPFPFAA) was identified which rapidly integrated into the vesicle membrane and, according to its significant accumulation, is obviously connected to a particular advantage of the corresponding functionalized vesicle. Here we report a molecular dynamics study of the structural details of the functionalized vesicle membrane, which was a product of this evolution process and is connected to several survival mechanisms. In order to elucidate the particular advantage of this structure, we performed all-atom molecular dynamics simulations to examine structural changes and interactions of the peptide (KSPFPFAA) with the given octadecanoic acid/octadecylamine (1:1) bilayer under acidic conditions. The calculations clearly demonstrate the specific interactions between the peptide and the membrane and reveal the mechanisms leading to the improved vesicle survival. © 2022 by the authors. Licensee MDPI, Basel, Switzerland.
    view abstractdoi: 10.3390/life12020145
  • 2022 • 1170 Surface and Bulk Chemistry of Mechanochemically Synthesized Tohdite Nanoparticles
    De Bellis, J. and Ochoa-Hernández, C. and Farès, C. and Petersen, H. and Ternieden, J. and Weidenthaler, C. and Amrute, A.P. and Schüth, F.
    Journal of the American Chemical Society 144 9421-9433 (2022)
    Aluminum oxides, oxyhydroxides, and hydroxides are important in different fields of application due to their many attractive properties. However, among these materials, tohdite (5Al2O3·H2O) is probably the least known because of the harsh conditions required for its synthesis. Herein, we report a straightforward methodology to synthesize tohdite nanopowders (particle diameter ∼13 nm, specific surface area ∼102 m2g-1) via the mechanochemically induced dehydration of boehmite (γ-AlOOH). High tohdite content (about 80%) is achieved upon mild ball milling (400 rpm for 48 h in a planetary ball mill) without process control agents. The addition of AlF3can promote the crystallization of tohdite by preventing the formation of the most stable α-Al2O3, resulting in the formation of almost phase-pure tohdite. The availability of easily accessible tohdite samples allowed comprehensive characterization by powder X-ray diffraction, total scattering analysis, solid-state NMR (1H and 27Al), N2-sorption, electron microscopy, and simultaneous thermal analysis (TG-DSC). Thermal stability evaluation of the samples combined with structural characterization evidenced a low-temperature transformation sequence: 5Al2O3·H2O → κ-Al2O3→ α-Al2O3. Surface characterization via DRIFTS, ATR-FTIR, D/H exchange experiments, pyridine-FTIR, and NH3-TPD provided further insights into the material properties. © 2022 American Chemical Society. All rights reserved.
    view abstractdoi: 10.1021/jacs.2c02181
  • 2022 • 1169 Direct Dry Synthesis of Supported Bimetallic Catalysts: A Study on Comminution and Alloying of Metal Nanoparticles
    De Bellis, J. and Petersen, H. and Ternieden, J. and Pfänder, N. and Weidenthaler, C. and Schüth, F.
    Angewandte Chemie - International Edition (2022)
    Ball milling is growing increasingly important as an alternative synthetic tool to prepare catalytic materials. It was recently observed that supported metal catalysts could be directly obtained upon ball milling from the coarse powders of metal and oxide support. Moreover, when two compatible metal sources are simultaneously subjected to the mechanochemical treatment, bimetallic nanoparticles are obtained. A systematic investigation was extended to different metals and supports to understand better the mechanisms involved in the comminution and alloying of metal nanoparticles. Based on this, a model describing the role of metal-support interactions in the synthesis was developed. The findings will be helpful for the future rational design of supported metal catalysts via dry ball milling. © 2022 The Authors. Angewandte Chemie International Edition published by Wiley-VCH GmbH.
    view abstractdoi: 10.1002/anie.202208016
  • 2022 • 1168 Influence of process gases containing helium on the laser beam melting process [Einfluss heliumhaltiger Prozess-gase auf den Laser-Strahlschmelz-prozess]
    Deckers, T. and Ammann, T. and Forêt, P. and Dubiez-Le-goff, S. and Zissel, K. and Witt, G.
    Zeitschrift Kunststofftechnik/Journal of Plastics Technology 117 452-455 (2022)
    Influence of Process Gases Containing Helium on the Laser Beam Melting Process. Can the process gas play a key role in optimizing the PBF-LB/M process (layer thickness, scan speed, processability of new materials, etc.)? This article provide insights into the current state of research at Linde GmbH regarding he-lium-containing process gases and presenting the novel process gas ADDvance® Laser230. Due to its composition, the gas mixture allows to significantly improve process productivity and stability. © 2022 Walter de Gruyter GmbH, Berlin/Boston, Germany.
    view abstractdoi: 10.1515/zwf-2022-1094
  • 2022 • 1167 Obtaining different orientation relationships for Cu films grown on (0001) α-Al2O3substrates by magnetron sputtering
    Dehm, G. and Edongué, H. and Wagner, T. and Oh, S.H. and Arzt, E.
    International Journal of Materials Research 96 249-254 (2022)
    Cu films were grown on (0001) α-Al2O3 single-crystals by magnetron sputtering. The growth behavior was manipulated by Ar+-ion sputter cleaning of the substrates at kinetic energies between 100 and 500 eV, changing the sputter rate from 0.75 to 1.1 nm/s, and using nominal substrate temperatures of 100 and 200 °C, respectively. Polycrystalline Cu films formed on α-Al2O3 substrates after an Ar+-ion bombardment at 500 eV, while epitaxial Cu films evolved when Ar+-ion energies of 100 and 200 eV were used. The epitaxial Cu films always consisted of two twin-related growth variants. However, two different orientation relationships emerged which differ by a 30° in-plane rotation of the (111) oriented Cu films when the deposition rate is changed from 0.75 to 1.1 nm/s. The results will be discussed on the basis of differences in the growth process. © 2005 Carl Hanser Verlag, München.
    view abstractdoi: 10.3139/ijmr-2005-0045
  • 2022 • 1166 Implication of grain-boundary structure and chemistry on plasticity and failure
    Dehm, G. and Cairney, J.
    MRS Bulletin 47 800-807 (2022)
    doi: 10.1557/s43577-022-00378-3
  • 2022 • 1165 Non-Classical Conversion of Methanol to Formaldehyde
    Deitermann, M. and Huang, Z. and Lechler, S. and Merko, M. and Muhler, M.
    Chemie-Ingenieur-Technik 94 1573-1590 (2022)
    Non-classical alternatives to the silver contact and the Formox processes comprise the thermal non-oxidative dehydrogenation of methanol, for which new catalysts are needed to achieve high formaldehyde selectivity at high conversion at temperatures below 600 °C. The electro- or photocatalytic conversion of methanol to formaldehyde is not applied either industrially but is attractive because of mild reaction conditions and high formaldehyde selectivities. Novel gas-phase approaches yielding (anhydrous) formaldehyde are presented describing lab-scale setups and the challenges for up-scaling. © 2022 The Authors. Chemie Ingenieur Technik published by Wiley-VCH GmbH.
    view abstractdoi: 10.1002/cite.202200083
  • 2022 • 1164 Kinetic model assessment for the synthesis of γ-valerolactone from n-butyl levulinate and levulinic acid hydrogenation over the synergy effect of dual catalysts Ru/C and Amberlite IR-120
    Delgado, J. and Vasquez Salcedo, W.N. and Bronzetti, G. and Casson Moreno, V. and Mignot, M. and Legros, J. and Held, C. and Grénman, H. and Leveneur, S.
    Chemical Engineering Journal 430 (2022)
    The production of platform molecules from the valorization of lignocellulosic biomass is increasing. Among these plateform molecules, γ-valerolactone (GVL) is a promising one and could be used for different industrial applications. This molecule is synthesized from levulinic acid (LA) or alkyl levulinates (AL) through a tandem hydrogenation/cyclization (lactonization) cascade. A lot of investigations have been carried out to develop the best catalyst for the hydrogenation step by using solely LA or AL. However, one should keep in mind that in the AL production via fructose alcoholysis, there is also LA production, and both are present in the product mixture during the further conversion. To the best of our knowledge, no article exists describing the hydrogenation of LA and AL simultaneously in one-pot. Also, the literature reporting the use of solid catalyst for the second cyclization step is rare. To fill this gap, the hydrogenation of levulinic acid and butyl levulinate (BL) was studied over Ru/C and Amberlite IR-120. Several kinetic models were evaluated via Bayesian inference and K-fold approach. The kinetic assessment showed that a non-competitive Langmuir-Hinshelwood with no dissociation of hydrogen where LA, BL and H2 are adsorbed on different sites (NCLH1.2) and non-competitive Langmuir-Hinshelwood with dissociation of hydrogen where LA, BL and H2 are adsorbed on different sites (NCLH2.2) are the best model to describe this system. The presence of LA and Amberlite IR-120 allows to increase the kinetics of cyclization steps, and in fine to accelerate the production of GVL. © 2021 Elsevier B.V.
    view abstractdoi: 10.1016/j.cej.2021.133053
  • 2022 • 1163 Influence of laser-generated surface micro-structuring on the intrinsically bonded hybrid system CFRP-EN AW 6082-T6 on its corrosion properties
    Delp, A. and Freund, J. and Wu, S. and Scholz, R. and Löbbecke, M. and Haubrich, J. and Tröster, T. and Walther, F.
    Composite Structures 285 (2022)
    The corrosion behavior of a hybrid material consisting of intrinsically bonded carbon fiber-reinforced epoxy resin with laser-structured EN AW 6082 metal was investigated. Particular attention was paid to the effects of the laser-structuring, surface topography and the contacting. Pristine and hybridized specimens were corroded in aqueous NaCl electrolyte (0.1 mol/l) using a potentiodynamic polarization technique and subsequently analyzed using computed tomography, scanning electron-, light- and laser scanning microscopy. The results show that the corrosive reaction arises mainly from the aluminum component. Surface pretreatment of the aluminum resulted in increasing corrosion rates, but showed no influence on the hybrids corrosion properties. Optical micrographs suggest that the epoxy resin acts as a sealant preventing galvanic corrosion between the aluminum and carbon fibers by hindering the diffusion of the electrolyte into the joints. While corrosion effects were observed locally at the aluminum surface, they were, contrary to expectations, not enhanced on the hybrid interfaces. © 2022 Elsevier Ltd
    view abstractdoi: 10.1016/j.compstruct.2022.115238
  • 2022 • 1162 Ultrafast All-Optical Polarization Switch Controlled by Optically Excited Picosecond Acoustic Perturbation of Exciton Resonance in Planar Microcavities
    Demenev, A.A. and Yaremkevich, D.D. and Scherbakov, A.V. and Gavrilov, S.S. and Yakovlev, D.R. and Kulakovskii, V.D. and Bayer, M.
    Physical Review Applied 18 (2022)
    doi: 10.1103/PhysRevApplied.18.044045
  • 2022 • 1161 Unfolding engineering metamaterials design: Relaxed micromorphic modeling of large-scale acoustic meta-structures
    Demore, F. and Rizzi, G. and Collet, M. and Neff, P. and Madeo, A.
    Journal of the Mechanics and Physics of Solids 168 (2022)
    In this paper, we present a unit cell showing a band-gap in the lower acoustic domain. The corresponding metamaterial is made up of a periodic arrangement of one unit cell. We rigorously show that the relaxed micromorphic model can be used for metamaterials’ design at large scales as soon as sufficiently large specimens are considered. We manufacture the metamaterial via metal etching procedures applied to a titanium plate so as to show that its production for realistic applications is viable. Experimental tests are also carried out confirming that the metamaterials’ response is in good agreement with the theoretical design. In order to show that our micromorphic model opens unprecedented possibilities in metastructural design, we conceive a finite-size structure that is able to focus elastic energy in a confined region, thus enabling its possible subsequent use for optimizing complex structures. Indeed, thanks to the introduction of a well-posed set of micromorphic boundary conditions, we can combine different metamaterials and classical Cauchy materials in such a way that the elastic energy produced by a source of vibrations is focused in specific collection points. The design of this structure would have not been otherwise possible (via e.g., direct simulations), due to the large dimensions of the metastructure, counting hundreds of unit cells. © 2022 Elsevier Ltd
    view abstractdoi: 10.1016/j.jmps.2022.104995
  • 2022 • 1160 Surface Resonant Raman Scattering from Cu(110)
    Denk, M. and Speiser, E. and Plaickner, J. and Chandola, S. and Sanna, S. and Zeppenfeld, P. and Esser, N.
    Physical Review Letters 128 (2022)
    doi: 10.1103/PhysRevLett.128.216101
  • 2022 • 1159 Controlled use of cooling lubricants for tribological optimization of machining processes – Efficient lubrication of the chip formation zone [Gezielter Einsatz von Kühlschmierstoffen zur tribologischen Optimierung von Zerspanprozessen Effizientes Schmieren der Spanbildungszon0e]
    Denkena, B. and Elgeti, S. and Ellersiek, L. and Lee, J. and Liu, H. and Pape, F. and Poll, G. and Saelzer, J. and Zabel, A.
    WT Werkstattstechnik 112 44-49 (2022)
    doi: 10.37544/1436-4980-2021-1-2-48
  • 2022 • 1158 Combining 2D and 3D Characterization Techniques for Determining Effects of HIP Rejuvenation After Fatigue Testing of SX Microstructures
    Dennstedt, A. and Lopez-Galilea, I. and Ruttert, B. and Theisen, W. and Bartsch, M.
    Metallurgical and Materials Transactions A: Physical Metallurgy and Materials Science (2022)
    doi: 10.1007/s11661-022-06914-9
  • 2022 • 1157 Signatures of collective modes in fifth harmonic generation of BCS superconductor
    Derendorf, P. and Müller, M.A. and Eremin, I.M.
    Faraday Discussions 237 186-197 (2022)
    doi: 10.1039/d2fd00067a
  • 2022 • 1156 Resolving particle shape in DEM simulations from tabulated geometry information
    Deshpande, R. and Mahiques, E. and Wirtz, S. and Scherer, V.
    Powder Technology 407 (2022)
    DEM applications require versatile representations of the particle shapes. The downside of resolved shapes is the required computational effort. In this short communication, we propose new measures to reduce the computational effort needed to evaluate the pairwise contact of resolved polytopes in DEM simulations. Employing the Gilbert–Johnson–Keerthi (GJK) and Expanding Polytope algorithm (EPA) algorithm it is demonstrated that restricting the particle vertices to the actually required ones, which can be obtained from a directional tabulation prior to the simulation, reduces the computational effort drastically. The feasibility of this strategy is evaluated and discussed. Applicability is demonstrated by comparing the simulated granular outflow of regular polyhedrons with differently resolved edges from a hopper with experimental data. The results obtained disclose the strong effect of geometric features on particle discharge. © 2022 Elsevier B.V.
    view abstractdoi: 10.1016/j.powtec.2022.117700
  • 2022 • 1155 A model for lime consolidation of porous solids
    Detmann, B. and Gavioli, C. and Krejčí, P. and Lamač, J. and Namlyeyeva, Y.
    Nonlinear Analysis: Real World Applications 65 (2022)
    We propose a mathematical model describing the process of filling the pores of a building material with lime water solution with the goal to improve the consistency of the porous solid. Chemical reactions produce calcium carbonate which glues the solid particles together at some distance from the boundary and strengthens the whole structure. The model consists of a 3D convection–diffusion system with a nonlinear boundary condition for the liquid and for calcium hydroxide, coupled with the mass balance equations for the chemical reaction. The main result consists in proving that the system has a solution for each initial data from a physically relevant class. A 1D numerical test shows a qualitative agreement with experimental observations. © 2021 Elsevier Ltd
    view abstractdoi: 10.1016/j.nonrwa.2021.103483
  • 2022 • 1154 Asymptotic equivalence for nonparametric regression with dependent errors: Gauss–Markov processes
    Dette, H. and Kroll, M.
    Annals of the Institute of Statistical Mathematics 74 1163-1196 (2022)
    doi: 10.1007/s10463-022-00826-6
  • 2022 • 1153 Quantifying deviations from separability in space-time functional processes
    Dette, H. and Dierickx, G. and Kutta, T.
    Bernoulli 28 2909-2940 (2022)
    doi: 10.3150/21-BEJ1442
  • 2022 • 1152 DESIGN ADMISSIBILITY AND DE LA GARZA PHENOMENON IN MULTIFACTOR EXPERIMENTS
    Dette, H. and Liu, X. and Yue, R.-X.
    Annals of Statistics 50 1247-1265 (2022)
    doi: 10.1214/21-AOS2147
  • 2022 • 1151 The effect of intraday periodicity on realized volatility measures
    Dette, H. and Golosnoy, V. and Kellermann, J.
    Metrika (2022)
    doi: 10.1007/s00184-022-00875-0
  • 2022 • 1150 Detecting relevant changes in the spatiotemporal mean function
    Dette, H. and Quanz, P.
    Journal of Time Series Analysis (2022)
    doi: 10.1111/jtsa.12674
  • 2022 • 1149 Introduction to the Minitrack on Open Platform Ecosystems in Logistics: Business Models and Technologies
    Detzner, P. and Möller, F. and Kerner, S. and Otto, B.
    Proceedings of the Annual Hawaii International Conference on System Sciences 2022-January 4899-4900 (2022)
  • 2022 • 1148 Microstructure, grain boundary evolution and anisotropic Fe segregation in (0001) textured Ti thin films
    Devulapalli, V. and Hans, M. and Sukumar, P.T. and Schneider, J.M. and Dehm, G. and Liebscher, C.H.
    Acta Materialia 238 (2022)
    doi: 10.1016/j.actamat.2022.118180
  • 2022 • 1147 Non-collinear magnetic structure of the MAX phase Mn2GaC epitaxial films inferred from zero-field NMR study (CE-5:L05)
    Dey, J. and Wójcik, M. and Jędryka, E. and Kalvig, R. and Wiedwald, U. and Salikhov, R. and Farle, M. and Rosén, J.
    Ceramics International (2022)
    doi: 10.1016/j.ceramint.2022.11.265
  • 2022 • 1146 Optical and structural properties of ZnO NPs and ZnO–Bi2O3 nanocomposites
    Dhahri, I. and Ellouze, M. and Labidi, S. and Al-Bataineh, Q.M. and Etzkorn, J. and Guermazi, H. and Telfah, A. and Tavares, C.J. and Hergenröder, R. and Appel, T.
    Ceramics International 48 266-277 (2022)
    Pure ZnO and ZnO–Bi2O3 nanocomposites with 5 wt% and 10 wt% of Bi2O3 content were synthesized using the co-precipitation method. Optical properties such as refractive index (n), extinction coefficient (k), bandgap (Eg), and Urbach energies, as well as the band structure, were determined by modeling the experimental transmittance and reflectance UV–Vis spectra. The deduced bandgap and Urbach energies for pure ZnO (3.758 eV) increase with the increase of the doping degree of Bi2O3 in ZnO–Bi2O3 nanocomposite films. X-ray diffraction and scanning electron microscopy (SEM) was used to study the structural and morphological properties of these nanocomposite films. Pure ZnO and nanocomposites with Bi2O3 exhibit crystalline domains with wurtzite hexagonal structures, and as the doping degree of Bi2O3 increases, the crystallite size decreases. Based on SEM micrographs, the ZnO nanoparticles (NPs) structure shows the presence of aggregation. Moreover, Bi2O3 NPs in the nanocomposite film led to the further aggregation in the form of large rods. The elemental and chemical properties of the nanocomposites were investigated using infrared and energy-dispersive X-ray spectroscopy. The charge transfer process in the studied system is between ZnO and Bi2O3 conduction bands. Density-functional theory (DFT) calculations were performed for ZnO, Bi2O3, and ZnO-Bi2O3 compounds to investigate structural, optical, and electronic properties, being in agreement with the experimental results. © 2021 Elsevier Ltd and Techna Group S.r.l.
    view abstractdoi: 10.1016/j.ceramint.2021.09.101
  • 2022 • 1145 Template-Induced Precursor Formation in Heterogeneous Nucleation: Controlling Polymorph Selection and Nucleation Efficiency
    Díaz Leines, G. and Rogal, J.
    Physical Review Letters 128 (2022)
    We present an atomistic study of heterogeneous nucleation in Ni employing transition path sampling, which reveals a template precursor-mediated mechanism of crystallization. Most notably, we find that the ability of tiny templates to modify the structural features of the liquid and promote the formation of precursor regions with enhanced bond-orientational order is key to determining their nucleation efficiency and the polymorphs that crystallize. Our results reveal an intrinsic link between structural liquid heterogeneity and the nucleating ability of templates, which significantly advances our understanding toward the control of nucleation efficiency and polymorph selection. © 2022 American Physical Society.
    view abstractdoi: 10.1103/PhysRevLett.128.166001
  • 2022 • 1144 Orbital selective switching of ferromagnetism in an oxide quasi two-dimensional electron gas
    Di Capua, R. and Verma, M. and Radovic, M. and Strocov, V.N. and Piamonteze, C. and Guedes, E.B. and Plumb, N.C. and Chen, Y. and D’Antuono, M. and De Luca, G.M. and Di Gennaro, E. and Stornaiuolo, D. and Preziosi, D. and Jouaul...
    npj Quantum Materials 7 (2022)
    Multi-orbital physics in quasi-two-dimensional electron gases (q2DEGs) triggers intriguing phenomena not observed in bulk materials, such as unconventional superconductivity and magnetism. Here, we investigate the mechanism of orbital selective switching of the spin-polarization in the oxide q2DEG formed at the (001) interface between the LaAlO3, EuTiO3 and SrTiO3 band insulators. By using density functional theory calculations, transport, magnetic and x-ray spectroscopy measurements, we find that the filling of titanium-bands with 3dxz/3dyz orbital character in the EuTiO3 layer and at the interface with SrTiO3 induces an antiferromagnetic to ferromagnetic switching of the exchange interaction between Eu-4f7 magnetic moments. The results explain the observation of the carrier density-dependent ferromagnetic correlations and anomalous Hall effect in this q2DEG, and demonstrate how combined theoretical and experimental approaches can lead to a deeper understanding of emerging electronic phases and serve as a guide for the materials design of advanced electronic applications. © 2022, The Author(s).
    view abstractdoi: 10.1038/s41535-022-00448-4
  • 2022 • 1143 Robust optimization in nanoparticle technology: A proof of principle by quantum dot growth in a residence time reactor
    Dienstbier, J. and Aigner, K.-M. and Rolfes, J. and Peukert, W. and Segets, D. and Pflug, L. and Liers, F.
    Computers and Chemical Engineering 157 (2022)
    Knowledge-based determination of the best-possible experimental setups for nanoparticle design is highly challenging. Additionally, such processes are accompanied by noticeable uncertainties. Therefore, protection against those is needed. Robust optimization helps determining optimal processes. The latter guarantees quality requirements regardless of how uncertainties e.g., in raw materials, particle size distributions (PSD), heat and mass transport characteristics, and (growth) rates, manifest within predefined ranges. To approach this task, we exemplarily model a particle synthesis process with seeded growth by population balance equations and study different growth kinetics. We determine the mean residence time maximizing the product mass subject to a guaranteed yield. Additionally, we hedge against uncertain growth rates and derive an algorithmically tractable reformulation for the robustified problem. This reformulation can be applied if both the objective and the constraint functions are quasiconcave in the uncertainty which is a natural assumption in this context. We also show that the approach extends to higher-dimensional uncertainties if the uncertain parameters do not influence each other. We evaluate our approach for seeded growth synthesis of zinc oxide quantum dots and demonstrate computationally that a guaranteed yield is met for all growth rates within predefined regions. The protection against uncertainties only reduces the maximum amount of product that can be obtained by a negligible margin. © 2021
    view abstractdoi: 10.1016/j.compchemeng.2021.107618
  • 2022 • 1142 ANALYSIS OF LEARNING OBJECTS FOR OPTIMIZATION AND DIGITAL TRANSFER REPORT OF INTERMEDIATE RESULTS ON LEARNING PATH IDEAS – FIRST SURVEY
    Dillenhöfer, F. and Künne, B.
    Proceedings of the International Conference on E-Learning 2022, EL 2022 - Part of the Multi Conference on Computer Science and Information Systems 2022, MCCSIS 2022 169-172 (2022)
  • 2022 • 1141 Neologised teaching concept and materials combine remote teaching and hands-on activities
    Dillenhofer, F. and Kunne, B. and Willms, U.
    2022 IEEE German Education Conference, GeCon 2022 (2022)
    doi: 10.1109/GeCon55699.2022.9942764
  • 2022 • 1140 Pinning of domain walls by strontium layer in the BaTiO3 perovskite: An atomic-scale study
    Dimou, A. and Hirel, P. and Grünebohm, A.
    Physical Review B 106 (2022)
    doi: 10.1103/PhysRevB.106.094104
  • 2022 • 1139 Color and pseudogap tunability in multicomponent carbonitrides
    Dippo, O.F. and Sangiovanni, D.G. and Wenger, E. and Vecchio, K.S.
    Materials and Design 217 (2022)
    doi: 10.1016/j.matdes.2022.110600
  • 2022 • 1138 Advances towards Cell-Specific Gene Transfection: A Small-Molecule Approach Allows Order-of-Magnitude Selectivity
    Dirksmeyer, T. and Stahl, P. and Vallet, C. and Knauer, S. and Giese, M. and Schmuck, C. and Hirschhäuser, C.
    Chemistry (Weinheim an der Bergstrasse, Germany) 28 e202202024 (2022)
    doi: 10.1002/chem.202202024
  • 2022 • 1137 Influence of Heat Treatment Parameters on the Carbide Morphology of PM High-Speed Steel HS 6-5-3-8
    Disch, N. and Benito, S. and Röttger, A. and Weber, S.
    Steel Research International (2022)
    doi: 10.1002/srin.202200755
  • 2022 • 1136 Time resolved studies reveal the origin of the unparalleled high efficiency of one nanosecond laser ablation in liquids
    Dittrich, S. and Spellauge, M. and Barcikowski, S. and Huber, H.P. and Gökce, B.
    Opto-Electronic Advances 5 (2022)
    doi: 10.29026/oea.2022.210053
  • 2022 • 1135 Shock tube study of the pyrolysis kinetics of Di- and trimethoxy methane
    Döntgen, M. and Fuller, M.E. and Peukert, S. and Nativel, D. and Schulz, C. and Alexander Heufer, K. and Franklin Goldsmith, C.
    Combustion and Flame 242 (2022)
    The high potential of oxymethylene ethers (OMEs) and related compounds as fuels and fuel-additives motivated a multitude of experimental and theoretical investigations on, e.g., dimethoxy methane (DMM), the smallest member of the OME family. The present work adds to this research by providing combined experimental and theoretical rate coefficients for di- and trimethoxy methane (TMM) pyrolysis. For DMM pyrolysis, the branching ratios between the major dissociation pathways remained elusive in recent studies and is elucidated in the present work using four independent sets of shock tube experiments and master equation modeling. For TMM pyrolysis, the present work provides the very first detailed chemical kinetics model. A key consumption reaction of both compounds, DMM and TMM, is the methoxy-induced H-atom migration, which yields methanol and a singlet diradical. While for DMM this reaction is in direct competition to the C–O bond fission reactions, TMM is found to be a prime example for methoxy-induced H-atom migration, as its pyrolysis chemistry is exclusively governed by this reaction. With the present work, the details of DMM pyrolysis are elucidated and the foundation is laid for detailed chemical kinetics modeling of TMM. © 2022 The Combustion Institute
    view abstractdoi: 10.1016/j.combustflame.2022.112186
  • 2022 • 1134 PDA LASER MEASUREMENTS OF DROPLET-LADEN FLOWS IN A FOUR STAGE AXIAL COMPRESSOR
    Doerr, T. and Schuster, S. and Brillert, D.
    Proceedings of the ASME Turbo Expo 10-A (2022)
    doi: 10.1115/GT2022-80284
  • 2022 • 1133 AN EULER-BASED THROUGHFLOW APPROACH FOR CENTRIFUGAL COMPRESSORS - PART B: EXPERIMENTAL INVESTIGATIONS AND VALIDATION
    Doerr, T. and Yildiz, A. and Dolle, B. and Brillert, D.
    Proceedings of the ASME Turbo Expo 7 (2022)
    doi: 10.1115/GT2022-82114
  • 2022 • 1132 Interaction of Human Resistin with Human Islet Amyloid Polypeptide at Charged Phospholipid Membranes
    Dogan, S. and Paulus, M. and Kosfeld, B.R. and Cewe, C. and Tolan, M.
    ACS Omega 7 22377-22382 (2022)
    An X-ray reflectivity study on the interaction of recombinant human resistin (hRes) with fibrillation-prone human islet amyloid polypeptide (hIAPP) at anionic phospholipid Langmuir films as model membranes is presented. Aggregation and amyloid formation of hIAPP is considered the main mechanism of pancreatic β-cell loss in patients with type 2 diabetes mellitus. Resistin shows a chaperone-like ability, but also tends to form aggregates by itself. Resistin and hIAPP cross multiply metabolism pathways. In this study, we researched the potential protective effects of resistin against hIAPP-induced lipid membrane rupture. The results demonstrate that resistin can inhibit or prevent hIAPP adsorption even in the presence of aggregation-promoting negatively charged lipid interfaces. Moreover, we found strong hydrophobic interactions of resistin at the bare buffer-air interface. © 2022 American Chemical Society. All rights reserved.
    view abstractdoi: 10.1021/acsomega.2c01363
  • 2022 • 1131 Nondestructive Compression and Fluidization of Phospholipid Monolayers by Gaseous and Aerolized Perfluorocarbons: Promising Substances for Lung Surfactant Treatment
    Dogan, S. and Paulus, M. and Surmeier, G. and Foryt, K. and Brägelmann, K. and Tolan, M.
    Langmuir 38 6690-6699 (2022)
    We present a surface-sensitive X-ray scattering study on the influence of gaseous and aerolized perfluorocarbons (FCs) on zwitterionic and anionic phospholipid Langmuir films, which serve as a simplified model system of lung surfactants. It was found that small gaseous FC molecules like F-propane and F-butane penetrate phospholipid monolayers and accumulate between the alkyl chains and form islands. This clustering process can trigger the formation of lipid crystallites at low initial surface pressures. In contrast, the large linear FC F-octyl bromide fluidizes membranes, causing a dissolution of crystalline domains. The bicyclic FC F-decalin accumulates between the alkyl chains of 1,2-dipalmitoyl phosphatidylcholine but cannot penetrate the more densely packed 1,2-dipalmitoyl phosphatidic acid films because of its size. The effects of FCs on lung surfactants are discussed in the framework of currently proposed therapeutic methods for acute respiratory distress syndrome using FC gases, vapor, or aerosol ventilation causing monolayer fluidization effects. This study implies that the highly biocompatible and nontoxic FCs could be beneficial in the treatment of lung diseases with injured nonfunctional lung surfactants in a novel approach for ventilation. © 2022 The Authors. Published by American Chemical Society.
    view abstractdoi: 10.1021/acs.langmuir.2c00617
  • 2022 • 1130 Production of bactericidal powder suitable for laser powder bed fusion by silver nanoadditivation of polyamide
    Doñate-Buendia, C. and Ingendoh-Tsakmakidis, A. and Hupfeld, T. and Winkel, A. and Barcikowski, S. and Gökce, B.
    Procedia CIRP 111 47-50 (2022)
    doi: 10.1016/j.procir.2022.08.113
  • 2022 • 1129 Revealing the influence of Mo addition on interphase precipitation in Ti-bearing low carbon steels
    Dong, H. and Chen, H. and Riyahi khorasgani, A. and Zhang, B. and Zhang, Y. and Wang, Z. and Zhou, X. and Wang, W. and Wang, H. and Li, T. and Yang, Z. and van der Zwaag, S.
    Acta Materialia 223 (2022)
    Mo is widely used as an effective microalloying element to improve mechanical performance of interphase precipitation steels, but the precise role of Mo in interphase precipitation behavior is not fully understood. In this contribution, interphase precipitation behavior in a series of Ti-Mo-bearing low carbon steels is systematically studied, and the role of Mo in interphase precipitates and its coarsening behavior is revisited. It is found that (Ti, Mo)C precipitates instead of TiC are formed in the Mo-containing alloys, and the average site fraction of Mo in (Ti, Mo)C is almost independent of the bulk Mo content. Moreover, the number density of interphase precipitates can be substantially enhanced by a minor addition of Mo, albeit it does not further rise with increasing the bulk Mo content. This is because the Mo fraction in (Ti, Mo)C rather than the bulk Mo content governs the driving force for precipitation nucleation and the interfacial energy of the (Ti, Mo)C/α and (Ti, Mo)C/γ interfaces. In addition to the reduced interfacial energy, decrease of Ti trans-interface diffusivity has been identified as another key reason for the enhanced carbide coarsening resistance in Mo-containing alloys. © 2021 Acta Materialia Inc.
    view abstractdoi: 10.1016/j.actamat.2021.117475
  • 2022 • 1128 Hydrogen-associated decohesion and localized plasticity in a high-Mn and high-Al two-phase lightweight steel
    Dong, X. and Wang, D. and Thoudden-Sukumar, P. and Tehranchi, A. and Ponge, D. and Sun, B. and Raabe, D.
    Acta Materialia 239 (2022)
    Advanced lightweight high-strength steels are often compositionally and microstructurally complex. While this complex feature enables the activation of multiple strengthening and strain-hardening mechanisms, it also leads to a complicated damage behavior, especially in the presence of hydrogen (H). The mechanisms of hydrogen embrittlement (HE) in these steels need to be properly understood for their successful application. Here we focus on a high-Mn (∼20 wt.%), high-Al (∼9 wt.%) lightweight steel with an austenite (∼74 vol.%) and ferrite (∼26 vol.%) two-phase microstructure and unravel the interplay of H-related decohesion and localized plasticity and their effects on failure. We find that HE in this alloy is driven by both, H-induced intergranular cracking along austenite-ferrite phase boundaries and H-induced transgranular cracking inside the ferrite. The former phenomenon is attributed to the mechanism of H-enhanced decohesion. For the latter damage behavior, systematic scanning electron microscopy-based characterization reveals that only parts of the transgranular cracks inside ferrite are straight (∼52% proportion) and along the cleavage plane. Other portions of these transgranular cracks show a distinct deviation from the {100} planes at certain stages of crack propagation, which is associated with a mechanism transition from the H-enhanced transgranular decohesion of the ferrite by cleavage to the H-associated localized plasticity occurring near the propagating crack tip. These mechanisms are further discussed based on a detailed comparison to the damage behavior at cryogenic temperatures and on the nanoindentation results performed with in-situ H-charging. The findings provide new insights into the understanding of the interplay between different HE mechanisms operating in high-strength alloys and their synergistic effects on damage evolution. © 2022 Acta Materialia Inc.
    view abstractdoi: 10.1016/j.actamat.2022.118296
  • 2022 • 1127 Quantitative determination of the electric field strength in a plasmon focus from ponderomotive energy shifts
    Dreher, P. and Janoschka, D. and Neuhaus, A. and Frank, B. and Giessen, H. and Horn-Von Hoegen, M. and Meyer Zu Heringdorf, F.-J.
    Nanophotonics 11 3687-3694 (2022)
    doi: 10.1515/nanoph-2022-0284
  • 2022 • 1126 A small-scale creep test for calibrating an efficient lifetime model for high pressure turbine blades [Ein miniaturisierter Kriechversuch zur Kalibrierung eines effizienten Lebensdauermodells für Hochdruckturbinenschaufeln]
    Dresbach, C. and Wischek, J. and Bartsch, M. and Prien, T.
    Materialwissenschaft und Werkstofftechnik 53 440-448 (2022)
    doi: 10.1002/mawe.202100347
  • 2022 • 1125 Beneficial Effects of Low Iron Contents on Cobalt-Containing Spinel Catalysts in the Gas Phase 2-Propanol Oxidation
    Dreyer, M. and Hagemann, U. and Heidelmann, M. and Budiyanto, E. and Cosanne, N. and Ortega, K.F. and Najafishirtari, S. and Hartmann, N. and Tüysüz, H. and Behrens, M.
    ChemCatChem 14 (2022)
    doi: 10.1002/cctc.202200472
  • 2022 • 1124 Thermo-Responsive Hydrophilic Support for Polyamide Thin-Film Composite Membranes with Competitive Nanofiltration Performance
    Drikvand, H.N. and Golgoli, M. and Zargar, M. and Ulbricht, M. and Nejati, S. and Mansourpanah, Y.
    Polymers 14 (2022)
    Poly(N-isopropylacrylamide) (PNIPAAm) was introduced into a polyethylene terephthalate (PET) nonwoven fabric to develop novel support for polyamide (PA) thin-film composite (TFC) membranes without using a microporous support layer. First, temperature-responsive PNIPAAm hydrogel was prepared by reactive pore-filling to adjust the pore size of non-woven fabric, creating hydrophilic support. The developed PET-based support was then used to fabricate PA TFC membranes via interfacial polymerization. SEM–EDX and AFM results confirmed the successful fabrication of hydrogel-integrated non-woven fabric and PA TFC membranes. The newly developed PA TFC membrane demonstrated an average water permeability of 1 L/m2 h bar, and an NaCl rejection of 47.0% at a low operating pressure of 1 bar. The thermo-responsive property of the prepared membrane was studied by measuring the water contact angle (WCA) below and above the lower critical solution temperature (LCST) of the PNIPAAm hydrogel. Results proved the thermo-responsive behavior of the prepared hydrogel-filled PET-supported PA TFC membrane and the ability to tune the membrane flux by changing the operating temperature was confirmed. Overall, this study provides a novel method to fabricate TFC membranes and helps to better understand the influence of the support layer on the separation performance of TFC membranes. © 2022 by the authors.
    view abstractdoi: 10.3390/polym14163376
  • 2022 • 1123 Approximating the impact of nuclear quantum effects on thermodynamic properties of crystalline solids by temperature remapping
    Dsouza, R. and Huber, L. and Grabowski, B. and Neugebauer, J.
    Physical Review B 105 (2022)
    When computing finite-temperature properties of materials with atomistic simulations, nuclear quantum effects are often neglected or approximated at the quasiharmonic level. The inclusion of these effects beyond this level using approaches like the path integral method is often not feasible due to their large computational effort. We discuss and evaluate the performance of a temperature-remapping approach that links the finite-temperature quantum system to its best classical surrogate via a temperature map. This map, which is constructed using the internal energies of classical and quantum harmonic oscillators, is shown to accurately capture the impact of quantum effects on thermodynamic properties at an additional cost that is negligible compared to classical molecular dynamics simulations. Results from this approach show excellent agreement with previously reported path integral Monte Carlo simulation results for diamond cubic carbon and silicon. The approach is also shown to work well for obtaining thermodynamic properties of light metals and for the prediction of the fcc to bcc phase transition in calcium. © 2022 authors. Published by the American Physical Society. Published by the American Physical Society under the terms of the "https://creativecommons.org/licenses/by/4.0/"Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article's title, journal citation, and DOI. Open access publication funded by the Max Planck Society.
    view abstractdoi: 10.1103/PhysRevB.105.184111
  • 2022 • 1122 Nanocomposite Concept for Electrochemical in Situ Preparation of Pt-Au Alloy Nanoparticles for Formic Acid Oxidation
    Du, J. and Quinson, J. and Zhang, D. and Wang, B. and Wiberg, G.K.H. and Pittkowski, R.K. and Schröder, J. and Simonsen, Sø.B. and Kirkensgaard, J.J.K. and Li, Y. and Reichenberger, S. and Barcikowski, S. and Jensen, K.M.Ø. and Arenz, M.
    JACS Au 2 1757-1768 (2022)
    doi: 10.1021/jacsau.2c00335
  • 2022 • 1121 Rare-earth doped BiFe0.95Mn0.05O3 nanoparticles for potential hyperthermia applications
    Dubey, A. and Salamon, S. and Attanayake, S.B. and Ibrahim, S. and Landers, J. and Castillo, M.E. and Wende, H. and Srikanth, H. and Shvartsman, V.V. and Lupascu, D.C.
    Frontiers in Bioengineering and Biotechnology 10 (2022)
    Ionic engineering is exploited to substitute Bi cations in BiFe0.95Mn0.05O3 NPs (BFM) with rare-earth (RE) elements (Nd, Gd, and Dy). The sol-gel synthesized RE-NPs are tested for their magnetic hyperthermia potential. RE-dopants alter the morphology of BFM NPs from elliptical to rectangular to irregular hexagonal for Nd, Gd, and Dy doping, respectively. The RE-BFM NPs are ferroelectric and show larger piezoresponse than the pristine BFO NPs. There is an increase of the maximum magnetization at 300 K of BFM up to 550% by introducing Gd. In hyperthermia tests, 3 mg/ml dispersion of NPs in water and agar could increase the temperature of the dispersion up to ∼39°C under an applied AC magnetic field of 80 mT. Although Gd doping generates the highest increment in magnetization of BFM NPs, the Dy-BFM NPs show the best hyperthermia results. These findings show that RE-doped BFO NPs are promising for hyperthermia and other biomedical applications. Copyright © 2022 Dubey, Salamon, Attanayake, Ibrahim, Landers, Castillo, Wende, Srikanth, Shvartsman and Lupascu.
    view abstractdoi: 10.3389/fbioe.2022.965146
  • 2022 • 1120 Mono-, Di-, and Tri-Valent Cation Doped BiFe0.95Mn0.05O3 Nanoparticles: Ferroelectric Photocatalysts
    Dubey, A. and Keat, C.H. and Shvartsman, V.V. and Yusenko, K.V. and Castillo, M.E. and Buzanich, A.G. and Hagemann, U. and Kovalenko, S.A. and Stähler, J. and Lupascu, D.C.
    Advanced Functional Materials 32 (2022)
    The ferroelectricity of multivalent codoped Bismuth ferrite (BiFeO3; BFO) nanoparticles (NPs) is revealed and utilized for photocatalysis, exploiting their narrow electronic bandgap. The photocatalytic activity of ferroelectric photocatalysts BiFe0.95Mn0.05O3 (BFM) NPs and mono-, di-, or tri-valent cations (Ag+, Ca2+, Dy3+; MDT) coincorporated BFM NPs are studied under ultrasonication and in acidic conditions. It is found that such doping enhances the photocatalytic activity of the ferroelectric NPs approximately three times. The correlation of the photocatalytic activity with structural, optical, and electrical properties of the doped NPs is established. The increase of spontaneous polarization by the mono- and tri-valent doping is one of the major factors in enhancing the photocatalytic performance along with other factors such as stronger light absorption in the visible range, low recombination rate of charge carriers, and larger surface area of NPs. A-site doping of BFO NPs by divalent elements suppresses the polarization, whereas trivalent (Dy3+) and monovalent (Ag+) cations provide an increase of polarization. The depolarization field in these single domain NPs acts as a driving force to mitigate recombination of the photoinduced charge carriers. © 2022 The Authors. Advanced Functional Materials published by Wiley-VCH GmbH.
    view abstractdoi: 10.1002/adfm.202207105
  • 2022 • 1119 Multivariate Mean Comparison Under Differential Privacy
    Dunsche, M. and Kutta, T. and Dette, H.
    Lecture Notes in Computer Science (including subseries Lecture Notes in Artificial Intelligence and Lecture Notes in Bioinformatics) 13463 LNCS 31-45 (2022)
    doi: 10.1007/978-3-031-13945-1_3
  • 2022 • 1118 Archetypes of open-source business models
    Duparc, E. and Möller, F. and Jussen, I. and Stachon, M. and Algac, S. and Otto, B.
    Electronic Markets 32 727-745 (2022)
    The open-source paradigm offers a plethora of opportunities for innovative business models (BMs) as the underlying codebase of the technology is accessible and extendable by external developers. However, finding the proper configuration of open-source business models (OSBMs) is challenging, as existing literature gives guidance through commonly used BMs but does not describe underlying design elements. The present study generates a taxonomy following an iterative development process based on established guidelines by analyzing 120 OSBMs to complement the taxonomy's conceptually-grounded design elements. Then, a cluster-based approach is used to develop archetypes derived from dominant features. The results show that OSBMs can be classified into seven archetypical patterns: open-source platform BM, funding-based BM, infrastructure BM, Open Innovation BM, Open Core BM, proprietary-like BM, and traditional open-source software (OSS) BM. The results can act as a starting point for further investigation regarding the use of the open-source paradigm in the era of digital entrepreneurship. Practitioners can find guidance in designing OSBMs. © 2022, The Author(s).
    view abstractdoi: 10.1007/s12525-022-00557-9
  • 2022 • 1117 Evaluating Platform Openness in Logistics based on a Taxonomic Analysis
    Duparc, E. and Culotta, C. and Otto, B.
    Proceedings of the Annual Hawaii International Conference on System Sciences 2022-January 4911-4920 (2022)
  • 2022 • 1116 Atomic cluster expansion: Completeness, efficiency and stability
    Dusson, G. and Bachmayr, M. and Csányi, G. and Drautz, R. and Etter, S. and van der Oord, C. and Ortner, C.
    Journal of Computational Physics 454 (2022)
    The Atomic Cluster Expansion (Drautz (2019) [21]) provides a framework to systematically derive polynomial basis functions for approximating isometry and permutation invariant functions, particularly with an eye to modelling properties of atomistic systems. Our presentation extends the derivation by proposing a precomputation algorithm that yields immediate guarantees that a complete basis is obtained. We provide a fast recursive algorithm for efficient evaluation and illustrate its performance in numerical tests. Finally, we discuss generalisations and open challenges, particularly from a numerical stability perspective, around basis optimisation and parameter estimation, paving the way towards a comprehensive analysis of the convergence to a high-fidelity reference model. © 2022 Elsevier Inc.
    view abstractdoi: 10.1016/j.jcp.2022.110946
  • 2022 • 1115 Non-equilibrium phonon distribution caused by an electrical current
    Dwedari, M. and Brendel, L. and Wolf, D.E.
    New Journal of Physics 24 (2022)
    doi: 10.1088/1367-2630/aca11a
  • 2022 • 1114 Optical Optimization Potential of Transparent-Passivated Contacts in Silicon Solar Cells
    Eberst, A. and Zamchiy, A. and Qiu, K. and Winkel, P. and Gebrewold, H.T. and Lambertz, A. and Duan, W. and Li, S. and Bittkau, K. and Kirchartz, T. and Rau, U. and Ding, K.
    Solar RRL (2022)
    Herein, an optical loss analysis of the recently introduced silicon carbide–based transparent passivating contact (TPC) for silicon heterojunction solar cells is presented, the most dominant losses are identified, and the potential for reducing these losses is discussed. Magnesium fluoride is applied as an antireflective coating to reduce the reflective losses by up to 0.8 mA cm−2. When applying the magnesium fluoride, the passivation quality of the layer stack degrades, but is restored after annealing on a hot plate in ambient air. Afterwards, a road map for TPC solar cells toward an efficiency of 25% is presented and discussed. The largest part in efficiency gain is achieved by reducing the finger width and by increasing the passivation quality. Furthermore, it is shown that TPC solar cells have the potential to achieve short-circuit current densities above 42 mA cm−2 if the finger width is reduced and the front-side indium tin oxide (ITO) layer can be replaced by an ITO silicon nitride double layer. © 2022 The Authors. Solar RRL published by Wiley-VCH GmbH
    view abstractdoi: 10.1002/solr.202101050
  • 2022 • 1113 Antiferromagnetic Chern insulator in centrosymmetric systems
    Ebrahimkhas, M. and Uhrig, G.S. and Hofstetter, W. and Hafez-Torbati, M.
    Physical Review B 106 (2022)
    doi: 10.1103/PhysRevB.106.205107
  • 2022 • 1112 Catalytic effects for cellulose-based model fuels under low and high heating rate in air and oxy-fuel atmosphere
    Eckhard, T. and Pflieger, C. and Schmidt, S. and Böttger, J. and Senneca, O. and Schiemann, M. and Scherer, V. and Muhler, M. and Cerciello, F.
    Fuel 324 (2022)
    The detailed catalytic influence of minerals on solid biomass in oxy-fuel combustion is yet to be fully understood. The catalytic influence of metal sulfates on a mineral-free, cellulose-based model biomass was investigated during slow and high heating in air and oxy-fuel combustion. Measurements were performed in a thermogravimetric setup in air with slow heating rates and in a flat-flame burner in oxy-fuel combustion atmosphere with high heating rates. Temperature-programmed experiments identified the catalytic activity scale of Fe &gt; K &gt; Na &gt; Mg ∼ Ca in synthetic air (20% O2/He) for the sulfates. The highly active metals Fe and K were chosen for more detailed investigations in oxy-fuel combustion experiments using an additional loading of Mg as less-volatile mineral tracer. Samples doped with Fe and Mg (FeMg-MH) exhibited lower thermal stability and higher particle combustion temperatures in the flat-flame burner compared with the undoped model fuel, while the combination of K and Mg (KMg-MH) decreased the particle combustion temperature drastically during oxy-fuel combustion. X-ray diffraction patterns acquired between 25 and 800 °C showed that in FeMg-MH the mineral phases FeSO4 and MgSO4 were still separated and independently active, while the addition of MgSO4 to K2SO4 formed the stable mineral phase Langbeinite inhibiting the K mobility. The influence of metal chlorides and nitrates was also investigated by slow heating rate TGA experiments showing an overlapping of metal salts decomposition and carbon devolatilization and oxidation. © 2022 Elsevier Ltd
    view abstractdoi: 10.1016/j.fuel.2022.124437
  • 2022 • 1111 Numerical Simulation of Tube Manufacturing Consisting of Roll Forming and High-Frequency Induction Welding
    Egger, C. and Lüchinger, M. and Schreiner, M. and Tillmann, W.
    Materials 15 (2022)
    This paper presents a fully coupled three-dimensional finite element model for the simulation of a tube manufacturing process consisting of roll forming and high-frequency induction welding. The multiphysics model is based on the dual mesh method. Thus, the electromagnetic field, the temperature field, the elasto-plastic deformation of the weld bead, and the phase transformations within the material can be simulated for a moving tube without remeshing. A comparison with mea-surements shows that the geometry of the welded tube and the weld bead, the force on the squeeze rolls, the temperature along the band edges, and the hardness distribution within the heat-affected zone can be simulated realistically. © 2022 by the authors. Licensee MDPI, Basel, Switzerland.
    view abstractdoi: 10.3390/ma15031270
  • 2022 • 1110 Experimental Investigation of Temperature and Contact Pressure Influence on HFI Welded Joint Properties
    Egger, C. and Kroll, M. and Kern, K. and Steimer, Y. and Schreiner, M. and Tillmann, W.
    Materials 15 (2022)
    This paper presents an experimental electro-thermo-mechanical simulation of high-frequency induction (HFI) welding to investigate the effect of temperature and contact normal stress on the weld seam quality. Therefore welding experiments at different temperatures and contact pressures are performed using flat specimens of 34MnB5 steel sheet. In order to characterize the weld seam strength of the welded specimens, tensile and bending tests are performed. To obtain a relative weld seam strength, the bending specimens were additionally hardened prior to testing. With the hardened specimens, it can be shown that the weld seam strength increases with increasing temperature and contact normal stress until a kind of plateau is formed where the weld seam strength remains almost constant. In addition to mechanical testing, the influence of the investigated process parameters on the weld seam microstructure is studied metallographically using light optical microscopy, scanning electron microscopy, EBSD and hardness measurements. It is shown that the weld seam strength is related to the amount of oxides in the bonding line. © 2022 by the authors. Licensee MDPI, Basel, Switzerland.
    view abstractdoi: 10.3390/ma15103615
  • 2022 • 1109 Influence of a Calcium Phosphate Coating (BONIT®) on the Proliferation and Differentiation Potential of Human Mesenchymal Stroma Cells in the Early Phase of Bone Healing
    Eggert, A. and Buhren, B.A. and Schrumpf, H. and Haversath, M. and Ruppert, M. and Jäger, M. and Krauspe, R. and Zilkens, C.
    Journal of Functional Biomaterials 13 (2022)
    doi: 10.3390/jfb13040176
  • 2022 • 1108 Precipitation Evolution in the Heat-Affected Zone and Coating Material of AA2024 Processed by Friction Surfacing
    Ehrich, J. and Staron, P. and Karkar, A. and Roos, A. and Hanke, S.
    Advanced Engineering Materials 24 (2022)
    doi: 10.1002/adem.202201019
  • 2022 • 1107 Chipless RFID Tags Placement Optimization as Infrastructure for Maximal Localization Coverage
    El-Absi, M. and Al-Haj Abbas, A. and Kaiser, T.
    IEEE Journal of Radio Frequency Identification 6 368-380 (2022)
    doi: 10.1109/JRFID.2022.3189555
  • 2022 • 1106 Hydrogen-assisted decohesion associated with nanosized grain boundary κ-carbides in a high-Mn lightweight steel
    Elkot, M.N. and Sun, B. and Zhou, X. and Ponge, D. and Raabe, D.
    Acta Materialia 241 (2022)
    While age-hardened austenitic high-Mn and high-Al lightweight steels exhibit excellent strength-ductility combinations, their properties are strongly degraded when mechanically loaded under harsh environments, e.g. with the presence of hydrogen (H). The H embrittlement in this type of materials, especially pertaining to the effect of κ-carbide precipitation, has been scarcely studied. Here we focus on this subject, using a Fe-28.4Mn-8.3Al-1.3C (wt%) steel in different microstructure conditions, namely, solute solution treated and age-hardened. Contrary to the reports that grain boundary (GB) κ-carbides precipitate only during overaging, site-specific atom probe tomography and scanning transmission electron microscopy (STEM) reveal the existence of nanosized GB κ-carbides at early stages of aging. We correlate this observation with the deterioration of H embrittlement resistance in aged samples. While H pre-charged solution-treated samples fail by intergranular fracture at depths consistent with the H ingress depth (∼20 µm), age-hardened samples show intergranular fracture features at a much larger depth of above 500 µm, despite similar amount of H introduced into the material. This difference is explained in terms of the facile H-induced decohesion of GB κ-carbides/matrix interfaces where H can be continuously supplied through internal short-distance diffusion to the propagating crack tips. The H-associated decohesion mechanisms are supported by a comparison with the fracture behavior in samples loaded under the cryogenic temperature and can be explained based on dislocation pileups and elastic misfit at the GB κ-carbide/matrix interfaces. The roles of other plasticity-associated H embrittlement mechanisms are also discussed in this work based on careful investigations of the dislocation activities near the H-induced cracks. Possible alloying and microstructure design strategies for the enhancement of the H embrittlement resistance in this alloy family are also suggested. © 2022
    view abstractdoi: 10.1016/j.actamat.2022.118392
  • 2022 • 1105 Transient Spin Injection Efficiencies at Ferromagnet–Metal Interfaces
    Elliott, P. and Eschenlohr, A. and Chen, J. and Shallcross, S. and Bovensiepen, U. and Dewhurst, J.K. and Sharma, S.
    Advanced Materials Interfaces (2022)
    doi: 10.1002/admi.202201233
  • 2022 • 1104 On the Application of Calcium Phosphate Micro- and Nanoparticles as Food Additive
    Enax, J. and Meyer, F. and Schulze zur Wiesche, E. and Epple, M.
    Nanomaterials 12 (2022)
    doi: 10.3390/nano12224075
  • 2022 • 1103 A-posteriori assessment of Large-Eddy Simulation subgrid-closures for momentum and scalar fluxes in a turbulent premixed burner experiment
    Engelmann, L. and Hasslberger, J. and Inanc, E. and Klein, M. and Kempf, A.
    Computers and Fluids 240 (2022)
    Although overall increasing computing power allows for higher resolution in Large-Eddy Simulation (LES), an appropriate choice of the subgrid-model is still decisive for the simulation quality. The relevance of the subgrid-model increases even further, if transported quantities are used in additional thermo-chemical models, which are coupled to the flow field. The present study investigates the impact of the choice of the subgrid-model for reactive flows in LES in the context of tabulated chemistry using well known and recently suggested modifications of eddy viscosity and scale-similarity-type models. LES calculations of the well investigated Cambridge stratified swirl burner have been performed with flamelet generated manifolds in combination with artificial flame-thickening. The simulations have been compared with flame-resolved results using the same numerical setup. Encouraging results have been obtained for a regularized scale-similarity-type model (applied to momentum- and scalar-fluxes). The sensor-enhanced Smagorinsky model outperforms well known eddy viscosity models while maintaining stability and being straight forward to implement with very low computational overhead compared to the static Smagorinsky model. © 2022 Elsevier Ltd
    view abstractdoi: 10.1016/j.compfluid.2022.105441
  • 2022 • 1102 Cyclic Variations in the Flame Propagation in an Spark-Ignited Engine: Multi Cycle Large Eddy Simulation Supported by Imaging Diagnostics
    Engelmann, L. and Laichter, J. and Wollny, P. and Klein, M. and Kaiser, S.A. and Kempf, A.M.
    Flow, Turbulence and Combustion (2022)
    Experimental measurements and multi-cycle large eddy simulation (LES) are performed in an optically accessible four-stroke spark-ignition engine to investigate cycle-to-cycle variations (CCV). High-speed combustion imaging is used to measure the early flame propagation and obtain the flame radius and centroids. Large Eddy Simulation generates data-bases for the flame propagation as well as the kinetic energy in the cylinder and confirms the observations from the two-dimensional fields by three-dimensional simulation results. Experiment and simulation are compared with respect to the strength and distribution of CCV. Both approaches reveal CCV causing similar statistics of maximum pressures and combustion speeds. The cycles are categorized as slow and fast cycles using the crank angle of ten percent burnt fuel-mixture. Analysis of the flame centroids shows that slow cycles move further towards the intake-side of the engine compared to fast cycles. The kinetic energy during combustion is averaged for the slow and fast cycles based on the samples being in unburnt and burnt mixture. Studying the kinetic energy level in the unburnt and burnt mixture reveals higher turbulent kinetic energy for the fast cycles as well as larger separation between the global kinetic and the turbulent kinetic energy for the slow cycles, providing evidence for a source of the CCV variations observed in this engine. © 2022, The Author(s).
    view abstractdoi: 10.1007/s10494-022-00350-w
  • 2022 • 1101 A Reverse Osmosis Process to Recover and Recycle Trivalent Chromium from Electroplating Wastewater
    Engstler, R. and Reipert, J. and Karimi, S. and Vukušić, J.L. and Heinzler, F. and Davies, P. and Ulbricht, M. and Barbe, S.
    Membranes 12 (2022)
    Electroplating generates high volumes of rinse water that is contaminated with heavy metals. This study presents an approach for direct metal recovery and recycling from simulated rinse water, made up of an electroplating electrolyte used in industry, using reverse osmosis (RO). To simulate the real industrial application, the process was examined at various permeate fluxes, ranging from 3.75 to 30 L·m−2·h−1 and hydraulic pressures up to 80 bar. Although permeance decreased significantly with increasing water recovery, rejections of up to 93.8% for boric acid, &gt;99.9% for chromium and 99.6% for sulfate were observed. The final RO retentate contained 8.40 g/L chromium and was directly used in Hull cell electroplating tests. It was possible to deposit cold-hued chromium layers under a wide range of relevant current densities, demonstrating the reusability of the concentrate of the rinsing water obtained by RO. © 2022 by the authors.
    view abstractdoi: 10.3390/membranes12090853
  • 2022 • 1100 Prevention of Caries and Dental Erosion by Fluorides—A Critical Discussion Based on Physico-Chemical Data and Principles
    Epple, M. and Enax, J. and Meyer, F.
    Dentistry Journal 10 (2022)
    Dental erosion is a common problem in dentistry. It is defined as the loss of tooth mineral by the attack of acids that do not result from caries. From a physico-chemical point of view, the nature of the corroding acids only plays a minor role. A protective effect of fluorides, to prevent caries and dental erosion, is frequently claimed in the literature. The proposed modes of action of fluorides include, for example, the formation of an acid-resistant fluoride-rich surface layer and a fluoride-induced surface hardening of the tooth surface. We performed a comprehensive literature study on the available data on the interaction between fluoride and tooth surfaces (e.g., by toothpastes or mouthwashes). These data are discussed in the light of general chemical considerations on fluoride incorporation and the acid solubility of teeth. The analytical techniques available to address this question are presented and discussed with respect to their capabilities. In summary, the amount of fluoride that is incorporated into teeth is very low (a few µg mm−2), and is unlikely to protect a tooth against an attack by acids, be it from acidic agents (erosion) or from acid-producing cariogenic bacteria. © 2022 by the authors. Licensee MDPI, Basel, Switzerland.
    view abstractdoi: 10.3390/dj10010006
  • 2022 • 1099 A garden pool in a cold summer - How does it get warm? [Ein Gartenpool im kalten Sommer – wie wird er warm?]
    Epple, M. and Fischer, C. and Loza, K.
    Chemie in Unserer Zeit 56 180-186 (2022)
    doi: 10.1002/ciuz.202100064
  • 2022 • 1098 A switchable DNA origami/plasmonic hybrid device with a precisely tuneable DNA-free interparticle gap
    Erkelenz, M. and Kosinski, R. and Giesler, H. and Sritharan, O. and Jose, J. and Saccà, B. and Schlücker, S.
    Chemical Communications 58 13479-13482 (2022)
    doi: 10.1039/d2cc05324a
  • 2022 • 1097 Fundamentals of Nanobiophotonics for Diagnostics and Therapy
    Erkelenz, M. and Schlücker, S.
    World Scientific Series in Nanoscience and Nanotechnology 22 3-39 (2022)
    doi: 10.1142/9789811235252_0001
  • 2022 • 1096 Signatures of Exciton Orbits in Quantum Mechanical Recurrence Spectra of Cu2 O
    Ertl, J. and Marquardt, M. and Schumacher, M. and Rommel, P. and Main, J. and Bayer, M.
    Physical Review Letters 129 (2022)
    doi: 10.1103/PhysRevLett.129.067401
  • 2022 • 1095 Materials for extreme environments
    Eswarappa Prameela, S. and Pollock, T.M. and Raabe, D. and Meyers, M.A. and Aitkaliyeva, A. and Chintersingh, K.-L. and Cordero, Z.C. and Graham-Brady, L.
    Nature Reviews Materials (2022)
    doi: 10.1038/s41578-022-00496-z
  • 2022 • 1094 Particle movement in the spheronizer – Experimental investigations with respect to the toroidal and poloidal direction
    Evers, M. and Weis, D. and Antonyuk, S. and Thommes, M.
    Powder Technology 404 (2022)
    Oberservation of particle movement during wet granulation is crucial for identifying granulation mechanisms, process optimizations and troubleshooting. An example of such a process is spheronization, which is commonly used as a wet granulation technique to produce spherical, pharmaceutical pellets. Due to the dense particle bed, measurements of poloidal pellet velocities remain a challenge and have not been yet been reported in literature. In this work, a modelling approach was used in combination with particle image velocimetry (PIV) and mixing progress as a surrogate parameter to obtain information about the movement inside the pellet bed, including those parts not visible from outside the pellet bed. A good agreement between the experiment and the simulation was found. Regions of low poloidal velocities were found in both experiments and simulations. The initial pellet shape was not identified as a significant influence on the mixing progress. © 2022 Elsevier B.V.
    view abstractdoi: 10.1016/j.powtec.2022.117452
  • 2022 • 1093 Circumventing the OCl versus OOH scaling relation in the chlorine evolution reaction: Beyond dimensionally stable anodes
    Exner, K.S. and Lim, T. and Joo, S.H.
    Current Opinion in Electrochemistry 34 (2022)
    The development of selective electrocatalysts for the chlorine evolution reaction (CER) is majorly restrained by a scaling relation between the OCl and OOH adsorbates, rendering that active CER catalysts are also reasonably active in the competing oxygen evolution reaction (OER). While theory predicts that the OCl versus OOH scaling relation can be circumvented as soon as the elementary reaction steps in the CER comprise the Cl rather than the OCl adsorbate, it was demonstrated recently that PtN4 sites embedded in a carbon nanotube follow this theoretical prediction. Advanced experimental analyses illustrate that the PtN4 sites also reveal a different reaction kinetics compared to the industrial benchmark of dimensionally stable anodes (DSA). A reverse Volmer–Heyrovsky mechanism was identified, in which the rate-determining Volmer step for small overpotentials is followed by the kinetically limiting Heyrovsky step for larger overpotentials. Since the PtN4 sites excel DSA in terms of activity and chlorine selectivity, we suggest the Cl intermediate as well as the reverse Volmer–Heyrovsky mechanism as the design criteria for the development of next-generation electrode materials beyond DSA. © 2022 The Author(s)
    view abstractdoi: 10.1016/j.coelec.2022.100979
  • 2022 • 1092 Beyond the thermodynamic volcano picture in the nitrogen reduction reaction over transition-metal oxides: Implications for materials screening
    Exner, K.S.
    Chinese Journal of Catalysis 43 2871-2880 (2022)
    doi: 10.1016/S1872-2067(21)64025-1
  • 2022 • 1091 On the Optimization of Nitrogen-Reduction Electrocatalysts: Breaking Scaling Relation or Catalytic Resonance Theory?
    Exner, K.S.
    ChemCatChem 14 (2022)
    doi: 10.1002/cctc.202200366
  • 2022 • 1090 Blickpunkt Nachwuchs: Theoretische Elektrokatalyse
    Exner, K.S.
    Nachrichten aus der Chemie 70 82-84 (2022)
    doi: 10.1002/nadc.20224125416
  • 2022 • 1089 A doxorubicin-peptide-gold nanoparticle conjugate as a functionalized drug delivery system: exploring the limits
    Exner, K.S. and Ivanova, A.
    Physical Chemistry Chemical Physics 24 14985-14992 (2022)
    doi: 10.1039/d2cp00707j
  • 2022 • 1088 Teaming up main group metals with metallic iron to boost hydrogenation catalysis
    Färber, C. and Stegner, P. and Zenneck, U. and Knüpfer, C. and Bendt, G. and Schulz, S. and Harder, S.
    Nature Communications 13 (2022)
    Hydrogenation of unsaturated bonds is a key step in both the fine and petrochemical industries. Homogeneous and heterogeneous catalysts are historically based on noble group 9 and 10 metals. Increasing awareness of sustainability drives the replacement of costly, and often harmful, precious metals by abundant 3d-metals or even main group metals. Although not as efficient as noble transition metals, metallic barium was recently found to be a versatile hydrogenation catalyst. Here we show that addition of finely divided Fe0, which itself is a poor hydrogenation catalyst, boosts activities of Ba0 by several orders of magnitude, enabling rapid hydrogenation of alkynes, imines, challenging multi-substituted alkenes and non-activated arenes. Metallic Fe0 also boosts the activity of soluble early main group metal hydride catalysts, or precursors thereto. This synergy originates from cooperativity between a homogeneous, highly reactive, polar main group metal hydride complex and a heterogeneous Fe0 surface that is responsible for substrate activation. © 2022, The Author(s).
    view abstractdoi: 10.1038/s41467-022-30840-4
  • 2022 • 1087 Doping of Nanostructured Co3O4with Cr, Mn, Fe, Ni, and Cu for the Selective Oxidation of 2-Propanol
    Falk, T. and Budiyanto, E. and Dreyer, M. and Büker, J. and Weidenthaler, C. and Behrens, M. and Tüysüz, H. and Muhler, M. and Peng, B.
    ACS Applied Nano Materials 5 17783-17794 (2022)
    doi: 10.1021/acsanm.2c03757
  • 2022 • 1086 Rapid Water Diffusion at Cryogenic Temperatures through an Inchworm-like Mechanism
    Fang, W. and Meyer auf der Heide, K.M. and Zaum, C. and Michaelides, A. and Morgenstern, K.
    Nano Letters 22 340-346 (2022)
    Water diffusion across the surfaces of materials is of importance to disparate processes such as water purification, ice formation, and more. Despite reports of rapid water diffusion on surfaces the molecular level, details of such processes remain unclear. Here, with scanning tunneling microscopy, we observe structural rearrangements and diffusion of water trimers at unexpectedly low temperatures (<10 K) on a copper surface, temperatures at which water monomers or other clusters do not diffuse. Density functional theory calculations reveal a facile trimer diffusion process involving transformations between elongated and almost cyclic conformers in an inchworm-like manner. These subtle intermolecular reorientations maintain an optimal balance of hydrogen-bonding and water–surface interactions throughout the process. This work shows that the diffusion of hydrogen-bonded clusters can occur at exceedingly low temperatures without the need for hydrogen bond breakage or exchange; findings that will influence Ostwald ripening of ice nanoclusters and hydrogen bonded clusters in general. © 2021 American Chemical Society
    view abstractdoi: 10.1021/acs.nanolett.1c03894
  • 2022 • 1085 Wide-Angle Spoof Surface Plasmon Polariton Leaky-Wave Antenna Exploiting Pre-Fractal Structures With Backfire to Nearly Endfire Scanning
    Farokhipour, E. and Sievert, B. and Svejda, J.T. and Rennings, A. and Komjani, N. and Erni, D.
    IEEE Antennas and Wireless Propagation Letters 1-5 (2022)
    doi: 10.1109/LAWP.2022.3199073
  • 2022 • 1084 Beam Steering Leaky-Wave Antenna based on Spoof Surface Plasmon Polaritons for W-band Applications
    Farokhipour, E. and Wang, P.-Y. and Komjani, N. and Erni, D.
    2022 5th International Workshop on Mobile Terahertz Systems, IWMTS 2022 (2022)
    doi: 10.1109/IWMTS54901.2022.9832439
  • 2022 • 1083 Investigation on the crack formation in carbon concrete for the use in deck caps on cantilever slabs of bridges
    Farwig, K. and Schulte-Schrepping, C. and Curbach, M. and Breitenbücher, R.
    Structural Concrete (2022)
    doi: 10.1002/suco.202200298
  • 2022 • 1082 A High-Density Polarized 3He Gas–Jet Target for Laser–Plasma Applications
    Fedorets, P. and Zheng, C. and Engels, R. and Engin, I. and Feilbach, H. and Giesen, U. and Glückler, H. and Kannis, C. and Klehr, F. and Lennartz, M. and Pfeifer, H. and Pfennings, J. and Schneider, C.M. and Schnitzler, N. and S...
    Instruments 6 (2022)
    A laser-driven spin-polarized 3He2+-beam source for nuclear–physics experiments and for the investigation of polarized nuclear fusion demands a high-density polarized 3He gas-jet target. Such a target requires a magnetic system providing a permanent homogeneous holding field for the nuclear spins plus a set of coils for adjusting the orientation of the polarization. Starting from a transport vessel at a maximum pressure of 3 bar, the helium gas is compressed for a short time and can be injected into a laser–interaction chamber through a non-magnetic opening valve and nozzle, thus forming jets with densities of about a few 1019 cm−3 and widths of about 1 mm. The target comprises a 3D adjustment system for precise positioning of the jet relative to the laser focus. An auxiliary gas system provides remote target operation and flushing of the gas lines with Ar gas, which helps to reduce polarization losses. The design of the target, its operation procedures and first experimental results are presented. © 2022 by the authors. Licensee MDPI, Basel, Switzerland.
    view abstractdoi: 10.3390/INSTRUMENTS6020018
  • 2022 • 1081 Element-specific visualization of dynamic magnetic coupling in a Co/Py bilayer microstructure
    Feggeler, T. and Meckenstock, R. and Spoddig, D. and Schöppner, C. and Zingsem, B. and Schaffers, T. and Ohldag, H. and Wende, H. and Farle, M. and Ney, A. and Ollefs, K.
    Scientific Reports 12 (2022)
    doi: 10.1038/s41598-022-23273-y
  • 2022 • 1080 Influence of Core Hole Diameter on Thread Quality for a High-Performance Tapping Technology in AlSi10MnMg Cast Alloys
    Felinks, N. and Krumme, E. and Beer, C. and Hechtle, D. and Sarafraz, Y. and Walther, F. and Biermann, D.
    Procedia CIRP 115 42-47 (2022)
    doi: 10.1016/j.procir.2022.10.047
  • 2022 • 1079 Syntheses of Polypeptides and Their Biomedical Application for Anti-Tumor Drug Delivery
    Feng, H. and Fabrizi, J. and Li, J. and Mayer, C.
    International Journal of Molecular Sciences 23 (2022)
    Polypeptides have attracted considerable attention in recent decades due to their inherent biodegradability and biocompatibility. This mini-review focuses on various ways to synthesize polypeptides, as well as on their biomedical applications as anti-tumor drug carriers over the past five years. Various approaches to preparing polypeptides are summarized, including solid phase peptide synthesis, recombinant DNA techniques, and the polymerization of activated amino acid monomers. More details on the polymerization of specifically activated amino acid monomers, such as amino acid N-carboxyanhydrides (NCAs), amino acid N-thiocarboxyanhydrides (NTAs), and N-phenoxycarbonyl amino acids (NPCs), are introduced. Some stimuli-responsive polypeptide-based drug delivery systems that can undergo different transitions, including stability, surface, and size transition, to realize a better anti-tumor effect, are elaborated upon. Finally, the challenges and opportunities in this field are briefly discussed. © 2022 by the authors. Licensee MDPI, Basel, Switzerland.
    view abstractdoi: 10.3390/ijms23095042
  • 2022 • 1078 Optimization of high performance aerogel concrete [Hochleistungsaerogelbeton – Optimierung, Tragverhalten, Festigkeit]
    Fickler, S. and Heidrich, T. and Welsch, T. and Schnellenbach-Held, M.
    Beton- und Stahlbetonbau 117 498-509 (2022)
    Optimization of High Performance Aerogel Concrete. The development of a new type of high-performance lightweight concrete based on silica aerogels, the so-called high-performance aerogel concrete (HPAC), was reported in [1]. In addition to excellent fire and acoustic protection properties, HPAC shows a very favorable relationship between compressive strength and thermal conductivity and is therefore suitable to produce monolithic exterior walls without additional thermal insulation. In order to expand the possible applications of the new material in construction practice, it has been continuously developed at the Institute for Structural Concrete at the University of Duisburg-Essen since its presentation in 2016. This affects, on the one hand, the optimization of the material with regard to its shrinkage behavior and, on the other hand, the investigation of the load bearing behaviour and the statistical evaluation of the compressive strength. While the first aspect is particularly relevant for the production of reinforced HPAC components, the statistical investigations provide the basis for Finite Element Simulations and the determination of the characteristic strengths. The results of these investigations are reported subsequently. © 2022, Ernst und Sohn. All rights reserved.
    view abstractdoi: 10.1002/best.202200037
  • 2022 • 1077 In-Flight Measurements of Particle Temperature and Velocity with a High-Speed IR Camera During Cold Gas Spraying of In718 and TiAlCrNb
    Fiebig, J. and Gagnon, J.-P. and Mauer, G. and Bakan, E. and Vaßen, R.
    Journal of Thermal Spray Technology 31 2013-2024 (2022)
    Unlike other thermal spraying methods, it is difficult to determine the temperature of the particles during cold gas spraying due to the relatively low radiation. In the present study, the velocities and in-flight temperatures of metal particles were measured during cold gas spraying. A state-of-the-art high-speed infrared camera was used to study the behavior of two different base materials, In718 and TiAlCrNb, both used as structural materials in gas turbine engines. The experiments aimed to improve the fundamental understanding of the process, in particular the heating of the particles, and to compare the experimental results with theoretical calculations of the particle temperatures. © 2022, The Author(s).
    view abstractdoi: 10.1007/s11666-022-01426-9
  • 2022 • 1076 Atomistic Simulation of the Lattice Properties of SnSe
    Filanovich, A.N. and Lysogorskiy, Y.V. and Povzner, A.A.
    Semiconductors 56 169-174 (2022)
    Abstract: A set of ab initio calculations of the energy of the ground state as a function of volume, elastic properties, and phonon spectra of tin selenide in its different crystal modifications has been performed. Based on the data set we obtained, the SnSe interatomic interaction potential has been built by implementing the atomic cluster expansion method. The potential has been used to study the temperature dependences of the thermal and elastic characteristics of SnSe in the quasi-harmonic approximation. © 2022, Pleiades Publishing, Ltd.
    view abstractdoi: 10.1134/S1063782622020051
  • 2022 • 1075 Cross-correlation spectra in interacting quantum dot systems
    Fischer, A. and Kleinjohann, I. and Sinitsyn, N.A. and Anders, F.B.
    Physical Review B 105 (2022)
    Two-color spin-noise spectroscopy of interacting electron spins in singly charged semiconductor quantum dots provides information on the interquantum dot interactions. We investigate the spin cross-correlation function in a quantum dot ensemble employing a modified semiclassical approach. Spin-correlation functions are calculated using a Hamilton quaternion approach that maintains local quantum mechanical properties of the spins. This method takes into account the effects of the nuclear-electric quadrupolar interactions, the randomness of the coupling constants, and the variation of the electron g factor on the spin-noise power spectra. We demonstrate that the quantum dot ensemble can be mapped on an effective two-quantum dot problem and discuss how the characteristic length scale of the interdot interaction modifies the low-frequency cross-correlation spectrum. We argue that details on the interaction strength distribution can be extracted from the cross-correlation spectrum when applying a longitudinal or a transversal external magnetic field. ©2022 American Physical Society
    view abstractdoi: 10.1103/PhysRevB.105.035303
  • 2022 • 1074 Quantum dynamics of disordered arrays of interacting superconducting qubits: Signatures of quantum collective states
    Fistul, M.V. and Neyenhuys, O. and Bocaz, A.B. and Lisitskiy, M. and Eremin, I.M.
    Physical Review B 105 (2022)
    doi: 10.1103/PhysRevB.105.104516
  • 2022 • 1073 Intracavity absorption spectroscopy of HCl isotopes, H2O, CH4, C2H4, and C2H6 in the 3.1-3.4 µm spectral range using a Cr:CdSe laser
    Fjodorow, P. and Frolov, M.P. and Korostelin, Y.V. and Kozlovsky, V.I. and Schulz, C. and Leonov, S.O. and Skasyrsky, Y.K. and Yuryshev, N.N.
    Optics Express 30 40347-40356 (2022)
    We demonstrate the first application of a Cr:CdSe laser for highly-sensitive multicomponent intracavity absorption spectroscopy around λ = 3.1-3.4 µm. A detection scheme based on an integrated recording of multiple (∼70) individual Cr:CdSe laser pulses after a single pump-pulse excitation is reported. The sensitivity of our system corresponds to an effective absorption path length of Leff ≈ 850 m. Exemplary measurements of atmospheric H2O and CH4, and additionally introduced gas-phase HCl, C2H4, or C2H6 are presented. The achieved noise-equivalent detection limits are in the ppb range. Possibilities for further sensitivity enhancement by up to a factor of 104 are discussed. © 2022 Optica Publishing Group under the terms of the Optica Open Access Publishing Agreement.
    view abstractdoi: 10.1364/OE.471851
  • 2022 • 1072 Mass Transport via In-Plane Nanopores in Graphene Oxide Membranes
    Foller, T. and Madauß, L. and Ji, D. and Ren, X. and De Silva, K.K.H. and Musso, T. and Yoshimura, M. and Lebius, H. and Benyagoub, A. and Kumar, P.V. and Schleberger, M. and Joshi, R.
    Nano Letters 22 4941-4948 (2022)
    Angstrom-confined solvents in 2D laminates can travel through interlayer spacings, through gaps between adjacent sheets, and via in-plane pores. Among these, experimental access to investigate the mass transport through in-plane pores is lacking. Our experiments allow an understanding of this mass transport via the controlled variation of oxygen functionalities, size and density of in-plane pores in graphene oxide membranes. Contrary to expectations, our transport experiments show that higher in-plane pore densities may not necessarily lead to higher water permeability. We observed that membranes with a high in-plane pore density but a low amount of oxygen functionalities exhibit a complete blockage of water. However, when water-ethanol mixtures with a weaker hydrogen network are used, these membranes show an enhanced permeation. Our combined experimental and computational results suggest that the transport mechanism is governed by the attraction of the solvents toward the pores with functional groups and hindered by the strong hydrogen network of water formed under angstrom confinement. © 2022 The Authors. Published by American Chemical Society.
    view abstractdoi: 10.1021/acs.nanolett.2c01615
  • 2022 • 1071 Investigating spray flames for nanoparticle synthesis via tomographic imaging using multi-simultaneous measurements (TIMes) of emission
    Foo, C.T. and Unterberger, A. and Martins, F.J.W.A. and Prenting, M.M. and Schulz, C. and Mohri, K.
    Optics Express 30 15524-15545 (2022)
    doi: 10.1364/OE.449269
  • 2022 • 1070 Synthesis of freestanding few-layer graphene in microwave plasma: The role of oxygen
    Fortugno, P. and Musikhin, S. and Shi, X. and Wang, H. and Wiggers, H. and Schulz, C.
    Carbon 186 560-573 (2022)
    We systematically studied the role of oxygen in gas-phase synthesis of graphene in atmospheric hydrocarbon-fed microwave plasmas. Oxygen is introduced through the use of alcohols, and mixtures of ethylene and water. These reactants were contrasted with oxygen-free hydrocarbon reactants, including ethylene and toluene. Solid materials were collected at the plasma reactor exit and characterized. Gas-phase temperature and key species concentrations were measured using in situ Fourier-transform infrared absorption and emission spectroscopy inside the reactors. Ethanol resulted in pure few-layer graphene formation, in agreement with previous studies. In contrast, ethylene fed at the same flow rate produced a mixture of carbon allotropes. A shift towards graphene formation is observed when water is added to ethylene, or when the flow rate of ethylene is cut to half. Simulations suggest that reactants undergo rapid chemical reactions in the plasma front and the mixture composition in and immediately after the plasma is in chemical equilibrium. The primary factor that controls graphene growth appears to be the total amount of carbon available in the growth region. Oxygen, through CO formation, modulates the amount of acetylene and other growth species, while other factors require further study. © 2021 The Authors
    view abstractdoi: 10.1016/j.carbon.2021.10.047
  • 2022 • 1069 Elastoresistivity in the incommensurate charge density wave phase of BaNi2(As1−xPx)2
    Frachet, M. and Wiecki, P. and Lacmann, T. and Souliou, S.M. and Willa, K. and Meingast, C. and Merz, M. and Haghighirad, A.-A. and Le Tacon, M. and Böhmer, A.E.
    npj Quantum Materials 7 (2022)
    doi: 10.1038/s41535-022-00525-8
  • 2022 • 1068 Light-driven in vitro catalysis with photosynthetic biohybrids [Lichtgetriebene in vitro-Katalyse mit photosynthetischen Biohybriden]
    Frank, A. and Conzuelo, F. and Schuhmann, W. and Nowaczyk, M.M.
    BioSpektrum 28 546-548 (2022)
    The use of photosynthetic biohybrids to drive redox reactions in vitro is a promising strategy due to the natural abundance and high quantum efficiency of the bio-components. Here, we present different tools for the fabrication of photosystem I-based biohybrid devices by using redox-active polymers, 3D-structured electrodes as well as additional light-harvesting antennae modules. © 2022, Die Autorinnen und Autoren.
    view abstractdoi: 10.1007/s12268-022-1808-4
  • 2022 • 1067 Reliability-based optimization of structural topologies using artificial neural networks
    Freitag, S. and Peters, S. and Edler, P. and Meschke, G.
    Probabilistic Engineering Mechanics (2022)
    In this paper, a topology optimization approach is presented, where uncertain load and uncertain material parameters are considered. The concept of compliance minimization, i.e., stiffness maximization, is applied based on a plane stress finite element formulation. In order to take uncertain structural load parameters and uncertain material behavior into account, the topology optimization is embedded into a reliability-based design optimization approach. Uncertain structural parameters and design variables are quantified as random variables, intervals and probability boxes (p-boxes). This allows to consider aleatory and epistemic uncertainties by means of polymorphic uncertainty models within the topology optimization. Solving optimization problems with random variables, intervals and p-boxes leads to a high computational effort, because the objective functions and constraints have to evaluated millions of times. To speed up the optimization process, the finite element simulation of the topology optimization is replaced by artificial neural networks. This includes the topology dependent maximal stresses and displacements of the structure, which are used as constraints, and also the material density distribution inside the design domain. The reliability-based optimization of structural topologies approach is applied to a cantilever structure and a single span girder. © 2022 Elsevier Ltd
    view abstractdoi: 10.1016/j.probengmech.2022.103356
  • 2022 • 1066 Quantification of gas-accessible microporosity in metal-organic framework glasses
    Frentzel-Beyme, L. and Kolodzeiski, P. and Weiß, J.-B. and Schneemann, A. and Henke, S.
    Nature Communications 13 (2022)
    doi: 10.1038/s41467-022-35372-5
  • 2022 • 1065 Fuel-Rich Natural Gas Conversion in HCCI Engines with Ozone and Dimethyl Ether as Ignition Promoters: A Kinetic and Exergetic Analysis
    Freund, D. and Horn, C. and Atakan, B.
    Notes on Numerical Fluid Mechanics and Multidisciplinary Design 152 47-65 (2022)
    Fuel-rich operated HCCI engines are suitable for the polygeneration of work, heat, and base chemicals like synthesis gas (CO + H2). Under favorable conditions, these engines are exergetically more efficient than separate steam reformer and cogeneration gas engines. However, to achieve ignition, reactive fuel additives like dimethyl ether or ozone must be supplied, which have some, probably negative and not yet quantified, impacts on the exergetic efficiency. Therefore, the aim of this work is to compute and evaluate the effect of DME and ozone on the exergy input and exergetic efficiency of fuel-rich operated HCCI engines, which convert natural gas at equivalence ratios of 1.5 to 2.5. Results of a single-zone-model (SZM) and a multi-zone model (MZM) are compared to analyze the influence of inhomogeneities in the cylinder on the system’s exergetic efficiency. Natural gas as fuel is compared with previous neat methane results. The single-zone model results show that natural gas is much more reactive than methane. Ethane and propane convert partially in the compression stroke and lead to ethene, propene, and OH radicals. However, the ethane and propane conversions do not favor but slightly reduce the formation of methyl hydroperoxide, which is an important buffer molecule for fuel-rich methane ignition. But in addition, further buffer molecules like ethene or ethyl hydroperoxide are intermediately formed. The product selectivities are neither influenced by the natural gas composition, nor by the chosen additive. Compared to ozone, the DME molar and mass fractions needed for ignition are up to 11 times higher, and its exergy contribution to the total mixture is even 95 times higher. Therefore, the system’s exergetic efficiency is much higher when ozone is chosen as additive: reasonable values of up to 82.8% are possible, compared to 67.7% with DME. The multi-zone model results show that the efficiency is strongly dependent on the fuel conversion and thus unconverted fuel should be recycled within the polygeneration system to maintain high efficiencies. Comparing the total exergetic efficiency, ozone is a favorable additive for fuel-rich operated HCCI polygeneration. © 2022, The Author(s), under exclusive license to Springer Nature Switzerland AG.
    view abstractdoi: 10.1007/978-3-030-90727-3_4
  • 2022 • 1064 Limitations of empirical supercell extrapolation for calculations of point defects in bulk, at surfaces, and in two-dimensional materials
    Freysoldt, C. and Neugebauer, J. and Tan, A.M.Z. and Hennig, R.G.
    Physical Review B 105 (2022)
    The commonly employed supercell approach for defects in crystalline materials may introduce spurious interactions between the defect and its periodic images. A rich literature is available on how the interaction energies can be estimated, reduced, or corrected. A simple and seemingly straightforward approach is to extrapolate from a series of finite supercell sizes to the infinite-size limit, assuming a smooth polynomial dependence of the energy on inverse supercell size. In this work, we demonstrate by means of explict density-functional theory supercell calculations and simplified models that wave-function overlap and electrostatic interactions lead to more complex dependencies on supercell size than commonly assumed. We show that this complexity cannot be captured by the simple extrapolation approaches and that suitable correction schemes should be employed. Published by the American Physical Society
    view abstractdoi: 10.1103/PhysRevB.105.014103
  • 2022 • 1063 Dual phase patterning during a congruent grain boundary phase transition in elemental copper
    Frommeyer, L. and Brink, T. and Freitas, R. and Frolov, T. and Dehm, G. and Liebscher, C.H.
    Nature Communications 13 (2022)
    doi: 10.1038/s41467-022-30922-3
  • 2022 • 1062 Characterization of a robot-assisted UV-C disinfection for the inactivation of surface-associated microorganisms and viruses
    Fuchs, F.M. and Bibinov, N. and Blanco, E.V. and Pfaender, S. and Theiß, S. and Wolter, H. and Awakowicz, P.
    Journal of Photochemistry and Photobiology 11 (2022)
    doi: 10.1016/j.jpap.2022.100123
  • 2022 • 1061 Characterizing Localized Microstructural Deformation of Multiphase Steel by Crystal Plasticity Simulation with Multi-Constitutive Law [複数の材料構成則を用いた結晶塑性解析による複相組織鋼の局所変形挙動評価]
    Fujita, N. and Yasuda, K. and Ishikawa, N. and Diehl, M. and Roters, F. and Raabe, D.
    Journal of the Japan Society for Technology of Plasticity 63 1-8 (2022)
    The demand for safety and reliability in pipelines has been increasing steadily. Dual-phase steels, especially with a bainite matrix and a well-dispersed martensite–austenite constituent (MA), provide ingredients necessary for the improvement of the yield ratio and toughness. To design alloy elements and ensure that dual-phase steels have the required mechanical properties, an understanding of the governing microscopic deformation mechanisms is essential. For this purpose, multi-constitutive crystal plasticity simulation coupled with local strain/stress partitioning, ductile damage and transformation-induced plasticity evolution was employed. Microstructural cell responses were captured by fast Fourier transform crystal plasticity analysis. Representative microstructural patches with the same high spatial resolution as those obtained by electron backscatter diffraction (EBSD) tomography provide new insights into the deformation mechanism in dual-phase microstructures, especially regarding the effects of the matrix and secondary phase distribution on the strain, ductile damage and transformation localization behavior. © 2022 Japan Society for Technology of Plasticity. All rights reserved.
    view abstractdoi: 10.9773/sosei.63.1
  • 2022 • 1060 A Compact Overmoded Waveguide Test Environment: Investigation of Propagation Behaviour
    Funk, M. and Dahl, C. and Barowski, J. and Rolfes, I. and Schulz, C.
    Asia-Pacific Microwave Conference Proceedings, APMC 2022-November 470-472 (2022)
  • 2022 • 1059 A Broadband Test Environment Concept for FMCW Radars based on Overmoded Waveguides
    Funk, M. and Dahl, C. and Barowski, J. and Rolfes, I. and Schulz, C.
    2022 19th European Radar Conference, EuRAD 2022 245-248 (2022)
    doi: 10.23919/EuRAD54643.2022.9924735
  • 2022 • 1058 Oxidation of oxymethylene ether (OME0−5): An experimental systematic study by mass spectrometry and photoelectron photoion coincidence spectroscopy
    Gaiser, N. and Bierkandt, T. and Oßwald, P. and Zinsmeister, J. and Kathrotia, T. and Shaqiri, S. and Hemberger, P. and Kasper, T. and Aigner, M. and Köhler, M.
    Fuel 313 (2022)
    This paper presents a systematic study of oxymethylene ethers (OMEs) oxidation in an atmospheric laminar flow reactor setup. Oxymethylene ethers with different number of oxymethylene ether groups (n = 0–5) have been investigated under lean and rich conditions (750–1250 K). The flow reactor is coupled to an electron ionization molecular-beam mass spectrometer (EI-MBMS) with high mass resolution to measure speciation data. Additional isomer-selective speciation analysis was performed using a novel atmospheric laminar flow reactor combined with double-imaging photoelectron photoion coincidence (i2PEPICO) spectroscopy at the vacuum ultraviolet radiation (VUV) beamline of the Swiss Light Source. The results show a dominance of oxygenated intermediates during the combustion of all OMEs in the investigated temperature regime. The observed species pool is thereby nearly independent of the OME's chain length. In particular the presence of significant fractions of ethanol is remarkable and indicates unknown or underestimated reaction pathways to form C–C bonds from OME structures. Formation of combustion intermediates during oxidation of longer OMEs occurs at lower temperatures and correlates with the ignition delay time. No hydrocarbons with more than four carbon atoms are detected. The combination of high mass resolution provided by EI-MBMS detection and isomer-selective analysis by i2PEPICO enables a complete overview of all intermediates. This allows for in-depth discussion and analysis of systematic trends for several intermediate species. © 2021 Elsevier Ltd
    view abstractdoi: 10.1016/j.fuel.2021.122650
  • 2022 • 1057 Investigation of the combustion chemistry in laminar, low-pressure oxymethylene ether flames (OME0–4)
    Gaiser, N. and Zhang, H. and Bierkandt, T. and Schmitt, S. and Zinsmeister, J. and Kathrotia, T. and Hemberger, P. and Shaqiri, S. and Kasper, T. and Aigner, M. and Oßwald, P. and Köhler, M.
    Combustion and Flame (2022)
    Quantitative speciation data for alternative fuels is highly desired to assess their emission potential and to develop and validate chemical kinetic models. In terms of substitute choices for fossil diesel are oxymethylene ethers (OMEs) strongly discussed. Due to the absence of carbon-carbon bonds, soot emissions from combustion of OMEs are low, but significant emissions of unregulated pollutants such as aldehydes emerge. The combustion behavior of OME fuels with different chain lengths, OME0–4, was investigated in laminar premixed low-pressure flames using complementary molecular-beam mass spectrometry (MBMS) techniques. MBMS sampling provides an in-situ access directly into the reaction zone of the flame. Almost all chemical species involved in the oxidation process can be detected and quantified simultaneously. Neat OME0–3 flames were analyzed by electron ionization (EI) MBMS with high mass resolution (R ≈ 3900) providing exact elementary composition. To obtain isomer-specific information, an OME1-doped hydrogen flame and a stochiometric OME4 flame were studied by double-imaging photoelectron photoion coincidence (i2PEPICO) spectroscopy. Both, EI-MBMS detection and i2PEPICO spectroscopy, enables a complete overview of all intermediates. The results show a dominance of oxygenated intermediates for all measured conditions. Mole fraction profiles for the most important species are presented (i.e. formaldehyde, methanol, methyl formate and formic acid) and compared to modeling results. Hydrocarbons with more than four carbon atoms were not detected under the investigated conditions. Isomers such as ethanol/dimethyl ether (m/z = 46) and ethenol/acetaldehyde (m/z = 44) could be separated using threshold photoelectron spectra for clear identification and photoionization efficiency curves for quantification. This investigation permits the discussion and analysis of systematic trends, including intermediate species, for the combustion of the studied series of oxymethylene ether fuels. © 2022 The Combustion Institute
    view abstractdoi: 10.1016/j.combustflame.2022.112060
  • 2022 • 1056 Oxidation of linear and branched ethers: A comparative flow reactor study of OME2 and trimethoxymethane
    Gaiser, N. and Bierkandt, T. and Oßwald, P. and Zinsmeister, J. and Hemberger, P. and Shaqiri, S. and Aigner, M. and Kasper, T. and Köhler, M.
    Proceedings of the Combustion Institute (2022)
    doi: 10.1016/j.proci.2022.08.112
  • 2022 • 1055 Assessing the Influence of Betaine-Based Natural Deep Eutectic Systems on Horseradish Peroxidase
    Gajardo-Parra, N.F. and Meneses, L. and Duarte, A.R.C. and Paiva, A. and Held, C.
    ACS Sustainable Chemistry and Engineering 10 12873-12881 (2022)
    doi: 10.1021/acssuschemeng.2c04045
  • 2022 • 1054 Osmolyte effect on enzymatic stability and reaction equilibrium of formate dehydrogenase
    Gajardo-Parra, N.F. and Akrofi-Mantey, H. and Ascani, M. and Cea-Klapp, E. and Garrido, J.M. and Sadowski, G. and Held, C.
    Physical Chemistry Chemical Physics 24 27930-27939 (2022)
    doi: 10.1039/d2cp04011e
  • 2022 • 1053 Regulation of photo triggered cytotoxicity in electrospun nanomaterials: role of photosensitizer binding mode and polymer identity
    Galstyan, A. and Majiya, H. and Dobrindt, U.
    Nanoscale Advances 4 200-210 (2022)
    Although electrospun nanomaterials containing photoactive dyes currently compete with the present state of art antimicrobial materials, relatively few structure-activity relationships have been established to identify the role of carrier polymer and photosensitizer binding mode on the performance of the materials. In this study scaffolds composed of poly(vinyl alcohol), polyacrylonitrile, poly(caprolactone), and tailor-made phthalocyanine-based photosensitizers are developed utilizing electrospinning as a simple, time and cost-effective method. The photoinduced activity of nanofibrous materials was characterizedin vitroagainstE. coliandB. subtilisas models for Gram-negative and Gram-positive bacteria respectively, as well as against bacteriophages phi6 and MS2 as models for enveloped and non-enveloped viruses respectively. For the first time, we show how polymer-specific properties affect antifouling and antimicrobial activity of the nanofibrous material, indicating that the most promising way to increase efficiency is likelyviamethods that focus on increasing the number of short, but strong and reversible bacteria-surface interactions. © The Royal Society of Chemistry 2021.
    view abstractdoi: 10.1039/d1na00717c
  • 2022 • 1052 Influence of photosensitizer concentration and polymer composition on photoinduced antimicrobial activity of PVA- and PVA-chitosan-based electrospun nanomaterials cross-linked with tailor-made silicon(IV) phthalocyanine
    Galstyan, A. and Strokov, K.
    Photochemical and Photobiological Sciences (2022)
    The ongoing effort to eradicate pathogenic bacteria and viruses is a major endeavor that requires development of new and innovative materials. Materials based on photodynamic action represent an emerging and attractive area of research, and therefore, a broad understanding of chemical design principles is required. In the present study, we investigated the antibacterial and antiviral activities of five different nanofibrous membranes composed of poly(vinyl alcohol) or poly(vinyl alcohol)-chitosan mixture cross-linked through silicon(IV)phthalocyanine derivative with the aim to identify the role of the carrier polymer and photosensitizers concentration on its efficacy. A straightforward cross-linking process was adopted to create a water-stable material with an almost uniform distribution of the fiber structure, as revealed by scanning electron microscopy. The results of the antimicrobial studies showed that the increase in the amount of chitosan in the polymer mixture, rather than the increase in the photosensitizer concentration, enhanced the activity of the material. Due to their visible light-triggered antimicrobial activity, the resulting materials provide valuable opportunities for both topical antimicrobial photodynamic therapy and the area of environmental remediation. Graphical abstract: [Figure not available: see fulltext.] © 2022, The Author(s).
    view abstractdoi: 10.1007/s43630-022-00229-9
  • 2022 • 1051 Smartes mit Singulett-Sauerstoff
    Galstyan, A.
    Nachrichten aus der Chemie 70 65-70 (2022)
    doi: 10.1002/nadc.20224119950
  • 2022 • 1050 Manufacturing of W/steel composites using electro-discharge sintering process
    Ganesh, V. and Leich, L. and Dorow-Gerspach, D. and Heuer, S. and Coenen, J.W. and Wirtz, M. and Pintsuk, G. and Gormann, F. and Lied, P. and Baumgärtner, S. and Theisen, W. and Linsmeier, C.
    Nuclear Materials and Energy 30 (2022)
    Tungsten-steel metal matrix composites are consolidated using electro-discharge sintering. At first steel and tungsten powders are sintered separately and then 25 vol% W, 50 vol% W and 75 vol% W mixed powders are sintered. A thorough process parametric study is carried out involving analysis of the influence of particle size distribution, sintering pressure, and discharge energy on the maximum discharge current and obtained residual porosity. Thermal expansion coefficient and the specific heat capacity of the optimized sintered composites are almost same as their theoretical values, however the thermal conductivities and the mechanical properties are lower than the expected values. © 2021 The Authors
    view abstractdoi: 10.1016/j.nme.2021.101089
  • 2022 • 1049 Identification of a novel homozygous synthesis of cytochrome c oxidase 2 variant in siblings with early-onset axonal Charcot-Marie-Tooth disease
    Gangfuß, A. and Hentschel, A. and Rademacher, N. and Sickmann, A. and Stüve, B. and Horvath, R. and Gross, C. and Kohlschmidt, N. and Förster, F. and Abicht, A. and Schänzer, A. and Schara-Schmidt, U. and Roos, A. and Della Marina, A.
    Human Mutation (2022)
    The synthesis of cytochrome c oxidase 2 (SCO2) gene encodes for a mitochondrial located metallochaperone essential for the synthesis of the cytochrome c oxidase (COX) subunit 2. Recessive mutations in SCO2 have been reported in several cases with fatal infantile cardioencephalomyopathy with COX deficiency and in only four cases with axonal neuropathy. Here, we identified a homozygous pathogenic variant (c.361G &gt; C; p.[Gly121Arg]) in SCO2 in two brothers with isolated axonal motor neuropathy. To address pathogenicity of the amino acid substitution, biochemical studies were performed and revealed increased level of the mutant SCO2-protein and dysregulation of COX subunits in leukocytes and moreover unraveled decrease of proteins involved in the manifestation of neuropathies. Hence, our combined data strengthen the concept of SCO2 being causative for a very rare form of axonal neuropathy, expand its molecular genetic spectrum and provide first biochemical insights into the underlying pathophysiology. © 2022 The Authors. Human Mutation published by Wiley Periodicals LLC.
    view abstractdoi: 10.1002/humu.24338
  • 2022 • 1048 Proteomic and morphological insights and clinical presentation of two young patients with novel mutations of BVES (POPDC1)
    Gangfuß, A. and Hentschel, A. and Heil, L. and Gonzalez, M. and Schönecker, A. and Depienne, C. and Nishimura, A. and Zengeler, D. and Kohlschmidt, N. and Sickmann, A. and Schara-Schmidt, U. and Fürst, D.O. and van der Ven, P.F...
    Molecular Genetics and Metabolism 136 226-237 (2022)
    Popeye domain containing protein 1 (POPDC1) is a highly conserved transmembrane protein essential for striated muscle function and homeostasis. Pathogenic variants in the gene encoding POPDC1 (BVES, Blood vessel epicardial substance) are causative for limb-girdle muscular dystrophy (LGMDR25), associated with cardiac arrhythmia. We report on four affected children (age 7–19 years) from two consanguineous families with two novel pathogenic variants in BVES c.457C>T(p.Q153X) and c.578T>G (p.I193S). Detailed analyses were performed on muscle biopsies from an affected patient of each family including immunofluorescence, electron microscopy and proteomic profiling. Cardiac abnormalities were present in all patients and serum creatine kinase (CK) values were variably elevated despite lack of overt muscle weakness. Detailed histological analysis of skeletal muscle, however indicated a myopathy with reduced sarcolemmal expression of POPDC1 accompanied by altered sarcolemmal and sarcoplasmatic dysferlin and Xin/XIRP1 abundance. At the electron microscopic level, the muscle fiber membrane was focally disrupted. The proteomic signature showed statistically significant dysregulation of 191 proteins of which 173 were increased and 18 were decreased. Gene ontology-term analysis of affected biological processes revealed - among others - perturbation of muscle fibril assembly, myofilament sliding, and contraction as well as transition between fast and slow fibers. In conclusion, these findings demonstrate that the phenotype of LGMDR25 is highly variable and also includes younger children with conduction abnormalities, no apparent muscular problems, and only mildly elevated CK values. Biochemical studies suggest that BVES mutations causing loss of functional POPDC1 can impede striated muscle function by several mechanisms. © 2022 Elsevier Inc.
    view abstractdoi: 10.1016/j.ymgme.2022.05.005
  • 2022 • 1047 8.0% Efficient Submicron CuIn(S,Se)2Solar Cells on Sn:In2O3Back Contact via a Facile Solution Process
    Gao, Y. and Yin, G. and Li, Y. and Köhler, T. and Lucaßen, J. and Schmid, M.
    ACS Applied Energy Materials 5 12252-12260 (2022)
    High-performance chalcopyrite solar cells have been fabricated on transparent conductive oxide (TCO) back contact through an environmentally benign solution, showing great potential for bifacial application. Ultrathin (around 550 nm) CuIn(S,Se)2 (CISSe) solar cells were successfully deposited on Sn:In2O3 (ITO) back contact via spin-coating of metal-chloride N,N-dimethylformamide (DMF) solution, followed by selenization. The ultrathin devices achieved a conversion efficiency of 7.5% when the precursor film was selenized at 520 °C. With the increase in the absorber thickness to submicron (740 nm), the solar cells exhibited not only a higher short-circuit current density but also an improved fill factor compared to the ultrathin devices, which resulted in an efficiency enhancement to 7.9%. Furthermore, NaCl solution preselenization treatment was demonstrated to improve the performance of CISSe solar cells. When the submicron absorber was subject to 1 M NaCl solution prior to selenization, an 8.0% efficient CISSe device was achieved. To the best of our knowledge, this is the topmost performance for submicron CISSe solar cells fabricated from solution-based precursors on TCO back contact. © 2022 American Chemical Society.
    view abstractdoi: 10.1021/acsaem.2c01764
  • 2022 • 1046 Cobalt ferrite nanoparticles for tumor therapy: Effective heating versus possible toxicity
    Garanina, A.S. and Nikitin, A.A. and Abakumova, T.O. and Semkina, A.S. and Prelovskaya, A.O. and Naumenko, V.A. and Erofeev, A.S. and Gorelkin, P.V. and Majouga, A.G. and Abakumov, M.A. and Wiedwald, U.
    Nanomaterials 12 (2022)
    Magnetic nanoparticles (MNPs) are widely considered for cancer treatment, in particular for magnetic hyperthermia (MHT). Thereby, MNPs are still being optimized for lowest possible toxicity on organisms while the magnetic properties are matched for best heating capabilities. In this study, the biocompatibility of 12 nm cobalt ferrite MNPs, functionalized with citrate ions, in different dosages on mice and rats of both sexes was investigated for 30 days after intraperitoneal injection. The animals’ weight, behavior, and blood cells changes, as well as blood biochemical parameters are correlated to histological examination of organs revealing that cobalt ferrite MNPs do not have toxic effects at concentrations close to those used previously for efficient MHT. Moreover, these MNPs demonstrated high specific loss power (SLP) of about 400 W g−1. Importantly the MNPs retained their magnetic properties inside tumor tissue after intratumoral administration for several MHT cycles within three days. Thus, cobalt ferrite MNPs represent a perspective platform for tumor therapy by MHT due to their ability to provide effective heating without exerting a toxic effect on the organism. This opens up new avenues for smaller MNPs sizes while their heating efficiency is maintained. © 2021 by the authors. Licensee MDPI, Basel, Switzerland.
    view abstractdoi: 10.3390/nano12010038
  • 2022 • 1045 Investigation of the Influence of Surface Roughness on Reflective THz Measurements
    Gassel, S.T. and Azih, D.A. and Hofmann, M.R. and Brenner, C.
    International Conference on Infrared, Millimeter, and Terahertz Waves, IRMMW-THz 2022-August (2022)
    doi: 10.1109/IRMMW-THz50927.2022.9895793
  • 2022 • 1044 Voltammetric Behaviour of LMO at the Nanoscale: A Map of Reversibility and Diffusional Limitations
    Gavilán-Arriazu, E.M. and Mercer, M.P. and Barraco, D.E. and Hoster, H.E. and Leiva, E.P.M.
    ChemPhysChem 23 (2022)
    Understanding and optimizing single particle rate behaviour is normally challenging in composite commercial lithium-ion electrode materials. In this regard, recent experimental research has addressed the electrochemical Li-ion intercalation in individual nanosized particles. Here, we present a thorough theoretical analysis of the Li+ intercalation voltammetric behaviour in single nano/micro-scale LiMn2O4 (LMO) particles, incorporating realistic interactions between inserted ions. A transparent 2-dimensional zone diagram representation of kinetic-diffusional behaviour is provided that allows rapid diagnosis of the reversibility and diffusion length of the system depending on the particle geometry. We provide an Excel file where the boundary lines of the zone diagram can be rapidly recalculated by setting input values of the rate constant, (Formula presented.) and diffusion coefficient, (Formula presented.). The model framework elucidates the heterogeneous behaviour of nanosized particles with similar sizes but different shapes. Hence, we present here an outlook for realistic multiscale modelling of real materials. © 2021 Wiley-VCH GmbH.
    view abstractdoi: 10.1002/cphc.202100700
  • 2022 • 1043 Electrochemical CO2 reduction - The macroscopic world of electrode design, reactor concepts & economic aspects
    Gawel, A. and Jaster, T. and Siegmund, D. and Holzmann, J. and Lohmann, H. and Klemm, E. and Apfel, U.-P.
    iScience 25 (2022)
    doi: 10.1016/j.isci.2022.104011
  • 2022 • 1042 Theoretical modeling and prediction of biorelevant solubility of poorly soluble pharmaceuticals
    Ge, K. and Paus, R. and Penner, V. and Sadowski, G. and Ji, Y.
    Chemical Engineering Journal 444 (2022)
    The solubility of active pharmaceutical ingredients (APIs) in biorelevant media is important fundamental data for API formulation design and contributes to better evaluation of in vivo dissolution kinetics. However, these data are mainly determined by experimental measurements, which is rather time and cost consuming. Therefore, it is essential to develop a novel theoretical strategy to describe and predict API solubility in biorelevant media. In this work, the solubilization effect of micelle and the effect of pH as well as ion components on the solubility of naproxen and indomethacin were determined experimentally. A micellar solubilization model and pH-dependent solubility model were proposed to model the effect of various micelles and pH (including buffer components) on API aqueous solubility, respectively. The combination of the two model successfully described the biorelevant solubility of APIs as function of temperature. The proposed strategy could provide insights into the mechanisms of micelle and different pH regulated by different buffer components on API solubility and could accurately describe the solubility of APIs in biorelevant media. This work is expected to provide theoretical guidance for API formulation development. © 2022
    view abstractdoi: 10.1016/j.cej.2022.136678
  • 2022 • 1041 Damage Evolution of Steel Fibre-Reinforced High-Performance Concrete in Low-Cycle Flexural Fatigue: Numerical Modeling and Experimental Validation
    Gebuhr, G. and Pise, M. and Anders, S. and Brands, D. and Schröder, J.
    Materials 15 (2022)
    This contribution aims to analyze the deterioration behaviour of steel fibre-reinforced high-performance concrete (HPC) in both experiments as well as numerical simulations. For this purpose, flexural tensile tests are carried out on beams with different fibre contents and suitable damage indicators are established to describe and calibrate the damage behaviour numerically using a phase-field model approach. In addition to conventional measurement methods, the tests are equipped with acoustic emission sensors in order to obtain a more precise picture of crack evolution by observing acoustic events. It is shown that, in addition to classical damage indicators, such as stiffness degradation and absorbed energy, various acoustic indicators, such as the acoustic energy of individual crack events, can also provide information about the damage progress. For the efficient numerical analysis of the overall material behaviour of fibre-reinforced HPC, a phenomenological material model is developed. The data obtained in the experiments are used to calibrate and validate the numerical model for the simulation of three-point bending beam tests. To verify the efficiency of the presented numerical model, the numerical results are compared with the experimental data, e.g., load-CMOD curves and the degradation of residual stiffness. © 2022 by the authors. Licensee MDPI, Basel, Switzerland.
    view abstractdoi: 10.3390/ma15031179
  • 2022 • 1040 Noncovalent Intra- and Intermolecular Interactions in Peri-Substituted Pnicta Naphthalene and Acenaphthalene Complexes
    Gehlhaar, A. and Wölper, C. and van der Vight, F. and Jansen, G. and Schulz, S.
    European Journal of Inorganic Chemistry 2022 (2022)
    Five peri-substituted naphthalene and acenaphthalene complexes (Ph2Pn)2Naph (E=Sb 1, Bi 3), (Ph2Sb)2Acenaph (2), (Ph2Bi)(Me3Sn)Naph (4) and (PhBiNaph)2 (5) were synthesized and characterized in solution (1H, 13C NMR, IR) and in the solid-state (sc-XRD). 1–5 show different types of noncovalent intermolecular interactions in the solid-state including Naph−H⋅⋅⋅π, π⋅⋅⋅π and Bi⋅⋅⋅π (5) contacts, which were exemplarily (5) quantified by use of density functional theory and local coupled cluster electronic structure theory calculations, demonstrating that the Bi⋅⋅⋅π contact provides the main stabilizing contribution. Symmetry-adapted intermolecular perturbation theory calculations showed that this and other contacts are dominated by London dispersion interactions. © 2021 The Authors. European Journal of Inorganic Chemistry published by Wiley-VCH GmbH
    view abstractdoi: 10.1002/ejic.202100883
  • 2022 • 1039 Bisstibane-distibane conversion via consecutive single-electron oxidation and reduction reaction
    Gehlhaar, A. and Weinert, H.M. and Wölper, C. and Semleit, N. and Haberhauer, G. and Schulz, S.
    Chemical Communications 58 6682-6685 (2022)
    peri-Substituted naphthalene complexes (Trip2Pn)2Naph (Pn = Sb 1, Bi 2) were synthesised and their redox behaviour investigated. Oxidation of 1 with [Fc][BArF] (BArF = B(C6F5)4) yielded [(Trip2Sb)(TripSb)Naph][BArF] (3) containing the stibane-coordinated stibenium cation [(Trip2Sb)(TripSb)Naph]+. Subsequent reduction of 3 with KC8 yielded distibane (TripSb)2Naph (4). 1-4 were characterised by NMR (1H, 13C) and IR spectroscopy as well as single-crystal X-ray diffraction (sc-XRD), while their electronic structures were analysed by quantum chemical computations. © 2022 The Royal Society of Chemistry
    view abstractdoi: 10.1039/d2cc01986h
  • 2022 • 1038 Comparing London dispersion pnictogen-π interactions in naphthyl-substituted dipnictanes
    Gehlhaar, A. and Schiavo, E. and Wölper, C. and Schulte, Y. and Auer, A.A. and Schulz, S.
    Dalton Transactions 51 5016-5023 (2022)
    Using a combination of NMR, single crystal X-ray diffraction (sc-XRD) and quantum chemistry, the structure-directing role of London Dispersion (LD) is demonstrated for dibismuthane Bi2Naph2 (1). 1 shows intermolecular Bi⋯π contacts in the solid-state, while π⋯π interactions as observed in the lighter homologues are missing. Comparison of the whole series of dipnictanes revealed the influence of the pnictogen atom on the strength of London dispersion and highlights its importance in heavy main group element chemistry. © 2022 The Royal Society of Chemistry
    view abstractdoi: 10.1039/d2dt00477a
  • 2022 • 1037 Interactions during the Adsorption of Heterocycles on Zeolites, Silica Gels, and Activated Carbons
    Gehrke, L. and Pfeifer, S. and Bläker, C. and Pasel, C. and Bathen, D.
    Journal of Chemical and Engineering Data 67 3317-3327 (2022)
    doi: 10.1021/acs.jced.2c00286
  • 2022 • 1036 Optimization of Covalent MKK7 Inhibitors via Crude Nanomole-Scale Libraries
    Gehrtz, P. and Marom, S. and Bührmann, M. and Hardick, J. and Kleinbölting, S. and Shraga, A. and Dubiella, C. and Gabizon, R. and Wiese, J.N. and Müller, M.P. and Cohen, G. and Babaev, I. and Shurrush, K. and Avram, L. and Res...
    Journal of Medicinal Chemistry 65 10341-10356 (2022)
    High-throughput nanomole-scale synthesis allows for late-stage functionalization (LSF) of compounds in an efficient and economical manner. Here, we demonstrated that copper-catalyzed azide-alkyne cycloaddition could be used for the LSF of covalent kinase inhibitors at the nanoscale, enabling the synthesis of hundreds of compounds that did not require purification for biological assay screening, thus reducing experimental time drastically. We generated crude libraries of inhibitors for the kinase MKK7, derived from two different parental precursors, and analyzed them via the high-throughput In-Cell Western assay. Select inhibitors were resynthesized, validated via conventional biological and biochemical methods such as western blots and liquid chromatography-mass spectrometry (LC-MS) labeling, and successfully co-crystallized. Two of these compounds showed over 20-fold increased inhibitory activity compared to the parental compound. This study demonstrates that high-throughput LSF of covalent inhibitors at the nanomole-scale level can be an auspicious approach in improving the properties of lead chemical matter. © 2022 American Chemical Society.
    view abstractdoi: 10.1021/acs.jmedchem.1c02206
  • 2022 • 1035 Knowledge-Driven Data Ecosystems Toward Data Transparency
    Geisler, S. and Vidal, M.-E. and Cappiello, C. and Lóscio, B.F. and Gal, A. and Jarke, M. and Lenzerini, M. and Missier, P. and Otto, B. and Paja, E. and Pernici, B. and Rehof, J.
    Journal of Data and Information Quality 14 (2022)
    A data ecosystem (DE) offers a keystone-player or alliance-driven infrastructure that enables the interaction of different stakeholders and the resolution of interoperability issues among shared data. However, despite years of research in data governance and management, trustability is still affected by the absence of transparent and traceable data-driven pipelines. In this work, we focus on requirements and challenges that DEs face when ensuring data transparency. Requirements are derived from the data and organizational management, as well as from broader legal and ethical considerations. We propose a novel knowledge-driven DE architecture, providing the pillars for satisfying the analyzed requirements. We illustrate the potential of our proposal in a real-world scenario. Last, we discuss and rate the potential of the proposed architecture in the fulfillmentof these requirements. © 2021 Copyright held by the owner/author(s). Publication rights licensed to ACM.
    view abstractdoi: 10.1145/3467022
  • 2022 • 1034 Oxygen vacancy formation and electronic reconstruction in strained LaNiO3 and LaNiO3/LaAlO3 superlattices
    Geisler, B. and Follmann, S. and Pentcheva, R.
    Physical Review B 106 (2022)
    By using density functional theory calculations including a Coulomb repulsion term, we explore the formation of oxygen vacancies and their impact on the electronic and magnetic properties of strained bulk LaNiO3 and (LaNiO3)1/(LaAlO3)1(001) superlattices. For bulk LaNiO3, we find that epitaxial strain induces a substantial anisotropy in the oxygen vacancy formation energy. In particular, tensile strain promotes the selective reduction of apical oxygen, which may explain why the recently observed superconductivity in infinite-layer nickelates is limited to strained films. For (LaNiO3)1/(LaAlO3)1(001) superlattices, the simulations reveal that the NiO2 layer is most prone to vacancy formation, whereas the AlO2 layer exhibits generally the highest formation energies. The reduction is consistently endothermic, and a largely repulsive vacancy-vacancy interaction is identified as a function of the vacancy concentration. The released electrons are accommodated exclusively in the NiO2 layer, reducing the vacancy formation energy in the AlO2 layer by ∼70% with respect to bulk LaAlO3. By varying the vacancy concentration from 0 to 8.3% in the NiO2 layer at tensile strain, we observe an unexpected transition from a localized site-disproportionated (0.5%) to a delocalized (2.1%) charge accommodation, a reentrant site disproportionation leading to a metal-to-insulator transition despite a half-filled majority-spin Ni eg manifold (4.2%), and finally a magnetic phase transition (8.3%). While a band gap of up to 0.5 eV opens at 4.2% for compressive strain, it is smaller for tensile strain or the system is metallic, which is in sharp contrast to the defect-free superlattice. The strong interplay of electronic reconstructions and structural modifications induced by oxygen vacancies in this system highlights the key role of an explicit supercell treatment beyond rigid-band methods and exemplifies the complex response to defects in artificial transition metal oxides. © 2022 American Physical Society.
    view abstractdoi: 10.1103/PhysRevB.106.155139
  • 2022 • 1033 Atom Pair Frequencies as a Quantitative Structure-Activity Relationship for Catalytic 2-Propanol Oxidation over Nanocrystalline Cobalt-Iron-Spinel
    Geiss, J. and Falk, T. and Ognjanovic, S. and Anke, S. and Peng, B. and Muhler, M. and Winterer, M.
    Journal of Physical Chemistry C 126 10346-10358 (2022)
    The purpose of this study is to find a direct and quantitative correlation of the structure of Co3-xFexO4nanoparticles with catalytic performance in 2-propanol oxidation. Eight nanocrystalline samples with varying iron contents are synthesized, and quantitative information regarding their structure is obtained from nitrogen physisorption, X-ray diffraction (XRD), X-ray absorption near-edge structure (XANES), and extended X-ray absorption fine structure (EXAFS) analyzed by reverse Monte Carlo simulations. The catalytic performance is tested in 2-propanol oxidation in the gas phase. Overall, catalytic conversion data as a function of temperature are deconvoluted to obtain conversion and half-conversion temperatures as quantitative parameters for the different catalytic reaction channels. The crystal structure is described by a spinel structure with interstitial cation defects. These defects result in a reduced electronic state of the nanoparticles. The defect density depends on the cationic composition. We also observe a complex cationic distribution on tetrahedral and octahedral sites, which is strongly influenced by the overall cationic composition. In the catalytic tests, the samples exhibit a low-temperature pathway, which is deactivated in subsequent runs but can be recovered by an oxidative treatment of the catalyst. We find that the frequency of cation pairs CoO-CoOand CoO-CoTof the individual samples correlates directly to their catalytic activity and selectivity. © 2022 American Chemical Society. All rights reserved.
    view abstractdoi: 10.1021/acs.jpcc.2c00788
  • 2022 • 1032 Addressing the relation between transparency and supply chain finance schemes
    Gelsomino, L.M. and Sardesai, S. and Pirttilä, M. and Henke, M.
    International Journal of Production Research (2022)
    doi: 10.1080/00207543.2022.2115575
  • 2022 • 1031 Control of spoke movement in DCMS plasmas
    George, M. and Breilmann, W. and Held, J. and von Keudell, A.
    Plasma Sources Science and Technology 31 (2022)
    Spokes appear as zones of increased ionisation in magnetron sputtering discharges. They rotate in front of a 2″ target at a natural frequency between a few 10 kHz and several 100 kHz and move in E → × B → or anti E → × B → direction depending on plasma power. Spokes are known to cause strong gradients in plasma density and potential and can, thus, increase the ion transport from target to substrate. Here, we explore the possibility to control spokes by applying a given frequency f to a set of control probes around the plasma to lock the spoke movement. The efficiency of this locking is analyzed by diagnostic probes and energy resolved mass spectrometry, which measure the integrated ion fluxes leaving the magnetic trap region. It was found that the spoke movement could be locked to the external control signal at frequency f around the natural spoke frequencies f 0. The additional control signal affects the ion flux twofold: (i) a 15% increase in ion flux towards the substrate and a 15% reduction in radial direction irrespective of control frequency is observed, which is explained by a change in plasma confinement since electric fluctuations at the separatrix are induced; (ii) the locking at f causes an increase in ion current in normal as well as in radial direction for f &lt; f 0 and a reduction for f &gt; f 0. This is explained by either longer or shorter residence times of ions in the electric fields caused by the spoke, or by an enhancement of these fields caused by the control. Using this spoke controlling technique an overall increase of ion flux towards the substrate of up to 30% was realized. © 2022 The Author(s). Published by IOP Publishing Ltd.
    view abstractdoi: 10.1088/1361-6595/ac830e
  • 2022 • 1030 Computed tomography-based characterization of impact and fatigue after impact behavior of carbon fiber-reinforced polyurethane
    Gerdes, L. and Richle, S. and Mrzljak, S. and Hülsbusch, D. and Barandun, G. and Walther, F.
    Composite Structures 289 (2022)
    doi: 10.1016/j.compstruct.2022.115474
  • 2022 • 1029 Application-Oriented Digital Image Correlation for the High-Speed Deformation and Fracture Analysis of AISI 1045 and Ti6Al4V Materials
    Gerdes, L. and Berger, S. and Saelzer, J. and Franck, P. and Helwing, R. and Zabel, A. and Walther, F.
    Applied Mechanics 3 1190-1205 (2022)
    doi: 10.3390/applmech3040068
  • 2022 • 1028 Molecular dynamics study on the role of Ar ions in the sputter deposition of Al thin films
    Gergs, T. and Mussenbrock, T. and Trieschmann, J.
    Journal of Applied Physics 132 (2022)
    Compressive stresses in sputter deposited thin films are generally assumed to be caused by forward sputtered (peened) built-in particles and entrapped working gas atoms. While the former are assumed to be predominant, the effect of the latter on interaction dynamics and thin film properties is scarcely clarified (concurrent or causative). The overlay of the ion bombardment induced processes renders an isolation of their contribution impracticable. This issue is addressed by two molecular dynamics case studies considering the sputter deposition of Al thin films in Ar working gas. First, Ar atoms are fully retained. Second, they are artificially neglected, as implanted Ar atoms are assumed to outgas anyhow and not alter the ongoing dynamics significantly. Both case studies share common particle dose impinging Al(001) surfaces. Ion energies from 3 to 300 eV and Al / Ar + flux ratios from 0 to 1 are considered. The surface interactions are simulated by hybrid reactive molecular dynamics/force-biased Monte Carlo simulations and characterized in terms of mass density, Ar concentration, biaxial stress, shear stress, ring statistical connectivity profile, Ar gas porosity, Al vacancy density, and root-mean-squared roughness. Implanted Ar atoms are found to form subnanometer sized eventually outgassing clusters for ion energies exceeding 100 eV. They fundamentally govern a variety of surface processes (e.g., forward sputtering/peening) and surface properties (e.g., compressive stresses) in the considered operating regime. © 2022 Author(s).
    view abstractdoi: 10.1063/5.0098040
  • 2022 • 1027 Nanoporous SiOx plasma polymer films as carrier for liquid-infused surfaces
    Gergs, T. and Monti, C. and Gaiser, S. and Amberg, M. and Schütz, U. and Mussenbrock, T. and Trieschmann, J. and Heuberger, M. and Hegemann, D.
    Plasma Processes and Polymers 19 (2022)
    Liquid-infused surfaces are based upon the infusion of a liquid phase into a porous solid material to induce slippery and repellent character. In this context, porous SiOx plasma polymer films represent a relevant candidate for a robust nanoporous carrier layer. Intermittent low-pressure plasma etching of O2/hexamethyldisiloxane-derived coatings is investigated to enhance the intrinsic porosity inherent to residual hydrocarbons in the silica matrix. Simulations of the resulting Si–O ring network structure using reactive molecular dynamics indicate formation of interconnected voids with Si–OH functionalized pore walls allowing water penetration with almost Fickian diffusive behavior. The corresponding porosity of up to 18%, well agreeing with simulations, Fourier-transform infrared spectroscopy, and ellipsometry measurements, was found to be suitable for the liquid infusion of polyethylene glycol molecules into about 80 nm thick SiOx films providing ongoing lubricating properties, thus revealing their suitability as liquid-infused surfaces. © 2022 The Authors. Plasma Processes and Polymers published by Wiley-VCH GmbH.
    view abstractdoi: 10.1002/ppap.202200049
  • 2022 • 1026 Development and analysis of a mechatronic system for in-process monitoring and compensation of straightness deviation in BTA deep hole drilling
    Gerken, J.F. and Klages, N. and Biermann, D. and Denkena, B.
    Mechanical Systems and Signal Processing 170 (2022)
    In BTA deep hole drilling straightness deviation of the bore is a very important quality criteria. The avoidance of straightness deviation is not possible due to the many influencing variables. Currently used methods for compensation require significant additional time, as they either require the interruption of the drilling process, or require an additional boring process. By using a newly developed, manufactured and tested compensation unit, which is mounted between the drill head and the drill pipe, a targeted tilting of the drill head and thus a targeted influencing of the straightness deviation in the running process is possible with the use of a radially adjustable control pad and an innovative actuator concept. The developed measuring system offers the possibility to record the straightness deviation during the drilling process. On the basis of experimental test series, a control system was developed and applied to the BTA deep drilling process. After a drilling path of 1,000 mm, a maximum straightness deviation reduction of approx. 51 % can be realized. Compared to the process without control and compensation unit, the progressive increase of the straightness deviation was significantly reduced. © 2022 Elsevier Ltd
    view abstractdoi: 10.1016/j.ymssp.2022.108838
  • 2022 • 1025 Development and validation of a mesh-free flow model in ejector deep hole drilling [Entwicklung und Validierung eines gitterfreien Strömungsmodells beim Ejektortiefbohren: Strömungscharakteristika beim Ejektortiefbohren]
    Gerken, J.F. and Canini, D. and Biermann, D. and Eberhard, P.
    WT Werkstattstechnik 112 425-429 (2022)
    doi: 10.37544/1436-4980-2022-6-75
  • 2022 • 1024 Analysis of the cooling lubricant flow during ejector deep hole drilling by in-process volume flow and pressure measurements
    Gerken, J.F. and Daniel, M. and Biermann, D.
    Procedia CIRP 107 227-232 (2022)
    doi: 10.1016/j.procir.2022.04.038
  • 2022 • 1023 Synthesis and Characterization of Phosphorus-Containing Isocyclam Macrocycles and Their Nickel Complexes
    Gerschel, P. and Guseva, T. and Siegmund, D. and Apfel, U.-P.
    Journal of Organic Chemistry 87 16368-16377 (2022)
    doi: 10.1021/acs.joc.2c02049
  • 2022 • 1022 Is the bioactivity of induced membranes time dependent?
    Gessmann, J. and Rosteius, T. and Baecker, H. and Sivalingam, K. and Peter, E. and Schildhauer, T.A. and Köller, M.
    European Journal of Trauma and Emergency Surgery 48 3051-3061 (2022)
    Purpose: The induced membrane technique (IMT) is a two-stage surgical procedure for reconstruction of bone defects. Bone grafting (second stage of IMT) is recommend after 4–8 weeks assuming the highest bioactivity of IMs. However, larger studies concerning the biology and maturation of IMs and a potential time dependency of the bioactivity are missing. Therefore, aim of this study was the time-dependent structural and cellular characterization of cement spacer IMs concomitantly to an analysis of membrane bioactivity. Methods: IMs from 60 patients (35–82 years) were obtained at different maturation stages (1–16 weeks). IMs were studied by histology and co-culture with mesenchymal stem cells (MSC). IM lysates were analyzed by ELISA and protein microarray. Results: Increasing vascularization and fibrosis were found in membranes older than 4 and 7 weeks, respectively. MSC grew out from all membranes and all membranes enhanced proliferation of cultured MSC. Osteocalcin and osteopontin (in membrane lysates or induced in MSC by membrane tissue) were found over all time points without significant differences. In contrast to alkaline phosphatase activity, increasing levels of osteoprotegerin were found in membranes. Conclusion: The histological structure of IMs changes during growth and maturation, however, biologically active MSC and factors related to osteogenesis are found over all time points with minor changes. Thus, membranes older than 8 weeks exert regenerative capacities comparable to the younger ones. The postulated narrow time frame of 4–8 weeks until bone grafting can be questioned and surgeons may choose timing for the second operation more independently and based on other clinical factors. © 2021, The Author(s).
    view abstractdoi: 10.1007/s00068-021-01844-4
  • 2022 • 1021 Analysis, Prediction and Reduction of Emissions in an Industrial Hot Forming Process Chain for the Manufacture of Sheet Metal Components
    Ghattamaneni, M.C. and Wernicke, S. and Hainmann, T.S. and Sulaiman, H. and Tekkaya, A.E.
    Key Engineering Materials 926 KEM 2342-2354 (2022)
    doi: 10.4028/p-g7120f
  • 2022 • 1020 Comparison of the Catalytic Activity of Mono- and Multinuclear Ga Complexes in the ROCOP of Epoxides and Cyclic Anhydrides
    Ghosh, S. and Glöckler, E. and Wölper, C. and Linders, J. and Janoszka, N. and Gröschel, A.H. and Schulz, S.
    European Journal of Inorganic Chemistry 2022 (2022)
    Tetranuclear Schiff-base complexes L1–32Ga4(t-Bu)8 1–3 are highly active and selective (&gt;99 %) catalyst in the alternating ring-opening copolymerization (ROCOP) of epoxides and anhydrides, yielding polyesters with high molecular weights (Mn) and narrow dispersity (Đ). The thermal properties (Tg) of the resulting polyester range from 18 °C to 124 °C and increase with increasing steric bulk or rigidity along the polymer backbone. Comparative studies using structurally related complexes L4Ga(t-Bu)2 4, [L5GaR2]2 (R=t-Bu 5, R=Me 6) and L6Ga(t-Bu)2 7 proved that the Ga2O2 core of catalyst 1 is the catalytically active species. © 2021 The Authors. European Journal of Inorganic Chemistry published by Wiley-VCH GmbH
    view abstractdoi: 10.1002/ejic.202101017
  • 2022 • 1019 Cooperative Effect in Binuclear Zinc Catalysts in the ROP of Lactide
    Ghosh, S. and Schulte, Y. and Wölper, C. and Tjaberings, A. and Gröschel, A.H. and Haberhauer, G. and Schulz, S.
    Organometallics 41 2698-2708 (2022)
    Binuclear monomeric L1Zn2R2(R = Me 1 and Et 2; L2Zn2R2, R = Me 3 and Et 4) and dimeric ketodiiminate zinc alkyl complexes [L1(H)ZnR]2(R = Me 5 and Et 6; L1= (Me2NC2H4NC (Me)CH)2CO, L2= (Me2NC3H6NC(Me)CH)2CO) were synthesized and spectroscopically characterized (1H and 13C NMR and IR). Diffusion-ordered NMR spectroscopy and single-crystal X-ray diffraction analysis (1, 2, and 4-6) proved their monomeric (1-4) and dimeric (5 and 6) structures in solution and solid states. Their catalytic activity in the ring-opening polymerization of lactide was studied under various conditions and compared to mononuclear β-ketoimine zinc complexes 7-10. Initiation reactions of the Et-substituted complexes 2, 4, and 6 are faster than for the corresponding Me-substituted complexes 1, 3, and 5, and kinetic studies with catalyst 2 proved the first-order dependency on both the monomer and the catalyst concentration. Quantum chemical calculations revealed that the activation barriers for the addition of CH3-to L-LA via a mononuclear mechanism for the mono- (7) and binuclear (1) Me-substituted and the corresponding MeO-substituted complexes 1-OMe and 7-OMe, which are regarded as model compounds of the "active" catalyst, are similar. However, while the binuclear mechanism for complex 1 is slightly higher in energy than for the mononuclear mechanism, the binuclear pathway for the MeO-substituted complex 1-OMe is favored, clearly proving the beneficial cooperative effect between the two adjacent zinc atoms. © 2022 American Chemical Society. All rights reserved.
    view abstractdoi: 10.1021/acs.organomet.2c00333
  • 2022 • 1018 Short-range order and phase stability of CrCoNi explored with machine learning potentials
    Ghosh, S. and Sotskov, V. and Shapeev, A.V. and Neugebauer, J. and Körmann, F.
    Physical Review Materials 6 (2022)
    doi: 10.1103/PhysRevMaterials.6.113804
  • 2022 • 1017 Characterization of the electric transport properties of black phosphorous back-gated field-effect transistors
    Giubileo, F. and Pelella, A. and Grillo, A. and Faella, E. and Sleziona, S. and Kharsah, O. and Schleberger, M. and Bartolomeo, A.D.
    Journal of Physics: Conference Series 2353 (2022)
    doi: 10.1088/1742-6596/2353/1/012005
  • 2022 • 1016 Binuclear ketodiiminate magnesium complexes for the ROP of cyclic L-Lactide and ε-Caprolactone
    Glöckler, E. and Ghosh, S. and Wölper, C. and Coban, D. and Gröschel, A.H. and Schulz, S.
    Polyhedron 222 (2022)
    In contrast to well-established linear and branched polyesters, which find widespread biomedical and materials applications, cyclic polyesters have been less explored. We report on ketodiiminate magnesium complexes L12Mg3Cp+MgCp3- (1), L1(MgCp*)2 (2) and L2(MgCp)2 (3) (L1 = (Me2NC2H4NC(Me)CH)2CO, L2 = (Me2NC3H6NC(Me)CH)2CO), which were spectroscopically characterized (1H, 13C NMR, IR) as well as by elemental analysis and single crystal X-ray diffraction (sc-XRD). Complexes 1–3 were used in the ring-opening polymerization (ROP) of L-lactide (L-LA) and ε-caprolactone (ε-CL) under mild reaction conditions. Catalyst 2 showed excellent reactivity and selectivity for the synthesis of cyclic polylactide (cPLA; TOF = 17820 h−1) and cyclic polycaprolactone (cPCL; 712800 h−1). © 2022 Elsevier Ltd
    view abstractdoi: 10.1016/j.poly.2022.115918
  • 2022 • 1015 β-Diketiminate and β-Ketoiminate Metal Catalysts for Ring-Opening Polymerization of Cyclic Esters
    Glöckler, E. and Ghosh, S. and Schulz, S.
    Polymer Reviews (2022)
    This review highlights the ongoing developments on the ring-opening polymerization (ROP) of lactide (LA) and caprolactone (CL) using mononuclear and dinuclear β-diketiminate- and β-ketoiminate-substituted metal complexes. The resulting aliphatic polyesters are of great interest as sustainable replacements to petrochemicals-based polymers with potential applications in tissue engineering, bio-medical, and agricultural sciences. β-Diketiminate and β-ketoiminate metal complexes are very promising ROP catalysts since their steric and electronic properties, and hence their catalytic activity and selectivity can be easily modified. This review compares different classes of β-diketiminate and β-ketoiminate complexes with respect to the controlled synthesis of homopolymers and copolymers of aliphatic polyesters and elaborates on the polymerization kinetics and mechanistic studies. © 2022 Taylor & Francis Group, LLC.
    view abstractdoi: 10.1080/15583724.2022.2121837
  • 2022 • 1014 Amphiphilic Alginate-Based Layer-by-Layer Coatings Exhibiting Resistance against Nonspecific Protein Adsorption and Marine Biofouling
    Gnanasampanthan, T. and Karthäuser, J.F. and Spöllmann, S. and Wanka, R. and Becker, H.-W. and Rosenhahn, A.
    ACS Applied Materials and Interfaces 14 16062-16073 (2022)
    Amphiphilic coatings are promising materials for fouling-release applications, especially when their building blocks are inexpensive, biodegradable, and readily accessible polysaccharides. Here, amphiphilic polysaccharides were fabricated by coupling hydrophobic pentafluoropropylamine (PFPA) to carboxylate groups of hydrophilic alginic acid, a natural biopolymer with high water-binding capacity. Layer-by-layer (LbL) coatings comprising unmodified or amphiphilic alginic acid (AA*) and polyethylenimine (PEI) were assembled to explore how different PFPA contents affect their physicochemical properties, resistance against nonspecific adsorption (NSA) of proteins, and antifouling activity against marine bacteria (Cobetia marina) and diatoms (Navicula perminuta). The amphiphilic multilayers, characterized through spectroscopic ellipsometry, water contact angle goniometry, elemental analysis, AFM, XPS, and SPR spectroscopy, showed similar or even higher swelling in water and exhibited higher resistance toward NSA of proteins and microfouling marine organisms than multilayers without fluoroalkyl groups. © 2022 American Chemical Society. All rights reserved.
    view abstractdoi: 10.1021/acsami.2c01809
  • 2022 • 1013 Competing instabilities of the extended Hubbard model on the triangular lattice: Truncated-unity functional renormalization group and application to moiré materials
    Gneist, N. and Classen, L. and Scherer, M.M.
    Physical Review B 106 (2022)
    doi: 10.1103/PhysRevB.106.125141
  • 2022 • 1012 Functional renormalization of spinless triangular-lattice fermions: N-patch vs. truncated-unity scheme
    Gneist, N. and Kiese, D. and Henkel, R. and Thomale, R. and Classen, L. and Scherer, M.M.
    European Physical Journal B 95 (2022)
    doi: 10.1140/epjb/s10051-022-00395-w
  • 2022 • 1011 Trion magnetic polarons in (Cd,Mn)Te/(Cd,Mn,Mg)Te quantum wells
    Godejohann, F. and Akhmadullin, R.R. and Kavokin, K.V. and Yakovlev, D.R. and Akimov, I.A. and Namozov, B.R. and Kusrayev, Y.G. and Karczewski, G. and Wojtowicz, T. and Bayer, M.
    Physical Review B 106 (2022)
    doi: 10.1103/PhysRevB.106.195305
  • 2022 • 1010 Photocatalytic nanocomposite membranes for environmental remediation
    Golmohammadi, M. and Sabbagh Alvani, A.A. and Sameie, H. and Mei, B. and Salimi, R. and Poelman, D. and Rosei, F.
    Nanotechnology 33 (2022)
    We report the design and one-pot synthesis of Ag-doped BiVO4 embedded in reduced graphene oxide (BiVO4:Ag/rGO) nanocomposites via a hydrothermal processing route. The binary heterojunction photocatalysts exhibited high efficiency for visible light degradation of model dyes and were correspondingly used for the preparation of photocatalytic membranes using polyvinylidene fluoride (PVDF) or polyethylene glycol (PEG)-modified polyimide (PI), respectively. The surface and cross-section images combined with elemental mapping illustrated the effective distribution of the nanocomposites within the polymeric membranes. Photocatalytic degradation efficiencies of 61% and 70% were achieved after 5 h of visible light irradiation using BiVO4:Ag/rGO@PVDF and BiVO4:Ag/rGO@PI (PEG-modified) systems, respectively. The beneficial photocatalytic performance of the BiVO4:Ag/rGO@PI (PEG-modified) membrane is explained by the higher hydrophilicity due to the PEG modification of the PI membrane. This work may provide a rational and effective strategy to fabricate highly efficient photocatalytic nanocomposite membranes with well-contacted interfaces for environmental purification. © 2022 IOP Publishing Ltd.
    view abstractdoi: 10.1088/1361-6528/ac8682
  • 2022 • 1009 A Comparative Study of the Band-Edge Exciton Fine Structure in Zinc Blende and Wurtzite CdSe Nanocrystals
    Golovatenko, A.A. and Kalitukha, I.V. and Dimitriev, G.S. and Sapega, V.F. and Rakhlin, M.V. and Galimov, A.I. and Shubina, T.V. and Shornikova, E.V. and Qiang, G. and Yakovlev, D.R. and Bayer, M. and Biermann, A. and Hoffmann, A....
    Nanomaterials 12 (2022)
    doi: 10.3390/nano12234269
  • 2022 • 1008 On the interplay between microstructure, residual stress and fracture toughness of (Hf-Nb-Ta-Zr)C multi-metal carbide hard coatings
    Gopalan, H. and Marshal, A. and Hans, M. and Primetzhofer, D. and Cautaerts, N. and Breitbach, B. and Völker, B. and Kirchlechner, C. and Schneider, J.M. and Dehm, G.
    Materials and Design 224 (2022)
    doi: 10.1016/j.matdes.2022.111323
  • 2022 • 1007 THE INTEGRATED COPULA SPECTRUM
    Goto, Y. and Kley, T. and van Hecke, R. and Volgushev, S. and Dette, H. and Hallin, M.
    Annals of Statistics 50 3563-3591 (2022)
    doi: 10.1214/22-AOS2240
  • 2022 • 1006 Influence of process temperature and residence time on the manufacturing of amorphous solid dispersions in hot melt extrusion
    Gottschalk, T. and Grönniger, B. and Ludwig, E. and Wolbert, F. and Feuerbach, T. and Sadowski, G. and Thommes, M.
    Pharmaceutical Development and Technology 27 313-318 (2022)
    The manufacturing of amorphous solid dispersions via hot melt extrusion is a topic of high interest in pharmaceutical development. By this technique, the drug is dissolved in the molten polymer above solubility temperature within the process time. In this study, an experimental framework is proposed determining the minimum required process temperature and the residence time using particularly low quantities of material. Drug/polymer mixtures in different ratios were processed in a micro-scale extruder while the process temperature and residence time were varied systematically. The phase situation was assessed by the turbidity of the final extrudate. Four different drug/polymer mixtures were investigated in three drug/polymer ratios. The minimum required process temperature was close to solubility temperature for each specific formulation. Moreover, an influence of residence time on the phase situation was found. About three minutes were required in order to dissolve the drug in the polymer at these process conditions. © 2022 Informa UK Limited, trading as Taylor & Francis Group.
    view abstractdoi: 10.1080/10837450.2022.2051549
  • 2022 • 1005 Predicting Throughput and Melt Temperature in Pharmaceutical Hot Melt Extrusion
    Gottschalk, T. and Özbay, C. and Feuerbach, T. and Thommes, M.
    Pharmaceutics 14 (2022)
    Even though hot melt extrusion (HME) is a commonly applied process in the pharmaceutical area, determination of the optimal process parameters is demanding. The goal of this study was to find a rational approach for predetermining suitable extrusion parameters, with a focus on material temperature and throughput. A two-step optimization procedure, called scale-independent optimization strategy (SIOS), was applied and developed further, including the use of an autogenic extrusion mode. Three different polymers (Plasdone S-630, Soluplus, and Eudragit EPO) were considered, and different optimal process parameters were assessed. The maximum barrel load was dependent on the polymers’ bulk density and the extruder size. The melt temperature was influenced by the screw speed and the rheological behavior of the polymer. The melt viscosity depended mainly on the screw speed and was self-adjusted in the autogenic extrusion. A new approach, called SIOS 2.0, was suggested for calculating the extrusion process parameters (screw speed, melt temperature and throughput) based on the material data and a few extrusion experiments. © 2022 by the authors.
    view abstractdoi: 10.3390/pharmaceutics14091757
  • 2022 • 1004 Addressing the Osimertinib Resistance Mutation EGFR-L858R/C797S with Reversible Aminopyrimidines
    Grabe, T. and Jeyakumar, K. and Niggenaber, J. and Schulz, T. and Koska, S. and Kleinbölting, S. and Beck, M.E. and Müller, M.P. and Rauh, D.
    ACS Medicinal Chemistry Letters (2022)
    doi: 10.1021/acsmedchemlett.2c00514
  • 2022 • 1003 Fill Factor Losses and Deviations from the Superposition Principle in Lead Halide Perovskite Solar Cells
    Grabowski, D. and Liu, Z. and Schöpe, G. and Rau, U. and Kirchartz, T.
    Solar RRL 6 (2022)
    The enhancement of the fill factor in the current generation of perovskite solar cells is the key for further efficiency improvement. Thus, methods to quantify the fill factor losses are urgently needed. Two methods are presented to quantify losses due to the finite resistance of the semiconducting layers of the solar cell as well as its contacts. The first method is based on the comparison between the voltage in the dark and under illumination analyzed at equal recombination current density and results in a voltage-dependent series resistance. Furthermore, the method reveals the existence of a strong photoshunt under illumination. The second method is based on measuring the photoluminescence of perovskite solar cells as a function of applied voltage. Thereby, the recombination current is determined as a function of voltage from short circuit to open circuit, and the presence of the photoshunt is explained with a high resistance of the electron and/or hole transport layers combined with field screening in the absorber. © 2022 The Authors. Solar RRL published by Wiley-VCH GmbH.
    view abstractdoi: 10.1002/solr.202200507
  • 2022 • 1002 Spatial Distribution of Intracellular Ion Concentrations in Aggregate-Forming HeLa Cells Analyzed by μ-XRF Imaging
    Gräfenstein, A. and Rumancev, C. and Pollak, R. and Hämisch, B. and Galbierz, V. and Schroeder, W.H. and Garrevoet, J. and Falkenberg, G. and Vöpel, T. and Huber, K. and Ebbinghaus, S. and Rosenhahn, A.
    ChemistryOpen 11 (2022)
    Protein aggregation is a hallmark of several severe neurodegenerative disorders such as Huntington's, Parkinson's, or Alzheimer's disease. Metal ions play a profound role in protein aggregation and altered metal-ion homeostasis is associated with disease progression. Here we utilize μ-X-ray fluorescence imaging in combination with rapid freezing to resolve the elemental distribution of phosphorus, sulfur, potassium, and zinc in huntingtin exon-1-mYFP expressing HeLa cells. Using quantitative XRF analysis, we find a threefold increase in zinc and a 10-fold enrichment of potassium that can be attributed to cellular stress response. While the averaged intracellular ion areal masses are significantly different in aggregate-containing cells, a local intracellular analysis shows no different ion content at the location of intracellular inclusion bodies. The results are compared to corresponding experiments on HeLa cells forming pseudoisocyanine chloride aggregates. As those show similar results, changes in ion concentrations are not exclusively linked to huntingtin exon-1 amyloid formation. © 2022 The Authors. Published by Wiley-VCH GmbH.
    view abstractdoi: 10.1002/open.202200024
  • 2022 • 1001 Memory effects in black phosphorus field effect transistors
    Grillo, A. and Pelella, A. and Faella, E. and Giubileo, F. and Sleziona, S. and Kharsah, O. and Schleberger, M. and Di Bartolomeo, A.
    2D Materials 9 (2022)
    We report the fabrication and the electrical characterization of back-gated field effect transistors with a black phosphorus (BP) channel. We show that the hysteresis of the transfer characteristic, due to intrinsic defects, can be exploited to realize non-volatile memories. We demonstrate that gate voltage pulses allow to trap and store charge inside the defect states, which enable memory devices with endurance over 200 cycles and retention longer than 30 min. We show that the use of a protective poly(methyl methacrylate) layer, positioned on top of the BP channel, does not affect the electrical properties of the device but avoids the degradation caused by the exposure to air. © 2021 IOP Publishing Ltd.
    view abstractdoi: 10.1088/2053-1583/ac3f45
  • 2022 • 1000 Mechanism and Kinetics of the Thermal Decomposition of Fe(C5H5)2 in Inert and Reductive Atmosphere: A Synchrotron-Assisted Investigation in A Microreactor
    Grimm, S. and Hemberger, P. and Kasper, T. and Atakan, B.
    Advanced Materials Interfaces 9 (2022)
    doi: 10.1002/admi.202200192
  • 2022 • 999 Insights into the decomposition of zirconium acetylacetonate using synchrotron radiation: Routes to the formation of volatile Zr-intermediates
    Grimm, S. and Baik, S.-J. and Hemberger, P. and Kasper, T. and Kempf, A.M. and Atakan, B.
    Journal of Materials Research 37 1558-1575 (2022)
    doi: 10.1557/s43578-022-00566-6
  • 2022 • 998 Multiple Rabi rotations of trions in InGaAs quantum dots observed by photon echo spectroscopy with spatially shaped laser pulses
    Grisard, S. and Rose, H. and Trifonov, A.V. and Reichhardt, R. and Reiter, D.E. and Reichelt, M. and Schneider, C. and Kamp, M. and Höfling, S. and Bayer, M. and Meier, T. and Akimov, I.A.
    Physical Review B 106 (2022)
    doi: 10.1103/PhysRevB.106.205408
  • 2022 • 997 Analysing the Porosity Distribution in Stone Surfaces by Means of Unilateral NMR after Long-Term Outdoor Weathering
    Groh, M. and Orlowsky, J. and Holthausen, R.S.
    Materials 15 (2022)
    Porosity changes in the near-surface area of sandstones due to long-term weathering can produce deterioration. Therefore, porosity analyses on weathered sandstones are significant for detecting possible influences on the pore structure. Classical methods for determining the porosity and pore size distribution in sandstones can only investigate the entire sample volume. In contrast, in this publication, the porosity was analysed in 0.2 mm steps over a depth of 5 mm by means of single-sided NMR measurements on water-saturated sandstones under vacuum. Evaluations of Obernkirchener and Schleeriether Sandstones that were weathered outdoors in Germany for over 30 years are presented. The results showed that the water content in Vol.-% strongly correlated with the normalised NMR signal. The unweathered sandstones showed a uniform distribution of micro and capillary pores throughout the stone depth. As a result of 30 years of outdoor weathering, changes in the pore structure occurred at the sandstone surface due to weathering down to depths of about 0.6 mm. The porosity of the Schleeriether Sandstone samples, mainly the microporosity, clearly increased in this region. Due to the dominance of capillary pores in the Obernkirchener Sandstone, the changes were not as pronounced, but a shift towards smaller pores in the surface area was observable. © 2022 by the authors. Licensee MDPI, Basel, Switzerland.
    view abstractdoi: 10.3390/ma15134604
  • 2022 • 996 Probability of Unrecognized LiDAR Interference for TCSPC LiDAR
    Grollius, S. and Buchner, A. and Ligges, M. and Grabmaier, A.
    IEEE Sensors Journal 22 12976-12986 (2022)
    doi: 10.1109/JSEN.2022.3178179
  • 2022 • 995 Optimized Interference Suppression for TCSPC LiDAR
    Grollius, S. and Grosse, S. and Ligges, M. and Grabmaier, A.
    IEEE Sensors Journal 1-1 (2022)
    doi: 10.1109/JSEN.2022.3216810
  • 2022 • 994 Aliphatic Aldehydes in the Earth’s Crust—Remains of Prebiotic Chemistry?
    Großmann, Y. and Schreiber, U. and Mayer, C. and Schmitz, O.J.
    Life 12 (2022)
    The origin of life is a mystery that has not yet been solved in the natural sciences. Some promising interpretative approaches are related to hydrothermal activities. Hydrothermal environments contain all necessary elements for the development of precursor molecules. There are surfaces with possible catalytic activity, and wide ranges of pressure and temperature conditions. The chemical composition of hydrothermal fluids together with periodically fluctuating physical conditions should open up multiple pathways towards prebiotic molecules. In 2017, we detected potentially prebiotic organic substances, including a homologous series of aldehydes in Archean quartz crystals from Western Australia, more than 3 billion years old. In order to approach the question of whether the transformation of inorganic into organic substances is an ongoing process, we investigated a drill core from the geologically young Wehr caldera in Germany at a depth of 1000 m. Here, we show the existence of a similar homologous series of aldehydes (C8 to C16) in the fluid inclusions of the drill core calcites, a finding that supports the thesis that hydrothermal environments could possibly be the material source for the origin of life. © 2022 by the authors. Licensee MDPI, Basel, Switzerland.
    view abstractdoi: 10.3390/life12070925
  • 2022 • 993 Interplay of domain structure and phase transitions: Theory, experiment and functionality
    Grünebohm, A. and Marathe, M. and Khachaturyan, R. and Schiedung, R. and Lupascu, D.C. and Shvartsman, V.V.
    Journal of Physics Condensed Matter 34 (2022)
    Domain walls and phase boundaries are fundamental ingredients of ferroelectrics and strongly influence their functional properties. Although both interfaces have been studied for decades, often only a phenomenological macroscopic understanding has been established. The recent developments in experiments and theory allow to address the relevant time and length scales and revisit nucleation, phase propagation and the coupling of domains and phase transitions. This review attempts to specify regularities of domain formation and evolution at ferroelectric transitions and give an overview on unusual polar topological structures that appear as transient states and at the nanoscale. We survey the benefits, validity, and limitations of experimental tools as well as simulation methods to study phase and domain interfaces. We focus on the recent success of these tools in joint scale-bridging studies to solve long lasting puzzles in the field and give an outlook on recent trends in superlattices. © 2021 IOP Publishing Ltd.
    view abstractdoi: 10.1088/1361-648X/ac3607
  • 2022 • 992 A benchmark dataset for Hydrogen Combustion
    Guan, X. and Das, A. and Stein, C.J. and Heidar-Zadeh, F. and Bertels, L. and Liu, M. and Haghighatlari, M. and Li, J. and Zhang, O. and Hao, H. and Leven, I. and Head-Gordon, M. and Head-Gordon, T.
    Scientific Data 9 (2022)
    The generation of reference data for deep learning models is challenging for reactive systems, and more so for combustion reactions due to the extreme conditions that create radical species and alternative spin states during the combustion process. Here, we extend intrinsic reaction coordinate (IRC) calculations with ab initio MD simulations and normal mode displacement calculations to more extensively cover the potential energy surface for 19 reaction channels for hydrogen combustion. A total of ∼290,000 potential energies and ∼1,270,000 nuclear force vectors are evaluated with a high quality range-separated hybrid density functional, ωB97X-V, to construct the reference data set, including transition state ensembles, for the deep learning models to study hydrogen combustion reaction. © 2022, The Author(s).
    view abstractdoi: 10.1038/s41597-022-01330-5
  • 2022 • 991 Foundations of physical vapor deposition with plasma assistance
    Gudmundsson, J.T. and Anders, A. and von Keudell, A.
    Plasma Sources Science and Technology 31 (2022)
    doi: 10.1088/1361-6595/ac7f53
  • 2022 • 990 First evidence of crucible steel production in Medieval Anatolia, Kubadabad: A trace for possible technology exchange between Anatolia and Southern Asia
    Güder, Ü. and Çeken, M. and Yavaş, A. and Yalçın, Ü. and Raabe, D.
    Journal of Archaeological Science 137 (2022)
    In this article, we present the first archaeological evidence for crucible steel production in Anatolia uncovered in recent excavations at Kubadabad, which was built as a palace by the Anatolian Seljuks in the early 13th century AD. Along with plenty of crucible sherds recovered at the site, blades made of crucible steel, production waste-iron chunks and manganese oxide pellets also revealed remarkable information about the process of production. Based on the results of the archaeometry analysis of crucibles of a unique shape with a pointed base, it was discovered that the fabric of the crucible was tempered with finely crushed charcoal, straw and quartz-containing sand. In addition, metallography and SEM analysis conducted on the metal finds demonstrated that high-quality tools were produced from manganese alloy crucible steel ingots at the site. This study evaluates most of the finds found at Kubadabad from the end of the 13th century AD, when some of the buildings were converted into workshops for decorated ceramic tiles and metal production under Ilkhanid patronage or Turkish beyliks. Using analytical results and archaeological findings, we discuss the historical connections of crucible steel production in Kubadabad, which differs from the Central Asian and Persian traditions, but shares similarities with the Southern Asian tradition. © 2021 Elsevier Ltd
    view abstractdoi: 10.1016/j.jas.2021.105529
  • 2022 • 989 Blockchain Technology in Supply Chain Management – A Discussion of Current and Future Research Topics
    Gürpinar, T. and Große, N. and Schwarzer, M. and Burov, E. and Stammes, R. and Ioannidis, P.A. and Krämer, L. and Ahlbäumer, R. and Henke, M.
    Lecture Notes of the Institute for Computer Sciences, Social-Informatics and Telecommunications Engineering, LNICST 442 LNICST 482-503 (2022)
    doi: 10.1007/978-3-031-06371-8_32
  • 2022 • 988 Revisiting the Growth of Large (Mg,Zr):SrGa12O19Single Crystals: Core Formation and Its Impact on Structural Homogeneity Revealed by Correlative X-ray Imaging
    Guguschev, C. and Richter, C. and Brützam, M. and Dadzis, K. and Hirschle, C. and Gesing, T.M. and Schulze, M. and Kwasniewski, A. and Schreuer, J. and Schlom, D.G.
    Crystal Growth and Design 22 2557-2568 (2022)
    We demonstrate the growth of large (Mg,Zr):SrGa12O19(SGMZ) single crystals and use a combination of X-ray imaging techniques to analyze their structural and chemical homogeneity. Single-crystal cylinders with lengths and diameters up to about 2.5 cm are achieved. Our characterization of polished sections reveals a localized (0001) facet that is typically formed at the center of the growth interface. Such facets are seen as the key factor limiting the growth of large-area crystals with excellent structural quality due to local deviations in the segregation behavior of the dopants. We developed a lab-based X-ray diffraction imaging technique with high sensitivity that exposes subtle variations in lattice parameters and lattice tilts, which are attributed to changes in the chemical composition and the resulting elastic deformation. The relationship between unit-cell dimensions and composition is verified by micro X-ray fluorescence mapping. In this way, we find a Ga-rich center region with a reduced unit-cell volume that is surrounded by a ring of increased tilt and elastic strain. Furthermore, we observe a 6-fold in-plane anisotropy of dopant incorporation and tree-ring-shaped structures caused by macrosteps. With rocking curve widths below 23 arcsec in ∼90% of the crystal, SGMZ crystals are largely homogeneous and hence suitable for the preparation of high-quality substrates. For most applications, the substantially enhanced crystal size enabled by very high Mg and Zr codoping levels outweighs the issues related to concentration variations arising from their addition. © 2022 American Chemical Society. All rights reserved.
    view abstractdoi: 10.1021/acs.cgd.2c00030
  • 2022 • 987 Role-Specialized Division of Labor in CO2 Reduction with Doubly-Functionalized Iron Porphyrin Atropisomers
    Guo, K. and Li, X. and Lei, H. and Guo, H. and Jin, X. and Zhang, X.-P. and Zhang, W. and Apfel, U.-P. and Cao, R.
    Angewandte Chemie - International Edition 61 (2022)
    doi: 10.1002/anie.202209602
  • 2022 • 986 Megaporous monolithic adsorbents for bioproduct recovery as prepared on the basis of nonwoven fabrics
    Guo, Y. and Ali, W. and Schneider, A. and Salma, A. and Mayer-Gall, T. and Gutmann, J.S. and Fernandez Lahore, H.M.
    Electrophoresis 43 1387-1398 (2022)
    doi: 10.1002/elps.202100220
  • 2022 • 985 Defective Metal-Organic Frameworks with Tunable Porosity and Metal Active Sites for Significantly Improved Performance in Styrene Oxidation
    Guo, P. and Cheng, H. and Zeng, X. and Tao, L. and Peng, B. and Zhang, S. and Fischer, R.A. and Muhler, M.
    ChemPlusChem 87 (2022)
    doi: 10.1002/cplu.202200303
  • 2022 • 984 Requirements for DataOps to foster Dynamic Capabilities in Organizations - A mixed methods approach
    Gur, I. and Moller, F. and Hupperz, M. and Uzun, D. and Otto, B.
    Proceedings - 2022 IEEE 24th Conference on Business Informatics, CBI 2022 1 166-175 (2022)
    doi: 10.1109/CBI54897.2022.00025
  • 2022 • 983 Reviews and syntheses: A framework to observe, understand and project ecosystem response to environmental change in the East Antarctic Southern Ocean
    Gutt, J. and Arndt, S. and Barnes, D.K.A. and Bornemann, H. and Brey, T. and Eisen, O. and Flores, H. and Griffiths, H. and Haas, C. and Hain, S. and Hattermann, T. and Held, C. and Hoppema, M. and Isla, E. and Janout, M. and Le B...
    Biogeosciences 19 5313-5342 (2022)
    doi: 10.5194/bg-19-5313-2022
  • 2022 • 982 Iron-cementite nanoparticles in carbon matrix: Synthesis, structure and magnetic properties
    Gyulasaryan, H. and Avakyan, L. and Emelyanov, A. and Sisakyan, N. and Kubrin, S. and Srabionyan, V. and Ovcharov, A. and Dannangoda, C. and Bugaev, L. and Sharoyan, E. and Angelakeris, M. and Farle, M. and Spasova, M. and Martiro...
    Journal of Magnetism and Magnetic Materials 559 (2022)
    doi: 10.1016/j.jmmm.2022.169503
  • 2022 • 981 X-Band Parallel-Mode and Multifrequency Electron Paramagnetic Resonance Spectroscopy of S = 1/2 Bismuth Centers
    Haak, J. and Krüger, J. and Abrosimov, N.V. and Helling, C. and Schulz, S. and Cutsail Iii, G.E.
    Inorganic Chemistry 61 11173-11181 (2022)
    The recent successes in the isolation and characterization of several bismuth radicals inspire the development of new spectroscopic approaches for the in-depth analysis of their electronic structure. Electron paramagnetic resonance (EPR) spectroscopy is a powerful tool for the characterization of main group radicals. However, the large electron-nuclear hyperfine interactions of Bi (209Bi, I = 9/2) have presented difficult challenges to fully interpret the spectral properties for some of these radicals. Parallel-mode EPR (B1B0) is almost exclusively employed for the study of S &gt; 1/2 systems but becomes feasible for S = 1/2 systems with large hyperfine couplings, offering a distinct EPR spectroscopic approach. Herein, we demonstrate the application of conventional X-band parallel-mode EPR for S = 1/2, I = 9/2 spin systems: Bi-doped crystalline silicon (Si:Bi) and the molecular Bi radicals [L(X)Ga]2Bi &gt;(X = Cl or I) and [L(Cl)GaBi(MecAAC)]+(L = HC[MeCN(2,6-iPr2C6H3)]2). In combination with multifrequency perpendicular-mode EPR (X-, Q-, and W-band frequencies), we were able to fully refine both the anisotropic g-and A-Tensors of these molecular radicals. The parallel-mode EPR experiments demonstrated and discussed here have the potential to enable the characterization of other S = 1/2 systems with large hyperfine couplings, which is often challenging by conventional perpendicular-mode EPR techniques. Considerations pertaining to the choice of microwave frequency are discussed for relevant spin-systems. © 2022 American Chemical Society. All rights reserved.
    view abstractdoi: 10.1021/acs.inorgchem.2c01141
  • 2022 • 980 Turbomachine Operation with Magnetic Bearings in Supercritical Carbon Dioxide Environment
    Hacks, A.J. and Brillert, D.
    International Journal of Turbomachinery, Propulsion and Power 7 (2022)
    doi: 10.3390/ijtpp7020018
  • 2022 • 979 Experimental Data of Supercritical Carbon Dioxide (sCO2) Compressor at Various Fluid States
    Hacks, A.J. and El Hussein, I.A. and Ren, H. and Schuster, S. and Brillert, D.
    Journal of Engineering for Gas Turbines and Power 144 (2022)
    doi: 10.1115/1.4052954
  • 2022 • 978 Photonic-assisted 2-D terahertz beam steering enabled by a LWA array monolithically integrated with a BFN
    Haddad, T. and Biurrun-Quel, C. and Lu, P. and Tebart, J. and Sievert, B. and Makhlouf, S. and Grzeslo, M. and Teniente, J. and Del-Río, C. and Stöhr, A.
    Optics Express 30 38596-38612 (2022)
    A novel photonic-assisted 2-D Terahertz beam steering chip using only two tuning elements is presented. The chip is based on an array of three leaky wave antennas (LWAs) with a monolithically integrated beamforming network (BFN) on a 50 µm-thick indium phosphide substrate. The THz beam angle in elevation (E-plane) is controlled via optical frequency tuning using a tunable dual-wavelength laser. An optical delay line is used for azimuth (H-plane) beam control. The simulated beam scanning range is 92° in elevation for a frequency sweep from 0.23 THz to 0.33 THz and 69.18° in azimuth for a time delay of 3.6 ps. For the frequency range from 0.26 THz to 0.32 THz, it is confirmed experimentally that the THz beam scans from −12° to +33°, which is in good agreement with the numerical simulations. The beam direction in azimuth scans with a total angle of 39° when applying a delay difference of 1.68 ps. A good agreement is found between theoretically predicted and experimentally determined THz beam angles with a maximum angle deviation below 5°. The experimental scanning angles are limited due to the mechanical constraints of the on-wafer probes, the on-chip integrated transition and the bandwidth of the THz receiver LNA. The mechanical limitation will be overcome when using a packaged chip. © 2022 Optica Publishing Group under the terms of the Optica Open Access Publishing Agreement.
    view abstractdoi: 10.1364/OE.468200
  • 2022 • 977 Simplified approach to the magnetic blue shift of Mott gaps
    Hafez-Torbati, M. and Anders, F.B. and Uhrig, G.S.
    Physical Review B 106 (2022)
    doi: 10.1103/PhysRevB.106.205117
  • 2022 • 976 More than recycling – The potential of the circular economy shown by a case study of the metal working industry
    Hagedorn, W. and Jäger, S. and Wieczorek, L. and Kronenberg, P. and Greiff, K. and Weber, S. and Roettger, A.
    Journal of Cleaner Production 377 (2022)
    The steel industry is responsible for a quarter of all industrial greenhouse gas emissions. So far, the environmental savings are mainly due to steel recycling. Besides recycling, the circular economy offers strategies to increase material efficiency and thus decrease the primary raw material demand. However, the potentials remain unexploited because circular economy concepts with a higher degree of circularity are not considered. The presented case study of an industrial machining knife illustrates how the production process can be improved by implementing various circular strategies. The environmental performance is analyzed by calculating and comparing the carbon footprint, the cumulative energy demand and the material footprint, and the material efficiency indicator. The results show that the implementation of the three overarching strategies of the circular economy - narrowing, closing, and slowing – contributes to a significant increase in material efficiency. The implementation also has a positive effect on the overall environmental performance. The circular production processes require less energy and resources and cause fewer emissions. Auxiliary processes such as additional transport routes are relevant, as they can reduce or even overcompensate for savings. These processes must be adequately considered and designed. © 2022 Elsevier Ltd
    view abstractdoi: 10.1016/j.jclepro.2022.134439
  • 2022 • 975 Microstructural and Tribo-mechanical Properties of Arc-Sprayed CoCr-Based Coatings
    Hagen, L. and Paulus, M. and Tillmann, W.
    Journal of Thermal Spray Technology 31 2229-2242 (2022)
    Due to their superior wear and oxidation resistance, Stellite™ coatings are widely used in industrial applications, where the coatings are exposed to high temperature. Common processes for applying Stellite™ coatings include the high-velocity oxy-fuel spraying, laser cladding, and plasma transferred arc welding. Although Stellite™ welding consumables or similar welding consumables in the form of cored wires (CoCr base without industrial property rights) are commercially available, there are hardly any studies on arc-sprayed Stellite™ coatings available in the literature. In this study, the microstructural characteristics of arc-sprayed deposits were investigated, which were produced using a CoCr-based cored wire with addition of 4.5 wt.% tungsten. The produced deposits were examined in its as-sprayed state as well as after exposed to elevated temperatures. The microstructure was scrutinized by means of electron microscopy, energy-dispersive x-ray spectroscopy, as well as x-ray diffraction analyses using synchrotron radiation. Tribo-mechanical tests were conducted in order to assess the performance of the arc-sprayed coating. The findings were discussed and compared to those obtained from conventional CoCr-based coatings. It was found that the arc-sprayed CoCr-based coating is predominantly composed of Co-rich, Cr-rich lamellae or lamellae comprising a Co(Cr)-rich solid solution interspersed with various oxides between the individual lamellae. Solid solution hardening serves as dominant strengthening mechanism, while precipitation hardening effects are hardly evident. With regard to the oxidation behaviour, the as-sprayed coating mainly contains CoCr2O4 as well as traces of Co3O4. For heating above 550 °C, coating surface additionally consists of Fe2O3 and Co3O4. In dry sliding experiments, the arc-sprayed CoCr-based coating shows a decreased wear resistance compared to CoCr-based coatings processed by HVOF and PTA, whereas the coefficient of friction (COF) sliding against alumina was similar to the COF observed for the HVOF-sprayed CoCr-based coating, but lower than the COF obtained for the CoCr-based hardfacing alloy deposited by PTA. © 2022, The Author(s).
    view abstractdoi: 10.1007/s11666-022-01440-x
  • 2022 • 974 Novel Development of an NbC-Containing Powder-Metallurgical Martensitic Steel with Outstanding Tribocorrosion Resistance
    Hahn, I. and Siebert, S. and Fluch, R. and Theisen, W. and Weber, S.
    Steel Research International (2022)
    The development of NbC-containing martensitic stainless steels has made it possible to unite the properties of high corrosion resistance and wear resistance. If NbC is used as a hard phase instead of chromium carbide, the abrasive wear resistance of the steels is increased due to the greater hardness of NbC. The solubility of chromium in NbC is low. For this reason, chromium is fully available to form a passive surface layer to increase the corrosion resistance. In the steel melt, niobium leads to the formation of primary NbC, which grows very rapidly. Atomization of PM steels leads to the formation of coarse primary hard phases that clog the nozzle. Therefore, until now, steels with NbC as a hard phase are produced using the PM route with so-called diffusion alloying; however, this production route is very complex and expensive. Herein, a novel Nb-rich MC-containing wear- and corrosion-resistant steel that is produced using the usual PM route is presented. This steel consists of a martensitic matrix with evenly dispersed Nb-rich MC having a volume of 2.5%. Due to the high hardness (>750 HV30) in combination with high resistance to pitting corrosion, the steel exhibits outstanding tribocorrosion resistance in 0.9% NaCl solution. © 2022 The Authors. Steel Research International published by Wiley-VCH GmbH.
    view abstractdoi: 10.1002/srin.202200474
  • 2022 • 973 Practical guide to replica exchange transition interface sampling and forward flux sampling
    Hall, S.W. and Díaz Leines, G. and Sarupria, S. and Rogal, J.
    Journal of Chemical Physics 156 (2022)
    Path sampling approaches have become invaluable tools to explore the mechanisms and dynamics of the so-called rare events that are characterized by transitions between metastable states separated by sizable free energy barriers. Their practical application, in particular to ever more complex molecular systems, is, however, not entirely trivial. Focusing on replica exchange transition interface sampling (RETIS) and forward flux sampling (FFS), we discuss a range of analysis tools that can be used to assess the quality and convergence of such simulations, which is crucial to obtain reliable results. The basic ideas of a step-wise evaluation are exemplified for the study of nucleation in several systems with different complexities, providing a general guide for the critical assessment of RETIS and FFS simulations. © 2022 Author(s).
    view abstractdoi: 10.1063/5.0080053
  • 2022 • 972 High Energy Storage Density in Nanocomposites of P(VDF-TrFE-CFE) Terpolymer and BaZr0.2Ti0.8O3 Nanoparticles
    Hambal, Y. and Shvartsman, V.V. and Michiels, I. and Zhang, Q. and Lupascu, D.C.
    Materials 15 (2022)
    Polymer materials are actively used in dielectric capacitors, in particular for energy storage applications. An enhancement of the stored energy density can be achieved in composites of electroactive polymers and dielectric inorganic fillers with a high dielectric permittivity. In this article, we report on the energy storage characteristics of composites of relaxor terpolymer P(VDF-TrFE-CFE) and BaZr0.2Ti0.8O3 (BZT) nanoparticles. The choice of materials was dictated by their large dielectric permittivity in the vicinity of room temperature. Free-standing composite films, with BZT contents up to 5 vol.%, were prepared by solution casting. The dielectric properties of the composites were investigated over a wide range of frequencies and temperatures. It was shown that the addition of the BZT nanoparticles does not affect the relaxor behavior of the polymer matrix, but significantly increases the dielectric permittivity. The energy storage parameters were estimated from the analysis of the unipolar polarization hysteresis loops. The addition of the BZT filler resulted in the increasing discharge energy density. The best results were achieved for composites with 1.25–2.5 vol.% of BZT. In the range of electric fields to 150 MV/m, the obtained materials demonstrate a superior energy storage density compared to other P(VDF-TFE-CFE) based composites reported in the literature. © 2022 by the authors. Licensee MDPI, Basel, Switzerland.
    view abstractdoi: 10.3390/ma15093151
  • 2022 • 971 Enhanced heterogeneous activation of peroxymonosulfate by Ruddlesden-Popper-type La2CoO4+δ nanoparticles for bisphenol A degradation
    Hammad, M. and Alkan, B. and Al-kamal, A.K. and Kim, C. and Ali, M.Y. and Angel, S. and Wiedemann, H.T.A. and Klippert, D. and Schmidt, T.C. and Kay, C.W.M. and Wiggers, H.
    Chemical Engineering Journal 429 (2022)
    The scalable synthesis of stable catalysts for environmental remediation applications remains challenging. Nonetheless, metal leaching is a serious environmental issue hindering the practical application of transition-metal based catalysts including Co-based catalysts. Herein, for the first time, we describe a facile one-step and scalable spray-flame synthesis of high surface area La2CoO4+δ nanoparticles containing excess oxygen interstitials (+δ) and use them as a stable and efficient catalyst for activating peroxymonosulfate (PMS) towards the degradation of bisphenol A. Importantly, the La2CoO4+δ catalyst exhibits higher catalytic degradation of bisphenol A (95% in 20 min) and stability than LaCoO3–x nanoparticles (60%) in the peroxymonosulfate activation system. The high content of Co2+ in the structure showed a strong impact on the catalytic performance of the La2CoO4+δ + PMS system. Despite its high specific surface area, our results showed a very low amount of leached cobalt (less than 0.04 mg/L in 30 min), distinguishing it as a material with high chemical stability. According to the radical quenching experiments and the electron paramagnetic resonance technology, SO4[rad]–, [rad]OH, and 1O2 were generated and SO4[rad]– played a dominant role in bisphenol A degradation. Moreover, the La2CoO4+δ + PMS system maintained conspicuous catalytic performance for the degradation of other organic pollutants including methyl orange, rhodamine B, and methylene blue. Overall, our results showed that we developed a new synthesis method for stable La2CoO4+δ nanoparticles that can be used as a highly active heterogeneous catalyst for PMS-assisted oxidation of organic pollutants. © 2021 Elsevier B.V.
    view abstractdoi: 10.1016/j.cej.2021.131447
  • 2022 • 970 Toward the Integration of a Silicon/Graphite Anode-Based Lithium-Ion Battery in Photovoltaic Charging Battery Systems
    Hamzelui, N. and Kin, L.-C. and Köhler, J. and Astakhov, O. and Liu, Z. and Kirchartz, T. and Rau, U. and Eshetu, G.G. and Merdzhanova, T. and Figgemeier, E.
    ACS Omega 7 27532-27541 (2022)
    Solar photovoltaic (PV) energy generation is highly dependent on weather conditions and only applicable when the sun is shining during the daytime, leading to a mismatch between demand and supply. Merging PVs with battery storage is the straightforward route to counteract the intermittent nature of solar generation. Capacity (or energy density), overall efficiency, and stability at elevated temperatures are among key battery performance metrics for an integrated PV-battery system. The performance of high-capacity silicon (Si)/graphite (Gr) anode and LiNi0.6Mn0.2Co0.2O2(NMC622) cathode cells at room temperature, 45, and 60 °C working temperatures for PV modules are explored. The electrochemical performance of both half and full cells are tested using a specially formulated electrolyte, 1 M LiPF6in ethylene carbonate: diethyl carbonate, with 5 wt % fluoroethylene carbonate, 2 wt % vinylene carbonate, and 1 wt % (2-cyanoethyl)triethoxysilane. To demonstrate solar charging, perovskite solar cells (PSCs) are coupled to the developed batteries, following the evaluation of each device. An overall efficiency of 8.74% under standard PV test conditions is obtained for the PSC charged lithium-ion battery via the direct-current-direct-current converter, showing the promising applicability of silicon/graphite-based anodes in the PV-battery integrated system. © 2022 American Chemical Society. All rights reserved.
    view abstractdoi: 10.1021/acsomega.2c02940
  • 2022 • 969 A mechanically strong and ductile soft magnet with extremely low coercivity
    Han, L. and Maccari, F. and Souza Filho, I.R. and Peter, N.J. and Wei, Y. and Gault, B. and Gutfleisch, O. and Li, Z. and Raabe, D.
    Nature 608 310-316 (2022)
    Soft magnetic materials (SMMs) serve in electrical applications and sustainable energy supply, allowing magnetic flux variation in response to changes in applied magnetic field, at low energy loss1. The electrification of transport, households and manufacturing leads to an increase in energy consumption owing to hysteresis losses2. Therefore, minimizing coercivity, which scales these losses, is crucial3. Yet meeting this target alone is not enough: SMMs in electrical engines must withstand severe mechanical loads; that is, the alloys need high strength and ductility4. This is a fundamental design challenge, as most methods that enhance strength introduce stress fields that can pin magnetic domains, thus increasing coercivity and hysteresis losses5. Here we introduce an approach to overcome this dilemma. We have designed a Fe–Co–Ni–Ta–Al multicomponent alloy (MCA) with ferromagnetic matrix and paramagnetic coherent nanoparticles (about 91 nm in size and around 55% volume fraction). They impede dislocation motion, enhancing strength and ductility. Their small size, low coherency stress and small magnetostatic energy create an interaction volume below the magnetic domain wall width, leading to minimal domain wall pinning, thus maintaining the soft magnetic properties. The alloy has a tensile strength of 1,336 MPa at 54% tensile elongation, extremely low coercivity of 78 A m−1 (less than 1 Oe), moderate saturation magnetization of 100 A m2 kg−1 and high electrical resistivity of 103 μΩ cm. © 2022, The Author(s).
    view abstractdoi: 10.1038/s41586-022-04935-3
  • 2022 • 968 Terahertz conductivity of nanograined bulk Bi2Te3
    Han, J.W. and Izadi, S. and Salloum, S. and Wolff, U. and Schnatmann, L. and Bhattacharya, A. and Asaithambi, A. and Matschy, S. and Schlorb, H. and Reith, H. and Perez, N. and Nielsen, K. and Schulz, S. and Schierning, G. and Mit...
    2022 Conference on Lasers and Electro-Optics, CLEO 2022 - Proceedings (2022)
    Nanograined Bi2Te3 offers a large surface-to-volume ratio, making it an interesting material to employ the high mobility surface states for devices. We present THz spectroscopic measurements to reveal the role of the surface carriers. © Optica Publishing Group 2022, © 2022 The Author(s)
    view abstract
  • 2022 • 967 Bioinspired iron porphyrins with appended poly-pyridine/amine units for boosted electrocatalytic CO2 reduction reaction
    Han, J. and Wang, N. and Li, X. and Lei, H. and Wang, Y. and Guo, H. and Jin, X. and Zhang, Q. and Peng, X. and Zhang, X.-P. and Zhang, W. and Apfel, U.-P. and Cao, R.
    eScience 2 623-631 (2022)
    doi: 10.1016/j.esci.2022.06.003
  • 2022 • 966 Investigation of phase transformation related electrical conductivity of long-term heat treated aluminium electrolysis cathodes
    Hankel, J. and Kernebeck, S. and Deuerler, F. and Weber, S.
    SN Applied Sciences 4 (2022)
    This study presents an investigation on the specific electrical conductivity of the cathode materials used in an aluminium electrolysis cell over a temperature range between room temperature and 950 °C. Those materials are subjected to a diffusion related aging process due to the high operating temperature of the cell, leading to a change in chemical composition and microstructure. The materials were investigated both in the initial state before use in an aluminium electrolysis cell and after an operating period of 5 years. It is shown that the changes in chemical composition and thus also in microstructure over the service life at elevated operating temperature exert an effect on the electrical conductivity. In addition, calculations based on thermodynamic data were used to relate phase transformations to the changes in electrical conductivity. On the one hand, the electrical conductivity of the collector bar at 950 °C is reduced by about 11% after 5 years of service. On the other hand, the ageing process has a positive influence on the cast iron with an increased conductivity by about 41% at 950 °C. The results provide an understanding how diffusion related processes in the cathode materials affect energy efficiency of the aluminium electrolysis cell. © 2022, The Author(s).
    view abstractdoi: 10.1007/s42452-022-05101-0
  • 2022 • 965 Processability of a Hot Work Tool Steel Powder Mixture in Laser-Based Powder Bed Fusion
    Hantke, N. and Großwendt, F. and Strauch, A. and Fechte-Heinen, R. and Röttger, A. and Theisen, W. and Weber, S. and Sehrt, J.T.
    Materials 15 (2022)
    Powder bed fusion of metals using a laser beam system (PBF-LB/M) of highly complex and filigree parts made of tool steels is becoming more important for many industrial applications and scientific investigations. To achieve high density and sufficient chemical homogeneity, pre-alloyed gas-atomized spherical powder feedstock is used. For high-performance materials such as tool steels, the number of commercially available starting powders is limited due to the susceptibility to crack formation in carbon-bearing steels. Furthermore, scientific alloy development in combination with gas-atomization is a cost-intensive process which requires high experimental effort. To overcome these drawbacks, this investigation describes the adaption of a hot work tool steel for crack-free PBFLB/M-fabrication without any preheating as well as an alternative alloying strategy which implies the individual admixing of low-cost aspherical elemental powders and ferroalloy particles with gas-atomized pure iron powder. It is shown that the PBF-LB/M-fabrication of this powder mixture is technically feasible, even though the partly irregular-shaped powder particles reduce the flowability and the laser reflectance compared to a gas-atomized reference powder. Moreover, some high-melting alloying ingredients of the admixed powder remain unmolten within the microstructure. To analyze the laser energy input in detail, the second part of the investigation focuses on the characterization of the individual laser light reflectance of the admixed alloy, the gas-atomized reference powder and the individual alloying elements and ferroalloys. © 2022 by the authors. Licensee MDPI, Basel, Switzerland.
    view abstractdoi: 10.3390/ma15072658
  • 2022 • 964 Design Principles for Shared Digital Twins in Distributed Systems
    Haße, H. and van der Valk, H. and Möller, F. and Otto, B.
    Business and Information Systems Engineering (2022)
    Digital Twins offer considerable potential for cross-company networks. Recent research primarily focuses on using Digital Twins within the limits of a single organization. However, Shared Digital Twins extend application boundaries to cross-company utilization through their ability to act as a hub to share data. This results in the need to consider additional design dimensions which help practitioners design Digital Twins tailored for inter-company use. The article addresses precisely that issue as it investigates how Shared Digital Twins should be designed to achieve business success. For this purpose, the article proposes a set of design principles for Shared Digital Twins stemming from a qualitative interview study with 18 industry experts. The interview study is the primary data source for formulating and evaluating the design principles. © 2022, The Author(s).
    view abstractdoi: 10.1007/s12599-022-00751-1
  • 2022 • 963 Silver Thin-Film Electrodes Grown by Low-Temperature Plasma-Enhanced Spatial Atomic Layer Deposition at Atmospheric Pressure
    Hasselmann, T. and Misimi, B. and Boysen, N. and Zanders, D. and Wree, J.-L. and Rogalla, D. and Haeger, T. and Zimmermann, F. and Brinkmann, K.O. and Schädler, S. and Theirich, D. and Heiderhoff, R. and Devi, A. and Riedl, T.
    Advanced Materials Technologies (2022)
    doi: 10.1002/admt.202200796
  • 2022 • 962 Calculations regarding the stress on the segment tube in the longitudinal direction of the tunnel caused by the annular gap grouting [Berechnungen zur Beanspruchung der Tübbingröhre in Tunnellängsrichtung infolge der Ringspaltverpressung]
    Hausmann, M. and Mähner, D. and Perau, E.
    Bauingenieur 97 331-340 (2022)
    This paper deals with the loading and deforma-tion of the tunnel cross section perpendicular to the longitudinal axis during the construction phase of a tunnel in shield dri-ving in the context of annular gap filling with liquid mortar. Since in some cases damage to the lining segments is de-tected which occurs early after a ring has been constructed, there is a technical and economic motivation for a better un-derstanding of the internal stresses in the tunnel in the longitudinal direction of the tunnel during the construction phase. The aim of the present work is to develop a coherent calculation method to consider this situation on the basis of analytical approaches and to identify, describe and quantify relevant aspects which influence the loading of the tunnel during the construction phase. In the present work, analytical approaches are used for the most part to ensure a continuous, comprehen-sible and transparent calculation method. © 2022, VDI Fachmedien GmBH & Co. KG. All rights reserved.
    view abstractdoi: 10.37544/0005-6650-2022-10-69
  • 2022 • 961 Splicing the active phases of copper/cobalt-based catalysts achieves high-rate tandem electroreduction of nitrate to ammonia
    He, W. and Zhang, J. and Dieckhöfer, S. and Varhade, S. and Brix, A.C. and Lielpetere, A. and Seisel, S. and Junqueira, J.R.C. and Schuhmann, W.
    Nature Communications 13 (2022)
    Electrocatalytic recycling of waste nitrate (NO3−) to valuable ammonia (NH3) at ambient conditions is a green and appealing alternative to the Haber−Bosch process. However, the reaction requires multi-step electron and proton transfer, making it a grand challenge to drive high-rate NH3 synthesis in an energy-efficient way. Herein, we present a design concept of tandem catalysts, which involves coupling intermediate phases of different transition metals, existing at low applied overpotentials, as cooperative active sites that enable cascade NO3−-to-NH3 conversion, in turn avoiding the generally encountered scaling relations. We implement the concept by electrochemical transformation of Cu−Co binary sulfides into potential-dependent core−shell Cu/CuOx and Co/CoO phases. Electrochemical evaluation, kinetic studies, and in−situ Raman spectra reveal that the inner Cu/CuOx phases preferentially catalyze NO3− reduction to NO2−, which is rapidly reduced to NH3 at the nearby Co/CoO shell. This unique tandem catalyst system leads to a NO3−-to-NH3 Faradaic efficiency of 93.3 ± 2.1% in a wide range of NO3− concentrations at pH 13, a high NH3 yield rate of 1.17 mmol cm−2 h−1 in 0.1 M NO3− at −0.175 V vs. RHE, and a half-cell energy efficiency of ~36%, surpassing most previous reports. © 2022, The Author(s).
    view abstractdoi: 10.1038/s41467-022-28728-4
  • 2022 • 960 Computational electrochemistry focusing on nanostructured catalysts: challenges and opportunities
    He, T. and Exner, K.S.
    Materials Today Energy 28 (2022)
    doi: 10.1016/j.mtener.2022.101083
  • 2022 • 959 Pair-amplitude dynamics in strongly coupled superconductor-quantum dot hybrids
    Heckschen, M. and Sothmann, B.
    Physical Review B 105 (2022)
    We consider a three-terminal system consisting of a quantum dot strongly coupled to two superconducting reservoirs in the infinite-gap limit and weakly coupled to a normal metal. Using a real-time diagrammatic approach, we calculate the dynamics of the proximity-induced pair amplitude on the quantum dot. We find that after a quench the pair amplitude shows pronounced oscillations with a frequency determined by the coupling to the superconductors. In addition, it decays exponentially on a timescale set by the coupling to the normal metal. Strong oscillations of the pair amplitude occur also when the system is periodically driven both in the adiabatic and fast-driving limit. We relate the dynamics of the pair amplitude to the Josephson and Andreev current through the dot to demonstrate that it is an experimentally accessible quantity. © 2022 American Physical Society.
    view abstractdoi: 10.1103/PhysRevB.105.045420
  • 2022 • 958 The effect of deviations from precise [001] tensile direction on creep of Ni-base single crystal superalloys
    Heep, L. and Bürger, D. and Bonnekoh, C. and Wollgramm, P. and Dlouhy, A. and Eggeler, G.
    Scripta Materialia 207 (2022)
    Low temperature (1023 K) high stress (800 MPa) tensile creep behavior of the superalloy single crystal ERBO-1 (CMSX-4 type) is investigated. Three loading directions are compared: precise [001] and 15 ° deviations from [001] towards [111] and [011]. It is found that creep rates ε˙ scale as ε˙[001]→[111]&gt;ε˙[001]&gt;ε˙[001]→[011]already in the early stages of creep (ε≤1%), where dislocation network formation and planar fault intersections cannot rationalize the observed rate effects. An analysis based on Peach-Köhler force calculations suggests, that fast creep rates are observed, when dislocations from two octahedral systems, which are required to react and form the leading part of a planar fault ribbon in the γ’-phase, experience similar driving forces. Creep data, micromechanical calculations and TEM results are in good qualitative agreement. From a technological point of view, the results show that while 15 ° deviations from [001] towards [011] can be tolerated, deviations towards [111] must be avoided. © 2021
    view abstractdoi: 10.1016/j.scriptamat.2021.114274
  • 2022 • 957 Spin-Lasing in Bimodal Quantum Dot Micropillar Cavities
    Heermeier, N. and Heuser, T. and Große, J. and Jung, N. and Kaganskiy, A. and Lindemann, M. and Gerhardt, N.C. and Hofmann, M.R. and Reitzenstein, S.
    Laser and Photonics Reviews 16 (2022)
    doi: 10.1002/lpor.202100585
  • 2022 • 956 Boosting the overall electrochemical water splitting performance of pentlandites through non-metallic heteroatom incorporation
    Hegazy, M.B.Z. and Harrath, K. and Tetzlaff, D. and Smialkowski, M. and Siegmund, D. and Li, J. and Cao, R. and Apfel, U.-P.
    iScience 25 (2022)
    doi: 10.1016/j.isci.2022.105148
  • 2022 • 955 Temperature-dependent spin-resolved electronic structure of EuO thin films
    Heider, T. and Gerber, T. and Köksal, O. and Eschbach, M. and Młyńczak, E. and Lömker, P. and Gospodaric, P. and Gehlmann, M. and Plötzing, M. and Pentcheva, R. and Plucinski, L. and Schneider, C.M. and Müller, M.
    Physical Review B 106 (2022)
    The electronic structure of the ferromagnetic semiconductor EuO is investigated by means of spin- and angle-resolved photoemission spectroscopy (spin-ARPES) and density functional theory. EuO exhibits unique properties of hosting both weakly dispersive nearly fully polarized Eu 4f bands, as well as O 2p levels indirectly exchange-split by the interaction with Eu nearest neighbors. Our temperature-dependent spin-ARPES data directly demonstrate the exchange splitting in O 2p and its vanishing at the Curie temperature. Our calculations with a Hubbard U term reveal a complex nature of the local exchange splitting on the oxygen site and in conduction bands. We discuss the mechanisms of indirect exchange in the O 2p levels by analyzing the orbital resolved band characters in ferromagnetic and antiferromagnetic phases. The directional effects due to spin-orbit coupling are predicted theoretically to be significant in particular in the Eu 4f band manifold. The analysis of the shape of spin-resolved spectra in the Eu 4f spectral region reveals signatures of hybridization with O 2p states, in agreement with the theoretical predictions. We also analyze spectral changes in the spin-integrated spectra throughout the Curie temperature, and demonstrate that they derive from both the magnetic phase transition and effects due to sample aging, unavoidable for this highly reactive material. © 2022 American Physical Society.
    view abstractdoi: 10.1103/PhysRevB.106.054424
  • 2022 • 954 Generation of terahertz transients from Co2Fe0.4Mn0.6Si Heusler alloy/heavy-metal bilayers
    Heidtfeld, S. and Adam, R. and Kubota, T. and Takanashi, K. and Cao, D. and Schmitz-Antoniak, C. and Bürgler, D.E. and Wang, F. and Greb, C. and Chen, G. and Komissarov, I. and Hardtdegen, H. and Mikulics, M. and Sobolewski, R. a...
    Journal of Magnetism and Magnetic Materials 547 (2022)
    We generated pulses of electromagnetic radiation with a frequency content up to three terahertz (THz) by optical excitation of Co2Fe0.4Mn0.6Si Heusler alloy/heavy metal bilayers (CFMS/HM) using fs-laser pulses. We attribute the generation process to the conversion of a spin current, generated by the illumination with a fs-laser pulse, to a charge current via the inverse spin Hall effect. We compared the THz emission efficiency in CFMS/Pt and CFMS/Ta bilayers due to their high spin–orbit coupling of Pt and Ta. Surprisingly, our data reveal that CFMS/Pt shows substantially larger THz amplitudes compared to CFMS/Ta. Both bilayers exhibit a tunability of the THz amplitude by external magnetic field both at 300 K and 100 K. Ferromagnetic resonance measurements demonstrate that CFMS/Ta has a high effective spin mixing conductance, describing the efficiency of interfacial spin transport. We observe that the efficiency of the THz radiation cannot be solely described by the spin–orbit coupling strength and the spin diffusion length in the HM material plays an important role. © 2021 Elsevier B.V.
    view abstractdoi: 10.1016/j.jmmm.2021.168791
  • 2022 • 953 Low Cycle Fatigue Performance of Additively Processed and Heat-Treated Ti-6Al-7Nb Alloy for Biomedical Applications
    Hein, M. and Kokalj, D. and Dias, N.F.L. and Stangier, D. and Oltmanns, H. and Pramanik, S. and Kietzmann, M. and Hoyer, K.-P. and Meißner, J. and Tillmann, W. and Schaper, M.
    Metals 12 (2022)
    In biomedical engineering, laser powder bed fusion is an advanced manufacturing technology, which enables, for example, the production of patient-customized implants with complex geometries. Ti-6Al-7Nb shows promising improvements, especially regarding biocompatibility, compared with other titanium alloys. The biocompatible features are investigated employing cytocompatibility and antibacterial examinations on Al2O3-blasted and untreated surfaces. The mechanical properties of additively manufactured Ti-6Al-7Nb are evaluated in as-built and heat-treated conditions. Recrystallization annealing (925◦C for 4 h), β annealing (1050◦C for 2 h), as well as stress relieving (600◦C for 4 h) are applied. For microstructural investigation, scanning and transmission electron microscopy are performed. The different microstructures and the mechanical properties are compared. Mechanical behavior is determined based on quasi-static tensile tests and strain-controlled low cycle fatigue tests with total strain amplitudes εA of 0.35%, 0.5%, and 0.8%. The as-built and stress-relieved conditions meet the mechanical demands for the tensile properties of the international standard ISO 5832-11. Based on the Coffin–Manson–Basquin relation, fatigue strength and ductility coefficients, as well as exponents, are determined to examine fatigue life for the different conditions. The stress-relieved condition exhibits, overall, the best properties regarding monotonic tensile and cyclic fatigue behavior. © 2022 by the authors. Licensee MDPI, Basel, Switzerland.
    view abstractdoi: 10.3390/met12010122
  • 2022 • 952 Heat Treatments of Metastable β Titanium Alloy Ti-24Nb-4Zr-8Sn Processed by Laser Powder Bed Fusion
    Hein, M. and Lopes Dias, N.F. and Pramanik, S. and Stangier, D. and Hoyer, K.-P. and Tillmann, W. and Schaper, M.
    Materials 15 (2022)
    Titanium alloys, especially β alloys, are favorable as implant materials due to their promising combination of low Young’s modulus, high strength, corrosion resistance, and biocompatibility. In particular, the low Young’s moduli reduce the risk of stress shielding and implant loosening. The processing of Ti-24Nb-4Zr-8Sn through laser powder bed fusion is presented. The specimens were heat-treated, and the microstructure was investigated using X-ray diffraction, scanning electron microscopy, and transmission electron microscopy. The mechanical properties were determined by hardness and tensile tests. The microstructures reveal a mainly β microstructure with α” formation for high cooling rates and α precipitates after moderate cooling rates or aging. The as-built and α” phase containing conditions exhibit a hardness around 225 HV5, yield strengths (YS) from 340 to 490 MPa, ultimate tensile strengths (UTS) around 706 MPa, fracture elongations around 20%, and Young’s moduli about 50 GPa. The α precipitates containing conditions reveal a hardness around 297 HV5, YS around 812 MPa, UTS from 871 to 931 MPa, fracture elongations around 12%, and Young’s moduli about 75 GPa. Ti-24Nb-4Zr-8Sn exhibits, depending on the heat treatment, promising properties regarding the material behavior and the opportunity to tailor the mechanical performance as a low modulus, high strength implant material. © 2022 by the authors. Licensee MDPI, Basel, Switzerland.
    view abstractdoi: 10.3390/ma15113774
  • 2022 • 951 ADAPTIVE GDSW COARSE SPACES OF REDUCED DIMENSION FOR OVERLAPPING SCHWARZ METHODS
    Heinlein, A. and Klawonn, A. and Knepper, J. and Rheinbach, O. and Widlund, O.B.
    SIAM Journal on Scientific Computing 44 A1176-A1204 (2022)
    A new reduced-dimension adaptive generalized Dryja-Smith-Widlund (GDSW) overlapping Schwarz method for linear second-order elliptic problems in three dimensions is introduced. It is robust with respect to large contrasts of the coefficients of the partial differential equations. The condition number bound of the new method is shown to be independent of the coefficient contrast and only dependent on a user-prescribed tolerance. The interface of the nonoverlapping domain decomposition is partitioned into nonoverlapping patches. The new coarse space is obtained by selecting a few eigenvectors of certain local eigenproblems which are defined on these patches. These eigenmodes are energy-minimally extended to the interior of the nonoverlapping subdomains and added to the coarse space. By using a new interface decomposition, the reduced-dimension adaptive GDSW overlapping Schwarz method usually has a smaller coarse space than existing GDSW and adaptive GDSW domain decomposition methods. A robust condition number estimate is proven for the new reduced-dimension adaptive GDSW method which is also valid for existing adaptive GDSW methods. Numerical results for the equations of isotropic linear elasticity in three dimensions confirming the theoretical findings are presented. © 2022 Alexander Heinlein, Axel Klawonn, Jascha Knepper, Oliver Rheinbach, Olof B. Widlund
    view abstractdoi: 10.1137/20M1364540
  • 2022 • 950 Predicting the Geometric Location of Critical Edges in Adaptive GDSW Overlapping Domain Decomposition Methods Using Deep Learning
    Heinlein, A. and Klawonn, A. and Lanser, M. and Weber, J.
    Lecture Notes in Computational Science and Engineering 145 307-315 (2022)
    doi: 10.1007/978-3-030-95025-5_32
  • 2022 • 949 A Three-Level Extension for Fast and Robust Overlapping Schwarz (FROSch) Preconditioners with Reduced Dimensional Coarse Space
    Heinlein, A. and Klawonn, A. and Rheinbach, O. and Röver, F.
    Lecture Notes in Computational Science and Engineering 145 505-513 (2022)
    doi: 10.1007/978-3-030-95025-5_54
  • 2022 • 948 Surrogate Models for the Prediction of Damping Ratios in Coupled Acoustoelastic Rotor-Cavity Systems
    Heinrich, C.R. and Unglaube, T. and Beirow, B. and Brillert, D. and Steff, K. and Petry, N.
    Journal of Engineering for Gas Turbines and Power 144 (2022)
    doi: 10.1115/1.4054567
  • 2022 • 947 Spoke-resolved electron density, temperature and potential in direct current magnetron sputtering and HiPIMS discharges
    Held, J. and George, M. and von Keudell, A.
    Plasma Sources Science and Technology 31 (2022)
    Spokes are long wavelength oscillations observed in the magnetized region of direct current magnetron sputtering (DCMS), high power impulse magnetron sputtering (HiPIMS), as well as other E → × B → discharges. Spokes rotate in front of the cathode with velocities between about 2 km s−1 and 15 km s−1, making it difficult to perform quantitative measurements. This is overcome by synchronizing Langmuir probe measurements to the movement of spokes in DCMS to obtain the probe current-voltage (I-V) characteristic without averaging out the spoke influence. The I-V curves are then evaluated using magnetized probe theory, revealing the strong plasma parameter modulations, caused by the spokes. The plasma density was found to oscillate between 2.5 × 1016 m−3 and 1.7 × 1017 m−3, which corresponds to a modulation strength of more than 70% or an almost seven times increase of density. In good agreement with previous work, a plasma potential minimum of −55 V is found ahead of the spoke followed by a sudden increase to about 2 V inside the spoke. The electron temperature was found to oscillate between 3 eV and 7 eV. On top of that oscillation, electrons experience a sudden energy increase as they move inside the spoke, crossing the potential jump at the leading edge for the spoke. On basis of these observations a model is presented to explain spokes in DCMS. These results are then compared to HiPIMS spokes under otherwise similar conditions. The plasma parameter modulation found for HiPIMS is much weaker than for DCMS, which is explained by the higher collision frequency for electrons in HiPIMS plasmas. © 2022 The Author(s). Published by IOP Publishing Ltd.
    view abstractdoi: 10.1088/1361-6595/ac87ce
  • 2022 • 946 Geminal C-Cl and Si-Cl bond activation of chloromethanes and chlorosilanes by gallanediyl LGa
    Helling, C. and Ganesamoorthy, C. and Wölper, C. and Schulz, S.
    Dalton Transactions 51 2050-2058 (2022)
    The activation of relatively inert E-X σ-bonds by low-valent main group metal complexes is receiving increasing interest. We here confirm the promising potential of gallanediyl LGa (L = HC[C(Me)N(Dip)]2, Dip = 2,6-i-Pr2C6H3) to activate E-Cl (E = C, Si) σ-bonds of group 14 element compounds. Equimolar reactions of LGa with chloromethanes and chlorosilanes EHxCl4-x (E = C, x = 0-2; E = Si, x = 0, 1) occurred with E-Cl bond insertion and formation of gallylmethanes and -silanes L(Cl)GaEHxCl3-x (E = C, x = 2 (1), 1 (2), 0 (3); E = Si, x = 1 (4)). In contrast, consecutive insertion into a geminal E-Cl bond was observed with two equivalents of LGa, yielding digallyl complexes [L(Cl)Ga]2EHxCl2-x (E = C, x = 2 (5); E = Si, x = 1 (6), 0 (7)). Compounds 1-7 were characterized by heteronuclear NMR (1H, 13C, 29Si (4, 6)), IR spectroscopy and elemental analysis, and their solid-state structures were determined by single-crystal X-ray diffraction (sc-XRD). © 2022 The Royal Society of Chemistry.
    view abstractdoi: 10.1039/d1dt04192d
  • 2022 • 945 Sequential Reduction of Borylstibane to an Electronically Nonsymmetric Diboryldistibene Radical Anion
    Helling, C. and Haak, J. and Wölper, C. and Cutsail, G.E. and Schulz, S.
    Inorganic Chemistry 61 5124-5132 (2022)
    Understanding the formation of metal-metal bonds and their electronic structures is still a scientific task. We herein report on the stepwise synthesis of boryl-substituted antimony compounds in which the antimony atoms adopt four different oxidation states (+III, +II, +I, +I/0). Sb-C bond homolysis of Cp*[(HCNDip)2B]SbCl (1; Cp∗ = C5Me5; Dip = 2,6-iPr2C6H3) gave diboryldichlorodistibane [(HCNDip)2BSbCl]2(2), which reacted with KC8to form diboryldistibene [(HCNDip)2BSb]2(3) and traces of cyclotetrastibane [(HCNDip)2B]3Sb4Cl (5). One-electron reduction of 3 yielded the potassium salt of the diboryldistibene radical anion [(HCNDip)2BSb]2˙-, [K(18-c-6)(OEt2)][{(HCNDip)2BSb}2] (4), which exhibits an unprecedented inequivalent spin localization on the Sb-Sb bond and hence an unsymmetric electronic structure. Compounds 1-4 were characterized by heteronuclear nuclear magnetic resonance (NMR) (1H, 13C, 11B), infrared (IR), ultraviolet-visible (UV-vis) spectroscopy (3, 4), and single crystal X-ray diffraction (sc-XRD, 1-5), while the bonding nature of 3 and 4 was analyzed by quantum chemical calculations. EPR spectroscopy resolves the dissimilar Sb hyperfine tensors of 4, reflecting the inequivalent spin distribution, setting 4 uniquely apart from all previously characterized dipnictene radical anions. © 2022 American Chemical Society. All rights reserved.
    view abstractdoi: 10.1021/acs.inorgchem.2c00251
  • 2022 • 944 Gallium, Indium, and Thallium
    Helling, C. and Schulz, S.
    Comprehensive Organometallic Chemistry IV: Volume 1-15 1-15 370-406 (2022)
    doi: 10.1016/B978-0-12-820206-7.00126-8
  • 2022 • 943 Deep learning method for analysis and segmentation of fatigue damage in X-ray computed tomography data for fiber-reinforced polymers
    Helwing, R. and Hülsbusch, D. and Walther, F.
    Composites Science and Technology 230 (2022)
    doi: 10.1016/j.compscitech.2022.109781
  • 2022 • 942 Photostability of polylactide with respect to blue LED radiation at very high irradiance and ambient temperature
    Hemmerich, M. and Scholz, R. and Meyer, J. and Walther, F.
    Materials Today Communications 31 (2022)
    For an overall sustainable development of lighting systems, it is crucial to establish alternatives to fossil based optical plastics. One biodegradable plastic alternative, based exclusively on renewable raw materials and having outstanding optical properties, could be the bioplastic polylactide (PLA). In order to evaluate the stability of PLA under the influence of extreme levels of optical LED radiation (λmax = 450 nm, FWHM = 16.3 nm), aging experiments were carried out over a period of 5000 h (~ 7 months) using an innovative self-developed test setup. As a reference the widely used optical plastic polycarbonate (PC) was aged under the same conditions. The novel test setup allowed aging tests at low temperatures of 23.0 and 36.1 °C (below the crystallization temperature of PLA) with irradiances of 7.9 and 16.1 kW/m2, respectively. Photodegradation tests in which temperature can be varied virtually independent of radiant flux were performed. To the best of our knowledge this is a first in degradation experiments. By this, aging can be attributed to more radiation- or temperature-related phenomena. Before, during, and after aging, optical, mechanical and chromatographic methods were used to analyze the samples. PLA was found to be largely resistant to visible blue LED radiation under the selected aging conditions. Only an increase in surface hardness and stiffness, indicating embrittlement, was observed. In contrast, even at the low temperatures used in these experiments, PC shows a significant decrease in transmission in the short-wavelength range of up to 17.0% after prolonged aging. Moreover, known degradation products (by FTIR spectroscopy), a decrease in molar mass (5.1%) and a trend increase in Martens hardness and indentation modulus, were detected for all PC of samples. © 2022 Elsevier Ltd
    view abstractdoi: 10.1016/j.mtcomm.2022.103307
  • 2022 • 941 Durability of the optical plastic polycarbonate under modulated blue LED irradiation at different duty cycles
    Hemmerich, M. and Klein, D.A. and Meyer, J. and Walther, F.
    Optical Materials 131 (2022)
    In order to provide longer LED lifetimes, all LED-related components, including lenses and other optical components, need to be adapted to increasing radiation levels. Pulse width modulation (PWM) is an easy-to-implement method for driving and dimming LEDs and could be a cost-effective way to extend the lifetime of optical components installed in conjunction with the LED. In this study, polycarbonate (PC) samples were artificially aged with high-power blue LEDs using different driving modes in a newly developed test setup. The LEDs were pulse-width modulated in three different modes (50% duty cycle, 25% duty cycle, and continuous wave (CW)), while emitting the same optical power. Optical light microscopy, UV/vis spectroscopy, FTIR spectroscopy and gel permeation chromatography were performed to measure transmittance changes and general aging effects of the samples. The results indicate a substantial correlation of aging with the mode of exposure. It is found that the samples age most severely under CW irradiation, as both the decrease in transmission (at 295 nm wavelength, after 1500 h) and the sample temperature, and thus the degradation, are highest. FTIR spectroscopy showed the expected results for optical aging under LED irradiation, again the changes tended to be more pronounced for the samples irradiated without PWM. Gel permeation chromatography shows a decrease in the weight averaged molar mass, once more with the CW irradiated samples exhibiting the most significant decrease. However, optical light microscopy did not reveal any significant aging effects on the sample surface. Overall, modulation of the LED, and in particular a reduction of the duty cycle, has a positive effect on the durability of optical plastics at similar radiative energy loads. In order to explain the different aging behavior of the samples under the different driving modes, a model of the time-related temperature changes in the material during the heating phase at different duty cycles is proposed. © 2022 Elsevier B.V.
    view abstractdoi: 10.1016/j.optmat.2022.112713
  • 2022 • 940 Role of geochemical protoenzymes (geozymes) in primordial metabolism: specific abiotic hydride transfer by metals to the biological redox cofactor NAD+
    Henriques Pereira, D.P. and Leethaus, J. and Beyazay, T. and do Nascimento Vieira, A. and Kleinermanns, K. and Tüysüz, H. and Martin, W.F. and Preiner, M.
    FEBS Journal (2022)
    Hydrogen gas, H2, is generated in serpentinizing hydrothermal systems, where it has supplied electrons and energy for microbial communities since there was liquid water on Earth. In modern metabolism, H2 is converted by hydrogenases into organically bound hydrides (H–), for example, the cofactor NADH. It transfers hydrides among molecules, serving as an activated and biologically harnessed form of H2. In serpentinizing systems, minerals can also bind hydrides and could, in principle, have acted as inorganic hydride donors—possibly as a geochemical protoenzyme, a ‘geozyme’— at the origin of metabolism. To test this idea, we investigated the ability of H2 to reduce NAD+ in the presence of iron (Fe), cobalt (Co) and nickel (Ni), metals that occur in serpentinizing systems. In the presence of H2, all three metals specifically reduce NAD+ to the biologically relevant form, 1,4-NADH, with up to 100% conversion rates within a few hours under alkaline aqueous conditions at 40 °C. Using Henry's law, the partial pressure of H2 in our reactions corresponds to 3.6 mm, a concentration observed in many modern serpentinizing systems. While the reduction of NAD+ by Ni is strictly H2-dependent, experiments in heavy water (2H2O) indicate that native Fe can reduce NAD+ both with and without H2. The results establish a mechanistic connection between abiotic and biotic hydride donors, indicating that geochemically catalysed, H2-dependent NAD+ reduction could have preceded the hydrogenase-dependent reaction in evolution. © 2022 The Authors. The FEBS Journal published by John Wiley & Sons Ltd on behalf of Federation of European Biochemical Societies
    view abstractdoi: 10.1111/febs.16329
  • 2022 • 939 A Hessian-based assessment of atomic forces for training machine learning interatomic potentials
    Herbold, M. and Behler, J.
    Journal of Chemical Physics 156 (2022)
    In recent years, many types of machine learning potentials (MLPs) have been introduced, which are able to represent high-dimensional potential-energy surfaces (PESs) with close to first-principles accuracy. Most current MLPs rely on atomic energy contributions given as a function of the local chemical environments. Frequently, in addition to total energies, atomic forces are also used to construct the potentials, as they provide detailed local information about the PES. Since many systems are too large for electronic structure calculations, obtaining reliable reference forces from smaller subsystems, such as molecular fragments or clusters, can substantially simplify the construction of the training sets. Here, we propose a method to determine structurally converged molecular fragments, providing reliable atomic forces based on an analysis of the Hessian. The method, which serves as a locality test and allows us to estimate the importance of long-range interactions, is illustrated for a series of molecular model systems and the metal-organic framework MOF-5 as an example for a complex organic-inorganic hybrid material. © 2022 Author(s).
    view abstractdoi: 10.1063/5.0082952
  • 2022 • 938 SO(4) multicriticality of two-dimensional Dirac fermions
    Herbut, I.F. and Scherer, M.M.
    Physical Review B 106 (2022)
    doi: 10.1103/PhysRevB.106.115136
  • 2022 • 937 Electromechanical Coupling in Electroactive Polymers – a Visual Analysis of a Third-Order Tensor Field
    Hergl, C. and Witt, C. and Nsonga, B. and Menzel, A. and Scheuermann, G.
    IEEE Transactions on Visualization and Computer Graphics 1-15 (2022)
    Electroactive polymers are frequently used in engineering applications due to their ability to change their shape and properties under the influence of an electric field. This process also works vice versa, such that mechanical deformation of the material induces an electric field in the EAP device. This specific behavior makes such materials highly attractive for the construction of actuators and sensors in various application areas. The electromechanical behaviour of electroactive polymers can be described by a third-order coupling tensor, which represents the sensitivity of mechanical stresses concerning the electric field, i.e., it establishes a relation between a second-order and a first-order tensor field. Due to this coupling tensor&#x0027;s complexity and the lack of meaningful visualization methods for third-order tensors in general, an interpretation of the tensor is rather difficult. Thus, the central engineering research question that this contribution deals with is a deeper understanding of electromechanical coupling by analyzing the third-order coupling tensor with the help of specific visualization methods. Starting with a deviatoric decomposition of the tensor, the multipoles of each deviator are visualized, which allows a first insight into this highly complex third-order tensor. In the present contribution, four examples, including electromechanical coupling, are simulated within a finite element framework and subsequently analyzed using the tensor visualization method. IEEE
    view abstractdoi: 10.1109/TVCG.2022.3209328
  • 2022 • 936 Tailoring magnetic anisotropy by graphene-induced selective skyhook effect on 4f-metals
    Herman, A. and Kraus, S. and Tsukamoto, S. and Spieker, L. and Caciuc, V. and Lojewski, T. and Günzing, D. and Dreiser, J. and Delley, B. and Ollefs, K. and Michely, T. and Atodiresei, N. and Wende, H.
    Nanoscale 14 7682-7691 (2022)
    From macroscopic heavy-duty permanent magnets to nanodevices, the precise control of the magnetic properties in rare-earth metals is crucial for many applications used in our daily life. Therefore, a detailed understanding and manipulation of the 4f-metals’ magnetic properties are key to further boosting the functionalization and efficiency of future applications. We present a proof-of-concept approach consisting of a dysprosium-iridium surface alloy in which graphene adsorption allows us to tailor its magnetic properties. By adsorbing graphene onto a long-range ordered two-dimensional dysprosium-iridium surface alloy, the magnetic 4f-metal atoms are selectively lifted from the surface alloy. This selective skyhook effect introduces a giant magnetic anisotropy in dysprosium atoms as a result of manipulating its geometrical structure within the surface alloy. Introducing and proving this concept by our combined theoretical and experimental approach provides an easy and unambiguous understanding of its underlying mechanism. Our study sets the ground for an alternative path on how to modify the crystal field around 4f-atoms and therefore their magnetic anisotropies. © 2022 The Royal Society of Chemistry.
    view abstractdoi: 10.1039/d2nr01458k
  • 2022 • 935 Challenges and limits of upconversion nanoparticles for cationic photopolymerization with UV initiators excited at 980 nm
    Hermes, P. and Hermsen, A. and Jäger, M. and Gutmann, J.S. and Strehmel, V. and Strehmel, B.
    Polymer Chemistry 13 4879-4886 (2022)
    doi: 10.1039/d2py00460g
  • 2022 • 934 Green Textile Materials for Surface Enhanced Raman Spectroscopy Identification of Pesticides Using a Raman Handheld Spectrometer for In-Field Detection
    Hermsen, A. and Schoettl, J. and Hertel, F. and Cerullo, M. and Schlueter, A. and Lehmann, C.W. and Mayer, C. and Jaeger, M.
    Applied Spectroscopy 76 1222-1233 (2022)
    Surface enhanced Raman spectroscopy (SERS) has evolved into a powerful analytical method in food and environmental analytical sciences due to its high sensitivity. Pesticide analysis is a major discipline therein. Using sustainable materials has become increasingly important to adhere to Green Chemistry principles. Hence, the green textiles poly-(L-lactic acid) (PLA) and the mixed fabric polyethylene terephthalate polyamide (PET/PA) were investigated for their applicability as solid supports for gold nanoparticles to yield SERS substrates. Gold nanoparticle solutions and green textile supports were prepared after preparation optimization. Particle size, dispersity, and particle distribution over the textiles were characterized by absorption spectroscopy and transmission electron imaging. The performance of the SERS substrates was tested using the three pesticides imidacloprid, paraquat, and thiram and a handheld Raman spectrometer with a laser wavelength of 785 nm. The resulting SERS spectra possessed an intra-substrate variation of 7–8% in terms of the residual standard deviation. The inter-substrate variations amounted to 15% for PET/PA and to 27% for PLA. Substrate background signals were smaller with PLA but more enhanced through PET/PA. The pesticides could be detected at 1 pg on PET/PA and at 3 ng on PLA. Hence, PET/PA woven textile soaked with gold nanoparticle solution provides green SERS substrates and might prove, in combination with fieldable Raman spectrometers, suitable for in-field analytics for pesticide identification. © The Author(s) 2022.
    view abstractdoi: 10.1177/00037028221097130
  • 2022 • 933 A biophotoelectrode based on boronic acid-modified Chlorella vulgaris cells integrated within a redox polymer
    Herrero-Medina, Z. and Wang, P. and Lielpetere, A. and Bashammakh, A.S. and Alyoubi, A.O. and Katakis, I. and Conzuelo, F. and Schuhmann, W.
    Bioelectrochemistry 146 (2022)
    Green microalgae are gaining attention in the renewable energy field due to their ability to convert light into energy in biophotovoltaic (BPV) cells. The poor exogenous electron transfer kinetics of such microorganisms requires the use of redox mediators to improve the performance of related biodevices. Redox polymers are advantageous in the development of subcellular-based BPV devices by providing an improved electron transfer while simultaneously serving as immobilization matrix. However, these surface-confined redox mediators have been rarely used in microorganism-based BPVs. Since electron transfer relies on the proximity between cells and the redox centres at the polymer matrix, the development of molecularly tailored surfaces is of great significance to fabricate more efficient BPV cells. We propose a bioanode integrating Chlorella vulgaris embedded in an Os complex-modified redox polymer. Chlorella vulgaris cells are functionalized with 3-aminophenylboronic acid that exhibits high affinity to saccharides in the cell wall as a basis for an improved integration with the redox polymer. Maximum photocurrents of (5 ± 1) µA cm−2 are achieved. The developed bioanode is further coupled to a bilirubin oxidase-based biocathode for a proof-of-concept BPV cell. The obtained results encourage the optimization of electron-transfer pathways toward the development of advanced microalgae-based biophotovoltaic devices. © 2022 The Authors
    view abstractdoi: 10.1016/j.bioelechem.2022.108128
  • 2022 • 932 Shock-tube study of the ignition and product formation of fuel-rich CH4/ozone/air and natural gas/ozone/air mixtures at high pressure
    Herzler, J. and Fikri, M. and Schulz, C.
    Applications in Energy and Combustion Science 12 (2022)
    The influence of ozone on the ignition delay times and product formation of methane and natural gas was determined in a high-pressure shock tube at fuel-rich conditions (ϕ = 2 and 10), ozone concentrations of 550 ppm, temperatures between 850 and 1700 K and pressures of about 30 bar. The addition of ozone causes a strong reduction of the ignition delay times for temperatures below 1100 K. Product concentrations were determined with fast sampling and GC/MS analysis for the experiments at ϕ = 10. Experiments and simulations show that CO, H2, H2O, C2H2, C2H4, C2H6, CO2, C3H6, and benzene are the main products. A comparison to similar studies with additives such as n-heptane, dimethyl ether, diethyl ether, dimethoxymethane and experiments without additives shows that C2H2, C2H4, and benzene concentrations are decreased, whereas CO concentrations are increased when ozone is used as additive. The experimental results were compared to simulations with chemical kinetics mechanisms from literature. The measured ignition delay times agree well with the simulations. A comparison of measured and simulated product distributions shows that the temperature dependence of the product formation is predicted well but that there are deviations of the absolute concentrations up to a factor of two for acetylene and benzene contrary to studies with other additives. © 2022
    view abstractdoi: 10.1016/j.jaecs.2022.100082
  • 2022 • 931 Single-pulse shock-tube study on the pyrolysis of small esters (ethyl and propyl propanoate, isopropyl acetate) and methyl isopropyl carbonate
    Herzler, J. and Mujaddadi, S.A. and Fikri, M. and Schulz, C. and Peukert, S.
    Proceedings of the Combustion Institute (2022)
    Single-pulse shock-tube experiments were used to study the thermal decomposition of selected oxygenated hydrocarbons: Ethyl propanoate (C2H5OC(O)C2H5; EP), propyl propanoate (C3H7OC(O)C2H5; PP), isopropyl acetate ((CH3)2HCOC(O)CH3; IPA), and methyl isopropyl carbonate ((CH3)2HCOC(O)OCH3; MIC) The consumption of reactants and the formation of stable products such as C2H4 and C3H6 were measured with gas chromatography/mass spectrometry (GC/MS). Depending on the considered reactant, the temperatures range from 716-1102 K at pressures between 1.5 and 2.0 bar. Rate-coefficient data were obtained from first-order analysis. All reactants primarily decompose by six-center eliminations: EP → C2H4 + C2H5COOH (propionic acid); PP → C3H6 + C2H5COOH; IPA → C3H6 + CH3COOH (acetic acid); MIC → C3H6 + CH3OC(O)OH (methoxy formic acid). Experimental rate-coefficient data can be well represented by the following Arrhenius expressions: k(EP → products) = 1013.49±0.16 exp(-214.95±3.25 kJ/mol/RT) s-1; k(PP → products) = 1012.21±0.16 exp(-191.21±2.79 kJ/mol/RT) s-1; k(IPA → products) = 1013.10±0.31 exp(-186.38±5.10 kJ/mol/RT) s-1; k(MIC → products) = 1012.43±0.29 exp(-165.25±4.46 kJ/mol/RT) s-1. The determination of rate coefficients was based on the amount of C2H4 or C3H6 formed. The potential energy surface (PES) of the thermal decomposition of these four reactants was determined with the G4 composite method. A master-equation analysis was conducted based on energies and molecular properties from the G4 computations. The results indicate that the length of a linear alkyl substituent does not significantly influence the rate of six-center eliminations, whereas the change from a linear to a branched alkyl substituent results in a significant reactivity increase. The comparison between rate-coefficient data also shows that alkyl carbonates have higher reactivity towards decomposition by six-center elimination than esters. The results are discussed in in the context of reactivity patterns of carbonyl compounds. © 2022 Elsevier Inc. All rights reserved.
    view abstractdoi: 10.1016/j.proci.2022.07.012
  • 2022 • 930 Rate-Independent Systems and Their Viscous Regularizations: Analysis, Simulation, and Optimal Control
    Herzog, R. and Knees, D. and Meyer, C. and Sievers, M. and Stötzner, A. and Thomas, S.
    International Series of Numerical Mathematics 172 121-144 (2022)
    This chapter provides a survey on the analysis, simulation, and optimal control of a class of non-smooth evolution systems that appears in the modeling of dissipative solids. Our focus is on models that include internal constraints, such as a flow rule in plasticity, and that account for the temperature dependence of the respective materials. We discuss here two cases, namely purely rate-independent models and viscously regularized models coupled to the temperature equation. © 2022, Springer Nature Switzerland AG.
    view abstractdoi: 10.1007/978-3-030-79393-7_6
  • 2022 • 929 Mono-ADP-ribosylation sites of human CD73 inhibit its adenosine-generating enzymatic activity
    Hesse, J. and Rosse, M.K. and Steckel, B. and Blank-Landeshammer, B. and Idel, S. and Reinders, Y. and Sickmann, A. and Sträter, N. and Schrader, J.
    Purinergic Signalling 18 115-121 (2022)
    CD73-derived adenosine plays a major role in damage-induced tissue responses by inhibiting inflammation. Damage-associated stimuli, such as hypoxia and mechanical stress, induce the cellular release of ATP and NAD+ and upregulate the expression of the nucleotide-degrading purinergic ectoenzyme cascade, including adenosine-generating CD73. Extracellular NAD+ also serves as substrate for mono-ADP-ribosylation of cell surface proteins, which in human cells is mediated by ecto-ADP-ribosyltransferase 1 (ARTC1). Here we explored, whether human CD73 enzymatic activity is regulated by mono-ADP-ribosylation, using recombinant human CD73 in the presence of ARTC1 with etheno-labelled NAD+ as substrate. Multi-colour immunoblotting with an anti-etheno-adenosine antibody showed ARTC1-mediated transfer of ADP-ribose together with the etheno label to CD73. HPLC analysis of the enzymatic activity of in vitro-ribosylated CD73 revealed strong inhibition of adenosine generation in comparison to non-ribosylated CD73. Mass spectrometry of in vitro-ribosylated CD73 identified six ribosylation sites. 3D model analysis indicated that three of them (R328, R354, R545) can interfere with CD73 enzymatic activity. Our study identifies human CD73 as target for ARTC1-mediated mono-ADP-ribosylation, which can profoundly modulate its adenosine-generating activity. Thus, in settings with enhanced release of NAD+ as substrate for ARTC1, assessment of CD73 protein expression in human tissues may not be predictive of adenosine formation resulting in anti-inflammatory activity. © 2021, The Author(s).
    view abstractdoi: 10.1007/s11302-021-09832-4
  • 2022 • 928 Mixing and segregation of spheres of three different sizes on a batch stoker grate: Experiments and discrete element simulation
    Hilse, N. and Kriegeskorte, M. and Illana, E. and Wirtz, S. and Scherer, V.
    Powder Technology 400 (2022)
    Mixing and segregation in a tri-disperse granular assembly of polyoxymethylene (POM) spheres induced by the moveable stoking bars of a generic batch grate system are examined. Each particle size class features a separate colour. Stroke bar velocity and stroke length are varied. Different moving modes of the bars are analysed. Optically transparent walls of the grate allow for the localization of the visible particles. Based on the visible particle positions a segregation index is calculated. The initial arrangement of the particles in the experiments, which exhibits small statistical differences introduced by the grate filling procedure, has an influence on the progression of the segregation index. The experiments are compared with discrete element (DEM) simulations employing an in-house DEM code. Experiments are in good general agreement with the simulations. The particle rearrangement during bar movement is characterized by an initially fast mixing on short time-scales and a slow process to reach a final state of segregation. These two processes are influenced by the penetration depth of the bars into the bed and the specific movement mode. Three modes predominantly showed segregation in the direction of bar movement, whereas two modes showed large-scale spatial particle rearrangement. Two moving modes show bridging at the beginning of the experiments, an effect that could be reproduced by the DEM simulations. The influence of the modes and their specific parameters on segregation indices, a mixing rate and a segregation efficiency are discussed in detail. © 2022 Elsevier B.V.
    view abstractdoi: 10.1016/j.powtec.2022.117258
  • 2022 • 927 Deuteron magnetic resonance study of glyceline deep eutectic solvents: Selective detection of choline and glycerol dynamics
    Hinz, Y. and Böhmer, R.
    Journal of Chemical Physics 156 (2022)
    doi: 10.1063/5.0088290
  • 2022 • 926 Recognition of a Flexible Protein Loop in Taspase 1 by Multivalent Supramolecular Tweezers
    Höing, A. and Kirupakaran, A. and Beuck, C. and Pörschke, M. and Niemeyer, F.C. and Seiler, T. and Hartmann, L. and Bayer, P. and Schrader, T. and Knauer, S.K.
    Biomacromolecules (2022)
    Many natural proteins contain flexible loops utilizing well-defined complementary surface regions of their interacting partners and usually undergo major structural rearrangements to allow perfect binding. The molecular recognition of such flexible structures is still highly challenging due to the inherent conformational dynamics. Notably, protein-protein interactions are on the other hand characterized by a multivalent display of complementary binding partners to enhance molecular affinity and specificity. Imitating this natural concept, we here report the rational design of advanced multivalent supramolecular tweezers that allow addressing two lysine and arginine clusters on a flexible protein surface loop. The protease Taspase 1, which is involved in cancer development, carries a basic bipartite nuclear localization signal (NLS) and thus interacts with Importin α, a prerequisite for proteolytic activation. Newly established synthesis routes enabled us to covalently fuse several tweezer molecules into multivalent NLS ligands. The resulting bi- up to pentavalent constructs were then systematically compared in comprehensive biochemical assays. In this series, the stepwise increase in valency was robustly reflected by the ligands' gradually enhanced potency to disrupt the interaction of Taspase 1 with Importin α, correlated with both higher binding affinity and inhibition of proteolytic activity. © 2022 The Authors. Published by American Chemical Society.
    view abstractdoi: 10.1021/acs.biomac.2c00652
  • 2022 • 925 Dual activity inhibition of threonine aspartase 1 by a single bisphosphate ligand
    Höing, A. and Struth, R. and Beuck, C. and Rafieiolhosseini, N. and Hoffmann, D. and Stauber, R.H. and Bayer, P. and Niemeyer, J. and Knauer, S.K.
    RSC Advances 12 34176-34184 (2022)
    doi: 10.1039/d2ra06019a
  • 2022 • 924 Nitrous acid in high-pressure oxidation of CH4 doped with nitric oxide: Challenges in the isomer-selective detection and quantification of an elusive intermediate
    Hoener, M. and Kasper, T.
    Combustion and Flame 243 (2022)
    The nitrous acid combustion intermediate has recently been detected in several reaction conditions using hydrocarbon fuels with different analytical techniques. Three of the several isomers of nitrous acid are expected to be produced during combustion: trans-HONO, cis-HONO and HNO2. It has recently been shown that cis-HONO dissociates upon ionization, rendering isomer selective quantification with methods requiring photoionization prior to detection impossible. This fact is of importance, since cis-HONO is produced at a ten times higher rate than trans-HONO according to recently published isomer branching ratios, possibly leading to sensitivity issues when a detection of the isomer mix is attempted with photoionization methods. We provide a quantitative glimpse at the trans-HONO isomer in a systematic set of measurements of NO doped methane oxidized in a plug-flow reactor covering three reaction conditions in the lean and rich regimes. Reactions take place at equivalence ratios of 0.7 and 1.2 with 1000 ppm NO and at an equivalence ratio of 2.1 doped with 1% NO. Double imaging photoelectron photo ion coincidence spectroscopy, i2PEPICO, was used to selectively and assuredly detect and assign trans-HONO. We touch on the difficulties encountered when attempting to detect cis-HONO. HNO2 remained undetectable despite recently published reaction rates for HNO2 decomposition suggesting modelled concentrations of this species two orders of magnitude larger than previously believed, yet 10 times lower than the reported isomer branching ratio. The recent reaction rates add a new path for HNO2 decomposition leading to formation of OH and NO which in turn influences the remaining decomposition kinetics of HNO2. A literature model is modified to include the recently published reaction rates for HONO and HNO2 decomposition and isomerization and compared to the measurements. Despite the higher predicted concentration of HNO2, that should be sufficient for detection, no HNO2 is detected in the experiment. Other nitrogen containing species, such as nitromethane and NO2, the precursor of both HONO and nitromethane, have also been detected. Interestingly, ammonia was also present in significant concentration, albeit exclusively in the fuel-rich conditions, despite the relatively low maximum temperature of 923 K at which the experiments have been performed. We conclude that, facing the unfavorable photoionization properties of cis-HONO as well as the decomposition and formation kinetics of HNO2, a measurement of isomer branching fractions by means of selective and sensitive photoionization methods may remain unattainable. © 2022 The Combustion Institute
    view abstractdoi: 10.1016/j.combustflame.2022.112096
  • 2022 • 923 Simulation, analysis and control of a self-propelling heat removal system using supercritical CO2 under varying boundary conditions
    Hofer, M. and Ren, H. and Hecker, F. and Buck, M. and Brillert, D. and Starflinger, J.
    Energy 247 (2022)
    The supercritical carbon dioxide (sCO21) heat removal system, which is based on a closed Brayton cycle with sCO2 as a working fluid, is an innovative heat removal system for existing and future nuclear power plants. This paper provides the design, layout and control of the system based on assumptions developed in the project sCO2-4-NPP. A self-propelling operational readiness state enables a fast start-up and consumes only 12% of the design thermal power input. The system is analysed over a wide range of ambient and steam-side conditions in ATHLET, using performance maps for the turbomachinery, which were designed recently. The performance analysis suggests that it is a good option to operate the system at the design compressor inlet temperature of 55 °C at any boundary condition. With decreasing thermal power input, the rotational speed of the turbomachinery must be decreased to keep the system self-propelling. Moreover, the turbomachinery design with a higher surge margin is preferred. By controlling the compressor inlet temperature via the air mass flow rate and turbine inlet temperature via the turbomachinery speed, the heat removal system is successfully operated in interaction with a pressurized water reactor. © 2022 The Authors
    view abstractdoi: 10.1016/j.energy.2022.123500
  • 2022 • 922 Oxygen NMR of high-density and low-density amorphous ice
    Hoffmann, L. and Beerwerth, J. and Adjei-Körner, M. and Fuentes-Landete, V. and Tonauer, C.M. and Loerting, T. and Böhmer, R.
    Journal of Chemical Physics 156 (2022)
    doi: 10.1063/5.0080333
  • 2022 • 921 THz metrology with monolithic tunable two-color diode lasers
    Hofmann, M.R. and Surkamp, N. and Gerling, A. and O’Gorman, J. and Honsberg, M. and Schmidtmann, S. and Nandi, U. and Preu, S. and Sacher, J. and Brenner, C.
    Proceedings of SPIE - The International Society for Optical Engineering 12134 (2022)
    doi: 10.1117/12.2626219
  • 2022 • 920 Mesoporous boron nitride in contact with water - Chemical stability and adsorption properties
    Hojak, J. and Jähnichen, T. and Bläker, C. and Pasel, C. and Mauer, V. and Rasmussen, L. and Denecke, R. and Enke, D. and Bathen, D.
    Results in Materials 16 (2022)
    doi: 10.1016/j.rinma.2022.100338
  • 2022 • 919 Adsorption of Inhalation Anesthetics on Activated Carbon in Humid Atmosphere
    Hojak, J. and Bläker, C. and Pasel, C. and Bathen, D.
    Journal of Chemical and Engineering Data 67 2845-2854 (2022)
    doi: 10.1021/acs.jced.2c00132
  • 2022 • 918 Laser pre-structure-assisted micro-milling of Ti6Al4V titanium alloy
    Hojati, F. and Azarhoushang, B. and Daneshi, A. and Biermann, D.
    International Journal of Advanced Manufacturing Technology (2022)
    High flexibility of the micro-milling process compared to nontraditional methods has led to its growing application in manufacturing complex micro-parts with tight tolerances and high accuracies. However, difficulties such as tool deflection, size effect, and tool wear limit the application of micro-milling. In this regard, the role of laser-assisted machining (LAM) is highlighted to prevent mentioned issues through reduction of machining forces and providing the possibility for using higher feeds. Ti6Al4V as a hard-to-machine material is chosen as the workpiece material. Unlike traditional LAM, Ti6Al4V parts were structured using a picosecond laser before micro-milling. The influence of laser structuring at different structure densities on the reduction of machining forces was analyzed at two feeds of 10 and 50 µm/tooth at a constant cutting speed of 35 m/min. A remarkable reduction in cutting forces was observed at both feeds. Additionally, the role of structure density in cutting force reduction is highlighted. © 2022, The Author(s).
    view abstractdoi: 10.1007/s00170-022-08774-4
  • 2022 • 917 Recent developments in the functional renormalization group approach to correlated electron systems
    Honerkamp, C. and Kennes, D.M. and Meden, V. and Scherer, M.M. and Thomale, R.
    European Physical Journal B 95 (2022)
    doi: 10.1140/epjb/s10051-022-00463-1
  • 2022 • 916 Hidden parameters for electrochemical carbon dioxide reduction in zero-gap electrolyzers
    Hoof, L. and Thissen, N. and Pellumbi, K. and junge Puring, K. and Siegmund, D. and Mechler, A.K. and Apfel, U.-P.
    Cell Reports Physical Science 3 (2022)
    doi: 10.1016/j.xcrp.2022.100825
  • 2022 • 915 Influence of surface activation on the microporosity of PE-CVD and PE-ALD SiOx thin films on PDMS
    Hoppe, C. and Mitschker, F. and Mai, L. and Liedke, M.O. and de los Arcos, T. and Awakowicz, P. and Devi, A. and Attallah, A.G. and Butterling, M. and Wagner, A. and Grundmeier, G.
    Plasma Processes and Polymers (2022)
    The microporosity, structure and permeability of SiOx thin films deposited by microwave plasma-enhanced chemical vapour deposition (PE-CVD) and plasma-enhanced atomic layer deposition (PE-ALD) on polydimethylsiloxane (PDMS) substrates were investigated by positron annihilation spectroscopy and complementary technique, such as X-ray photoelectron spectroscopy, infrared spectroscopy, time of flight mass spectroscopy and atomic force microscopy. The SiOx films were deposited onto spin-coated PDMS substrates, which were previously exposed to an oxygen plasma thus achieving the conversion of the top polymer layer into SiOx. The presence of this oxidised surface near the region led to an overall decrease in micropore density and to a shift towards smaller pore sizes within the deposited SiOx films. A correlation between the oxygen fluence during the oxygen plasma treatment and the microporosity of the PE-CVD and PE-ALD SiOx films could be established. © 2022 The Authors. Plasma Processes and Polymers published by Wiley-VCH GmbH.
    view abstractdoi: 10.1002/ppap.202100174
  • 2022 • 914 Experimental analysis of particle deposition in fibrous depth filters during gas cleaning using X-ray microscopy
    Hoppe, K. and Schaldach, G. and Zielke, R. and Tillmann, W. and Thommes, M. and Pieloth, D.
    Aerosol Science and Technology 56 1114-1131 (2022)
    Microscopic data on airborne particle separation in depth filters are a key for understanding and predictive modeling of the evolution of filtration properties such as pressure drop and efficiency during the filtration process. Tomographic imaging techniques (e.g., MRI, CT) are excellent methods for 3D-resolved analysis of microscopic loading behavior, but these are often limited in terms of spatial resolution and because of the low contrast between filter material and particles. In this study, an X-ray microscope was used to analyze the separation of iodine-containing particles (d50,3 =1.5 µm) in a coarse dust filter (porosity: 0.98; fiber diameter: 24 µm). The use of iodine-containing particles produced sufficient contrast for segmentation and analysis of the particle deposits produced during filtration. The established method allowed the analysis of the deposits within the material in terms of mass, size distribution, and the shape of the formed deposits in time and space. The data presented in this work provide new insights and methods for an improved understanding of the dynamic behavior of filter materials. © 2022 The Author(s). Published with license by Taylor and Francis Group, LLC.
    view abstractdoi: 10.1080/02786826.2022.2132133
  • 2022 • 913 Sign depth tests in multiple regression
    Horn, M. and Müller, C.H.
    Journal of Statistical Computation and Simulation (2022)
    The recently proposed simple but powerful sign depth tests depend on the order of the residuals. While one-dimensional explanatory variables provide a natural order, there exists no canonical order for multidimensional explanatory variables. For this scenario, we present different approaches for ordering multidimensional explanatory variables and compare them regarding their performance with respect to the stability of the ordering, the usability for non-metric explanatory variables, the computational time complexity, and in the context of testing in linear models including high-dimensional multiple regression. It is shown that the sign depth tests based on orderings given by pairwise distances perform best. They are much more powerful than the classical sign test and also than the F-test when not having normally distributed errors. They are competitive to the much more complicated robust Wald test based on efficient MM-estimation. Additionally, the sign depth tests are more appropriate for outlier robust model checks. © 2022 Informa UK Limited, trading as Taylor & Francis Group.
    view abstractdoi: 10.1080/00949655.2022.2130922
  • 2022 • 912 Design and validation of a low-cost open-source impedance based quartz crystal microbalance for electrochemical research
    Horst, R.J. and Katzourakis, A. and Mei, B.T. and de Beer, S.
    HardwareX 12 (2022)
    The quartz crystal microbalance (QCM) measurement technique is utilized in a broad variety of scientific fields and applications, where surface and interfacial processes are relevant. However, the costs of purchasing QCMs is typically high, which has limited its employment in education as well as by scientists in developing countries. In this article, we present an open-source QCM, built on the OpenQCM project, and using an impedance-based measurement technique (QCM-I), which can be built for <200 euro. Our QCM allows for simultaneous monitoring of the frequency change and dissipation, such that both soft and rigid materials can be characterized. In addition, our QCM measurements can be combined with simultaneous electrochemical measurement techniques (EQCM-I). We demonstrate the validity of our system by characterizing the electrodeposition of a rigid metallic film (Cu) and by the electropolymerization of aniline. Finally, we discuss potential improvements to our system. © 2022 The Author(s)
    view abstractdoi: 10.1016/j.ohx.2022.e00374
  • 2022 • 911 Size scaling in bi-crystalline Cu micropillars containing a coherent twin boundary
    Hosseinabadi, R. and Riesch-Oppermann, H. and Best, J.P. and Dehm, G. and Kirchlechner, C.
    Acta Materialia 230 (2022)
    doi: 10.1016/j.actamat.2022.117841
  • 2022 • 910 Reactivity of NK Cells Against Ovarian Cancer Cells Is Maintained in the Presence of Calcium Phosphate Nanoparticles
    Hrvat, A. and Schmidt, M. and Obholzer, M. and Benders, S. and Kollenda, S. and Horn, P.A. and Epple, M. and Brandau, S. and Mallmann-Gottschalk, N.
    Frontiers in Immunology 13 (2022)
    Calcium phosphate nanoparticles (CaP-NPs) are biodegradable carriers that can be functionalized with biologically active molecules. As such, they are potential candidates for delivery of therapeutic molecules in cancer therapies. In this context, it is important to explore whether CaP-NPs impair the natural or therapy-induced immune cell activity against cancer cells. Therefore, in this study, we have investigated the effects of different CaP-NPs on the anti-tumor activity of natural killer (NK) cells using different ovarian cancer (OC) cell line models. We explored these interactions in coculture systems consisting of NK cells, OC cells, CaP-NPs, and therapeutic Cetuximab antibodies (anti-EGFR, ADCC-inducing antibody). Our experiments revealed that aggregated CaP-NPs can serve as artificial targets, which activate NK cell degranulation and impair ADCC directed against tumor targets. However, when CaP-NPs were properly dissolved by sonication, they did not cause substantial activation. CaP-NPs with SiO2-SH-shell induced some activation of NK cells that was not observed with polyethyleneimine-coated CaP-NPs. Addition of CaP-NPs to NK killing assays did not impair conjugation of NK with OC and subsequent tumor cytolytic NK degranulation. Therapeutic antibody coupled to functionalized CaP-NPs maintained substantial levels of antibody-dependent cellular cytotoxic activity. Our study provides a cell biological basis for the application of functionalized CaP-NPs in immunologic anti-cancer therapies. Copyright © 2022 Hrvat, Schmidt, Obholzer, Benders, Kollenda, Horn, Epple, Brandau and Mallmann-Gottschalk.
    view abstractdoi: 10.3389/fimmu.2022.830938
  • 2022 • 909 Laser performance of LD side-pumped Er:YSGG crystal rods with different diameters
    Hu, L. and Sun, D. and Hou, Y. and Gurevich, E.L. and Ostendorf, A. and Guo, Q.
    Proceedings of SPIE - The International Society for Optical Engineering 12310 (2022)
    doi: 10.1117/12.2641626
  • 2022 • 908 Highly dispersed Pd clusters/nanoparticles encapsulated in MOFs via in situ auto-reduction method for aqueous phenol hydrogenation
    Huang, X. and Li, X. and Xia, W. and Hu, B. and Muhler, M. and Peng, B.
    Journal of Materials Science and Technology 109 167-175 (2022)
    In this work, a novel in situ auto-reduction strategy was developed to encapsulate uniformly dispersed Pd clusters/nanoparticles in MIL-125-NH2. It is demonstrated that the amino groups in MIL-125-NH2 can react with formaldehyde to form novel reducing groups (-NH[sbnd]CH2OH), which can in situ auto-reduce the encapsulated Pd2+ ions to metallic Pd clusters/nanoparticles. As no additional reductants are required, the strategy limits the aggregation and migration of Pd clusters and the formation of large Pd nanoparticles via controlling the amount of Pd2+ precursor. When applied as catalysts in the hydrogenation of phenol in the aqueous phase, the obtained Pd(1.5)/MIL-125-NH-CH2OH catalyst with highly dispersed Pd clusters/nanoparticles with the size of around 2 nm exhibited 100% of phenol conversion and 100% of cyclohexanone selectivity at 70 °C after 5 h, as well as remarkable reusability for at least five cycles due to the large MOF surface area, the highly dispersed Pd clusters/nanoparticles and their excellent stability within the MIL-125-NH-CH2OH framework. © 2021
    view abstractdoi: 10.1016/j.jmst.2021.08.079
  • 2022 • 907 B-Spline-Based Corner Smoothing Method to Decrease the Maximum Curvature of the Transition Curve
    Huang, N. and Hua, L. and Huang, X. and Zhang, Y. and Zhu, L. and Biermann, D.
    Journal of Manufacturing Science and Engineering, Transactions of the ASME 144 (2022)
    doi: 10.1115/1.4052708
  • 2022 • 906 Self-Assembled Artificial DNA Nanocompartments and Their Bioapplications
    Huang, J. and Gambietz, S. and Saccà, B.
    Small (2022)
    Compartmentalization is the strategy evolved by nature to control reactions in space and time. The ability to emulate this strategy through synthetic compartmentalization systems has rapidly evolved in the past years, accompanied by an increasing understanding of the effects of spatial confinement on the thermodynamic and kinetic properties of the guest molecules. DNA nanotechnology has played a pivotal role in this scientific endeavor and is still one of the most promising approaches for the construction of nanocompartments with programmable structural features and nanometer-scaled addressability. In this review, the design approaches, bioapplications, and theoretical frameworks of self-assembled DNA nanocompartments are surveyed. From DNA polyhedral cages to virus-like capsules, the construction principles of such intriguing architectures are illustrated. Various applications of DNA nanocompartments, including their use for programmable enzyme scaffolding, single-molecule studies, biosensing, and as artificial nanofactories, ending with an ample description of DNA nanocages for biomedical purposes, are then reported. Finally, the theoretical hypotheses that make DNA nanocompartments, and nanosystems in general, a topic of great interest in modern science, are described and the progresses that have been done until now in the comprehension of the peculiar phenomena that occur within nanosized environments are summarized. © 2022 The Authors. Small published by Wiley-VCH GmbH.
    view abstractdoi: 10.1002/smll.202202253
  • 2022 • 905 Roles of Focal Adhesion Kinase PTK2 and Integrin αIIbβ3 Signaling in Collagen- and GPVI-Dependent Thrombus Formation under Shear
    Huang, J. and Jooss, N.J. and Fernández, D.I. and Sickmann, A. and García, Á. and Wichapong, K. and Dijkgraaf, I. and Heemskerk, J.W.M.
    International Journal of Molecular Sciences 23 (2022)
    Glycoprotein (GP)VI and integrin αIIbβ3 are key signaling receptors in collagen-dependent platelet aggregation and in arterial thrombus formation under shear. The multiple downstream signaling pathways are still poorly understood. Here, we focused on disclosing the integrin-dependent roles of focal adhesion kinase (protein tyrosine kinase 2, PTK2), the shear-dependent collagen receptor GPR56 (ADGRG1 gene), and calcium and integrin-binding protein 1 (CIB1). We designed and synthetized peptides that interfered with integrin αIIb binding (pCIB and pCIBm) or mimicked the activation of GPR56 (pGRP). The results show that the combination of pGRP with PTK2 inhibition or of pGRP with pCIB &gt; pCIBm in additive ways suppressed collagen- and GPVI-dependent platelet activation, thrombus buildup, and contraction. Microscopic thrombus formation was assessed by eight parameters (with script descriptions enclosed). The suppressive rather than activating effects of pGRP were confined to blood flow at a high shear rate. Blockage of PTK2 or interference of CIB1 no more than slightly affected thrombus formation at a low shear rate. Peptides did not influence GPVI-induced aggregation and Ca2+ signaling in the absence of shear. Together, these data reveal a shear-dependent signaling axis of PTK2, integrin αIIbβ3, and CIB1 in collagen- and GPVI-dependent thrombus formation, which is modulated by GPR56 and exclusively at high shear. This work thereby supports the role of PTK2 in integrin αIIbβ3 activation and signaling. © 2022 by the authors.
    view abstractdoi: 10.3390/ijms23158688
  • 2022 • 904 The effects of the driving frequencies on micro atmospheric pressure He/N2plasma jets driven by tailored voltage waveforms
    Hübner, G. and Bischoff, L. and Korolov, I. and Donkó, Z. and Leimkühler, M. and Liu, Y. and Böke, M. and Schulz-Von Der Gathen, V. and Mussenbrock, T. and Schulze, J.
    Journal of Physics D: Applied Physics 55 (2022)
    Capacitively coupled micro atmospheric pressure plasma jets are important tools for the generation of radicals at room temperature for various applications. Voltage waveform tailoring (VWT), which is based on the simultaneous use of a set of excitation frequencies, has been demonstrated to provide an efficient control of the electron energy probability function (EEPF) in such plasmas and, thus, allows optimizing the electron impact driven excitation and dissociation processes as compared to the classical single-frequency operation mode. In this work, the effects of changing the driving frequencies on the spatio-temporally resolved electron power absorption dynamics, the generation of helium metastables and the dissociation of nitrogen molecules are investigated in He/N2 plasmas based on experiments and simulations. We find that under a single-frequency excitation, the plasma and helium metastable densities are enhanced as a function of the driving frequency at a fixed voltage. When using valleys-type driving voltage waveforms synthesized based on consecutive harmonics of the fundamental driving frequency, the spatial symmetry of the electron power absorption dynamics and of the metastable density profile is broken. Increasing the fundamental frequency at a constant voltage is found to drastically enhance the plasma and metastable densities, which is a consequence of the change of the EEPF. Finally, we compare the energy efficiency of the formation of radicals under single-frequency and VWT operation at different driving frequencies. For a given power dissipated in the plasma, VWT yields a higher helium metastable as well as electron density and a higher dissociation rate of N2. © 2021 IOP Publishing Ltd.
    view abstractdoi: 10.1088/1361-6463/ac3791
  • 2022 • 903 One-Dimensional Water Structures upon Cs Hydration on the Moiré Pattern of Graphitic ZnO
    Hung, T.-C. and Morgenstern, K.
    Journal of Physical Chemistry C 126 15229-15234 (2022)
    Water nucleation on alkali precovered metal-supported oxide surfaces is an important step in understanding water as one of the reactants in alkali-assisted heterogeneous catalysis. For instance, alkali metals as catalyst dopants enhance the water-gas shift reaction that catalyzes on ZnO-metal nanostructures. Here, we investigate the hydration of cesium on a Ag(111)-supported graphitic zinc oxide ultrathin film using scanning tunneling microscopy at (160 ± 30) K. Upon hydrating the pristine graphitic ZnO film, the water forms well-separated clusters on the hcp regions of the ZnO moiré pattern at water coverages below 85% ML. In the presence of cesium on the fcc regions of the ZnO moiré pattern, the water clusters coalesce across hcp regions at water coverages above ∼32% ML, forming unique one-dimensional water-Cs chains along the high-symmetry directions of the ZnO moiré pattern. Our study demonstrates that the alkali doping of an oxide surface alters the dimensionality of water structures redirecting it partially to other adsorption regions, possibly influencing its reactivity. © 2022 American Chemical Society.
    view abstractdoi: 10.1021/acs.jpcc.2c05166
  • 2022 • 902 Influence of the Moiré Pattern of Ag(111)-Supported Graphitic ZnO on Water Distribution
    Hung, T.-C. and Le, D. and Rahman, T. and Morgenstern, K.
    Journal of Physical Chemistry C 126 12500-12506 (2022)
    The distribution of water on metal supported oxides is an important step in understanding heterogeneous catalysis such as in the water gas shift reaction. Here, we study water structures on Ag(111)-supported graphitic zinc oxide islands by variable temperature scanning tunneling microscopy around 150 K and ab initio calculations. Water clusters, accumulating on the ZnO islands, are confined to the hcp regions of the ZnO moiré pattern. A significantly higher cluster density at the island border is related to the dimensions of its capture zone. This suggests an upward mass transport of the water from the supporting metal to the ultrathin oxide film, increasing the water density at the active metal-oxide border. © 2022 American Chemical Society. All rights reserved.
    view abstractdoi: 10.1021/acs.jpcc.2c03274
  • 2022 • 901 Influence of the PTFE Membrane Thickness on the CO2 Electroreduction Performance of Sputtered Cu-PTFE Gas Diffusion Electrodes
    Huq, F. and Sanjuán, I. and Baha, S. and Braun, M. and Kostka, A. and Chanda, V. and Junqueira, J.R.C. and Sikdar, N. and Ludwig, A. and Andronescu, C.
    ChemElectroChem 9 (2022)
    Gas diffusion electrodes (GDE) obtained by sputtering metal films on polytetrafluoroethylene (PTFE) membranes are among the most performant electrodes used to electrochemically reduce CO2. The present work reveals several essential aspects for fabricating performant PTFE-based gas diffusion electrodes (GDEs) for CO2 electroreduction (CO2R). We show that adding an additive layer (a mixture of carbon and Nafion™ or Nafion™ only) is required for stabilizing the metal catalyst film (Cu), deposited via sputtering on the PTFE membrane, during the CO2R experiments. We found that the PTFE membrane thickness used in the GDE fabrication plays an essential role in electrode performance. The quantification of the products formed during the CO2R conducted in a flow-cell electrolyzer revealed that on thinner membranes, CO2R is the dominant process while on thicker ones, the H2 formation is promoted. Thus, the PTFE membrane influences the CO2 transport to the catalyst layer and can be used to promote the CO2R while maintaining a minimum H2 production. © 2021 The Authors. ChemElectroChem published by Wiley-VCH GmbH
    view abstractdoi: 10.1002/celc.202101279
  • 2022 • 900 Comparison of the nucleation and growth of a phosphate conversion coating on Zn[sbnd]Al and Zn[sbnd]Al[sbnd]Mg coatings under the influence of a corrosion inhibitor film
    Husien Said, V. and Haakmann, F. and Brinkbäumer, J. and Ulbricht, M.
    Surface and Coatings Technology 451 (2022)
    doi: 10.1016/j.surfcoat.2022.129044
  • 2022 • 899 SnO deposition via water based ALD employing tin(ii) formamidinate: precursor characterization and process development
    Huster, N. and Ghiyasi, R. and Zanders, D. and Rogalla, D. and Karppinen, M. and Devi, A.
    Dalton Transactions 51 14970-14979 (2022)
    doi: 10.1039/d2dt02562k
  • 2022 • 898 Multilevel Picard approximations for McKean-Vlasov stochastic differential equations
    Hutzenthaler, M. and Kruse, T. and Nguyen, T.A.
    Journal of Mathematical Analysis and Applications 507 (2022)
    In the literature there exist approximation methods for McKean-Vlasov stochastic differential equations which have a computational effort of order 3. In this article we introduce full-history recursive multilevel Picard approximations for McKean-Vlasov stochastic differential equations. We prove that these MLP approximations have computational effort of order 2+ which is essentially optimal in high dimensions. © 2021 Elsevier Inc.
    view abstractdoi: 10.1016/j.jmaa.2021.125761
  • 2022 • 897 Multilevel Picard approximations of high-dimensional semilinear partial differential equations with locally monotone coefficient functions
    Hutzenthaler, M. and Nguyen, T.A.
    Applied Numerical Mathematics 181 151-175 (2022)
    doi: 10.1016/j.apnum.2022.05.009
  • 2022 • 896 Strong convergence rate of Euler-Maruyama approximations in temporal-spatial Hölder-norms
    Hutzenthaler, M. and Nguyen, T.A.
    Journal of Computational and Applied Mathematics 413 (2022)
    doi: 10.1016/j.cam.2022.114391
  • 2022 • 895 On the speed of convergence of Picard iterations of backward stochastic differential equations
    Hutzenthaler, M. and Kruse, T. and Nguyen, T.A.
    Probability, Uncertainty and Quantitative Risk 7 133-150 (2022)
    doi: 10.3934/puqr.2022009
  • 2022 • 894 Overcoming the curse of dimensionality in the numerical approximation of backward stochastic differential equations
    Hutzenthaler, M. and Jentzen, A. and Kruse, T. and Anh Nguyen, T.
    Journal of Numerical Mathematics (2022)
    doi: 10.1515/jnma-2021-0111
  • 2022 • 893 Costly defense traits in structured populations
    Hutzenthaler, M. and Jordan, F. and Metzler, D.
    Alea (Rio de Janeiro) 19 1697-1752 (2022)
    doi: 10.30757/ALEA.V19-65
  • 2022 • 892 Predicting Solvent Effects on Homogeneity and Kinetics of the Hydroaminomethylation: A Thermodynamic Approach Using PC-SAFT
    Huxoll, F. and Kampwerth, A. and Seidensticker, T. and Vogt, D. and Sadowski, G.
    Industrial and Engineering Chemistry Research 61 2323-2332 (2022)
    Solvents may significantly affect the phase behavior and kinetics of chemical reactions. Especially for complex reactions performed in mixtures of different solvents, it requires a high experimental effort to quantify these effects. This work focuses on a novel thermodynamic approach to predict solvent effects on both reaction rates and phase behavior. We applied this method to the homogeneously catalyzed hydroaminomethylation of 1-decene in a thermomorphic multiphase system of methanol and n-dodecane. For that purpose, the thermodynamic activities of the reactants and the liquid-liquid equilibrium of the multicomponent reaction system were successfully modeled using the Perturbed-Chain Statistical Associating Fluid Theory (PC-SAFT). An increasing concentration of n-dodecane in the solvent mixture was predicted not only to limit the working space for the reaction due to unwanted phase separation but also to massively reduce the reaction rate. These results were in good agreement with batch experiments and homogeneity tests performed in this work. The approach is applicable to a wide variety of liquid-phase reactions and thus is a valuable tool for reducing the experimental effort to a minimum. © 2022 The Authors. Published by American Chemical Society
    view abstractdoi: 10.1021/acs.iecr.1c03891
  • 2022 • 891 A guide to direct mechanocatalysis
    Hwang, S. and Grätz, S. and Borchardt, L.
    Chemical Communications 58 1661-1671 (2022)
    Direct mechanocatalysis (DM) describes solvent-free catalytic reactions that are initiated by mechanical forces in mechanochemical reactors such as ball mills. The distinctive feature of DM is that the milling materials, e.g. the milling balls themselves are the catalyst of the reaction. In this article we follow the historical evolution of this novel concept and give a guide to this emerging, powerful synthesis tool. Within this perspective we seek to highlight the impact of the relevant milling parameters, the nature of the catalyst and potential additives, the scope of reactions that are currently accessible by this method, and the thus far raised hypotheses on the underlying mechanisms of direct mechanochemical transformations. © The Royal Society of Chemistry.
    view abstractdoi: 10.1039/d1cc05697b
  • 2022 • 890 Hybrid Mixed Finite Element Formulations Based on a Least-Squares Approach
    Igelbüscher, M. and Schröder, J.
    Lecture Notes in Applied and Computational Mechanics 98 169-189 (2022)
    In this contribution we focus on the relaxation of continuity conditions and the enforcement of these continuity constraints for the considered fields via Lagrange multipliers. Therefore, a stress-displacement least-squares formulation F(σ, u) is considered, which is defined by the squared L2(B) -norm applied to the first-order system of differential equations, given by the balance of momentum and the constitutive equation as well as an additional (mathematically redundant) residual for the enforcement of the moment of momentum. In general the continuity conditions are enforced by the conforming discretization of the individual fields. The conforming discretization, which demands continuity of the displacements and normal continuity of the stresses, is given by polynomial functions of Lagrange type for the displacements, i.e. uh∈ H1(B), and a stress approximation e.g. with Raviart–Thomas functions, i.e. σh∈ H(div, B). A non-conforming discretization of the stresses and displacements considering discontinuous Raviart–Thomas and discontinuous Lagrange approximation functions with σh∈ d RTm and uh∈ d Pk yield a relaxation of the continuity conditions. However the fulfillment of these relaxed constraints is enforced by the introduction of Lagrange multipliers. Additionally, a continuous as well as a discontinuous stress approximation with σh∈ H1(B) and σh∈ L2(B) is considered. © 2022, The Author(s), under exclusive license to Springer Nature Switzerland AG.
    view abstractdoi: 10.1007/978-3-030-92672-4_7
  • 2022 • 889 Least-Squares Finite Element Formulation for Finite Strain Elasto-Plasticity
    Igelbüscher, M. and Schröder, J. and Schwarz, A. and Starke, G.
    Lecture Notes in Applied and Computational Mechanics 98 149-167 (2022)
    This work presents a mixed least-squares finite element formulation for rate-independent elasto-plasticity at finite strains. In this context, the stress-displacement formulation is defined by the L2(B) -norm minimization of a first-order system of differential equations written in residual form. The utilization of the least-squares method (LSM) provides some well-known advantages. For the proposed rate-independent elasto-plastic material law a straight forward application of the LSM leads to discontinuities within the first variation of the formulation, based on the non-smoothness of the constitutive relation. Therefore, a modification by means of a modified first variation is necessary to guarantee a continuous weak form, which is done in terms of the considered test spaces. In addition to that an antisymmetric displacement gradient in the test space is added to the formulation due to a not a priori fulfillment of the stress symmetry condition, which results from the stress approximation with Raviart-Thomas functions. The resulting formulation is validated by a numerical test and compared to a standard displacement finite element formulation. © 2022, The Author(s), under exclusive license to Springer Nature Switzerland AG.
    view abstractdoi: 10.1007/978-3-030-92672-4_6
  • 2022 • 888 Reduction of submicron particle agglomeration via melt foaming in solid crystalline suspension
    da Igreja, P. and Klump, D. and Bartsch, J. and Thommes, M.
    Journal of Dispersion Science and Technology (2022)
    doi: 10.1080/01932691.2022.2146707
  • 2022 • 887 Increasing the performance of all-solid-state Li batteries by infiltration of Li-ion conducting polymer into LFP-LATP composite cathode
    Ihrig, M. and Dashjav, E. and Laptev, A.M. and Ye, R. and Grüner, D. and Ziegner, M. and Odenwald, P. and Finsterbusch, M. and Tietz, F. and Fattakhova-Rohlfing, D. and Guillon, O.
    Journal of Power Sources 543 (2022)
    doi: 10.1016/j.jpowsour.2022.231822
  • 2022 • 886 Scalar gradient and flame propagation statistics of a flame-resolved laboratory-scale turbulent stratified burner simulation
    Inanc, E. and Kempf, A.M. and Chakraborty, N.
    Combustion and Flame 238 (2022)
    A bluff-body stabilised turbulent jet flame burning in a stratified mode of combustion for fuel-lean methane/air mixtures is investigated by a flame-resolved simulation. A tabulated chemistry approach based on premixed flamelet generated manifolds (PFGM) accounts for thermochemistry. The computations are performed for a grid-resolution of 100 µm, sufficient to resolve the thermal flame thickness. The look-up table is generated with a mixture-averaged diffusivity assumption and the preferential diffusion fluxes are included in the simulation, using an efficient method without increasing the dimensionality of the manifold. The predicted mean and RMS quantities are found to be in good agreement with the experiment. The investigation focuses on the comparison of the combustion behaviour of the upstream locations close to the inlet with weak mixture fraction gradients to the downstream locations away from the inlet with strong mixture fraction gradients. Statistical analysis of the diffusion terms within the flame revealed that the preferential diffusion remains significant near the inlet, in the recirculation zone over the bluff-body. The structure of the stratified flame in downstream locations is statistically analysed in terms of displacement speed and scalar gradients by comparing against the corresponding quantities in upstream locations with weak mixture fraction gradients. It is shown that the displacement speed is statistically different between the flames under weak or strong mixture fraction gradients due to the influence of molecular diffusion and reaction rate components. However, increased curvature effects and cross-dissipation component also play a role. Finally, scalar dissipation and cross-dissipation rates of the mixture fraction fluctuation and the reaction progress variable fluctuation within the flame-brush are investigated, and their closure approaches are discussed. © 2021 The Combustion Institute
    view abstractdoi: 10.1016/j.combustflame.2021.111917
  • 2022 • 885 Thermoelastic fracture analysis of functionally graded materials using the scaled boundary finite element method
    Iqbal, M.D. and Birk, C. and Ooi, E.T. and Pramod, A.L.N. and Natarajan, S. and Gravenkamp, H. and Song, C.
    Engineering Fracture Mechanics 264 (2022)
    The scaled boundary finite element method is extended to model fracture in functionally graded materials (FGM) under coupled thermo-mechanical loads. The governing equations of coupled thermo-mechanical equilibrium are discretized using scaled boundary shape functions enriched with the thermal load terms. The material gradient is modeled as a series of power functions, and the stiffness matrix is calculated semi-analytically. Stress intensity factors and T−stress are directly calculated from their definition without any need for additional post-processing techniques. Arbitrary-sided polygon elements are employed for flexible mesh generation. Several numerical examples for isotropic and orthotropic FGMs are presented to validate the proposed technique. © 2022 Elsevier Ltd
    view abstractdoi: 10.1016/j.engfracmech.2022.108305
  • 2022 • 884 Interpolation Methods with Phase Control for Backprojection of Complex-Valued SAR Data†
    Ivanenko, Y. and Vu, V.T. and Batra, A. and Kaiser, T. and Pettersson, M.I.
    Sensors 22 (2022)
    doi: 10.3390/s22134941
  • 2022 • 883 Broadband THz Interconnect for Hybrid Integration of InP and Si Platforms
    Iwamatsu, S. and Ali, M. and Fernandez-Estevez, J.L. and Makhlouf, S. and Carpintero, G. and Stohr, A.
    International Conference on Infrared, Millimeter, and Terahertz Waves, IRMMW-THz 2022-August (2022)
    We demonstrate a broadband terahertz coupling between InP-based coplanar waveguide and silicon dielectric rod waveguide for hybrid integration. A coupling efficiency of around -2 dB has been experimentally achieved in frequency range between 70-120 GHz. Numerical simulations reveal an operational 3dB-bandwidth >100 GHz. © 2022 IEEE.
    view abstractdoi: 10.1109/IRMMW-THz50927.2022.9895647
  • 2022 • 882 The Implant Proteome—The Right Surgical Glue to Fix Titanium Implants In Situ
    Jäger, M. and Latosinska, A. and Herten, M. and Busch, A. and Grupp, T. and Sowislok, A.
    Journal of Functional Biomaterials 13 (2022)
    doi: 10.3390/jfb13020044
  • 2022 • 881 Bioaktivierung von Scaffolds bei Osteonekrose [Bioactivation of scaffolds in osteonecrosis]
    Jäger, M. and Busch, A. and Sowislok, A.
    Orthopadie (Heidelberg, Germany) 51 808-814 (2022)
    doi: 10.1007/s00132-022-04303-z
  • 2022 • 880 Simulation-based analysis of the propagation behaviour of vibrations generated by reconstruction measures in production environments
    Jaeger, E. and Weist, K. and Gralla, M. and Wiederkehr, P.
    Procedia CIRP 112 128-133 (2022)
    doi: 10.1016/j.procir.2022.09.050
  • 2022 • 879 Synthesis of Turbostratic Boron Nitride: Effect of Urea Decomposition
    Jähnichen, T. and Hojak, J. and Bläker, C. and Pasel, C. and Mauer, V. and Zittel, V. and Denecke, R. and Bathen, D. and Enke, D.
    ACS Omega 7 33375-33384 (2022)
    doi: 10.1021/acsomega.2c04003
  • 2022 • 878 Polystyrene Sulfonate Particles as Building Blocks for Nanofiltration Membranes
    Jahn, P. and Zelner, M. and Freger, V. and Ulbricht, M.
    Membranes 12 (2022)
    doi: 10.3390/membranes12111138
  • 2022 • 877 Early stage, label-free detection of breast cancer based on exosome's protein content alteration
    Jalali, M. and Erni, D.
    Proceedings of SPIE - The International Society for Optical Engineering 12139 (2022)
    doi: 10.1117/12.2621062
  • 2022 • 876 Long-term stable bioprocess-derived Pickering-type emulsions: Identification of key parameters for emulsion stability based on cell interaction at interface
    Janssen, L. and Sadowski, G. and Brandenbusch, C.
    Chemical Engineering Science 264 (2022)
    Industrial implementation of highly potent biphasic whole-cell biocatalytic processes is often limited due to the formation of long-term stable Pickering-type emulsions, caused by the presence of cells. State-of-the-art-concepts for phase separation fail or include inefficient and costly strategies (centrifugation/de-emulsifiers). Using the phenomenon of catastrophic phase inversion (CPI), efficient phase separation can be achieved by addition of dispersed phase. To show the industrial applicability of CPI for phase separations of bioprocess-derived Pickering-type emulsions, the mutual influence of the emulsion components and thus emulsion phase behavior and stability has to be known. Characterizing several Pickering-type emulsions (stabilized by E. coli JM101 and P. putida KT2440 cells), the cell radius, the wettability of cells, and the interfacial tension, were identified to be the most crucial parameters. On this basis, we suggest guidelines and estimation strategies for suitable process (window) selection, assisting in the introduction of these highly potent processes into industrial applications. © 2022 Elsevier Ltd
    view abstractdoi: 10.1016/j.ces.2022.118164
  • 2022 • 875 Investigation of the potential of topology optimization in additive manufacturing using the example of components subject to bending stress [Untersuchung des Potenzials der Topologieoptimierung in der additiven Fertigung am Beispiel von biegebeanspruchten Bauteilen]
    Jantos, D.R. and Röttger, A. and Junker, P.
    Materialwissenschaft und Werkstofftechnik 53 1298-1310 (2022)
    In this application-oriented work, we examine the performance of topology-optimized structures as compared to the reference I-beam. We make use of the thermodynamic topology optimization based on a linear elastic compliance minimization, i. e. minimization of the elastic strain energy of the whole structure. We investigate, how the optimization of the rather theoretical strain energy influences the efficiency of more practical measurements, i. e. the force-displacement response at the loading points and the maximum tolerable force. For this purpose, starting from a cuboid design space with the boundary conditions of a 3-point and 4-point bending stress, the geometry with constant volume was optimized. The topology-optimized bending beams were subsequently produced by stereolithography and mechanically tested with respect to the previously defined boundary conditions. In order to avoid a falsification of results due to internal sample defects, all samples were previously examined with the aid of computer tomography with regard to the defects in the volume. As a general result, the topology-optimized bending beams can bear a higher load in the experiment, which shows the usefulness of the coupling of additive manufacturing and topology optimization methods without any special constraints or enhancements regarding the manufacturing process within the optimization. © 2022 The Authors. Materialwissenschaft und Werkstofftechnik published by Wiley-VCH GmbH.
    view abstractdoi: 10.1002/mawe.202200013
  • 2022 • 874 Application of Photogrammetric Object Reconstruction for Simulation Environments in the Context of Inland Waterways
    Jarofka, M. and Schweig, S. and Maas, N. and Kracht, F.E. and Schramm, D.
    Lecture Notes in Networks and Systems 306 1-17 (2022)
    For the automated generation of simulation environments in the context of inland waterways navigation, a toolchain for the reconstruction of roadside buildings is used for the first time in this field. It was first implemented and tested for the reconstruction of roadside buildings. The toolchain uses data of a stereo camera to automatically generate models of the surrounding objects. This contribution describes the major changes that have to be made to adapt the toolchain to the changed environment. An unmanned aerial vehicle (UAV) is used to take images of specific objects. Due to the limited space on this UAV, only the supplied camera is used. Thus, the further steps in the toolchain have to be adapted. For the evaluation of the resulting model quality images of two bridges are considered. The implemented programs Metashape and Meshroom are compared with each other in terms of quality and computational effort. It is shown that the resulting model quality is better by using the program Metashape. Regarding the computational effort, the necessary time as well as the CPU and GPU utilization are reviewed. Although the GPU utilization is similar, Metashape outperforms Meshroom in terms of CPU utilization and total processing time. Furthermore, two different image recording methods are compared. On the one hand, models are reconstructed from only the top view. On the other hand, a tilted viewing angle with images from both sides of the bridges is used. © 2022, The Author(s), under exclusive license to Springer Nature Switzerland AG.
    view abstractdoi: 10.1007/978-3-030-84811-8_1
  • 2022 • 873 Template for Preparation of Papers for IEEE Sponsored Conferences & Symposia
    Jarofka, M. and Sieberg, P.M. and Hurten, C. and Benedens, T. and Peters, R. and Kracht, F.E. and Schramm, D.
    IEEE Conference on Intelligent Transportation Systems, Proceedings, ITSC 2022-October 1548-1553 (2022)
    doi: 10.1109/ITSC55140.2022.9922371
  • 2022 • 872 Electrochemical CO2 reduction toward multicarbon alcohols - The microscopic world of catalysts & process conditions
    Jaster, T. and Gawel, A. and Siegmund, D. and Holzmann, J. and Lohmann, H. and Klemm, E. and Apfel, U.-P.
    iScience 25 (2022)
    doi: 10.1016/j.isci.2022.104010
  • 2022 • 871 Electrochemistry under confinement
    Jaugstetter, M. and Blanc, N. and Kratz, M. and Tschulik, K.
    Chemical Society Reviews 51 2491-2543 (2022)
    Although the term ‘confinement’ regularly appears in electrochemical literature, elevated by continuous progression in the research of nanomaterials and nanostructures, up until today the various aspects of confinement considered in electrochemistry are rather scattered individual contributions outside the established disciplines in this field. Thanks to a number of highly original publications and the growing appreciation of confinement as an overarching link between different exciting new research strategies, ‘electrochemistry under confinement’ is the process of forming a research discipline of its own. To aid the development a coherent terminology and joint basic concepts, as crucial factors for this transformation, this review provides an overview on the different effects on electrochemical processes known to date that can be caused by confinement. It also suggests where boundaries to other effects, such as nano-effects could be drawn. To conceptualize the vast amount of research activities revolving around the main concepts of confinement, we define six types of confinement and select two of them to discuss the state of the art and anticipated future developments in more detail. The first type concerns nanochannel environments and their applications for electrodeposition and for electrochemical sensing. The second type covers the rather newly emerging field of colloidal single entity confinement in electrochemistry. In these contexts, we will for instance address the influence of confinement on the mass transport and electric field distributions and will link the associated changes in local species concentration or in the local driving force to altered reaction kinetics and product selectivity. Highlighting pioneering works and exciting recent developments, this educational review does not only aim at surveying and categorizing the state-of-the-art, but seeks to specifically point out future perspectives in the field of confinement-controlled electrochemistry. © 2022 The Royal Society of Chemistry
    view abstractdoi: 10.1039/d1cs00789k
  • 2022 • 870 Graphene-Based Metal-Organic Framework Hybrids for Applications in Catalysis, Environmental, and Energy Technologies
    Jayaramulu, K. and Mukherjee, S. and Morales, D.M. and Dubal, D.P. and Nanjundan, A.K. and Schneemann, A. and Masa, J. and Kment, S. and Schuhmann, W. and Otyepka, M. and Zbořil, R. and Fischer, R.A.
    Chemical Reviews (2022)
    Current energy and environmental challenges demand the development and design of multifunctional porous materials with tunable properties for catalysis, water purification, and energy conversion and storage. Because of their amenability to de novo reticular chemistry, metal-organic frameworks (MOFs) have become key materials in this area. However, their usefulness is often limited by low chemical stability, conductivity and inappropriate pore sizes. Conductive two-dimensional (2D) materials with robust structural skeletons and/or functionalized surfaces can form stabilizing interactions with MOF components, enabling the fabrication of MOF nanocomposites with tunable pore characteristics. Graphene and its functional derivatives are the largest class of 2D materials and possess remarkable compositional versatility, structural diversity, and controllable surface chemistry. Here, we critically review current knowledge concerning the growth, structure, and properties of graphene derivatives, MOFs, and their graphene@MOF composites as well as the associated structure-property-performance relationships. Synthetic strategies for preparing graphene@MOF composites and tuning their properties are also comprehensively reviewed together with their applications in gas storage/separation, water purification, catalysis (organo-, electro-, and photocatalysis), and electrochemical energy storage and conversion. Current challenges in the development of graphene@MOF hybrids and their practical applications are addressed, revealing areas for future investigation. We hope that this review will inspire further exploration of new graphene@MOF hybrids for energy, electronic, biomedical, and photocatalysis applications as well as studies on previously unreported properties of known hybrids to reveal potential "diamonds in the rough". ©
    view abstractdoi: 10.1021/acs.chemrev.2c00270
  • 2022 • 869 Dynamical photon–photon interaction mediated by a quantum emitter
    Jeannic, H.L. and Tiranov, A. and Carolan, J. and Ramos, T. and Wang, Y. and Appel, M.H. and Scholz, S. and Wieck, A.D. and Ludwig, Ar. and Rotenberg, N. and Midolo, L. and García-Ripoll, J.J. and Sørensen, A.S. and Lodahl, P.
    Nature Physics 18 1191-1195 (2022)
    Single photons role in the development of quantum science and technology. They can carry quantum information over extended distances to act as the backbone of a future quantum internet1 and can be manipulated in advanced photonic circuits, enabling scalable photonic quantum computing2,3. However, more sophisticated devices and protocols need access to multi-photon states with particular forms of entanglement. Efficient light–matter interfaces offer a route to reliably generating these entangled resource states4,5. Here we utilize the efficient and coherent coupling of a single quantum emitter to a nanophotonic waveguide to realize a quantum nonlinear interaction between single-photon wavepackets. We demonstrate the control of a photon using a second photon mediated by the quantum emitter. The dynamical response of the two-photon interaction is experimentally unravelled and reveals quantum correlations controlled by the pulse duration. Further development of this platform work, which constitutes a new research frontier in quantum optics6, will enable the tailoring of complex photonic quantum resource states. © 2022, The Author(s), under exclusive licence to Springer Nature Limited.
    view abstractdoi: 10.1038/s41567-022-01720-x
  • 2022 • 868 High-throughput exploration of activity and stability for identifying photoelectrochemical water splitting materials
    Jenewein, K.J. and Thienhaus, S. and Kormányos, A. and Ludwig, Al. and Cherevko, S.
    Chemical Science 13 13774-13781 (2022)
    doi: 10.1039/d2sc05115j
  • 2022 • 867 AN EULER-BASED THROUGHFLOW APPROACH FOR CENTRIFUGAL COMPRESSORS - PART A: EXTENSION AND MODIFICATIONS OF MODELS
    Jenzen, R. and Woiczinski, C. and Schuster, S. and Brillert, D.
    Proceedings of the ASME Turbo Expo 7 (2022)
    doi: 10.1115/GT2022-82170
  • 2022 • 866 The Identification of Spectral Signatures in Randomized (Sub-)Surface Material Systems
    Jerbic, K. and Svejda, J.T. and Sievert, B. and Liu, X. and Kolpatzeck, K. and Degen, M. and Rennings, A. and Czylwik, A. and Balzer, J. and Erni, D.
    2022 5th International Workshop on Mobile Terahertz Systems, IWMTS 2022 (2022)
    doi: 10.1109/IWMTS54901.2022.9832449
  • 2022 • 865 An Assessment of Solvers for Algebraically Stabilized Discretizations of Convection-Diffusion-Reaction Equations
    Jha, A. and Pártl, O. and Ahmed, N. and Kuzmin, D.
    Journal of Numerical Mathematics (2022)
    We consider flux-corrected finite element discretizations of 3D convection-dominated transport problems and assess the computational efficiency of algorithms based on such approximations. The methods under investigation include flux-corrected transport schemes and monolithic limiters. We discretize in space using a continuous Galerkin method and P1 or Q1 finite elements. Time integration is performed using the Crank-Nicolson method or an explicit strong stability preserving Runge-Kutta method. Nonlinear systems are solved using a fixed-point iteration method, which requires solution of large linear systems at each iteration or time step. The great variety of options in the choice of discretization methods and solver components calls for a dedicated comparative study of existing approaches. To perform such a study, we define new 3D test problems for time dependent and stationary convection-diffusion-reaction equations. The results of our numerical experiments illustrate how the limiting technique, time discretization and solver impact on the overall performance. © 2022 Walter de Gruyter GmbH, Berlin/Boston 2022.
    view abstractdoi: 10.1515/jnma-2021-0123
  • 2022 • 864 Numerical Investigation of Hydroelastic Effects on Floating Structures
    Jiang, C. and el Moctar, O. and Schellin, T.E. and Qi, Y.
    Lecture Notes in Civil Engineering 158 309-330 (2022)
    Hydroelasticity effects of an offshore floating structure comprise the combined motions and deformations of the floating body responding to environmental excitations. The review of research on hydroelasticity of very large floating structure shows that understanding the physical phenomenon has increased, but discussions of practical implications of hydroelasticity on offshore structure design are rare. Conventionally, floating structure designs are based on a rigid quasi-static analysis, meaning that the hydrodynamic loads are estimated under rigid assumption and then applied to the elastic structure regardless of structural inertia. Here, the hydroelastic behavior of a standard floating module designed within the scope of the Space@Sea project was numerically investigated, and the role of hydroelasticity in the practical assessment of a large floating structure was demonstrated. The fluid dynamics relied on a Computational Fluid Dynamics (CFD) code, and the structural responses were computed by a Computational Structural Dynamics (CSD) solver. The CFD-CSD solver was coupled using an implicit two-way coupling approach, computing the nonlinear 6-DoF rigid body motion separately from linear elastic structural deformations. First, the numerical model was validated against benchmark test data, and then a standard floating module in waves was assessed in terms of structural integrity and motions. Maximum stresses and bending moments obtained by the coupled CFD-CSD approach and the traditional rigid-quasi-static approach were compared, and the implication of hydroelasticity on the floating module was assessed. The hydroelastic criterion and the validity of a rigid a quasi-static analysis determined the effects on dynamic responses. © 2022, The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd.
    view abstractdoi: 10.1007/978-981-16-2256-4_19
  • 2022 • 863 Capability of a potential-flow solver to analyze articulated multibody offshore modules
    Jiang, C. and el Moctar, O. and Schellin, T.E.
    Ocean Engineering 266 (2022)
    doi: 10.1016/j.oceaneng.2022.112754
  • 2022 • 862 Numerical investigation of wave-induced loads on an offshore monopile using a viscous and a potential-flow solver
    Jiang, C. and el Moctar, O.
    Journal of Ocean Engineering and Marine Energy 8 381-397 (2022)
    doi: 10.1007/s40722-022-00237-y
  • 2022 • 861 SIMULATION OF A MOORED MULTIBODY OFFSHORE STRUCTURE ARTICULATED BY DIFFERENT JOINTS IN WAVES
    Jiang, C. and el Moctar, O. and Zhang, G. and Schellin, T.E.
    Proceedings of the International Conference on Offshore Mechanics and Arctic Engineering - OMAE 5-B (2022)
    doi: 10.1115/OMAE2022-79571
  • 2022 • 860 Extension of a coupled mooring–viscous flow solver to account for mooring–joint–multibody interaction in waves
    Jiang, C. and el Moctar, O.
    Journal of Ocean Engineering and Marine Energy (2022)
    doi: 10.1007/s40722-022-00252-z
  • 2022 • 859 Influence of brazing process and gap size on the fatigue strength of shear and peel specimen
    Jöckel, A. and Baumgartner, J. and Tillmann, W. and Bültena, J. and Bobzin, K. and Heinemann, H. and Hebing, J. and Erck, M.
    Welding in the World 66 1941-1955 (2022)
    Brazing is a joining technique used in many industries for components that consist of many individual parts. Many of these components are cyclically loaded during service. For this reason, reliable approaches to assess the service life must be developed. For this purpose, it is necessary to gain knowledge about factors influencing the fatigue strength and the damage behavior. In this paper induction, vacuum- and continuous furnace brazed shear and peel specimen with different brazing gap widths are analyzed. Therefore, the specimens were characterized, measuring the geometry of the specimens and surface condition of the brazing radii, and tested under load control using constant amplitudes. It is found that the manufacturing process and the parameters used have a significant influence on the mechanical properties of the brazing material, the surface condition and the profile of the fillet radii. These properties have again an influence on the damage behavior and the fatigue strength. In particular crack-like defects of varying severity, which can extend deep into the brazing material, that are located in highly stressed areas of the fillet radii have a significant influence on the fatigue strength. It is also found that, regardless of the brazing process used, there is a tendency in the area of the brazing gap width for the number and size of defects to increase with increasing gap size, which can negatively affect fatigue strength depending on the damage behavior. © 2022, The Author(s).
    view abstractdoi: 10.1007/s40194-022-01304-6
  • 2022 • 858 Spin Crossover in a Cobalt Complex on Ag(111)
    Johannsen, S. and Ossinger, S. and Grunwald, J. and Herman, A. and Wende, H. and Tuczek, F. and Gruber, M. and Berndt, R.
    Angewandte Chemie - International Edition 61 (2022)
    The Co-based complex [Co(H2B(pz)(pypz))2] (py=pyridine, pz=pyrazole) deposited on Ag(111) was investigated with scanning tunneling microscopy at ≈5 K. Due to a bis(tridentate) coordination sphere the molecules aggregate mainly into tetramers. Individual complexes in these tetramers undergo reversible transitions between two states with characteristic image contrasts when current is passed through them or one of their neighbors. Two molecules exhibit this bistability while the other two molecules are stable. The transition rates vary linearly with the tunneling current and exhibit an intriguing dependence on the bias voltage and its polarity. We interpret the states as being due to S=1/2 and 3/2 spin states of the Co2+ complex. The image contrast and the orders-of-magnitude variations of the switching yields can be tentatively understood from the calculated orbital structures of the two spin states, thus providing first insights into the mechanism of electron-induced excited spin-state trapping (ELIESST). © 2022 The Authors. Angewandte Chemie International Edition published by Wiley-VCH GmbH
    view abstractdoi: 10.1002/anie.202115892
  • 2022 • 857 A bioinspired redox-modulating copper(ii)-macrocyclic complex bearing non-steroidal anti-inflammatory drugs with anti-cancer stem cell activity
    Johnson, A. and Iffland-Mühlhaus, L. and Northcote-Smith, J. and Singh, K. and Ortu, F. and Apfel, U.-P. and Suntharalingam, K.
    Dalton Transactions 51 5904-5912 (2022)
    doi: 10.1039/d2dt00788f
  • 2022 • 856 Impact of Sterilization on the Colloidal Stability of Ligand-Free Gold Nanoparticles for Biomedical Applications
    Johny, J. and Van Halteren, C.E.R. and Zwiehoff, S. and Behrends, C. and Bäumer, C. and Timmermann, B. and Rehbock, C. and Barcikowski, S.
    Langmuir 38 13030-13047 (2022)
    doi: 10.1021/acs.langmuir.2c01557
  • 2022 • 855 Polyurea Thickened Lubricating Grease—The Effect of Degree of Polymerization on Rheological and Tribological Properties
    Jopen, M. and Degen, P. and Henzler, S. and Grabe, B. and Hiller, W. and Weberskirch, R.
    Polymers 14 (2022)
    Lubricating greases based on urea thickeners are frequently used in high-performance applications since their invention in 1954. One property that has so far been neglected in the further development of these systems due to their low solubility and the resulting difficulty of analysis, is to better understand how the degree of polymerization affect such polyurea lubricating systems. In this work, we prepared three different oligoor polyurea systemswith different degrees of polymerization (DP) and investigated the influence of DP on rheological and tribological properties. The results showed that the DP has an influence on the flow limit in rheology as well as on the extreme pressure (EP) and anti-wear (AW) properties as examined by tribology measurements. By optimizing the DP for a thickener system, comparable EP and AW properties can be achieved through the use of additives. The DP showed an increasing influence on the flow limit. This could reduce damage to rolling bearings due to lateral loading at rest. Therefore, modifying the DP of the polyurea systems shows similar effects as the addition of external additives. Overall, this would reduce the use of additives in industrial applications. © 2022 by the authors.Licensee MDPI, Basel, Switzerland.
    view abstractdoi: 10.3390/polym14040795
  • 2022 • 854 Particle Size-Dependent Onset of the Tunneling Regime in Ideal Dimers of Gold Nanospheres
    Jose, J. and Schumacher, L. and Jalali, M. and Haberfehlner, G. and Svejda, J.T. and Erni, D. and Schlücker, S.
    ACS Nano 16 21377-21387 (2022)
    doi: 10.1021/acsnano.2c09680
  • 2022 • 853 A cracking oxygen story: A new view of stress corrosion cracking in titanium alloys
    Joseph, S. and Kontis, P. and Chang, Y. and Shi, Y. and Raabe, D. and Gault, B. and Dye, D.
    Acta Materialia 227 (2022)
    Titanium alloys can suffer from halide-associated stress corrosion cracking at elevated temperatures e.g., in jet engines, where chlorides and Ti-oxide promote the cracking of water vapour in the gas stream, depositing embrittling species at the crack tip. Here we report, using isotopically-labelled experiments, that crack tips in an industrial Ti-6Al-2Sn-4Zr-6Mo alloy are strongly enriched (>5 at.%) in oxygen from the water vapour, far greater than the amounts (0.25 at.%) required to embrittle the material. Surprisingly, relatively little hydrogen (deuterium) is measured, despite careful preparation and analysis. Therefore, we suggest that a combined effect of O and H leads to cracking, with O playing a vital role, since it is well-known to cause embrittlement of the alloy. In contrast it appears that in α + β Ti alloys, it may be that H may drain away into the bulk owing to its high solubility in β-Ti, rather than being retained in the stress field of the crack tip. Therefore, whilst hydrides may form on the fracture surface, hydrogen ingress might not be the only plausible mechanism of embrittlement of the underlying matrix. This possibility challenges decades of understanding of stress-corrosion cracking as being related solely to the hydrogen enhanced localised plasticity (HELP) mechanism, which explains why H-doped Ti alloys are embrittled. This would change the perspective on stress corrosion embrittlement away from a focus purely on hydrogen to also consider the ingress of O originating from the water vapour, insights critical for designing corrosion resistant materials. © 2022 Acta Materialia Inc.
    view abstractdoi: 10.1016/j.actamat.2022.117687
  • 2022 • 852 Transient uptake measurements with a physisorption instrument: Trends in gas-phase diffusivities within mesoporous materials
    Joshi, H. and Hopf, A. and Losch, P. and Schmidt, W. and Schüth, F.
    Microporous and Mesoporous Materials 330 (2022)
    The measurement of diffusivity within porous solids is vital for the characterization of materials, especially in heterogeneous catalysis and separation processes. Numerous methods have been developed to measure gas-phase diffusivities within materials. However, establishing correlations between the diffusivities and the properties of a material is challenging. Herein, we report a method for obtaining trends in gas-phase diffusivity of N2 at 77 K within three different sets of mesoporous materials, disordered, ordered silica, and carbons-based materials. Synthesis procedures are reproducible and controlled precisely to achieve monodisperse particle size and defined pore size distributions. A standard physisorption device, Micromeritics 3Flex, is used to obtain the required transient data. These two aspects offer a suitable database of materials to identify trends and reduce the challenges associated with obtaining experimental data. A simplified model is fitted over the transient data with MATLAB to obtain empirical diffusivities used for trend analysis. The trends are based on a constant Dτ, an ensemble value representing various diffusion processes occurring during a transient uptake process. The analysis identifies several correlations between the diffusivity and properties of materials, such as type of pore structure, pore size, and the chemical nature of the material. Based on the principles reported, this study can be extended to other adsorptive molecules or different temperatures. The possibility of using standard sorption instrumentation will allow a broader user community to employ the reported methodology. © 2021 Elsevier Inc.
    view abstractdoi: 10.1016/j.micromeso.2021.111627
  • 2022 • 851 Spin-polarized hybrid states in epitaxially-aligned and rotated graphene on cobalt
    Jugovac, M. and Donkor, E.D. and Moras, P. and Cojocariu, I. and Genuzio, F. and Zamborlini, G. and Di Santo, G. and Petaccia, L. and Stojić, N. and Feyer, V. and Schneider, C.M. and Locatelli, A. and Menteş, T.O.
    Carbon 198 188-194 (2022)
    The strong interaction between graphene and elemental ferromagnetic transition metals results in considerable shifts of the graphene π band away from the Fermi level. At the same time, a weakly-dispersing single-spin conical band feature is found in the proximity of the Fermi level at the K̄ point in the surface Brillouin zone of epitaxially-aligned graphene/Co(0001). Here, the robustness of this electronic state against twisting angles at the interface is experimentally and theoretically demonstrated by showing the presence of similar band features also in the case of rotated graphene domains on Co(0001). Spin-resolved reciprocal space maps show that the band feature in rotated graphene has similar Fermi velocity and spin polarization as its counterpart in epitaxially-aligned graphene. Density functional theory simulations carried out for the experimentally observed graphene orientations, reproduce the highly spin-polarized conical band feature at the graphene K̄ point, characterized by a hybrid π-d orbital character. The presence of the conical features in the rotated domains is attributed to the unfolding of the superstructure K̄ point states exclusively to the K̄ point of the graphene primitive cell. The similarities found in the electronic character for different graphene orientations are crucial in understanding the magnetic properties of realistic graphene/Co interfaces, facilitating their implementation in spintronics applications. © 2022 Elsevier Ltd
    view abstractdoi: 10.1016/j.carbon.2022.07.011
  • 2022 • 850 Propagation of nanosecond plasmas in liquids - Streamer velocities and streamer lengths
    Jungling, E. and Grosse, K. and Von Keudell, A.
    Journal of Vacuum Science and Technology A: Vacuum, Surfaces and Films 40 (2022)
    Nanosecond plasmas in liquids are often generated by applying a short high voltage pulse to an electrode immersed in a liquid for biomedical or environmental applications. The plasmas appear as streamers that propagate through the liquid. The understanding of the ignition of these nanosecond plasmas in liquids, however, is an open question. The occurrence of any traditional gas phase ignition mechanism is unlikely, because the formation of a gas bubble prior to ignition is suppressed by the inertia of the liquid. Therefore, either electron multiplication inside nanopores that are induced by an electric field pressure gradient or field effects at the tip and at the ionization front of the liquid streamer may act as electron generation mechanisms. A deeper understanding can be achieved by comparing the velocity and dynamic of the plasma propagation with modeling, where the individual mechanisms and transport coefficients can be analyzed. Here, we are using intensified charge-coupled device imaging to investigate the time dependence of the streamer dynamic and compare this with a 1D fluid code for negative voltages. It is shown that the maximum streamer length scales with the applied electric field, indicating that an electric stability field in the liquid streamer channel is important, as known for gas streamers. The 1D fluid code can reproduce the proper streamer velocities, if transport coefficients for hydrated electrons are chosen. The model suggests that the propagation of liquid streamers is dominated by the local ionization rate at the ionization front rather than by advection or diffusion of electrons as in gases. This also explains the finding that positive and negative streamers exhibit almost identical electron densities. © 2022 Author(s).
    view abstractdoi: 10.1116/6.0001669
  • 2022 • 849 Efficient and robust numerical treatment of a gradient-enhanced damage model at large deformations
    Junker, P. and Riesselmann, J. and Balzani, D.
    International Journal for Numerical Methods in Engineering 123 774-793 (2022)
    The modeling of damage processes in materials constitutes an ill-posed mathematical problem which manifests in mesh-dependent finite element results. The loss of ellipticity of the discrete system of equations is counteracted by regularization schemes of which the gradient enhancement of the strain energy density is often used. In this contribution, we present an extension of the efficient numerical treatment, which has been proposed by Junker et al. in 2019, to materials that are subjected to large deformations. Along with the model derivation, we present a technique for element erosion in the case of severely damaged materials. Efficiency and robustness of our approach is demonstrated by two numerical examples including snapback and springback phenomena. © 2021 The Authors. International Journal for Numerical Methods in Engineering published by John Wiley & Sons Ltd.
    view abstractdoi: 10.1002/nme.6876
  • 2022 • 848 Structural and electron spin state changes in an x-ray heated iron carbonate system at the Earth's lower mantle pressures
    Kaa, J.M. and Sternemann, C. and Appel, K. and Cerantola, V. and Preston, T.R. and Albers, C. and Elbers, M. and Libon, L. and Makita, M. and Pelka, A. and Petitgirard, S. and Plückthun, C. and Roddatis, V. and Sahle, C.J. and Sp...
    Physical Review Research 4 (2022)
    The determination of the spin state of iron-bearing compounds at high pressure and temperature is crucial for our understanding of chemical and physical properties of the deep Earth. Studies on the relationship between the coordination of iron and its electronic spin structure in iron-bearing oxides, silicates, carbonates, iron alloys, and other minerals found in the Earth's mantle and core are scarce because of the technical challenges to simultaneously probe the sample at high pressures and temperatures. We used the unique properties of a pulsed and highly brilliant x-ray free electron laser (XFEL) beam at the High Energy Density (HED) instrument of the European XFEL to x-ray heat and probe samples contained in a diamond anvil cell. We heated and probed with the same x-ray pulse train and simultaneously measured x-ray emission and x-ray diffraction of an FeCO3 sample at a pressure of 51 GPa with up to melting temperatures. We collected spin state sensitive Fe Kβ1,3 fluorescence spectra and detected the sample's structural changes via diffraction, observing the inverse volume collapse across the spin transition. During x-ray heating, the carbonate transforms into orthorhombic Fe4C3O12 and iron oxides. Incipient melting was also observed. This approach to collect information about the electronic state and structural changes from samples contained in a diamond anvil cell at melting temperatures and above will considerably improve our understanding of the structure and dynamics of planetary and exoplanetary interiors. © 2022 authors. Published by the American Physical Society.
    view abstractdoi: 10.1103/PhysRevResearch.4.033042
  • 2022 • 847 Kinetic investigation of the ozone-assisted partial oxidation of fuel-rich natural gas mixtures at elevated pressure
    Kaczmarek, D. and Rudolph, C. and Atakan, B. and Kasper, T.
    Proceedings of the Combustion Institute (2022)
    doi: 10.1016/j.proci.2022.07.195
  • 2022 • 846 Wide-Angle Ceramic Retroreflective Luneburg Lens Based on Quasi-Conformal Transformation Optics for Mm-Wave Indoor Localization
    Kadera, P. and Sanchez-Pastor, J. and Eskandari, H. and Tyc, T. and Sakaki, M. and Schusler, M. and Jakoby, R. and Benson, N. and Jimenez-Saez, A. and Lacik, J.
    IEEE Access 10 41097-41111 (2022)
    doi: 10.1109/ACCESS.2022.3166509
  • 2022 • 845 Experimental study of the influence of mesoscale surface structuring on single bubble dynamics
    Kadivar, E. and el Moctar, O. and Sagar, H.J.
    Ocean Engineering 260 (2022)
    doi: 10.1016/j.oceaneng.2022.111892
  • 2022 • 844 One-Pot Multicomponent Synthesis of Allyl and Alkylamines Using a Catalytic System Composed of Ruthenium Nanoparticles on Copper N-Heterocyclic Carbene-Modified Silica
    Kalsi, D. and Louis Anandaraj, S.J. and Durai, M. and Weidenthaler, C. and Emondts, M. and Nolan, S.P. and Bordet, A. and Leitner, W.
    ACS Catalysis 12 14902-14910 (2022)
    doi: 10.1021/acscatal.2c04044
  • 2022 • 843 Hardware/Software Co-design of 2D THz SAR Imaging for FPGA-based Systems-on-Chip
    Kamaleldin, A. and Aliagha, E. and Batra, A. and Wiemeler, M. and Kaiser, T. and Gohringer, D.
    2022 5th International Workshop on Mobile Terahertz Systems, IWMTS 2022 (2022)
    doi: 10.1109/IWMTS54901.2022.9832447
  • 2022 • 842 Isothermal hot tube material characterization – Forming limits and flow curves of stainless steel tubes at elevated temperatures
    Kamaliev, M. and Kolpak, F. and Tekkaya, A.E.
    Journal of Materials Processing Technology 309 (2022)
    doi: 10.1016/j.jmatprotec.2022.117757
  • 2022 • 841 Invariants in the paramagnetic resonance spectra of impurity-doped crystals
    Kamenskii, A.N. and Kozlov, V.O. and Kuznetsov, N.S. and Ryzhov, I.I. and Kozlov, G.G. and Bayer, M. and Greilich, A. and Zapasskii, V.S.
    Physical Review B 105 (2022)
    We show that in cubic crystals with anisotropic impurity centers the sum of squares of the magnetic resonance [electron paramagnetic resonance (EPR)] frequencies is invariant with respect to the magnetic field direction. The connection between such an invariant and the g-tensor components of the impurity is derived for different types of centers. The established regularity is confirmed experimentally for the spin-noise spectra of a cubic CaF2-Nd3+ crystal. We show how this property of the EPR spectra can be efficiently used for the assignment of paramagnetic centers in cubic crystals. © 2022 American Physical Society.
    view abstractdoi: 10.1103/PhysRevB.105.014416
  • 2022 • 840 Bistable H2Pc Molecular Conductance Switch on Ag(100)
    Kamiński, W. and Antczak, G. and Morgenstern, K.
    Journal of Physical Chemistry C 126 16767-16776 (2022)
    Scanning tunneling microscopy (STM) and density functional theory (DFT) were used to study the tautomerization reaction of an H2Pc molecule adsorbed on a Ag(100) surface. The presence of two hydrogen atoms in the cavity of the H2Pc molecule enforces the existence of two molecular tautomers. It causes a reduction from 4- to 2-fold symmetry in STM images that can be recorded as two current states over the H2Pc molecule with a high-to-low current state ratio of ∼1.2. These findings are confirmed by the spatial distributions of the all-atom electron charge density calculated by using DFT and transmission maps together with tunneling current ratios (∼1.2) determined from the nonequilibrium Green's function transport calculations. Therefore, we demonstrate that an H2Pc molecule adsorbed on a Ag(100) surface is a good candidate for a bistable molecular conductance switch since neither the presence of the Ag(100) surface nor that of the STM tip alters the tautomerization. © 2022 American Chemical Society.
    view abstractdoi: 10.1021/acs.jpcc.2c03485
  • 2022 • 839 Design and characterization of a cascode switching stage for high frequency radiation hardened DC/DC converters for the supply of future pixel detectors
    Kampkoetter, J. and Karagounis, M. and Kokozinski, R.
    Journal of Instrumentation 17 (2022)
    doi: 10.1088/1748-0221/17/12/C12022
  • 2022 • 838 Characterization and verification of the Shunt-LDO regulator and its protection circuits for serial powering of the ATLAS and CMS pixel detectors
    Kampkötter, J. and Karagounis, M. and Koukola, D. and Loddo, F. and Orfanelli, S. and Luengo, A.P. and Traversi, G. and Kokozinski, R.
    Journal of Physics: Conference Series 2374 (2022)
    doi: 10.1088/1742-6596/2374/1/012071
  • 2022 • 837 Efficient Synthesis of Macromolecular DO3A@Gn Derivatives for Potential Application in MRI Diagnostics: From Polymer Conjugates to Polymer Nanoparticles
    Kampmann, A.-L. and Hiller, W. and Weberskirch, R.
    Macromolecular Chemistry and Physics (2022)
    Here, the synthesis of three different macromolecular DO3A@Gn conjugates based on poly(2-oxazoline)s is presented. Therefore, poly(2-methyl-2-oxazoline) is synthesized by a ring-opening, cationic polymerization and the polymerization is terminated with DO3A(tBu)3. The best results are obtained after 48 h at 120 °C with degree of termination of 86%. After deprotection of the DO3A ligand and complexation with Gn3+, relaxivity as measured with a magnetic field strength of 9.4 T (400 MHz) reveals values for r1 of up to 2.32 mm−1 s−1. The concept is extended to a block copolymer based on 2-heptyl-2-oxazoline and 2-methyl-2-oxazoline that is again terminated with DO3A(tBu)3 to form micelles with a size of 12.6 ± 0.7 nm after DO3A(tBu)3 termination and deprotection of the 1,4,7,10-tetraazacyclododecane-N,N,N,N-tetraacetic acid ligand. After complexation with Gn3+, relaxivity r1 is 10.1 mm−1 s−1 as determined from the slope of the plot of 1/T1 against the gadolinium(III) concentration at 9.4 T. Finally, crosslinked nanoparticles are prepared from amphiphilic macro-monomers that form micelles in water and are crosslinked throughout the core in the presence of azoisobutyronitrile (AIBN). The nanoparticle is 32.9 ± 7.8 nm in size after Gn3+ complexation and reveals a relaxivity r1 of 6.77 mm−1 s−1. © 2022 The Authors. Macromolecular Chemistry and Physics published by Wiley-VCH GmbH.
    view abstractdoi: 10.1002/macp.202200211
  • 2022 • 836 Improved protective clothing for welders with nanoparticles
    Kamps, Leonie and Gutmann, Jochen S. and Mayer-Call, Thomas and Textor, Torsten
    Melliand International 28 190 – 191 (2022)
  • 2022 • 835 Electronic Circuit Simulations as a Tool to Understand Distorted Signals in Single-Entity Electrochemistry
    Kanokkanchana, K. and Tschulik, K.
    Journal of Physical Chemistry Letters 13 10120-10125 (2022)
    Electrochemical analysis relies on precise measurement of electrical signals, yet the distortions caused by potentiostat circuitry and filtering are rarely addressed. Elucidation of these effects is essential for gaining insights behind sensitive low-current and short-duration electrochemical signals, e.g., in single-entity electrochemistry. We present a simulation approach utilizing the Electrical Simulation Program with Integrated Circuit Emphasis (SPICE), which is extensively used in electronic circuit simulations. As a proof-of-concept, we develop a universal electrical circuit model for single nanoparticle impact experiments, incorporating potentiostat and electronic filter circuitry. Considering these alterations, the experimentally observed transients of silver nanoparticle oxidation were consistently shorter and differently shaped than those predicted by established models. This reveals the existence of additional processes, e.g., migration, partial or asymmetric oxidation. These results highlight the SPICE approach's ability to provide valuable insights into processes occurring during single-entity electrochemistry, which can be applied to various electrochemical experiments, where signal distortions are inevitable. © 2022 American Chemical Society. All rights reserved.
    view abstractdoi: 10.1021/acs.jpclett.2c02720
  • 2022 • 834 A High Temperature SOI-CMOS Chipset Focusing Sensor Electronics for Operating Temperatures up to 300°C
    Kappert, H. and Braun, S. and Kordas, N. and Kosfeld, A. and Utz, A. and Weber, C. and Rämer, O. and Spanier, M. and Ihle, M. and Ziesche, S. and Kokozinski, R.
    Journal of Microelectronics and Electronic Packaging 19 1-7 (2022)
    Sensors are the key elements for capturing environmental properties and are increasingly important in the industry for the intelligent control of industrial processes. While in many everyday objects highly integrated sensor systems are already state of the art, the situation in an industrial environment is clearly different. Frequently, the use of sensor systems is impossible, because the extreme ambient conditions of industrial processes like high operating temperatures or strong mechanical load do not allow the reliable operation of sensitive electronic components. Fraunhofer is running the Lighthouse Project "eHarsh"to overcome this hurdle. In the course of the project, an integrated sensor readout electronic has been realized based on a set of three chips. A dedicated sensor frontend provides the analog sensor interface for resistive sensors typically arranged in a Wheatstone configuration. Furthermore, the chipset includes a 32-bit microcontroller for signal conditioning and sensor control. Finally, it comprises an interface chip including a bus transceiver and voltage regulators. The chipset has been realized in a high-temperature 0.35-micron SOI-CMOS technology focusing operating temperatures up to 300_C. The chipset is assembled on a multilayer ceramic low-temperature cofired ceramics (LTCC) board using flip chip technology. The ceramic board consists of four layers with a total thickness of approximately 0.9 mm. The internal wiring is based on silver paste while the external contacts were alternatively manufactured in silver (sintering/soldering) or in gold alloys (wire bonding). As an interconnection technology, silver sintering has been applied. It has already been shown that a significant increase in lifetime can be reached by using silver sintering for die attach applications. Using silver sintering for flip chip technology is a new and challenging approach. By adjusting the process parameter geared to the chipset design and the design of the ceramic board high-quality flip chip interconnects can be generated. © 2022 International Microelectronics Assembly and Packaging Society.
    view abstractdoi: 10.4071/imaps.1547377
  • 2022 • 833 Sensor Systems for Extremely Harsh Environments
    Kappert, H. and Schopferer, S. and Saeidi, N. and Döring, R. and Ziesche, S. and Olowinsky, A. and Naumann, F. and Jägle, M. and Spanier, M. and Grabmaier, A.
    Journal of Microelectronics and Electronic Packaging 19 101-114 (2022)
    doi: 10.4071/001C.57715
  • 2022 • 832 Characterization of spray parameters and flame stability in two modified nozzle configurations of the SpraySyn burner
    Karaminejad, S. and Dupont, S.M.L. and Bieber, M. and Reddemann, M.A. and Kneer, R. and Dreier, T. and Endres, T. and Schulz, C.
    Proceedings of the Combustion Institute (2022)
    doi: 10.1016/j.proci.2022.07.248
  • 2022 • 831 Optimizing Fouling Resistance of Poly(Sulfabetaine)s through Backbone and Charge Separation
    Karthäuser, J.F. and Koc, J. and Schönemann, E. and Wanka, R. and Aldred, N. and Clare, A.S. and Rosenhahn, A. and Laschewsky, A.
    Advanced Materials Interfaces (2022)
    The three dominating polyzwitterion families, polyphosphatidylcholines, polycarboxybetaines, and polysulfobetaines, all of which provide high fouling resistance, have been complemented by a fourth one recently, the so-called polysulfabetaines that combine ammonium with sulfate moieties. To elucidate the relationship between their structure and antifouling potential, coatings of a set of systematically varied poly(sulfabetaine methacrylate)s are investigated. In particular, the effects of the spacer groups, either separating the zwitterionic units from the polymer backbone, or the cationic from the anionic charges, are explored, studying the resistance against non-specific protein adsorption and the accumulation of single species of marine biofouling organisms. All polysulfabetaines are at least as effective, or even more potent than the structurally closely related standard poly(sulfobetaine methacrylate). Their resistance against proteins and fouling organisms can be tuned via the betaine-to-backbone spacer. Overall, the polysulfabetaine coatings with the shorter ethylene spacer show higher resistance against non-specific adsorption of proteins, in particular of lysozyme, or against colonization by diatoms. This may result from the higher steric constraints of the polymer attached zwitterions, favoring particularly advantageous conformations. Moreover, a shorter spacer between the oppositely charged ionic groups of the zwitterionic moiety reduces the settlement of cyprid larvae more effectively. © 2022 The Authors. Advanced Materials Interfaces published by Wiley-VCH GmbH.
    view abstractdoi: 10.1002/admi.202200677
  • 2022 • 830 Corrosion of NiTi stents induced by galvanic interaction with radiopaque materials
    Kassab, E. and Frotscher, M. and Eggeler, G. and Ponciano Gomes, J.A.C.
    Materials Today Communications 33 (2022)
    doi: 10.1016/j.mtcomm.2022.104401
  • 2022 • 829 Atomic/molecular layer deposition of cerium(iii) hybrid thin films using rigid organic precursors
    Kaur, P. and Muriqi, A. and Wree, J.-L. and Ghiyasi, R. and Safdar, M. and Nolan, M. and Karppinen, M. and Devi, A.
    Dalton Transactions 51 5603-5611 (2022)
    doi: 10.1039/d2dt00353h
  • 2022 • 828 PREPARATION AND ANALYSIS OF MEMBRANE ELECTRODE ASSEMBLIES FOR PEM WATER ELECTROLYSERS BASED ON LASER-GENERATED IRIDIUMOXIDE NANOPARTICLES AS ELECTROCATALYSTS FOR THE OXYGEN EVOLUTION REACTION
    Kazamer, N. and Reichenberger, S. and Spree, M. and Rost, U. and Tack, M. and Bopardikar, T. and Wirkert, F. and Salih, H. and Böhm, L. and Cieluch, M. and Roth, J. and Zoz, T. and Hülser, T. and Barcikowski, S. and Brodmann, M.
    Proceedings of WHEC 2022 - 23rd World Hydrogen Energy Conference: Bridging Continents by H2 204-206 (2022)
  • 2022 • 827 In situ reactive coating of porous filtration membranes with functional polymer layers to integrate boron adsorber property
    Ke, Q. and Ulbricht, M.
    Journal of Membrane Science 660 (2022)
    The state-of-the-art reverse osmosis membranes for seawater desalination have limited competence to efficiently remove boron. One promising approach for boron removal is to integrate membrane-based separation with selective adsorption of boron in pre- or posttreatment of seawater desalination; the porous support layer of established filtration membranes, constituting the largest part of total membrane volume shall be utilized for this function. Therefore, this study focuses on performing in situ modification of commercial polyethersulfone (PES) microfiltration membranes toward reactive coating the pore surface with a boron affinity polymer-based hydrogel. Modification is carried out in two steps: 1) adsorption of an amphiphilic copolymer which contains tertiary amine groups as co-initiator for surface-selective free radical generation; 2) grafting of a hydrogel layer by using a monomer solution comprising polyol-containing monomer as boron ligand, a cross-linker monomer, and the redox initiator ammonium persulfate (APS). The entire modification process is performed under flow-through conditions. Membranes with different pore sizes were modified; modification parameters, such as molar mass of macromolecular co-initiator as well as composition of reactive monomer solution, were systematically varied. It was found that using an “integrated” initiation system with low molecular weight co-initiator N,N,N′,N′-tetraethyl ethylenediamine (TEMED) added to the reactive solution, yielded significantly higher degree of grafting and therefore superior adsorber properties. Boron binding capacity of modified membranes was evaluated in terms of boron adsorption isotherms, adsorption kinetics, break-through behavior under filtration conditions and regeneration of the adsorber. The trade-off between permeance and boron binding capacity of modified membrane was studied in order to identify promising materials with competitive overall separation performance, i.e. high permeance at a specific filter cut-off in combination with high boron binding capacity. © 2022 Elsevier B.V.
    view abstractdoi: 10.1016/j.memsci.2022.120851
  • 2022 • 826 OPTIMIZING THE ACID RESISTANCE OF CONCRETE WITH GRANULATED BLAST-FURNACE SLAG
    Kempf, L.-A. and Breitenbücher, R. and Gerten, C. and Ehrenberg, A.
    Acta Polytechnica CTU Proceedings 33 295-299 (2022)
    doi: 10.14311/APP.2022.33.0295
  • 2022 • 825 X-ray Absorption Near-Edge Structure (XANES) at the O K-Edge of Bulk Co3 O4: Experimental and Theoretical Studies
    Kenmoe, S. and Douma, D.H. and Raji, A.T. and M’passi-Mabiala, B. and Götsch, T. and Girgsdies, F. and Knop-Gericke, A. and Schlögl, R. and Spohr, E.
    Nanomaterials 12 (2022)
    We combine theoretical and experimental X-ray absorption near-edge spectroscopy (XANES) to probe the local environment around cationic sites of bulk spinel cobalt tetraoxide (Co3 O4 ). Specifically, we analyse the oxygen K-edge spectrum. We find an excellent agreement between our calculated spectra based on the density functional theory and the projector augmented wave method, previous calculations as well as with the experiment. The oxygen K-edge spectrum shows a strong pre-edge peak which can be ascribed to dipole transitions from O 1s to O 2p states hybridized with the unoccupied 3d states of cobalt atoms. Also, since Co3 O4 contains two types of Co atoms, i.e., Co3+ and Co2+, we find that contribution of Co2+ ions to the pre-edge peak is solely due to single spin-polarized t2g orbitals (dxz, dyz, and dxy ) while that of Co3+ ions is due to spin-up and spin-down polarized eg orbitals (dx2 −y2 andd z2 ). Furthermore, we deduce the magnetic moments on the Co3+ and Co2+ to be zero and 3.00 µB respectively. This is consistent with an earlier experimental study which found that the magnetic structure of Co3 O4 consists of antiferromagnetically ordered Co2+ spins, each of which is surrounded by four nearest neighbours of oppositely directed spins. © 2022 by the authors. Licensee MDPI, Basel, Switzerland.
    view abstractdoi: 10.3390/nano12060921
  • 2022 • 824 Make or break: The thermodynamic equilibrium of polyphosphate kinase-catalysed reactions
    Keppler, M. and Moser, S. and Jessen, H.J. and Held, C. and Andexer, J.N.
    Beilstein Journal of Organic Chemistry 18 1278-1288 (2022)
    doi: 10.3762/bjoc.18.134
  • 2022 • 823 Scaling and Confinement in Ultrathin Chalcogenide Films as Exemplified by GeTe
    Kerres, P. and Zhou, Y. and Vaishnav, H. and Raghuwanshi, M. and Wang, J. and Häser, M. and Pohlmann, M. and Cheng, Y. and Schön, C.-F. and Jansen, T. and Bellin, C. and Bürgler, D.E. and Jalil, A.R. and Ringkamp, C. and Kowalc...
    Small 18 (2022)
    Chalcogenides such as GeTe, PbTe, Sb2Te3, and Bi2Se3 are characterized by an unconventional combination of properties enabling a plethora of applications ranging from thermo-electrics to phase change materials, topological insulators, and photonic switches. Chalcogenides possess pronounced optical absorption, relatively low effective masses, reasonably high electron mobilities, soft bonds, large bond polarizabilities, and low thermal conductivities. These remarkable characteristics are linked to an unconventional bonding mechanism characterized by a competition between electron delocalization and electron localization. Confinement, that is, the reduction of the sample dimension as realized in thin films should alter this competition and modify chemical bonds and the resulting properties. Here, pronounced changes of optical and vibrational properties are demonstrated for crystalline films of GeTe, while amorphous films of GeTe show no similar thickness dependence. For crystalline films, this thickness dependence persists up to remarkably large thicknesses above 15 nm. X-ray diffraction and accompanying simulations employing density functional theory relate these changes to thickness dependent structural (Peierls) distortions, due to an increased electron localization between adjacent atoms upon reducing the film thickness. A thickness dependence and hence potential to modify film properties for all chalcogenide films with a similar bonding mechanism is expected. © 2022 The Authors. Small published by Wiley-VCH GmbH.
    view abstractdoi: 10.1002/smll.202201753
  • 2022 • 822 Innovative Online Measurement and Modelling Approach for Property-Controlled Flow Forming Processes
    Kersting, L. and Arian, B. and Vasquez, J.R. and Trächtler, A. and Homberg, W. and Walther, F.
    Key Engineering Materials 926 KEM 862-874 (2022)
    The production of complex multi-functional, high-strength parts is becoming increasingly important in the industry. Especially with small batch size, the incremental flow forming processes can be advantageous. The production of parts with complex geometry and locally graded material properties currently depicts a great challenge in the flow forming process. At this point, the usage of closed-loop control for the shape and properties could be a feasible new solution. The overall aim in this project is to establish an intelligent closed-loop control system for the wall thickness as well as the α’-martensite content of AISI 304L-workpieces in a flow forming process. To reach this goal, a novel sensor concept for online measurements of the wall thickness reduction and the martensite content during forming process is proposed. It includes the setup of a modified flow forming machine and the integration of the sensor system in the machine control. Additionally, a simulation model for the flow forming process is presented which describes the forming process with regard to the plastic workpiece deformation, the induced α’-martensite fraction, and the sensor behavior. This model was used for designing a closed-loop process control of the wall thickness reduction that was subsequently realized at the real plant including online measured feedback from the sensor system. © 2022 The Author(s). Published by Trans Tech Publications Ltd, Switzerland.
    view abstractdoi: 10.4028/p-yp2hj3
  • 2022 • 821 Macroscopic simulation model for laser cutting of carbon fibre reinforced plastics
    Keuntje, J. and Mrzljak, S. and Gerdes, L. and Wippo, V. and Kaierle, S. and Overmeyer, L. and Walther, F. and Jaeschke, P.
    Procedia CIRP 111 496-500 (2022)
    doi: 10.1016/j.procir.2022.08.078
  • 2022 • 820 Domain Wall Acceleration by Ultrafast Field Application: An Ab Initio-Based Molecular Dynamics Study
    Khachaturyan, R. and Dimou, A. and Grünebohm, A.
    Physica Status Solidi - Rapid Research Letters 16 (2022)
    doi: 10.1002/pssr.202200038
  • 2022 • 819 Exploring MgO/HA ceramic nano-composites for biodegradable implants: Exploring biological properties and micromechanics
    Khalili, V. and Sengstock, C. and Kalchev, Y. and Pfetzing-Micklich, J. and Frenzel, J.
    Surface and Coatings Technology 445 (2022)
    doi: 10.1016/j.surfcoat.2022.128730
  • 2022 • 818 Localised Muscle Contraction Predictor for Steering Wheel Operation in Simulated Condition
    Khamis, N.K. and Schramm, D. and Sabri, M.A.M. and Khalid, M.S.A.
    Lecture Notes in Electrical Engineering 730 647-657 (2022)
    Evaluation of the steering wheel control is important to optimise the posture of the driver. The purpose of this study was to determine the relationship between muscle contraction at the shoulder and anthropometric variables when performing steering wheel task. Participants were recruited to perform multiple steering wheel actions. The surface electromyogram (SEMG) evaluation and anthropometric parameter measurement of individuals were recorded simultaneously during the experiment. For the statistical analysis, the anthropometric parameter was selected as an independent variable, while muscle activity based on SEMG measurement was chosen as the dependent variable. The results reveal that the left deltoid muscle showed the highest contraction at the right turn with high degree of turning. The SEMG and anthropometric data were positively correlated, and the predictive model shows the validity of the proposed model with the R2 value nearly 0.50. This finding recommends that driver’s anthropometric parameter may provide a good reference in a real driving task for controlling the steering wheel. Thus, some of potential utilization from this research is the optimizing in changing the vehicle design for allowing an independent adjustment to the relative distance between the driver seat and the steering wheel. © 2022, The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd.
    view abstractdoi: 10.1007/978-981-33-4597-3_58
  • 2022 • 817 Existence and uniqueness of Rayleigh waves in isotropic elastic Cosserat materials and algorithmic aspects
    Khan, H. and Ghiba, I.-D. and Madeo, A. and Neff, P.
    Wave Motion 110 (2022)
    We discuss the propagation of surface waves in an isotropic half space modelled with the linear Cosserat theory of isotropic elastic materials. To this aim we use a method based on the algebraic analysis of the surface impedance matrix and on the algebraic Riccati equation, and which is independent of the common Stroh formalism. Due to this method, a new algorithm which determines the amplitudes and the wave speed in the theory of isotropic elastic Cosserat materials is described. Moreover, this method allows us to prove the existence and uniqueness of a subsonic solution of the secular equation, a problem which remains unsolved in almost all generalized linear theories of elastic materials. Since the results are suitable to be used for numerical implementations, we propose two numerical algorithms which are viable for any elastic material. Explicit numerical calculations are made for aluminium-epoxy in the context of the Cosserat model. Since the novel form of the secular equation for isotropic elastic material has not been explicitly derived elsewhere, we establish it in this paper, too. © 2022 Elsevier B.V.
    view abstractdoi: 10.1016/j.wavemoti.2022.102898
  • 2022 • 816 Laser-equipped gas reaction chamber for probing environmentally sensitive materials at near atomic scale
    Khanchandani, H. and El-Zoka, A.A. and Kim, S.-H. and Tezins, U. and Vogel, D. and Sturm, A. and Raabe, D. and Gault, B. and Stephenson, L.T.
    PLoS ONE 17 (2022)
    Numerous metallurgical and materials science applications depend on quantitative atomic-scale characterizations of environmentally-sensitive materials and their transient states. Studying the effect upon materials subjected to thermochemical treatments in specific gaseous atmospheres is of central importance for specifically studying a material’s resistance to certain oxidative or hydrogen environments. It is also important for investigating catalytic materials, direct reduction of an oxide, particular surface science reactions or nanoparticle fabrication routes. This manuscript realizes such experimental protocols upon a thermochemical reaction chamber called the "Reacthub" and allows for transferring treated materials under cryogenic &amp; ultrahigh vacuum (UHV) workflow conditions for characterisation by either atom probe or scanning Xe+/electron microscopies. Two examples are discussed in the present study. One protocol was in the deuterium gas charging (25 kPa D2 at 200°C) of a high-manganese twinning-induced-plasticity (TWIP) steel and characterization of the ingress and trapping of hydrogen at various features (grain boundaries in particular) in efforts to relate this to the steel’s hydrogen embrittlement susceptibility. Deuterium was successfully detected after gas charging but most contrast originated from the complex ion FeOD+ signal and the feature may be an artefact. The second example considered the direct deuterium reduction (5 kPa D2 at 700°C) of a single crystal wüstite (FeO) sample, demonstrating that under a standard thermochemical treatment causes rapid reduction upon the nanoscale. In each case, further studies are required for complete confidence about these phenomena, but these experiments successfully demonstrate that how an ex-situ thermochemical treatment can be realised that captures environmentally-sensitive transient states that can be analysed by atomic-scale by atom probe microscope. © 2022 Khanchandani et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
    view abstractdoi: 10.1371/journal.pone.0262543
  • 2022 • 815 Reassessment of mobility parameters for Cantor High Entropy Alloys through an automated procedure
    Khorasgani, A.R. and Kundin, J. and Divinski, S.V. and Steinbach, I.
    Calphad: Computer Coupling of Phase Diagrams and Thermochemistry 79 (2022)
    An automated assessment procedure is performed in order to establish a sophisticated kinetic data bank, introduced and modified by applying consequential iteration steps through the cross-validation method. The nonlinear curve-fitting of the end-member parameters is replaced by a simple linear fitting function via the logarithmic form of the Arrhenius equation. The applied modifications allow us to increase the precision of the method by decreasing the fitting errors. The input data employed here are the tracer diffusion coefficients in the well investigated high entropy alloy Co–Cr–Fe–Mn–Ni. The resulting parameters are in an acceptable agreement with the previously defined parameters in the literature while providing an efficient robust tool for kinetic data base development so that it enable an adequate prediction of diffusion transport. © 2022 Elsevier Ltd
    view abstractdoi: 10.1016/j.calphad.2022.102498
  • 2022 • 814 Accumulation and control of spin waves in magnonic dielectric microresonators by a comb of ultrashort laser pulses
    Khramova, A.E. and Kobecki, M. and Akimov, I.A. and Savochkin, I.V. and Kozhaev, M.A. and Shaposhnikov, A.N. and Berzhansky, V.N. and Zvezdin, A.K. and Bayer, M. and Belotelov, V.I.
    Scientific Reports 12 (2022)
    doi: 10.1038/s41598-022-07784-2
  • 2022 • 813 Active Buffer Matrix in Nanoparticle-Based Silicon-Rich Silicon Nitride Anodes Enables High Stability and Fast Charging of Lithium-Ion Batteries
    Kilian, S.O. and Wankmiller, B. and Sybrecht, A.M. and Twellmann, J. and Hansen, M.R. and Wiggers, H.
    Advanced Materials Interfaces 9 (2022)
    A very promising way to improve the stability of silicon in lithium-ion battery (LIB) anodes is the use of nanostructured silicon-rich silicon nitride (SiNx), known as a conversion-type anode material. To investigate the conversion mechanism in this material in detail, SiN0.5 nanoparticles are synthesized and examined as LIB anodes using a combination of ex situ X-ray photoelectron spectroscopy and solid-state 7Li MAS NMR measurements. During the initial cycle, the conversion of SiN0.5 nanoparticles results in the formation of lithium silicides and a buffer matrix consisting of different lithium nitridosilicates and lithium nitride. These phases can be reversibly lithiated and contribute to the total reversible capacity of the silicon nitride active material. The structure of the material after conversion is best described by an amorphous solid solution. Further, it is shown that silicon-rich silicon nitrides possess improved rate capability because of the higher ionic conductivity of the buffer matrix compared to pure silicon, and very fine dispersion of silicon clusters throughout the buffer matrix. Thus, unlike most conversion materials, the silicon-rich silicon nitride exhibits an additional intrinsic active functionality of the buffer matrix that goes far beyond the mere reduction of electrolyte contact area and volume expansion. © 2022 The Authors. Advanced Materials Interfaces published by Wiley-VCH GmbH.
    view abstractdoi: 10.1002/admi.202201389
  • 2022 • 812 Understanding Alkali Contamination in Colloidal Nanomaterials to Unlock Grain Boundary Impurity Engineering
    Kim, S.-H. and Yoo, S.-H. and Chakraborty, P. and Jeong, J. and Lim, J. and El-Zoka, A.A. and Zhou, X. and Stephenson, L.T. and Hickel, T. and Neugebauer, J. and Scheu, C. and Todorova, M. and Gault, B.
    Journal of the American Chemical Society 144 987-994 (2022)
    Metal nanogels combine a large surface area, a high structural stability, and a high catalytic activity toward a variety of chemical reactions. Their performance is underpinned by the atomic-level distribution of their constituents, yet analyzing their subnanoscale structure and composition to guide property optimization remains extremely challenging. Here, we synthesized Pd nanogels using a conventional wet chemistry route, and a near-atomic-scale analysis reveals that impurities from the reactants (Na and K) are integrated into the grain boundaries of the poly crystalline gel, typically loci of high catalytic activity. We demonstrate that the level of impurities is controlled by the reaction condition. Based on ab initio calculations, we provide a detailed mechanism to explain how surface-bound impurities become trapped at grain boundaries that form as the particles coalesce during synthesis, possibly facilitating their decohesion. If controlled, impurity integration into grain boundaries may offer opportunities for designing new nanogels. © 2022 The Authors. Published by American Chemical Society
    view abstractdoi: 10.1021/jacs.1c11680
  • 2022 • 811 Controlled Doping of Electrocatalysts through Engineering Impurities
    Kim, S.-H. and Yoo, S.-H. and Shin, S. and El-Zoka, A.A. and Kasian, O. and Lim, J. and Jeong, J. and Scheu, C. and Neugebauer, J. and Lee, H. and Todorova, M. and Gault, B.
    Advanced Materials 34 (2022)
    Fuel cells recombine water from H2 and O2 thereby can power, for example, cars or houses with no direct carbon emission. In anion-exchange membrane fuel cells (AEMFCs), to reach high power densities, operating at high pH is an alternative to using large volumes of noble metals catalysts at the cathode, where the oxygen-reduction reaction occurs. However, the sluggish kinetics of the hydrogen-oxidation reaction (HOR) hinders upscaling despite promising catalysts. Here, the authors observe an unexpected ingress of B into Pd nanocatalysts synthesized by wet-chemistry, gaining control over this B-doping, and report on its influence on the HOR activity in alkaline conditions. They rationalize their findings using ab initio calculations of both H- and OH-adsorption on B-doped Pd. Using this “impurity engineering” approach, they thus design Pt-free catalysts as required in electrochemical energy conversion devices, for example, next generations of AEMFCs, that satisfy the economic and environmental constraints, that is, reasonable operating costs and long-term stability, to enable the “hydrogen economy.”. © 2022 The Authors. Advanced Materials published by Wiley-VCH GmbH.
    view abstractdoi: 10.1002/adma.202203030
  • 2022 • 810 Understanding the Degradation of a Model Si Anode in a Li-Ion Battery at the Atomic Scale
    Kim, S.-H. and Dong, K. and Zhao, H. and El-Zoka, A.A. and Zhou, X. and Woods, E.V. and Giuliani, F. and Manke, I. and Raabe, D. and Gault, B.
    Journal of Physical Chemistry Letters 13 8416-8421 (2022)
    To advance the understanding of the degradation of the liquid electrolyte and Si electrode, and their interface, we exploit the latest developments in cryo-atom probe tomography. We evidence Si anode corrosion from the decomposition of the Li salt before charge-discharge cycles even begin. Volume shrinkage during delithiation leads to the development of nanograins from recrystallization in regions left amorphous by the lithiation. The newly created grain boundaries facilitate pulverization of nanoscale Si fragments, and one is found floating in the electrolyte. P is segregated to these grain boundaries, which confirms the decomposition of the electrolyte. As structural defects are bound to assist the nucleation of Li-rich phases in subsequent lithiations and accelerate the electrolyte's decomposition, these insights into the developed nanoscale microstructure interacting with the electrolyte contribute to understanding the self-catalyzed/accelerated degradation Si anodes and can inform new battery designs unaffected by these life-limiting factors. © 2022 American Chemical Society.
    view abstractdoi: 10.1021/acs.jpclett.2c02236
  • 2022 • 809 Efficient indoor light harvesting with CH3NH3Pb(I0.8Br0.2)3 solar modules and sodium-ion battery
    Kin, L.-C. and Liu, Z. and Astakhov, O. and Shcherbachenko, S. and Kungl, H. and Kirchartz, T. and Eichel, R.-A. and Rau, U. and Merdzhanova, T.
    Cell Reports Physical Science 3 (2022)
    doi: 10.1016/j.xcrp.2022.101123
  • 2022 • 808 Characterization of the deformation behavior and the contact situation: Superfinishing with diamond-coated foams [Feinstbearbeitung mit diamantbelegten Schaumstoffen]
    Kipp, M. and Biermann, D.
    VDI-Z Integrierte Produktion 164 28-30 (2022)
  • 2022 • 807 Cementite decomposition in 100Cr6 bearing steel during high-pressure torsion: Influence of precipitate composition, size, morphology and matrix hardness
    Kiranbabu, S. and Tung, P.-Y. and Sreekala, L. and Prithiv, T.S. and Hickel, T. and Pippan, R. and Morsdorf, L. and Herbig, M.
    Materials Science and Engineering A 833 (2022)
    Premature failure of rail and bearing steels by White-Etching-Cracks leads to severe economic losses. This failure mechanism is associated with microstructure decomposition via local severe plastic deformation. The decomposition of cementite plays a key role. Due to the high hardness of this phase, it is the most difficult obstacle to overcome in the decaying microstructure. Understanding the mechanisms of carbide decomposition is essential for designing damage-resistant steels for industrial applications. We investigate cementite decomposition in the bearing steel 100Cr6 (AISI 52100) upon exposure to high-pressure torsion (maximum shear strain, Ƴmax = 50.2). Following-up on our earlier work on cementite decomposition in hardened 100Cr6 steel (Qin et al., Act. Mater. 2020 [1]), we now apply a modified heat treatment to generate a soft-annealed microstructure where spherical and lamellar cementite precipitates are embedded in a ferritic matrix. These two precipitate types differ in morphology (spherical vs. lamellar), size (spherical: 100–1000 nm diameter, lamellar: 40–100 nm thickness) and composition (Cr and Mn partitioning). We unravel the correlation between cementite type and its resistance to decomposition using multi-scale chemical and structural characterization techniques. Upon high-pressure torsion, the spherical cementite precipitates did not decompose, but the larger spherical precipitates (≥ 1 μm) deformed. In contrast, the lamellar cementite precipitates underwent thinning followed by decomposition and dissolution. Moreover, the decomposition behavior of cementite precipitates is affected by the type of matrix microstructure. We conclude that the cementite size and morphology, as well as the matrix mechanical properties are the predominating factors influencing the decomposition behavior of cementite. The compositional effects of Cr and Mn on cementite stability calculated by complementary density functional theory (DFT) calculations are minor in the current scenario. © 2021 Elsevier B.V.
    view abstractdoi: 10.1016/j.msea.2021.142372
  • 2022 • 806 Picturing charge carrier diffusion
    Kirchartz, T.
    Nature Materials 21 1344-1345 (2022)
    doi: 10.1038/s41563-022-01389-w
  • 2022 • 805 Metamodel-based optimization of shift planning in high-bay warehouse operations
    Kirchhoff, D. and Kirberg, M. and Kuhnt, S. and Clausen, U.
    Quality and Reliability Engineering International (2022)
    Gaussian process (GP) models of time-consuming computer simulations are nowadays widely used within metamodel-based optimization. In recent years, GP models with mixed inputs have been proposed to handle both numerical and categorical inputs. Using a case study of a high-bay warehouse, we demonstrate the use of GP models with low-rank correlation (LRC) kernels in the context of efficient global optimization (EGO). As is common in many logistics applications, the high-bay warehouse is modeled with a discrete-event simulation model. Input variables include, for example, the choice between different task assignment strategies. A shift scheduling problem is considered in which personnel and energy costs as well as the delay of tasks are to be minimized at the same time. Evaluations of an initial experimental design provide a first approximation of the Pareto front, which we manage to extend substantially within only 15 iterations of identifying new points using the expected hypervolume improvement (EHI) and the S metric selection (SMS) criteria. We penalize the criteria in the last five iterations using the known total costs of proposed points to guide the search towards a more desired area. The resulting Pareto front approximation provides a selection of shift plans that have different characteristics. This enables decision makers in practice to choose a shift plan with desirable features. © 2022 The Authors. Quality and Reliability Engineering International published by John Wiley & Sons Ltd.
    view abstractdoi: 10.1002/qre.3207
  • 2022 • 804 Lead-Dominated Hyperfine Interaction Impacting the Carrier Spin Dynamics in Halide Perovskites
    Kirstein, E. and Yakovlev, D.R. and Glazov, M.M. and Evers, E. and Zhukov, E.A. and Belykh, V.V. and Kopteva, N.E. and Kudlacik, D. and Nazarenko, O. and Dirin, D.N. and Kovalenko, M.V. and Bayer, M.
    Advanced Materials 34 (2022)
    The outstanding optical quality of lead halide perovskites inspires studies of their potential for the optical control of carrier spins as pursued in other materials. Entering largely uncharted territory, time-resolved pump–probe Kerr rotation is used to explore the coherent spin dynamics of electrons and holes in bulk formamidinium caesium lead iodine bromide (FA0.9Cs0.1PbI2.8Br0.2) and to determine key parameters characterizing interactions of their spins, such as the g-factors and relaxation times. The demonstrated long spin dynamics and narrow g-factor distribution prove the perovskites as promising competitors for conventional semiconductors in spintronics. The dynamic nuclear polarization via spin-oriented holes is realized and the identification of the lead (207Pb) isotope in optically detected nuclear magnetic resonance proves that the hole–nuclei interaction is dominated by the lead ions. A detailed theoretical analysis accounting for the specifics of the lead halide perovskite materials allows the evaluation of the underlying hyperfine interaction constants, both for electrons and holes. Recombination and spin dynamics evidence that at low temperatures, photogenerated electrons and holes are localized at different regions of the perovskite crystal, resulting in their long lifetimes up to 44 μs. The findings form the base for the tailored development of spin-optoelectronic applications for the large family of lead halide perovskites and their nanostructures. © 2021 The Authors. Advanced Materials published by Wiley-VCH GmbH
    view abstractdoi: 10.1002/adma.202105263
  • 2022 • 803 The Landé factors of electrons and holes in lead halide perovskites: universal dependence on the band gap
    Kirstein, E. and Yakovlev, D.R. and Glazov, M.M. and Zhukov, E.A. and Kudlacik, D. and Kalitukha, I.V. and Sapega, V.F. and Dimitriev, G.S. and Semina, M.A. and Nestoklon, M.O. and Ivchenko, E.L. and Kopteva, N.E. and Dirin, D.N. ...
    Nature Communications 13 (2022)
    doi: 10.1038/s41467-022-30701-0
  • 2022 • 802 Spin Dynamics of Electrons and Holes Interacting with Nuclei in MAPbI3Perovskite Single Crystals
    Kirstein, E. and Yakovlev, D.R. and Zhukov, E.A. and Höcker, J. and Dyakonov, V. and Bayer, M.
    ACS Photonics 9 1375-1384 (2022)
    doi: 10.1021/acsphotonics.2c00096
  • 2022 • 801 Adaptive and Frugal FETI-DP for Virtual Elements
    Klawonn, A. and Lanser, M. and Wasiak, A.
    Vietnam Journal of Mathematics (2022)
    The FETI-DP (Finite Element Tearing and Interconnecting - Dual Primal) method has recently successfully been applied to virtual element discretizations, adding more flexibility to the resolution of possibly complicated underlying domain geometries. However, for second-order partial differential equations with large discontinuities in the coefficient functions, in general, the convergence rate of domain decomposition methods is known to deteriorate if the coarse space is not properly adjusted. For finite element discretizations, this problem can be solved by using adaptive coarse spaces, which guarantee a robust method for arbitrary coefficient distributions, or by the computationally much cheaper frugal coarse space, which numerically proved to be robust for many realistic coefficient distributions. In this article, both, the adaptive and the frugal FETI-DP methods are applied to discretizations obtained by using virtual elements. As model problems, stationary diffusion and compressible linear elasticity in two spatial dimensions are considered. The performance of the methods is numerically tested, varying the quasi-uniformity of the underlying meshes, the polynomial degree, the scaling method, and considering regular and irregular domain decompositions. It is shown that adaptive and frugal FETI-DP for virtual elements behave similarly as in the finite element case. © 2022, The Author(s).
    view abstractdoi: 10.1007/s10013-022-00580-5
  • 2022 • 800 Adaptive Nonlinear Elimination in Nonlinear FETI-DP Methods
    Klawonn, A. and Lanser, M. and Uran, M.
    Lecture Notes in Computational Science and Engineering 145 337-345 (2022)
    doi: 10.1007/978-3-030-95025-5_35
  • 2022 • 799 Polyconvex anisotropic hyperelasticity with neural networks
    Klein, D.K. and Fernández, M. and Martin, R.J. and Neff, P. and Weeger, O.
    Journal of the Mechanics and Physics of Solids 159 (2022)
    In the present work, two machine learning based constitutive models for finite deformations are proposed. Using input convex neural networks, the models are hyperelastic, anisotropic and fulfill the polyconvexity condition, which implies ellipticity and thus ensures material stability. The first constitutive model is based on a set of polyconvex, anisotropic and objective invariants. The second approach is formulated in terms of the deformation gradient, its cofactor and determinant, uses group symmetrization to fulfill the material symmetry condition, and data augmentation to fulfill objectivity approximately. The extension of the dataset for the data augmentation approach is based on mechanical considerations and does not require additional experimental or simulation data. The models are calibrated with highly challenging simulation data of cubic lattice metamaterials, including finite deformations and lattice instabilities. A moderate amount of calibration data is used, based on deformations which are commonly applied in experimental investigations. While the invariant-based model shows drawbacks for several deformation modes, the model based on the deformation gradient alone is able to reproduce and predict the effective material behavior very well and exhibits excellent generalization capabilities. In addition, the models are calibrated with transversely isotropic data, generated with an analytical polyconvex potential. For this case, both models show excellent results, demonstrating the straightforward applicability of the polyconvex neural network constitutive models to other symmetry groups. © 2021 Elsevier Ltd
    view abstractdoi: 10.1016/j.jmps.2021.104703
  • 2022 • 798 Monitoring Catalytic 2-Propanol Oxidation over Co3O4Nanowires via in Situ Photoluminescence Spectroscopy
    Klein, J. and Kampermann, L. and Korte, J. and Dreyer, M. and Budiyanto, E. and Tüysüz, H. and Ortega, K.F. and Behrens, M. and Bacher, G.
    Journal of Physical Chemistry Letters 13 3217-3223 (2022)
    doi: 10.1021/acs.jpclett.2c00098
  • 2022 • 797 Covalent Attachment of Aggregation-Induced Emission Molecules to the Surface of Ultrasmall Gold Nanoparticles to Enhance Cell Penetration
    Klein, K. and Hayduk, M. and Kollenda, S. and Schmiedtchen, M. and Voskuhl, J. and Epple, M.
    Molecules 27 (2022)
    doi: 10.3390/molecules27061788
  • 2022 • 796 Development and validation of models for turbulent reacting flows
    Klein, M. and Chakraborty, N. and Kempf, A. and Sadiki, A.
    Physics of Fluids 34 (2022)
    doi: 10.1063/5.0137795
  • 2022 • 795 Pushing the Limits in Real-Time Measurements of Quantum Dynamics
    Kleinherbers, E. and Stegmann, P. and Kurzmann, A. and Geller, M. and Lorke, A. and König, J.
    Physical Review Letters 128 (2022)
    Time-resolved studies of quantum systems are the key to understanding quantum dynamics at its core. The real-time measurement of individual quantum numbers as they switch between certain discrete values, well known as a "random telegraph signal,"is expected to yield maximal physical insight. However, the signal suffers from both systematic errors, such as a limited time resolution and noise from the measurement apparatus, as well as statistical errors due to a limited amount of data. Here we demonstrate that an evaluation scheme based on factorial cumulants can reduce the influence of such errors by orders of magnitude. The error resilience is supported by a general theory for the detection errors as well as experimental data of single-electron tunneling through a self-assembled quantum dot. Thus, factorial cumulants push the limits in the analysis of random telegraph data, which represent a wide class of experiments in physics, chemistry, engineering, and life sciences. © 2022 American Physical Society.
    view abstractdoi: 10.1103/PhysRevLett.128.087701
  • 2022 • 794 Nuclear-spin polaron formation: Anisotropy effects and quantum phase transition
    Kleinjohann, I. and Fischer, A. and Glazov, M.M. and Anders, F.B.
    Physical Review B 105 (2022)
    doi: 10.1103/PhysRevB.105.195309
  • 2022 • 793 Selective hydrogenation of highly concentrated acetylene streams over mechanochemically synthesized PdAg supported catalysts
    Kley, K.S. and De Bellis, J. and Schüth, F.
    Catalysis Science and Technology 13 119-131 (2022)
    doi: 10.1039/d2cy01424f
  • 2022 • 792 Validation of the smooth step model by particle-in-cell/Monte Carlo collisions simulations
    Klich, M. and Löwer, J. and Wilczek, S. and Mussenbrock, T. and Brinkmann, R.P.
    Plasma Sources Science and Technology 31 (2022)
    Bounded plasmas are characterized by a rapid but smooth transition from quasi-neutrality in the volume to electron depletion close to the electrodes and chamber walls. The thin non-neutral region, the boundary sheath, comprises only a small fraction of the discharge domain but controls much of its macroscopic behavior. Insights into the properties of the sheath and its relation to the plasma are of high practical and theoretical interest. The recently proposed smooth step model (SSM) provides a closed analytical expression for the electric field in a planar, radio-frequency modulated sheath. It represents (i) the space charge field in the depletion zone, (ii) the generalized Ohmic and ambipolar field in the quasi-neutral zone, and (iii) a smooth interpolation for the transition in between. This investigation compares the SSM with the predictions of a more fundamental particle-in-cell/Monte Carlo collisions simulation and finds good quantitative agreement when the assumed length and time scale requirements are met. A second simulation case illustrates that the model remains applicable even when the assumptions are only marginally fulfilled. © 2022 The Author(s). Published by IOP Publishing Ltd.
    view abstractdoi: 10.1088/1361-6595/ac5dd3
  • 2022 • 791 Thermal stability of nanoscale ferroelectric domains by molecular dynamics modeling
    Klomp, A.J. and Khachaturyan, R. and Wallis, T. and Albe, K. and Grünebohm, A.
    Physical Review Materials 6 (2022)
    doi: 10.1103/PhysRevMaterials.6.104411
  • 2022 • 790 Transverse magnetic routing of light emission in hybrid plasmonic-semiconductor nanostructures: Towards operation at room temperature
    Klompmaker, L. and Poddubny, A.N. and Yalcin, E. and Litvin, L.V. and Jede, R. and Karczewski, G. and Chusnutdinow, S. and Wojtowicz, T. and Yakovlev, D.R. and Bayer, M. and Akimov, I.A.
    Physical Review Research 4 (2022)
    We study experimentally and theoretically the temperature dependence of transverse magnetic routing of light emission from hybrid plasmonic-semiconductor quantum well structures where the exciton emission from the quantum well is routed into surface plasmon polaritons propagating along a nearby semiconductor-metal interface. In II-VI and III-V direct-band semiconductors the magnitude of routing is governed by the circular polarization of exciton optical transitions, that is induced by a magnetic field. For structures comprising a (Cd,Mn)Te/(Cd,Mg)Te diluted magnetic semiconductor quantum well we observe a strong directionality of the emission up to 15% at low temperature of 20K and magnetic field of 485mT due to giant Zeeman splitting of holes mediated via the strong exchange interaction with Mn2+ ions. For increasing temperatures towards room temperature the magnetic susceptibility decreases and the directionality strongly drops to 4% at about 65 K. We also propose an alternative design based on a nonmagnetic (In,Ga)As/(In,Al)As quantum well structure, suitable for higher temperatures. According to our calculations, such structure can demonstrate emission directionality up to 5% for temperatures below 200 K and moderate magnetic fields of 1 T. © 2022 authors. Published by the American Physical Society.
    view abstractdoi: 10.1103/PhysRevResearch.4.013058
  • 2022 • 789 Channel Sounding Measurements for 5G Campus Networks in Industrial Environments
    Knitter, M. and Kays, R.
    2022 32nd International Telecommunication Networks and Applications Conference, ITNAC 2022 96-101 (2022)
    doi: 10.1109/ITNAC55475.2022.9998355
  • 2022 • 788 Spatial Reuse Insights for IEEE 802.11ax and IEEE 802.11be Wireless LANs and beyond
    Knitter, M. and Kays, R.
    IEEE International Symposium on Personal, Indoor and Mobile Radio Communications, PIMRC 2022-September 919-925 (2022)
    doi: 10.1109/PIMRC54779.2022.9978080
  • 2022 • 787 Impact of enzymatically synthesized aliphatic–aromatic polyesters with increased hydroxyl group content on coating properties
    Knospe, P. and Seithümmer, J. and Reichmann, R. and Gutmann, J.S. and Hoffmann-Jacobsen, K. and Dornbusch, M.
    Journal of Coatings Technology and Research (2022)
    doi: 10.1007/s11998-022-00651-9
  • 2022 • 786 Experimental and kinetic modeling study of the positive ions in premixed ethylene flames over a range of equivalence ratios
    Knyazkov, D.A. and Cherepanov, A. and Kiselev, V.G. and Gerasimov, I.E. and Kasper, T. and Shmakov, A.G.
    Proceedings of the Combustion Institute (2022)
    Understanding the ion chemistry in flames is crucial for developing ion sensitive technologies for controlling combustion processes. In this work, we measured the spatial distributions of positive ions in atmospheric-pressure burner-stabilized premixed flames of ethylene/oxygen/argon mixtures in a wide range of equivalence ratios π = 0.4+1.5. A flame sampling molecular beam system coupled with a quadrupole mass spectrometer was used to obtain the spatial distributions of cations in the flames, and a high mass resolution time-of-flight mass spectrometer was utilized for the identification of the cations having similar m/z ratios. The measured profiles of the flame ions were corrected for the contribution of hydrates formed during sampling in the flames slightly upstream the flame reaction zone. We also proposed an updated ion chemistry model and verified it against the experimental profiles of the most abundant cations in the flames. Our model is based on the kinetic mechanism available in the literature extended with the reactions for C3H5+ cation. Highly accurate W2-F12 quantum chemical calculations were used to obtain a reliable formation enthalpy of C3H5+. The model was found to reproduce properly the measured relative abundance of the key oxygenated cations (viz., CH5O+, C2H3O+) in the whole range of equivalence ratios employed, and the C3H5+ cation abundance in the richest flame with π=1.5, but significantly underpredicts the relative mole fraction of C3H3+, which becomes a key species under fuel-rich conditions. Apart from this, several aromatic and cyclic CxHy cations dominating under fuel-rich conditions were identified. We also considered the most important directions for the further refinement of the mechanism. © 2022 Elsevier Inc. All rights reserved.
    view abstractdoi: 10.1016/j.proci.2022.07.157
  • 2022 • 785 Analysis of Dielectric Post-Wall Waveguide-based Passive Circuits using Recurrent Neural Network
    Kobakhidze, S. and Archemashvili, E. and Jandieri, V. and Yasumoto, K. and Maeda, H. and Hong, W. and Werner, D.H. and Erni, D.
    2022 16th European Conference on Antennas and Propagation, EuCAP 2022 (2022)
  • 2022 • 784 Giant Photoelasticity of Polaritons for Detection of Coherent Phonons in a Superlattice with Quantum Sensitivity
    Kobecki, M. and Scherbakov, A.V. and Kukhtaruk, S.M. and Yaremkevich, D.D. and Henksmeier, T. and Trapp, A. and Reuter, D. and Gusev, V.E. and Akimov, A.V. and Bayer, M.
    Physical Review Letters 128 (2022)
    doi: 10.1103/PhysRevLett.128.157401
  • 2022 • 783 Stress-Based Methods for Quasi-Variational Inequalities Associated with Frictional Contact
    Kober, B. and Starke, G. and Krause, R. and Rovi, G.
    International Series of Numerical Mathematics 172 445-466 (2022)
    The stress-based formulation of elastic contact with Coulomb friction in the form of a quasi-variational inequality is investigated. Weakly symmetric stress approximations are constructed using a finite element combination on the basis of Raviart–Thomas spaces of next-to-lowest order. An error estimator is derived based on a displacement reconstruction and proved to be reliable under certain assumptions on the solution formulated in terms of a norm equivalence in the trace space H1∕2(Γ). Numerical results illustrate the effectiveness of the adaptive refinement strategy for a Hertzian frictional contact problem in the compressible as well as in the incompressible case. © 2022, Springer Nature Switzerland AG.
    view abstractdoi: 10.1007/978-3-030-79393-7_18
  • 2022 • 782 Neural Network Potentials: A Concise Overview of Methods
    Kocer, E. and Ko, T.W. and Behler, J.
    Annual Review of Physical Chemistry 73 163-186 (2022)
    In the past two decades, machine learning potentials (MLPs) have reached a level of maturity that now enables applications to large-scale atomistic simulations of a wide range of systems in chemistry, physics, and materials science. Different machine learning algorithms have been used with great success in the construction of these MLPs. In this review, we discuss an important group of MLPs relying on artificial neural networks to establish a mapping from the atomic structure to the potential energy. In spite of this common feature, there are important conceptual differences among MLPs, which concern the dimensionality of the systems, the inclusion of long-range electrostatic interactions, global phenomena like nonlocal charge transfer, and the type of descriptor used to represent the atomic structure, which can be either predefined or learnable. A concise overview is given along with a discussion of the open challenges in the field. © 2022 Annual Reviews Inc.. All rights reserved.
    view abstractdoi: 10.1146/annurev-physchem-082720-034254
  • 2022 • 781 Process-Related Characterization of the Influence of the Die Design on the Microstructure and the Mechanical Properties of Profiles Made from Directly Recycled Hot Extruded EN AW-6060 Aluminum Chips
    Koch, A. and Laskowski, S. and Walther, F.
    Minerals, Metals and Materials Series 1021-1028 (2022)
    Solid-state-recycling processes for aluminum chips are promising alternatives to energy-intensive re-melting. In order to directly recycle aluminum chips without the necessity of re-melting, these are pre-compacted and further processed into profiles in a hot extrusion process. The quality of the so-produced profiles depends on the quality of the interface between the single chips, which are linked by microstructural welding. In order to enable a successful welding process, the pathways during the extrusion process have to be long enough in order to transfer enough energy and the encasing oxide layers have to be broken up successfully. Parameters like pressure, shear strain, and temperature influence the quality of the oxide layer breakup. Especially the shear strain can be varied by the material flow and the die. Therefore, this study examines the effects of different extrusion dies on the microstructure and the mechanical properties. The microstructure was characterized using metallographic investigations and could found to form within four different zones depending on the conditions during the extrusion process. The mechanical properties were investigated by means of tensile tests and fatigue tests and could be correlated well with the microstructure, since two different damage mechanisms depending on the specimen position can be distinguished. © 2022, The Minerals, Metals & Materials Society.
    view abstractdoi: 10.1007/978-3-030-92529-1_133
  • 2022 • 780 Chemical long range ordering in all-d-metal Heusler alloys
    Koch, D. and Beckmann, B. and Fortunato, N.M. and Miroshkina, O.N. and Gruner, M.E. and Zhang, H. and Gutfleisch, O. and Donner, W.
    Journal of Applied Physics 131 (2022)
    doi: 10.1063/5.0079952
  • 2022 • 779 Electrical Properties of the Base-Substrate Junction in Freestanding Core-Shell Nanowires
    Koch, J. and Liborius, L. and Kleinschmidt, P. and Weimann, N. and Prost, W. and Hannappel, T.
    Advanced Materials Interfaces 9 (2022)
    Well-defined hetero-interfaces with controlled properties are crucial for any high-performance, semiconductor-based, (opto-)electronic device. They are particularly important for device structures on the nanoscale with increased interfacial areas. Utilizing a ultrahigh-vacuum based multi-tip scanning tunneling microscope, this work reveals inadvertent conductivity channels between the nanowire (NW) base and the substrate, when measuring individual vertical core-shell III-V-semiconductor NWs. For that, four-terminal probing is applied on freestanding, epitaxially grown coaxial p-GaAs/i-GaInP/n-GaInP NWs without the need of nanoscale lithography or deposition of electrical contacts. This advanced analysis, carried out after composition-selective wet chemical etching, reveals a substantially degraded electrical performance of the freestanding NWs compared to detached ones. In an electron beam induced current mode of the nanosensor, charge separation at the substrate-to-NW base junction is demonstrated. An energy dispersive X-ray spectroscopic linescan shows an unintended compositional change of the epitaxially grown NW toward the planar layers caused by different incorporation mechanisms of Ga and In at the NW base. This approach provides direct insight into the NW-substrate transition area and leads to a model of the conductivity channels at the NW base, which should, in principle, be considered in the fabrication of all NW heterostructures grown bottom-up on heterogeneous substrate materials. © 2022 The Authors. Advanced Materials Interfaces published by Wiley-VCH GmbH.
    view abstractdoi: 10.1002/admi.202200948
  • 2022 • 778 Degradation and lifetime of self-healing thermal barrier coatings containing MoSi2 as self-healing particles in thermo-cycling testing
    Koch, D. and Mack, D.E. and Vaßen, R.
    Surface and Coatings Technology 437 (2022)
    Yttria-stabilized zirconia (YSZ) is the state-of-the-art top coat material for thermal barrier coatings (TBCs) applied on highly loaded gas turbine parts. During operation at high temperatures, stresses are induced by the thermal expansion coefficient mismatch between the ceramic TBC and the metallic substrate. As a consequence cracks can grow, propagate and finally lead to a spallation of the top coat. Using atmospheric plasma spraying (APS), so-called self-healing MoSi2 particles can be incorporated into the YSZ matrix to mitigate the propagation of cracks leading to a lifetime gain and possibly higher temperature capability of the TBC. In the present work, the healing process is realized by the oxidation of the self-healing particles, which introduces a volume expansion by a formation of reaction products, which can seal the cracks. The self-healing particles were introduced within the first 150 μm of the YSZ coating matrix immediately on top of the bond coat. The degradation and lifetime of such systems were studied in furnace cycling and in burner rig tests, in which a temperature gradient through the sample was applied. The lifetime of the self-healing coatings was then compared to the lifetime of an YSZ coating without self-healing particles. In burner rig tests a clear lifetime extension of the self-healing TBCs was observed. The origin of this different behavior was investigated by microstructural analysis in scanning electron microscopy. A further insight into the failure mechanisms was gained by the analysis of a self-healing TBC cycled in a furnace cycling test only for about 55% of its expected lifetime. © 2022 Elsevier B.V.
    view abstractdoi: 10.1016/j.surfcoat.2022.128353
  • 2022 • 777 Adaptive convexification of microsphere-based incremental damage for stress and strain softening at finite strains
    Köhler, M. and Neumeier, T. and Melchior, J. and Peter, M.A. and Peterseim, D. and Balzani, D.
    Acta Mechanica 233 4347-4364 (2022)
    doi: 10.1007/s00707-022-03332-1
  • 2022 • 776 Continuum multiscale modeling of absorption processes in micro- and nanocatalysts
    Köhler, M. and Junker, P. and Balzani, D.
    Archive of Applied Mechanics 92 2207-2223 (2022)
    doi: 10.1007/s00419-022-02172-8
  • 2022 • 775 Sauter-Schwinger Effect for Colliding Laser Pulses
    Kohlfürst, C. and Ahmadiniaz, N. and Oertel, J. and Schützhold, R.
    Physical Review Letters 129 (2022)
    doi: 10.1103/PhysRevLett.129.241801
  • 2022 • 774 Zeeman and Davydov splitting of Frenkel excitons in the antiferromagnet CuB2 O4
    Kopteva, N.E. and Kudlacik, D. and Yakovlev, D.R. and Eremin, M.V. and Nurmukhametov, A.R. and Bayer, M. and Pisarev, R.V.
    Physical Review B 105 (2022)
    The optical spectra of antiferromagnetic copper metaborate CuB2O4 are characterized by an exceptionally rich structure of narrow absorption lines due to electronic transitions within the magnetic Cu2+ ions, but their unambiguous identification and behavior in magnetic fields have remained far from being fully understood. We study the polarized magnetoabsorption spectra of this tetragonal antiferromagnet with high spectral resolution across the energy range of 1.4055-1.4065 eV in magnetic fields up to 9.5 T for temperatures from 1.6 up to the Néel temperature TN=20 K. We observe a set of eight absorption lines at T=1.6 K in magnetic fields exceeding 1.4 T, which we identify as arising from Frenkel excitons related to the ground and first excited states of the Cu2+ ions. The number of these excitons is defined by the presence of the four Cu2+ ions with doubly degenerate spin state S=1/2 at the 4b positions in the crystallographic unit cell. The energies of these excitons are determined by the exchange interaction of 0.5 meV of the Cu2+ ions in the excited state with the surrounding ions and by the Davydov splitting of 0.12 meV. In large magnetic field the observed Zeeman splitting is controlled by the anisotropic g-factors of both the ground and excited states. We develop a theoretical model of Frenkel excitons in the magnetic field that accounts for specific features of the spin structure and exchange interactions in CuB2O4. The model is used for fitting the experimental data and evaluation of the Frenkel exciton parameters, such as the Davydov splitting, the molecular exchange energy, and the g-factors of the ground and excited states of the Cu2+ ions. © 2022 American Physical Society.
    view abstractdoi: 10.1103/PhysRevB.105.024421
  • 2022 • 773 Extending the time of coherent optical response in ensemble of singly-charged InGaAs quantum dots
    Kosarev, A.N. and Trifonov, A.V. and Yugova, I.A. and Yanibekov, I.I. and Poltavtsev, S.V. and Kamenskii, A.N. and Scholz, S.E. and Sgroi, C.A. and Ludwig, A. and Wieck, A.D. and Yakovlev, D.R. and Bayer, M. and Akimov, I.A.
    Communications Physics 5 (2022)
    doi: 10.1038/s42005-022-00922-2
  • 2022 • 772 The role of DNA nanostructures in the catalytic properties of an allosterically regulated protease
    Kosinski, R. and Perez, J.M. and Schöneweiß, E.-C. and Ruiz-Blanco, Y.B. and Ponzo, I. and Bravo-Rodriguez, K. and Erkelenz, M. and Schlücker, S. and Uhlenbrock, G. and Sanchez-Garcia, E. and Saccà, B.
    Science Advances 8 (2022)
    DNA-scaffolded enzymes typically show altered kinetic properties; however, the mechanism behind this phenomenon is still poorly understood. We address this question using thrombin, a model of allosterically regulated serine proteases, encaged into DNA origami cavities with distinct structural and electrostatic features. We compare the hydrolysis of substrates that differ only in their net charge due to a terminal residue far from the cleavage site and presumably involved in the allosteric activation of thrombin. Our data show that the reaction rate is affected by DNA/substrate electrostatic interactions, proportionally to the degree of DNA/enzyme tethering. For substrates of opposite net charge, this leads to an inversion of the catalytic response of the DNA-scaffolded thrombin when compared to its freely diffusing counterpart. Hence, by altering the electrostatic environment nearby the encaged enzyme, DNA nanostructures interfere with charge-dependent mechanisms of enzyme-substrate recognition and may offer an alternative tool to regulate allosteric processes through spatial confinement. © 2022 The Authors.
    view abstractdoi: 10.1126/sciadv.abk0425
  • 2022 • 771 The effect of DNA boundaries on enzymatic reactions
    Kosiński, R. and Saccà, B.
    DNA Origami: Structures, Technology, and Applications 241-260 (2022)
  • 2022 • 770 Use of twin girder auxiliary bridges in the course of an emergency project for crossing the BAB 40 [Einsatz von Zwillingsträgerhilfsbrücken im Zuge einer Notmaßnahme zur Querung der BAB 40]
    Kosky, T. and Zillinger, W. and Shahnazian, A. and Ay, Y. and Stranghöner, N. and Afzali, N. and Makevičius, L. and Ungermann, D. and Kalameya, J.
    Stahlbau 91 72-83 (2022)
    Use of twin girder auxiliary bridges in the course of an emergency project for crossing the BAB 40. On 2020/09/17 a damaged fuel tanker completely burnt-out under a railway bridge over the German motorway A 40 between Duisburg and Mülheim a. d. R. Three out of five bridges had been damaged by the extremely high temperature that the structural and transport safety could no longer be ensured. Therefore the affected railway tracks of the DB Netz AG had to be shut. Immediately after the recording of damages, one bridge structure had been demolished. Due to the immediate detailed design for the replacement and the DB-internal as well as the governmental approvals the erection of the complete structure, including foundations, auxiliary bridges and rail system could be realized in a minimum amount of time. The initial operation of the bridges took place on 2020/12/28 (bridge 3) and 2012/09/06 (bridges 2, 4). Only by the use of twin-girder-auxiliary-bridges type ZH26 of the DB Netz AG the short-term replacement of the damaged bridges could be realized. Subsequent the whole building process is described. The available auxiliary-bridge-systems of the DB Netz AG and their limitations of use are summarized additionally. The use of the auxiliary-bridges as a structural chain as well as the use as permanent makeshift require DB-internal approvals. The required verifications, especially fatigue design, and the therefore required expertise for the durability of the bolted connections are described as well. © 2022, Ernst und Sohn. All rights reserved.
    view abstractdoi: 10.1002/stab.202100103
  • 2022 • 769 Linear growth of reaction layer during in-situ TEM annealing of thin film Al/Ni diffusion couples
    Kostka, A. and Naujoks, D. and Oellers, T. and Salomon, S. and Somsen, C. and Öztürk, E. and Savan, A. and Ludwig, A. and Eggeler, G.
    Journal of Alloys and Compounds 922 (2022)
    During reactive layer growth in binary diffusion couples new phases can nucleate and grow. In the present work we perform in- and ex-situ interdiffusion studies in the system Ni-Al using X-ray diffraction (XRD) and analytical transmission electron microscopy (TEM). We investigate the reaction between 270 °C and 500 °C. We show that in the early stages of the solid-state reaction a small polycrystalline aluminide layer forms, while preferential grain growth follows in the later stage. In the reaction layer we detect the presence of Al3Ni by XRD and electron diffraction. Local chemical analysis by EDX in the TEM suggests that a second aluminide phase forms simultaneously. An in-situ TEM study at 380 °C shows layer growth of about 0.042 nm/s with a linear time dependence. We interpret this rate law on the basis of an interface-controlled reaction and discuss our results in the light of what is known about layer growth in thin film diffusion couples (presence/absence of predicted phases, linear/parabolic rate laws) and in view of results from the Ni-Al system published in the literature. Areas in need of further work are identified. © 2022 The Authors
    view abstractdoi: 10.1016/j.jallcom.2022.165926
  • 2022 • 768 Ein Rumtopf chemisch betrachtet
    Kostka, K. and Kruse, B. and Fischer, C. and Epple, M.
    Chemie in Unserer Zeit (2022)
    doi: 10.1002/ciuz.202100075
  • 2022 • 767 A rum pot viewed chemically [Ein Rumtopf chemisch betrachtet]
    Kostka, K. and Kruse, B. and Fischer, C. and Epple, M.
    Chemie in Unserer Zeit 56 378-383 (2022)
    doi: 10.1002/ciuz.202100075
  • 2022 • 766 Microstructure analysis and mechanical properties of electron beam powder bed fusion (PBF-EB)-manufactured γ-titanium aluminide (TiAl) at elevated temperatures
    Kotzem, D. and Teschke, M. and Juechter, V. and Körner, C. and Walther, F.
    Materialpruefung/Materials Testing 64 636-646 (2022)
    Additively manufactured γ-titanium aluminide has a high specific strength and temperature resistance. This opens new possibilities for future lightweight constructions for aerospace applications. The objective of this work was to characterize additively manufactured Ti-48Al-2Cr-2Nb alloy specimens, which were successfully manufactured by electron beam powder bed fusion. For microstructural characterization, the as-built state was investigated with light and scanning electron microscopy. In the electron backscatter diffraction analysis, the size and the orientation of the grains were observed. The pore size and distribution were examined in computer tomographic scans, which showed a near fully dense material with a relative density of >99.9%. Furthermore, the hardness curve over the building height was examined in hardness mappings. Thereby, a strong decrease in hardness could be observed with an increase in part height. To evaluate the reliability of the manufactured alloy, quasi-static compression tests were carried out at temperatures up to 650 °C. Within these tests, a high compression strength (σc,p,0.2,650 °C = 684 MPa) was determined, which implicated a potential substitution of nickel-based superalloy components in aerospace applications under compressive loads. © 2022 Walter de Gruyter GmbH, Berlin/Boston.
    view abstractdoi: 10.1515/mt-2021-2137
  • 2022 • 765 Atomistic mechanisms underlying plasticity and crack growth in ceramics: a case study of AlN/TiN superlattices
    Koutná, N. and Löfler, L. and Holec, D. and Chen, Z. and Zhang, Z. and Hultman, L. and Mayrhofer, P.H. and Sangiovanni, D.G.
    Acta Materialia 229 (2022)
    doi: 10.1016/j.actamat.2022.117809
  • 2022 • 764 VeLABi-Research and control center for autonomous inland vessels [VeLABi-Forschungs- und Leitzentrum fur autonome Binnenschiffe]
    Kracht, F.E. and Jarofka, M. and Oberhagemann, J. and Henn, R. and Schramm, D.
    At-Automatisierungstechnik 70 411-419 (2022)
    This paper describes the conception and implementation of the research and control center VeLABi for the development of automation functions up to a fully autonomous inland vessel. A high-tech simulator was designed and built as the central component of VeLABi. It allows simulative developments and demonstrations of automation functions. Furthermore, ongoing research activities aim at transforming the simulator into a remote operators' stand to remotely control inland vessels and, in case of an autonomous vessel, to provide corresponding monitoring and emergency intervention functions. © 2022 Walter de Gruyter GmbH, Berlin/Boston.
    view abstractdoi: 10.1515/auto-2022-0007
  • 2022 • 763 BINOL as a chiral element in mechanically interlocked molecules
    Krajnc, M. and Niemeyer, J.
    Beilstein Journal of Organic Chemistry 18 508-523 (2022)
    In this minireview we present the use of the axially chiral 1,1'-binaphthyl-2,2'-diol (BINOL) unit as a stereogenic element in mechanically interlocked molecules (MIMs). We describe the synthesis and properties of such BINOL-based chiral MIMs, together with their use in further diastereoselective modifications, their application in asymmetric catalysis, and their use in stereoselective chemosensing. Given the growing importance of mechanically interlocked molecules and the key advantages of the privileged chiral BINOL backbone, we believe that this research area will continue to grow and deliver many useful applications in the future. © 2022 Krajnc and Niemeyer.
    view abstractdoi: 10.3762/bjoc.18.53
  • 2022 • 762 Martensite Transformation in Tool Steels under Isostatic Pressure–Implementation of In-Situ Electrical Resistivity Measurements into a Hot Isostatic Press with Rapid Quenching Technology
    Kramer, B. and Deng, Y. and Lentz, J. and Broeckmann, C. and Theisen, W. and Weber, S.
    Metals 12 (2022)
    Powder metallurgical (PM) parts usually benefit from more homogenous and finer mi-crostructures as opposed to conventionally processed material. In particular, hot isostatic pressing (HIP) combined with near-net-shape technologies can produce almost defect free PM tools with com-plex geometries. Recent advances in the plant technology of smaller HIP units allow the integration of hardening heat treatments in HIP processes. Thus, additional processing steps, transportation, energy consumption and cost are reduced. However, it is known that high pressure influences phase stability and transformation temperatures. Still, knowledge of the martensite start temperature (MS) is crucial for the design of hardening heat treatment. Since the influence of pressure on MS in HIP heat treatment is insufficiently investigated, it is the aim of this study to deploy a measurement method that allows to record MS as a function of pressure, temperature and cooling rate. Taking the hot working tool steel AISI H11 (X37CrMoV5-1, 1.2343) as the reference material, in this study for the first time the method of an in-situ electrical resistivity measurement was used to measure MS within a HIP. To investigate the influence of HIP pressure on Ms, resulting microstructures and hardness, specimens were austenitized at a temperature of TAUS = 1050◦ C for tAUS = 30 min at pAUS = 25, 50, 100 or 150 MPa. Additionally, the MS temperature of the same material was determined by quenching dilatometry at ambient pressure for comparison purposes. Characterization of microstructures was conducted by scanning electron microscopy while hardness as an important technological property of tool steels was measured according to the Vickers method. Furthermore, the CALPHAD method was used to compute the thermodynamic influence of pressure on phase stabilities. The experimental results indicate that the method of in-situ resistivity measurement can be used to measure MS during an integrated HIP heat-treatment process. Besides, a stabilizing effect of pressure on the close packed crystal structure of the austenitic fcc phase is clearly detected, resulting in a reducing influence on the MS temperature of AISI H11 by up to 90 K. © 2022 by the authors. Licensee MDPI, Basel, Switzerland.
    view abstractdoi: 10.3390/met12050708
  • 2022 • 761 Relaxation of photoexcited hot carriers beyond multitemperature models: General theory description verified by experiments on Pb/Si(111)
    Kratzer, P. and Rettig, L. and Sklyadneva, I.Y. and Chulkov, E.V. and Bovensiepen, U.
    Physical Review Research 4 (2022)
    doi: 10.1103/PhysRevResearch.4.033218
  • 2022 • 760 Uniaxially Aligned 1D Sandwich-Molecular Wires: Electronic Structure and Magnetism
    Kraus, S. and Herman, A. and Huttmann, F. and Bianchi, M. and Stan, R.-M. and Holt, A.J. and Tsukamoto, S. and Rothenbach, N. and Ollefs, K. and Dreiser, J. and Bischof, K. and Wende, H. and Hofmann, P. and Atodiresei, N. and Michely, T.
    Journal of Physical Chemistry C 126 3140-3150 (2022)
    Sandwich-molecular wires consisting of europium and cyclooctatetraene (Cot) were grown in situ on the moiré of graphene with Ir(110). The moiré templates a uniaxial alignment of monolayer EuCot nanowire carpets and multilayer films with the EuCot wire axis along the [001] direction of the Ir substrate. Using angle-resolved photoemission spectroscopy, we investigate the band structure of the wire carpet films. While π-derived bands were not observed experimentally, we find a flat band 1.85 eV below the Fermi energy. Using density-functional theory and X-ray photoelectron spectroscopy and replacing europium through barium in the sandwich-molecular wires, it is concluded that the flat band is derived from Eu 4f states weakly mixed with Eu 5d states and slightly overlapping with Cot π states. X-ray magnetic circular dichroism is employed to characterize the magnetic properties of the EuCot wire carpet films at low temperatures. Clear evidence for an easy-axis magnetization along the wires is found. © 2022 American Chemical Society
    view abstractdoi: 10.1021/acs.jpcc.1c10625
  • 2022 • 759 Selecting the Reaction Path in On-Surface Synthesis through the Electron Chemical Potential in Graphene
    Kraus, S. and Herman, A. and Huttmann, F. and Krämer, C. and Amsharov, K. and Tsukamoto, S. and Wende, H. and Atodiresei, N. and Michely, T.
    Journal of the American Chemical Society 144 11003-11009 (2022)
    The organometallic on-surface synthesis of the eight-membered sp2 carbon-based ring cyclooctatetraene (C8H8, Cot) with the neighboring rare-earth elements ytterbium and thulium yields fundamentally different products for the two lanthanides, when conducted on graphene (Gr) close to the charge neutrality point. Sandwich-molecular YbCot wires of more than 500 Å length being composed of an alternating sequence of Yb atoms and upright-standing Cot molecules result from the on-surface synthesis with Yb. In contrast, repulsively interacting TmCot dots consisting of a single Cot molecule and a single Tm atom result from the on-surface synthesis with Tm. While the YbCot wires are bound through van der Waals interactions to the substrate, the dots are chemisorbed to Gr via the Tm atoms being more electropositive compared to Yb atoms. When the electron chemical potential in Gr is substantially raised (n-doping) through backside doping from an intercalation layer, the reaction product in the synthesis with Tm can be tuned to TmCot sandwich-molecular wires rather than TmCot dots. By use of density functional theory, it is found that the reduced electronegativity of Gr upon n-doping weakens the binding as well as the charge transfer between the reaction intermediate TmCot dot and Gr. Thus, the assembly of the TmCot dots to long TmCot sandwich-molecular wires becomes energetically favorable. It is thereby demonstrated that the electron chemical potential in Gr can be used as a control parameter in an organometallic on-surface synthesis to tune the outcome of a reaction. © 2022 The Authors. Published by American Chemical Society.
    view abstractdoi: 10.1021/jacs.2c04359
  • 2022 • 758 Single-crystal graphene on Ir(110)
    Kraus, S. and Huttmann, F. and Fischer, J. and Knispel, T. and Bischof, K. and Herman, A. and Bianchi, M. and Stan, R.-M. and Holt, A.J. and Caciuc, V. and Tsukamoto, S. and Wende, H. and Hofmann, P. and Atodiresei, N. and Michely, T.
    Physical Review B 105 (2022)
    A single-crystal sheet of graphene is synthesized on the low-symmetry substrate Ir(110) by thermal decomposition of C2H4 at 1500 K. Using scanning tunneling microscopy, low-energy electron diffraction, angle-resolved photoemission spectroscopy, and ab initio density functional theory, the structure and electronic properties of the adsorbed graphene sheet and its moiré with the substrate are uncovered. The adsorbed graphene layer forms a wave pattern of nanometer wavelength with a corresponding modulation of its electronic properties. This wave pattern is demonstrated in density functional theory calculations to enable the templated adsorption of naphthalene molecules, and in experiment to uniaxially align sandwich-molecular wires composed of Eu and cyclooctatetraene molecules. © 2022 American Physical Society.
    view abstractdoi: 10.1103/PhysRevB.105.165405
  • 2022 • 757 Superconducting Instabilities in Strongly Correlated Infinite-Layer Nickelates
    Kreisel, A. and Andersen, B.M. and Rømer, A.T. and Eremin, I.M. and Lechermann, F.
    Physical Review Letters 129 (2022)
    doi: 10.1103/PhysRevLett.129.077002
  • 2022 • 756 Transfer-Substrate Process for InP RTD-Oscillator Characterization
    Kress, R. and Mutlu, E. and Kubiczek, T. and Kossmann, J. and Preuss, C. and Schultze, T. and Balzer, J.C. and Prost, W. and Weimann, N.
    2022 5th International Workshop on Mobile Terahertz Systems, IWMTS 2022 (2022)
    THz oscillators with on-chip antennas containing no ground plane are affected by substrate modes and therefore undirected radiation into free space. When integrating such antennas with focusing lenses, accurate sub-μm alignment is required. This work presents an assembly process utilizing an HRFZ-Si transfer substrate between the InP RTD chip and a hyper-hemispherical silicon lens, enabling precise alignment. We developed a bonding process for 1.2 × 1.2 mm2 InP RTD chips with an optical adhesive utilizing an advanced sub-micron bonder. THz-TDS measurements of the HRFZ silicon wafer were carried out to analyze the losses within the created setup by EM simulations. The assembly process was verified with measurements of a 300 GHz triple barrier (TB)-RTD oscillator using an SBD detector. © 2022 IEEE.
    view abstractdoi: 10.1109/IWMTS54901.2022.9832457
  • 2022 • 755 Comparison of the performance of a microwave plasma torch and a gliding arc plasma for hydrogen production via methane pyrolysis
    Kreuznacht, S. and Purcel, M. and Böddeker, S. and Awakowicz, P. and Xia, W. and Muhler, M. and Böke, M. and Keudell, A.V.
    Plasma Processes and Polymers (2022)
    Hydrogen production via plasma methane pyrolysis is investigated using a microwave plasma torch (MPT) and a gliding arc plasmatron (GAP). The performance of the two plasma sources in terms of methane conversion, product spectrum, and energy efficiency is compared. The physical and chemical properties of the produced carbon particles are compared. The methane conversion is higher in the GAP than in the MPT. In the MPT amorphous spherical carbon particles are produced in the volume of the plasma source. In the GAP methane pyrolysis in the volume stops after the production of acetylene. The conversion of acetylene into solid carbon takes place in a heterogeneous reaction on top of the electrode surfaces instead. This leads to a lower hydrogen selectivity, higher acetylene selectivity and more platelet-like morphology of the produced carbon particles when compared to the MPT. © 2022 The Authors. Plasma Processes and Polymers published by Wiley-VCH GmbH.
    view abstractdoi: 10.1002/ppap.202200132
  • 2022 • 754 Tuning the Electronic Properties of Homoleptic Silver(I) bis-BIAN Complexes towards Efficient Electrocatalytic CO2 Reduction
    Krisch, D. and Sun, H. and Pellumbi, K. and Faust, K. and Apfel, U.-P. and Schöfberger, W.
    Catalysts 12 (2022)
    doi: 10.3390/catal12050545
  • 2022 • 753 Influence of Temperature and Concentration on the Self-Assembly of Nonionic CiEj Surfactants: A Light Scattering Study
    Kroll, P. and Benke, J. and Enders, S. and Brandenbusch, C. and Sadowski, G.
    ACS Omega 7 7057-7065 (2022)
    Nonionic poly(ethylene oxide) alkyl ether (CiEj) surfactants self-assemble into aggregates of various sizes and shapes above their critical micelle concentration (CMC). Knowledge on solution attributes such as CMC as well as aggregate characteristics is crucial to choose the appropriate surfactant for a given application, e.g., as a micellar solvent system. In this work, we used static and dynamic light scattering to measure the CMC, aggregation number (Nagg), and hydrodynamic radius (Rh) of four different CiEj surfactants (C8E5, C8E6, C10E6, and C10E8). We examined the influence of temperature, concentration, and molecular structure on the self-assembly in the vicinity of the CMC. A minimum in the CMC vs temperature curve was identified for all surfactants investigated. Further, extending the hydrophilic and hydrophobic chain lengths leads to an increase and decrease of the CMC, respectively. The size of the aggregates strongly depends on temperature. Nagg and Rh increase with increasing temperature for all surfactants investigated. Additionally, Nagg and Rh both increase with increasing surfactant concentration. The data obtained in this work further improve the understanding of the influence of temperature and molecular structure on the self-assembly of CiEj surfactants and will further foster their use in micellar solvent systems. © 2022 The Authors. Published by American Chemical Society
    view abstractdoi: 10.1021/acsomega.1c06766
  • 2022 • 752 Efficient Prediction of Grain Boundary Energies from Atomistic Simulations via Sequential Design
    Kroll, M. and Schmalofski, T. and Dette, H. and Janisch, R.
    Advanced Theory and Simulations 5 (2022)
    doi: 10.1002/adts.202100615
  • 2022 • 751 Solubilization of Aldehydes and Amines in Aqueous C iE jSurfactant Aggregates: Solubilization Capacity and Aggregate Properties
    Kroll, P. and Sadowski, G. and Brandenbusch, C.
    Langmuir 38 10022-10031 (2022)
    Hydroformylation of olefins to aldehydes and subsequent reductive amination of aldehydes to amines takes place in an aqueous system using a water-soluble catalyst. It is limited to short-chain molecules due to an insufficient solubility of long-chain molecules in water. A promising approach to increase the solubility of long-chain aldehydes and amines is the addition of surfactants to the aqueous phase. In this work, we thus determined the solubilization capacity (SC) of different nonionic CiEj surfactants (C8E6, C10E6, and C10E8) toward long-chain aldehydes and amines. We used static and dynamic light scattering techniques to investigate the influence of both the surfactant and solute molecular structures on the SC as well as on the aggregation number (Nagg) and hydrodynamic radius (Rh) of mixed aggregates. Our data reveals that an optimum ratio of hydrophobic to hydrophilic chain length of CiEj surfactants exists where the SC toward long-chain aldehydes and amines possesses a maximum. Further, the size of the aggregates (Nagg, Rh) passes through a minimum upon amine solubilization, while upon aldehyde solubilization, the aggregate size increases gradually. The results shown in this work give valuable insights to the solubilization of aldehydes and n-amines into nonionic CiEj surfactants and facilitate the search of suitable surfactants for hydroformylation and reductive amination as "green"solvents based on the detailed knowledge about the aggregate structure. © 2022 The Authors. Published by American Chemical Society.
    view abstractdoi: 10.1021/acs.langmuir.2c01463
  • 2022 • 750 Quantification of methods used in field metallography using the example of quality assurance measures for a circular economy for high-alloy steels [Quantifizierung von Methoden der Ambulanten Metallographie an qualitätssichernden Maßnahmen einer zirkulären Wertschöpfung hochlegierter Stähle]
    Kronenberg, P. and Wieczorek, L. and Weber, S.L. and Röttger, A.
    Praktische Metallographie/Practical Metallography 59 296-316 (2022)
    This study aims to develop a method for on-site metallography, enabling the characterization of carbide banding in cold-work steels via cellulose acetate film replication. It will be demonstrated that for this purpose, it is sufficient to grind the sample surface using P1500 mesh SiC abrasive paper and etch it with V2A etchant or nitric acid for 7 minutes. By sample preparation and etching, the matrix of the parent material is sufficiently removed for the carbides to leave a "negative"impression on the film. This negative replica can then be studied under reflected light microscope, enabling the characterization of carbide banding. © 2022 Walter de Gruyter GmbH, Berlin/Boston, Germany.
    view abstractdoi: 10.1515/pm-2022-0034
  • 2022 • 749 Formation and Cleavage of a Sb−Sb Double Bond: From Carbene-Coordinated Distibenes to Stibinidenes
    Krüger, J. and Wölper, C. and Auer, A.A. and Schulz, S.
    European Journal of Inorganic Chemistry 2022 (2022)
    Reactions of L(Cl)Ga-substituted stibine [L(Cl)Ga]2SbCl (L=HC[C(Me)NAr]2; Ar=2,6-i-Pr2C6H3) with N-heterocyclic carbenes RNHCMe (RNHCMe=[C(R)NMe]2C:; R=Me, Et, iPr) gave NHC-coordinated stibinidenes L(Cl)GaSb-RNHCMe (R=Me 1 a, Et 1 b, iPr 1 c) and distibenes L(Cl)GaSbSb(RNHCMe)Ga(Cl)L (R=Me 2 a, Et 2 b, iPr 2 c). Distibenes 2 a and 2 b react with a second equivalent of RNHCMe with cleavage of the Sb−Sb double bond and formation of stibinidenes 1 a and 1 b. 1 a–2 b were spectroscopically characterized and the solid-state structures determined by single crystal X-ray diffraction (sc-XRD). Quantum chemical calculations gave a deeper insight into the electronic nature and bonding situation of 1 a–2 c and the reaction energetics were investigated in detail. © 2021 The Authors. European Journal of Inorganic Chemistry published by Wiley-VCH GmbH
    view abstractdoi: 10.1002/ejic.202100960
  • 2022 • 748 Switching from Heteronuclear Allyl Cations to Vinyl Cations by Using a Chemical Charge Trap
    Krüger, J. and Wölper, C. and Haberhauer, G. and Schulz, S.
    Inorganic Chemistry 61 597-604 (2022)
    Halide abstraction of the carbene-coordinated pnictinidenes (MecAAC)EGa(Cl)L (E = As 1, Sb 2, Bi 3, MecAAC = [H2C(CMe2)2NDipp]C; L = HC[C(Me)NDipp]2; Dipp = 2,6-i-Pr2C6H3) yielded the series of cationic group 15 compounds [(MecAAC)EGaL][Al(ORF)4] (E = As 4, Sb 5; Al(ORF)4 = Al(OC(CF3)3)4) and [(MecAAC)EGaL][B(ArF)4] (E = Sb 6, Bi 7; B(ArF)4 = B[C6H3(CF3)2]4), which were characterized by heteronuclear NMR spectroscopy and sc-XRD. The electronic nature of the cations [(MecAAC)EGaL]+ is controlled by the central pnictogen atom, according to quantum chemical calculations. The calculations furthermore demonstrated that compounds containing the lighter pnictogens (E = N, P) are best described as heteronuclear allyl cations, whereas heavier pnictogen atoms (E = As, Sb, Bi) serve as a trap for the positive charge, resulting in carbene-stabilized heterovinyl-type structures. © 2021 The Authors. Published by American Chemical Society.
    view abstractdoi: 10.1021/acs.inorgchem.1c03279
  • 2022 • 747 Single-Electron Oxidation of Carbene-Coordinated Pnictinidenes-Entry into Heteroleptic Radical Cations and Metalloid Clusters
    Krüger, J. and Haak, J. and Wölper, C. and Cutsail, G.E. and Haberhauer, G. and Schulz, S.
    Inorganic Chemistry 61 5878-5884 (2022)
    Stable heavy main group element radicals are challenging synthetic targets. Although several strategies have been developed to stabilize such odd-electron species, the number of heavier pnictogen-centered radicals is limited. We report on a series of two-coordinated pnictogen-centered radical cations [(MecAAC)EGa(Cl)L][B(C6F5)4] (MecAAC = [H2C(CMe2)2NDipp]C; Dipp = 2,6-i-Pr2C6H3; E = As 1, Sb 2, Bi 3; L = HC[C(Me)NDipp]2) synthesized by one-electron oxidation of L(Cl)Ga-substituted pnictinidenes (MecAAC)EGa(Cl)L (E = As I, Sb II, Bi III). 1-3 were characterized by electron paramagnetic resonance (EPR) spectroscopy and single crystal X-ray diffraction (sc-XRD) (1, 2), while quantum chemical calculations support their description as carbene-coordinated pnictogen-centered radical cations. The low thermal stability of 3 enables access to metalloid bismuth clusters as shown by formation of [{LGa(Cl)}3Bi6][B(C6F5)4] (4). © 2022 American Chemical Society.
    view abstractdoi: 10.1021/acs.inorgchem.2c00249
  • 2022 • 746 Role of Group 13 Metals in the Electronic Properties of L(X)M-Substituted Pnictinidenes
    Krüger, J. and Wölper, C. and Schulz, S.
    Organometallics 41 3788-3793 (2022)
    doi: 10.1021/acs.organomet.2c00515
  • 2022 • 745 Explaining the Release Mechanism of Ritonavir/PVPVA Amorphous Solid Dispersions
    Krummnow, A. and Danzer, A. and Voges, K. and Dohrn, S. and Kyeremateng, S.O. and Degenhardt, M. and Sadowski, G.
    Pharmaceutics 14 (2022)
    In amorphous solid dispersions (ASDs), an active pharmaceutical ingredient (API) is dissolved on a molecular level in a polymeric matrix. The API is expected to be released from the ASD upon dissolution in aqueous media. However, a series of earlier works observed a drastic collapse of the API release for ASDs with high drug loads (DLs) compared to those with low DLs. This work provides a thermodynamic analysis of the release mechanism of ASDs composed of ritonavir (RIT) and poly(vinylpyrrolidone-co-vinyl acetate) (PVPVA). The observed release behavior is, for the first time, explained based on the quantitative thermodynamic phase diagram predicted by PC-SAFT. Both liquid–liquid phase separation in the dissolution medium, as well as amorphous phase separation in the ASD, could be linked back to the same thermodynamic origin, whereas they had been understood as different phenomena so far in the literature. Furthermore, it is illustrated that upon release, independent of DL, both phenomena occur simultaneously for the investigated system. It could be shown that the non-congruent release of the drug and polymer is observed when amorphous phase separation within the ASD has taken place to some degree prior to dissolution. Nanodroplet formation in the dissolution medium could be explained as the liquid–liquid phase separation, as predicted by PC-SAFT. © 2022 by the authors.
    view abstractdoi: 10.3390/pharmaceutics14091904
  • 2022 • 744 Approximate Fast Fourier Transform-based Preprocessing for Edge AI
    Krupp, L. and Wiede, C. and Grabmaier, A.
    IEEE International Conference on Emerging Technologies and Factory Automation, ETFA 2022-September (2022)
    doi: 10.1109/ETFA52439.2022.9921684
  • 2022 • 743 The mechanochemical synthesis of polymers
    Krusenbaum, A. and Grätz, S. and Tigineh, G.T. and Borchardt, L. and Kim, J.G.
    Chemical Society Reviews 51 2873-2905 (2022)
    Mechanochemistry - the utilization of mechanical forces to induce chemical reactions - is a rarely considered tool for polymer synthesis. It offers numerous advantages such as reduced solvent consumption, accessibility of novel structures, and the avoidance of problems posed by low monomer solubility and fast precipitation. Consequently, the development of new high-performance materials based on mechanochemically synthesised polymers has drawn much interest, particularly from the perspective of green chemistry. This review covers the constructive mechanochemical synthesis of polymers, starting from early examples and progressing to the current state of the art while emphasising linear and porous polymers as well as post-polymerisation modifications. © 2022 The Royal Society of Chemistry
    view abstractdoi: 10.1039/d1cs01093j
  • 2022 • 742 The mechanochemical Friedel-Crafts polymerization as a solvent-free cross-linking approach toward microporous polymers
    Krusenbaum, A. and Geisler, J. and Kraus, F.J.L. and Grätz, S. and Höfler, M.V. and Gutmann, T. and Borchardt, L.
    Journal of Polymer Science 60 62-71 (2022)
    Herein we report the mechanochemical Friedel-Crafts alkylation of 1,3,5-triphenylbenzene (TPB) with two organochloride cross-linking agents, dichloromethane (DCM) and chloroform (CHCl3), respectively. During a thorough milling parameter evaluation, the DCM-linked polymers were found to be flexible and extremely sensitive toward parameter changes, which even enables the synthesis of a polymer with a SSABET of 1670 m2/g, on par with the solution-based reference. Contrary, CHCl3-linked polymers are exhibiting a rigid structure, with a high porosity that is widely unaffected by parameter changes. As a result, a polymer with a SSABET of 1280 m2/g could be generated in as little as 30 minutes, outperforming the reported literature analogue in terms of synthesis time and SSABET. To underline the environmental benefits of our fast and solvent-free synthesis approach, the green metrics are discussed, revealing an enhancement of the mass intensity, mass productivity and the E-factor, as well as of synthesis time and the work-up in comparison to the classical synthesis. Therefore, the mechanochemical polymerization is presented as a versatile tool, enabling the generation of highly porous polymers within short reaction times, with a minimal use of chlorinated cross-linker and with the possibility of a post polymerization modification. © 2021 The Authors. Journal of Polymer Science published by Wiley Periodicals LLC.
    view abstractdoi: 10.1002/pol.20210606
  • 2022 • 741 Carbon-nitrogen bond formation on Cu electrodes during CO2 reduction in NO3- solution
    Krzywda, P.M. and Paradelo Rodríguez, A. and Benes, N.E. and Mei, B.T. and Mul, G.
    Applied Catalysis B: Environmental 316 (2022)
    We demonstrate by Raman Spectroscopy that simultaneous reduction of NO3- and CO2 on Cu surfaces leads to formation of Cu-C[tbnd]N–like species, showing Raman bands at 2080 and 2150 cm−1 when associated with reduced or oxidized Cu surfaces, respectively. Furthermore Cu-C[tbnd]N–like species are soluble, explaining vast restructuring of the Cu surface observed after co-electrolysis of CO2 and nitrate. Oxidation of deposited Cu-C[tbnd]N–like species results in the formation of NO. Cu-C[tbnd]N–like species do not form in electrolytes containing i) NH4+ and CO2, or ii) NO3- and HCOO-, suggesting these likely originate from Cu-CO, the commonly accepted intermediate in electrochemical reduction of CO2, and Cu-NHx species, previously identified in the literature as intermediate towards C-N bond formation. The implications of the previously unresolved formation of Cu-C[tbnd]N–like species for the development of electrodes and processes for electrochemical formation of carbon-nitrogen bonds, including urea, amines or amides, are briefly discussed. © 2022 The Authors
    view abstractdoi: 10.1016/j.apcatb.2022.121512
  • 2022 • 740 Effect of Electrolyte and Electrode Configuration on Cu-Catalyzed Nitric Oxide Reduction to Ammonia
    Krzywda, P.M. and Paradelo Rodríguez, A. and Benes, N.E. and Mei, B.T. and Mul, G.
    ChemElectroChem 9 (2022)
    Reduction of nitric oxide was investigated using Cu electrodes in acid and neutral pH conditions. Analysis of Cu discs in stagnant electrolyte by Electrochemical Mass Spectrometry (EC-MS), revealed the favorable formation of ammonia (and hydrogen) in acidic electrolyte, while N2O and N2 are formed in significant quantities at neutral conditions. Additional performance evaluation of Cu electrodes in hollow fiber geometry, was performed using 10 vol % NO in Ar supplied through the porous electrode structure and off-line determination of ammonia by 1H NMR spectroscopy. The pH dependent performance of the Cu hollow fiber is in agreement with EC-MS data at low gas flow rates, showing the highest ammonia selectivity in acidic conditions. However, at relatively high gas flow rates, almost 90 % faradaic efficiency and a NH3 production rate of 400 μmol h−2 cm−2 were obtained in neutral electrolyte at −0.6 V vs RHE, likely due to enhanced availability of NO at the electrode surface, suppressing the hydrogen evolution reaction. This approach shows conversion of waste NO gas to valuable green fertilizer components is possible. © 2021 The Authors. ChemElectroChem published by Wiley-VCH GmbH
    view abstractdoi: 10.1002/celc.202101273
  • 2022 • 739 Electroreduction of NO3− on tubular porous Ti electrodes
    Krzywda, P.M. and Paradelo Rodríguez, A. and Cino, L. and Benes, N.E. and Mei, B.T. and Mul, G.
    Catalysis Science and Technology (2022)
    Inefficient fertilizer use in agriculture causes nitrate runoff, polluting rivers and streams. This pollution can be mitigated by partially converting nitrate into ammonia - rebalancing the composition to ammonium nitrate, and allowing recycling of fertilizer. Here, we present efficient electrochemical conversion of nitrate (50 mM) to ammonia in acidic electrolyte using tubular porous Ti electrodes. A high faradaic efficiency (FE) of 58% and partial current density to ammonia of −33 mA cm−2 at −1 V vs. RHE were achieved in the absence of inert gas purge. Additionally, we reveal that hydroxylamine is formed, as well as NO and N2O by spontaneous decomposition of nitrite, as has been determined by EC-MS analysis. The effective increase in local mass transport by introducing a flow of inert gas exiting the wall of the hollow fiber electrode results in an unprecedently high partial current density to ammonia of ∼−75 mA cm−2, while maintaining a faradaic efficiency to ammonia of up to 45%. This concept facilitates nitrate conversion at high FE even at low concentrations, and holds promise for development to practical scale if electrochemical potential and exiting gas flow rate are well controlled. © 2022 The Royal Society of Chemistry.
    view abstractdoi: 10.1039/d2cy00289b
  • 2022 • 738 Removal of Artifacts in THz Imaging with a Synthetic Aperture
    Kubiczek, T. and Kolpatzeck, K. and Schultze, T. and Balzer, J.C.
    International Conference on Infrared, Millimeter, and Terahertz Waves, IRMMW-THz 2022-August (2022)
    Terahertz time-domain spectroscopy (THz-TDS) measurements from synthetic aperture radar (SAR) type measurements enable high resolution imaging. However, the reconstructed images show artifacts and noise. In this work, the benefit of considering the antenna pattern to reduce artifacts is demonstrated. Additionally, the limitations of focused transmission measurements are shown by measuring the beam profile in the focused and in the divergent part of a transmission terahertz path. © 2022 IEEE.
    view abstractdoi: 10.1109/IRMMW-THz50927.2022.9896056
  • 2022 • 737 3D Printed Terahertz Filter as a Broadband Frequency Reference
    Kubiczek, T. and Kolpatzeck, K. and Schultze, T. and Balzer, J.C.
    International Conference on Infrared, Millimeter, and Terahertz Waves, IRMMW-THz 2022-August (2022)
    A simple broadband terahertz transmission filter with strong absorption lines and medium broadband attenuation is introduced. The filter is 3D printed using a low-loss cyclic olefin copolymer (COC) filament and characterized with a time-domain and a frequency-domain terahertz spectroscopy system. © 2022 IEEE.
    view abstractdoi: 10.1109/IRMMW-THz50927.2022.9895494
  • 2022 • 736 3D Printed Passive Beam-Guiding and Manipulating Devices for the Terahertz Frequency Range
    Kubiczek, T. and Liu, X. and Balzer, J.C. and Guo, X. and Sakaki, M. and Zhao, Y. and Benson, N.
    2022 IEEE 12th International Conference on RFID Technology and Applications, RFID-TA 2022 43-46 (2022)
    doi: 10.1109/RFID-TA54958.2022.9923966
  • 2022 • 735 From MAX Phase Carbides to Nitrides: Synthesis of V2GaC, V2GaN, and the Carbonitride V2GaC1-xN x
    Kubitza, N. and Reitz, A. and Zieschang, A.-M. and Pazniak, H. and Albert, B. and Kalha, C. and Schlueter, C. and Regoutz, A. and Wiedwald, U. and Birkel, C.S.
    Inorganic Chemistry 61 10634-10641 (2022)
    The research in MAX phases is mainly concentrated on the investigation of carbides rather than nitrides (currently >150 carbides and only <15 nitrides) that are predominantly synthesized by conventional solid-state techniques. This is not surprising since the preparation of nitrides and carbonitrides is more demanding due to the high stability and low diffusion rate of nitrogen-containing compounds. This leads to several drawbacks concerning potential variations in the chemical composition of the MAX phases as well as control of morphology, the two aspects that directly affect the resulting materials properties. Here, we report how alternative solid-state hybrid techniques solve these limitations by combining conventional techniques with nonconventional precursor synthesis methods, such as the "urea-glass"sol-gel or liquid ammonia method. We demonstrate the synthesis and morphology control within the V-Ga-C-N system by preparing the MAX phase carbide and nitride-the latter in the form of bulkier and more defined smaller particle structures-as well as a hitherto unknown carbonitride V2GaC1-xNx MAX phase. This shows the versatility of hybrid methods starting, for example, from wet chemically obtained precursors that already contain all of the ingredients needed for carbonitride formation. All products are characterized in detail by X-ray powder diffraction, electron microscopy, and electron and X-ray photoelectron spectroscopies to confirm their structure and morphology and to detect subtle differences between the different chemical compositions. © 2022 American Chemical Society.
    view abstractdoi: 10.1021/acs.inorgchem.2c00200
  • 2022 • 734 In-situ Investigation of the Onset of Cavitation Damage from Single Bubbles on Technical Alloys
    Kühlmann, J. and Lopez de Arcaute y Lozano, C. and Hanke, S. and Kaiser, S.A.
    Tribology Letters 70 (2022)
    doi: 10.1007/s11249-022-01665-5
  • 2022 • 733 Ultrafast transport and energy relaxation of hot electrons in Au/Fe/MgO(001) heterostructures analyzed by linear time-resolved photoelectron spectroscopy
    Kühne, F. and Beyazit, Y. and Sothmann, B. and Jayabalan, J. and Diesing, D. and Zhou, P. and Bovensiepen, U.
    Physical Review Research 4 (2022)
    doi: 10.1103/PhysRevResearch.4.033239
  • 2022 • 732 Real-Time Condition Monitoring of Filling Machines with Vibration Analysis and Edge AI
    Kuhnel, J. and Wiede, C. and Heidemann, B. and Grabmaier, A.
    2022 7th International Conference on Frontiers of Signal Processing, ICFSP 2022 173-178 (2022)
    doi: 10.1109/ICFSP55781.2022.9924652
  • 2022 • 731 Transition magnon modes in thin ferromagnetic nanogratings
    Kukhtaruk, S.M. and Rushforth, A.W. and Godejohann, F. and Scherbakov, A.V. and Bayer, M.
    Physical Review B 106 (2022)
    doi: 10.1103/PhysRevB.106.064411
  • 2022 • 730 Roadmap on Machine learning in electronic structure
    Kulik, H.J. and Hammerschmidt, T. and Schmidt, J. and Botti, S. and Marques, M.A.L. and Boley, M. and Scheffler, M. and Todorović, M. and Rinke, P. and Oses, C. and Smolyanyuk, A. and Curtarolo, S. and Tkatchenko, A. and Bartók,...
    Electronic Structure 4 (2022)
    doi: 10.1088/2516-1075/ac572f
  • 2022 • 729 Influence of the ZnCrAl Oxide Composition on the Formation of Hydrocarbons from Syngas
    Kull, T. and Wiesmann, T. and Wilmsen, A. and Purcel, M. and Muhler, M. and Lohmann, H. and Zeidler-Fandrich, B. and Apfel, U.-P.
    ACS Omega 7 42994-43005 (2022)
    doi: 10.1021/acsomega.2c05225
  • 2022 • 728 Efficient Nitrate Conversion to Ammonia on f-Block Single-Atom/Metal Oxide Heterostructure via Local Electron-Deficiency Modulation
    Kumar, A. and Lee, J. and Kim, M.G. and Debnath, B. and Liu, X. and Hwang, Y. and Wang, Y. and Shao, X. and Jadhav, A.R. and Liu, Y. and Tüysüz, H. and Lee, H.
    ACS Nano 16 15297-15309 (2022)
    Exploring single-atom catalysts (SACs) for the nitrate reduction reaction (NO3-NitRR) to value-added ammonia (NH3) offers a sustainable alternative to both the Haber-Bosch process and NO3--rich wastewater treatment. However, due to the insufficient electron deficiency and unfavorable electronic structure of SACs, resulting in poor NO3--adsorption, sluggish proton (H*) transfer kinetics, and preferred hydrogen evolution, their NO3--to-NH3selectivity and yield rate are far from satisfactory. Herein, a systematic theoretical prediction reveals that the local electron deficiency of an f-block Gd single atom (GdSA) can be significantly regulated upon coordination with oxygen-defect-rich NiO (GdSA-D-NiO400) support. Thus, facilitating stronger NO3-adsorption via strong Gd5d-O2porbital coupling and further improving the protonation kinetics of adsorption intermediates by rapid H∗ capture from water dissociation catalyzed by the adjacent oxygen vacancy site along with suppressed H∗ dimerization synergistically boosts the NH3selectivity/yield rate. Motivated by DFT prediction, we delicately stabilized electron-deficient (strongly electrophilic) GdSAon D-NiO400(?84% strong electrophilic sites), which exhibited excellent alkaline NitRR activity (NH3Faradaic efficiency ?97% and yield rate ?628 μg/(mgcath)) along with superior structural stability, as revealed by in situ Raman spectroscopy, significantly outperforming weakly electrophilic Gd nanoparticles, defect-free GdSA-P-NiO400, and reported state-of-the-art catalysts. © 2022 American Chemical Society. All rights reserved.
    view abstractdoi: 10.1021/acsnano.2c06747
  • 2022 • 727 Coherent chiroptical Raman spectroscopy
    Kumar, V. and Schlücker, S.
    Molecular and Laser Spectroscopy: Advances and Applications: Volume 3 3 101-139 (2022)
    doi: 10.1016/B978-0-323-91249-5.00015-6
  • 2022 • 726 Durability assessment of differently orientated surfaces of treated long-term weathered natural stones
    Kunz, A. and Groh, M. and Braun, F. and Brüggerhoff, S. and Orlowsky, J.
    Journal of Cultural Heritage 53 176-183 (2022)
    In this study, selected natural stone prisms have been compared with each other to detect the effectiveness of the hydrophobic treatment on differently orientated surfaces. The samples have been examined after 2 and 17 years of weathering at two different locations in Germany. The examinations focused on certain criteria which are based on the research of the last four years. By measuring colour changes, not only the influence of different hydrophobing agents could be investigated, but also different stone deterioration patterns could be identified. It could be determined that the effectiveness of water repellents is significantly influenced by the penetration and distribution depth of the active substance. The results of non-destructive NMR measurements show that the durability of the stones is more influenced by the uniform distribution of the active ingredient and the penetration depth than by the surface orientation. Thus, for the Obernkirchener Sandstone, the efficiency of the applied agents was proven after 17 years of outdoor weathering. Despite determined effective hydrophobic zones, degradation of the natural stones could not be prevented. Measuring the damaged depth with NMR it was found out that water penetrates the stone within the first 500 to 1000 µm, even with an intact hydrophobic layer, and can cause surface changes, like biogenic growth and decomposition. In these degradation processes, the orientation of the samples again has a significant influence. Thus, the roof surfaces show stronger deterioration. © 2021 Elsevier Masson SAS
    view abstractdoi: 10.1016/j.culher.2021.12.001
  • 2022 • 725 The role of electrons during the martensitic phase transformation in NiTi-based shape memory alloys
    Kunzmann, A. and Frenzel, J. and Wolff, U. and Han, J.W. and Giebeler, L. and Piorunek, D. and Mittendorff, M. and Scheiter, J. and Reith, H. and Perez, N. and Nielsch, K. and Eggeler, G. and Schierning, G.
    Materials Today Physics 24 (2022)
    doi: 10.1016/j.mtphys.2022.100671
  • 2022 • 724 Emergent phenomena at oxide interfaces studied with standing-wave photoelectron spectroscopy
    Kuo, C.-T. and Conti, G. and Rault, J.E. and Schneider, C.M. and Nemšák, S. and Gray, A.X.
    Journal of Vacuum Science and Technology A: Vacuum, Surfaces and Films 40 (2022)
    Emergent phenomena at complex-oxide interfaces have become a vibrant field of study in the past two decades due to the rich physics and a wide range of possibilities for creating new states of matter and novel functionalities for potential devices. The electronic-structural characterization of such phenomena presents a unique challenge due to the lack of direct yet nondestructive techniques for probing buried layers and interfaces with the required Ångstrom-level resolution, as well as element and orbital specificity. In this Review, we survey several recent studies wherein soft x-ray standing-wave photoelectron spectroscopy - a relatively newly developed technique - is used to investigate buried oxide interfaces exhibiting emergent phenomena such as metal-insulator transition, interfacial ferromagnetism, and two-dimensional electron gas. The advantages, challenges, and future applications of this methodology are also discussed. © 2022 Author(s).
    view abstractdoi: 10.1116/6.0001584
  • 2022 • 723 Real-Time Observation of Charge-Spin Cooperative Dynamics Driven by a Nonequilibrium Phonon Environment
    Kuroyama, K. and Matsuo, S. and Muramoto, J. and Yabunaka, S. and Valentin, S.R. and Ludwig, Ar. and Wieck, A.D. and Tokura, Y. and Tarucha, S.
    Physical Review Letters 129 (2022)
    We report on experimental observations of charge-spin cooperative dynamics of two-electron states in a GaAs double quantum dot located in a nonequilibrium phonon environment. When the phonon energy exceeds the lowest excitation energy in the quantum dot, the spin-flip rate of a single electron strongly enhances. In addition, originated from the spatial gradient of phonon density between the dots, the parallel spin states become more probable than the antiparallel ones. These results indicate that spin is essential for further demonstrations of single-electron thermodynamic systems driven by phonons, which will greatly contribute to understanding of the fundamental physics of thermoelectric devices. © 2022 American Physical Society.
    view abstractdoi: 10.1103/PhysRevLett.129.095901
  • 2022 • 722 Microstructure and corrosion properties of PBF-LB produced carbide nanoparticles additivated AlSi10Mg parts
    Kusoglu, I.M. and Vieth, P. and Heiland, S. and Huber, F. and Lüddecke, A. and Ziefuss, A.R. and Kwade, A. and Schmidt, M. and Schaper, M. and Barcikowski, S. and Grundmeier, G.
    Procedia CIRP 111 10-13 (2022)
    doi: 10.1016/j.procir.2022.08.046
  • 2022 • 721 Statistical inference for the slope parameter in functional linear regression
    Kutta, T. and Dierickx, G. and Dette, H.
    Electronic Journal of Statistics 16 5980-6042 (2022)
    doi: 10.1214/22-EJS2078
  • 2022 • 720 Bound-preserving Flux Limiting for High-Order Explicit Runge–Kutta Time Discretizations of Hyperbolic Conservation Laws
    Kuzmin, D. and Quezada de Luna, M. and Ketcheson, D.I. and Grüll, J.
    Journal of Scientific Computing 91 (2022)
    We introduce a general framework for enforcing local or global maximum principles in high-order space-time discretizations of a scalar hyperbolic conservation law. We begin with sufficient conditions for a space discretization to be bound preserving (BP) and satisfy a semi-discrete maximum principle. Next, we propose a global monolithic convex (GMC) flux limiter which has the structure of a flux-corrected transport (FCT) algorithm but is applicable to spatial semi-discretizations and ensures the BP property of the fully discrete scheme for strong stability preserving (SSP) Runge–Kutta time discretizations. To circumvent the order barrier for SSP time integrators, we constrain the intermediate stages and/or the final stage of a general high-order RK method using GMC-type limiters. In this work, our theoretical and numerical studies are restricted to explicit schemes which are provably BP for sufficiently small time steps. The new GMC limiting framework offers the possibility of relaxing the bounds of inequality constraints to achieve higher accuracy at the cost of more stringent time step restrictions. The ability of the presented limiters to recognize undershoots/overshoots, as well as smooth solutions, is verified numerically for three representative RK methods combined with weighted essentially nonoscillatory (WENO) finite volume space discretizations of linear and nonlinear test problems in 1D. In this context, we enforce global bounds and prove preservation of accuracy for the linear advection equation. © 2022, The Author(s), under exclusive licence to Springer Science+Business Media, LLC, part of Springer Nature.
    view abstractdoi: 10.1007/s10915-022-01784-0
  • 2022 • 719 Limiter-based entropy stabilization of semi-discrete and fully discrete schemes for nonlinear hyperbolic problems
    Kuzmin, D. and Hajduk, H. and Rupp, A.
    Computer Methods in Applied Mechanics and Engineering 389 (2022)
    The algebraic flux correction (AFC) schemes presented in this work constrain a standard continuous finite element discretization of a nonlinear hyperbolic problem to satisfy relevant maximum principles and entropy stability conditions. The desired properties are enforced by applying a limiter to antidiffusive fluxes that represent the difference between the high-order baseline scheme and a property-preserving approximation of Lax–Friedrichs type. In the first step of the limiting procedure, the given target fluxes are adjusted in a way that guarantees preservation of local and/or global bounds. In the second step, additional limiting is performed, if necessary, to ensure the validity of fully discrete and/or semi-discrete entropy inequalities. The limiter-based entropy fixes considered in this work are applicable to finite element discretizations of scalar hyperbolic equations and systems alike. The underlying inequality constraints are formulated using Tadmor's entropy stability theory. The proposed limiters impose entropy-conservative or entropy-dissipative bounds on the rate of entropy production by antidiffusive fluxes and Runge–Kutta (RK) time discretizations. Two versions of the fully discrete entropy fix are developed for this purpose. The first one incorporates temporal entropy production into the flux constraints, which makes them more restrictive and dependent on the time step. The second algorithm interprets the final stage of a high-order AFC-RK method as a constrained antidiffusive correction of an implicit low-order scheme (algebraic Lax–Friedrichs in space + backward Euler in time). In this case, iterative flux correction is required, but the inequality constraints are less restrictive and limiting can be performed using algorithms developed for the semi-discrete problem. To motivate the use of limiter-based entropy fixes, we prove a finite element version of the Lax–Wendroff theorem and perform numerical studies for standard test problems. In our numerical experiments, entropy-dissipative schemes converge to correct weak solutions of scalar conservation laws, of the Euler equations, and of the shallow water equations. © 2021 Elsevier B.V.
    view abstractdoi: 10.1016/j.cma.2021.114428
  • 2022 • 718 An unfitted finite element method using level set functions for extrapolation into deformable diffuse interfaces
    Kuzmin, D. and Bäcker, J.-P.
    Journal of Computational Physics 461 (2022)
    We explore a new way to handle flux boundary conditions imposed on level sets. The proposed approach is a diffuse interface version of the shifted boundary method (SBM) for continuous Galerkin discretizations of conservation laws in embedded domains. We impose the interface conditions weakly and approximate surface integrals by volume integrals. The discretized weak form of the governing equation has the structure of an immersed boundary finite element method. That is, integration is performed over a fixed fictitious domain. Source terms are included to account for interface conditions and extend the boundary data into the complement of the embedded domain. The calculation of these extra terms requires (i) construction of an approximate delta function and (ii) extrapolation of embedded boundary data into quadrature points. We accomplish these tasks using a level set function, which is given analytically or evolved numerically. A globally defined averaged gradient of this approximate signed distance function is used to construct a simple map to the closest point on the interface. The normal and tangential derivatives of the numerical solution at that point are calculated using the interface conditions and/or interpolation on uniform stencils. Similarly to SBM, extrapolation of data back to the quadrature points is performed using Taylor expansions. Computations that require extrapolation are restricted to a narrow band around the interface. Numerical results are presented for elliptic, parabolic, and hyperbolic test problems, which are specifically designed to assess the error caused by the numerical treatment of interface conditions on fixed and moving boundaries in 2D. © 2022 Elsevier Inc.
    view abstractdoi: 10.1016/j.jcp.2022.111218
  • 2022 • 717 A sustainable ultra-high strength Fe18Mn3Ti maraging steel through controlled solute segregation and α-Mn nanoprecipitation
    Kwiatkowski da Silva, A. and Souza Filho, I.R. and Lu, W. and Zilnyk, K.D. and Hupalo, M.F. and Alves, L.M. and Ponge, D. and Gault, B. and Raabe, D.
    Nature Communications 13 (2022)
    The enormous magnitude of 2 billion tons of alloys produced per year demands a change in design philosophy to make materials environmentally, economically, and socially more sustainable. This disqualifies the use of critical elements that are rare or have questionable origin. Amongst the major alloy strengthening mechanisms, a high-dispersion of second-phase precipitates with sizes in the nanometre range is particularly effective for achieving ultra-high strength. Here, we propose an alternative segregation-based strategy for sustainable steels, free of critical elements, which are rendered ultrastrong by second-phase nano-precipitation. We increase the Mn-content in a supersaturated, metastable Fe-Mn solid solution to trigger compositional fluctuations and nano-segregation in the bulk. These fluctuations act as precursors for the nucleation of an unexpected α-Mn phase, which impedes dislocation motion, thus enabling precipitation strengthening. Our steel outperforms most common commercial alloys, yet it is free of critical elements, making it a new platform for sustainable alloy design. © 2022, The Author(s).
    view abstractdoi: 10.1038/s41467-022-30019-x
  • 2022 • 716 Temperature Rise Inside Shear Bands in a Simple Model Glass
    Lagogianni, A.E. and Varnik, F.
    International Journal of Molecular Sciences 23 (2022)
    One of the key factors, which hampers the application of metallic glasses as structural components, is the localization of deformation in narrow bands of a few tens up to one hundred nanometers thickness, the so-called shear bands. Processes, which occur inside shear bands are of central importance for the question whether a catastrophic failure of the material is unavoidable or can be circumvented or, at least, delayed. Via molecular dynamics simulations, this study addresses one of these processes, namely the local temperature rise due to viscous heat generation. The major contribution to energy dissipation is traced back to the plastic work performed by shear stress during steady deformation. Zones of largest strain contribute the most to this process and coincide with high-temperature domains (hottest spots) inside the sample. Magnitude of temperature rise can reach a few percent of the sample’s glass transition temperature. Consequences of these observations are discussed in the context of the current research in the field. © 2022 by the authors.
    view abstractdoi: 10.3390/ijms232012159
  • 2022 • 715 Early particle formation and evolution in iron-doped flames
    Lalanne, M.R. and Wollny, P. and Nanjaiah, M. and Menser, J. and Schulz, C. and Wiggers, H. and Cheskis, S. and Wlokas, I. and Rahinov, I.
    Combustion and Flame 244 (2022)
    In flame synthesis of nanoparticles, the temperature history experienced by the nascent particle aerosol defines the morphology, composition, and crystallinity of the resulting nanomaterial. Commonly, flame-synthesis processes are modeled with an isothermal approximation assuming that the particle temperature replicates that of the surrounding gas phase, avoiding inclusion of an additional internal coordinate in the population balance model, and thus reducing the computational cost. This simplification neglects the influence of matter- and energy-exchange as well as thermochemistry between the particle and reactive gas phase, impacting the particle temperature. In this work, we investigate the temperature history of the particles in incipient formation stages and their evolution in iron-doped flames, prototypical for many other transition-metal (oxide) synthesis systems. The temperature and relative volume-fraction distributions of early particles forming in H2/O2/Ar flames doped with iron pentacarbonyl were determined for the first time, based on spectrally and spatially resolved flame emission measurements and pyrometric analysis of the continuum emission emanating from the nascent particle aerosol. The nascent particle temperature was found to be several hundred degrees above the gas-phase temperature for all physically reasonable assumptions concerning particle composition and emission efficiency. Early particles volume fraction rises sharply shortly after the decomposition of iron pentacarbonyl and decreases steeply in the flame front, in excellent agreement with previous particle-mass spectrometry/quartz-crystal microbalance measurements. By modeling the evaporation process of isothermal iron particles, we show that vanishing of particles in the flame front cannot be explained by evaporation of particles that are in thermal equilibrium with the gas phase. A single-particle Monte-Carlo simulation based on a simple model comprising Fe-monomer condensation, concurrent with oxidation, reduction, etching, and evaporation occurring at the particle surface, captures both the flame structure with respect to early particle formation and their excess temperature compared to the gas phase. © 2022
    view abstractdoi: 10.1016/j.combustflame.2022.112251
  • 2022 • 714 Ginzburg effect in a dielectric medium with dispersion and dissipation
    Lang, S. and Sauerbrey, R. and Schützhold, R. and Unruh, W.G.
    Physical Review Research 4 (2022)
    As a quantum analog of Cherenkov radiation, an inertial photon detector moving through a medium with constant refractive index n may perceive the electromagnetic quantum fluctuations as real photons if its velocity v exceeds the medium speed of light c/n. For dispersive Hopfield-type media, we find this Ginzburg effect to extend to much lower v because the phase velocity of light is very small near the medium resonance. In this regime, however, dissipation effects become important. Via an extended Hopfield model, we present a consistent treatment of quantum fluctuations in dispersive and dissipative media and derive the Ginzburg effect in such systems. Finally, we propose an experimental test. © 2022 authors. Published by the American Physical Society.
    view abstractdoi: 10.1103/PhysRevResearch.4.033074
  • 2022 • 713 How regularization concepts interfere with (quasi-)brittle damage: a comparison based on a unified variational framework
    Langenfeld, K. and Kurzeja, P. and Mosler, J.
    Continuum Mechanics and Thermodynamics 34 1517-1544 (2022)
    Three regularization concepts are assessed regarding their variational structure and interference with the predicted physics of (quasi-)brittle damage: the fracture energy concept, viscous regularization and micromorphic regularization. They are first introduced in a unified variational framework, depicting how they distinctively evolve from incremental energy minimization. The analysis of a certain time interval of a one-dimensional example is used to show how viscous and micromorphic regularization retains well-posedness within the softening regime. By way of contrast, the fracture energy concept is characterized by ill-posedness—as known from previous non-variational analyses. Numerical examples finally demonstrate the limitations and capabilities of each concept. The ill-posed local fracture energy concept leads by its design to a spatially constant fracture energy—in line with Griffith’s theory. The viscous regularization, in turn, yields a well-posed problem but artificial viscosity can add a bias to unloading and fracture thickness. Furthermore, and even more important, a viscous regularization does not predict a spatially constant fracture energy due to locally heterogeneous loading rates. The well-posed micromorphic regularization is in line with the underlying physics and does not show this undesired dependency. However, it requires the largest numerical efforts, since it is based on a coupled two-field formulation. © 2022, The Author(s).
    view abstractdoi: 10.1007/s00161-022-01143-2
  • 2022 • 712 Deuteron nuclear magnetic resonance and dielectric studies of molecular reorientation and charge transport in succinonitrile-glutaronitrile plastic crystals
    Lansab, S. and Münzner, P. and Zimmermann, H. and Böhmer, R.
    Journal of Non-Crystalline Solids: X 14 (2022)
    doi: 10.1016/j.nocx.2022.100097
  • 2022 • 711 Experimental Validation of an Analytical Condensation Model for Application in Steam Turbine Design
    Lapp, F.F. and Schuster, S. and Hecker, S. and Brillert, D.
    International Journal of Turbomachinery, Propulsion and Power 7 (2022)
    This paper presents experimental data on shear-stress-driven liquid water films on a horizontal plate formed by the condensation of superheated steam. The experimental results were obtained in the Experimental Multi-phase Measurement Application (EMMA) at the University of Duisburg-Essen. The liquid film thickness was spatially and temporally investigated with an optical measurement system. Furthermore, the resulting local heat transfer coefficient in the case of film condensation was determined for a variety of steam velocities and temperatures. Subsequently, the presented data are compared to the results of an analytical condensation model for shear-stressdriven liquid films developed by Cess and Koh. Thus, the model is qualitatively validated, with explicable remaining disparities between the model and experiment that are further discussed. The presented results are an important contribution to the contemporary research into steady-state, single-component multiphase flow considering phase-change phenomena including heat transfer. © 2022 by the authors. Licensee MDPI, Basel, Switzerland.
    view abstractdoi: 10.3390/ijtpp7010009
  • 2022 • 710 Aluminum Diethylphosphinate as a Flame Retardant for Polyethylene: Investigation of the Pyrolysis and Combustion Behavior of PE/AlPi-Mixtures
    Lau, S. and Gonchikzhapov, M. and Paletsky, A. and Shmakov, A. and Korobeinichev, O. and Kasper, T. and Atakan, B.
    Combustion and Flame 240 (2022)
    The popularity of organic polymers despite their high flammability forces the introduction of flame retardants (FR) such as metal phosphinates into the combustible material. The thermal behavior of aluminum diethylphosphinate (AlPi) as FR in the widely used polymer ultra-high molecular weight polyethylene (UHMWPE) is investigated here. The study focuses on the effect of the FR on the gas phase activity when a polymer is pyrolyzed or burned. For this purpose, the fast pyrolysis of AlPi was investigated by differential mass-spectrometric thermal analysis (DMSTA). Also, the thermal and chemical structures of diffusion flames of UHMWPE + AlPi specimens were investigated using micro thermocouples and molecular beam mass spectrometry, respectively. Small amounts of AlPi (2.5 wt.%) decrease the gas temperature significantly by a maximum of 155 K related to FR-free polymer flames, indicating a retardancy effect of the additive on the flame. From the results of subsequent limiting oxygen index (LOI) tests, it is obvious that a PE burn-up cannot be achieved in a self-sustained flame when an additive content above 10 wt.% is used as FR. In the mass-spectrometric studies, the phosphorus-containing species produced in the pyrolysis experiments (DMSTA) of the neat AlPi as well as the species which are formed in flames during combustion experiments can be detected. In the flames, the concentration of the phosphorus containing compounds peaks at low heights above the polymer surface which indicate a gas phase activity of AlPi or its pyrolysis products. Besides a charring layer on top of the burning surface could be noticed. The use of AlPi as a FR for UHMWPE shows flame retardant effects in both the condensed and the gas phase. © 2022 The Combustion Institute
    view abstractdoi: 10.1016/j.combustflame.2022.112006
  • 2022 • 709 Effects of aging on the stress-induced martensitic transformation and cyclic superelastic properties in Co-Ni-Ga shape memory alloy single crystals under compression
    Lauhoff, C. and Reul, A. and Langenkämper, D. and Krooß, P. and Somsen, C. and Gutmann, M.J. and Pedersen, B. and Kireeva, I.V. and Chumlyakov, Y.I. and Eggeler, G. and Schmahl, W.W. and Niendorf, T.
    Acta Materialia 226 (2022)
    Co-Ni-Ga shape memory alloys attracted scientific attention as promising candidate materials for damping applications at elevated temperatures, owing to excellent superelastic properties featuring a fully reversible stress-strain response up to temperatures as high as 500 °C. In the present work, the effect of aging treatments conducted in a wide range of aging temperatures and times, i.e. at 300–400 °C for 0.25–8.5 h, was investigated. It is shown that critical features of the martensitic transformation are strongly affected by the heat treatments. In particular, the formation of densely dispersed γ’-nanoparticles has a strong influence on the martensite variant selection and the morphology of martensite during stress-induced martensitic transformation. Relatively large, elongated particles promote irreversibility. In contrast, small spheroidal particles are associated with excellent functional stability during cyclic compression loading of 〈001〉-oriented single crystals. In addition to mechanical experiments, a detailed microstructural analysis was performed using in situ optical microscopy and neutron diffraction. Fundamental differences in microstructural evolution between various material states are documented and the relations between thermal treatment, microstructure and functional properties are explored and rationalized. © 2022 Acta Materialia Inc.
    view abstractdoi: 10.1016/j.actamat.2022.117623
  • 2022 • 708 A Novel Thermo-Mechanical Processing Route Exploiting Abnormal Grain Growth in Heusler-Type Co–Ni–Ga Shape Memory Alloys
    Lauhoff, C. and Pham, T. and Paulsen, A. and Krooß, P. and Frenzel, J. and Eggeler, G. and Niendorf, T.
    Metallurgical and Materials Transactions A: Physical Metallurgy and Materials Science 53 4139-4142 (2022)
    doi: 10.1007/s11661-022-06827-7
  • 2022 • 707 Particle Generation with Liquid Carbon Dioxide Emulsions
    Lauscher, C. and Schaldach, G. and Thommes, M.
    Chemical Engineering and Technology 45 1631-1636 (2022)
    Spray drying is a common technique for particle generation. However, due to limitations in the droplet size, the production of solid submicron particles using conventional atomizers has proven to be challenging. With the aim of overcoming this limitation, the generation and expansion of emulsions of an aqueous solution and liquid carbon dioxide with a subsequent drying step was investigated. Potassium chloride concentrations in the solution between 0.1 and 10 wt. % and mass loads of the aqueous disperse phase between 0.01 and 0.09 were used in order to study their impact on the droplet and particle size. For the lowest potassium chloride concentration, median particle diameters in the submicron size range were measured for all mass loads of the disperse phase. © 2022 The Authors. Chemical Engineering Technology published by Wiley-VCH GmbH.
    view abstractdoi: 10.1002/ceat.202200176
  • 2022 • 706 AN APPROACH FOR SMALL DROPLET PRODUCTION: NEBULIZATION BY EXPANSION OF WATER/LIQUID CARBON DIOXIDE EMULSIONS
    Lauscher, C. and Schaldach, G. and Thommes, M.
    Atomization and Sprays 32 77-93 (2022)
    Droplets in the small micrometer size range can be used in various applications such as spray drying for producing submicron-sized particles. Unfortunately, conventional atomizers are limited in their ability to produce droplets in the desired size range. To overcome this limitation, a nebulization process using the expansion of liquid carbon dioxide emulsions is presented. This approach is based on a high-pressure emulsion and a subsequent rapid expansion process, resulting in an aerosol. The investigation was conducted with deionized water as the disperse phase. For the emulsification process, water was injected into liquid carbon dioxide through an orifice. The influence of the nozzle diameter and the water mass load on the droplet size in the emulsion and the aerosol was investigated. Volumetric median droplet diameters in the emulsion were determined to have values between 180 and 730 µm. The nebulization of the water/liquid carbon dioxide emulsion led to an average droplet disintegration factor down to 0.007, which resulted in volumetric median droplet diameters in the aerosol smaller than 10 µm for all water mass loads. © 2022 by Begell House, Inc.
    view abstractdoi: 10.1615/ATOMIZSPR.2022039582
  • 2022 • 705 Molecular tweezers - a new class of potent broad-spectrum antivirals against enveloped viruses
    Le, M.-H. and Taghuo K., E.S. and Schrader, T.
    Chemical Communications 58 2954-2966 (2022)
    A new supramolecular approach to broad spectrum antivirals utilizes host guest chemistry between molecular tweezers and lysine/arginine as well as choline. Basic amino acids in amyloid-forming SEVI peptides (semen-derived enhancers of viral infection) are included inside the tweezer cavity leading to disaggregation and neutralization of the fibrils, which lose their ability to enhance HIV-1/HIV-2 infection. Lipid head groups contain the trimethylammonium cation of choline; this is likewise bound by molecular tweezers, which dock onto viral membranes and thus greatly enhance their surface tension. Disruption of the envelope in turn leads to total loss of infectiosity (ZIKA, Ebola, Influenza). This complexation event also seems to be the structural basis for an effective inihibition of cell-to-cell spread in Herpes viruses. The article describes the discovery of novel molecular recognition motifs and the development of powerful antiviral agents based on these host guest systems. It explains the general underlying mechanisms of antiviral action and points to future optimization and application as therapeutic agents. This journal is © The Royal Society of Chemistry
    view abstractdoi: 10.1039/d1cc06737k
  • 2022 • 704 Simple powerful robust tests based on sign depth
    Leckey, K. and Malcherczyk, D. and Horn, M. and Müller, C.H.
    Statistical Papers (2022)
    Up to now, powerful outlier robust tests for linear models are based on M-estimators and are quite complicated. On the other hand, the simple robust classical sign test usually provides very bad power for certain alternatives. We present a generalization of the sign test which is similarly easy to comprehend but much more powerful. It is based on K-sign depth, shortly denoted by K-depth. These so-called K-depth tests are motivated by simplicial regression depth, but are not restricted to regression problems. They can be applied as soon as the true model leads to independent residuals with median equal to zero. Moreover, general hypotheses on the unknown parameter vector can be tested. While the 2-depth test, i.e. the K-depth test for K= 2 , is equivalent to the classical sign test, K-depth test with K≥ 3 turn out to be much more powerful in many applications. A drawback of the K-depth test is its fairly high computational effort when implemented naively. However, we show how this inherent computational complexity can be reduced. In order to see why K-depth tests with K≥ 3 are more powerful than the classical sign test, we discuss the asymptotic behavior of its test statistic for residual vectors with only few sign changes, which is in particular the case for some alternatives the classical sign test cannot reject. In contrast, we also consider residual vectors with alternating signs, representing models that fit the data very well. Finally, we demonstrate the good power of the K-depth tests for some examples including high-dimensional multiple regression. © 2022, The Author(s).
    view abstractdoi: 10.1007/s00362-022-01337-5
  • 2022 • 703 A conservative Eulerian-Lagrangian decomposition principle for the solution of multi-scale flow problems at high Schmidt or Prandtl numbers
    Leer, M. and Pettit, M.W.A. and Lipkowicz, J.T. and Domingo, P. and Vervisch, L. and Kempf, A.M.
    Journal of Computational Physics 464 (2022)
    The simulation of turbulent flow that involves scalar transport at high Schmidt or Prandtl numbers is a major challenge. Enhanced Schmidt and Prandtl numbers demand an excessive increase in numerical resolution. Otherwise, the accuracy of transport would suffer substantially through unresolved information and numerical diffusion. With the aim of providing an efficient alternative for such applications, this paper presents a simulation method that is based on a novel Eulerian-Lagrangian decomposition principle (ELD) of the transported quantity. Low-pass filtering of the initial scalar quantity field separates it into a smooth low-frequency component and a fine-structured high-frequency component. The low-frequency component is represented and transported according to the Eulerian description by applying the Finite Volume Method (FVM) with a numerical resolution according to the Kolmogorov scale. The high-frequency component is translated into the Lagrangian description by the formation of particles, which are transported in parallel. By exchanging information between the two components, a re-initialisation mechanism ensures that the frequency-based decomposition is maintained throughout the simulation. Such ELD approach combines the efficiency of the FVM with the numerical stability of Lagrangian particles. As a result of the frequency-separation, the latter are by principle limited to zones of small scales and thus effectively complement the FVM. Furthermore, the particle information allows details of the scalar quantity field to be reconstructed that extend into the sub-grid level. By using a mixing layer setup, the proposed method is tested for a range of Schmidt numbers, and the numerical costs are considered and discussed. © 2022 Elsevier Inc.
    view abstractdoi: 10.1016/j.jcp.2022.111216
  • 2022 • 702 Metal-Corrole-Based Porous Organic Polymers for Electrocatalytic Oxygen Reduction and Evolution Reactions
    Lei, H. and Zhang, Q. and Liang, Z. and Guo, H. and Wang, Y. and Lv, H. and Li, X. and Zhang, W. and Apfel, U.-P. and Cao, R.
    Angewandte Chemie - International Edition 61 (2022)
    doi: 10.1002/anie.202201104
  • 2022 • 701 Publisher Correction: Dynamical photon–photon interaction mediated by a quantum emitter (Nature Physics, (2022), 18, 10, (1191-1195), 10.1038/s41567-022-01720-x)
    Le Jeannic, H. and Tiranov, A. and Carolan, J. and Ramos, T. and Wang, Y. and Appel, M.H. and Scholz, S. and Wieck, A.D. and Ludwig, Ar. and Rotenberg, N. and Midolo, L. and García-Ripoll, J.J. and Sørensen, A.S. and Lodahl, P.
    Nature Physics 18 1379 (2022)
    In the version of this article initially published, there was a citation error in the sixth paragraph, now reading in part, “The calculation of the two-photon response was obtained following an approach as outlined in ref. 43,” where ref. 43 (Ramos, T. & García-Ripoll, J. J. Phys. Rev. Lett. 119, 153601 (2017)) replaces the originally cited ref. 44 (Houck, M. et al. Phys. Rev. Lett. 124, 16051 (2020)), which has been removed from the reference list. The change has been made to the HTML and PDF versions of the article © 2022 The Author(s), under exclusive licence to Springer Nature Limited.
    view abstractdoi: 10.1038/s41567-022-01823-5
  • 2022 • 700 Lower degree of dissociation of pyruvic acid at water surfaces than in bulk
    Lesnicki, D. and Wank, V. and Cyran, J.D. and Backus, E.H.G. and Sulpizi, M.
    Physical Chemistry Chemical Physics 24 13510-13513 (2022)
    Understanding the acid/base behavior of environmentally relevant organic acids is of key relevance for accurate climate modelling. Here we investigate the effect of pH on the (de)protonation state of pyruvic acid at the air-water interface and in bulk by using the analytical techniques surface-specific vibrational sum frequency generation and attenuated total reflection spectroscopy. To provide a molecular interpretation of the observed behavior, simulations are carried out using a free energy perturbation approach in combination with electronic structure-based molecular dynamics. In both the experimental and theoretical results we observe that the protonated form of pyruvic acid is preferred at the air-water interface. The increased proton affinity is the result of the specific microsolvation at the interface. © 2022 The Royal Society of Chemistry
    view abstractdoi: 10.1039/d2cp01293f
  • 2022 • 699 Ab initio molecular dynamics simulation of vibrational energy relaxation at the solid/liquid interface: Charge defects at the fluorite/water interface allow very fast intermolecular vibrational energy transfer
    Lesnicki, D. and Sulpizi, M.
    High Performance Computing in Science and Engineering '20: Transactions of the High Performance Computing Center, Stuttgart (HLRS) 2020 87-99 (2022)
    The water/fluorite interface is of relevance to diverse industrial, environmental, and medical applications. In this contribution we review some of our recent results on the dynamics of water in contact with the solid calcium fluoride at low pH, where localised charge can develop upon fluorite dissolution. We use ab initio molecular dynamics simulations, including the full electronic structure, to simulate the vibrational energy relaxation and to quantify the heterogeneity of the interfacial water molecules. We find that strongly hydrogen-bonded OH groups display very rapid spectral diffusion and vibrational relaxation; for weakly H-bonded OD groups, the dynamics is instead much slower. Detailed analysis of the simulations reveals the molecular origin of energy transport through the local hydrogen-bond network. In particular, we find that the water molecules in the adsorbed layer, whose orientation is pinned by the localised charge defects, can exchange vibrational energy using just half a solvation shell, thanks to the strong dipole-dipole alignment between H-bond donor and acceptor. © The Author(s), under exclusive license to Springer Nature Switzerland AG 2021.
    view abstractdoi: 10.1007/978-3-030-80602-6_6
  • 2022 • 698 Identification of herbal teas and their compounds eliciting antiviral activity against SARS-CoV-2 in vitro
    Le-Trilling, V.T.K. and Mennerich, D. and Schuler, C. and Sakson, R. and Lill, J.K. and Kasarla, S.S. and Kopczynski, D. and Loroch, S. and Flores-Martinez, Y. and Katschinski, B. and Wohlgemuth, K. and Gunzer, M. and Meyer, F. an...
    BMC Biology 20 (2022)
    doi: 10.1186/s12915-022-01468-z
  • 2022 • 697 Predicting elastic properties of hard-coating alloys using ab-initio and machine learning methods
    Levämäki, H. and Tasnádi, F. and Sangiovanni, D.G. and Johnson, L.J.S. and Armiento, R. and Abrikosov, I.A.
    npj Computational Materials 8 (2022)
    doi: 10.1038/s41524-022-00698-7
  • 2022 • 696 Enhancing the phase change material properties by an energy-efficient one-step preparation method using organogelator-polyolefin composites
    Leven, F. and Limberg, J. and Noll, J. and Ulbricht, M. and Ostermann, R.
    Materials Advances (2022)
    The synergistic combination of various sorbitol-based organogelators with polyolefins allows the preparation of porous support structures for immobilized phase change materials (PCMs). Using a PCM as a solvent for the preparation leads to dimensionally stable composite materials with extremely high loading rates and low leakage of PCMs. Detailed investigations were performed on the kind of polyolefin support and its mass fraction concentration in the PCM, the temperature-dependent softening and failure under superimposed load, the efficiency of heat transport and the retention capacity over several melting/solidification cycles in various measurement setups. In particular, paraffin wax in combination with 1,2,3-trideoxy-4,6:5,7-bis-O-[(4-propylphenyl)methylene]-nonitol (TBPMN) and ultrahigh molecular weight polyethylene (UHMWPE) showed the best results in terms of high dimensional stability, low leakage, excellent processability and competitive heat capacity. The herein-established one-step preparation method saves time and energy compared to the loading of pre-formed porous supports and improves application-related properties at the same time. © 2022 RSC.
    view abstractdoi: 10.1039/d2ma00578f
  • 2022 • 695 Effect of microstructure heterogeneity on the mechanical properties of friction stir welded reduced activation ferritic/martensitic steel
    Li, S. and Vajragupta, N. and Biswas, A. and Tang, W. and Wang, H. and Kostka, A. and Yang, X. and Hartmaier, A.
    Scripta Materialia 207 (2022)
    The microhardness distribution in the different zones of a friction stir welded reduced activation ferritic/martensitic steel has been investigated and correlated to the hierarchical martensitic microstructure in the respective zones, characterized by electron backscatter diffraction orientation analysis. It is found that the variation of prior austenite grain size, packet size, and block width in different subzones is influenced by the peak temperature and effective strain rate during the friction stir welding process. The distribution of the microhardness correlates directly with the geometrically necessary dislocation density observed in the different zones. © 2021
    view abstractdoi: 10.1016/j.scriptamat.2021.114306
  • 2022 • 694 Bifacial semi-transparent ultra-thin Cu(In,Ga)Se2 solar cells on ITO substrate: How ITO thickness and Na doping influence the performance
    Li, Y. and Yin, G. and Schmid, M.
    Solar Energy Materials and Solar Cells 234 (2022)
    Ultra-thin Cu(In,Ga)Se2 (CIGSe) is a promising absorber for thin-film solar cells, as it combines the advantages of low raw material consumption and high conversion efficiency. In addition, ultra-thin absorbers on transparent back contacts bring the advantage of semitransparency, which is essential for e.g. tandem or bifacial solar cells. This work optimizes ultra-thin CIGSe on In2O3:Sn (ITO) for application in bifacial semi-transparent ultra-thin (BSTUT) CIGSe solar cells. Firstly, 100–400 nm ITO were coated onto glass substrates, and it was revealed that the thickness of ITO influences its optical bandgap Eg due to the Burstein-Moss (B-M) shift. The band gap of 400 nm ITO increased by 0.14 eV compared to the 100 nm thick ITO, and the Voc of the related BSTUT CIGSe solar cells raised by 0.043 V as a result of the diminished Schottky barrier Φb at the ITO/CIGSe interface. Secondly, 0–8 mg of NaF used for post deposition treatment (PDT) of the CIGSe were applied to the BSTUT solar cells. Compared to the reference without NaF, 8 mg NaF PDT enhanced the carrier density NA from 2 × 1015cm−3 to 1.2 × 1016cm−3 and diminished the ITO/CIGSe Schottky barrier Φb by 0.21 eV. In conclusion, we found that NaF PDT can tune the carrier density of ultra-thin CIGSe on ITO, and both thicker ITO and higher NaF PDT dose can reduce the ITO/CIGSe Schottky barrier. These discoveries enable future optimization of BSTUT CIGSe solar cells. © 2021 Elsevier B.V.
    view abstractdoi: 10.1016/j.solmat.2021.111431
  • 2022 • 693 Introducing Water-Network-Assisted Proton Transfer for Boosted Electrocatalytic Hydrogen Evolution with Cobalt Corrole
    Li, X. and Lv, B. and Zhang, X.-P. and Jin, X. and Guo, K. and Zhou, D. and Bian, H. and Zhang, W. and Apfel, U.-P. and Cao, R.
    Angewandte Chemie - International Edition 61 (2022)
    Proton transfer is vital for many biological and chemical reactions. Hydrogen-bonded water-containing networks are often found in enzymes to assist proton transfer, but similar strategy has been rarely presented by synthetic catalysts. We herein report the Co corrole 1 with an appended crown ether unit and its boosted activity for the hydrogen evolution reaction (HER). Crystallographic and 1H NMR studies proved that the crown ether of 1 can grab water via hydrogen bonds. By using protic acids as proton sources, the HER activity of 1 was largely boosted with added water, while the activity of crown-ether-free analogues showed very small enhancement. Inhibition studies by adding 1) external 18-crown-6-ether to extract water molecules and 2) potassium ion or N-benzyl-n-butylamine to block the crown ether of 1 further confirmed its critical role in assisting proton transfer via grabbed water molecules. This work presents a synthetic example to boost HER through water-containing networks. © 2021 Wiley-VCH GmbH
    view abstractdoi: 10.1002/anie.202114310
  • 2022 • 692 Co-doping of iron and copper ions in nanosized bioactive glass by reactive laser fragmentation in liquids
    Li, Y. and Ramesh, V. and Bider, F. and Bradshaw, N. and Rehbock, C. and Boccaccini, A.R. and Barcikowski, S.
    Journal of Biomedical Materials Research - Part A 110 1537-1550 (2022)
    doi: 10.1002/jbm.a.37393
  • 2022 • 691 Experimental investigation of laser surface texturing and related biocompatibility of pure titanium
    Li, H. and Wang, X. and Zhang, J. and Wang, B. and Breisch, M. and Hartmaier, A. and Rostotskyi, I. and Voznyy, V. and Liu, Y.
    International Journal of Advanced Manufacturing Technology (2022)
    While pure titanium is a material of choice for medical applications for its excellent mechanical and chemical properties, further improving its surface-related functionalities by surface texturing is also promising. In the present work, we experimentally investigate the fabrication, as well as the resulting functionalities of surface wettability and biocompatibility, of precise mesh-type surface textures on pure titanium by picosecond pulsed laser ablation operating at 1064 nm wavelength. Specifically, the dependence of microgroove morphology on average power and scanning speed is evaluated to yield optimized laser processing parameters, which are utilized to fabricate high precision mesh-type surface textures with uniform feature size and limited thermal effects on pure titanium. Subsequent performance evaluation tests demonstrate that the mesh-type surface textures induce a beneficial effect on the biocompatibility with respect to BMSC cells due to the enhanced hydrophilicity. © 2022, The Author(s), under exclusive licence to Springer-Verlag London Ltd., part of Springer Nature.
    view abstractdoi: 10.1007/s00170-022-08710-6
  • 2022 • 690 Elucidation of formation and transformation mechanisms of Ca-rich Laves phase in Mg-Al-Ca-Mn alloys
    Li, J. and Zhou, X. and Breen, A. and Peng, Z. and Su, J. and Kürnsteiner, P. and Correa, M.J.D. and Chwałek, M.L. and Wang, H. and Holec, D. and Mayer, J. and Dehm, G.
    Journal of Alloys and Compounds 928 (2022)
    doi: 10.1016/j.jallcom.2022.167177
  • 2022 • 689 Elucidating dynamic precipitation and yield strength of rolled Mg–Al–Ca–Mn alloy
    Li, J. and Zhou, X. and Su, J. and Breitbach, B. and Chwałek, M.L. and Wang, H. and Dehm, G.
    Materials Science and Engineering A 856 (2022)
    doi: 10.1016/j.msea.2022.143898
  • 2022 • 688 Beyond Light-Trapping Benefits: The Effect of SiO2 Nanoparticles in Bifacial Semitransparent Ultrathin Cu(In,Ga)Se2 Solar Cells
    Li, Y. and Tabernig, S.W. and Yin, G. and Polman, A. and Schmid, M.
    Solar RRL 6 (2022)
    Bifacial semitransparent ultrathin Cu(In,Ga)Se2 solar cells (BSTUT CIGSe SCs) enable efficient usage of light and reduced raw material. By inserting the SiO2 nanoparticles (NPs) at the CIGSe/back–contact interface, this work optimizes the performance of BSTUT SCs under front and especially rear illumination, which has not been studied much so far. For the SCs with NPs, the short-circuit current density increases by 4.1–4.4 mA cm−2 for front and by 6.4–7.4 mA cm−2 for rear illumination. In addition, a significantly improved fill factor for rear illumination highlights a benefit of the NPs beyond light trapping. A jet-like focusing behind the NPs is observed, which in this case leads to a higher field localization near the pn junction, joint with an enhanced carrier generation and separation. Furthermore, a thinner In2O3:Sn (ITO) back contact is noticed to be favorable for effective light trapping, whereas thicker ITO is preferred for higher open-circuit voltage. Overall, inserting NPs in BSTUT SCs is an effective and practical strategy to achieve a higher cost-to-efficiency ratio in photovoltaic device production. In our case, a maximum of 12.2% under front and 9.2% under rear illumination is achieved leading to a calculated bifacial efficiency of 15% for the ultrathin device. © 2022 Wiley-VCH GmbH.
    view abstractdoi: 10.1002/solr.202200695
  • 2022 • 687 Ultrathin Cu(In,Ga)Se2Solar Cells with a Passivated Back Interface: A Comparative Study between Mo and In2O3:Sn Back Contacts
    Li, Y. and Yin, G. and Tu, Y. and Sedaghat, S. and Gao, Y. and Schmid, M.
    ACS Applied Energy Materials 5 7956-7964 (2022)
    Point-contact passivation layers have been proven beneficial in most solar cells (SCs). However, the latest theoretical simulations suggested that a high back-contact recombination velocity Sbcan also be beneficial in ultrathin CIGSe (Cu(In,Ga)Se2) SCs if they have a relatively high back potential barrier height Eh. SCAPS simulations predicted that a high Sbwill deteriorate the SC efficiency Eff when Ehis in the range of 0-0.17 eV (Ohmic contact). Yet, when Ehis greater than 0.17 eV (Schottky contact), a high Sbcan also diminish the current limitation arising from the back Schottky diode since it has a reverse direction to the main p-n junction. Therefore, a high Sbcan support the carriers in passing the Schottky barrier via recombination, thus enhancing the cell performance. This work aims to verify the simulation prediction in practical experiments. To achieve different Sbvalues, we fabricate SiO2passivation layers with point contacts of various dimensions by nanosphere lithography. The passivation effects are studied comparatively on Mo and ITO (In2O3:Sn) back contacts. The emphasis is on Eh, which is marginal for Mo but acts Schottky-like on ITO. We show that for Mo-based solar cells, the Ehis trivial; hence, a high Sb(without SiO2passivation) deteriorates the efficiency. In contrast, on ITO, the reference sample without SiO2shows less current limitation than the passivated ones, implying that a high Sbimproves the efficiency. Comparing the differences of SiO2on Mo and ITO back contacts in experiments, with the contrasting behavior of Sbon Ohmic and Schottky contacts in simulation, we conclude that Ehdecides about the role of Sbin ultrathin CIGSe SCs. These findings deepen the understanding of the Schottky back contact and pave the way for future optimization of bifacial semitransparent ultrathin CIGSe SCs. © 2022 American Chemical Society. All rights reserved.
    view abstractdoi: 10.1021/acsaem.2c00088
  • 2022 • 686 Synthesis and redox activity of carbene-coordinated group 13 metal radicals
    Li, B. and Geoghegan, B.L. and Weinert, H.M. and Wölper, C. and Cutsail, G.E. and Schulz, S.
    Chemical Communications 58 4372-4375 (2022)
    Carbenes are known to stabilize main group element compounds with unusual electronic properties. Herein, we report the synthesis of carbene-stabilized group 13 metal radicals (cAAC)MX2(IPr) (M = Al, X = Br 3; M = Ga, X = Cl 4) and the corresponding cations [(cAAC)MX2(IPr)][B(C6F5)4] (M = Al, X = Br 5; M = Ga, X = Cl 6), which were characterized spectroscopically and by sc-XRD. Quantum chemical calculation gave insights into their electronic structures. © 2022 The Royal Society of Chemistry
    view abstractdoi: 10.1039/d2cc00216g
  • 2022 • 685 C−Br Bond Activation of Bromoalkanes with Gallanediyl LGa
    Li, B. and Wölper, C. and Schulz, S.
    Zeitschrift fur Anorganische und Allgemeine Chemie (2022)
    Monovalent group 13 diyls are promising reagents for C−X bond activation. We here report on C−Br bond activation reactions of gallanediyl LGa (L=HC[C(Me)NAr)]2, Ar=2,6-i-Pr2C6H3)) with a variety of bromoalkanes. Reactions with alkylbromides R−Br gave the corresponding LGa(Br)R (R=Et 1, n-Pr 2, i-Pr 3), while the reaction with dibromomethane in 2 : 1 molar ratio occurred with geminal C−Br bond addition and formation of [LGa(Br)]2CH2 (4). In contrast, equimolar reaction of LGa with CHBr3 yielded LGa(Br)CHBr2 (5), which reacted with another equiv. of LGa with decomposition and formation of LGaBr2. Compounds 1–5 were characterized by heteronuclear (1H, 13C) NMR and IR spectroscopy, as well as single-crystal X-ray diffraction (sc-XRD). © 2022 The Authors. Zeitschrift für anorganische und allgemeine Chemie published by Wiley-VCH GmbH.
    view abstractdoi: 10.1002/zaac.202200293
  • 2022 • 684 Microstructural evolution of Cu/W nano-multilayers filler metal during thermal treatment
    Li, H. and Xing, Z.-C. and Li, B.-J. and Liu, X.-S. and Lehmert, B. and Matthias, M. and Li, Z.-X. and Tillmann, W.
    Vacuum 200 (2022)
    Copper/Tungsten (Cu/W) nano-multilayers show potential for application as novel low-temperature brazing filler metals. Therefore, researchers are interested in understanding phase stability and microstructural evolution of the nano-multilayers during thermal treatment. A repetition of 50 alternating nanolayers of Cu and W with individual thicknesses of 10 nm were prepared by magnetron-sputtering on silicon substrates. The structural evolution of Cu/W nano-multilayers (NMLs) within the temperature range 400 °C–800 °C was monitored using real-time in-situ XRD, SEM, TEM, SAXS, DSC and in-house XRD system. The results showed that the melting point of Cu/W nano-multilayers determined using DSC was 793.694 °C was remarkably lower than the melting point of bulk Cu(1083 °C) and W (3140 °C). After annealing at 400 °C for 30 min, the surface of the NMLs exhibited more copper grains, with significant coarsening of the copper grains. The layered structure of the Cu/W NMLs was unaffected after annealed at 400 °C. When annealed at 600 °C for 30 min, some Cu particles migrated into the W layers along the internal interface leading to cracks which partially collapsed the original stratified structure. The nano-multilayered structure was completely destroyed when annealed at 800 °C. Further, the in-situ XRD results showed that the copper grains grew substantially, while the tungsten size remained unchanged with increasing temperature. © 2022
    view abstractdoi: 10.1016/j.vacuum.2022.111007
  • 2022 • 683 Atomic-scale characterization of (electro-)catalysts and battery materials by atom probe tomography
    Li, T. and Devaraj, A. and Kruse, N.
    Cell Reports Physical Science 3 (2022)
    doi: 10.1016/j.xcrp.2022.101188
  • 2022 • 682 Experimental investigation on the effect of fluid-structure interaction on unsteady cavitating flows around flexible and stiff hydrofoils
    Lin, Y. and Kadivar, E. and El Moctar, O. and Neugebauer, J. and Schellin, T.E.
    Physics of Fluids 34 (2022)
    doi: 10.1063/5.0099776
  • 2022 • 681 An Investigation of Antecedents for Data Governance Adoption in the Rail Industry—Findings From a Case Study at Thales
    Lis, D. and Arbter, M. and Spindler, M. and Otto, B.
    IEEE Transactions on Engineering Management 1-18 (2022)
    The role of data governance is experiencing a paradigm shift as organizations increasingly incorporate data governance to encourage the strategic utilization of data and, therefore, promote data-driven innovation. However, the opportunities arising from technological advancements and novel value propositions based on data come with implications that often stem from external and internal contingent factors, e.g., industry characteristics or organizational structures. In combination with inadequate practices regarding the conduct of data, difficulties in the adoption of data governance can increase. This article draws upon established practices from information technology governance and organizational theory, specifically contingency theory, to examine occurring antecedents in the adoption of data governance at Thales Ground Transportation Systems, a manufacturer of solutions for the railway infrastructure. By investigating the nomological link between antecedents, adoption, and consequences, associated implications for data governance can be taken into account in early phases of adoption to promote data-driven innovation. The article proposes new antecedents evolving from interorganizational dynamics such as data collaborations in the respective ecosystem. IEEE
    view abstractdoi: 10.1109/TEM.2022.3166109
  • 2022 • 680 In situ measurement of gas-borne silicon nanoparticle volume fraction and temperature by spatially and spectrally line-resolved attenuation and emission imaging
    Liu, G. and Asif, M. and Mohri, K. and Schulz, C. and Dreier, T. and Endres, T. and Menser, J.
    Powder Technology 396 535-541 (2022)
    In this study, the temperature and volume fraction distributions of liquid silicon nanoparticles in the aerosol flow in gas-phase synthesis were retrieved using tomographic reconstruction of emission and extinction spectra in the 230–700 nm range. Measurements were done in an optically accessible microwave-plasma flow reactor fed with a SiH4/H2/Ar gas mixture. Optical emission and extinction spectra in the visible spectral range were captured along a line perpendicular to the flow direction covering the entire cross-section of the Si particle stream. Particle temperature and volume fraction distributions were determined and the preferred location of the silicon particles in a 1-mm thick zone at the circumference of the cylindric flow was revealed. The combined recording of line-resolved emission/extinction spectra is a promising method for spatially-resolved detection of nanoparticles in combustion or gas-phase synthesis. © 2021 Elsevier B.V.
    view abstractdoi: 10.1016/j.powtec.2021.11.017
  • 2022 • 679 Massive interstitial solid solution alloys achieve near-theoretical strength
    Liu, C. and Lu, W. and Xia, W. and Du, C. and Rao, Z. and Best, J.P. and Brinckmann, S. and Lu, J. and Gault, B. and Dehm, G. and Wu, G. and Li, Z. and Raabe, D.
    Nature Communications 13 (2022)
    Interstitials, e.g., C, N, and O, are attractive alloying elements as small atoms on interstitial sites create strong lattice distortions and hence substantially strengthen metals. However, brittle ceramics such as oxides and carbides usually form, instead of solid solutions, when the interstitial content exceeds a critical yet low value (e.g., 2 at.%). Here we introduce a class of massive interstitial solid solution (MISS) alloys by using a highly distorted substitutional host lattice, which enables solution of massive amounts of interstitials as an additional principal element class, without forming ceramic phases. For a TiNbZr-O-C-N MISS model system, the content of interstitial O reaches 12 at.%, with no oxides formed. The alloy reveals an ultrahigh compressive yield strength of 4.2 GPa, approaching the theoretical limit, and large deformability (65% strain) at ambient temperature, without localized shear deformation. The MISS concept thus offers a new avenue in the development of metallic materials with excellent mechanical properties. © 2022, The Author(s).
    view abstractdoi: 10.1038/s41467-022-28706-w
  • 2022 • 678 Terahertz Beam Steering Using a MEMS-Based Reflectarray Configured by a Genetic Algorithm
    Liu, X. and Schmitt, L. and Sievert, B. and Lipka, J. and Geng, C. and Kolpatzeck, K. and Erni, D. and Rennings, A. and Balzer, J.C. and Hoffmann, M. and Czylwik, A.
    IEEE Access 10 84458-84472 (2022)
    doi: 10.1109/ACCESS.2022.3197202
  • 2022 • 677 CALPHAD-informed phase-field model for two-sublattice phases based on chemical potentials: η-phase precipitation in Al-Zn-Mg-Cu alloys
    Liu, C. and Davis, A. and Fellowes, J. and Prangnell, P.B. and Raabe, D. and Shanthraj, P.
    Acta Materialia 226 (2022)
    The electrochemical properties of high strength 7xxx aluminium alloys strongly depend on the substitutional occupancy of Zn by Cu and Al in the strengthening η-phase with the two-sublattice structure, and its microstructural and compositional prediction is the key to design of new generation corrosion resistant alloys. In this work, we have developed a chemical-potential-based phase-field model capable of describing multi-component and two-sublattice ordered phases, during commercial multi-stage artificial ageing treatments, by directly incorporating the compound energy CALPHAD formalism. The model developed has been employed to explore the complex compositional pathway for the formation of the η-phase in Al-Zn-Mg-Cu alloys during heat treatments. In particular, the influence of alloy composition, solute diffusivity, and heat treatment parameters on the microstructural and compositional evolution of η-phase precipitates, was systematically investigated from a thermodynamic and kinetic perspective and compared to electron probe microanalysis validation data. The simulated η-phase growth kinetics and the matrix residual solute evolution in the AA7050 alloy indicates that Zn depletion mainly controlled the η-phase growth process during the early stage of ageing, resulting in fast η-phase growth kinetics, enrichment of Zn in the η-phase, and an excess in residual Cu in the matrix. The gradual substitution of Zn by Cu atoms in the η-phase during the later ageing stage was in principle a kinetically controlled process, owing to the slower diffusivity of Cu relative to Zn in the matrix. It was also found that the higher nominal Zn content in alloys like the AA7085 alloy, compared to the AA7050 alloy, could significantly enhance the chemical potential of Zn, but this had a minor influence on Cu, which essentially led to the higher Zn content (and consequently lower Cu) seen in the η-phase. Finally, substantial depletion of Zn and supersaturation of Cu in the matrix of the AA7050 alloy was predicted after 24 h ageing at 120 ∘C, whereas the second higher-temperature ageing stage at 180 ∘C markedly enhanced the diffusion of Cu from the supersaturated matrix into the η-phase, while the matrix residual Zn content was only slightly affected. © 2021 The Author(s)
    view abstractdoi: 10.1016/j.actamat.2021.117602
  • 2022 • 676 Optimizing the Radiation Pattern of a MEMS-Based Reflectarray Using a Genetic Algorithm for Beam Steering Applications
    Liu, X. and Schmitt, L. and Lipka, J. and Kolpatzeck, K. and Balzer, J.C. and Hoffmann, M. and Czylwik, A.
    International Conference on Infrared, Millimeter, and Terahertz Waves, IRMMW-THz 2022-August (2022)
    doi: 10.1109/IRMMW-THz50927.2022.9895897
  • 2022 • 675 Facet-Dependent Intrinsic Activity of Single Co3O4 Nanoparticles for Oxygen Evolution Reaction
    Liu, Z. and Amin, H.M.A. and Peng, Y. and Corva, M. and Pentcheva, R. and Tschulik, K.
    Advanced Functional Materials (2022)
    Deciphering the influence of nanocatalyst morphology on their catalytic activity in the oxygen evolution reaction (OER), the limiting reaction in water splitting process, is essential to develop highly active precious metal-free catalysts, yet poorly understood. The intrinsic OER activity of Co3O4 nanocubes and spheroids is probed at the single particle level to unravel the correlation between exposed facets, (001) vs. (111), and activity. Single cubes with predominant (001) facets show higher activity than multi-faceted spheroids. Density functional theory calculations of different terminations and reaction sites at (001) and (111) surfaces confirm the higher activity of the former, expressed in lower overpotentials. This is rationalized by a change in the active site from octahedral to tetrahedral Co and the potential-determining step from *OH to *O for the cases with lowest overpotentials at the (001) and (111) surfaces, respectively. This approach enables the identification of highly active facets to guide shape-selective syntheses of improved metal oxide nanocatalysts for water oxidation. © 2022 The Authors. Advanced Functional Materials published by Wiley-VCH GmbH.
    view abstractdoi: 10.1002/adfm.202210945
  • 2022 • 674 Probing magnetic anisotropy in Kagome antiferromagnetic Mn3Ge with torque magnetometry
    Liu, Y.S. and Xiao, H. and Yu, A.B. and Wu, Y.F. and Manna, K. and Felser, C. and Schneider, C.M. and Xie, H.-Y. and Hu, T.
    Journal of Magnetism and Magnetic Materials 563 (2022)
    We investigate the magnetic symmetry of the topological antiferromagnetic material Mn3Ge by torque measurements. Below the Néel temperature, detailed angle-dependent torque measurements were performed on Mn3Ge single crystals in directions parallel and perpendicular to the Kagome basal plane. The out-of plane torque data exhibit ±sinθ and sin2θ behaviors, of which the former results from the spontaneous ferromagnetism within the basal plane and the latter from the in- and out-of-plane susceptibility anisotropy. The reversible component of the in-plane torque exhibits sin6φ behavior, revealing the six-fold symmetry of the in-plane magnetic free energy. Moreover, we find that the free energy minima are pinned to the direction of spontaneous ferromagnetism, which corresponds to the maxima of the irreversible component of the in-plane torque. We provide an effective spin model to describe the in-plane magnetic anisotropy. Our results demonstrate that the ground state of Mn3Ge is described by the coexistence of a strong six-fold antichiral order and a weak ferromagnetic order induced by second-order spin anisotropy. © 2022
    view abstractdoi: 10.1016/j.jmmm.2022.170018
  • 2022 • 673 Sintering of Li-garnets: Impact of Al-incorporation and powder-bed composition on microstructure and ionic conductivity
    Lobe, S. and Bauer, A. and Sebold, D. and Wettengl, N. and Fattakhova-Rohlfing, D. and Uhlenbruck, S.
    Open Ceramics 10 (2022)
    doi: 10.1016/j.oceram.2022.100268
  • 2022 • 672 A deterministic source of single photons
    Lodahl, P. and Ludwig, Ar. and Warburton, R.J.
    Physics Today 75 44-50 (2022)
    doi: 10.1063/PT.3.4962
  • 2022 • 671 Development of a Hot Cutting Process for Functional Parts by Stress State-Dependent Damage Modeling
    Löbbe, C. and Martschin, J. and Putschkat, D. and Sulaiman, H. and Jäger, A. and Tekkaya, A.E.
    Minerals, Metals and Materials Series 511-521 (2022)
    doi: 10.1007/978-3-031-06212-4_47
  • 2022 • 670 Role of surface structures on long term stability of adhesive joints between Ti–15V–3Cr–3Sn–3Al and polyether-ether-ketone
    Löbbecke, M. and Bayerbasi, T.J. and Bartsch, M. and Haubrich, J.
    International Journal of Adhesion and Adhesives (2022)
    doi: 10.1016/j.ijadhadh.2022.103282
  • 2022 • 669 SoC for Retinal Ganglion Cell Stimulation with Integrated Sinusoidal Kilohertz Frequency Waveform Generation
    Lohler, P. and Pickhinke, A. and Erbsloh, A. and Kokozinski, R. and Seidl, K.
    PRIME 2022 - 17th International Conference on Ph.D Research in Microelectronics and Electronics, Proceedings 341-344 (2022)
    For retinal prostheses strategies to increase the stimulative cell selectivity are required to generate neural responses to electrical stimulation of retinal ganglion cells (RGCs) that match the response of the natural signal pathway. An important part of these strategies is the modulation of stimulus amplitude and frequency in the kilohertz range. The aim of this research is to investigate the electronic challenges and requirements of new electrical stimulation strategies for future retinal implants. This paper presents a 42 channel current controlled stimulator which is able to stimulate retinal tissue with sinusoidal frequencies higher than 1 kHz at amplitudes of up to 200 µ A. The power efficiency of the stimulator is 87.3% at a supply voltage of 1.8 V. One stimulator requires a respective area of 0.0071 mm2 by using a 180 nm CMOS technology. © 2022 IEEE.
    view abstractdoi: 10.1109/PRIME55000.2022.9816766
  • 2022 • 668 Fourier analysis of a time-simultaneous two-grid algorithm using a damped Jacobi waveform relaxation smoother for the one-dimensional heat equation
    Lohmann, C. and Dünnebacke, J. and Turek, S.
    Journal of Numerical Mathematics 30 173-207 (2022)
    In this work, the convergence behavior of a time-simultaneous two-grid algorithm for the one-dimensional heat equation is studied using Fourier arguments in space. The underlying linear system of equations is obtained by a finite element or finite difference approximation in space while the semi-discrete problem is discretized in time using the θ-scheme. The simultaneous treatment of all time instances leads to a global system of linear equations which provides the potential for a higher degree of parallelization of multigrid solvers due to the increased number of degrees of freedom per spatial unknown. It is shown that the all-at-once system based on an equidistant discretization in space and time stays well conditioned even if the number of blocked time-steps grows arbitrarily. Furthermore, mesh-independent convergence rates of the considered two-grid algorithm are proved by adopting classical Fourier arguments in space without assuming periodic boundary conditions. The rate of convergence with respect to the Euclidean norm does not deteriorate arbitrarily if the number of blocked time steps increases and, hence, underlines the potential of the solution algorithm under investigation. Numerical studies demonstrate why minimizing the spectral norm of the iteration matrix may be practically more relevant than improving the asymptotic rate of convergence. © 2022 Walter de Gruyter GmbH, Berlin/Boston.
    view abstractdoi: 10.1515/jnma-2021-0045
  • 2022 • 667 Computational Pourbaix Diagrams for MXenes: A Key Ingredient toward Proper Theoretical Electrocatalytic Studies
    López, M. and Exner, K.S. and Viñes, F. and Illas, F.
    Advanced Theory and Simulations (2022)
    doi: 10.1002/adts.202200217
  • 2022 • 666 Exploring the Si-precursor composition for inline coating and agglomeration of TiO2 via modular spray-flame and plasma reactor
    López-Cámara, C.-F. and Dasgupta, M. and Fortugno, P. and Wiggers, H.
    Proceedings of the Combustion Institute (2022)
    Inline particle coating after the particle formation process to preserve its specific properties is hardly investigated scientifically. Tackling that issue, we have studied the use of three different vaporized organo-siloxanes (tetraethyl orthosilicate TEOS, hexamethyldisiloxane HMDSO, and octamethylcyclotetrasiloxane OMCTS) as precursors for direct inline coating of pristine titanium dioxide (TiO2) nanoparticles made via spray-flame synthesis. The inline silica (SiO2) coating of the formed titanium dioxide nanoparticles is achieved by vaporizing and sending the chosen organo-siloxane precursors into a cylindrical coating nozzle downstream the particle formation zone of the spray-flame. To further explore the effects on morphology and the quality of the resultant TiO2|SiO2 core-shell nanoparticles, a plasma discharge - i.e., dielectric barrier discharge source - is applied after the coating step. The TiO2|SiO2 core-shell nanoparticles are characterized using Transmission Electron Microscopy (TEM) and Scanning Transmission Electron Microscopy (STEM), X-Ray Diffraction (XRD), Fourier-Transform InfraRed spectroscopy (FTIR), Brunauer-Emmett-Teller surface area analysis (BET), elemental analysis, and dynamic light scattering (DLS). Results showed distinct core-shell nanoparticles with shell thicknesses of around 1.5 nm alongside the formation of unattached SiO2 nanoparticles due to homogenous nucleation of SiO2. As the precursor silicon content increased (TEOS &lt; HMDSO &lt; OMCTS), the homogenous nucleation rose to generate materials with high BET surface areas. When employing OMCTS, the high homogeneous nucleation rate led to SiO2 agglomeration, which resulted in large TiO2|SiO2 agglomerates. Morphologically, the phase composition of anatase/rutile of the produced coated nanoparticles did not vary significantly when compared with the reference uncoated TiO2 nanoparticles, indicating that the SiO2 coating is purely a surface phenomenon. Plasma discharge was shown to reduce coated particle agglomeration up to certain extend. Based on these findings, we conclude that the best studied parameters to benefit the synthesis of homogeneously coated TiO2|SiO2 nanoparticles are (i) using TEOS as a coating precursor to minimize SiO2 homogeneous nucleation and (ii) applying a plasma discharge to slightly reduce coated particle agglomeration. © 2022 Elsevier Ltd. All rights reserved.
    view abstractdoi: 10.1016/j.proci.2022.07.137
  • 2022 • 665 Toward Zero Variance in Proteomics Sample Preparation: Positive-Pressure FASP in 96-Well Format (PF96) Enables Highly Reproducible, Time- and Cost-Efficient Analysis of Sample Cohorts
    Loroch, S. and Kopczynski, D. and Schneider, A.C. and Schumbrutzki, C. and Feldmann, I. and Panagiotidis, E. and Reinders, Y. and Sakson, R. and Solari, F.A. and Vening, A. and Swieringa, F. and Heemskerk, J.W.M. and Grandoch, M. ...
    Journal of Proteome Research 21 1181-1188 (2022)
    As novel liquid chromatography-mass spectrometry (LC-MS) technologies for proteomics offer a substantial increase in LC-MS runs per day, robust and reproducible sample preparation emerges as a new bottleneck for throughput. We introduce a novel strategy for positive-pressure 96-well filter-aided sample preparation (PF96) on a commercial positive-pressure solid-phase extraction device. PF96 allows for a five-fold increase in throughput in conjunction with extraordinary reproducibility with Pearson product-moment correlations on the protein level of r = 0.9993, as demonstrated for mouse heart tissue lysate in 40 technical replicates. The targeted quantification of 16 peptides in the presence of stable-isotope-labeled reference peptides confirms that PF96 variance is barely assessable against technical variation from nanoLC-MS instrumentation. We further demonstrate that protein loads of 36-60 μg result in optimal peptide recovery, but lower amounts ≥3 μg can also be processed reproducibly. In summary, the reproducibility, simplicity, and economy of time provide PF96 a promising future in biomedical and clinical research. © 2022 American Chemical Society. All rights reserved.
    view abstractdoi: 10.1021/acs.jproteome.1c00706
  • 2022 • 664 Combinatorial sputter deposition of CrMnFeCoNi high entropy alloy thin films on agitated particles
    Lourens, F. and Ludwig, Al.
    Surface and Coatings Technology 449 (2022)
    A method for combinatorial sputter deposition of thin films on microparticles is presented. The method is developed for a laboratory-scale magnetron sputter system and uses a piezoelectric actuator to agitate the microparticles through oscillation. Custom-made components enable to agitate up to nine separate batches of particles simultaneously. Due to the agitation, the whole surface of the particles can be exposed to the sputter flux and thus completely covered with a thin film. By sputtering a CrMnFeCoNi high entropy alloy target, separate batches of polystyrene microspheres (500 μm monodisperse diameter), Fe alloy particles (300 μm mean size) and NaCl salt particles (350 μm mean size) were simultaneously coated with a homogeneous thin film. In contrast, a CrMnFeCoNi thin film that was deposited on agglomerating Al particles (5 μm mean size) only partially covers the surface of the particles. By co-sputtering a CrMn, an FeCo and a Ni target, nine separate batches of Al particles (25 μm mean size) were coated with a CrMnFeCoNi thin film with a composition gradient. These depositions demonstrate the ability to coat different types of particles with uniform films (from elemental to multinary compositions) and to deposit films with composition gradients on uniform particles. © 2022 Elsevier B.V.
    view abstractdoi: 10.1016/j.surfcoat.2022.128984
  • 2022 • 663 Survey of Zirconium-Containing NaSICON-type Solid-State Li+ Ion Conductors with the Aim of Increasing Reduction Stability by Partial Cation Substitution
    Loutati, A. and Odenwald, P. and Aktekin, B. and Sann, J. and Guillon, O. and Tietz, F. and Fattakhova-Rohlfing, D.
    Batteries and Supercaps 5 (2022)
    doi: 10.1002/batt.202200327
  • 2022 • 662 NaSICON-type solid-state Li+ ion conductors with partial polyanionic substitution of phosphate with silicate
    Loutati, A. and Guillon, O. and Tietz, F. and Fattakhova-Rohlfing, D.
    Open Ceramics 12 (2022)
    doi: 10.1016/j.oceram.2022.100313
  • 2022 • 661 Elevated-temperature cyclic deformation mechanisms of CoCrNi in comparison to CoCrFeMnNi
    Lu, K. and Knöpfle, F. and Chauhan, A. and Litvinov, D. and Schneider, M. and Laplanche, G. and Aktaa, J.
    Scripta Materialia 220 (2022)
    We report the cyclic deformation behavior of CoCrNi at 550 °C under a strain amplitude of ± 0.5% and compare it to that of CoCrFeMnNi. CoCrNi manifests cyclic hardening followed by minor softening and a near-steady state until failure. Transmission electron microscopy investigations of CoCrNi revealed that increasing the number of cycles from 10 to 2500/5000 leads to a transition of dislocation arrangements from slip bands to tangles. Compared to CoCrFeMnNi, CoCrNi exhibits higher strength, longer lifetime and persistent serrated flow. Owing to its lower stacking fault energy (even at 550 °C), planar slip is more pronounced in CoCrNi than CoCrFeMnNi, which additionally shows wavy slip. © 2022 Acta Materialia Inc.
    view abstractdoi: 10.1016/j.scriptamat.2022.114926
  • 2022 • 660 Photonic Integrated Circuit for Optical Phase Control of 1 × 4 Terahertz Phased Arrays
    Lu, P. and Haddad, T. and Tebart, J. and Roeloffzen, C. and Stöhr, A.
    Photonics 9 (2022)
    doi: 10.3390/photonics9120902
  • 2022 • 659 Understanding the Thickness and Light-Intensity Dependent Performance of Green-Solvent Processed Organic Solar Cells
    Lübke, D. and Hartnagel, P. and Hülsbeck, M. and Kirchartz, T.
    ACS Materials Au (2022)
    doi: 10.1021/acsmaterialsau.2c00070
  • 2022 • 658 Giant effective Zeeman splitting in a monolayer semiconductor realized by spin-selective strong light–matter coupling
    Lyons, T.P. and Gillard, D.J. and Leblanc, C. and Puebla, J. and Solnyshkov, D.D. and Klompmaker, L. and Akimov, I.A. and Louca, C. and Muduli, P. and Genco, A. and Bayer, M. and Otani, Y. and Malpuech, G. and Tartakovskii, A.I.
    Nature Photonics 16 632-636 (2022)
    doi: 10.1038/s41566-022-01025-8
  • 2022 • 657 Numerical assessment of the effects of a porous medium in transient sloshing-induced impulsive hydrodynamics
    Lyu, W. and el Moctar, O. and Schellin, T.E. and Delgado, A.
    Ocean Engineering 265 (2022)
    doi: 10.1016/j.oceaneng.2022.112508
  • 2022 • 656 Investigations of transient sloshing induced impulsive hydrodynamics
    Lyu, W. and el Moctar, O. and Schellin, T.
    Ocean Engineering 258 (2022)
    doi: 10.1016/j.oceaneng.2022.111524
  • 2022 • 655 Ship motion-sloshing interaction with forward speed in oblique waves
    Lyu, W. and Moctar, O.E. and Schellin, T.E.
    Ocean Engineering 250 (2022)
    doi: 10.1016/j.oceaneng.2022.110999
  • 2022 • 654 Hierarchical nature of hydrogen-based direct reduction of iron oxides
    Ma, Y. and Souza Filho, I.R. and Bai, Y. and Schenk, J. and Patisson, F. and Beck, A. and van Bokhoven, J.A. and Willinger, M.G. and Li, K. and Xie, D. and Ponge, D. and Zaefferer, S. and Gault, B. and Mianroodi, J.R. and Raabe, D.
    Scripta Materialia (2022)
    Fossil-free ironmaking is indispensable for reducing massive anthropogenic CO2 emissions in the steel industry. Hydrogen-based direct reduction (HyDR) is among the most attractive solutions for green ironmaking, with high technology readiness. The underlying mechanisms governing this process are characterized by a complex interaction of several chemical (phase transformations), physical (transport), and mechanical (stresses) phenomena. Their interplay leads to rich microstructures, characterized by a hierarchy of defects ranging across several orders of magnitude in length, including vacancies, dislocations, internal interfaces, and free surfaces in the form of cracks and pores. These defects can all act as reaction, nucleation, and diffusion sites, shaping the overall reduction kinetics. A clear understanding of the roles and interactions of these dynamically-evolving nano-/microstructure features is missing. Gaining better insights into these effects could enable improved access to the microstructure-based design of more efficient HyDR methods, with potentially high impact on the urgently needed decarbonization in the steel industry. © 2022 The Author(s)
    view abstractdoi: 10.1016/j.scriptamat.2022.114571
  • 2022 • 653 Impact of Climate Change on Drinking Water Safety
    Ma, B. and Hu, C. and Zhang, J. and Ulbricht, M. and Panglisch, S.
    ACS Environmental Science and Technology Water 2 259-261 (2022)
    Widespread, rapid, and intensifying climate change plays an important role in drinking water quality. By scientifically exploring the interrelated mechanisms between climate change and drinking water quality, professionals can better adapt and optimize the water management and thereby ensure drinking water safety. Here, a new concept regarding water quality under the conditions of climate change is proposed due to the potential long-time and far-reaching impacts. © 2022 American Chemical Society
    view abstractdoi: 10.1021/acsestwater.2c00004
  • 2022 • 652 Enhancing the Dendrite Tolerance of NaSICON Electrolytes by Suppressing Edge Growth of Na Electrode along Ceramic Surface
    Ma, Q. and Ortmann, T. and Yang, A. and Sebold, D. and Burkhardt, S. and Rohnke, M. and Tietz, F. and Fattakhova-Rohlfing, D. and Janek, J. and Guillon, O.
    Advanced Energy Materials 12 (2022)
    doi: 10.1002/aenm.202201680
  • 2022 • 651 Hydrogen-based direct reduction of iron oxide at 700°C: Heterogeneity at pellet and microstructure scales
    Ma, Y. and Souza Filho, I.R. and Zhang, X. and Nandy, S. and Barriobero-Vila, P. and Requena, G. and Vogel, D. and Rohwerder, M. and Ponge, D. and Springer, H. and Raabe, D.
    International Journal of Minerals, Metallurgy and Materials 29 1901-1907 (2022)
    Steel production causes a third of all industrial CO2 emissions due to the use of carbon-based substances as reductants for iron ores, making it a key driver of global warming. Therefore, research efforts aim to replace these reductants with sustainably produced hydrogen. Hydrogen-based direct reduction (HyDR) is an attractive processing technology, given that direct reduction (DR) furnaces are routinely operated in the steel industry but with CH4 or CO as reductants. Hydrogen diffuses considerably faster through shaft-furnace pellet agglomerates than carbon-based reductants. However, the net reduction kinetics in HyDR remains extremely sluggish for high-quantity steel production, and the hydrogen consumption exceeds the stoichiometrically required amount substantially. Thus, the present study focused on the improved understanding of the influence of spatial gradients, morphology, and internal microstructures of ore pellets on reduction efficiency and metallization during HyDR. For this purpose, commercial DR pellets were investigated using synchrotron high-energy X-ray diffraction and electron microscopy in conjunction with electron backscatter diffraction and chemical probing. Revealing the interplay of different phases with internal interfaces, free surfaces, and associated nucleation and growth mechanisms provides a basis for developing tailored ore pellets that are highly suited for a fast and efficient HyDR. © 2022, The Author(s).
    view abstractdoi: 10.1007/s12613-022-2440-5
  • 2022 • 650 Surface modification of silicon by femtosecond laser ablation in liquid
    Maack, P. and Kanitz, A. and Hoppius, J. and Köhler, J. and Esen, C. and Ostendorf, A.
    Proceedings of SPIE - The International Society for Optical Engineering 11989 (2022)
    Pulsed laser ablation is steadily gaining popularity in micromachining to keep pace with the increasing demand for precision manufacturing and functional surfaces. However, efficient laser processing under atmospheric conditions primarily suffers from particle redeposition and therefore requires additional cleaning steps to obtain high surface quality. To reduce additional cleanings steps after manufacturing, laser ablation in liquid allows for a significant reduction in particle redeposition as particles rapidly cool down and penetrate into the liquid without stitching to the surface. However, laser ablation in liquid is accompanied by the complex interaction between the hot molten material, the generated plasma and the over-critical liquid in the ablation zone. During this interaction, chemical reactions at the surface can take place and cause a persistent change of surface chemistry. Since the surface chemistry is a key aspect for micromachining, the interaction has to be studied to determine whether laser processing in liquids can be a feasible alternative to laser processing under ambient atmospheric conditions while reducing the problem of redeposition. Here, we present the results on the change of surface chemistry by laser ablation in liquid of a pristine silicon substrate. The micromachining process is either performed in an aqueous or gaseous environment and studied in dependence of laser intensity. The changes in surface chemistry are evaluated by micro-Raman spectroscopy and EDX. Copyright © 2022 SPIE.
    view abstractdoi: 10.1117/12.2608708
  • 2022 • 649 Setting Residual Stresses in Tensile Stress-Superposed Incremental Sheet Forming
    Maaß, F. and Hahn, M. and Tekkaya, A.E.
    Key Engineering Materials 926 KEM 655-662 (2022)
    doi: 10.4028/p-232uip
  • 2022 • 648 Modeling of the Split-Hopkinson-Pressure-Bar experiment with the explicit material point method
    Maassen, S.F. and Niekamp, R. and Bergmann, J.A. and Pöhl, F. and Schröder, J. and Wiederkehr, P.
    Computational Particle Mechanics 9 153-166 (2022)
    The material point method (MPM) represents an alternative discretization method for numerical simulations. It aims to combine the benefits of a Lagrangian representation of bodies and an Eulerian numerical solution approach. Therefore, especially at high material deformations the method is not prone to mesh distortions such as the finite element method (FEM). For this reason, the MPM is used to a great extent for modeling granular materials as in geo-mechanics. However, high deformations occur in many industrial processes on metallic materials. The Split-Hopkinson-Pressure-Bar (SHPB) experiment is used to characterize material properties at high deformation rates. Although widely used, this experiment is not yet standardized and shows a variety of sensitivities, e.g. to friction. Inter alia for this reason, simulations are conducted with the experiment to allow for a better evaluation of the measured data. The purpose of this work from an engineering point of view is to analyze the performance of the MPM on an SHPB experiment. In order to validate the experimental results for the material characterization under dynamic loading conditions we introduce frictional contact. We use arbitrary tri-linear brick domains in a 3D CPDI1 scheme, instead of originally used parallelepipeds. This allows for a more flexible geometry approximation using standard meshes. The results of the method are analyzed with respect to discretization sensitivity and discussed in the context of the experimental results for a 42CrMo4 steel. We were able to show that the method is capable to reproduce the SHPB experiment. Additionally the method shows convergency in the results with finer discretizations. Thus, the MPM has underlined its importance as an alternative simulation technique for problems with high deformation. © 2021, The Author(s).
    view abstractdoi: 10.1007/s40571-021-00399-w
  • 2022 • 647 Biomolecule‐Mediated Therapeutics of the Dentin–Pulp Complex: A Systematic Review
    Machla, F. and Angelopoulos, I. and Epple, M. and Chatzinikolaidou, M. and Bakopoulou, A.
    Biomolecules 12 (2022)
    The aim of this systematic review was to evaluate the application of potential therapeutic signaling molecules on complete dentin‐pulp complex and pulp tissue regeneration in orthotopic and ectopic animal studies. A search strategy was performed according to the Preferred Reporting Items for Systematic Reviews and Meta‐Analyses (PRISMA) statement in the MEDLINE/PubMed database. Animal studies evaluating the application of signaling molecules to pulpectomized teeth for pulp tissue or dentin‐pulp complex regeneration were included. From 2530 identified records, 18 fulfilled the eligibility criteria and were subjected to detailed qualitative analysis. Among the applied molecules, basic fibroblast growth factor, vascular endothelial growth factor, bone morpho-genetic factor‐7, nerve growth factor, and platelet‐derived growth factor were the most frequently studied. The clinical, radiographical and histological outcome measures included healing of peri-apical lesions, root development, and apical closure, cellular recolonization of the pulp space, in-growth of pulp‐like connective tissue (vascularization and innervation), mineralized dentin‐like tissue formation along the internal dentin walls, and odontoblast‐like cells in contact with the internal dentin walls. The results indicate that signaling molecules play an important role in dentin/pulp regeneration. However, further studies are needed to determine a more specific subset combination of molecules to achieve greater efficiency towards the desired tissue engineering applications. © 2022 by the authors. Licensee MDPI, Basel, Switzerland.
    view abstractdoi: 10.3390/biom12020285
  • 2022 • 646 Influence of different ester side groups in polymers on the vapor phase infiltration with trimethyl aluminum
    Mai, L. and Maniar, D. and Zysk, F. and Schöbel, J. and Kühne, T.D. and Loos, K. and Devi, A.
    Dalton Transactions 51 1384-1394 (2022)
    doi: 10.1039/d1dt03753f
  • 2022 • 645 High-power UTC-photodiodes for an optically pumped subharmonic terahertz receiver
    Makhlouf, S. and Martinez-Gil, J. and Grzeslo, M. and Moro-Melgar, D. and Cojocari, O. and Stöhr, A.
    Optics Express 30 43798-43814 (2022)
    doi: 10.1364/OE.470375
  • 2022 • 644 Digestion processes and elemental analysis of oxide and sulfide solid electrolytes
    Malkowski, T.F. and Boeding, E.D. and Fattakhova-Rohlfing, D. and Wettengl, N. and Finsterbusch, M. and Veith, G.M.
    Ionics 28 3223-3231 (2022)
    doi: 10.1007/s11581-022-04536-0
  • 2022 • 643 Thermoregeneration of Fouling-Inhibiting Plastrons on Conductive Laser-Induced Graphene Coatings by Joule Heating
    Manderfeld, E. and Nunes Kleinberg, M. and Thamaraiselvan, C. and Arnusch, C.J. and Rosenhahn, A.
    Advanced Materials Interfaces (2022)
    Superhydrophobic surfaces are capable to resist the adhesion of organisms through a surface bound air layer, known as a plastron. However, the lifetime of such plastrons is limited and their decay results in the loss of the protective barrier against organism attachment. Here a method is established to replenish the plastron by Joule heating of electrically conductive, superhydrophobic laser-induced graphene (SLIG) coatings. Local heating with a DC current reduces the water solubility of gases and the growth of an initial microplastron into a macroplastron through gas nucleation at the liquid–air interface is observed. Small temperature differences between the surface and the surrounding water could induce this effect. Different SLIG surfaces are challenged against biofouling by the diatom Navicula perminuta under dynamic conditions and it is shown that surfaces with intact plastron resist diatom accumulation. Surfaces without the protective air layer are found to accumulate high amounts of diatoms. The results underline the promising potential of plastron-based antifouling approaches because plastrons can be stabilized for extended times. This strategy could be applied to many other materials for an effective protection against fouling organism. © 2022 The Authors. Advanced Materials Interfaces published by Wiley-VCH GmbH.
    view abstractdoi: 10.1002/admi.202201336
  • 2022 • 642 Bacterial surface attachment and fouling assay on polymer and carbon surfaces using Rheinheimera sp. identified using bacteria community analysis of brackish water
    Manderfeld, E. and Thamaraiselvan, C. and Nunes Kleinberg, M. and Jusufagic, L. and Arnusch, C.J. and Rosenhahn, A.
    Biofouling 38 940-951 (2022)
    doi: 10.1080/08927014.2022.2153333
  • 2022 • 641 Exploring stability of a nanoscale complex solid solution thin film by in situ heating transmission electron microscopy
    Manjón, A.G. and Zhang, S. and Völker, B. and Meischein, M. and Ludwig, Al. and Scheu, C.
    MRS Bulletin (2022)
    Abstract: Combining thin film deposition with in situ heating electron microscopy allows to understand the thermal stability of complex solid solution nanomaterials. From a CrMnFeCoNi alloy target a thin film with an average thickness of ~10 nm was directly sputtered onto a heating chip for in situ transmission electron microscopy. We investigate the growth process and the thermal stability of the alloy and compare our results with other investigations on bulk alloys or bulk-like films thicker than 100 nm. For the chosen sputtering condition and SiNx substrate, the sputter process leads to the Stranski–Krastanov growth type (i.e., islands forming on the top of a continuous layer). Directly after sputtering, we detect two different phases, namely CoNi-rich nanoscale islands and a continuous CrMnFe-rich layer. In situ annealing of the thin film up to 700°C leads to Ostwald ripening of the islands, which is enhanced in the areas irradiated by the electron beam during heating. Besides Ostwald ripening, the chemical composition of the continuous layer and the islands changed during the heating process. After annealing, the islands are still CoNi-rich, but lower amounts of Fe and Cr are observed and Mn was completely absent. The continuous layer also changed its composition. Co and Ni were removed, and the amount of Cr lowered. These results confirm that the synthesis of a CrMnFeCoNi thin film with an average thickness of ~10 nm can lead to a different morphology, chemical composition, and stability compared to thicker films (>100 nm). Impact statement: Exploring stability of a complex solid solution thin film by in situ heating transmission electron microscopy is a study of the thermal stability of sputtered complex solid solution thin films with thicknesses of ~10 nm. Complex solid solution materials have a promising electrocatalytic behavior due to the interplay of multi-element active sites. In order to understand their catalytic properties, it is important to identify the different structure-composition-activity correlations. Thus, our investigation helps to clarify and to understand the stability of nanoscale complex solid solution with an average film thickness of ~10 nm. Graphic abstract: Combining sputter deposition with in situ heating transmission electron microscopy allows to understand the thermal stability of nanoscale complex solid solution thin films. [Figure not available: see fulltext.] © 2022, The Author(s).
    view abstractdoi: 10.1557/s43577-021-00217-x
  • 2022 • 640 Anhydrous LiNbO3 Synthesis and Its Application for Surface Modification of Garnet Type Li-Ion Conductors
    Mann, M. and Schwab, C. and Ihrig, M. and Finsterbusch, M. and Martin, M. and Guillon, O. and Fattakhova-Rohlfing, D.
    Journal of the Electrochemical Society 169 (2022)
    doi: 10.1149/1945-7111/ac6836
  • 2022 • 639 5.6 mW average power THz source with 8 THz bandwidth at 540 kHz repetition rate based on organic crystal BNA
    Mansourzadeh, S. and Vogel, T. and Omar, A. and Shalaby, M. and Cinchetti, M. and Saraceno, C.J.
    2022 Conference on Lasers and Electro-Optics, CLEO 2022 - Proceedings (2022)
  • 2022 • 638 Broadband THz-TDS with 5.6 mW average power at 540 kHz with organic crystal BNA
    Mansourzadeh, S. and Vogel, T. and Omar, A. and Shalaby, M. and Cinchetti, M. and Saraceno, C.J.
    International Conference on Infrared, Millimeter, and Terahertz Waves, IRMMW-THz 2022-August (2022)
    doi: 10.1109/IRMMW-THz50927.2022.9895680
  • 2022 • 637 Micro- and nano-devices for electrochemical sensing
    Mariani, F. and Gualandi, I. and Schuhmann, W. and Scavetta, E.
    Microchimica Acta 189 (2022)
    doi: 10.1007/s00604-022-05548-3
  • 2022 • 636 Digital, Online, Take-Home - University Students' Attitude towards Different Examination Formats
    Martin, R.J. and Liebherr, M. and Boumann, R. and Schweig, S. and Kracht, F.E. and Schramm, D.
    2022 IEEE German Education Conference, GeCon 2022 (2022)
    doi: 10.1109/GeCon55699.2022.9942732
  • 2022 • 635 Fabrication of Rectangular Micro-Channels by Ultrashort Pulse Ablation Using a Bessel Beam
    Marx, J. and Tenkamp, J. and Walther, F. and Esen, C.
    Journal of Laser Micro Nanoengineering 17 150-155 (2022)
    doi: 10.2961/jlmn.2022.03.2003
  • 2022 • 634 Multiscale characterization of damage tolerance in barium titanate thin films
    Mathews, N.G. and Saxena, A.K. and Venkataramani, N. and Dehm, G. and Jaya, B.N.
    Journal of Applied Physics 132 (2022)
    doi: 10.1063/5.0095139
  • 2022 • 633 Investigation and Visualization of Flow Fields in Stirred Tank Reactors Using a Fluorescence Tracer Method
    Matzke, M. and Behrens, C. and Jongebloed, N. and Steins, D. and Ulbricht, M. and Schultz, H.J.
    Chemie-Ingenieur-Technik 94 1131-1140 (2022)
    In this study, flow fields in stirred tank reactors are investigated by a fluorescence tracer method. For these measurements, a fluorescent dye is inserted into a stirred tank reactor and distributed by the impeller flow, following the characteristic main circulation pathways. By this means, the main flow fields can be detected and visualized. Originally developed and used for the investigation of viscoelastic fluids, the method was adapted for Newtonian fluids with low viscosity in this study, with impeller installation height and impeller Reynolds numbers selected as influencing parameters. The resulting flow fields in both single- and double-impeller setups match the known structures from literature excellently. Therefore, the developed fluorescence tracer method has proven to be a promising supplement to the established repertoire of fluid investigation methods, with little effort in both experiment itself as well as the following data analysis steps. © 2022 The Authors. Chemie Ingenieur Technik published by Wiley-VCH GmbH.
    view abstractdoi: 10.1002/cite.202200006
  • 2022 • 632 Process Diagnostics and Control in Thermal Spray
    Mauer, G. and Moreau, C.
    Journal of Thermal Spray Technology (2022)
    This perspective paper summarizes the authors’ view on how process diagnostics and control can help to gain a deeper insight into thermal spray processes and to better understand the underlying mechanisms. The current situation in terms of available process control strategies and suitable sensors is described. In perspective, it is assumed that with suitable models, sensors and machine learning tools, it will be possible to perform a smaller number of experiments to develop coatings with specific target characteristics. In addition, trained machine learning tools can be used to implement an efficient control strategy to produce coatings with high reproducibility and reliability. The corresponding existing knowledge gaps are analyzed to identify needs for future research. © 2022, The Author(s).
    view abstractdoi: 10.1007/s11666-022-01341-z
  • 2022 • 631 Influence of reactivation conditions on the physio-chemical properties of activated carbon
    Mauer, V. and Rathinam, K. and Bläker, C. and Pasel, C. and Panglisch, S. and Bathen, D.
    Journal of Water Process Engineering 48 (2022)
    doi: 10.1016/j.jwpe.2022.102784
  • 2022 • 630 Combination of X-ray powder diffraction and adsorption calorimetry for the characterization of calcium exchanged LTA zeolites
    Mauer, V. and Petersen, H. and Bläker, C. and Pasel, C. and Weidenthaler, C. and Bathen, D.
    Microporous and Mesoporous Materials 337 (2022)
    doi: 10.1016/j.micromeso.2022.111940
  • 2022 • 629 Development of Plasma Parameters for the Manufacture of MCrAlY Bond Coats by Low-Pressure Plasma Spraying Using a Cascaded Torch
    Mauer, G.
    Advanced Engineering Materials 24 (2022)
    MCrAlY bond coats (M-Ni, Co) for thermal barrier coating systems are often manufactured by low-pressure plasma spraying (LPPS) to achieve dense coatings with low oxygen uptake at high deposition efficiencies. Herein, the novel SinplexPro 03C plasma spray torch (Oerlikon Metco) is characterized regarding this application, and appropriate process parameters are developed. The mass-specific plasma enthalpy and the hydrogen–argon plasma gas ratio prove to be substantial factors. The best deposition efficiency and lowest porosity are achieved at a mass-specific plasma enthalpy between 17 and 19 MJ kg−1. The oxygen content increases degressively with the enthalpy. Already at small hydrogen fractions in the plasma gas, a fast route is established for the recombination of argon ions. Consequently, the thermal treatment of the feedstock is improved. Moreover, the porosity decreases at increasing hydrogen content of the plasma gas, as the gun is operated in constant current mode and thus the input power increases. However, the deposition efficiency decreases slightly. On the other hand, the oxygen content decreases due to the reducing effect of hydrogen. The deposition efficiency, porosity, and oxygen content are also reasonable if no hydrogen is admixed at all, as the fluctuations of the plasma are reduced. © 2022 The Authors. Advanced Engineering Materials published by Wiley-VCH GmbH.
    view abstractdoi: 10.1002/adem.202200856
  • 2022 • 628 Condition Monitoring of a Three-Cathode Cascaded Plasma Spray Torch Regarding Process Reliability
    Mauer, G. and Kurze, F. and Rauwald, K.-H. and Vaßen, R.
    Materials 15 (2022)
    The TriplexPro™-210 plasma spray torch (Oerlikon Metco) is a three-cathode plasma generator. It became a kind of workhorse for the wide range of tasks handled at the Jülich Thermal Spray Center (JTSC). Compared to conventional single-cathode torches, the cascaded design of the nozzle suggests low fluctuations of the arc and thus high stability. However, after a certain time, degradation sets in even with such a torch, impairing the reliability of the process. It is therefore important to detect indications of performance loss in time and not only during the inspection of the deposited layer. In this study, standard samples of YSZ thermal barrier coatings were sprayed regularly over a period of two years. Operational data and feedstock characteristics were collected and correlated with the area-specific mass deposition. It turned out that the measured substrate surface temperature showed a distinct correlation. Searching for the reasons for the temperature variations, several process parameters could be ruled out as they are monitored by calibrated sensors, controlled, and their time course is recorded by the control unit. Moreover, there are other parameters, which can have a considerable impact such as the robot alignment or the substrate cooling conditions. However, the purposeful experimental variation of such variables resulted in a variability of the mass deposition being considerably smaller than observed over the two years. Thus, it can be concluded that torch degradation had a pronounced effect, too. The substrate surface temperature can be used as indicator for the torch status and the reliability of the spray process. © 2022 by the authors.
    view abstractdoi: 10.3390/ma15186203
  • 2022 • 627 Plasma spraying porous thermal barrier coatings with high deposition efficiency: A solvable dilemma?
    Mauer, G. and Vaßen, R.
    Surface and Coatings Technology 451 (2022)
    doi: 10.1016/j.surfcoat.2022.129070
  • 2022 • 626 Spontaneous Formation of Functional Structures in Messy Environments
    Mayer, C.
    Life 12 (2022)
    Even though prebiotic chemistry initially deals with simple molecules, its composition rapidly gains complexity with oligomerization. Starting with, e.g., 20 monomers (such as the 20 proteinogenic amino acids), we expect 400 different dimers, 3,200,000 pentamers, or more than 1013 decamers. Hence, the starting conditions are very messy but also form a very powerful pool of potentially functional oligomers. A selecting structure (a “selector” such as membrane multilayers or vesicles) may pick and accumulate those molecules from the pool that fulfill a simple function (such as the suitability to integrate into a bilayer membrane). If this “selector” is, in turn, subject to a superimposed selection in a periodic process, the accumulated oligomers may be further trimmed to fulfill more complex functions, which improve the survival rate of the selectors. Successful oligomers will be passed from generation to generation and further improved in subsequent steps. After thousands of generations, the selector, together with its integrated oligomers, can form a functional unit of considerable order and complexity. The actual power of this process of random formation and selection has already been shown in laboratory experiments. In this concept paper, earlier results are summarized and brought into a new context. © 2022 by the author. Licensee MDPI, Basel, Switzerland.
    view abstractdoi: 10.3390/life12050720
  • 2022 • 625 Cerium oxide nanozymes as biocide-free antifouling finish for outdoor fabrics
    Mayer-Gall, T. and Engels, T. and Gutmann, J.S. and Pfitzner, F. and Pütz, E. and Tremel, W. and Gazanis, A. and Heermann, R. and Delaittre, G.
    Melliand International 28 121-123 (2022)
  • 2022 • 624 Structural defects in a Janus MoSSe monolayer: A density functional theory study
    Mehdipour, H. and Kratzer, P.
    Physical Review B 106 (2022)
    doi: 10.1103/PhysRevB.106.235414
  • 2022 • 623 Progress and Challenges of InGaN/GaN-Based Core–Shell Microrod LEDs
    Meier, J. and Bacher, G.
    Materials 15 (2022)
    LEDs based on planar InGaN/GaN heterostructures define an important standard for solid-state lighting. However, one drawback is the polarization field of the wurtzite heterostructure impacting both electron–hole overlap and emission energy. Three-dimensional core–shell microrods offer field-free sidewalls, thus improving radiative recombination rates while simultaneously increasing the light-emitting area per substrate size. Despite those promises, microrods have still not replaced planar devices. In this review, we discuss the progress in device processing and analysis of microrod LEDs and emphasize the perspectives related to the 3D device architecture from an applications point of view. © 2022 by the authors. Licensee MDPI, Basel, Switzerland.
    view abstractdoi: 10.3390/ma15051626
  • 2022 • 622 Erratum: Anisotropic thermodynamic and transport properties of single-crystalline CaKFe4 As4 (Physical Review B (2016) 94 (064501) DOI: 10.1103/PhysRevB.94.064501)
    Meier, W.R. and Kong, T. and Kaluarachchi, U.S. and Taufour, V. and Jo, N.H. and Drachuck, G. and Böhmer, A.E. and Saunders, S.M. and Sapkota, A. and Kreyssig, A. and Tanatar, M.A. and Prozorov, R. and Goldman, A.I. and Balakirev...
    Physical Review B 105 (2022)
    The inline equation for the Ginzburg number, Gi, in the right column of page 9 of the paper had a typo, displaying a wrong power of θ0. (Formula Presented). This typo did not affect the value of Gi for CaKFe 4 As 4 evaluated in the paper or any discussions and conclusions. © 2022 American Physical Society. All rights reserved.
    view abstractdoi: 10.1103/PhysRevB.105.179901
  • 2022 • 621 Modification of Surface and Sub-Surface Conditions of Cemented Carbide by Pressurized Air Wet Abrasive Jet Machining for PVD Coatings
    Meijer, A.L. and Ott, A. and Stangier, D. and Tillmann, W. and Biermann, D.
    Procedia CIRP 108 372-377 (2022)
    doi: 10.1016/j.procir.2022.04.073
  • 2022 • 620 Induction of residual compressive stresses in the sub-surface by the adjustment of the micromilling process and the tool´s cutting edge
    Meijer, A.L. and Stangier, D. and Tillmann, W. and Biermann, D., (1)
    CIRP Annals 71 97-100 (2022)
    doi: 10.1016/j.cirp.2022.04.065
  • 2022 • 619 Elemental (im-)miscibility determines phase formation of multinary nanoparticles co-sputtered in ionic liquids
    Meischein, M. and Garzón-Manjón, A. and Hammerschmidt, T. and Xiao, B. and Zhang, S. and Abdellaoui, L. and Scheu, C. and Ludwig, A.
    Nanoscale Advances 4 3855-3869 (2022)
    doi: 10.1039/d2na00363e
  • 2022 • 618 Nanoscale copper and silver thin film systems display differences in antiviral and antibacterial properties
    Meister, T.L. and Fortmann, J. and Breisch, M. and Sengstock, C. and Steinmann, E. and Köller, M. and Pfaender, S. and Ludwig, Al.
    Scientific Reports 12 (2022)
    The current Coronavirus Disease 19 (COVID-19) pandemic has exemplified the need for simple and efficient prevention strategies that can be rapidly implemented to mitigate infection risks. Various surfaces have a long history of antimicrobial properties and are well described for the prevention of bacterial infections. However, their effect on many viruses has not been studied in depth. In the context of COVID-19, several surfaces, including copper (Cu) and silver (Ag) coatings have been described as efficient antiviral measures that can easily be implemented to slow viral transmission. In this study, we detected antiviral properties against Severe Acute Respiratory Syndrome Coronavirus-2 (SARS-CoV-2) on surfaces, which were coated with Cu by magnetron sputtering as thin Cu films or as Cu/Ag ultrathin bimetallic nanopatches. However, no effect of Ag on viral titers was observed, in clear contrast to its well-known antibacterial properties. Further enhancement of Ag ion release kinetics based on an electrochemical sacrificial anode mechanism did not increase antiviral activity. These results clearly demonstrate that Cu and Ag thin film systems display significant differences in antiviral and antibacterial properties which need to be considered upon implementation. © 2022, The Author(s).
    view abstractdoi: 10.1038/s41598-022-11212-w
  • 2022 • 617 Evaluation of ammonia co-firing in the CRIEPI coal jet flame using a three mixture fraction FPV-LES
    Meller, D. and Engelmann, L. and Wollny, P. and Tainaka, K. and Watanabe, H. and Debiagi, P. and Stein, O.T. and Kempf, A.M.
    Proceedings of the Combustion Institute (2022)
    Highly resolved Large Eddy Simulations (LES) are performed to investigate co-firing of coal and ammonia in a burner experiment conducted by the Central Research Institute of Electric Power Industry (CRIEPI) in Japan. The coaxial burner with a hydrogen supported pulverized coal flame is modeled using the in-house code PsiPhi. A three mixture fraction flamelet/progress variable (FPV) approach is employed to simulate coal particle conversion due to devolatilization, hydrogen combustion, and ammonia combustion. Three cases are investigated and compared to each other: 1) a coal combustion case, injecting air and coal particles, 2) an ammonia combustion case, injecting a mixture of ammonia and air, and 3) a co-firing combustion case, injecting a mixture of coal, ammonia and air in the center tube. Two mechanisms are used to build the chemistry table and are compared against each other: a reduced CRECK mechanism with 120 reaction species and 1551 elementary reactions, originally reduced for coal combustion modeling, and a newly introduced reduced CRECK mechanism with 129 reaction species and 1644 elementary reactions, including the detailed NH3 reaction paths in addition to the coal chemistry. Species are compared for the coal case and temperature fields are compared for both the coal and co-firing case. Normalized LIF signals for OH and NH are presented for all three cases. The gas composition profiles are in good agreement with the experiment and the temperature fields are consistent with previous results for the pure coal flames. For pure ammonia and for ammonia co-firing, the new mechanism shows an improved prediction of the reaction zone. © 2022 Elsevier Inc. All rights reserved.
    view abstractdoi: 10.1016/j.proci.2022.07.182
  • 2022 • 616 Ab initio calculation of the magnetic Gibbs free energy of materials using magnetically constrained supercells
    Mendive-Tapia, E. and Neugebauer, J. and Hickel, T.
    Physical Review B 105 (2022)
    We present a first-principles approach for the computation of the magnetic Gibbs free energy of materials using magnetically constrained supercell calculations. Our approach is based on an adiabatic approximation of slowly varying local moment orientations, the so-called finite-temperature disordered local moment picture. It describes magnetic phase transitions and how electronic and/or magnetostructural mechanisms generate a discontinuous (first-order) character. We demonstrate that the statistical mechanics of the local moment orientations can be described by an affordable number of supercell calculations containing noncollinear magnetic configurations. The applicability of our approach is illustrated by firstly studying the ferromagnetic state in bcc Fe. We then investigate the temperature-dependent properties of a triangular antiferromagnetic state stabilizing in two antiperovskite systems Mn3AN (A=Ga, Ni). Our calculations provide the negative thermal expansion of these materials as well as the ab initio origin of the discontinuous character of the phase transitions, electronic and/or magnetostructural, in good agreement with experiment. © 2022 authors. Published by the American Physical Society. Published by the American Physical Society under the terms of the "https://creativecommons.org/licenses/by/4.0/"Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article's title, journal citation, and DOI. Open access publication funded by the Max Planck Society.
    view abstractdoi: 10.1103/PhysRevB.105.064425
  • 2022 • 615 Extremal states and coupling properties in electroelasticity
    Menzel, A. and Witt, C.
    Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences 380 (2022)
    Electroelastic materials possess properties most attractive for the design of smart devices and systems such as actuators and sensors. Typical polymers show changes in shape under the action of an electric field, and vice versa, together with fast actuation times, high strain levels and low elastic moduli. This paper deals with an Ogden model inspired framework for large deformation electroelasticity which, as a special case, can also be reduced to the modelling of transversely isotropic elasticity. Extremal (local) states are elaborated based on a coaxiality analysis, i.e. extremal states of energy are considered at fixed deformation and changing direction of electric field, respectively, fixed electric field and changing principal directions of deformation. This analysis results in extremal states when stresses and strain commutate, respectively, dielectric displacements and electric field are aligned. In order to further elaborate electromechanical coupling properties, the sensitivity of stresses with respect to electric field is analysed. This sensitivity is represented by a third-order tensor which, in general, depends on deformation and electric field. To illustrate this third-order tensor, a decomposition into deviators is adopted. Related norms of these deviators, together with the electromechanical coupling contribution to the augmented energy, are investigated for different states under homogeneous deformation and changing electric field direction. The analysis is considered to contribute to a better understanding of electromechanical coupling properties and extremal states in large deformation electroelasticity and by that, as a long-term goal, may contribute to the improved design of related smart devices and systems. This article is part of the theme issue 'The Ogden model of rubber mechanics: Fifty years of impact on nonlinear elasticity'. © 2022 The Author(s).
    view abstractdoi: 10.1098/rsta.2021.0330
  • 2022 • 614 Sodiation Of Hard Carbon: How Separating Enthalpy And Entropy Contributions Can Find Transitions Hidden In The Voltage Profile
    Mercer, M.P. and Affleck, S. and Gavilán-Arriazu, E.M. and Zülke, A.A. and Maughan, P.A. and Trivedi, S. and Fichtner, M. and Reddy Munnangi, A. and Leiva, E.P.M. and Hoster, H.E.
    ChemPhysChem 23 (2022)
    Sodium-ion batteries (NIBs) utilize cheaper materials than lithium-ion batteries (LIBs) and can thus be used in larger scale applications. The preferred anode material is hard carbon, because sodium cannot be inserted into graphite. We apply experimental entropy profiling (EP), where the cell temperature is changed under open circuit conditions. EP has been used to characterize LIBs; here, we demonstrate the first application of EP to any NIB material. The voltage versus sodiation fraction curves (voltage profiles) of hard carbon lack clear features, consisting only of a slope and a plateau, making it difficult to clarify the structural features of hard carbon that could optimize cell performance. We find additional features through EP that are masked in the voltage profiles. We fit lattice gas models of hard carbon sodiation to experimental EP and system enthalpy, obtaining: 1. a theoretical maximum capacity, 2. interlayer versus pore filled sodium with state of charge. © 2021 Wiley-VCH GmbH
    view abstractdoi: 10.1002/cphc.202100748
  • 2022 • 613 The potential of remdesivir to affect function, metabolism and proliferation of cardiac and kidney cells in vitro
    Merches, K. and Breunig, L. and Fender, J. and Brand, T. and Bätz, V. and Idel, S. and Kollipara, L. and Reinders, Y. and Sickmann, A. and Mally, A. and Lorenz, K.
    Archives of Toxicology 96 2341-2360 (2022)
    Remdesivir is a prodrug of a nucleoside analog and the first antiviral therapeutic approved for coronavirus disease. Recent cardiac safety concerns and reports on remdesivir-related acute kidney injury call for a better characterization of remdesivir toxicity and understanding of the underlying mechanisms. Here, we performed an in vitro toxicity assessment of remdesivir around clinically relevant concentrations (Cmax 9 µM) using H9c2 rat cardiomyoblasts, neonatal mouse cardiomyocytes (NMCM), rat NRK-52E and human RPTEC/TERT1 cells as cell models for the assessment of cardiotoxicity or nephrotoxicity, respectively. Due to the known potential of nucleoside analogs for the induction of mitochondrial toxicity, we assessed mitochondrial function in response to remdesivir treatment, early proteomic changes in NMCM and RPTEC/TERT1 cells and the contractile function of NMCM. Short-term treatments (24 h) of H9c2 and NRK-52E cells with remdesivir adversely affected cell viability by inhibition of proliferation as determined by significantly decreased 3H-thymidine uptake. Mitochondrial toxicity of remdesivir (1.6–3.1 µM) in cardiac cells was evident by a significant decrease in oxygen consumption, a collapse of mitochondrial membrane potential and an increase in lactate secretion after a 24–48-h treatment. This was supported by early proteomic changes of respiratory chain proteins and intermediate filaments that are typically involved in mitochondrial reorganization. Functionally, an impedance-based analysis showed that remdesivir (6.25 µM) affected the beat rate and contractility of NMCM. In conclusion, we identified adverse effects of remdesivir in cardiac and kidney cells at clinically relevant concentrations, suggesting a careful evaluation of therapeutic use in patients at risk for cardiovascular or kidney disease. © 2022, The Author(s).
    view abstractdoi: 10.1007/s00204-022-03306-1
  • 2022 • 612 Assessing the Lightweight Potential of Additively Manufactured Metals by Density-Specific Woehler and Shiozawa Diagrams
    Merghany, M. and Teschke, M. and Stern, F. and Tenkamp, J. and Walther, F.
    Frontiers in Mechanical Engineering 8 (2022)
    Additive manufacturing (AM) using the powder bed fusion (PBF) process is building up the components layer by layer, which enables the fabrication of complex 3D structures with unprecedented degrees of freedom. Due to the high cooling rates of the AM process, fine microstructures are generated. This leads to an improvement in quasistatic properties such as tensile strength, whereas the fatigue strength is comparable to that of conventionally manufactured metal or even reduced. This is due to the presence of process-induced defects formulated during the manufacturing process in combination with the increased notch stress sensitivity of high-strength metals. In this work, the fatigue damage assessment using different approaches like those of Murakami and Shiozawa for three AM alloys (AlSi10Mg, 316L, and TNM-B1) containing defects is studied for better understanding of capability and mechanisms. Moreover, the effect of the lightweight potential is investigated, and how the specific material density can be considered when the fatigue damage tolerance is characterized. Copyright © 2022 Merghany, Teschke, Stern, Tenkamp and Walther.
    view abstractdoi: 10.3389/fmech.2022.957859
  • 2022 • 611 Non-oxidative Dehydrogenation of Methanol to Formaldehyde over Bulk β-Ga2O3
    Merko, M. and Busser, G.W. and Muhler, M.
    ChemCatChem 14 (2022)
    The non-oxidative dehydrogenation of methanol to formaldehyde is considered a dream reaction compared with the classical oxidative route, because the valuable coupled product hydrogen is formed instead of water, and the produced anhydrous formaldehyde is highly suitable for the further synthesis of oxygenated synthetic fuels. This study reports on the high catalytic performance of pure β-Ga2O3 in this reaction at temperatures between 500 °C and 650 °C. At 550 °C and a GHSV of 45500 h−1, an initial selectivity to formaldehyde of 77 % was obtained at a methanol conversion of 72 %. Performing the reaction at temperatures beyond this range and lower GHSV resulted in a lower formaldehyde selectivity. The catalyst suffered from deactivation caused by formation of carbon deposits, but it was possible to regenerate its initial activity at 500 °C and 550 °C completely by an oxidative treatment. Irreversible deactivation occurred at 650 °C due to partial volatilization of Ga2O3. © 2022 The Authors. ChemCatChem published by Wiley-VCH GmbH.
    view abstractdoi: 10.1002/cctc.202200258
  • 2022 • 610 Analysing the entropy of lithium-ion cells to trace anodic half-cell ageing
    Mertin, G.K. and Wycisk, D. and Stadler, J. and von Kessel, O. and Richter, E. and Oldenburger, M. and Wieck, A.D. and Birke, K.P.
    Journal of Energy Storage 50 (2022)
    The full-cell entropy and its temperature dependency were measured for automotive lithium-ion cells with a graphite anode in dependence of the state of charge. Resulting entropy curves can be related to certain characteristic conditions of the graphite anode. Those characteristics are induced by a certain lithium-ion concentrations within the graphite. Comparing the entropy curves of fresh to aged cells shows a shift in the characteristics of these curves at a similar charge input. Those shifts were assigned to a change in the anodic net capacity, enabling an entropy based state of health estimation of the anode. The execution of the differential voltage analysis leads to similar results. © 2022 Elsevier Ltd
    view abstractdoi: 10.1016/j.est.2022.104109
  • 2022 • 609 Dynamic measurement of the entropy coefficient for battery cells
    Mertin, G.K. and Wycisk, D. and Oldenburger, M. and Stoye, G. and Fill, A. and Birke, K.P. and Wieck, A.D.
    Journal of Energy Storage 51 (2022)
    The entropy coefficient is an important quantity to describe thermodynamic processes of battery cells and to model the temperature dependency of the open-circuit voltage. Determining the entropy via potentiometric measurements is often time-consuming. Therefore, several methods were developed to quickly estimate the entropy coefficient. This paper presents a new method, which is relatively simple in its execution and evaluation. The method is based on relating a dynamic temperature change to the cell's voltage change at an induced exponential temperature progression. Due to the dynamic of this process, the measurement time will be reduced compared to the potentiometric method by factor 13 for the executed experiments under its stated conditions. © 2022 Elsevier Ltd
    view abstractdoi: 10.1016/j.est.2022.104361
  • 2022 • 608 OPTIMAL CONTROL OF PERFECT PLASTICITY PART I: STRESS TRACKING
    Meyer, C. and Walther, S.
    Mathematical Control and Related Fields 12 275-301 (2022)
    The paper is concerned with an optimal control problem governed by the rate-independent system of quasi-static perfect elasto-plasticity. The objective is to optimize the stress field by controlling the displacement at prescribed parts of the boundary. The control thus enters the system in the Dirichlet boundary conditions. Therefore, the safe load condition is automatically fulfilled so that the system admits a solution, whose stress field is unique. This gives rise to a well defined control-to-state operator, which is continuous but not Gâteaux differentiable. The control-to-state map is therefore regularized, first by means of the Yosida regularization resp. viscous approximation and then by a second smoothing in order to obtain a smooth problem. The approximation of global minimizers of the original non-smooth optimal control problem is shown and optimality conditions for the regularized problem are established. A numerical example illustrates the feasibility of the smoothing approach. © 2022, American Institute of Mathematical Sciences. All rights reserved.
    view abstractdoi: 10.3934/mcrf.2021022
  • 2022 • 607 Modeling and simulation of microstructure in metallic systems based on multi-physics approaches
    Mianroodi, J.R. and Shanthraj, P. and Liu, C. and Vakili, S. and Roongta, S. and Siboni, N.H. and Perchikov, N. and Bai, Y. and Svendsen, B. and Roters, F. and Raabe, D. and Diehl, M.
    npj Computational Materials 8 (2022)
    The complex interplay between chemistry, microstructure, and behavior of many engineering materials has been investigated predominantly by experimental methods. Parallel to the increase in computer power, advances in computational modeling methods have resulted in a level of sophistication which is comparable to that of experiments. At the continuum level, one class of such models is based on continuum thermodynamics, phase-field methods, and crystal plasticity, facilitating the account of multiple physical mechanisms (multi-physics) and their interaction during microstructure evolution. This paper reviews the status of simulation approaches and software packages in this field and gives an outlook towards promising research directions. © 2022, The Author(s).
    view abstractdoi: 10.1038/s41524-022-00764-0
  • 2022 • 606 Lossless multi-scale constitutive elastic relations with artificial intelligence
    Mianroodi, J.R. and Rezaei, S. and Siboni, N.H. and Xu, B.-X. and Raabe, D.
    npj Computational Materials 8 (2022)
    A seamless and lossless transition of the constitutive description of the elastic response of materials between atomic and continuum scales has been so far elusive. Here we show how this problem can be overcome by using artificial intelligence (AI). A convolutional neural network (CNN) model is trained, by taking the structure image of a nanoporous material as input and the corresponding elasticity tensor, calculated from molecular statics (MS), as output. Trained with the atomistic data, the CNN model captures the size- and pore-dependency of the material’s elastic properties which, on the physics side, derive from its intrinsic stiffness as well as from surface relaxation and non-local effects. To demonstrate the accuracy and the efficiency of the trained CNN model, a finite element method (FEM)-based result of an elastically deformed nanoporous beam equipped with the CNN as constitutive law is compared with that obtained by a full atomistic simulation. The trained CNN model predicts the elasticity tensor in the test dataset with a root-mean-square error of 2.4 GPa (3.0% of the bulk modulus) when compared to atomistic calculations. On the other hand, the CNN model is about 230 times faster than the MS calculation and does not require changing simulation methods between different scales. The efficiency of the CNN evaluation together with the preservation of important atomistic effects makes the trained model an effective atomistically informed constitutive model for macroscopic simulations of nanoporous materials, optimization of nanostructures, and the solution of inverse problems. © 2022, The Author(s).
    view abstractdoi: 10.1038/s41524-022-00753-3
  • 2022 • 605 Indentation behavior of creep-feed grinding induced gradient microstructures in single crystal nickel-based superalloy
    Miao, Q. and Ding, W. and Kuang, W. and Fu, Y. and Yin, Z. and Dai, C. and Cao, L. and Wang, H.
    Materials Letters 306 (2022)
    The gradient microstructures of surface layer in single crystal nickel-based superalloy were produced by creep-feed grinding. The mechanical properties (i.e., hardness, elastic modulus) and room-temperature (RT) creep behavior of such structures were evaluated using a nano-indentation technique. Results show that the gradient structures along depth from ground surface consisted of nanograins, submicron grains and lamellar-shape structures, and dislocation structures. Furthermore, it was found that the hardness and elastic modulus of gradient structures were higher by 8–10% than that of bulk material on average. However, the regions containing nanograins showed a remarkable increase in creep depth compared to bulk material, implying that the creep behavior of ground layer was changed unfavorably. The obtained stress exponents of gradient structures suggested that dislocation activities were the main mechanism for indentation creep deformation. © 2021 Elsevier B.V.
    view abstractdoi: 10.1016/j.matlet.2021.130956
  • 2022 • 604 Targeting early stages of cardiotoxicity from anti-PD1 immune checkpoint inhibitor therapy
    Michel, L. and Helfrich, I. and Hendgen-Cotta, U.B. and Mincu, R.-I. and Korste, S. and Mrotzek, S.M. and Spomer, A. and Odersky, A. and Rischpler, C. and Herrmann, K. and Umutlu, L. and Coman, C. and Ahrends, R. and Sickmann, A. ...
    European heart journal 43 316-329 (2022)
    AIMS: Cardiac immune-related adverse events (irAEs) from immune checkpoint inhibition (ICI) targeting programmed death 1 (PD1) are of growing concern. Once cardiac irAEs become clinically manifest, fatality rates are high. Cardio-oncology aims to prevent detrimental effects before manifestation of severe complications by targeting early pathological changes. We therefore aimed to investigate early consequences of PD1 inhibition for cardiac integrity to prevent the development of overt cardiac disease. METHODS AND RESULTS: We investigated cardiac-specific consequences from anti-PD1 therapy in a combined biochemical and in vivo phenotyping approach. Mouse hearts showed broad expression of the ligand PDL1 on cardiac endothelial cells as a main mediator of immune-crosstalk. Using a novel melanoma mouse model, we assessed that anti-PD1 therapy promoted myocardial infiltration with CD4+ and CD8+ T cells, the latter being markedly activated. Left ventricular (LV) function was impaired during pharmacological stress, as shown by pressure-volume catheterization. This was associated with a dysregulated myocardial metabolism, including the proteome and the lipidome. Analogous to the experimental approach, in patients with metastatic melanoma (n = 7) receiving anti-PD1 therapy, LV function in response to stress was impaired under therapy. Finally, we identified that blockade of tumour necrosis factor alpha (TNFα) preserved LV function without attenuating the anti-cancer efficacy of anti-PD1 therapy. CONCLUSIONS: Anti-PD1 therapy induces a disruption of cardiac immune homeostasis leading to early impairment of myocardial functional integrity, with potential prognostic effects on the growing number of treated patients. Blockade of TNFα may serve as an approach to prevent the manifestation of ICI-related cardiotoxicity. Published on behalf of the European Society of Cardiology. All rights reserved. © The Author(s) 2021. For permissions, please email: journals.permissions@oup.com.
    view abstractdoi: 10.1093/eurheartj/ehab430
  • 2022 • 603 Piezoelectric shear rheometry: Further developments in experimental implementation and data extraction
    Mikkelsen, M. and Eliasen, K.L. and Lindemann, N. and Moch, K. and Böhmer, R. and Karimi-Varzaneh, H.A. and Lacayo-Pineda, J. and Jakobsen, B. and Niss, K. and Christensen, T. and Hecksher, T.
    Journal of Rheology 66 983-1003 (2022)
    doi: 10.1122/8.0000379
  • 2022 • 602 Nano-LED driven phase change evolution of layered chalcogenides for Raman spectroscopy investigations
    Mikulics, M. and Adam, R. and Roman Sobolewski and Heidtfeld, S. and Cao, D. and Bürgler, D.E. and Schneider, C.M. and Mayer, J. and Hardtdegen, H.H.
    FlatChem 36 (2022)
    doi: 10.1016/j.flatc.2022.100447
  • 2022 • 601 Enzyme-Induced Ferrification of Hydrogels for Toughening of Functional Inorganic Compounds
    Milovanovic, M. and Rauner, N. and Civelek, E. and Holtermann, T. and Jid, O.E. and Meuris, M. and Brandt, V. and Tiller, J.C.
    Macromolecular Materials and Engineering 307 (2022)
    Enzyme-induced mineralization (EIM) has been shown to greatly enhance the mechanical properties of hydrogels by precipitation of calcium salts. Another feature of such hydrogels is their high toughness even when containing finely nanostructured mineral content of ≈75 wt%. This might be useful for bendable materials with high content of functional inorganic nanostructures. The present study demonstrates that EIM can form homogeneous nanostructures of water-insoluble iron salts within hydrogels. Crystalline iron(II) carbonate precipitates urease-induced within polyacrylate-based hydrogels and forms platelet structures that have the potential of forming self-organized nacre-like architectures. The platelet structure can be influenced by chemical composition of the hydrogel. Further, amorphous iron(II) phosphate precipitates within hydrogels with alkaline phosphatase, forming a nanostructured porous inorganic phase, homogeneously distributed within the double network hydrogel. The high amount of iron phosphate (more than 80 wt%) affords a stiffness of ≈100 MPa. The composite is still bendable with considerable toughness of 400 J m−2 and strength of 1 MPa. The high water content (&gt;50%) may allow fast diffusion processes within the material. This makes the iron phosphate-based composite an interesting candidate for flexible electrodes and demonstrates that EIM can be used to deliberately soften ceramic materials, rendering them bendable. © 2022 The Authors. Macromolecular Materials and Engineering published by Wiley-VCH GmbH.
    view abstractdoi: 10.1002/mame.202200051
  • 2022 • 600 Fatigue Assessment of Twin Wire Arc Sprayed and Machine Hammer-Peened ZnAl4 Coatings on S355 JRC+C Substrate
    Milz, M.P. and Wirtz, A. and Abdulgader, M. and Biermann, D. and Tillmann, W. and Walther, F.
    Materials 15 (2022)
    Structural elements for applications in maritime environments, especially offshore instal-lations, are subjected to various stresses, such as mechanical loads caused by wind or waves and corrosive attacks, e.g., by seawater, mist and weather. Thermally sprayed ZnAl coatings are often used for maritime applications, mainly due to good corrosion protection properties. Machine hammer peening (MHP) has the potential to increase fatigue and corrosion fatigue resistance of ZnAl coatings by adjusting various material properties such as hardness, porosity and roughness. This study investigates the fatigue behavior of twin wire arc sprayed and MHP post-treated ZnAl4 coat-ings. Unalloyed steel (S355 JRC+C) was selected as substrate material and tested as a reference. MHP achieved the desired improvements in material properties with increased hardness, decreased roughness and uniform coating thickness. Multiple and constant amplitude tests have been carried out to evaluate the fatigue capability of coating systems. In the high cycle fatigue regime, the addi-tional MHP post-treatment led to an improvement of the lifetime in comparison to pure sandblasted specimens. The surface was identified as a crack initiation point. ZnAl coating and MHP post-treat-ment are suitable to improve the fatigue behavior in the high cycle fatigue regime compared to uncoated specimens. © 2022 by the authors. Licensee MDPI, Basel, Switzerland.
    view abstractdoi: 10.3390/ma15031182
  • 2022 • 599 Electronic and Vibrational Properties of FeNiAl and CoNiAl Full Heusler Alloys: A First-Principles Comparison
    Miroshkina, O.N. and Sokolovskiy, V.V. and Buchelnikov, V.D. and Gruner, M.E.
    IEEE Transactions on Magnetics 58 (2022)
    doi: 10.1109/TMAG.2022.3142849
  • 2022 • 598 Impact of magnetic and antisite disorder on the vibrational densities of states in Ni2MnSn Heusler alloys
    Miroshkina, O.N. and Eggert, B. and Lill, J. and Beckmann, B. and Koch, D. and Hu, M.Y. and Lojewski, T. and Rauls, S. and Scheibel, F. and Taubel, A. and Šob, M. and Ollefs, K. and Gutfleisch, O. and Wende, H. and Gruner, M.E. a...
    Physical Review B 106 (2022)
    doi: 10.1103/PhysRevB.106.214302
  • 2022 • 597 Strategies for damage tolerance enhancement in metal/ceramic thin films: Lessons learned from Ti/TiN
    Mishra, A.K. and Gopalan, H. and Hans, M. and Kirchlechner, C. and Schneider, J.M. and Dehm, G. and Jaya, B.N.
    Acta Materialia 228 (2022)
    Most functional microelectronic devices as well as hard coatings use brittle ceramics like Titanium Nitride (TiN) in nanostructured, thin film form. Damage tolerance is critical to their deployment in service, and life extension. In this study, we explore multilayering to enhance the damage tolerance of such material systems. Ti/TiN is a model metal/ceramic system with a strong interface, where elastic-plastic mismatch could potentially be used to modify the crack driving force. We carry out systematic numerical simulations of crack driving force in Ti/TiN multilayers with changing layer spacing. Micro-cantilever experiments are then carried out on a selected set of multilayers to determine the fracture toughness as a function of the number of interfaces. The 50 layer multilayer exhibits a fracture toughness that is 82% higher than the single layer TiN while maintaining a comparable hardness to the latter. The weak intercolumnar boundaries of sputtered films are found to be a limitation in fully exploiting the advantage of the shielding effect due to alternating stiff and compliant layers. The results are discussed in the context of design parameters for multilayering in metal/ceramic thin film systems in general. © 2022 Acta Materialia Inc.
    view abstractdoi: 10.1016/j.actamat.2022.117777
  • 2022 • 596 METHOD FOR THE ANALYSIS OF EPISTEMIC AND ALEATORY UNCERTAINTIES FOR A RELIABLE EVALUATION OF FAILURE OF ENGINEERING STRUCTURES
    Miska, N. and Balzani, D.
    International Journal for Uncertainty Quantification 12 23-45 (2022)
    doi: 10.1615/Int.J.UncertaintyQuantification.2022042145
  • 2022 • 595 Fe(001) angle-resolved photoemission and intrinsic anomalous Hall conductivity in Fe seen by different ab initio approaches: LDA and GGA versus GW
    Młyńczak, E. and Aguilera, I. and Gospodarič, P. and Heider, T. and Jugovac, M. and Zamborlini, G. and Hanke, J.-P. and Friedrich, C. and Mokrousov, Y. and Tusche, C. and Suga, S. and Feyer, V. and Blügel, S. and Plucinski, L....
    Physical Review B 105 (2022)
    Many material properties such as the electronic transport characteristics depend on the details of the electronic band structure in the vicinity of the Fermi level. For an accurate ab initio description of the material properties, the electronic band structure must be known and theoretically reproduced with high fidelity. Here, we ask a question which of the ab initio methods compare the best to the experimental photoemission intensities from bcc Fe. We confront the photoemission data from Fe(001) thin film grown on Au(001) to the photoemission simulations based on different ab initio initial band structures: density functional theory (DFT) in the local density approximation (LDA) and the generalized gradient approximation (GGA) and GGA corrected with many-body perturbation theory in the GW approximation. We find the best comparison for the GW results. As a second step, we discuss how the calculated intrinsic anomalous Hall conductivity (AHC) in bcc Fe depends on the choice of the method that describes the electronic band structure and Fermi level position. We find very large differences in AHC between the three theoretical approaches and show that the AHC found for the experimental Fermi level location within the GW band structure is the closest to the literature results of transport experiments. This finding improves our understanding of not only the anomalous Hall effect itself, but also other related phenomena, such as the anomalous Nernst effect. © 2022 American Physical Society.
    view abstractdoi: 10.1103/PhysRevB.105.115135
  • 2022 • 594 Molecular Cross-correlations Govern Structural Rearrangements in a Nonassociating Polar Glass Former
    Moch, K. and Münzner, P. and Böhmer, R. and Gainaru, C.
    Physical Review Letters 128 (2022)
    doi: 10.1103/PhysRevLett.128.228001
  • 2022 • 593 Nongeneric structural-relaxation shape of supercooled liquids: Insights from linear and nonlinear experiments on propylene glycol
    Moch, K. and Münzner, P. and Gainaru, C. and Böhmer, R.
    Journal of Chemical Physics 157 (2022)
    doi: 10.1063/5.0131568
  • 2022 • 592 High-Pressure Pulsing of Ammonia Results in Carbamate as Strongly Inhibiting Adsorbate of Methanol Synthesis over Cu/ZnO/Al2O3
    Mockenhaupt, B. and Schwiderowski, P. and Jelic, J. and Studt, F. and Muhler, M. and Behrens, M.
    Journal of Physical Chemistry C (2022)
    doi: 10.1021/acs.jpcc.2c08823
  • 2022 • 591 An efficient and accurate approach for zero-frequency added mass for maneuvering simulations in deep and shallow water
    el Moctar, O. and Lantermann, U. and Chillcce, G.
    Applied Ocean Research 126 (2022)
    doi: 10.1016/j.apor.2022.103259
  • 2022 • 590 Forming Stress-Induced Initial Damage in Case Hardening Steel 16MnCrS5 Under Cyclic Axial Loading in LCF Regime
    Moehring, K. and Walther, F.
    Structural Integrity 24 267-273 (2022)
    Present materials used for industrial applications are significantly influenced by manufacturing technologies used during production of industrial goods and applied strains or stresses. For the latter are pre-deformations resulting, these induce changes in the material like hardening, residual stresses, changes in microstructure. In dependence on the level of pre-deformation initial damage is also induced in the microstructure. This study investigates the influence for the direction of pre-deformation on the fatigue performance in the load regime of low cycle fatigue (LCF). In order to quantify the influence of pre-deformation, destructive and non-destructive analyses by means of fatigue tests, hardness measurements, residual stress analyses, quantification of the pore partition and scanning electron analyses of the volume and the surface of the specimen were performed. The results obtained indicate a damage tolerance of the microstructure and the overcompensating effect of the orientation of manganese sulfides precepted. It is concluded that further investigations are necessary in order to quantify the influence of forming induced damage on the fatigue loading capability. © 2022, The Author(s), under exclusive license to Springer Nature Switzerland AG.
    view abstractdoi: 10.1007/978-3-030-97822-8_31
  • 2022 • 589 Efficient model-based bioequivalence testing
    Möllenhoff, K. and Loingeville, F. and Bertrand, J. and Nguyen, T.T. and Sharan, S. and Zhao, L. and Fang, L. and Sun, G. and Grosser, S. and Mentré, F. and Dette, H.
    Biostatistics (Oxford, England) 23 314-327 (2022)
    The classical approach to analyze pharmacokinetic (PK) data in bioequivalence studies aiming to compare two different formulations is to perform noncompartmental analysis (NCA) followed by two one-sided tests (TOST). In this regard, the PK parameters area under the curve (AUC) and $C_{\max}$ are obtained for both treatment groups and their geometric mean ratios are considered. According to current guidelines by the U.S. Food and Drug Administration and the European Medicines Agency, the formulations are declared to be sufficiently similar if the $90\%$ confidence interval for these ratios falls between $0.8$ and $1.25 $. As NCA is not a reliable approach in case of sparse designs, a model-based alternative has already been proposed for the estimation of $\rm AUC$ and $C_{\max}$ using nonlinear mixed effects models. Here we propose another, more powerful test than the TOST and demonstrate its superiority through a simulation study both for NCA and model-based approaches. For products with high variability on PK parameters, this method appears to have closer type I errors to the conventionally accepted significance level of $0.05$, suggesting its potential use in situations where conventional bioequivalence analysis is not applicable. © The Author 2020. Published by Oxford University Press. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.
    view abstractdoi: 10.1093/biostatistics/kxaa026
  • 2022 • 588 Testing for similarity of binary efficacy-toxicity responses
    Möllenhoff, K. and Dette, H. and Bretz, F.
    Biostatistics (Oxford, England) 23 949-966 (2022)
    doi: 10.1093/biostatistics/kxaa058
  • 2022 • 587 Tuning of optical coherence tomography texture features as a basis for tissue differentiation in glioblastoma samples
    Möller, J. and Popanda, E. and Tischoff, I. and Aydın, N.H. and Welp, H. and Brenner, C. and Gerhardt, N.C. and Schmieder, K. and Miller, D. and Hofmann, M.R.
    Progress in Biomedical Optics and Imaging - Proceedings of SPIE 11948 (2022)
    doi: 10.1117/12.2609402
  • 2022 • 586 Design Principles for Boundary Spanning in Transdisciplinary Design Science Research
    Möller, F. and Chandra Kruse, L. and Schoormann, T. and Otto, B.
    Lecture Notes in Computer Science (including subseries Lecture Notes in Artificial Intelligence and Lecture Notes in Bioinformatics) 13229 LNCS 42-54 (2022)
    Design principles capture prescriptive design knowledge to guide design science researchers and design professionals in their design works. In the context of a transdisciplinary team, design principles can also be a powerful vehicle to bridge knowledge barriers and facilitate collaboration among team members with different backgrounds and expertise. These heterogeneous actors use design principles as a boundary object which helps to mediate their diverse perspectives. The paper draws from boundary object theory to explore the goals and the mechanisms of boundary spanning through ‘design principles-in-use’ and ‘design principles-in-formulation’. We discuss the applicability of our findings using a case of formulation and application of design principles for data spaces in a transdisciplinary research consortium. Our results add the layers of transdisciplinary collaboration to the ongoing discourse on design principles and design knowledge accumulation and evolution. © 2022, Springer Nature Switzerland AG.
    view abstractdoi: 10.1007/978-3-031-06516-3_4
  • 2022 • 585 Spin-Polarized Photoemission from Chiral CuO Catalyst Thin Films
    Möllers, P.V. and Wei, J. and Salamon, S. and Bartsch, M. and Wende, H. and Waldeck, D.H. and Zacharias, H.
    ACS Nano 16 12145-12155 (2022)
    The chirality-induced spin selectivity (CISS) effect facilitates a paradigm shift for controlling the outcome and efficiency of spin-dependent chemical reactions, for example, photoinduced water splitting. While the phenomenon is established in organic chiral molecules, its emergence in chiral but inorganic, nonmolecular materials is not yet understood. Nevertheless, inorganic spin-filtering materials offer favorable characteristics, such as thermal and chemical stability, over organic, molecular spin filters. Chiral cupric oxide (CuO) thin films can spin polarize (photo)electron currents, and this capability is linked to the occurrence of the CISS effect. In the present work, chiral CuO films, electrochemically deposited on partially UV-transparent polycrystalline gold substrates, were subjected to deep-UV laser pulses, and the average spin polarization of photoelectrons was measured in a Mott scattering apparatus. By energy resolving the photoelectrons and changing the photoexcitation geometry, the energy distribution and spin polarization of the photoelectrons originating from the Au substrate could be distinguished from those arising from the CuO film. The findings reveal that the spin polarization is energy dependent and, furthermore, indicate that the measured polarization values can be rationalized as a sum of an intrinsic spin polarization in the chiral oxide layer and a contribution via CISS-related spin filtering of electrons from the Au substrate. The results support efforts toward a rational design of further spin-selective catalytic oxide materials. © 2022 The Authors. Published by American Chemical Society.
    view abstractdoi: 10.1021/acsnano.2c02709
  • 2022 • 584 Photonic Non-Invasive mmW and THz Imaging for Non-Melanoma Skin Cancer Detection
    Mohammad, I. and Rymanov, V. and Makhlouf, S. and Stoffels, I. and Klode, J. and Tang, X. and Ali, M. and Stohr, A.
    2022 5th International Workshop on Mobile Terahertz Systems, IWMTS 2022 (2022)
    This paper proposes a contact-less non-invasive diagnostic technique for skin cancer detection and screening based on millimeter-wave (mmW) to terahertz (THz) photonic near-field imaging. Key photonic technologies required for developing multi-spectral sensors are fabricated and reported. This includes broadband photodiodes and wideband near-field antennas, both offering an operational frequency tuning range in excess of 0.2 THz and a maximum operational frequency beyond 0.3 THz. Furthermore, a compact photonic Ka-band mmW imaging sensor has been developed. The sensor head consists of a broadband photodiode for mmW signal generation and a Schottky barrier diode for incoherent power detection within the Ka-band. Calibration of the integrated sensor head is performed using a manufactured gelatin-based skin phantom. Calibration results reveal that the expected refractive index difference of 1 between healthy skin tissue and malignant squamous cell carcinoma (SCC) tumor in the mmW range can be easily detected. Finally, the principal function of the developed photonic imaging sensor is proven in the first in-vivo experiments using human skin tissue and skin tumor tissue (SCC). Experimental results indicate that the tumor can be clearly distinguished from healthy skin. © 2022 IEEE.
    view abstractdoi: 10.1109/IWMTS54901.2022.9832443
  • 2022 • 583 Acid sphingomyelinase deactivation post-ischemia promotes brain angiogenesis and remodeling by small extracellular vesicles
    Mohamud Yusuf, A. and Hagemann, N. and Zhang, X. and Zafar, M. and Hussner, T. and Bromkamp, C. and Martiny, C. and Tertel, T. and Börger, V. and Schumacher, F. and Solari, F.A. and Hasenberg, M. and Kleinschnitz, C. and Doeppner...
    Basic research in cardiology 117 43 (2022)
    Antidepressants have been reported to enhance stroke recovery independent of the presence of depressive symptoms. They have recently been proposed to exert their mood-stabilizing actions by inhibition of acid sphingomyelinase (ASM), which catalyzes the hydrolysis of sphingomyelin to ceramide. Their restorative action post-ischemia/reperfusion (I/R) still had to be defined. Mice subjected to middle cerebral artery occlusion or cerebral microvascular endothelial cells exposed to oxygen-glucose deprivation were treated with vehicle or with the chemically and pharmacologically distinct antidepressants amitriptyline, fluoxetine or desipramine. Brain ASM activity significantly increased post-I/R, in line with elevated ceramide levels in microvessels. ASM inhibition by amitriptyline reduced ceramide levels, and increased microvascular length and branching point density in wildtype, but not sphingomyelinase phosphodiesterase-1 ([Smpd1]-/-) (i.e., ASM-deficient) mice, as assessed by 3D light sheet microscopy. In cell culture, amitriptyline, fluoxetine, and desipramine increased endothelial tube formation, migration, VEGFR2 abundance and VEGF release. This effect was abolished by Smpd1 knockdown. Mechanistically, the promotion of angiogenesis by ASM inhibitors was mediated by small extracellular vesicles (sEVs) released from endothelial cells, which exhibited enhanced uptake in target cells. Proteomic analysis of sEVs revealed that ASM deactivation differentially regulated proteins implicated in protein export, focal adhesion, and extracellular matrix interaction. In vivo, the increased angiogenesis was accompanied by a profound brain remodeling response with increased blood-brain barrier integrity, reduced leukocyte infiltrates and increased neuronal survival. Antidepressive drugs potently boost angiogenesis in an ASM-dependent way. The release of sEVs by ASM inhibitors disclosed an elegant target, via which brain remodeling post-I/R can be amplified. © 2022. The Author(s).
    view abstractdoi: 10.1007/s00395-022-00950-7
  • 2022 • 582 Applications of shape memory alloys in structural engineering with a focus on concrete construction – A comprehensive review
    Molod, M.A. and Spyridis, P. and Barthold, F.-J.
    Construction and Building Materials 337 (2022)
    doi: 10.1016/j.conbuildmat.2022.127565
  • 2022 • 581 Self-referenced optical frequency comb based on low-noise Yb:CALGO femtosecond laser system
    Molteni, L.M. and Canella, F. and Pirzio, F. and Betz, M. and Vicentini, E. and Coluccelli, N. and Piccino, G. and Agnesi, A. and Laporta, P. and Galzerano, G.
    Nuovo Cimento della Societa Italiana di Fisica C 45 (2022)
    doi: 10.1393/ncc/i2022-22206-5
  • 2022 • 580 Compression and characterization of ultrashort pulses at 1.5 and 3 um wavelength
    Montoya, O.A.N. and Bridger, M. and Tarasevitch, A. and Bovensiepen, U.
    Optics InfoBase Conference Papers (2022)
  • 2022 • 579 Preparation of Practical High-Performance Electrodes for Acidic and Alkaline Media Water Electrolysis
    Moon, G.-H. and Wang, Y. and Kim, S. and Budiyanto, E. and Tüysüz, H.
    ChemSusChem 15 (2022)
    The synthesis of electrocatalyst and the electrode preparation were merged into a one-step process and proved to be a versatile method to synthesize metal oxide electrocatalysts on the conductive carbon paper (CP). Very simply, the metal precursor deposited on the CP was thermally treated by a torch-gun for just 6 s, resulting in the formation of RuO2, Co3O4, and mixed oxide nanoparticles. The material could be directly used as working electrode for oxygen evolution reaction (OER). Compared with commercial and other state-of-the-art electrocatalysts, the fabricated electrode showed a superior electrocatalytic activity for OER in 1 m HClO4 and 1 m KOH in terms of not only a low overpotential to reach 10 mA cm−2 but also a high current density at 1.6 VRHE with satisfying a long-term stability. The novel strategy without requiring time-consuming and uneconomical steps could be expanded to the preparation of various metal oxides on conductive substrates towards diverse electrocatalytic applications. © 2021 The Authors. ChemSusChem published by Wiley-VCH GmbH.
    view abstractdoi: 10.1002/cssc.202102114
  • 2022 • 578 Electrocatalytic Conversion of Glycerol to Oxalate on Ni Oxide Nanoparticles-Modified Oxidized Multiwalled Carbon Nanotubes
    Morales, D.M. and Jambrec, D. and Kazakova, M.A. and Braun, M. and Sikdar, N. and Koul, A. and Brix, A.C. and Seisel, S. and Andronescu, C. and Schuhmann, W.
    ACS Catalysis 12 982-992 (2022)
    Electrocatalytic oxidation of glycerol (GOR) as the anode reaction in water electrolysis facilitates the production of hydrogen at the cathode at a substantially lower cell voltage compared with the oxygen evolution reaction. It simultaneously provides the basis for the production of value-added compounds at the anode. We investigate earth-abundant transition-metal oxide nanoparticles (Fe, Ni, Mn, Co) embedded in multiwalled carbon nanotubes as GOR catalysts. Out of the four investigated composites, the Ni-based catalyst exhibits the highest catalytic activity toward the GOR according to rotating disk electrode voltammetry, reaching a current density of 10 mA cm–2 already at 1.31 V vs RHE, a potential below the formation of Ni3+. Chronoamperometry conducted in a flow-through cell followed by HPLC analysis is used to identify and quantify the GOR products over time, revealing that the applied potential, electrolyte concentration, and duration of the experiment impact strongly the composition of the products’ mixture. Upon optimization, the GOR is directed toward oxalate production. Moreover, oxalate is not further converted and hence accumulates as a major organic product under the chosen conditions in a concentration ratio of 60:1 with acetate as a minor product after 48 h electrolysis in 7 M KOH, which represents a promising route for the synthesis of this highly valued product. © 2022 American Chemical Society
    view abstractdoi: 10.1021/acscatal.1c04150
  • 2022 • 577 Impact of interstitial elements on the stacking fault energy of an equiatomic CoCrNi medium entropy alloy: theory and experiments
    Moravcik, I. and Zelený, M. and Dlouhy, A. and Hadraba, H. and Moravcikova-Gouvea, L. and Papež, P. and Fikar, O. and Dlouhy, I. and Raabe, D. and Li, Z.
    Science and Technology of Advanced Materials 23 376-392 (2022)
    We investigated the effects of interstitial N and C on the stacking fault energy (SFE) of an equiatomic CoCrNi medium entropy alloy. Results of computer modeling were compared to tensile deformation and electron microscopy data. Both N and C in solid solution increase the SFE of the face-centered cubic (FCC) alloy matrix at room temperature, with the former having a more significant effect by 240% for 0.5 at % N. Total energy calculations based on density functional theory (DFT) as well as thermodynamic modeling of the Gibbs free energy with the CALPHAD (CALculation of PHAse Diagrams) method reveal a stabilizing effect of N and C interstitials on the FCC lattice with respect to the hexagonal close-packed (HCP) CoCrNi-X (X: N, C) lattice. Scanning transmission electron microscopy (STEM) measurements of the width of dissociated ½&lt;110&gt; dislocations suggest that the SFE of CoCrNi increases from 22 to 42–44 mJ·m−2 after doping the alloy with 0.5 at. % interstitial N. The higher SFE reduces the nucleation rates of twins, leading to an increase in the critical stress required to trigger deformation twinning, an effect which can be used to design load-dependent strain hardening response. © 2022 The Author(s). Published by National Institute for Materials Science in partnership with Taylor & Francis Group.
    view abstractdoi: 10.1080/14686996.2022.2080512
  • 2022 • 576 Interplay of viscosity and surface tension for ripple formation by laser melting
    Morawetz, K. and Trinschek, S. and Gurevich, E.L.
    Physical Review B 105 (2022)
    A model for ripple formation on liquid surfaces exposed to an external laser or particle beam and a variable ground is developed. The external incident beam is hereby mechanically coupled to the liquid surface due to surface roughness. Starting from the Navier-Stokes equation, the coupled equations for the velocity potential and the surface height are derived in a shallow-water approximation with special attention to viscosity. The resulting equations obey conservation laws for volume and momentum where characteristic potentials for gravitation and surface tension are identified analogously to conservative forces. The approximate solutions are discussed in the context of ripple formation in laser-materials processing involving melting of a surface by a laser beam. Linear stability analysis provides the formation of a damped wave modified by an interplay between the external beam, the viscosity, and the surface tension. The limit of small viscosity leads to damped gravitational and the limit of high viscosity to capillary waves. The resulting wavelengths are in the order of the ripples occurring in laser welding experiments, hinting at the involvement of hydrodynamic processes in their origin. By discussing the response of the system to external periodic excitations with the help of Floquet multipliers, we show that the ripple formation could be triggered by a a periodically modulated external beam, e.g., appropriate repetition rates of an incident laser beam. The weak nonlinear stability analysis provides ranges where hexagonal or stripe structures can appear. The orientation of stripe structures and ripples are shown to be dependent on the incident angle of the laser or particle beam where a minimal angle is reported. Numerical simulations confirm the findings and allow us to describe the influence of variable grounds. © 2022 American Physical Society.
    view abstractdoi: 10.1103/PhysRevB.105.035415
  • 2022 • 575 Pushing the boundaries of lithium battery research with atomistic modelling on different scales
    Morgan, L.M. and Mercer, M.P. and Bhandari, A. and Peng, C. and Islam, M.M. and Yang, H. and Holland, J. and Coles, S.W. and Sharpe, R. and Walsh, A. and Morgan, B.J. and Kramer, D. and Saiful Islam, M. and Hoster, H.E. and Edge, ...
    Progress in Energy 4 (2022)
    doi: 10.1088/2516-1083/ac3894
  • 2022 • 574 Influence of Two-Step Heat Treatments on Microstructure and Mechanical Properties of a β-Solidifying Titanium Aluminide Alloy Fabricated via Electron Beam Powder Bed Fusion
    Moritz, J. and Teschke, M. and Marquardt, A. and Heinze, S. and Heckert, M. and Stepien, L. and López, E. and Brueckner, F. and Walther, F. and Leyens, C.
    Advanced Engineering Materials (2022)
    Additive manufacturing technologies, particularly electron beam powder bed fusion (PBF-EB/M), are becoming increasingly important for the processing of intermetallic titanium aluminides. This study presents the effects of hot isostatic pressing (HIP) and subsequent two-step heat treatments on the microstructure and mechanical properties of the TNM-B1 alloy (Ti–43.5Al–4Nb–1Mo–0.1B) fabricated via PBF-EB/M. Adequate solution heat treatment temperatures allow the adjustment of fully lamellar (FL) and nearly lamellar (NL-β) microstructures. The specimens are characterized by optical microscopy and scanning electron microscopy (SEM), X-ray computed tomography (CT), X-ray diffraction (XRD), and electron backscatter diffraction (EBSD). The mechanical properties at ambient temperatures are evaluated via tensile testing and subsequent fractography. While lack-of-fusion defects are the main causes of failure in the as-built condition, the mechanical properties in the heat-treated conditions are predominantly controlled by the microstructure. The highest ultimate tensile strength is achieved after HIP due to the elimination of lack-of-fusion defects. The results reveal challenges originating from the PBF-EB/M process, for example, local variations in chemical composition due to aluminum evaporation, which in turn affect the microstructures after heat treatment. For designing suitable heat treatment strategies, particular attention should therefore be paid to the microstructural characteristics associated with additive manufacturing. © 2022 The Authors. Advanced Engineering Materials published by Wiley-VCH GmbH.
    view abstractdoi: 10.1002/adem.202200931
  • 2022 • 573 Locally Adapted Microstructures in an Additively Manufactured Titanium Aluminide Alloy Through Process Parameter Variation and Heat Treatment
    Moritz, J. and Teschke, M. and Marquardt, A. and Stepien, L. and López, E. and Brueckner, F. and Walther, F. and Leyens, C.
    Advanced Engineering Materials (2022)
    Electron beam powder bed fusion (PBF-EB/M) has been attracting great research interest as a promising technology for additive manufacturing of titanium aluminide alloys. However, challenges often arise from the process-induced evaporation of aluminum, which is linked to the PBF-EB/M process parameters. This study applies different volumetric energy densities during PBF-EB/M processing to deliberately adjust the aluminum contents in additively manufactured Ti–43.5Al–4Nb–1Mo–0.1B (TNM-B1) samples. The specimens are subsequently subjected to hot isostatic pressing (HIP) and a two-step heat treatment. The influence of process parameter variation and heat treatments on microstructure and defect distribution are investigated using optical and scanning electron microscopy, as well as X-ray computed tomography (CT). Depending on the aluminum content, shifts in the phase transition temperatures can be identified via differential scanning calorimetry (DSC). It is confirmed that the microstructure after heat treatment is strongly linked to the PBF-EB/M parameters and the associated aluminum evaporation. The feasibility of producing locally adapted microstructures within one component through process parameter variation and subsequent heat treatment can be demonstrated. Thus, fully lamellar and nearly lamellar microstructures in two adjacent component areas can be adjusted, respectively. © 2022 The Authors. Advanced Engineering Materials published by Wiley-VCH GmbH.
    view abstractdoi: 10.1002/adem.202200917
  • 2022 • 572 Influence of preheating temperatures on material properties of PBF-LB manufactured hot-work tool steel X37CrMoV5-1
    Moritz, S. and Ziesing, U. and Boes, J. and Lentz, J. and Weber, S. and Reuber, M.
    Procedia CIRP 111 171-175 (2022)
    doi: 10.1016/j.procir.2022.08.143
  • 2022 • 571 Gelation Dynamics upon Pressure-Induced Liquid-Liquid Phase Separation in a Water-Lysozyme Solution
    Moron, M. and Al-Masoodi, A. and Lovato, C. and Reiser, M. and Randolph, L. and Surmeier, G. and Bolle, J. and Westermeier, F. and Sprung, M. and Winter, R. and Paulus, M. and Gutt, C.
    Journal of Physical Chemistry B 126 4160-4167 (2022)
    Employing X-ray photon correlation spectroscopy, we measure the kinetics and dynamics of a pressure-induced liquid-liquid phase separation (LLPS) in a water-lysozyme solution. Scattering invariants and kinetic information provide evidence that the system reaches the phase boundary upon pressure-induced LLPS with no sign of arrest. The coarsening slows down with increasing quench depths. The g2 functions display a two-step decay with a gradually increasing nonergodicity parameter typical for gelation. We observe fast superdiffusive (γ≥ 3/2) and slow subdiffusive (γ< 0.6) motion associated with fast viscoelastic fluctuations of the network and a slow viscous coarsening process, respectively. The dynamics age linearly with time τ ∝ tw, and we observe the onset of viscoelastic relaxation for deeper quenches. Our results suggest that the protein solution gels upon reaching the phase boundary. © 2022 American Chemical Society.
    view abstractdoi: 10.1021/acs.jpcb.2c01947
  • 2022 • 570 3D Visualization of the 2400-Year-Old Garments of Salt Man 4 from Chehrābād, Iran
    Moskvin, A. and Grömer, K. and Moskvina, M. and Kuzmichev, V. and Stöllner, T. and Aali, A.
    Interdisciplinary Contributions to Archaeology 319-338 (2022)
    This article presents a digital reconstruction of Salt man 4 (405–380 BCE), a salt miner’s mummy found in the Douzlākh salt mine (Chehrābād, northern Iran). The mummy and its costume are relatively well preserved because the salt mine offers good preservation conditions for organic finds. Salt man 4 is unique in that his garments are a complete set of worker’s gear. This offers an exceptional opportunity to study garments worn during heavy physical work in ancient times. An international research team has been conducting an in-depth study of the mummy since 2004. The results include measurements, photographs, MRI (magnetic resonance imaging) scans and descriptions, which taken together provide a good basis for a digital reconstruction. This article describes technical features of the reconstruction process and challenges that were solved to reproduce the garments. The reconstruction opens new ways of studying the costume in virtual reality using computer graphics and computer-aided design tools to obtain further insights into ancient mining clothes within the broader area of digital humanities. © 2022, The Author(s), under exclusive license to Springer Nature Switzerland AG.
    view abstractdoi: 10.1007/978-3-030-92170-5_18
  • 2022 • 569 The effects of aluminum concentration on the microstructural and electrochemical properties of lithium lanthanum zirconium oxide
    Moy, A.C. and Häuschen, G. and Fattakhova-Rohlfing, D. and Wolfenstine, J.B. and Finsterbusch, M. and Sakamoto, J.
    Journal of Materials Chemistry A (2022)
    doi: 10.1039/d2ta03676b
  • 2022 • 568 CHARACTERIZATION OF FATIGUE CRACK INITIATION AND PROPAGATION IN THERMOPLASTIC-BASED HYBRID LAMINATES
    Mrzljak, S. and Blickling, P. and Trautmann, M. and Wagner, G. and Walther, F.
    ECCM 2022 - Proceedings of the 20th European Conference on Composite Materials: Composites Meet Sustainability 3 869-876 (2022)
  • 2022 • 567 Assessment of laser cutting parameters and heat-affected zone on microstructure and fatigue behaviour of carbon fibre-reinforced epoxy
    Mrzljak, S. and Gerdes, L. and Keuntje, J. and Wippo, V. and Jaeschke, P. and Walther, F.
    Proceedings of the Institution of Mechanical Engineers, Part E: Journal of Process Mechanical Engineering (2022)
    doi: 10.1177/09544089221139656
  • 2022 • 566 Nanoparticles Carrying NF-κB p65-Specific siRNA Alleviate Colitis in Mice by Attenuating NF-κB-Related Protein Expression and Pro-Inflammatory Cellular Mediator Secretion
    Müller, E.K. and Białas, N. and Epple, M. and Hilger, I.
    Pharmaceutics 14 (2022)
    Ulcerative colitis is a disease that causes inflammation and ulcers in the colon and which is typically recurrent, and NF-κB proteins are important players during disease progression. Here, we assess the impact of silica-coated calcium phosphate nanoparticles carrying encapsulated siRNA against NF-κB p65 on a murine model of colitis. To this end, nanoparticles were injected intravenously (2.0 mg siRNA/kg body weight) into mice after colitis induction with dextran sulfate sodium or healthy ones. The disease activity index, the histopathological impact on the colon, the protein expression of several NF-κB-associated players, and the mediator secretion (colon tissue, blood) were analyzed. We found that the nanoparticles effectively alleviated the clinical and histopathological features of colitis. They further suppressed the expression of NF-κB proteins (e.g., p65, p50, p52, p100, etc.) in the colon. They finally attenuated the local (colon) or systemic (blood) pro-inflammatory mediator secretion (e.g., TNF-α, IFN-β, MCP-1, interleukins, etc.) as well as the leucocyte load of the spleen and mesenteric lymph nodes. The nanoparticle biodistribution in diseased animals was seen to pinpoint organs containing lymphoid entities (appendix, intestine, lung, etc.). Taken together, the nanoparticle-related silencing of p65 NF-κB protein expression could well be used for the treatment of ulcerative colitis in the future. © 2022 by the authors. Licensee MDPI, Basel, Switzerland.
    view abstractdoi: 10.3390/pharmaceutics14020419
  • 2022 • 565 Investigation of the effect of carbon post- vs pre-coated metallic bipolar plates for PEMFCs – start-up and shut-down
    Müller, M.-V. and Giorgio, M. and Hausmann, P. and Kinlechner, L. and Heinzel, A. and Schwämmlein, J.
    International Journal of Hydrogen Energy 47 8532-8548 (2022)
    In this work, the influence of increased potentials during the start-up/shut-down process on metallic bipolar plates (316L) with the coating system Cr/a-C based on graphite-like carbon is investigated. In comparison to commonly applied post-coated bipolar plates, a new low-cost manufacturing process based on pre-coated metal sheets for bipolar plates was evaluated. By developing a vehicle near start-up/shut-down cycle, a relative humidity of 140% and anode residence time of 0.94 s show the greatest damage potential of the cycle variations. After 2000 start-up/shut-down cycles, pre-coated metallic bipolar plates show no increased voltage loss compared to conventional coatings. Nevertheless, the resistances increase for Cr/a-C post- and pre-coating at the H2 outlet. This correlates with an increased surface roughness of the bipolar plate but otherwise only minor surface changes can be observed. The coating variation has no effect on the extent of catalyst coated membrane thinning or increased content of metal ions. © 2021 Hydrogen Energy Publications LLC
    view abstractdoi: 10.1016/j.ijhydene.2021.12.179
  • 2022 • 564 The Peptide/Antibody‐Based Surface Decoration of Calcium Phosphate Nanoparticles Carrying siRNA Influences the p65 NF‐κB Protein Expression in Inflamed Cells In Vitro
    Müller, E.K. and Białas, N. and Epple, M. and Hilger, I.
    Biomedicines 10 (2022)
    doi: 10.3390/biomedicines10071571
  • 2022 • 563 Guidelines to correctly measure the lithium ion conductivity of oxide ceramic electrolytes based on a harmonized testing procedure
    Müller, M. and Auer, H. and Bauer, A. and Uhlenbruck, S. and Finsterbusch, M. and Wätzig, K. and Nikolowski, K. and Dierickx, S. and Fattakhova-Rohlfing, D. and Guillon, O. and Weber, A.
    Journal of Power Sources 531 (2022)
    doi: 10.1016/j.jpowsour.2022.231323
  • 2022 • 562 TCAD Simulation of InP DHBTs with an In53.2Ga46.8As Base and InGaAsP Collector Grading
    Mueller, K. and Possberg, A. and Coers, M. and Zhang, H. and Weimann, N.
    2022 5th International Workshop on Mobile Terahertz Systems, IWMTS 2022 (2022)
    This work focuses on causes and improvements of non-linear behavior of InP DHBTs from a physical simulation point of view. The simulated devices are based on triple mesa structures with type-I band alignment employing a carbon doped In53.2Ga46.8As base, 0.5 μm emitter width and InGaAsP material in the collector region to improve the electron transport. Simulated OIP3 values differed by about 5 dB between two devices. RF performance, in terms of transit frequency and maximum frequency of oscillation, differed by about 75 GHz and 87 GHz for the same device designs. The improved design also showed better electron transport across the collector region, underlining the high sensitivity of device performance effected by the collector design. © 2022 IEEE.
    view abstractdoi: 10.1109/IWMTS54901.2022.9832460
  • 2022 • 561 Major surgical trauma impairs the function of natural killer cells but does not affect monocyte cytokine synthesis
    Müller-Heck, R.M. and Bösken, B. and Michiels, I. and Dudda, M. and Jäger, M. and Flohé, S.B.
    Life 12 (2022)
    Major traumatic and surgical injury increase the risk for infectious complications due to immune dysregulation. Upon stimulation with interleukin (IL) 12 by monocyte/macrophages, natural killer (NK) cells release interferon (IFN) γ that supports the elimination of the pathogen. In the present study, we investigated the impact of invasive spine surgery on the relationship between monocytes and NK cells upon exposure to Staphylococcus aureus. Mononuclear cells and serum were isolated from peripheral blood of patients before and up to 8 d after surgery and stimulated with inactivated S. aureus bacteria. NK cell and monocyte function were determined by flow cytometry. NK cells continuously lost their ability to produce IFN-γ during the first week after surgery independently from monocyte-derived IL-12 secretion. IFN-γ synthesis was minimal on day 8 and was associated with decreased expression of the IL-12 receptor and activation of transcription factors required for IFNG gene transcription. Addition of recombinant IL-12 could at least partially restore NK cell function. Pre-operative levels of growth/differentiation factor (GDF) 15 in the serum corre-lated with the extent of NK cell suppression and with hospitalization. Thus, NK cell suppression after major surgery might represent a therapeutic target to improve the immune defense against opportunistic infections. © 2021 by the authors. Li-censee MDPI, Basel, Switzerland.
    view abstractdoi: 10.3390/life12010013
  • 2022 • 560 Influence of non-convergent cation ordering on thermal expansion of rare-earth oxoborates RCa4O(BO3)3 (R = Er, Y, Dy, Gd, Sm, Nd, La)
    Münchhalfen, M. and Schreuer, J. and Reuther, C. and Stöcker, H.
    Materialia 26 (2022)
    The tensors of thermal expansion of monoclinic RCa4O(BO3)3 with R = Er, Y, Dy, Gd, Sm, Nd, La were studied in the temperature range from 100 K to 1373 K using high-resolution dilatometry. Reproducible anomalies, characterized by an excess strain at high temperatures, occur at different temperatures depending on the type of the R3+ cation. Additional single-crystal diffraction experiments on quenched samples and heat capacity measurements indicate that non-convergent cation ordering processes involving Ca2+ and R3+ play an essential role here. The cation distribution on the specific structural sites and the evolution of disorder with temperature are mainly influenced by the size of the trivalent cation, with the minimization of internal stresses being the driving force. The onset temperatures and the specific anisotropy of the anomalies in the thermal expansion are directly related to these processes. © 2022 The Authors
    view abstractdoi: 10.1016/j.mtla.2022.101561
  • 2022 • 559 How the cation size impacts on the relaxational and diffusional dynamics of supercooled butylammonium-based ionic liquids: DPEBA-TFSI versus BTMA-TFSI
    Münzner, P. and Gainaru, C. and Böhmer, R.
    Zeitschrift fur Physikalische Chemie 236 923-937 (2022)
    doi: 10.1515/zpch-2021-3138
  • 2022 • 558 Dislocation-mediated electronic conductivity in rutile
    Muhammad, Q.K. and Bishara, H. and Porz, L. and Dietz, C. and Ghidelli, M. and Dehm, G. and Frömling, T.
    Materials Today Nano 17 (2022)
    It has been recently shown that doping-like properties can be introduced into functional ceramics by inducing dislocations. Especially for TiO2, donor and acceptor-like behavior were observed depending on the type of introduced mesoscopic dislocation network. However, these early reports could not fully elucidate the mechanism behind it. In this work, we rationalize the electrical properties of dislocations by targeted microelectrode impedance measurements, local conductivity atomic force microscopy, and Kelvin probe force microscopy on deformed single crystals, comparing dislocation-rich and deficient regions. With the help of finite element method calculations, a semi-quantitative model for the effect of dislocations on the macroscopic electrical properties is developed. The model describes the dislocation bundles as highly conductive regions in which respective space charges overlap and induce temperature-independent, highly stable electronic conductivity. We illustrate the mechanism behind unique electrical properties tailored by introducing dislocations and believe that these results are the cornerstone in developing dislocation-tuned functionality in ceramics. © 2021 Elsevier Ltd
    view abstractdoi: 10.1016/j.mtnano.2021.100171
  • 2022 • 557 Catalytic Biosensors Operating under Quasi-Equilibrium Conditions for Mitigating the Changes in Substrate Diffusion
    Muhs, A. and Bobrowski, T. and Lielpētere, A. and Schuhmann, W.
    Angewandte Chemie - International Edition 61 (2022)
    doi: 10.1002/anie.202211559
  • 2022 • 556 Propagation dynamics and interaction of multiple streamers at and above adjacent dielectric pellets in a packed bed plasma reactor
    Mujahid, Z.-U.I. and Korolov, I. and Liu, Y. and Mussenbrock, T. and Schulze, J.
    Journal of Physics D: Applied Physics 55 (2022)
    The propagation and interaction between surface streamers propagating over dielectric pellets in a packed bed plasma reactor operated in Helium are studied using phase and space resolved optical emission spectroscopy and simulations. Such a discharge is known to generate cathode directed positive streamers in the gas phase at the positions of minimum electrode gap followed by surface streamers that propagate along the dielectric surface. By systematically varying the gap between neighboring dielectric pellets, we observe that a larger gap between adjacent dielectric pellets enhances plasma emission near the contact points of the dielectric structures. In agreement with the experiment, the simulation results reveal that the gap influences the attraction of streamers towards adjacent dielectric pellets via polarization of the surface material and the repulsion induced by nearby streamers. For a smaller gap, the streamer propagation changes from along the surface to propagation through the volume and back to surface propagation due to a combination of repulsion between adjacent streamers, polarization of adjacent dielectric surfaces, as well as acceleration of electrons from the volume towards the streamer head. For a wider gap, the streamer propagates along the surface, but repulsion by neighboring streamers increases the offset between the streamers. The streamer achieves a higher speed near the contact point earlier in the absence of an adjacent streamer, which indicates the role of mutual streamer interaction via repulsion. © 2022 The Author(s). Published by IOP Publishing Ltd.
    view abstractdoi: 10.1088/1361-6463/ac99ea
  • 2022 • 555 Inference of Intensity-Based Models for Load-Sharing Systems With Damage Accumulation
    Muller, C.H. and Meyer, R.
    IEEE Transactions on Reliability (2022)
    To model damage accumulation for load-sharing systems, two models given by intensity functions of self-exciting point processes are proposed: a model with additive damage accumulation and a model with multiplicative damage accumulation. Both models include the model without damage accumulation as a special case. For both models, the likelihood functions are derived and maximum likelihood estimators and likelihood ratio tests are given in a scale-invariant version and a scale-dependent version. Furthermore, a Bayesian approach using Markov chain Monte Carlo methods for posterior computation is provided. The frequentist and Bayesian methods are applied to a data set of failures of tension wires of concrete beams where a significant damage accumulation effect is confirmed by both additive and multiplicative damage accumulation models. This is all the more remarkable as a simulation study indicates that the tests for an existing damage accumulation effect are rather conservative. Moreover, prediction intervals for the failure times of the tension wires in a new experiment are given, which improve former prediction intervals derived without damage accumulation. The simulation study considers a scenario with a fixed time horizon and one with fixed numbers of failed components of the systems. IEEE
    view abstractdoi: 10.1109/TR.2022.3140483
  • 2022 • 554 Transfer-matrix summation of path integrals for transport through nanostructures
    Mundinar, S. and Hahn, A. and König, J. and Hucht, A.
    Physical Review B 106 (2022)
    On the basis of the method of iterative summation of path integrals (ISPI), we develop a numerically exact transfer-matrix method to describe the nonequilibrium properties of interacting quantum-dot systems. For this, we map the ISPI scheme to a transfer-matrix approach, which is more accessible to physical interpretation, allows for a more transparent formulation of the theory, and substantially improves the efficiency. In particular, the stationary limit is directly implemented, without the need of extrapolation. The resulting method, referred to as "transfer-matrix summation of path integrals"(TraSPI), is then applied to resonant electronic transport through a single-level quantum dot. © 2022 authors. Published by the American Physical Society. Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article's title, journal citation, and DOI.
    view abstractdoi: 10.1103/PhysRevB.106.165427
  • 2022 • 553 Lattice dynamics, elastic, magnetic, thermodynamic and thermoelectric properties of the two-dimensional semiconductors MPSe3 (M = Cd, Fe and NI): a first-principles study
    Musari, A.A. and Kratzer, P.
    Materials Research Express 9 (2022)
    Adopting Density Functional Theory (DFT) with Hubbard U correction implemented in Quantum Espresso, we have performed a comprehensive first-principles study of MPSe3 (M = Cd. Fe and Ni) monolayers. The computed electronic properties revealed the semi-conductive nature of the monolayers with small indirect bandgaps. A free-standing single layer of MPSe3 can be exfoliated from the parent compound by virtue of its structural stability and high in-plane stiffness. Hence, the elastic and dynamical properties were computed to establish the mechanical and dynamical stability. The results showed that CdPSe3 and NiPSe3 are stable in the trigonal structure while a single negative frequency observed in the phonon dispersion of FePSe3 indicates the possibility to relax to another, less symmetric structure. In addition, these 2D systems showed relatively good response when subjected to strain hence, they can be said to be mechanically stable. The thermodynamic properties, such as internal energies, vibrational free energies, entropies and constant-volume heat capacities have been computed within the harmonic approximations using the phonon density of states. The computed thermoelectric properties show that CdPSe3 and FePSe3 have the peak figure of merit at low temperature of 50 K. This work predicts a thermoelectric performance with an electronic figure of merit of 0.28 for p-doped CdPSe3. Moreover, the DFT+U method predicts an electronic figure of merit of 0.39 and 0.2 for p-doped FePSe3 and NiPSe3, respectively. © 2022 The Author(s). Published by IOP Publishing Ltd.
    view abstractdoi: 10.1088/2053-1591/ac96d3
  • 2022 • 552 Molecular Permeation in Freestanding Bilayer Silica
    Naberezhnyi, D. and Mai, L. and Doudin, N. and Ennen, I. and Hütten, A. and Altman, E.I. and Devi, A. and Dementyev, P.
    Nano Letters 22 1287-1293 (2022)
    Graphene and other single-layer structures are pursued as high-flux separation membranes, although imparting porosity endangers their crystalline integrity. In contrast, bilayer silica composed of corner-sharing (SiO4) units is foreseen to be permeable for small molecules due to its intrinsic lattice openings. This study sheds light on the mass transport properties of freestanding 2D SiO2 upon using atomic layer deposition (ALD) to grow large-area films on Au/mica substrates followed by transfer onto Si3N4 windows. Permeation experiments with gaseous and vaporous substances reveal the suspended material to be porous, but the membrane selectivity appears to diverge from the size exclusion principle. Whereas the passage of inert gas molecules is hindered with a permeance below 10-7 mol·s-1·m-2·Pa-1, condensable species like water are found to cross vitreous bilayer silica a thousand times faster in accordance with their superficial affinity. This work paves the way for bilayer oxides to be addressed as inherent 2D membranes. © 2022 American Chemical Society.
    view abstractdoi: 10.1021/acs.nanolett.1c04535
  • 2022 • 551 Non-Overlapped Subarrays Based Wideband Delay-Phase Hybrid Beamforming
    Najjar, A. and El-Absi, M. and Kaiser, T.
    2022 5th International Workshop on Mobile Terahertz Systems, IWMTS 2022 (2022)
    doi: 10.1109/IWMTS54901.2022.9832450
  • 2022 • 550 Electron g-factor determined for quantum dot circuit fabricated from (110)-oriented GaAs quantum well
    Nakagawa, T. and Lamoureux, S. and Fujita, T. and Ritzmann, J. and Ludwig, Ar. and Wieck, A.D. and Oiwa, A. and Korkusinski, M. and Sachrajda, A. and Austing, D.G. and Gaudreau, L.
    Journal of Applied Physics 131 (2022)
    The choice of substrate orientation for semiconductor quantum dot circuits offers opportunities for tailoring spintronic properties such as g-factors for specific functionality. Here, we demonstrate the operation of a few-electron double quantum dot circuit fabricated from a (110)-oriented GaAs quantum well. We estimate the in-plane electron g-factor from the profile of the enhanced inter-dot tunneling (leakage) current near-zero magnetic field. Spin blockade due to Pauli exclusion can block inter-dot tunneling. However, this blockade becomes inactive due to hyperfine interaction mediated spin flip-flop processes between electron spin states and the nuclear spin of the host material. The g-factor of absolute value ∼0.1 found for a magnetic field parallel to the direction [1 ¯ 10] is approximately a factor of four lower than that for comparable circuits fabricated from a material grown on widely employed standard (001) GaAs substrates and is in line with reported values determined by purely optical means for quantum well structures grown on (110) GaAs substrates. © 2022 Author(s).
    view abstractdoi: 10.1063/5.0086555
  • 2022 • 549 A control strategy for incremental profile forming
    Nakahata, R. and Seetharaman, S. and Srinivasan, K. and Tekkaya, A.E.
    Journal of Manufacturing Processes 79 142-153 (2022)
    Incremental profile forming (IPF) allows the flexible manufacture of metallic tubular structures with cross-sectional profiles that vary along their length, but its geometric accuracy is limited currently by exclusive reliance upon machine control of the process. Procedures for on-line sensing of process attributes and post-process sensing of part geometry, using laser triangulation sensors, are developed. Improved understanding of process characteristics for elementary IPF operations, obtained from FEM analysis and experiments, is described. Issues in developing a control-oriented process model are discussed along with prior related work. An overall control strategy for improving part geometry in IPF is formulated, indicating directions for needed research in process design, control-oriented modelling, sensing improvements, and control. © 2022
    view abstractdoi: 10.1016/j.jmapro.2022.04.034
  • 2022 • 548 Micromechanical Modeling of AlSi10Mg Processed by Laser-Based Additive Manufacturing: From as-Built to Heat-Treated Microstructures
    Nammalvar Raja Rajan, A. and Krochmal, M. and Wegener, T. and Biswas, A. and Hartmaier, A. and Niendorf, T. and Moeini, G.
    Materials 15 (2022)
    doi: 10.3390/ma15165562
  • 2022 • 547 Numerical simulation and parameterization of the heating and evaporation of a titanium (IV) isopropoxide/p-xylene precursor/solvent droplet in hot convective air
    Narasu, P. and Nanjaiah, M. and Wlokas, I. and Gutheil, E.
    International Journal of Multiphase Flow 150 (2022)
    Flame spray pyrolysis (FSP) is an excellent method to produce metal-oxide powders in the nano-size range. In this framework, the heating and evaporation of precursor solutions in hot oxidizing environments is investigated. A single spherically symmetric precursor/solvent droplets of titanium (IV) isopropoxide (TTIP) – Ti[OCH(CH3)2]4 in p-xylene – C6H4(CH3)2 at room temperature in convective hot air at atmospheric pressure is considered. Both variable liquid and gas thermophysical properties are incorporated and the non-random two-liquid (NRTL) model is used to describe the real behavior of the mixture. The bi-component droplet interior is not physically resolved and time-dependence is considered through the distillation-limit model for droplet heating and the rapid-mixing model accounts for droplet vaporization. A parameter study of the heating and evaporation characteristics of the single precursor/solvent droplet on the initial droplet size, the initial TTIP mass fraction in the droplet, the ambient air temperature, and the relative gas and droplet velocity is performed and discussed. The results are parameterized and tabulated in terms of polynomial fits of the individual mass evaporation rates of the components, the droplet surface temperature, and the normalized droplet surface area. A computer code in the programming language C is provided that can be incorporated into more complex simulations of FSP. © 2022 Elsevier Ltd
    view abstractdoi: 10.1016/j.ijmultiphaseflow.2022.104006
  • 2022 • 546 Adaptive modelling of dynamic brittle fracture - a combined phase field regularized cohesive zone model and scaled boundary finite element approach
    Natarajan, S. and Ooi, E.T. and Birk, C. and Song, C.
    International Journal of Fracture 236 87-108 (2022)
    doi: 10.1007/s10704-022-00634-2
  • 2022 • 545 Shock-tube study of the influence of oxygenated additives on benzene pyrolysis: Measurement of optical densities, soot inception times and comparison with simulations
    Nativel, D. and Herzler, J. and Krzywdziak, S. and Peukert, S. and Fikri, M. and Schulz, C.
    Combustion and Flame 243 (2022)
    The influence of the addition of oxygenated hydrocarbons (methanol, ethanol, and n-butanol) and ethers (diethyl ether, dimethoxymethane, furan, and tetrahydrofuran) on soot formation from benzene pyrolysis was studied. The pyrolysis process was investigated behind reflected shock waves at pressures around 1.4 bar and in the temperature range of 1670–2680 K. Extinction was measured at 633 nm to determine soot optical densities and soot-inception times. For extinction measurements, the studied gas mixtures contain 2.00 mol% C6H6 and 0.75 mol% additives diluted in argon. Since particle-inception times strongly depend on temperature and the reactive system cannot be considered isothermal because of the high reactant concentration in the shock tube, the temperature was measured as a function of time by two-color infrared absorption based on CO using two quantum-cascade lasers. For this purpose, 0.80 mol% CO and 5.00 mol% He were added to the studied gas mixtures as thermometry target species and enhancing species for vibrational relaxation, respectively. Both, temperature and measured optical densities were compared to simulations based on a detailed chemical kinetics mechanism from the CRECK Modeling Group. Additionally, simulations with a new mechanism composed of the CRECK mechanism (Pejpichestakul et al. 2009) and the recent PAH sub-mechanism of Sun et al. (2021) were performed. The agreement of experiments and simulations of the optical density were considerably improved using the aforementioned merged mechanism. © 2022 The Combustion Institute
    view abstractdoi: 10.1016/j.combustflame.2022.111985
  • 2022 • 544 Shock-tube study on the influence of oxygenated co-reactants on ethylene decomposition under pyrolytic conditions
    Nativel, D. and Peukert, S. and Herzler, J. and Drakon, A. and Korshunova, M. and Mikheyeva, E. and Eremin, A. and Fikri, M. and Schulz, C.
    Proceedings of the Combustion Institute (2022)
    The influence of various oxygenated co-reactants on soot formation was addressed by studying the pyrolysis of gas mixtures using ethylene as a base fuel in the absence of molecular oxygen. Alcohols (methanol, ethanol, and n-butanol) and ethers (diethyl ether, dimethoxymethane, furan, and tetrahydrofuran) were selected as oxygenated co-reactants. The pyrolysis process was studied behind reflected shock waves at around 3 bar. Laser extinction at 633 nm was used to determine soot-inception times and the related optical densities as a function of reaction time. The temporal variation in temperature was measured via time-resolved two-color CO absorption using two quantum-cascade lasers at 4.73 and 4.56 μm. Soot particle sizes were determined by time-resolved laser-induced incandescence using a Nd:YAG laser at a wavelength of 1064 nm. The major finding is that based on C2H4 as soot precursor, only CH3OH does not have a soot-promoting effect, whereas the addition of all other oxygenated hydrocarbons results in increased soot yields. The measured temperatures were compared with simulations based on a detailed chemical kinetics mechanism from the CRECK Modeling Group (Pejpichestakul et al. Proc. Combust. Inst. (2019)). In addition, kinetics modeling of hydrocarbon pyrolysis, PAH formation and soot growth was performed in OpenSMOKE++ software to give qualitative insight in the experimental results using the CRECK mechanism and an assembled mechanism composed of the CRECK and the recent PAH sub-mechanism (Sun et al. Proc. Combust. Inst. (2021)). The simulation reveals that the observed promotion of soot formation in presence of oxygenated co-reactants is associated with the release of CH3 and C3H3 during the thermal decomposition resulting in acceleration of C6H6 ring formation. © 2022 Elsevier Inc. All rights reserved.
    view abstractdoi: 10.1016/j.proci.2022.07.209
  • 2022 • 543 Study of thermal material properties for Ta- and Al-substituted Li7La3Zr2O12 (LLZO) solid-state electrolyte in dependency of temperature and grain size
    Neises, J. and Scheld, W.S. and Seok, A.-R. and Lobe, S. and Finsterbusch, M. and Uhlenbruck, S. and Schmechel, R. and Benson, N.
    Journal of Materials Chemistry A 10 12177-12186 (2022)
    doi: 10.1039/d2ta00323f
  • 2022 • 542 Unravelling the lamellar size-dependent fracture behavior of fully lamellar intermetallic γ-TiAl
    Neogi, A. and Janisch, R.
    Acta Materialia 227 (2022)
    Strengthening of metals by incorporating nano-scale coherent twin boundaries is one of the important breakthroughs of recent years in overcoming the strength-ductility trade-off. To this effect, also twin boundaries in nano-lamellar lightweight Ti-Al alloys promise a great potential, but their contribution to the deformation and fracture behavior needs to be better understood for designing optimal microstructures. To this end, we carry out linear elastic fracture mechanics informed large-scale atomistic simulations of fully lamellar microstructures consisting of the so-called ”true twin” boundaries in γ-TiAl. We find that nano-scale lamellae are not only effective in improving the fracture toughness and crack growth resistance, but also that the lamellar size controls the crack tip mechanisms. We identify a critical lamella thickness in the region between 1.64 and 3.04 nm, above which the crack tip events are primarily dislocation-based plasticity and the critical fracture initiation toughness exhibits an increasing trend with decreasing lamella size. Below the critical thickness, a decline in fracture toughness is observed and the crack tip propagation mechanisms are quasi-brittle in nature, i.e. the cleavage of atomic bonds at the crack tip is accompanied by plasticity events, such as twin-boundary migration and dislocation nucleation. A layer-wise analysis of the unstable stacking fault energy, the energy barrier for dislocation nucleation, that the critical thickness is of a similar value as the distance from the twin boundary at which bulk properties are restored. © 2022
    view abstractdoi: 10.1016/j.actamat.2022.117698
  • 2022 • 541 Compact Folded Leaky-Wave Antenna Radiating a Fixed Beam at Broadside for 5G mm-Wave Applications
    Neophytou, K. and Steeg, M. and Stöhr, A. and Antoniades, M.
    IEEE Antennas and Wireless Propagation Letters 21 292-296 (2022)
    A compact planar fixed-beam leaky-wave antenna that radiates its main beam at broadside is presented, that consists of two folded branches of periodically distributed series-fed microstrip patches. The antenna is fed from the center through a 50 Ω transmission line that subsequently feeds two constituent 100 Ω parallel branches, each consisting of eight series-fed microstrip patches. Fixed-beam operation is achieved by the combination of the two oppositely directed beams that are generated by the two branches. The proposed structure achieves a significant reduction of the longitudinal size by incorporating a 180° bend at the center of each branch, thus effectively folding the antenna in half. This results in a longitudinal size that is 1.8 times smaller than the analogous unfolded antenna. The antenna maintains a measured fixed beam at broadside over a wide zero beam-squinting bandwidth of 3 GHz in the 28 GHz band, with a radiation efficiency above 60% and a maximum measured gain of 14 dBi at 27.4 GHz, with an overall compact size of 5.8 × 1.1 cm. © 2002-2011 IEEE.
    view abstractdoi: 10.1109/LAWP.2021.3128563
  • 2022 • 540 Simultaneous User Localization and Identification Using Leaky-Wave Antennas and Backscattering Communications
    Neophytou, K. and Steeg, M. and Tebart, J. and Stohr, A. and Iezekiel, S. and Antoniades, M.A.
    IEEE Access 10 37097-37108 (2022)
    High-speed detection and identification of mobile terminals located in the vicinity of highly directive base stations is essential for future mm-wave communication systems. We propose a novel optoelectronic frequency modulated continuous wave (FMCW) radar system for detection, localization and identification of multiple mobile terminals. The simultaneous localization and identification of multiple mobile terminals is achieved by using frequency scanning mm-wave leaky-wave antennas (LWAs) and backscattering communications. LWAs provide RF-based beam steering for estimating the direction of arrival of the echoes using a FMCW radar signal. Additionally, the implementation of backscattering technology in the mobile terminals allows the identification of users. Hence, simultaneous user localization and identification without the use of any complicated radar signal post-processing algorithms is possible. Finally, the introduced modulated backscattering reflection shifts the signals of the targets at higher frequencies, which exhibit lower noise floor and thus have higher signal to noise ratio (SNR). © 2013 IEEE.
    view abstractdoi: 10.1109/ACCESS.2022.3161565
  • 2022 • 539 Numerical Multi-level Model for Fibre Reinforced Concrete: Validation and Comparison with Fib Model Code
    Neu, G.E. and Gudžulić, V. and Meschke, G.
    RILEM Bookseries 36 365-376 (2022)
    In this contribution, a Finite Element modelling scheme for steel-fibre reinforced concrete (SFRC) is proposed with which the post-cracking response of fibre reinforced structural members can be predicted. In contrast to the common guidelines, the post-cracking response of SFRC is derived from the actual fibre properties instead of indirectly from bending tests. The numerical model is designed to directly track the influence of design parameters such as fibre type, fibre orientation, fibre content and concrete strength on the structural response. For this purpose, sub models on the single fibre level are combined into a crack bridging model, considering the fibre orientation and the fibre content, and are integrated into a finite element model for the purpose of numerical structural analysis. The predictive capability of the proposed numerical multi-level model for SFRC is systematically validated by means of test series performed on the fibre, crack and the structural level. The experimental study comprises pull-out tests of Dramix 3D fibres, uniaxial tension tests involving different fibre contents and fibre types as well as three-point bending tests on notched beams with 23 and 57 kg/m3 Dramix 3D fibres. Furthermore, the results are compared to the modelling approach presented in the fib model code 2010 and an inverse analysis approach. © 2022, RILEM.
    view abstractdoi: 10.1007/978-3-030-83719-8_32
  • 2022 • 538 Reliability based optimization of steel-fibre segmental tunnel linings subjected to thrust jack loadings
    Neu, G.E. and Edler, P. and Freitag, S. and Gudžulić, V. and Meschke, G.
    Engineering Structures 254 (2022)
    The circular lining in mechanized tunnelling consists of concrete segments, which are exposed to different loading cases during tunnel construction. One of the most critical loading condition is the thrust jack force, which is induced to the lining segments by the Tunnel Boring Machine (TBM) during construction. Experimental campaigns showed that steel fibre reinforced concrete is suitable for bearing such loads and could replace conventional reinforcement schemes. In this contribution, a numerical model is presented, which allows to directly track the influence of important design parameters such as fibre type, fibre orientation, fibre content and concrete strength on the structural response of steel-fibre reinforced segments. For this purpose, submodels on the single fibre level are combined into a crack bridging model considering the fibre orientation and the fibre content. The submodels are integrated into a finite element model to perform numerical structural analyses. Two validation examples demonstrate that the modelling approach is capable to predict the failure loads as well as the crack development of fibre reinforced specimens subjected to localized loads. Finally, an optimization procedure is carried out to determine a robust and cost-effective design of a fibre reinforced segmental linings. A hybrid reinforcement scheme consisting of two layers of fibre reinforced concrete is employed in order to provide an improved material utilization. The thickness of the segment and the fibre content are optimized taking uncertainties of the material parameters and construction tolerances as uncertain a priori parameters into account. A sufficient load bearing capacity and serviceability performance under all possible conditions is ensured by the consideration of accepted failure probabilities as constraints in the optimization task. © 2022 Elsevier Ltd
    view abstractdoi: 10.1016/j.engstruct.2021.113752
  • 2022 • 537 Spectroscopy of nanoantenna-covered Cu2 O: Towards enhancing quadrupole transitions in Rydberg excitons
    Neubauer, A. and Heckötter, J. and Ubl, M. and Hentschel, M. and Panda, B. and Aßmann, M. and Bayer, M. and Giessen, H.
    Physical Review B 106 (2022)
    doi: 10.1103/PhysRevB.106.165305
  • 2022 • 536 Low-temperature ALD process development of 200 mm wafer-scale MoS2 for gas sensing application
    Neubieser, R.-M. and Wree, J.-L. and Jagosz, J. and Becher, M. and Ostendorf, A. and Devi, A. and Bock, C. and Michel, M. and Grabmaier, A.
    Micro and Nano Engineering 15 (2022)
    doi: 10.1016/j.mne.2022.100126
  • 2022 • 535 The value of (private) investor relations during the COVID-19 crisis
    Neukirchen, D. and Engelhardt, N. and Krause, M. and Posch, P.N.
    Journal of Banking and Finance (2022)
    We investigate the value of investor relations (IR) and find firms with strong IR to experience between five and eight percentage points higher stock returns than those with weak IR during the COVID-19 crisis. Firms with better-quality IR are also associated with higher investor loyalty and appear to have attracted significantly more institutional investors over the crisis period. This suggests that a firm's IR contributes to value generation by enhancing credibility with shareholders and by diversifying its shareholder base. After decomposing IR into public and private transmission channels, we find the private IR function to be the main driver of our results. © 2022 Elsevier B.V.
    view abstractdoi: 10.1016/j.jbankfin.2022.106450
  • 2022 • 534 THIN CONCRETE OVERLAYS WIT CARBON REINFORCEMENT ON DETERIORATED CONCRETE PAVEMENTS
    Neumann, J. and Breitenbücher, R.
    Acta Polytechnica CTU Proceedings 33 404-410 (2022)
    doi: 10.14311/APP.2022.33.0404
  • 2022 • 533 Controlling Transformer Magnetizing Offset Current in Isolated Phase-Shift Full-Bridge Converters Using a Luenberger Observer
    Neumann, A. and Meynen, S. and Rahmoun, A. and Ziegler, D. and Kirchartz, T.
    International Transactions on Electrical Energy Systems 2022 (2022)
    This paper proposes a flexible digital control scheme for isolated phase-shift full-bridge (PSFB) converters. The required transformer suffers from inevitable imbalance of magnetic flux resulting in an increased magnetizing DC-offset current that threatens system reliability due to saturation effects. The paper addresses two major issues of the occurrence of a magnetizing DC-offset current. First, caused by the change of duty cycle due to output power regulation and second caused by initial manufacturer tolerances of devices. In contrast to common methods the novel control scheme uses a Luenberger observer to estimate the magnetizing current requiring only simple measurement of transformer voltages without additional and lossy auxiliary networks. The observer model, in combination with a PI-controller, directly interventions the duty cycle and removes any DC-offset current resulting from both issues. A detailed deviation of the state-space model of the transformer and a subsequently design of the observer are presented. Simulation and experimental results on a PSFB prototype verify the principal functionality of the proposed control scheme to prevent transformer saturation. © 2022 Angelika Neumann et al.
    view abstractdoi: 10.1155/2022/9243429
  • 2022 • 532 Investigation of Laser-Induced Periodic Surface Structures Using Synthetic Optical Holography
    Neutsch, K. and Gurevich, E.L. and Hofmann, M.R. and Gerhardt, N.C.
    Nanomaterials 12 (2022)
    In this paper, the investigation of laser-induced periodic surface structures (LIPSSs) on a polycrystalline diamond substrate using synthetic optical holography (SOH) is demonstrated. While many techniques for LIPSS detection operate with sample contact and/or require preparation or processing of the sample, this novel technique operates entirely non-invasively without any processing of or contact with the LIPSS sample at all. The setup provides holographic amplitude and phase images of the investigated sample with confocally enhanced and diffraction-limited lateral resolution, as well as three-dimensional surface topography images of the periodic structures via phase reconstruction with one single-layer scan only. © 2022 by the authors. Licensee MDPI, Basel, Switzerland.
    view abstractdoi: 10.3390/nano12030505
  • 2022 • 531 Mechanical Behaviour and Failure Mode of High Interstitially Alloyed Austenite under Combined Compression and Cyclic Torsion
    Ngeru, T. and Kurtulan, D. and Karkar, A. and Hanke, S.
    Metals 12 (2022)
    multiaxial stress states frequently occur in technical components and, due to the multitude of possible load situations and variations in behaviour of different materials, are to date not fully predictable. This is particularly the case when loads lie in the plastic range, when strain accumulation, hardening and softening play a decisive role for the material reaction. This study therefore aims at adding to the understanding of material behaviour under complex load conditions. Fatigue tests conducted under cyclic torsional angles (5°, 7.5°, 10° and 15°), with superimposed axial static compression loads (250 MPa and 350 MPa), were carried out using smooth specimens at room temperature. A high nitrogen alloyed austenitic stainless steel (nickel free), was employed to determine not only the number of cycles to failure but particularly to aid in the understanding of the mechanical material reaction to the multiaxial stresses as well as modes of crack formation and growth. Experimental test results indicate that strain hardening occurs under the compressive strain, while at the same time cyclic softening is observable in the torsional shear stresses. Furthermore, the cracks’ nature is unusual with multiple branching and presence of cracks perpendicular in direction to the surface cracks, indicative of the varying multiaxial stress states across the samples’ cross section as cross slip is activated in different directions. In addition, it is believed that the static compressive stress facilitated the Stage I (mode II) crack to change direction from the axial direction to a plane perpendicular to the specimen’s axis. © 2022 by the authors. Licensee MDPI, Basel, Switzerland.
    view abstractdoi: 10.3390/met12010157
  • 2022 • 530 μs and ns twin surface dielectric barrier discharges operated in air: From electrode erosion to plasma characteristics
    Nguyen-Smith, R.T. and Böddecker, A. and Schücke, L. and Bibinov, N. and Korolov, I. and Zhang, Q.-Z. and Mussenbrock, T. and Awakowicz, P. and Schulze, J.
    Plasma Sources Science and Technology 31 (2022)
    Electrode erosion through continual long-timescale operation (60 min) of identical twin surface dielectric barrier discharges (twin SDBDs) powered either by a microsecond (μs) or a nanosecond timescale (ns) voltage source is investigated. The twin SDBDs are characterized using current-voltage measurements, optical emission spectroscopy, and phase integrated ICCD imaging. The temporally and spatially averaged gas temperature, consumed electric power, and effective discharge parameters (reduced electric field, and electron density) are measured. The μs twin SDBD is shown to operate in a filamentary mode while the ns twin SDBD is shown to operate in a more homogeneous mode (i.e. non filamentary). Despite a similarity of the effective discharge parameters in both the μs and ns twin SDBD, erosion of the nickel coated electrodes caused by operation of the twin SDBD differs strongly. Only the formation of a moderate number of nickel oxide species is observed on the surface of the ns twin SDBD electrodes. In contrast, the nickel coated electrodes are locally melted and considerably higher densities of oxides are observed around the eroded areas of the μs twin SDBD, due to the filamentary nature of the discharge. © 2022 The Author(s). Published by IOP Publishing Ltd.
    view abstractdoi: 10.1088/1361-6595/ac5452
  • 2022 • 529 Investigation of the thermomechanical loads on the bore surface during single-lip deep hole drilling of steel components
    Nickel, J. and Baak, N. and Walther, F. and Biermann, D.
    Procedia CIRP 108 805-810 (2022)
    doi: 10.1016/j.procir.2022.03.125
  • 2022 • 528 Ultralong one-dimensional plastic zone created in aluminum underneath a nanoscale indent
    Nie, Z.-Y. and Sato, Y. and Ogata, S. and Duarte, M.J. and Dehm, G. and Li, J. and Ma, E. and Xie, D.-G. and Shan, Z.-W.
    Acta Materialia 232 (2022)
    doi: 10.1016/j.actamat.2022.117944
  • 2022 • 527 A micromechanically motivated multiscale approach for residual distortion in laser powder bed fusion processes
    Noll, I. and Koppka, L. and Bartel, T. and Menzel, A.
    Additive Manufacturing 60 (2022)
    doi: 10.1016/j.addma.2022.103277
  • 2022 • 526 Study on the Effect of Electrolyte pH during Kolbe Electrolysis of Acetic Acid on Pt Anodes
    Nordkamp, M.O. and Mei, B. and Venderbosch, R. and Mul, G.
    ChemCatChem 14 (2022)
    Kolbe already discovered in 1849 that electrochemical oxidative decarboxylation of carboxylic acids is feasible and leads to formation of alkanes and CO2, via alkyl radical intermediates. We now show for Pt electrodes that Kolbe electrolysis of acetic acid is favored in electrolytes with a pH similar to, or larger than the pKa of acetic acid, suppressing the formation of O2. However extended duration of electrolysis of acetate at basic pH results in loss of Faradaic efficiency to ethane, compensated by the formation of methanol. This change in selectivity is likely caused by the dissolution of CO2 near the electrode-electrolyte interface, resulting in enlarged concentration of bicarbonate/carbonate. On the positively polarized, and oxidized Pt surface, these anions seem to inhibit homocoupling of methyl radicals to ethane. These results demonstrate that reaction selectivity in acetic acid (acetate) oxidation using oxidized Pt electrodes is determined by the pH and the anionic composition of the electrolyte. © 2022 The Authors. ChemCatChem published by Wiley-VCH GmbH.
    view abstractdoi: 10.1002/cctc.202200438
  • 2022 • 525 Controlled quantum dot array segmentation via highly tunable interdot tunnel coupling
    Nurizzo, M. and Jadot, B. and Mortemousque, P.-A. and Thiney, V. and Chanrion, E. and Dartiailh, M. and Ludwig, Ar. and Wieck, A.D. and Bäuerle, C. and Urdampilleta, M. and Meunier, T.
    Applied Physics Letters 121 (2022)
    Recent demonstrations using electron spins stored in quantum dot array as qubits are promising for developing a scalable quantum computing platform. An ongoing effort is, therefore, aiming at the precise control of the quantum dot parameters in larger and larger arrays which represents a complex challenge. Partitioning of the system with the help of the inter-dot tunnel barriers can lead to a simplification for tuning and offers a protection against unwanted charge displacement. In a triple quantum dot system, we demonstrate a nanosecond control of the inter-dot tunnel rate permitting to reach the two extreme regimes, large GHz tunnel coupling, and sub-Hz isolation between adjacent dots. We use this development to isolate a subpart of the array in a metastable configuration while performing charge displacement and readout in the rest of the system. The degree of control over tunnel coupling achieved in a unit cell should motivate future protocol development for tuning, manipulation, and readout including this capability. © 2022 Author(s).
    view abstractdoi: 10.1063/5.0105635
  • 2022 • 524 Microstructure property classification of nickel-based superalloys using deep learning
    Nwachukwu, U. and Obaied, A. and Horst, O.M. and Ali, M.A. and Steinbach, I. and Roslyakova, I.
    Modelling and Simulation in Materials Science and Engineering 30 (2022)
    Nickel-based superalloys have a wide range of applications in high temperature and stress domains due to their unique mechanical properties. Under mechanical loading at high temperatures, rafting occurs, which reduces the service life of these materials. Rafting is heavily affected by the loading conditions associated with plastic strain; therefore, understanding plastic strain evolution can help understand these material's service life. This research classifies nickel-based superalloys with respect to creep strain with deep learning techniques, a technique that eliminates the need for manual feature extraction of complex microstructures. Phase-field simulation data that displayed similar results to experiments were used to build a model with pre-trained neural networks with several convolutional neural network architectures and hyper-parameters. The optimized hyper-parameters were transferred to scanning electron microscopy images of nickel-based superalloys to build a new model. This fine-tuning process helped mitigate the effect of a small experimental dataset. The built models achieved a classification accuracy of 97.74% on phase-field data and 100% accuracy on experimental data after fine-tuning. © 2022 The Author(s). Published by IOP Publishing Ltd.
    view abstractdoi: 10.1088/1361-651X/ac3217
  • 2022 • 523 On-Demand Source of Dual-Rail Photon Pairs Based on Chiral Interaction in a Nanophotonic Waveguide
    Østfeldt, F.T. and González-Ruiz, E.M. and Hauff, N. and Wang, Y. and Wieck, A.D. and Ludwig, Ar. and Schott, R. and Midolo, L. and Sørensen, A.S. and Uppu, R. and Lodahl, P.
    PRX Quantum 3 (2022)
    Entanglement is the fuel of advanced quantum technology, enabling, e.g., measurement-based quantum computing and loss-tolerant encoding of quantum information. In photonics, entanglement has traditionally been generated probabilistically, requiring massive multiplexing for scaling up to many photons. An alternative approach utilizing quantum emitters in nanophotonic devices can realize deterministic generation of entangled photons. However, such sources generate polarization entanglement that is incompatible with spatial dual-rail qubit encoding employed in scalable photonic quantum-computing platforms utilizing integrated circuits. Here we propose and experimentally realize an on-demand source of dual-rail photon pairs using a quantum dot in a planar nanophotonic waveguide. The source exploits the cascaded decay of a biexciton state and chiral light-matter coupling to achieve deterministic generation of spatial dual-rail Bell pairs with the amount of entanglement determined by the chirality. The operational principle can readily be extended to multiphoton entanglement generation required for efficient preparation of resource states for photonic quantum computing. © 2022 authors. Published by the American Physical Society.
    view abstractdoi: 10.1103/PRXQuantum.3.020363
  • 2022 • 522 OPTIMIZATION OF CHARACTERIZATION ROUTINES FOR CARBON BLACKS USED IN ENERGY RELATED APPLICATIONS
    Özcan, F. and Amin, A.S. and Segets, D.
    Proceedings of WHEC 2022 - 23rd World Hydrogen Energy Conference: Bridging Continents by H2 824-826 (2022)
  • 2022 • 521 Magnetic properties of fcc and σ phases in equiatomic and off-equiatomic high-entropy Cantor alloys
    Özgün, Ö. and Koch, D. and Çaklr, A. and Tavşanoǧlu, T. and Donner, W. and Farle, M. and Acet, M.
    Physical Review B 106 (2022)
    doi: 10.1103/PhysRevB.106.214422
  • 2022 • 520 Cutting fluid behavior under consideration of chip formation during micro single-lip deep hole drilling of Inconel 718
    Oezkaya, E. and Baumann, A. and Michel, S. and Schnabel, D. and Eberhard, P. and Biermann, D.
    International Journal of Modelling and Simulation (2022)
    When micro-single-lip deep hole drilling the efficiency of the cutting fluid supply cannot be investigated experimentally due to the inaccessibility of the cutting zone. For this reason, this paper examines the cutting fluid behavior, taking into account the chip formation and the transient chip position, with the help of various combined simulation methods. Therefore, experimentally obtained chips are digitalized and converted into a Computer-Aided Design model for the following simulations. Furthermore, for a comparison of the simulations with the experiments, the velocity of the cutting fluid in the chip flute of the tool is measured by a similar Particle Image Velocimetry method. Then, a transient coupled particle simulation of Smoothed Particle Hydrodynamics and the Discrete Element Method is performed to obtain the transient chip positions along the chip flute under the influence of the cutting fluid. Based on these chip positions, a Computational Fluid Dynamics simulation follows to derive insights about the flow field and pressure field at certain points in time. This multi-physics simulation chain allows to deal with experimental results in a simulation context to gain further insights about the deep hole drilling process, which are experimentally inaccessible and allows further connections between experiment and simulation. © 2022 Informa UK Limited, trading as Taylor & Francis Group.
    view abstractdoi: 10.1080/02286203.2022.2042057
  • 2022 • 519 Experimental and computational analysis of the coolant distribution considering the viscosity of the cutting fluid during machining with helical deep hole drills
    Oezkaya, E. and Michel, S. and Biermann, D.
    Advances in Manufacturing (2022)
    An experimental analysis regarding the distribution of the cutting fluid is very difficult due to the inaccessibility of the contact zone within the bore hole. Therefore, suitable simulation models are necessary to evaluate new tool designs and optimize drilling processes. In this paper the coolant distribution during helical deep hole drilling is analyzed with high-speed microscopy. Micro particles are added to the cutting fluid circuit by a developed high-pressure mixing vessel. After the evaluation of suitable particle size, particle concentration and coolant pressure, a computational fluid dynamics (CFD) simulation is validated with the experimental results. The comparison shows a very good model quality with a marginal difference for the flow velocity of 1.57% between simulation and experiment. The simulation considers the kinematic viscosity of the fluid. The results show that the fluid velocity in the chip flutes is low compared to the fluid velocity at the exit of the coolant channels of the tool and drops even further between the guide chamfers. The flow velocity and the flow pressure directly at the cutting edge decrease to such an extent that the fluid cannot generate a sufficient cooling or lubrication. With the CFD simulation a deeper understanding of the behavior and interactions of the cutting fluid is achieved. Based on these results further research activities to improve the coolant supply can be carried out with great potential to evaluate new tool geometries and optimize the machining process. © 2022, The Author(s).
    view abstractdoi: 10.1007/s40436-021-00383-w
  • 2022 • 518 Analysis of the cutting fluid behavior with a modified micro single-lip deep hole drilling tool
    Oezkaya, E. and Baumann, A. and Eberhard, P. and Biermann, D.
    CIRP Journal of Manufacturing Science and Technology 38 93-104 (2022)
    doi: 10.1016/j.cirpj.2022.04.003
  • 2022 • 517 A simple and efficient adaptive time stepping technique for low-order operator splitting schemes applied to cardiac electrophysiology
    Ogiermann, D. and Perotti, L.E. and Balzani, D.
    International Journal for Numerical Methods in Biomedical Engineering (2022)
    doi: 10.1002/cnm.3670
  • 2022 • 516 Modeling and Control Design of a Contact-Based, Electrostatically Actuated Rotating Sphere
    Olbrich, M. and Farny, M. and Hoffmann, M. and Ament, C.
    Actuators 11 (2022)
    doi: 10.3390/act11030090
  • 2022 • 515 Influence of temperature, surface composition and electrochemical environment on 2-propanol decomposition at the Co3O4 (001)/H2O interface
    Omranpoor, A.H. and Kox, T. and Spohr, E. and Kenmoe, S.
    Applied Surface Science Advances 12 (2022)
    Ab initio molecular dynamics simulations of a single hydrated 2-propanol molecule were performed to study the role of temperature, surface structure and electrochemical environment for the oxidation of 2-propanol to acetone at the Co3O4 (001)/H2O interface. On the A-terminated and B-terminated surfaces, which differ in the relative number of Co2+ and Co3+ ions at the surface, 2-propanol adsorbs molecularly on the Co2+ and Co3+ sites, respectively. In both cases, no C-H bond cleavage is observed at room temperature. However, under oxidative conditions, which are modeled here by partial dehydrogenation of the mixed hydroxyl/water adsorbate layer, dehydrogenation of the alcoholic OH group is observed on both surface terminations. As a result, adsorbed 2-propanolate is formed. The reaction on the less hydroxylated B-terminated surface further proceeds with C-H bond cleavage at the 2-carbon atom. The oxidation product acetone remains adsorbed on the Co3+ site during the simulation period of approximately 20 ps. Both deprotonation steps are aided by the presence of the adsorbed hydroxyl groups in the vicinity of the adsorbed alcohol molecule, because both hydrogen atoms from the reactand molecule are transferred as protons to form adsorbed water molecules. Different from the case of the partially dehydrogenated environment, raising the system temperature from 300 to 450 K, which can be considered a simple model for high temperature thermal catalysis, does not lead to oxidation via C–H dehydrogenation of the 2-propanol molecule. © 2022
    view abstractdoi: 10.1016/j.apsadv.2022.100319
  • 2022 • 514 A thermo-viscoplasticity model for metals over wide temperature ranges- application to case hardening steel
    Oppermann, P. and Denzer, R. and Menzel, A.
    Computational Mechanics 69 541-563 (2022)
    In this contribution, a model for the thermomechanically coupled behaviour of case hardening steel is introduced with application to 16MnCr5 (1.7131). The model is based on a decomposition of the free energy into a thermo-elastic and a plastic part. Associated viscoplasticity, in terms of a temperature-depenent Perzyna-type power law, in combination with an isotropic von Mises yield function takes respect for strain-rate dependency of the yield stress. The model covers additional temperature-related effects, like temperature-dependent elastic moduli, coefficient of thermal expansion, heat capacity, heat conductivity, yield stress and cold work hardening. The formulation fulfils the second law of thermodynamics in the form of the Clausius–Duhem inequality by exploiting the Coleman–Noll procedure. The introduced model parameters are fitted against experimental data. An implementation into a fully coupled finite element model is provided and representative numerical examples are presented showing aspects of the localisation and regularisation behaviour of the proposed model. © 2021, The Author(s).
    view abstractdoi: 10.1007/s00466-021-02103-4
  • 2022 • 513 Metallization of PET fibers in supercritical carbon dioxide and potential applications in the textile sector
    Opwis, K. and Plohl, D. and Schneider, J. and Seithuemmer, J. and Wunschik, D.S. and Gutmann, J.S.
    Journal of Supercritical Fluids 191 (2022)
    doi: 10.1016/j.supflu.2022.105722
  • 2022 • 512 γ-BaFe2O4: a fresh playground for room temperature multiferroicity
    Orlandi, F. and Delmonte, D. and Calestani, G. and Cavalli, E. and Gilioli, E. and Shvartsman, V.V. and Graziosi, P. and Rampino, S. and Spaggiari, G. and Liu, C. and Ren, W. and Picozzi, S. and Solzi, M. and Casappa, M. and Mezzadri, F.
    Nature Communications 13 (2022)
    doi: 10.1038/s41467-022-35669-5
  • 2022 • 511 About the effectiveness of a hydrophobic surface treatment of Baumberger Sandstones
    Orlowsky, J. and Groh, M. and Braun, F.
    Environmental Earth Sciences 81 (2022)
    The Baumberger Sandstone, a sandy limestone, is used since the Middle Ages as a building material not only in the surrounding Münster region of North Rhine-Westphalia (Germany), where it is quarried since to date. To prevent the ingress of water and reduce weathering processes conservation methods, mostly in form of organosilicon compounds, were used. This study deals with the performance of applied hydrophobing agents on Baumberger Sandstone samples and their influence on the weathering processes during long-term exposure. The samples were exposed at several locations in Germany to different climatic conditions for up to 24 years. Afterwards, investigations concerning the water absorption behaviour and the degree of superficial damages were carried out. With an evaluation method on basis of NMR measurements, a very low and uneven distributed effective hydrophobic zone could be detected. This caused an ingress of water in the uppermost part and a progressive weathering of investigated natural stones. Thus the hydrophobic surface treatment did not lead to a significant decrease of weathering or damaging processes. Based on these results a hydrophobic surface treatment of Baumberger Sandstone seems not to be suitable. © 2022, The Author(s).
    view abstractdoi: 10.1007/s12665-022-10186-2
  • 2022 • 510 MORTAR WITH RECYCLED CARBON FIBRES AS ACTIVE CHLORIDE BARRIER FOR REINFORCED CONCRETE STRUCTURES
    Orlowsky, J. and Harnisch, J. and Kunz, A. and Fache, K. and Faulhaber, A. and Büttner, T.
    fib Symposium 685-694 (2022)
  • 2022 • 509 Locally varying formation of nanoclusters across a low-intensity ultra-short laser spot
    Osterloh, N. and Pan, T. and Morgenstern, K.
    Nanoscale Horizons 8 55-62 (2022)
    doi: 10.1039/d2nh00386d
  • 2022 • 508 Qubit Bias using a CMOS DAC at mK Temperatures
    Otten, R. and Schreckenberg, L. and Vliex, P. and Ritzmann, J. and Ludwig, Ar. and Wieck, A.D. and Bluhm, H.
    ICECS 2022 - 29th IEEE International Conference on Electronics, Circuits and Systems, Proceedings (2022)
    doi: 10.1109/ICECS202256217.2022.9971043
  • 2022 • 507 A federated infrastructure for European data spaces
    Otto, B.
    Communications of the ACM 65 44-45 (2022)
    doi: 10.1145/3512341
  • 2022 • 506 Data spaces for data ecosystems
    Otto, B.
    CEUR Workshop Proceedings 3306 1-3 (2022)
  • 2022 • 505 INFLUENCE OF STEEL FIBERS ON THE FATIGUE BEHAVIOR OF HIGH-PERFORMANCE CONCRETES UNDER CYCLIC LOADING
    Ov, D. and Breitenbücher, R.
    Acta Polytechnica CTU Proceedings 33 437-443 (2022)
    doi: 10.14311/APP.2022.33.0437
  • 2022 • 504 Ceramic-in-Polymer Hybrid Electrolytes with Enhanced Electrochemical Performance
    Overhoff, G.M. and Ali, M.Y. and Brinkmann, J.-P. and Lennartz, P. and Orthner, H. and Hammad, M. and Wiggers, H. and Winter, M. and Brunklaus, G.
    ACS Applied Materials and Interfaces 14 53636-53647 (2022)
    doi: 10.1021/acsami.2c13408
  • 2022 • 503 Influence of solvent and salt on kinetics and equilibrium of esterification reactions
    Pabsch, D. and Lindfeld, J. and Schwalm, J. and Strangmann, A. and Figiel, P. and Sadowski, G. and Held, C.
    Chemical Engineering Science 263 (2022)
    doi: 10.1016/j.ces.2022.118046
  • 2022 • 502 Solubility of Electrolytes in Organic Solvents: Solvent-Specific Effects and Ion-Specific Effects
    Pabsch, D. and Figiel, P. and Sadowski, G. and Held, C.
    Journal of Chemical and Engineering Data 67 2706-2718 (2022)
    doi: 10.1021/acs.jced.2c00203
  • 2022 • 501 Synthesis and Characterization of Cationic Hydrogels from Thiolated Copolymers for Independent Manipulation of Mechanical and Chemical Properties of Cell Substrates
    Pätzold, F. and Stamm, N. and Kamps, D. and Specht, M. and Bolduan, P. and Dehmelt, L. and Weberskirch, R.
    Macromolecular Bioscience (2022)
    Cells sense both mechanical and chemical properties in their environment and respond to these inputs with altered phenotypes. Precise and selective experimental manipulations of these environmental cues require biocompatible synthetic materials, for which multiple properties can be fine-tuned independently from each other. For example, cells typically show critical thresholds for cell adhesion as a function of substrate parameters such as stiffness and the degree of functionalization. However, the choice of tailor-made, defined materials to produce such cell adhesion substrates is still very limited. Here, a platform of synthetic hydrogels based on well-defined thiolated copolymers is presented. Therefore, four disulfide crosslinked hydrogels of different composition by free radical polymerization are prepared. After cleavage with dithiothreitol, four soluble copolymers P1–P4 with 0–96% cationic monomer content are obtained. P1 and P4 are then combined with PEGDA3500 as a crosslinker, to fabricate 12 hydrogels with variable elasticity, ranging from 8.1 to 26.3 kPa and cationic group concentrations of up to 350 µmol cm−3. Systematic analysis using COS7 cells shows that all of these hydrogels are nontoxic. However, successful cell adhesion requires both a minimal elasticity and a minimal cationic group concentration. © 2022 The Authors. Macromolecular Bioscience published by Wiley-VCH GmbH
    view abstractdoi: 10.1002/mabi.202100453
  • 2022 • 500 Swing Up and Balance of an Inverted Pendulum Using Reinforced Learning Approach Coupled with a Proportional-Integral-Derivative Controller
    Pal, A.K. and Nestorović, T.
    International Conference on Electrical, Computer, Communications and Mechatronics Engineering, ICECCME 2022 (2022)
    doi: 10.1109/ICECCME55909.2022.9988506
  • 2022 • 499 A high-throughput effector screen identifies a novel small molecule scaffold for inhibition of ten-eleven translocation dioxygenase 2
    Palei, S. and Weisner, J. and Vogt, M. and Gontla, R. and Buchmuller, B. and Ehrt, C. and Grabe, T. and Kleinbölting, S. and Müller, M. and Clever, G.H. and Rauh, D. and Summerer, D.
    RSC Medicinal Chemistry (2022)
    Ten-eleven translocation dioxygenases (TETs) are the erasers of 5-methylcytosine (mC), the central epigenetic regulator of mammalian DNA. TETs convert mC to three oxidized derivatives with unique physicochemical properties and inherent regulatory potential, and it initializes active demethylation by the base excision repair pathway. Potent small molecule inhibitors would be useful tools to study TET functions by conditional control. To facilitate the discovery of such tools, we here report a high-throughput screening pipeline and its application to screen and validate 31.5k compounds for inhibition of TET2. Using a homogenous fluorescence assay, we discover a novel quinoline-based scaffold that we further validate with an orthogonal semi-high throughput MALDI-MS assay for direct monitoring of substrate turnover. Structure-activity relationship (SAR) studies involving >20 derivatives of this scaffold led to the identification of optimized inhibitors, and together with computational studies suggested a plausible model for its mode of action. © 2022 RSC.
    view abstractdoi: 10.1039/d2md00186a
  • 2022 • 498 Lithium-Ion Battery Anodes Based on Silicon Nitride Nanoparticles as Active Material and Vertically Aligned Carbon Nanotubes as Electrically Conductive Scaffolding
    Pandel, D. and Neises, J. and Kilian, S.O. and Wiggers, H. and Benson, N.
    ACS Applied Energy Materials 5 14807-14814 (2022)
    doi: 10.1021/acsaem.2c02183
  • 2022 • 497 Revealing Weak Dimensional Confinement Effects in Excitonic Silver/Bismuth Double Perovskites
    Pantaler, M. and Diez-Cabanes, V. and Queloz, V.I.E. and Sutanto, A. and Schouwink, P.A. and Pastore, M. and García-Benito, I. and Nazeeruddin, M.K. and Beljonne, D. and Lupascu, D.C. and Quarti, C. and Grancini, G.
    JACS Au 2 136-149 (2022)
    doi: 10.1021/jacsau.1c00429
  • 2022 • 496 Quantum Interference between Integrated and Independently Controlled Quantum Dots
    Papon, C. and Wang, Y. and Uppu, R. and Scholz, S. and Wieck, A.D. and Ludwig, Ar. and Lodahl, P. and Midolo, L.
    2022 Conference on Lasers and Electro-Optics, CLEO 2022 - Proceedings (2022)
    We realize a quantum photonic circuit enabling the resonant excitation of multiple quantum emitters. Using independent electrical control, we demonstrate quantum interference between two embedded quantum dots in a single device. Our result represents a crucial step towards on-chip multi-photon generation for quantum information applications. © Optica Publishing Group 2022, © 2022 The Author(s)
    view abstract
  • 2022 • 495 An experimental/numerical investigation of non-reacting turbulent flow in a piloted premixed Bunsen burner
    Pareja, J. and Lipkowicz, T. and Inanc, E. and Carter, C.D. and Kempf, A. and Boxx, I.
    Experiments in Fluids 63 (2022)
    Abstract: In this paper, an experimental study of the non-reacting turbulent flow field characteristics of a piloted premixed Bunsen burner designed for operational at elevated pressure conditions is presented. The generated turbulent flow fields were experimentally investigated at atmospheric and elevated pressure by means of high-speed particle image velocimetry (PIV). The in-nozzle flow through the burner was computed using large-eddy simulation (LES), and the turbulent flow field predicted at the burner exit was compared against the experimental results. The findings show that the burner yields a reasonably homogeneous, nearly isotropic turbulence at the nozzle exit with highly reproducible boundary conditions that can be well predicted by numerical simulations. Similar levels of turbulence intensities and turbulent length scales were obtained at varied pressures and bulk velocities with turbulent Reynolds numbers up to 5300. This work demonstrates the burner’s potential for the study of premixed flames subject to intermediate and extreme turbulence at the elevated pressure conditions found in gas turbine combustors. Graphical abstract: [Figure not available: see fulltext.]. © 2022, The Author(s).
    view abstractdoi: 10.1007/s00348-021-03377-3
  • 2022 • 494 Hybrid biodegradable electrospun scaffolds based on poly(l-lactic acid) and reduced graphene oxide with improved piezoelectric response
    Pariy, I.O. and Chernozem, R.V. and Chernozem, P.V. and Mukhortova, Y.R. and Skirtach, A.G. and Shvartsman, V.V. and Lupascu, D.C. and Surmeneva, M.A. and Mathur, S. and Surmenev, R.A.
    Polymer Journal 54 1237-1252 (2022)
    Piezoelectric poly-L-lactide (PLLA) is a biodegradable polymer used in various biomedical applications. However, tailoring and controlling the structure of PLLA to enhance its piezoelectric response remains a challenge. In this work, extensive characterization was performed to reveal the effect of the reduced graphene oxide (rGO) content (0.2, 0.7, and 1.0 wt%) on the morphology, structure, thermal and piezoelectric behavior of PLLA scaffolds. Randomly oriented homogeneous fibers and a quasi-amorphous structure for pure PLLA and hybrid PLLA-rGO scaffolds were revealed. The addition of rGO affected the molecular structure of the PLLA scaffolds: for example, the number of polar C=O functional groups was increased. Increasing the content of rGO to 1 wt% resulted in decreased glass transition and melting temperatures and increased the degree of crystallinity of the scaffolds. The addition of 0.2 wt% rGO enhanced the effective local vertical and lateral piezoresponses by 2.3 and 15.4 times, respectively, in comparison with pure PLLA fibers. The presence of the shear piezoelectric α-phase (P212121) in uniaxially oriented PLLA fibers and C=O bond rotation in the polymer chains explained the observed piezoresponse. Thus, this study revealed routes to prepare hybrid biodegradable scaffolds with enhanced piezoresponse for tissue engineering applications. © 2022, The Author(s), under exclusive licence to The Society of Polymer Science, Japan.
    view abstractdoi: 10.1038/s41428-022-00669-1
  • 2022 • 493 Ferromagnetic domain wall manipulation using optically induced thermal gradients
    Parlak, U. and Adam, R. and Bürgler, D.E. and Duchoň, T. and Nemšák, S. and Wang, F. and Greb, C. and Heidtfeld, S. and Schneider, C.M.
    Journal of Magnetism and Magnetic Materials 560 (2022)
    Magnetic domain walls can be manipulated by thermal gradients. A local thermal gradient can be generated by illuminating the surface of a thin film sample with a focused femtosecond laser beam in relation to its intensity profile. We investigate the magnetic domain structures of a ferromagnetic [Co/Pt]3 multilayers under laser illumination. We create thermal gradients by either a stationary or a moving pulsed laser beam. Following the laser illumination, we use x-ray circular magnetic dichroism as a magnetic contrast mechanism in photoemission electron microscopy in order to image the magnetic domains. Our experimental results show that the domain walls drift towards the regions of higher temperature and align themselves parallel to the laser beam motion, leading to domains elongated in that direction. © 2022
    view abstractdoi: 10.1016/j.jmmm.2022.169441
  • 2022 • 492 Influence of crystal orientation on twinning in austenitic stainless-steel during single micro-asperity tribology and nanoindentation
    Patil, P. and Lee, S. and Dehm, G. and Brinckmann, S.
    Wear 504-505 (2022)
    doi: 10.1016/j.wear.2022.204403
  • 2022 • 491 Ion Implantation Enhanced Exfoliation Efficiency of V2AlC Single Crystals: Implications for Large V2CT zNanosheet Production
    Pazniak, H. and Hurand, S. and Guignard, N. and Célérier, S. and Wiedwald, U. and Ouisse, T. and David, M.-L. and Mauchamp, V.
    ACS Applied Nano Materials 5 8029-8037 (2022)
    MXenes are two-dimensional transition-metal carbides and nitrides with an attractive combination of physicochemical properties, gaining notable potential in many applications. Currently, MXene synthesis is mainly performed from powder precursors whose purity and grain size define the quality and flake size of 2D sheets, typically not exceeding 2-3 μm. In this work, we successfully synthesize macroscopic nanolayered V2CTzMXenes with lateral dimensions larger than 25 μm from a V2AlC single crystal by exploiting a new strategy based on ion implantation. Ne2+ion implantation of the single-crystal precursor is applied to introduce defects in the crystal structure of V2AlC, which facilitates chemical etching and drastically reduces the etching time down to 8 h (∼10 times lower as compared to conventional synthesis from powder precursors). The quality and morphology of exfoliated macroscopic MXene multilayers have been comprehensively studied by performing detailed analyses based on different kinds of microscopies and spectroscopies. The obtained macroscopic flakes are ideal objects to study the intrinsic physical properties of V2CTzMXenes and explore their potential application, in particular, as membranes. © 2022 American Chemical Society. All rights reserved.
    view abstractdoi: 10.1021/acsanm.2c01143
  • 2022 • 490 Machine-learning-based surrogate modeling of microstructure evolution using phase-field
    Peivaste, I. and Siboni, N.H. and Alahyarizadeh, G. and Ghaderi, R. and Svendsen, B. and Raabe, D. and Mianroodi, J.R.
    Computational Materials Science 214 (2022)
    Phase-field-based models have become common in material science, mechanics, physics, biology, chemistry, and engineering for the simulation of microstructure evolution. Yet, they suffer from the drawback of being computationally very costly when applied to large, complex systems. To reduce such computational costs, a Unet-based artificial neural network is developed as a surrogate model in the current work. Training input for this network is obtained from the results of the numerical solution of initial–boundary-value problems (IBVPs) based on the Fan–Chen model for grain microstructure evolution. In particular, about 250 different simulations with varying initial order parameters are carried out and 200 frames of the time evolution of the phase fields are stored for each simulation. The network is trained with 90% of this data, taking the ith frame of a simulation, i.e. order parameter field, as input, and producing the (i+1)-th frame as the output. Evaluation of the network is carried out with a test dataset consisting of 2200 microstructures based on different configurations than originally used for training. The trained network is applied recursively on initial order parameters to calculate the time evolution of the phase fields. The results are compared to the ones obtained from the conventional numerical solution in terms of the errors in order parameters and the system's free energy. The resulting order parameter error averaged over all points and all simulation cases is 0.005 and the relative error in the total free energy in all simulation boxes does not exceed 1%. © 2022 Elsevier B.V.
    view abstractdoi: 10.1016/j.commatsci.2022.111750
  • 2022 • 489 Opening the pathway towards a scalable electrochemical semi-hydrogenation of alkynols via earth-abundant metal chalcogenides
    Pellumbi, K. and Wickert, L. and Kleinhaus, J.T. and Wolf, J. and Leonard, A. and Tetzlaff, D. and Goy, R. and Medlock, J.A. and junge Puring, K. and Cao, R. and Siegmund, D. and Apfel, U.-P.
    Chemical Science (2022)
    doi: 10.1039/d2sc04647d
  • 2022 • 488 Quantitative analysis of grain boundary diffusion, segregation and precipitation at a sub-nanometer scale
    Peng, Z. and Meiners, T. and Lu, Y. and Liebscher, C.H. and Kostka, A. and Raabe, D. and Gault, B.
    Acta Materialia 225 (2022)
    Grain boundaries are intrinsic and omnipresent microstructural imperfections in polycrystalline and nanocrystalline materials. They are short-circuit diffusion paths and preferential locations for alloying elements, dopants, and impurities segregation. They also facilitate heterogeneous nucleation and the growth of secondary phases. Therefore, grain boundaries strongly influence many materials' properties and their stabilities during application. Here, we propose an approach to measure diffusion, segregation, and segregation-induced precipitation at grain boundaries at a sub-nanometer scale by combining atom probe tomography and scanning transmission electron microscopy. Nanocrystalline multilayer thin films with columnar grain structure were used as a model system as they offer a large area of random high-angle grain boundaries and inherent short diffusion distance. Our results show that the fast diffusion flux proceeds primarily through the core region of the grain boundary, which is around 1 nm. While the spatial range that the segregated solute atoms occupied is larger: below the saturation level, it is 1,2 nm; as the segregation saturates, it is 2–3.4 nm in most grain boundary areas. Above 3.4 nm, secondary phase nuclei seem to form. The observed distributions of the solutes at the matrix grain boundaries evidence that even at a single grain boundary, different regions accommodate different amounts of solute atoms and promote secondary phase nuclei with different compositions, which is caused by its complex three-dimensional topology. © 2021 Acta Materialia Inc.
    view abstractdoi: 10.1016/j.actamat.2021.117522
  • 2022 • 487 General Surface-Casting Synthesis of Mesoporous Metal Oxides with Hollow Structures and Ultrahigh Surface Areas
    Peng, Y. and Song, S. and Liu, F. and Yin, Z. and Zhong, Y. and Yi, X. and Zheng, A. and Schüth, F. and Gu, D.
    Chemistry of Materials 34 7042-7057 (2022)
    Metal oxides with high specific surface areas have essential roles in numerous applications. Over the past decades, various efforts to increase their surface areas have been made. One of the most important ways is to create nanopores inside the solids, resulting in mesoporous materials. However, ordered mesoporous metal oxides with crystalline framework, regular arrangement of pores, and very high surface areas have scarcely been achieved due to structural collapse during the high-temperature treatment. Herein, a family of mesoporous metal oxides with crystalline framework, hollow mesostructure, and ultrahigh surface area is synthesized by a surface-casting method. The strong interaction between the silica template surface and the precursors is vital in the formation of a thin layer of metal oxides on the nanopore surface. Metal oxides with tubular, hollow sphere, or hollow vesicle structures can be obtained after the templates are removed. The obtained surface-cast oxides (SCOs), including ZrO2, Fe2O3, CrOx, TiO2, and others, exhibit ultrahigh surface areas of up to 400 m2g-1. The high surface area feature of the SCO material can even be retained after calcination up to 800 °C. Catalytic tests reveal that the SCO materials with more exposed active sites have better activities than their conventional counterparts. © 2022 American Chemical Society. All rights reserved.
    view abstractdoi: 10.1021/acs.chemmater.2c01493
  • 2022 • 486 Semi-flowable Zn semi-solid electrodes as renewable energy carrier for refillable Zn–Air batteries
    Perez-Antolin, D. and Schuhmann, W. and Palma, J. and Ventosa, E.
    Journal of Power Sources 536 (2022)
    Today's society relies on energy storage on a day-to-day basis, e.g. match energy production and demand from renewable sources, power a variety of electronics, and enable emerging technologies. As a result, a vast range of energy storage technologies has emerged in the last decades. Among them, rechargeable Zn–Air batteries have held great promises for a long time. However, the severe challenges related to the reversible O2 reactions and poor cyclability at the positive and negative electrodes, respectively, have severely hindered the success of this technology. Herein, electrically-conducting and semi-flowable Zn semi-solid electrodes are proposed to revive the appealing concept of a mechanically–rechargeable alkaline Zn–Air battery, in which the spent negative electrodes are easily substituted at the end of the discharge process (refillable primary battery). In this proof-of-concept study energy densities of ca. 1500 Wh L−1 (1350 Ah Lelectrode−1 and utilization rate of 85%) are achieved thanks to the compromised flowability of the proposed Zn semi-solid electrodes. In this way, semi-solid Zn electrodes become a type of green energy carrier having intrinsic advantages over gas and liquid fuels. Zn semi-flowable electrode can be generated elsewhere using renewable sources, easily stored, transported, and used to produce electricity. © 2022 The Authors
    view abstractdoi: 10.1016/j.jpowsour.2022.231480
  • 2022 • 485 Crystal Structures of Two Titanium Phosphate-Based Proton Conductors: Ab Initio Structure Solution and Materials Properties
    Petersen, H. and Stegmann, N. and Fischer, M. and Zibrowius, B. and Radev, I. and Philippi, W. and Schmidt, W. and Weidenthaler, C.
    Inorganic Chemistry 61 2379-2390 (2022)
    Transition-metal phosphates show a wide range of chemical compositions, variations of the valence states, and crystal structures. They are commercially used as solid-state catalysts, cathode materials in rechargeable batteries, or potential candidates for proton-exchange membranes in fuel cells. Here, we report on the successful ab initio structure determination of two novel titanium pyrophosphates, Ti(III)p and Ti(IV)p, from powder X-ray diffraction (PXRD) data. The low-symmetry space groups P21/c for Ti(III)p and P1¯ for Ti(IV)p required the combination of spectroscopic and diffraction techniques for structure determination. In Ti(III)p, trivalent titanium ions occupy the center of TiO6 polyhedra, coordinated by five pyrophosphate groups, one of them as a bidentate ligand. This secondary coordination causes the formation of one-dimensional six-membered ring channels with a diameter dmax of 3.93(2) Å, which is stabilized by NH4+ ions. Annealing Ti(III)p in inert atmospheres results in the formation of a new compound, denoted as Ti(IV)p. The structure of this compound shows a similar three-dimensional framework consisting of [PO4]3- tetrahedra and TiIV+O6 octahedra and an empty one-dimensional channel with a diameter dmax of 5.07(1) Å. The in situ PXRD of the transformation of Ti(III)p to Ti(IV)p reveals a two-step mechanism, i.e., the decomposition of NH4+ ions in a first step and subsequent structure relaxation. The specific proton conductivity and activation energy of the proton migration of Ti(III)p, governed by the Grotthus mechanism, belong to the highest and lowest, respectively, ever reported for this class of materials, which reveals its potential application in electrochemical devices like fuel cells and water electrolyzers in the intermediate temperature range. © 2021 The Authors. Published by American Chemical Society.
    view abstractdoi: 10.1021/acs.inorgchem.1c02613
  • 2022 • 484 Operando X-ray Powder Diffraction Study of Mechanochemical Activation Tested for the CO Oxidation over Au@Fe2O3 as Model Reaction
    Petersen, H. and De Bellis, J. and Leiting, S. and Das, S.M. and Schmidt, W. and Schüth, F. and Weidenthaler, C.
    ChemCatChem 14 (2022)
    Mechanochemistry has proven to be an excellent green synthesis method for preparing organic, pharmaceutical, and inorganic materials. Mechanocatalysis, inducing a catalytic reaction by mechanical forces, is an emerging field because neither external temperature nor pressure inputs are required. Previous studies reported enhanced catalytic activity during the mechanical treatment of supported gold catalysts for CO oxidation. So far, the processes inside the milling vessel during mechanocatalysis could not be monitored. In this work, the results of high-energy operando X-ray powder diffraction experiments and online gas analysis will be reported. A specific milling setup with a custom-made vessel and gas dosing system was developed. To prove the feasibility of the experimental setup for operando diffraction studies during mechanocatalysis, the CO oxidation with Au@Fe2O3 as a catalyst was selected as a well-known model reaction. The operando studies enabled monitoring morphology changes of the support as well as changes in the crystallite size of the gold catalyst. The change of the crystal size is directly correlated to changes in the active surface area and thus to the CO2 yield. The studies confirm the successful implementation of the operando setup, and its potential to be applied to other catalytic reactions. © 2022 The Authors. ChemCatChem published by Wiley-VCH GmbH.
    view abstractdoi: 10.1002/cctc.202200703
  • 2022 • 483 Gold(I) NHC Catalysts Immobilized to Amphiphilic Block Copolymers: A Versatile Approach to Micellar Gold Catalysis in Water
    Petersen, H. and Ballmann, M. and Krause, N. and Weberskirch, R.
    ChemCatChem 14 (2022)
    Fifteen gold(I)-NHC-functionalized amphiphilic block copolymers that differ in the type of linker (ethyl, pentyl, octyl and benzyl) that attaches the gold(I) NHC catalyst to the block copolymer backbone, as well as, the substitution pattern of the NHC ligand (i. e. mesityl, methyl, 2,6-diisopropylphenyl and n-hexyl) were synthesized by a reversible addition and fragmentation transfer (RAFT) polymerization process. Micelle formation of the gold(I) NHC polymers was analyzed by electron microscopy and dynamic light scattering and revealed spherical and rod-like particles from 12 to 96 nm. In the micellar, gold(I) catalyzed cycloisomerization of an allene to the corresponding dihydrofuran, linker flexibility and substitution pattern of the NHC-ligand showed a strong effect on the catalytic activity. Best results were obtained were obtained for gold(I) NHC catalysts bound to the polymer backbone by pentyl linker whereas the rather stiff benzyl linker gave lowest catalyst conversion. Moreover, the polymer catalyst could be recycled in four consecutive runs and gave activities from 35 to 84 % in the fourth run and underscores the importance of fine tuning structural parameters to achieve high conversion under micellar reaction conditions. © 2022 The Authors. ChemCatChem published by Wiley-VCH GmbH.
    view abstractdoi: 10.1002/cctc.202200727
  • 2022 • 482 A review of recent developments for the in situ/operando characterization of nanoporous materials
    Petersen, H. and Weidenthaler, C.
    Inorganic Chemistry Frontiers 9 4244-4271 (2022)
    This is a review on up-to-date in situ/operando methods for a comprehensive characterization of nanoporous materials. The group of nanoporous materials is constantly growing, and with it, the variety of possible applications. Nanoporous materials include, among others, porous carbon materials, mesoporous silica, mesoporous transition metal oxides, zeolites, metal-organic frameworks (MOFs), or polymers. They are used as adsorbents, for gas storage, as catalysts, or for electrochemical applications to name just a few technical applications. Characterization of these materials has evolved from pure ex situ examination to increasingly complex in situ or operando methods. Monitoring nanoporous materials under reaction conditions allows for establishing structure-property relationships. This enables nanoporous materials to be adapted and optimized for specific processes. Recent developments on well-established but also exciting emerging methods for future applications will be discussed. The examples include in situ powder diffraction, total and small angle scattering, environmental electron microscopy, coupled with focused ion beam cutting, or X-ray tomography. This article will provide a useful reference to practitioners for in situ/operando characterization of nanoporous materials. © 2022 The Royal Society of Chemistry.
    view abstractdoi: 10.1039/d2qi00977c
  • 2022 • 481 Detecting material defects during turning of DA718 components
    Pfirrmann, D. and Wiederkehr, P.
    Procedia CIRP 108 619-623 (2022)
    Rotating turbine components of an aircraft engine are subjected to high thermal and mechanical alternating loads. The occurrence of material defects can have devastating effects and can even lead to component failure. However, many of these defects are not detected until very late in the production chain. This paper focuses on the detection of defects during the turning process of nickel-based alloy DA718 based on the analysis of measured cutting forces. For this purpose, the knowledge gained from previous experiments with synthetically produced defects were validated on real defects detected on series production parts. The applied measurement setup will be discussed and evaluated with regard to a series application. © 2022 The Authors.
    view abstractdoi: 10.1016/j.procir.2022.03.098
  • 2022 • 480 Thermicity of the Decomposition of Oxygen Functional Groups on Cellulose-Derived Chars
    Pflieger, C. and Eckhard, T. and Schmitz, G. and Angenent, V. and Göckeler, M. and Senneca, O. and Schmid, R. and Cerciello, F. and Muhler, M.
    ACS Omega 7 48606-48614 (2022)
    doi: 10.1021/acsomega.2c07429
  • 2022 • 479 Thermodynamic effects on single cavitation bubble dynamics under various ambient temperature conditions
    Phan, T.-H. and Kadivar, E. and Nguyen, V.-T. and El Moctar, O. and Park, W.-G.
    Physics of Fluids 34 (2022)
    doi: 10.1063/5.0076913
  • 2022 • 478 Low-temperature ALD/MLD growth of alucone and zincone thin films from non-pyrophoric precursors
    Philip, A. and Mai, L. and Ghiyasi, R. and Devi, A. and Karppinen, M.
    Dalton Transactions 51 14508-14516 (2022)
    doi: 10.1039/d2dt02279f
  • 2022 • 477 The Direct Mechanocatalytic Suzuki–Miyaura Reaction of Small Organic Molecules
    Pickhardt, W. and Beaković, C. and Mayer, M. and Wohlgemuth, M. and Kraus, F.J.L. and Etter, M. and Grätz, S. and Borchardt, L.
    Angewandte Chemie - International Edition (2022)
    The molecular Suzuki cross-coupling reaction was conducted mechanochemically, without solvents, ligands, or catalyst powders. Utilizing one catalytically active palladium milling ball, products could be formed in quantitative yield in as little as 30 min. In contrast to previous reports, the adjustment of milling parameters led to the complete elimination of abrasion from the catalyst ball, thus enabling the first reported systematic catalyst analysis. XPS, in situ XRD, and reference experiments provided evidence that the milling ball surface was the location of the catalysis, allowing a mechanism to be proposed. The versatility of the approach was demonstrated by extending the substrate scope to deactivated and even sterically hindered aryl iodides and bromides. © 2022 The Authors. Angewandte Chemie International Edition published by Wiley-VCH GmbH.
    view abstractdoi: 10.1002/anie.202205003
  • 2022 • 476 Anti-Blooming Clocking for Time-Delay Integration CCDs
    Piechaczek, D.S. and Schrey, O. and Ligges, M. and Hosticka, B. and Kokozinski, R.
    Sensors 22 (2022)
    This paper presents an investigation of the responsivity of a time-delay integration (TDI) charge-coupled device that employs anti-blooming clocking and uses a varying number of TDI stages. The influence of charge blooming caused by unused TDI stages in a TDI deployed selection scheme is shown experimentally, and an anti-blooming clocking mechanism is analyzed. The impact of blooming on sensor characteristics, such as the responsivity, the conversion gain, and the signal-to-noise ratio, is investigated. A comparison of the measurements with and without this anti-blooming clocking mechanism is presented and discussed in detail. © 2022 by the authors.
    view abstractdoi: 10.3390/s22197520
  • 2022 • 475 Adaptation of the Chemical Percolation Devolatilization Model for Low Temperature Pyrolysis in a Fluidized Bed Reactor
    Pielsticker, S. and Ontyd, C. and Kreitzberg, T. and Hatzfeld, O. and Schiemann, M. and Scherer, V. and Kneer, R.
    Combustion Science and Technology 194 417-434 (2022)
    In the present study, the CPD model originally developed based on predictions from heated grid (HGR) and entrained flow (EFR) experiments, has been adapted to analyze pyrolysis kinetics in a small-scale fluidized bed reactor. Impacts of particle feed, particle heat up as well as tar cracking reactions in the gas phase are considered. Furthermore, an optimized solver structure allows a time step independent solution and enables the use of implicit methods. A comparison with experimental results is undertaken for pulverized Rhenish lignite fuel particles in the temperature range from 673 to 973 K in N2 atmosphere. The comparison between simulated and experimentally derived volatile release rates reveals a good agreement, indicating that the high temperature derived kinetic parameters from HRG and EFR experiments can be extrapolated to lower temperatures. Nevertheless, discrepancies in the tar to light gas ratio occur with the proposed model implementation. © 2022 Taylor & Francis Group, LLC.
    view abstractdoi: 10.1080/00102202.2019.1682433
  • 2022 • 474 The influence of temperature on the strain-hardening behavior of Fe-22/25/28Mn-3Al-3Si TRIP/TWIP steels
    Pierce, D.T. and Benzing, J.T. and Jiménez, J.A. and Hickel, T. and Bleskov, I. and Keum, J. and Raabe, D. and Wittig, J.E.
    Materialia 22 (2022)
    doi: 10.1016/j.mtla.2022.101425
  • 2022 • 473 Recrystallization in non-conventional microstructures of 316L stainless steel produced via laser powder-bed fusion: effect of particle coarsening kinetics
    Pinto, F.C. and Aota, L.S. and Souza Filho, I.R. and Raabe, D. and Sandim, H.R.Z.
    Journal of Materials Science (2022)
    Abstract: Alloys processed by laser powder-bed fusion show distinct microstructures composed of dislocation cells, dispersed nanoparticles, and columnar grains. Upon post-build annealing, such alloys show sluggish recrystallization kinetics compared to the conventionally processed counterpart. To understand this behavior, AISI 316L stainless steel samples were constructed using the island scan strategy. Rhodonite-like (MnSiO3) nanoparticles and dislocation cells are found within weakly-textured grains in the as-built condition. Upon isothermal annealing at 1150 °C (up to 2880 min), the nucleation of recrystallization occurs along the center of the melt pool, where nuclei sites, high stored elastic energy, and local large misorientation are found in the as-built condition. The low value of the Avrami coefficient (n = 1.16) can be explained based on the non-random distribution of nucleation sites. The local interaction of the recrystallization front with nanoparticles speeds up their coarsening causing the decrease of the Zener-Smith pinning force. This allows the progression of recrystallization in LPBF alloys, although sluggish. These results allow us to understand the progress of recrystallization in LPBF 316L stainless steel, shedding light on the nucleation mechanisms and on the competition between driving and dragging pressures in non-conventional microstructures. They also help to understand the most relevant microstructural aspects applicable for tuning microstructures and designing new LPBF alloys. Graphical abstract: [Figure not available: see fulltext.] © 2022, The Author(s).
    view abstractdoi: 10.1007/s10853-021-06859-1
  • 2022 • 472 Unusual Phase Formation in Reactively Sputter-Deposited La—Co—O Thin-Film Libraries
    Piotrowiak, T.H. and Zehl, R. and Suhr, E. and Banko, L. and Kohnen, B. and Rogalla, D. and Ludwig, Al.
    Advanced Engineering Materials (2022)
    La-based perovskites are versatile materials that are of interest for solid oxide fuel cells and electrocatalytic water splitting. During fabrication of composition spread thin-film libraries of La—Co-based oxide systems, an unusual phase formation phenomenon is observed: instead of the expected continuous composition gradient, single-phase regions with homogeneous composition form (La2O3 or stoichiometric La-perovskite). This phenomenon, which occurs during reactive cosputtering, is independent of the used substrate. However, a dependency on the O2-portion in the process gas and the substrate temperature is observed. It can be described as a self-organized growth, where excess transition metal cannot be incorporated into the lattices of the forming single-phase regions, and therefore, not into the growing film. It is hypothesized that due to the high reactivity of La and the significantly low formation energies of La2O3 and La-perovskites, the reactive sputter deposition of La-based oxide films, which is a physical vapor deposition process, can turn partially—regarding film growth—into a chemical vapor deposition-like process. The described single-phase regions form and lead to a discontinuous composition spread, with preferred growth of the thermodynamically most stable phases. This phenomenon can be leveraged for the exploration of multinary perovskite thin-film libraries, where the B-site atoms of La-perovskites are systematically substituted. © 2022 The Authors. Advanced Engineering Materials published by Wiley-VCH GmbH.
    view abstractdoi: 10.1002/adem.202201050
  • 2022 • 471 Antimicrobial and Antibiofouling Electrically Conducting Laser-Induced Graphene Spacers in Reverse Osmosis Membrane Modules
    Pisharody, L. and Thamaraiselvan, C. and Manderfeld, E. and Singh, S.P. and Rosenhahn, A. and Arnusch, C.J.
    Advanced Materials Interfaces (2022)
    Biofouling is an ongoing challenge for water treatment membrane processes. Reducing biofilm growth on the membrane surface or on the polymeric feed spacer will reduce operation, maintenance, and module replacement costs. Laser-induced graphene (LIG) is a low cost, environmentally friendly, electrically conductive carbon material shown to have antibiofouling properties. Here it has been shown that an electrically conductive LIG-coated polypropylene (PP) feed spacer has both antimicrobial and antifouling effects under a low electrical current, and when implemented into a spiral wound membrane module reduced biofilm growth on both the membrane and the spacer components. The antibacterial property of the LIG spacer is tested using Pseudomonas aeruginosa and the brackish water Rheinheimera sp. as model organisms. Using a voltage of 12 V, P. aeruginosa is completely inactivated in 10 h, while a dynamic accumulation assay employing Rheinheimera sp. showed significant reduction (p < 0.05) in bacterial adhesion compared to an uncoated spacer. The spacer is incorporated into a spiral wound reverse osmosis (RO) membrane module, and reduced biofouling is observed on both the membrane and LIG spacers components using brackish water and 12 V. This study demonstrates the feasibility of electrically conductive feed spacer components in spiral wound RO membrane modules. © 2022 The Authors. Advanced Materials Interfaces published by Wiley-VCH GmbH.
    view abstractdoi: 10.1002/admi.202201443
  • 2022 • 470 Potential of high-feed milling structured dies for material flow control in hot forming
    Platt, T. and Baumann, J. and Biermann, D.
    Production Engineering (2022)
    doi: 10.1007/s11740-022-01165-4
  • 2022 • 469 Couette flow in a rectangular channel in the whole range of the gas rarefaction
    Pleskun, H. and Bode, T. and Brümmer, A.
    Physics of Fluids 34 (2022)
    The mass flow rate of a Couette flow in a long rectangular channel is calculated for constant or linear wall velocities in the whole range of the gas rarefaction and in a wide range of the width-to-height ratio. Analytical solutions for arbitrary width-to-height ratios are given for the hydrodynamic regime, the slip regime, and the free molecular regime. Therefore, both the velocity field and the mass flow rate can be calculated. In the transitional regime, simulations via direct simulation Monte Carlo method are performed. The results are provided as reduced flow rates in tabulated data, which can be used for any constant or linear increasing wall velocity (e.g., bounding walls of working chambers in positive displacement vacuum pumps). © 2022 Author(s).
    view abstractdoi: 10.1063/5.0082940
  • 2022 • 468 Gas-surface interactions of a Couette-Poiseuille flow in a rectangular channel
    Pleskun, H. and Brümmer, A.
    Physics of Fluids 34 (2022)
    doi: 10.1063/5.0099256
  • 2022 • 467 Magnetoelectric coupling in nonsintered bulk BaTiO3 -- xCoFe2O4 multiferroic composites
    Plyushch, A. and Lewin, D. and Sokal, A. and Grigalaitis, R. and Shvartsman, V.V. and Macutkevič, J. and Salamon, S. and Wende, H. and Lapko, K.N. and Kuzhir, P.P. and Lupascu, D.C. and Banys, J.
    Journal of Alloys and Compounds 917 (2022)
    Bulk BaTiO3-xCoFe2O4, x = 0.1 – 0.6 magnetoelectric composites were prepared using the phosphate bonded ceramics approach. XRD analysis proved the purity of both phases. The dielectric properties are governed by a series of composition-dependent Maxwell-Wagner relaxations and conductivity at lower frequencies and a phase transition-related anomaly at higher frequencies. A dielectric constant as high as 616 – 9387i is observed at 500 K for BaTiO3-0.6CoFe2O4. The magnetic hysteresis demonstrates a high Ms/Mr ratio of 0.46, which is related to the around 30 nm size of the CoFe2O4 particles. The measured direct magnetoelectric coupling coefficient of 1.1 mV Oe−1 cm−1 is higher than that of the conventionally sintered ceramics and compatible with that of core-shell structures. © 2022 Elsevier B.V.
    view abstractdoi: 10.1016/j.jallcom.2022.165519
  • 2022 • 466 PHOSPHATE BONDED CoFe2 O4 –BaTiO3 LAYERED STRUCTURES: DIELECTRIC RELAXATIONS AND MAGNETOELECTRIC COUPLING [FOSFATAIS SURIŠTI CoFe2O4 – BaTiO3 SLUOKSNINIAI DARINIAI: DIELEKTRINĖS RELAKSACIJOS IR MAGNETOELEKTRINĖ SĄVEIKA]
    Plyushch, A. and Lewin, D. and Ažubalis, P. and Kalendra, V. and Sokal, A. and Grigalaitis, R. and Shvartsman, V.V. and Salamon, S. and Wende, H. and Selskis, A. and Lapko, K.N. and Lupascu, D.C. and Banys, J.
    Lithuanian Journal of Physics 62 221-228 (2022)
    doi: 10.3952/physics.v62i4.4817
  • 2022 • 465 A single-Pt-atom-on-Ru-nanoparticle electrocatalyst for CO-resilient methanol oxidation
    Poerwoprajitno, A.R. and Gloag, L. and Watt, J. and Cheong, S. and Tan, X. and Lei, H. and Tahini, H.A. and Henson, A. and Subhash, B. and Bedford, N.M. and Miller, B.K. and O’Mara, P.B. and Benedetti, T.M. and Huber, D.L. and Z...
    Nature Catalysis 5 231-237 (2022)
    Single Pt atom catalysts are key targets because a high exposure of Pt substantially enhances electrocatalytic activity. In addition, PtRu alloy nanoparticles are the most active catalysts for the methanol oxidation reaction. To combine the exceptional activity of single Pt atom catalysts with an active Ru support we must overcome the synthetic challenge of forming single Pt atoms on noble metal nanoparticles. Here we demonstrate a process that grows and spreads Pt islands on Ru branched nanoparticles to create single-Pt-atom-on-Ru catalysts. By following the spreading process by in situ TEM, we found that the formation of a stable single atom structure is thermodynamically driven by the formation of strong Pt–Ru bonds and the lowering of the surface energy of the Pt islands. The stability of the single-Pt-atom-on-Ru structure and its resilience to CO poisoning result in a high current density and mass activity for the methanol oxidation reaction over time. [Figure not available: see fulltext.] © 2022, The Author(s), under exclusive licence to Springer Nature Limited.
    view abstractdoi: 10.1038/s41929-022-00756-9
  • 2022 • 464 Characterization of modified lead-free ferroelectric sodium-bismuth titanate ceramics
    Politova, E.D. and Kaleva, G.M. and Mosunov, A.V. and Stefanovich, S.Y. and Sadovskaya, N.V. and Shvartsman, V.V.
    Ferroelectrics 591 91-99 (2022)
    Influence of dopants on structure, microstructure, dielectric and ferroelectric properties of ferroelectric-relaxor (Na0.5Bi0.5)TiO3 ceramics modified by Ba2+ cations and overstoichiometric additives (SiO2 and Na2O) was studied. Changes in structure, microstructure, and dielectric parameters were observed depending on solid solutions compositions. © 2022 Taylor & Francis Group, LLC.
    view abstractdoi: 10.1080/00150193.2022.2044681
  • 2022 • 463 Dynamic growth/etching model for the synthesis of two-dimensional transition metal dichalcogenides via chemical vapour deposition
    Pollmann, E. and Maas, A. and Marnold, D. and Hucht, A. and Neubieser, R.-M. and Stief, M. and Madauß, L. and Schleberger, M.
    2D Materials 9 (2022)
    The preparation of two-dimensional transition metal dichalcogenides on an industrially relevant scale will rely heavily on bottom-up methods such as chemical vapour deposition. In order to obtain sufficiently large quantities of high-quality material, a knowledge-based optimization strategy for the synthesis process must be developed. A major problem that has not yet been considered is the degradation of materials by etching during synthesis due to the high growth temperatures. To address this problem, we introduce a mathematical model that accounts for both growth and, for the first time, etching to describe the synthesis of two-dimensional transition metal dichalcogenides. We consider several experimental observations that lead to a differential equation based on several terms corresponding to different supply mechanisms, describing the time-dependent change in flake size. By solving this equation and fitting two independently obtained experimental data sets, we find that the flake area is the leading term in our model. We show that the differential equation can be solved analytically when only this term is considered, and that this solution provides a general description of complex growth and shrinkage phenomena. Physically, the dominance suggests that the supply of material via the flake itself contributes most to its net growth. This finding also implies a predominant interplay between insertion and release of atoms and their motion in the form of a highly dynamic process within the flake. In contrast to previous assumptions, we show that the flake edges do not play an important role in the actual size change of the two-dimensional transition metal dichalcogenide flakes during chemical vapour deposition. © 2022 The Author(s). Published by IOP Publishing Ltd.
    view abstractdoi: 10.1088/2053-1583/ac5ec5
  • 2022 • 462 An Injection-Lockable InP-DHBT Source Operating at 421 GHz with -2.4 dBm Output Power and 1.7% DC-to-RF Efficiency
    Possberg, A. and Vogelsang, F. and Pohl, N. and Hossain, M. and Yacoub, H. and Johansen, T.K. and Heinrich, W. and Weimann, N.
    IEEE MTT-S International Microwave Symposium Digest 2022-June 336-339 (2022)
    In this work, an injection-lockable push-push oscillator operating at 421 GHz is presented. The circuit is based on a 0.5 um transferred substrate InP DHBT MMIC process. A peak output power of -2.4 dBm is measured at 34.6 mW DC-power consumption, resulting in 1.7% DC-to-RF conversion efficiency. The oscillator can be injection-locked through a dedicated locking port which, along with the compact core measuring 0.53 × 0.49 mm2, makes this design suitable for efficient injection-locked oscillator arrays comprising a beam steering function by phase tuning. © 2022 IEEE.
    view abstractdoi: 10.1109/IMS37962.2022.9865468
  • 2022 • 461 Investigations Into Chemically Stabilized Four-Letter DNA for DNA-Encoded Chemistry
    Potowski, M. and Kunig, V.B.K. and Eberlein, L. and Škopić, M.K. and Vakalopoulos, A. and Kast, S.M. and Brunschweiger, A.
    Frontiers in Chemistry 10 (2022)
    DNA-encoded libraries are a prime technology for target-based small molecule screening. Native DNA used as genetic compound barcode is chemically vulnerable under many reaction conditions. DNA barcodes that are composed of pyrimidine nucleobases, 7-deazaadenine, and 7-deaza-8-azaguanine have been investigated for their suitability for encoded chemistry both experimentally and computationally. These four-letter barcodes were readily ligated by T4 ligation, amplifiable by Taq polymerase, and the resultant amplicons were correctly sequenced. Chemical stability profiling showed a superior chemical stability compared to native DNA, though higher susceptibility to depurination than a three-letter code based on pyrimidine DNA and 7-deazaadenine. Copyright © 2022 Potowski, Kunig, Eberlein, Škopić, Vakalopoulos, Kast and Brunschweiger.
    view abstractdoi: 10.3389/fchem.2022.894563
  • 2022 • 460 Experimental and simulative analysis of an adapted methodology for decoupling tool wear in end milling
    Potthoff, N. and Agarwal, A. and Wöste, F. and Liß, J. and Mears, L. and Wiederkehr, P.
    Manufacturing Letters 33 380-387 (2022)
    The machining of nickel-based superalloys such as Inconel 718 still poses a great challenge. The high strength and temperature resistance of these materials lead to poor machinability, resulting in high process forces and extensive tool wear. However, this wear is stochastic when reaching a certain point and is difficult to predict. To generate consistent wear conditions, the tool wear can be decoupled from the milling process by creating artificial wear using grinding. In this paper, a multi-axis approach for decoupling tool wear is presented and analyzed. Therefore, scanning electron microscope images of different wear states – worn and artificially worn – are analyzed. In addition, the occurring process forces of naturally and contrived worn inserts are compared in orthogonal cutting experiments as an analogy setup. Finally, a finite element analysis using a novel methodology for segmenting relevant cutting edge sections using digital microscope images provides qualitative insights on the influence of different wear conditions. © 2022
    view abstractdoi: 10.1016/j.mfglet.2022.07.050
  • 2022 • 459 Improvement of proton conductivity of magnetically aligned phosphotungstic acid-decorated cobalt oxide embedded Nafion membrane
    Pourzare, K. and Mansourpanah, Y. and Farhadi, S. and Sadrabadi, M.M.H. and Ulbricht, M.
    Energy 239 (2022)
    The fabrication of proton exchange membranes with a short conduction pathway in the direction of membrane thickness is desirable for fuel cell applications. In this study, a new nanohybrid additive (Co3O4-NH2/H3PW12O40; CAW) is synthesized, by anchoring phosphotungstic acid (H3PW12O40; HPW) on aminopropylsiloxane-functionalized cobalt oxide, and then it is incorporated into the Nafion (NF) matrix to prepare nanocomposite membranes by film casting from CAW dispersions in NF solutions. To obtain short-pathway proton-conducting channels, through the nanocomposite membranes drying process, a magnetic field is employed to align the nanohybrid particles in transversal (thickness) direction of the NF matrix. Furthermore, the alignment of nanohybrids is observed directly by scanning electron microscopy, and estimated indirectly by proton conductivity and methanol permeability values. It is found that alignment of nanohybrids in the NF matrix elevates the conductivity of proton as well as the permeability of methanol. The aligned NF/CAW nanocomposite membrane with 1 wt% of CAW reveals the highest proton conductivity of 211 mS cm−1 at 90 °C and 95% relative humidity, which is 39% higher than that of pure NF (152 mS cm−1). Interestingly, through the orientation of CAW, 76% improvement in the selectivity of the membranes is observed. © 2021 Elsevier Ltd
    view abstractdoi: 10.1016/j.energy.2021.121940
  • 2022 • 458 Identification of texture characteristics for improved creep behavior of a L-PBF fabricated IN738 alloy through micromechanical simulations
    Prasad, M.R.G. and Biswas, A. and Vajragupta, N. and Hartmaier, A.
    Modelling and Simulation in Materials Science and Engineering 30 (2022)
    doi: 10.1088/1361-651X/ac6e7a
  • 2022 • 457 NdFeB Magnets with Well-Pronounced Anisotropic Magnetic Properties Made by Electric Current-Assisted Sintering
    Prasad Mishra, T. and Leich, L. and Krengel, M. and Weber, S. and Röttger, A. and Bram, M.
    Advanced Engineering Materials (2022)
    Electric current-assisted sintering (ECAS) technologies are highly promising for processing of NdFeB magnets. Due to the combination of direct Joule heating and application of external load, even powders, whose particle size distribution and morphology are not optimum for conventional powder processing like melt-spun powders or magnet scrap, can be easily sintered to high densities. A systematic study is done to demonstrate the potential of field-assisted sintering technique/spark plasma sintering (FAST/SPS) and flash spark plasma sintering (flash SPS) for sintering of NdFeB powders. Melt-spun, commercial NdFeB powder (Magnequench MQU-F) is used as starting material. Its platelet-like shape makes this powder extremely difficult to sinter by conventional methods. This study clearly reveals that especially in the case of flash SPS application of external pressure in combination with short cycle times enables to achieve well-pronounced anisotropic magnetic properties without the need of subsequent upset forging. Optimized flash SPS parameters are applied to NdFeB magnet scrap with broad particle size distribution, demonstrating the general potential of ECAS technologies for recycling of waste magnet materials. Finally, the results are benchmarked with respect to established NdFeB processing technologies and electrodischarge sintering (EDS), another promising ECAS technology with very short cycling time. © 2022 The Authors. Advanced Engineering Materials published by Wiley-VCH GmbH.
    view abstractdoi: 10.1002/adem.202201027
  • 2022 • 456 Liquid-phase temperature in the SpraySyn flame measured by two-color laser-induced fluorescence thermometry and simulated by LES
    Prenting, M.M. and Baik, S.-J. and Dreier, T. and Endres, T. and Kempf, A. and Schulz, C.
    Proceedings of the Combustion Institute (2022)
    doi: 10.1016/j.proci.2022.07.131
  • 2022 • 455 Biotin-Functionalized Block Catiomers as an Active Targeting Approach in Gene Delivery
    Pretzer, I. and Bushiri, D. and Weberskirch, R.
    Macromolecular Materials and Engineering (2022)
    doi: 10.1002/mame.202200627
  • 2022 • 454 FR4 Test Board for Measurements on InP Resonant Tunneling Diode THz Oscillators Integrated via Flip Chip Bonding Technology
    Preuss, C. and Mutlu, E. and Kress, R. and Clochiatti, S. and Lu, P. and Stohr, A. and Prost, W. and Weimann, N.
    2022 15th UK-Europe-China Workshop on Millimetre-Waves and Terahertz Technologies, UCMMT 2022 (2022)
    doi: 10.1109/UCMMT56896.2022.9994786
  • 2022 • 453 Endoplasmic reticulum-stress and unfolded protein response-activation in immune-mediated necrotizing myopathy
    Preusse, C. and Marteau, T. and Fischer, N. and Hentschel, A. and Sickmann, A. and Lang, S. and Schneider, U. and Schara-Schmidt, U. and Meyer, N. and Ruck, T. and Dengler, N.F. and Prudlo, J. and Dudesek, A. and Görl, N. and All...
    Brain Pathology 32 (2022)
    Patients suffering from immune-mediated necrotizing myopathies (IMNM) harbor, the pathognomonic myositis-specific auto-antibodies anti-SRP54 or -HMGCR, while about one third of them do not. Activation of chaperone-assisted autophagy was described as being part of the molecular etiology of IMNM. Endoplasmic reticulum (ER)/sarcoplasmic reticulum (SR)-stress accompanied by activation of the unfolded protein response (UPR) often precedes activation of the protein clearance machinery and represents a cellular defense mechanism toward restoration of proteostasis. Here, we show that ER/SR-stress may be part of the molecular etiology of IMNM. To address this assumption, ER/SR-stress related key players covering the three known branches (PERK-mediated, IRE1-mediated, and ATF6-mediated) were investigated on both, the transcript and the protein levels utilizing 39 muscle biopsy specimens derived from IMNM-patients. Our results demonstrate an activation of all three UPR-branches in IMNM, which most likely precedes the activation of the protein clearance machinery. In detail, we identified increased phosphorylation of PERK and eIF2a along with increased expression and protein abundance of ATF4, all well-documented characteristics for the activation of the UPR. Further, we identified increased general XBP1-level, and elevated XBP1 protein levels. Additionally, our transcript studies revealed an increased ATF6-expression, which was confirmed by immunostaining studies indicating a myonuclear translocation of the cleaved ATF6-form toward the forced transcription of UPR-related chaperones. In accordance with that, our data demonstrate an increase of downstream factors including ER/SR co-chaperones and chaperones (e.g., SIL1) indicating an UPR-activation on a broader level with no significant differences between seropositive and seronegative patients. Taken together, one might assume that UPR-activation within muscle fibers might not only serve to restore protein homeostasis, but also enhance sarcolemmal presentation of proteins crucial for attracting immune cells. Since modulation of ER-stress and UPR via application of chemical chaperones became a promising therapeutic treatment approach, our findings might represent the starting point for new interventional concepts. © 2022 The Authors. Brain Pathology published by John Wiley & Sons Ltd on behalf of International Society of Neuropathology.
    view abstractdoi: 10.1111/bpa.13084
  • 2022 • 452 Skeletal muscle provides the immunological micro-milieu for specific plasma cells in anti-synthetase syndrome-associated myositis
    Preuße, C. and Paesler, B. and Nelke, C. and Cengiz, D. and Müntefering, T. and Roos, A. and Amelin, D. and Allenbach, Y. and Uruha, A. and Dittmayer, C. and Hentschel, A. and Pawlitzki, M. and Hoffmann, S. and Timm, S. and Loui...
    Acta Neuropathologica 144 353-372 (2022)
    Anti-synthetase syndrome (ASyS)-associated myositis is a major subgroup of the idiopathic inflammatory myopathies (IIM) and is characterized by disease chronicity with musculoskeletal, dermatological and pulmonary manifestations. One of eight autoantibodies against the aminoacyl-transferase RNA synthetases (ARS) is detectable in the serum of affected patients. However, disease-specific therapeutic approaches have not yet been established. To obtain a deeper understanding of the underlying pathogenesis and to identify putative therapeutic targets, we comparatively investigated the most common forms of ASyS associated with anti-PL-7, anti-PL-12 and anti-Jo-1. Our cohort consisted of 80 ASyS patients as well as healthy controls (n = 40), diseased controls (n = 40) and non-diseased controls (n = 20). We detected a reduced extent of necrosis and regeneration in muscle biopsies from PL-12+ patients compared to Jo-1+ patients, while PL-7+ patients had higher capillary dropout in biopsies of skeletal muscle. Aside from these subtle alterations, no significant differences between ASyS subgroups were observed. Interestingly, a tissue-specific subpopulation of CD138+ plasma cells and CXCL12+/CXCL13+CD20+ B cells common to ASyS myositis were identified. These cells were localized in the endomysium associated with alkaline phosphatase+ activated mesenchymal fibroblasts and CD68+MHC-II+CD169+ macrophages. An MHC-I+ and MHC-II+ MxA negative type II interferon-driven milieu of myofiber activation, topographically restricted to the perifascicular area and the adjacent perimysium, as well as perimysial clusters of T follicular helper cells defined an extra-medullary immunological niche for plasma cells and activated B cells. Consistent with this, proteomic analyses of muscle tissues from ASyS patients demonstrated alterations in antigen processing and presentation. In-depth immunological analyses of peripheral blood supported a B-cell/plasma-cell-driven pathology with a shift towards immature B cells, an increase of B-cell-related cytokines and chemokines, and activation of the complement system. We hypothesize that a B-cell-driven pathology with the presence and persistence of a specific subtype of plasma cells in the skeletal muscle is crucially involved in the self-perpetuating chronicity of ASyS myositis. This work provides the conceptual framework for the application of plasma-cell-targeting therapies in ASyS myositis. © 2022, The Author(s).
    view abstractdoi: 10.1007/s00401-022-02438-z
  • 2022 • 451 Incorporation of Cu/Ni in Ordered Mesoporous Co-Based Spinels to Facilitate Oxygen Evolution and Reduction Reactions in Alkaline Media and Aprotic Li−O2 Batteries
    Priamushko, T. and Budiyanto, E. and Eshraghi, N. and Weidenthaler, C. and Kahr, J. and Jahn, M. and Tüysüz, H. and Kleitz, F.
    ChemSusChem 15 (2022)
    Ordered mesoporous CuNiCo oxides were prepared via nanocasting with varied Cu/Ni ratio to establish its impact on the electrochemical performance of the catalysts. Physicochemical properties were determined along with the electrocatalytic activities toward oxygen evolution/reduction reactions (OER/ORR). Combining Cu, Ni, and Co allowed creating active and stable bifunctional electrocatalysts. CuNiCo oxide (Cu/Ni≈1 : 4) exhibited the highest current density of 411 mA cm−2 at 1.7 V vs. reversible hydrogen electrode (RHE) and required the lowest overpotential of 312 mV to reach 10 mA cm−2 in 1 m KOH after 200 cyclic voltammograms. OER measurements were also conducted in the purified 1 m KOH, where CuNiCo oxide (Cu/Ni≈1 : 4) also outperformed NiCo oxide and showed excellent chemical and catalytic stability. For ORR, Cu/Ni incorporation provided higher current density, better kinetics, and facilitated the 4e− pathway of the oxygen reduction reaction. The tests in Li−O2 cells highlighted that CuNiCo oxide can effectively promote ORR and OER at a lower overpotential. © 2021 The Authors. ChemSusChem published by Wiley-VCH GmbH
    view abstractdoi: 10.1002/cssc.202102404
  • 2022 • 450 A Study of Reliable Short-Range Communication Systems for THz Frequencies
    Prokscha, A. and Sheikh, F. and Lessy, D. and Kaiser, T.
    2022 IEEE International Symposium on Antennas and Propagation and USNC-URSI Radio Science Meeting, AP-S/URSI 2022 - Proceedings 768-769 (2022)
    doi: 10.1109/AP-S/USNC-URSI47032.2022.9886636
  • 2022 • 449 Portable Device-Centric Human Postures for Modeling Reliable THz Channels
    Prokscha, A. and Sheikh, F. and Lessy, D. and Kaiser, T.
    2022 5th International Workshop on Mobile Terahertz Systems, IWMTS 2022 (2022)
    doi: 10.1109/IWMTS54901.2022.9832444
  • 2022 • 448 Triple Barrier Resonant Tunneling Diodes for THz emission and sensing
    Prost, W. and Arzi, K. and Clochiatti, S. and Mutlu, E. and Suzuki, S. and Asad, M. and Weimann, N.
    Proceedings of SPIE - The International Society for Optical Engineering 12230 (2022)
    doi: 10.1117/12.2632368
  • 2022 • 447 Potential of novel porous materials for capture of toluene traces in air under humid conditions
    Pujol, Q. and Weber, G. and Bellat, J.-P. and Grätz, S. and Krusenbaum, A. and Borchardt, L. and Bezverkhyy, I.
    Microporous and Mesoporous Materials 344 (2022)
    doi: 10.1016/j.micromeso.2022.112204
  • 2022 • 446 Electron Spin Coherence in CdSe Nanocrystals in a Glass Matrix
    Qiang, G. and Zhukov, E.A. and Evers, E. and Yakovlev, D.R. and Golovatenko, A.A. and Rodina, A.V. and Onushchenko, A.A. and Bayer, M.
    ACS Nano 16 18838-18848 (2022)
    doi: 10.1021/acsnano.2c07645
  • 2022 • 445 Heat flux in latent thermal energy storage systems: the influence of fins, thermal conductivity and driving temperature difference
    Quenel, J. and Atakan, B.
    Heat and Mass Transfer/Waerme- und Stoffuebertragung 58 2085-2096 (2022)
    doi: 10.1007/s00231-022-03220-3
  • 2022 • 444 Making sustainable aluminum by recycling scrap: The science of “dirty” alloys
    Raabe, D. and Ponge, D. and Uggowitzer, P.J. and Roscher, M. and Paolantonio, M. and Liu, C. and Antrekowitsch, H. and Kozeschnik, E. and Seidmann, D. and Gault, B. and De Geuser, F. and Deschamps, A. and Hutchinson, C. and Liu, C...
    Progress in Materials Science 128 (2022)
    There are several facets of aluminum when it comes to sustainability. While it helps to save fuel due to its low density, producing it from ores is very energy-intensive. Recycling it shifts the balance towards higher sustainability, because the energy needed to melt aluminum from scrap is only about 5% of that consumed in ore reduction. The amount of aluminum available for recycling is estimated to double by 2050. This offers an opportunity to bring the metallurgical sector closer to a circular economy. A challenge is that large amounts of scrap are post-consumer scrap, containing high levels of elemental contamination. This has to be taken into account in more sustainable alloy design strategies. A “green aluminum” trend has already triggered a new trading platform for low-carbon aluminum at the London Metal Exchange (2020). The trend may lead to limits on the use of less-sustainable materials in future products. The shift from primary synthesis (ore reduction) to secondary synthesis (scrap melting) requires to gain better understanding of how multiple scrap-related contaminant elements act on aluminum alloys and how future alloys can be designed upfront to become scrap-compatible and composition-tolerant. The paper therefore discusses the influence of scrap-related impurities on the thermodynamics and kinetics of precipitation reactions and their mechanical and electrochemical effects; impurity effects on precipitation-free zones around grain boundaries; their effects on casting microstructures; and the possibilities presented by adjusting processing parameters and the associated mechanical, functional and chemical properties. The objective is to foster the design and production of aluminum alloys with the highest possible scrap fractions, using even low-quality scrap and scrap types which match only a few target alloys when recycled. © 2022 The Authors
    view abstractdoi: 10.1016/j.pmatsci.2022.100947
  • 2022 • 443 Coupling of electronic and structural degrees of freedom in vanadate superlattices
    Radhakrishnan, P. and Geisler, B. and Fürsich, K. and Putzky, D. and Wang, Y. and Christiani, G. and Logvenov, G. and Wochner, P. and Van Aken, P.A. and Pentcheva, R. and Benckiser, E.
    Physical Review B 105 (2022)
    Heterostructuring provides different ways to manipulate the orbital degrees of freedom and to tailor orbital occupations in transition-metal oxides. However, the reliable prediction of these modifications remains a challenge. Here we present a detailed investigation of the relationship between the crystal and electronic structure in YVO3-LaAlO3 superlattices by combining ab initio theory, scanning transmission electron microscopy, and x-ray diffraction. Density functional theory simulations including an on-site Coulomb repulsion term accurately predict the crystal structure and, in conjunction with x-ray diffraction, provide an explanation for the lifting of degeneracy of the vanadium dxz and dyz orbitals that was recently observed in this system. In addition, we unravel the combined effects of electronic confinement and octahedral connectivity by disentangling their impact from that of epitaxial strain. Our results demonstrate that the specific orientation of the substrate and the thickness of the YVO3 slabs in the multilayer can be utilized to reliably engineer orbital polarization. © 2022 authors. Published by the American Physical Society.
    view abstractdoi: 10.1103/PhysRevB.105.165117
  • 2022 • 442 Computational model predicts protein binding sites of a luminescent ligand equipped with guanidiniocarbonyl-pyrrole groups
    Rafieiolhosseini, N. and Killa, M. and Neumann, T. and Tötsch, N. and Grad, J.-N. and Höing, A. and Dirksmeyer, T. and Niemeyer, J. and Ottmann, C. and Knauer, S.K. and Giese, M. and Voskuhl, J. and Hoffmann, D.
    Beilstein Journal of Organic Chemistry 18 1322-1331 (2022)
    doi: 10.3762/bjoc.18.137
  • 2022 • 441 Extending the potentials of draw-forging
    Rakshit, T. and Gebhard, J. and Napierala, O. and Kolpak, F. and Schulze, A. and Hering, O. and Tekkaya, A.E.
    International Journal of Material Forming 15 (2022)
    Composite components combine the benefits of different materials, leading to improved product properties, enhanced resource- and energy efficiency and widening the product spectrum. Draw-forging is the unique combination of deep-drawing and cold forging, where a core material is encapsulated within a thin sheet metal blank. Previously, the basic draw-forging process only allowed covering of the shaft tip, and the covered length was limited by the maximum drawing ratio of the sheet. In this work, the different failure types, including tearing of the sheet, asymmetric encapsulation, and the development of a gap in the transition zone were investigated numerically and experimentally and the axial encapsulation length is increased significantly. The usage of anisotropic sheet material leads to a form fit and enhances the bond strength in draw-forged hybrid components. An alternative process route in which a pierced sheet is utilized to partially cover a specific section of a shaft was also developed. The process route was stabilized with a novel contoured counter holder to ensure high repeatability. © 2022, The Author(s).
    view abstractdoi: 10.1007/s12289-022-01662-y
  • 2022 • 440 Introducing Stacking Faults into Three-Dimensional Branched Nickel Nanoparticles for Improved Catalytic Activity
    Ramadhan, Z.R. and Poerwoprajitno, A.R. and Cheong, S. and Webster, R.F. and Kumar, P.V. and Cychy, S. and Gloag, L. and Benedetti, T.M. and Marjo, C.E. and Muhler, M. and Wang, D.-W. and Gooding, J.J. and Schuhmann, W. and Tilley, R.D.
    Journal of the American Chemical Society 144 11094-11098 (2022)
    Creating high surface area nanocatalysts that contain stacking faults is a promising strategy to improve catalytic activity. Stacking faults can tune the reactivity of the active sites, leading to improved catalytic performance. The formation of branched metal nanoparticles with control of the stacking fault density is synthetically challenging. In this work, we demonstrate that varying the branch width by altering the size of the seed that the branch grows off is an effective method to precisely tune the stacking fault density in branched Ni nanoparticles. A high density of stacking faults across the Ni branches was found to lower the energy barrier for Ni2+/Ni3+oxidation and result in enhanced activity for electrocatalytic oxidation of 5-hydroxylmethylfurfural. These results show the ability to synthetically control the stacking fault density in branched nanoparticles as a basis for enhanced catalytic activity. © 2022 American Chemical Society. All rights reserved.
    view abstractdoi: 10.1021/jacs.2c04911
  • 2022 • 439 Effects of thermal, elastic, and surface properties on the stability of SiC polytypes
    Ramakers, S. and Marusczyk, A. and Amsler, M. and Eckl, T. and Mrovec, M. and Hammerschmidt, T. and Drautz, R.
    Physical Review B 106 (2022)
    doi: 10.1103/PhysRevB.106.075201
  • 2022 • 438 Electrophoretic Deposition of Platinum Nanoparticles using Ethanol-Water Mixtures Significantly Reduces Neural Electrode Impedance
    Ramesh, V. and Giera, B. and Karnes, J.J. and Stratmann, N. and Schaufler, V. and Li, Y. and Rehbock, C. and Barcikowski, S.
    Journal of the Electrochemical Society 169 (2022)
    Platinum electrodes are critical components in many biomedical devices, an important example being implantable neural stimulation or recording electrodes. However, upon implantation, scar tissue forms around the electrode surface, causing unwanted deterioration of the electrical contact. We demonstrate that sub-monolayer coatings of platinum nanoparticles (PtNPs) applied to 3D neural electrodes by electrophoretic deposition (EPD) can enhance the electrode?s active surface area and significantly lower its impedance. In this work we use ethanol-water mixtures as the EPD solvent, in contrast to our previous studies carried out in water. We show that EPD coating in 30 vol.% ethanol improves the device?s electrochemical performance. Computational mesoscale multiparticle simulations were for the first time applied to PtNP-on-Pt EPD, revealing correlations between ethanol concentration, electrochemical properties, and coating homogeneity. Thereto, this optimum ethanol concentration (30 vol.%) balances two opposing trends: (i) the addition of ethanol reduces water splitting and gas bubble formation, which benefits surface coverage, and (ii) increased viscosity and reduced permittivity occur at high ethanol concentrations, which impair the coating quality and favoring clustering. A seven-fold increase in active surface area and significantly reduced in vitro impedance of the nano-modified neural stimulation electrode surfaces highlight the influence of ethanol-water mixtures in PtNP EPD. © 2022 The Electrochemical Society ("ECS"). Published on behalf of ECS by IOP Publishing Limited.
    view abstractdoi: 10.1149/1945-7111/ac51f8
  • 2022 • 437 Mechanical Stability of Nano-Coatings on Clinically Applicable Electrodes, Generated by Electrophoretic Deposition
    Ramesh, V. and Stratmann, N. and Schaufler, V. and Angelov, S.D. and Nordhorn, I.D. and Heissler, H.E. and Martínez-Hincapié, R. and Čolić, V. and Rehbock, C. and Schwabe, K. and Karst, U. and Krauss, J.K. and Barcikowski, S.
    Advanced Healthcare Materials (2022)
    doi: 10.1002/adhm.202102637
  • 2022 • 436 A Data-driven Multi-fidelity Physics-informed Learning Framework for Smart Manufacturing: A Composites Processing Case Study
    Ramezankhani, M. and Nazemi, A. and Narayan, A. and Voggenreiter, H. and Harandi, M. and Seethaler, R. and Milani, A.S.
    Proceedings - 2022 IEEE 5th International Conference on Industrial Cyber-Physical Systems, ICPS 2022 (2022)
    doi: 10.1109/ICPS51978.2022.9816983
  • 2022 • 435 Trimethylamine Probes Isolated Silicon Dangling Bonds and Surface Hydroxyls of (H,OH)-Si(001)
    Ramírez, L.P. and Fornefeld, N. and Bournel, F. and Kubsky, S. and Magnano, E. and Bondino, F. and Köhler, U. and Carniato, S. and Gallet, J.-J. and Rochet, F.
    Journal of Physical Chemistry C 126 2548-2560 (2022)
    To better understand why amines catalyze the reactivity of SiOH with silanes, we examined the adsorption of trimethylamine under a low pressure (10-9-10-8 mbar) and a low temperature (105-160 K) on water-terminated (H,OH)-Si(001), which is both a model surface for adsorption studies and a promising starting substrate for atomic layer deposition. Trimethylamine bonding configurations were determined by combining real-time synchrotron radiation X-ray photoelectron spectroscopy (XPS) and high-resolution electron energy loss spectroscopy (HREELS) with density functional theory (DFT) calculations of core-level ionization energies and vibrational spectra. Both spectroscopies showed that the majority of species are trimethylamine molecules making acceptor H bonds with surface hydroxyls. Moreover, HREELS indicated that the hydrogen-bonding modes (single and double hydrogen acceptor bonds) depend on temperature and/or coverage, which may in turn affect the weakening of the O-H bond, and hence the catalytic effects of trimethylamine. XPS also clearly detected a minority species, trimethylamine, datively bonded to the isolated silicon dangling bonds (a few 1/100th of a monolayer). This species is prone to breaking, and a detailed analysis of the reaction products was made. The reactivity of the electrically active isolated silicon dangling bonds with the amine may impact the Fermi-level position in the gap. © 2022 American Chemical Society
    view abstractdoi: 10.1021/acs.jpcc.1c09776
  • 2022 • 434 Nanoscale subsurface dynamics of solids upon high-intensity femtosecond laser irradiation observed by grazing-incidence x-ray scattering
    Randolph, L. and Banjafar, M. and Preston, T.R. and Yabuuchi, T. and Makita, M. and Dover, N.P. and Rödel, C. and Göde, S. and Inubushi, Y. and Jakob, G. and Kaa, J. and Kon, A. and Koga, J.K. and Ksenzov, D. and Matsuoka, T. an...
    Physical Review Research 4 (2022)
    Observing ultrafast laser-induced structural changes in nanoscale systems is essential for understanding the dynamics of intense light-matter interactions. For laser intensities on the order of 1014W/cm2, highly collisional plasmas are generated at and below the surface. Subsequent transport processes such as heat conduction, electron-ion thermalization, surface ablation, and resolidification occur at picosecond and nanosecond timescales. Imaging methods, e.g., using x-ray free-electron lasers (XFEL), were hitherto unable to measure the depth-resolved subsurface dynamics of laser-solid interactions with appropriate temporal and spatial resolution. Here we demonstrate picosecond grazing-incidence small-angle x-ray scattering (GISAXS) from laser-produced plasmas using XFEL pulses. Using multilayer (ML) samples, both the surface ablation and subsurface density dynamics are measured with nanometer depth resolution. Our experimental data challenges the state-of-the-art modeling of matter under extreme conditions and opens new perspectives for laser material processing and high-energy density science. © 2022 authors. Published by the American Physical Society.
    view abstractdoi: 10.1103/PhysRevResearch.4.033038
  • 2022 • 433 Machine learning–enabled high-entropy alloy discovery
    Rao, Z. and Tung, P.-Y. and Xie, R. and Wei, Y. and Zhang, H. and Ferrari, A. and Klaver, T.P.C. and Körmann, F. and Sukumar, P.T. and da Silva, A.K. and Chen, Y. and Li, Z. and Ponge, D. and Neugebauer, J. and Gutfleisch, O. and...
    Science 378 (2022)
    High-entropy alloys are solid solutions of multiple principal elements that are capable of reaching composition and property regimes inaccessible for dilute materials. Discovering those with valuable properties, however, too often relies on serendipity, because thermodynamic alloy design rules alone often fail in high-dimensional composition spaces. We propose an active learning strategy to accelerate the design of high-entropy Invar alloys in a practically infinite compositional space based on very sparse data. Our approach works as a closed-loop, integrating machine learning with density-functional theory, thermodynamic calculations, and experiments. After processing and characterizing 17 new alloys out of millions of possible compositions, we identified two high-entropy Invar alloys with extremely low thermal expansion coefficients around 2 × 10−6 per degree kelvin at 300 kelvin. We believe this to be a suitable pathway for the fast and automated discovery of high-entropy alloys with optimal thermal, magnetic, and electrical properties. Copyright © 2022 The Authors, some rights reserved.
    view abstractdoi: 10.1126/science.abo4940
  • 2022 • 432 Interpretation of Mott-Schottky plots of photoanodes for water splitting
    Ravishankar, S. and Bisquert, J. and Kirchartz, T.
    Chemical Science 13 4828-4837 (2022)
    A large body of literature reports that both bismuth vanadate and haematite photoanodes are semiconductors with an extremely high doping density between 1018 and 1021 cm−3. Such values are obtained from Mott-Schottky plots by assuming that the measured capacitance is dominated by the capacitance of the depletion layer formed by the doping density within the photoanode. In this work, we show that such an assumption is erroneous in many cases because the injection of electrons from the collecting contact creates a ubiquitous capacitance step that is very difficult to distinguish from that of the depletion layer. Based on this reasoning, we derive an analytical resolution limit that is independent of the assumed active area and surface roughness of the photoanode, below which doping densities cannot be measured in a capacitance measurement. We find that the reported doping densities in the literature lie very close to this value and therefore conclude that there is no credible evidence from capacitance measurements that confirms that bismuth vanadate and haematite photoanodes contain high doping densities. © 2022 The Royal Society of Chemistry
    view abstractdoi: 10.1039/d1sc06401k
  • 2022 • 431 Statistical analysis of breaking scaling relation in the oxygen evolution reaction
    Razzaq, S. and Exner, K.S.
    Electrochimica Acta 412 (2022)
    The application of proton exchange membrane electrolyzers in practice to produce gaseous hydrogen as energy vector is majorly hampered by the sluggish oxygen evolution reaction (OER) at the anode. On the atomic scale, a scaling relation between the OH and OOH intermediates has been recognized as main limitation for the development of highly active OER catalysts. Breaking scaling relation is considered as a universal remedy to obtain OER materials with enhanced electrocatalytic activity. While it is a well-accepted paradigm that the optimum OER catalyst reveals a symmetric thermodynamic free-energy landscape, recently, it was suggested that the thermodynamic ideal may correspond to a free-energy landscape with asymmetric shape, allowing thermoneutral stabilization of the key intermediate at the target overpotential. In the present manuscript, we analyze breaking scaling relation in the OER to the symmetric and asymmetric thermodynamic free-energy landscapes by statistical methods at different applied overpotentials. Our analysis reveals that breaking scaling relation to the asymmetric rather than to the symmetric picture is statistically more significant as soon as an overpotential is applied, calling for a change in mindset when thermodynamic considerations are used for catalyst optimization. © 2022
    view abstractdoi: 10.1016/j.electacta.2022.140125
  • 2022 • 430 Method to Determine the Bifunctional Index for the Oxygen Electrocatalysis from Theory
    Razzaq, S. and Exner, K.S.
    ChemElectroChem 9 (2022)
    Metal-air batteries are encountered as a promising solution for energy storage due to their high energy density, cost effectiveness, and environmental benefits. Yet, the application of metal-air batteries in practice is still not mature, which is also related to the bifunctional oxygen electrocatalysis at the cathode, comprising the oxygen reduction (ORR) and oxygen evolution (OER) reactions during discharge and charge of the battery, respectively. Experimentally, the performance of electrocatalysts in the OER and ORR is described by bifunctional index (BI), but, so far, there is no direct approach to capture the BI on the atomic scale. Herein, we present a method to ascertain the BI from ab initio theory, thereby combining a data-driven methodology with thermodynamic considerations and microkinetic modeling as a function of the applied overpotential. Our approach allows deriving the BI from simple adsorption free energies, which are easily accessible to electronic structure theory in the density functional theory (DFT) approximation. We outline how our methodology may steer the design of efficient bifunctional catalysts on the atomic scale. © 2022 The Authors. ChemElectroChem published by Wiley-VCH GmbH
    view abstractdoi: 10.1002/celc.202101603
  • 2022 • 429 Advances and challenges in photosynthetic hydrogen production
    Redding, K.E. and Appel, J. and Boehm, M. and Schuhmann, W. and Nowaczyk, M.M. and Yacoby, I. and Gutekunst, K.
    Trends in Biotechnology 40 1313-1325 (2022)
    The vision to replace coal with hydrogen goes back to Jules Verne in 1874. However, sustainable hydrogen production remains challenging. The most elegant approach is to utilize photosynthesis for water splitting and to subsequently save solar energy as hydrogen. Cyanobacteria and green algae are unicellular photosynthetic organisms that contain hydrogenases and thereby possess the enzymatic equipment for photosynthetic hydrogen production. These features of cyanobacteria and algae have inspired artificial and semi-artificial in vitro techniques, that connect photoexcited materials or enzymes with hydrogenases or mimics of these for hydrogen production. These in vitro methods have on their part been models for the fusion of cyanobacterial and algal hydrogenases to photosynthetic photosystem I (PSI) in vivo, which recently succeeded as proofs of principle. © 2022 The Author(s)
    view abstractdoi: 10.1016/j.tibtech.2022.04.007
  • 2022 • 428 A comparative study of finite element schemes for micromagnetic mechanically coupled simulations
    Reichel, M. and Xu, B.-X. and Schröder, J.
    Journal of Applied Physics 132 (2022)
    doi: 10.1063/5.0105613
  • 2022 • 427 High-order nonlinear terahertz probing of the two-band superconductor MgB2: Third- and fifth-order harmonic generation
    Reinhoffer, C. and Pilch, P. and Reinold, A. and Derendorf, P. and Kovalev, S. and Deinert, J.-C. and Ilyakov, I. and Ponomaryov, A. and Chen, M. and Xu, T.-Q. and Wang, Y. and Gan, Z.-Z. and Wu, D.-S. and Luo, J.-L. and Germanski...
    Physical Review B 106 (2022)
    doi: 10.1103/PhysRevB.106.214514
  • 2022 • 426 Extrusion process simulation and layer shape prediction during 3D-concrete-printing using the Particle Finite Element Method
    Reinold, J. and Nerella, V.N. and Mechtcherine, V. and Meschke, G.
    Automation in Construction 136 (2022)
    Product quality and processing of additively manufactured concrete components strongly depend on the flow processes during material extrusion. To control layer deformations and enable purposeful design, numerical analyses with varying process and material parameters were performed to obtain a deeper understanding of flow processes and forces developing in the vicinity of the nozzle using the Lagrangian-based Particle Finite Element Method in association with a Bingham constitutive model. This model was validated by comparing the simulated layer geometries with those obtained from laboratory 3D-printing experiments. Within the investigated parameter range, the forces generated under the extrusion nozzle can be 6 times higher than those induced by self-weight and may cause deformations in substrate layers. Since the distribution of extrusion forces may change substantially under the nozzle for varying parameters, a novel indicator based on the yielding material is introduced to find optimal 3D-printing parameters to prevent plastic deformations in substrate layers. © 2022 Elsevier B.V.
    view abstractdoi: 10.1016/j.autcon.2022.104173
  • 2022 • 425 Algorithm for aging materials with evolving stiffness based on a multiplicative split
    Reinold, J. and Meschke, G.
    Computer Methods in Applied Mechanics and Engineering 397 (2022)
    During curing or hydration processes, materials such as polymers or fresh concrete undergo microstructural changes, which manifest themselves on the macroscopic scale as evolving material properties like strength or stiffness. Considering the increasing importance of additive manufacturing techniques using this type of “aging” materials, which typically undergo large deformations during the extrusion and deposition processes, a consistent finite strain model is required that takes evolving material properties and the proper characterization of the large deformation kinematics into account. In the proposed formulation, the problem of evolving stiffness is solved, in contrast to hypoelastic rate formulations typically used for this type of problems, by means of a multiplicative split of the deformation gradient into elastic and non-recoverable aging parts and the adoption of a hyperelastic potential. The existence of a hyperelastic potential is an advantage as it easily allows accounting for thermodynamic consistency. By introducing an internal aging parameter, a hyperelastic model based on principal logarithmic strains is adopted, to derive a novel and consistent evolution law for the aging part of the deformation gradient. The incremental and temporal discretization of the proposed constitutive model leads to a stress update scheme, which is reduced to a single multiplication of the principal logarithmic strains by a certain factor. As only minor adaptions are necessary, the proposed model is very attractive for implementations in already existing numerical models. In a benchmark study, the main aspects of the formulation are discussed, and the applicability of the proposed model is demonstrated by a computational analysis of a 3D printed concrete wall. © 2022 Elsevier B.V.
    view abstractdoi: 10.1016/j.cma.2022.115080
  • 2022 • 424 Cr3GeN: A Nitride with Orthorhombic Antiperovskite Structure
    Reitz, A. and Pazniak, H. and Shen, C. and Singh, H.K. and Jayanthi, K. and Kubitza, N. and Navrotsky, A. and Zhang, H. and Wiedwald, U. and Birkel, C.S.
    Chemistry of Materials 34 10304-10310 (2022)
    doi: 10.1021/acs.chemmater.2c01524
  • 2022 • 423 On the low temperature creep controlling mechanism in a high strength spring steel
    Remalli, N. and Münch, M. and Hasan, M. and Kishore, K.N. and Stern, F. and Baak, N. and Walther, F. and Sambandam, M. and Klapprott, S. and Rajulapati, K.V. and Brandt, R.
    Journal of Materials Research and Technology 21 2309-2315 (2022)
    doi: 10.1016/j.jmrt.2022.09.131
  • 2022 • 422 Mechanochemically-Assisted Synthesis of Polyimides
    Rensch, T. and Fabig, S. and Grätz, S. and Borchardt, L.
    ChemSusChem 15 (2022)
    Polyimides were obtained in 99 % yield in under 1 h through the “beat and heat” approach, involving solvent-free vibrational ball milling and a thermal treatment step. The influence of a plethora of additives was explored, such as Lewis acids, Lewis bases, and dehydrating agents, and the mechanochemical reaction was identified to run via a polyamic acid intermediate. The protocol was adopted to a range of substrates inaccessible through solution-based processes, including perylene tetracarboxylic acid dianhydride and melamine. Furthermore, quantum chemical calculations were conducted to identify the water removal as the crucial step in the reaction mechanism. The presented method is substantially faster and more versatile than the solution-based process. © 2021 The Authors. ChemSusChem published by Wiley-VCH GmbH
    view abstractdoi: 10.1002/cssc.202101975
  • 2022 • 421 Scale-Up of Solvent-Free, Mechanochemical Precursor Synthesis for Nanoporous Carbon Materials via Extrusion
    Rensch, T. and Chantrain, V. and Sander, M. and Grätz, S. and Borchardt, L.
    ChemSusChem (2022)
    The mechanochemical synthesis of nitrogen-rich nanoporous carbon materials has been scaled up using an extruder. Lignin, urea, and K2CO3 were extruded under heat and pressure to yield nanoporous carbons with up to 3500 m2 g−1 specific surface area after pyrolysis. The route was further broadened by applying different nitrogen sources as well as sawdust as a low-cost renewable feedstock to receive carbons with a C/N ratio of up to 15 depending on nitrogen source and extrusion parameters. The texture of obtained carbons was investigated by scanning electron microscopy as well as argon and nitrogen physisorption, while the chemical structure was analyzed by X-ray photoelectron spectroscopy. The received carbon was tested as a supercapacitor electrode, showing comparable performance to similar ball-mill-synthesized materials. Lastly, the space-time yield was applied to justify the use of a continuous reactor versus the ball mill. © 2022 The Authors. ChemSusChem published by Wiley-VCH GmbH.
    view abstractdoi: 10.1002/cssc.202200651
  • 2022 • 420 On the impact of nanometric γ’ precipitates on the tensile deformation of superelastic Co49Ni21Ga30
    Reul, A. and Lauhoff, C. and Krooß, P. and Somsen, C. and Langenkämper, D. and Gutmann, M.J. and Pedersen, B. and Hofmann, M. and Gan, W.M. and Kireeva, I. and Chumlyakov, Y.I. and Eggeler, G. and Niendorf, T. and Schmahl, W.W.
    Acta Materialia 230 (2022)
    Results are presented reporting on the martensite domain variant selection and stress-induced martensite morphology in [001]-oriented superelastic Co49Ni21Ga30 shape memory alloy (SMA) single crystals under tensile load. In situ neutron diffraction, as well as in situ optical- and confocal laser scanning microscopy were conducted focusing on three differently treated samples, i.e. in the as-grown, solution-annealed and aged condition. An aging treatment performed at 350 °C promotes the precipitation of nanoprecipitates. These second phase precipitates contribute to an increase of the number of habit plane interfaces, while reducing lamellar martensite plate thickness compared to the as-grown and solution-annealed (precipitate free) samples. During tensile loading, all samples show a stress-induced formation of martensite, characterized by one single domain variant (“detwinned”) and one set of parallel habit planes in a shear band. The results clearly show that γ’ nanoprecipitates do not necessarily promote multi-variant interaction during tensile loading. Thus, reduced recoverability in Co-Ni-Ga SMAs upon aging cannot be solely attributed to this kind of interaction as has been proposed in literature so far. © 2022
    view abstractdoi: 10.1016/j.actamat.2022.117835
  • 2022 • 419 Influence of machining on the surface integrity of high- and medium-entropy alloys
    Richter, T. and Schroepfer, D. and Rhode, M. and Boerner, A. and Neumann, R.S. and Schneider, M. and Laplanche, G.
    Materials Chemistry and Physics 275 (2022)
    High- and medium-entropy alloys (HEAs) are a quite new class of materials. They have a high potential for applications from low to high temperatures due to the excellent combination of their structural properties. Concerning their application as components; processing properties, such as machinability, have hardly been investigated so far. Hence, machinability analyses with a focus on the influence of the milling process and its basic parameters (cutting speed, feed per cutting edge) on the resulting surface integrity of specimens from an equiatomic high- (CoCrFeMnNi) and a medium- (CoCrNi) entropy alloy have been carried out. A highly innovative milling process with ultrasonic assistance (USAM) was compared to conventional milling processes. Recent studies have shown that USAM has a high potential to significantly reduce the mechanical load on the tool and workpiece surface during milling. In this study, the basic machining and ultrasonic parameters were systematically varied. After machining, the surface integrity of the alloys was analyzed in terms of topography, defects, subsurface damage, and residual stresses. It was observed that USAM reduces the cutting forces and increases the surface integrity in terms of lower tensile residual stresses and defect density near the surfaces for the CoCrFeMnNi alloy. It was shown that the cutting forces and the metallurgical influence in the sub surface region are reduced by increasing the cutting speed and reducing the feed rate per cutting edge. With the CoCrNi alloy, the tool revealed severe wear. As a result, for this alloy no influence of the parameters on the machinability could be determined. © 2021 Elsevier B.V.
    view abstractdoi: 10.1016/j.matchemphys.2021.125271
  • 2022 • 418 Theoretical formulation and computational aspects of a two-scale homogenization scheme combining the TPM and FE2 method for poro-elastic fluid-saturated porous media
    Ricken, T. and Schröder, J. and Bluhm, J. and Bartel, F.
    International Journal of Solids and Structures 241 (2022)
    The focus of this investigation lies on the development of a two-scale homogenization scheme for poro-elastic fluid-saturated porous media. For this purpose, the general concepts of the Theory of Porous Media (TPM) are combined with the FE2 method. After an introduction of the basics of TPM, the weak forms for the macroscopic and the microscopic scale will be formulated and the averaged macroscopic tangent moduli considering the microscale will be derived. Additionally, the formulation of lower level boundary conditions, which refer to the quantities that will be transmitted from the macro- to the microscale, in strict compliance with the Hill–Mandel homogeneity condition, is derived. Finally, a numerical example will be presented, pointing out the gained features of the methodology. © 2021
    view abstractdoi: 10.1016/j.ijsolstr.2021.111412
  • 2022 • 417 A hybrid exploration approach for the prediction of geological changes ahead of mechanized tunnel excavation
    Riedel, C. and Mahmoudi, E. and Trapp, M. and Lamert, A. and Hölter, R. and Zhao, C. and Musayev, K. and Baitsch, M. and König, M. and Hackl, K. and Nestorović, T. and Friederich, W.
    Journal of Applied Geophysics 203 (2022)
    doi: 10.1016/j.jappgeo.2022.104684
  • 2022 • 416 Noncontact reception of ultrasound from soft magnetic mild steel with zero applied bias field EMATs
    Rieger, K. and Erni, D. and Rueter, D.
    NDT and E International 125 (2022)
    Electromagnetic acoustic transducers (EMATs) without added magnets or bias currents receive ultrasound as bulk or Lamb waves from soft magnetic iron or mild steels. EMATs typically include bulky permanent or electromagnets for biasing magnetic fields in ultrasound reception. New compact-coils-only EMATs without additional magnets excite bias fields with pulsed strong coil currents, limiting detection time. Here, short premagnetization pulses in a simple EMAT coil allowed longer ultrasound reception from mild steel and virtually zero externally applied bias field. An unexpected long-lasting magnetic imprint inside the metal was clearly responsible and not normally expected with soft magnetic ferrous materials. Suggestions are made for mechanisms of electroacoustic coupling and permanent magnetization, even of transformer irons, after the termination of an exciting field. This contributes to novel applications of compact-coils-only EMATs without added magnets. © 2021 Elsevier Ltd
    view abstractdoi: 10.1016/j.ndteint.2021.102569
  • 2022 • 415 Temperature dependence of Fano resonances in CrPS4
    Riesner, M. and Fainblat, R. and Budniak, A.K. and Amouyal, Y. and Lifshitz, E. and Bacher, G.
    Journal of Chemical Physics 156 (2022)
    A Fano resonance, as often observed in scattering, absorption, or transmission experiments, arises from quantum interference between a discrete optical transition and a continuous background. Here, we present a temperature-dependent study on Fano resonances observed in photoluminescence from flakes of the layered semiconductor antiferromagnet chromium thiophosphate (CrPS4). Two Fano resonances with a distinctly different temperature dependence were identified. The continuous background that is responsible for the Fano resonances is attributed to the d–d transition of the optically active Cr3+ center, predominantly the spin-forbidden 2Eg → 4A2g transition with contributions of the broad-band 4T2g → 4A2g transition. The discrete states that interfere with this continuous background are suggested to arise from localized atomic phosphorus. A model idea for explaining the individual temperature dependence of the Fano resonances is presented. © 2022 Author(s).
    view abstractdoi: 10.1063/5.0079298
  • 2022 • 414 Robust and Efficient Finite Element Discretizations for Higher-Order Gradient Formulations
    Riesselmann, J. and Ketteler, J.W. and Schedensack, M. and Balzani, D.
    Lecture Notes in Applied and Computational Mechanics 98 69-90 (2022)
    doi: 10.1007/978-3-030-92672-4_3
  • 2022 • 413 Turning of high strength, austenitic stainless steels
    Rinschede, T. and Felinks, N. and Biermann, D. and Kimm, J. and Weber, S. and Niederhofer, P. and Herrera, C. and Kalveram, M.
    Tribologie und Schmierungstechnik 69 33-40 (2022)
    doi: 10.24053/TuS-2022-0004
  • 2022 • 412 Unveiling the electron-nuclear spin dynamics in an n-doped InGaAs epilayer by spin noise spectroscopy
    Rittmann, C. and Petrov, M.Y. and Kamenskii, A.N. and Kavokin, K.V. and Kuntsevich, A.Y. and Efimov, Y.P. and Eliseev, S.A. and Bayer, M. and Greilich, A.
    Physical Review B 106 (2022)
    doi: 10.1103/PhysRevB.106.035202
  • 2022 • 411 Metamaterial shields for inner protection and outer tuning through a relaxed micromorphic approach
    Rizzi, G. and Neff, P. and Madeo, A.
    Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences 380 (2022)
    In this paper, a coherent boundary value problem to model metamaterials' behaviour based on the relaxed micromorphic model is established. This boundary value problem includes well-posed boundary conditions, thus disclosing the possibility of exploring the scattering patterns of finite-size metamaterial specimens. Thanks to the simplified model's structure (few frequency- and angle-independent parameters), we are able to unveil the scattering metamaterial's response for a wide range of frequencies and angles of propagation of the incident wave. These results are an important stepping stone towards the conception of more complex large-scale meta-structures that can control elastic waves and recover energy. This article is part of the theme issue 'Wave generation and transmission in multi-scale complex media and structured metamaterials (part 1)'. © 2022 The Author(s).
    view abstractdoi: 10.1098/rsta.2021.0400
  • 2022 • 410 Towards the conception of complex engineering meta-structures: Relaxed-micromorphic modelling of low-frequency mechanical diodes/high-frequency screens
    Rizzi, G. and Tallarico, D. and Neff, P. and Madeo, A.
    Wave Motion 113 (2022)
    In this paper we show that an enriched continuum model of the micromorphic type (Relaxed Micromorphic Model) can be used to model metamaterials’ response in view of their use for meta-structural design. We focus on the fact that the reduced model's structure, coupled with the introduction of well-posed interface conditions, allows us to easily test different combinations of metamaterials’ and classical-materials bricks, so that we can eventually end-up with the conception of a meta-structure acting as a mechanical diode for low/medium frequencies and as a total screen for higher frequencies. Thanks to the reduced model's structure, we are also able to optimize this meta-structure so that the diode-behaviour is enhanced for both “pressure” and “shear” incident waves and for all possible angles of incidence. © 2022
    view abstractdoi: 10.1016/j.wavemoti.2022.102920
  • 2022 • 409 Influence of Temperature on the Binary Adsorption of Ethane and Ethene on FAU Zeolites
    Roehnert, M. and Pasel, C. and Bläker, C. and Bathen, D.
    Journal of Chemical and Engineering Data (2022)
    doi: 10.1021/acs.jced.2c00650
  • 2022 • 408 Olfactory Stem Cells for the Treatment of Spinal Cord Injury—A New Pathway to the Cure?
    Rövekamp, M. and von Glinski, A. and Volkenstein, S. and Dazert, S. and Sengstock, C. and Schildhauer, T.A. and Breisch, M.
    World Neurosurgery (2022)
    Objective: Because full functional recovery after spinal cord injury (SCI) remains a major challenge, stem cell therapies represent promising strategies to improve neurologic functions after SCI. The olfactory mucosa (OM) displays an attractive source of multipotent cells for regenerative approaches and is easily accessible by biopsies because of its exposed location. The regenerative capacity of the resident olfactory stem cells (OSCs) has been demonstrated in animal as well as clinical studies. This study aims to demonstrate the feasibility of isolation, purification and cultivation of OSCs. Methods: OM specimens were taken dorso-posterior from nasal middle turbinate. OSCs were isolated and purified using the neurosphere assay. Differentiation capacity of the OSCs in neural lineage and their behavior in a plasma clot matrix were investigated. Results: Our study demonstrated that OSCs differentiated into neural lineage and were positive for GFAP as well as β-III tubulin. Furthermore, OSCs were viable and proliferated in a plasma clot matrix. Conclusions: Because there are no standard methods for purification, characterization, and delivery of OSCs to the injury site, which is a prerequisite for the clinical approval, this study focuses on the establishment of appropriate methods and underlines the high potential of the OM for autologous cell therapeutic approaches. © 2022 Elsevier Inc.
    view abstractdoi: 10.1016/j.wneu.2022.02.019
  • 2022 • 407 Predicting Dielectric and Shear-Rheology Properties of Glass-Forming Pharmaceutical Liquids from Each Other: Applications and Limitations
    Röwekamp, L. and Moch, K. and Gainaru, C. and Böhmer, R.
    Molecular Pharmaceutics 19 1586-1597 (2022)
    doi: 10.1021/acs.molpharmaceut.2c00077
  • 2022 • 406 Chapter 11: Pathways in Classification Space: Machine Learning as a Route to Predicting Kinetics of Structural Transitions in Atomic Crystals
    Rogal, J. and Tuckerman, M.E.
    RSC Theoretical and Computational Chemistry Series 2022-January 312-348 (2022)
    Machine learning methods have become increasingly central in the development of a large variety of versatile tools for molecular simulations, many of which have the potential to advance significantly the fields of computational chemistry and physics. In this chapter, we present a framework for combining machine learning for local structure classification with the definition of a global classifier space as a basis for enhanced sampling of structural transformations in condensed phase systems. The transformation is represented by a path in classifier space, and the associated path collective variable is used to drive the process derived from changes in local structural motifs. Enhanced sampling along this type of path collective variable yields insight into the physical mechanism as well as corresponding free energy barriers of the transition. The idea is generally applicable, and the approach, as outlined here, can be adapted to a wide range of systems. © The Royal Society of Chemistry 2022.
    view abstractdoi: 10.1039/9781839164668-00312
  • 2022 • 405 Experimental investigations of plasma dynamics in the hysteresis regime of reactive RF sputter processes
    Roggendorf, J. and Berger, B. and Eremin, D. and Oberberg, M. and Engel, D. and Wölfel, C. and Zhang, Q.-Z. and Awakowicz, P. and Lunze, J. and Schulze, J.
    Plasma Sources Science and Technology 31 (2022)
    doi: 10.1088/1361-6595/ac7413
  • 2022 • 404 Boron in Ni-Rich NCM811 Cathode Material: Impact on Atomic and Microscale Properties
    Roitzheim, C. and Kuo, L.-Y. and Sohn, Y.J. and Finsterbusch, M. and Möller, S. and Sebold, D. and Valencia, H. and Meledina, M. and Mayer, J. and Breuer, U. and Kaghazchi, P. and Guillon, O. and Fattakhova-Rohlfing, D.
    ACS Applied Energy Materials 5 524-538 (2022)
    Doping of Ni-rich cathode active materials with boron is a promising way to improve their cycling stability and mitigate their degradation, but it is still not understood how this effect is achieved and where the boron is located. To receive deeper insights into the impact of doping on atomic and microscale properties, B-doped Li[Ni0.8Co0.1Mn0.1]O2 (NCM811) cathode materials were synthesized by a hydroxide coprecipitation as a model compound to verify the presence and location of boron in B-doped, Ni-rich NCM, as well as its impact on the microstructure and electrochemical properties, by a combined experimental and theoretical approach. Besides X-ray diffraction and Rietveld refinement, DFT calculation was used to find the preferred site of boron absorption and its effect on the NCM lattice parameters. It is found that boron shows a trigonal planar and tetrahedral coordination to oxygen in the Ni layers, leading to a slight increase in lattice parameter c through an electrostatic interaction with Li ions. Therefore, B-doping of NCM811 affects the crystal structure and cation disorder and leads to a change in primary particle size and shape. To experimentally prove that the observations are caused by boron incorporated into the NCM lattice, we detected, quantified, and localized boron in 2 mol % B-doped NCM811 by ion beam analysis and TOF-SIMS. It was possible to quantify boron by NRA with a depth resolution of 2 μm. We found a boron enrichment on the agglomerate surface but also, more importantly, a significant high and constant boron concentration in the interior of the primary particles near the surface, which experimentally verifies that boron is incorporated into the NCM811 lattice. ©
    view abstractdoi: 10.1021/acsaem.1c03000
  • 2022 • 403 All-Solid-State Li Batteries with NCM-Garnet-Based Composite Cathodes: The Impact of NCM Composition on Material Compatibility
    Roitzheim, C. and Sohn, Y.J. and Kuo, L.-Y. and Häuschen, G. and Mann, M. and Sebold, D. and Finsterbusch, M. and Kaghazchi, P. and Guillon, O. and Fattakhova-Rohlfing, D.
    ACS Applied Energy Materials 5 6913-6926 (2022)
    doi: 10.1021/acsaem.2c00533
  • 2022 • 402 Cyclophilin A Is Not Acetylated at Lysine‐82 and Lysine‐125 in Resting and Stimulated Platelets
    Rosa, A. and Butt, E. and Hopper, C.P. and Loroch, S. and Bender, M. and Schulze, H. and Sickmann, A. and Vorlova, S. and Seizer, P. and Heinzmann, D. and Zernecke, A.
    International Journal of Molecular Sciences 23 (2022)
    Cyclophilin A (CyPA) is widely expressed by all prokaryotic and eukaryotic cells. Upon activation, CyPA can be released into the extracellular space to engage in a variety of functions, such as interaction with the CD147 receptor, that contribute to the pathogenesis of cardiovascular diseases. CyPA was recently found to undergo acetylation at K82 and K125, two lysine residues conserved in most species, and these modifications are required for secretion of CyPA in response to cell activation in vascular smooth muscle cells. Herein we addressed whether acetylation at these sites is also required for the release of CyPA from platelets based on the potential for local delivery of CyPA that may exacerbate cardiovascular disease events. Western blot analyses confirmed the presence of CyPA in human and mouse platelets. Thrombin stimulation resulted in CyPA release from platelets; however, no acetylation was observed—neither in cell lysates nor in supernatants of both untreated and activated platelets, nor after immunoprecipitation of CyPA from platelets. Shotgun proteomics detected two CyPA peptide precursors in the recombinant protein, acetylated at K28, but again, no acetylation was found in CyPA derived from resting or stimulated platelets. Our findings suggest that acetylation of CyPA is not a major protein modification in platelets and that CyPA acetylation is not required for its secretion from platelets. © 2022 by the authors. Licensee MDPI, Basel, Switzerland.
    view abstractdoi: 10.3390/ijms23031469
  • 2022 • 401 On the determination of thermal boundary conditions for parameter identifications of thermo-mechanically coupled material models
    Rose, L. and Menzel, A.
    GAMM Mitteilungen 45 (2022)
    Identifiability and sensitivity of thermal boundary coefficients identified alongside thermal material parameters by means of full field measurements during a simple tension test are shown empirically using a simple tension test with self heating as a proof of concept. The identification is started for 10 different initial guesses, all of which converge toward the same optimum. The solution appears to be locally unique and parameters therefore independent, but a comparison against a reference solution indicates high correlation between three model parameters and the prescribed external temperatures required to model heat exchange with either air or clamping jaws. This sensitivity is further analyzed by rerunning the identification with different prescribed external temperatures and by comparing the obtained optimal parameter values. Although the model parameters are independent, optimal values for heat conduction and the heat transfer coefficients are highly correlated as well as sensitive with respect to a change, respectively, measurement error of the external temperatures. A precise fit on the basis of a simple tension test therefore requires precise measurements and a suitable material model which is able to accurately predict dissipated energy. © 2022 The Authors. GAMM - Mitteilungen published by Wiley-VCH GmbH.
    view abstractdoi: 10.1002/gamm.202200010
  • 2022 • 400 Free standing dual phase cathode tapes-scalable fabrication and microstructure optimization of garnet-based ceramic cathodes
    Rosen, M. and Finsterbusch, M. and Guillon, O. and Fattakhova-Rohlfing, D.
    Journal of Materials Chemistry A 10 2320-2326 (2022)
    To make ceramic based all-solid-state batteries competitive for the battery market, a shift from the separator supported cell-design for lab cells to a scalable, cathode-supported one is necessary to improve the energy density. Using tape casting, we were able to demonstrate for the first time all-ceramic free-standing LiCoO2 (LCO)/Li6.45Al0.05La3Zr1.6Ta0.4O12 (LLZO) mixed cathodes with high capacities and active material utilization. Further morphology engineering by introduction of a sequential layer casting enabled us to tailor the microstructure of the mixed cathodes resulting in opposite concentration gradients for the active material and the electrolyte over the thickness of the cathode. With this optimized microstructure, we were able to increase the discharge capacity of the free-standing mixed cathodes to 2.8 mA h cm-2 utilizing 99% of the theoretical capacity. For the oxide garnet-based system, both the scalable fabrication method and the achieved electrochemical performance demonstrates industrial relevance for the first time. Additionally, the obtained free-standing cathodes have sufficient mechanical stability to allow the application of hybrid and ultra-thin separators to further increase the energy density on the full cell level. This journal is © The Royal Society of Chemistry.
    view abstractdoi: 10.1039/d1ta07194g
  • 2022 • 399 Determining the sintering kinetics of Fe and FexOy-Nanoparticles in a well-defined model flow reactor
    Rosenberger, T. and Skenderović, I. and Sellmann, J. and Wollny, P. and Levish, A. and Wlokas, I. and Kempf, A. and Winterer, M. and Kruis, F.E.
    Aerosol Science and Technology 56 833-846 (2022)
    A model flow reactor provides a narrow particle temperature-residence time distribution with well-defined conditions and is mandatory to measure changes of the particle structure precisely. The experimental data of iron and iron oxide agglomerates are used to determine the sintering kinetics considering the temperature-time history of the particles. Thousand particle trajectories are tracked in a validated CFD model at three different furnace temperatures each. Strongly agglomerated particles with a small primary particle size (∼4 nm) are synthesized by spark discharge and are size-selected (25–250 nm) before sintering. The structure development is measured simultaneously with different online instrumentations and the structure calculated by means of structure models. A simple sintering model, based on the reduction of surface energy, is numerically quantified with the experimental results. The surface of the particles is strongly dependent on the primary particle size and the agglomerate structure. The chemical phase is analyzed using the offline techniques XANES, XRD, and EELS. It is observed that the addition of hydrogen led to a reduction of iron oxide to iron nanoparticles and to changes of the sintering kinetics. The sintering exponent (Formula presented.) = 1 was found to be optimal. For Fe, an activation energy (Formula presented.) of 59.15 kJ/mol and a pre-exponential factor (Formula presented.) of 1.57 104 s/m were found, for Fe3O4 an activation energy (Formula presented.) of 55.22 kJ/mol and a pre-exponential factor (Formula presented.) of 2.54 104 s/m. Copyright © 2022 American Association for Aerosol Research. © 2022 American Association for Aerosol Research.
    view abstractdoi: 10.1080/02786826.2022.2089011
  • 2022 • 398 Deep Reinforcement Learning Multi-Agent System for Resource Allocation in Industrial Internet of Things
    Rosenberger, J. and Urlaub, M. and Rauterberg, F. and Lutz, T. and Selig, A. and Bühren, M. and Schramm, D.
    Sensors 22 (2022)
    The high number of devices with limited computational resources as well as limited communication resources are two characteristics of the Industrial Internet of Things (IIoT). With Industry 4.0 emerges a strong demand for data processing in the edge, constrained primarily by the limited available resources. In industry, deep reinforcement learning (DRL) is increasingly used in robotics, job shop scheduling and supply chain. In this work, DRL is applied for intelligent resource allocation for industrial edge devices. An optimal usage of available resources of the IIoT devices should be achieved. Due to the structure of IIoT systems as well as security aspects, multi-agent systems (MASs) are preferred for decentralized decision-making. In our study, we build a network from physical and virtualized representative IIoT devices. The proposed approach is capable of dealing with several dynamic changes of the target system. Three aspects are considered when evaluating the performance of the MASs: overhead due to the MASs, improvement of the resource usage of the devices as well as latency and error rate. In summary, the agents’ resource usage with respect to traffic, computing resources and time is very low. It was confirmed that the agents not only achieve the desired results in training but also that the learned behavior is transferable to a real system. © 2022 by the authors. Licensee MDPI, Basel, Switzerland.
    view abstractdoi: 10.3390/s22114099
  • 2022 • 397 Extended kernel density estimation for anomaly detection in streaming data
    Rosenberger, J. and Müller, K. and Selig, A. and Bühren, M. and Schramm, D.
    Procedia CIRP 112 156-161 (2022)
    doi: 10.1016/j.procir.2022.09.065
  • 2022 • 396 Influence of mechanical characterization on the prediction of necking issues during sheet flow forming process
    Roula, A.M. and Mocellin, K. and Traphöner, H. and Tekkaya, A.E. and Bouchard, P.-O.
    Journal of Materials Processing Technology 306 (2022)
    Flow forming is an incremental sheet forming (ISF) process during which a sheet metal is compressed and stretched multiple times by means of one or multiple rotating roller tools. The local tool-workpiece contact zone evolves during the entire process. The necking phenomenon, which corresponds to an uncontrolled thinning of the part wall, is introduced. This phenomenon represents a major issue for ISF processes. A review of the state-of-the-art about ISF processes shows that most studies do not consider the loading path complexity when choosing the mechanical characterization test and its associated constitutive model. Besides, the prediction of necking occurring during sheet flow forming is poorly studied in the literature. In this paper, a finite element analysis (FEA) using the FORGE® software enables a detailed understanding of the loading path (strain and stress states) prevailing during the flow forming operation. Based on the peculiarities of this loading path, different mechanical tests associated with adequate constitutive models are chosen to characterize the material behavior. The ability of each constitutive model used within the FE approach to predict necking is then assessed. Results show that the best prediction of a geometry exhibiting necking issues is obtained with the cyclic in-plane torsion test (ITT) associated with its calibrated isotropic – kinematic hardening model. These results suggest that the behavior characterization under cyclic shear loadings is relevant. Using a simple tensile test with associated power-law provides a faster and conservative necking prediction. © 2022 Elsevier B.V.
    view abstractdoi: 10.1016/j.jmatprotec.2022.117620
  • 2022 • 395 Coupled microscopic and micromagnetic depth-specific analysis of plastic deformation and phase transformation of metastable austenitic steel AISI 304L by flow forming [Gekoppelte tiefenbezogene mikroskopische und mikromagnetische Analyse der in metastabilem austenitischem Stahl AISI 304L durch Drückwalzen hervorgerufenen plastischen Verformung und Phasenumwandlung]
    Rozo Vasquez, J. and Kanagarajah, H. and Arian, B. and Kersting, L. and Homberg, W. and Trächtler, A. and Walther, F.
    Praktische Metallographie/Practical Metallography 59 660-675 (2022)
    This paper presents the characterization of the microstructure evolution during flow forming of austenitic stainless steel AISI 304L. Due to plastic deformation of metastable austenitic steel, phase transformation from γ-Austenite into α'-martensite occurs. This is initiated by the formation of shear bands as product of the external stresses. By means of coupled microscopic and micromagnetic investigations, a characterization of the microstructure was carried out. In particular, this study shows the distribution of the strain-induced α'-martensite and its influence on material properties like hardness at different depths. The microstructural analyses by means of electron backscattered diffraction (EBSD) technique, evidence a higher amount of α'-martensite (ca. 23 %) close to the outer specimen surface, where the plastic deformation and the direct contact with the forming tool take place. In the middle area (ca. 1.5 mm depth from the outer surface), the portion of transformed α'-martensite drops to 7 % and in the inner surface to 2 %. These results are well correlated with microhardness and micromagnetic measurements at different depths. EBSD and atomic force microscopy (AFM) were used to make a detailed characterization of the topography and degree of deformation of the shear bands. Likewise, the mechanisms of nucleation of α'-martensite were discussed. This research contributes to the development of micromagnetic sensors to monitor the evolution of properties during flow forming. This makes them more suitable for closed-loop property control, which offers possibilities for an application-oriented and more efficient production. © 2022 Walter de Gruyter GmbH, Berlin/Boston, Germany.
    view abstractdoi: 10.1515/pm-2022-0064
  • 2022 • 394 Very fast finite element Poisson solvers on lower precision accelerator hardware: A proof of concept study for Nvidia Tesla V100
    Ruda, D. and Turek, S. and Ribbrock, D. and Zajac, P.
    International Journal of High Performance Computing Applications 36 459-474 (2022)
    Recently, accelerator hardware in the form of graphics cards including Tensor Cores, specialized for AI, has significantly gained importance in the domain of high-performance computing. For example, NVIDIA’s Tesla V100 promises a computing power of up to 125 TFLOP/s achieved by Tensor Cores, but only if half precision floating point format is used. We describe the difficulties and discrepancy between theoretical and actual computing power if one seeks to use such hardware for numerical simulations, that is, solving partial differential equations with a matrix-based finite element method, with numerical examples. If certain requirements, namely low condition numbers and many dense matrix operations, are met, the indicated high performance can be reached without an excessive loss of accuracy. A new method to solve linear systems arising from Poisson’s equation in 2D that meets these requirements, based on “prehandling” by means of hier-archical finite elements and an additional Schur complement approach, is presented and analyzed. We provide numerical results illustrating the computational performance of this method and compare it to a commonly used (geometric) multigrid solver on standard hardware. It turns out that we can exploit nearly the full computational power of Tensor Cores and achieve a significant speed-up compared to the standard methodology without losing accuracy. © The Author(s) 2022.
    view abstractdoi: 10.1177/10943420221084657
  • 2022 • 393 AN EXTENSION OF A VERY FAST DIRECT FINITE ELEMENT POISSON SOLVER ON LOWER PRECISION ACCELERATOR HARDWARE TOWARDS SEMI-STRUCTURED GRIDS
    Ruda, D. and Turek, S. and Ribbrock, D. and Zajac, P.
    World Congress in Computational Mechanics and ECCOMAS Congress (2022)
    doi: 10.23967/eccomas.2022.292
  • 2022 • 392 Low-calorific ammonia containing off-gas mixture: Modelling the conversion in HCCI engines
    Rudolph, C. and Freund, D. and Kaczmarek, D. and Atakan, B.
    Combustion and Flame 243 (2022)
    doi: 10.1016/j.combustflame.2022.112063
  • 2022 • 391 Shock-tube study on high-temperature CO formation during dry methane reforming
    Rudolph, C. and Grégoire, C.M. and Cooper, S.P. and Alturaifi, S.A. and Mathieu, O. and Petersen, E.L. and Atakan, B.
    Proceedings of the Combustion Institute (2022)
    doi: 10.1016/j.proci.2022.08.005
  • 2022 • 390 Molecular responses of a key Antarctic species to sedimentation due to rapid climate change
    Ruiz, M.B. and Servetto, N. and Alurralde, G. and Abele, D. and Harms, L. and Sahade, R. and Held, C.
    Marine Environmental Research 180 (2022)
    doi: 10.1016/j.marenvres.2022.105720
  • 2022 • 389 BioSAXS–an emerging method to accelerate, enrich and de-risk antimicrobial drug development
    Rumancev, C. and Rosenhahn, A. and Hilpert, K.
    Frontiers in Pharmacology 13 (2022)
    Antimicrobial resistance is a worldwide threat to modern health care. Low-profit margin and high risk of cross-resistance resulted in a loss of interest in big pharma, contributing to the increasing threat. Strategies to address the problem are starting to emerge. Novel antimicrobial compounds with novel modes of action are especially valued because they have a lower risk of cross-resistance. Up to now determining the mode of action has been very time and resource consuming and will be performed once drug candidates were already progressed in preclinical development. BioSAXS is emerging as a new method to test up to thousands of compounds to classify them into groups based on ultra-structural changes that correlate to their modes of action. First experiments in E. coli (gram-negative) have demonstrated that using conventional and experimental antimicrobials a classification of compounds according to their mode of action was possible. Results were backed up by transmission electron microscopy. Further work showed that also gram-positive bacteria (Staphylococcus aureus) can be used and the effects of novel antimicrobial peptides on both types of bacteria were studied. Preliminary experiments also show that BioSAXS can be used to classify antifungal drugs, demonstrated on Candida albicans. In summary, BioSAXS can accelerate and enrich the discovery of antimicrobial compounds from screening projects with a novel mode of action and hence de-risk the development of urgently needed antimicrobial drugs. Copyright © 2022 Rumancev, Rosenhahn and Hilpert.
    view abstractdoi: 10.3389/fphar.2022.947005
  • 2022 • 388 Electrochemical dealloying in a magnetic field – Tapping the potential for catalyst and material design
    Rurainsky, C. and Nettler, D.-R. and Pahl, T. and Just, A. and Cignoni, P. and Kanokkanchana, K. and Tschulik, K.
    Electrochimica Acta 426 (2022)
    Nanocatalyst optimisation through electrochemical dealloying has been employed as a successful strategy to increase catalytic activity, while reducing the need for precious metals. We present here a new pathway to influence the electrochemical dealloying, through external homogeneous magnetic fields. A homogeneous magnetic field with a flux density of 450 mT in two orientations, parallel or perpendicular to the current direction, was used during electrochemical dealloying using cyclic voltammetry of AgAu nanoparticles. We found increased porosity for low dealloying cycle numbers and improved catalytic properties after longer cycling, compared to nanoparticles dealloyed in the absence of magnetic fields. These findings demonstrate that magnetic fields applied during electrochemical dealloying have currently untapped potential that can be used to influence material properties in a new way and give researchers another powerful tool for material design. © 2022
    view abstractdoi: 10.1016/j.electacta.2022.140807
  • 2022 • 387 Interactions of water and short-chain alcohols with CoFe2O4(001) surfaces at low coverages
    Rushiti, A. and Falk, T. and Muhler, M. and Hättig, C.
    Physical Chemistry Chemical Physics 24 23195-23208 (2022)
    Iron and cobalt-based oxides crystallizing in the spinel structure are efficient and affordable catalysts for the oxidation of organics, yet, the detailed understanding of their surface structure and reactivity is limited. To fill this gap, we have investigated the (001) surfaces of cobalt ferrite, CoFe2O4, with the A- and B-layer terminations using density functional theory (DFT/PBE0) and an embedded cluster model. We have considered the five-fold coordinated Co2+/3+ (Oh), two-fold coordinated Fe2+ (Td), and an oxygen vacancy, as active sites for the adsorption of water and short-chain alcohols: methanol, ethanol, and 2-propanol, in the low coverage regime. The adsorbates dissociate upon adsorption on the Fe sites whereas the adsorption is mainly molecular on Co. At oxygen vacancies, the adsorbates always dissociate, fill the vacancy and form (partially) hydroxylated surfaces. The computed vibrational spectra for the most stable configurations are compared with results from diffuse reflectance infrared Fourier transform spectroscopy. © 2022 The Royal Society of Chemistry.
    view abstractdoi: 10.1039/d2cp02480b
  • 2022 • 386 Simulation and sensor data fusion for machine learning application
    Saadallah, A. and Finkeldey, F. and Buß, J. and Morik, K. and Wiederkehr, P. and Rhode, W.
    Advanced Engineering Informatics 52 (2022)
    The performance of machine learning algorithms depends to a large extent on the amount and the quality of data available for training. Simulations are most often used as test-beds for assessing the performance of trained models on simulated environment before deployment in real-world. They can also be used for data annotation, i.e, assigning labels to observed data, providing thus background knowledge for domain experts. We want to integrate this knowledge into the machine learning process and, at the same time, use the simulation as an additional data source. Therefore, we present a framework that allows for the combination of real-world observations and simulation data at two levels, namely the data or the model level. At the data level, observations and simulation data are integrated to form an enriched data set for learning. At the model level, the models learned from observed and simulated data separately are combined using an ensemble technique. Based on the trade-off between model bias and variance, an automatic selection of the appropriate fusion level is proposed. Our framework is validated using two case studies of very different types. The first is an industry 4.0 use case consisting of monitoring a milling process in real-time. The second is an application in astroparticle physics for background suppression. © 2022 Elsevier Ltd
    view abstractdoi: 10.1016/j.aei.2022.101600
  • 2022 • 385 A restricted additive Vanka smoother for geometric multigrid
    Saberi, S. and Meschke, G. and Vogel, A.
    Journal of Computational Physics 459 (2022)
    The solution of saddle-point problems, such as the Stokes equations, is a challenging task, especially in large-scale problems. Multigrid methods are one of the most efficient solvers for such systems of equations and can achieve convergence rates independent of the problem size. The smoother is a crucial component of multigrid methods and significantly affects its overall efficiency. We propose a Vanka-type smoother that we refer to as Restricted Additive Vanka and investigate its convergence in the context of adaptive geometric multigrid methods for the Stokes equations. The proposed smoother has the advantage of being an additive method and provides favorable properties in terms of algorithmic complexity, scalability and applicability to high-performance computing. We compare the performance of the smoother with two variants of the classical Vanka smoother using numerical benchmarks for the Stokes problem. We find that the restricted additive smoother achieves comparable convergence rates to the classical multiplicative Vanka smoother while being computationally less expensive per iteration, which results in faster solution runtimes. © 2022 Elsevier Inc.
    view abstractdoi: 10.1016/j.jcp.2022.111123
  • 2022 • 384 Laser Ablation of NiFe2O4 and CoFe2O4 Nanoparticles
    Sachse, E. and Escobar-Castillo, M. and Waag, F. and Gökce, B. and Salamon, S. and Landers, J. and Wende, H. and Lupascu, D.C.
    Nanomaterials 12 (2022)
    Pulsed laser ablation in liquids was utilized to prepare NiFe2O4 (NFO) and CoFe2O4 (CFO) nanoparticles from ceramic targets. The morphology, crystallinity, composition, and particle size distribution of the colloids were investigated. We were able to identify decomposition products formed during the laser ablation process in water. Attempts to fractionate the nanoparticles using the high-gradient magnetic separation method were performed. The nanoparticles with crystallite sizes in the range of 5–100 nm possess superparamagnetic behavior and approximately 20 Am2/kg magnetization at room temperature. Their ability to absorb light in the visible range makes them potential candidates for catalysis applications in chemical reactions and in biomedicine. © 2022 by the authors. Licensee MDPI, Basel, Switzerland.
    view abstractdoi: 10.3390/nano12111872
  • 2022 • 383 Systematic in-depth study on material constitutive parameter identification for numerical cutting simulation on 16MnCr5 comparing temperature-coupled and uncoupled Split Hopkinson pressure bars
    Saelzer, J. and Thimm, B. and Zabel, A.
    Journal of Materials Processing Technology 302 (2022)
    A comprehensive systematic comparative study on high-strain-rate tests (Split Hopkinson Pressure Bar), with and without in-situ heating of the specimens and their respective influence on the quality of empirical material models is presented. The determination of material constitutive model parameters is one of the most challenging aspects of the modelling and simulation of machining processes. Chip formation and process forces show a significant dependence on the actual constitutive model and its parameters as well as on the testing method. Typically, the influences of strain, strain rate, and temperature are investigated in separate experiments of quasi-static compression tests and tests, because the most widespread phenomenological constitutive material models (e.g. Johnson–Cook model) neglect interactions between temperature and strain rate. In contrast, the presented work demonstrates, that a coupled experimental approach of strain rate and temperature in the same test increases the quality of such uncoupled material models as well. The authors compared both approaches (separated and in situ temperature-dependent experiments) by determining the constitutive model parameters for AISI 5115 steel samples taken from a single material batch. The parameters are calculated based on a covariance matrix adaptation evolution strategy and applied in identical two-dimensional orthogonal FEM cutting simulations. Process forces and chip thickness values were used for comparison with the machining experiments. The work therefore gives new aspects to decide for a suitable experimental approach when calibrating a constitutive equation. © 2022 Elsevier B.V.
    view abstractdoi: 10.1016/j.jmatprotec.2021.117478
  • 2022 • 382 Machine-learning based analysis of time sequences for multiplexed microresonator sensor
    Saetchnikov, A. and Tcherniavskaia, E. and Saetchnikov, V. and Ostendorf, A.
    Proceedings of SPIE - The International Society for Optical Engineering 12139 (2022)
    This paper discusses an application of machine-learning solution for processing of the dynamical sensing responses collected with a multiplexed microresonator detector. Performance of a long short-term memory network (LSTM) out of bidirectional and dropout layers is analyzed on example of the experimental data collected for a temporal gradient of the local refractive index. We experimentally demonstrate the possibility for analyte parameters prediction with accuracy of > 99% based on a set of complex non-linear highly specific time sequences of the intensities radiated by the microcavities which is obtained within a timescale 4 times shorter than required to reach the steady state. Optimization possibilities in terms of the number of microresonator signals to consider for the LSTM network training along with the complexity of its architecture are analyzed. © 2022 SPIE.
    view abstractdoi: 10.1117/12.2621383
  • 2022 • 381 Deposition of Chiral Heptahelicene Molecules on Ferromagnetic Co and Fe Thin-Film Substrates
    Safari, M.R. and Matthes, F. and Ernst, K.-H. and Bürgler, D.E. and Schneider, C.M.
    Nanomaterials 12 (2022)
    The discovery of chirality-induced spin selectivity (CISS), resulting from an interaction between the electron spin and handedness of chiral molecules, has sparked interest in surface-adsorbed chiral molecules due to potential applications in spintronics, enantioseparation, and enantioselective chemical or biological processes. We study the deposition of chiral heptahelicene by sublimation under ultra-high vacuum onto bare Cu(111), Co bilayer nanoislands on Cu(111), and Fe bilayers on W(110) by low-temperature spin-polarized scanning tunneling microscopy/spectroscopy (STM/STS). In all cases, the molecules remain intact and adsorb with the proximal phenanthrene group aligned parallel to the surface. Three degenerate in-plane orientations on Cu(111) and Co(111), reflecting substrate symmetry, and only two on Fe(110), i.e., fewer than symmetry permits, indicate a specific adsorption site for each substrate. Heptahelicene physisorbs on Cu(111) but chemisorbs on Co(111) and Fe(110) bilayers, which nevertheless remain for the sub-monolayer coverage ferromagnetic and magnetized out-of-plane. We are able to determine the handedness of individual molecules chemisorbed on Fe(110) and Co(111), as previously reported for less reactive Cu(111). The demonstrated deposition control and STM/STS imaging capabilities for heptahelicene on Co/Cu(111) and Fe/W(110) substrate systems lay the foundation for studying CISS in ultra-high vacuum and on the microscopic level of single molecules in controlled atomic configurations. © 2022 by the authors.
    view abstractdoi: 10.3390/nano12193281
  • 2022 • 380 A SINGLE CAVITATION BUBBLE INDUCED DAMAGE
    Sagar, H. and el Moctar, O.
    Proceedings of the International Conference on Offshore Mechanics and Arctic Engineering - OMAE 5-A (2022)
    doi: 10.1115/OMAE2022-78536
  • 2022 • 379 Advanced oxidation processes for removal of organics from cooling tower blowdown: Efficiencies and evaluation of chlorinated species
    Saha, P. and Wang, Y. and Moradi, M. and Brüninghoff, R. and Moussavi, G. and Mei, B. and Mul, G. and H. M. Rijnaarts, H. and Bruning, H.
    Separation and Purification Technology 278 (2022)
    One of the major challenges in reusing cooling tower blowdown water (CTBD) utilizing membrane processes is its remaining organic compounds, e.g., humic substances leading to biofouling. Besides, the possible abundance of chloride in CTBD imposes the concern of the formation of chlorinated by-products. To choose a pre-treatment process for the studied CTBD composition, various advanced oxidation processes (AOPs), including electrooxidation (EO), photocatalytic degradation (PCD), heat-activated persulfate oxidation (PS), UVC/vacuum UV (UVC/VUV), and UVC processes, were evaluated and compared based on two main targets: i) highest removal and mineralization of the organics, especially humic substances; and ii) lowest formation of chlorinated by-products including adsorbable organic halides and oxychlorides. All the processes were conducted in the natural condition of the real CTBD, while solution pH was monitored. Based on results of chemical oxygen demand, total organic carbon, dissolved organic carbon, UV254 absorbance, liquid-chromatography–organic carbon detection (LC-OCD), and fluorescence excitation-emission matrices (FEEM), it is concluded that PS leads to complete removal of organic compounds along with the lowest formation of low molecular weight organic acids and organic neutrals. FEEM and LC-OCD data also indicated that EO, PCD, and UVC/VUV processes brought about substantial removal of organic compounds and broke down the humic substances into low molecular weight building blocks and organics. Besides, EO exhibited the highest AOX and oxychlorides formation, while these were limited when using the other AOPs. Summarizing, PS, PCD, and UVC/VUV were efficient processes for the degradation and mineralization of organics without generating significant amounts of chlorinated by-products. © 2021 The Author(s)
    view abstractdoi: 10.1016/j.seppur.2021.119537
  • 2022 • 378 Hydration in aqueous NaCl
    Sahle, C.J. and de Clermont Gallerande, E. and Niskanen, J. and Longo, A. and Elbers, M. and Schroer, M.A. and Sternemann, C. and Jahn, S.
    Physical Chemistry Chemical Physics 24 16075-16084 (2022)
    Atomistic details about the hydration of ions in aqueous solutions are still debated due to the disordered and statistical nature of the hydration process. However, many processes from biology, physical chemistry to materials sciences rely on the complex interplay between solute and solvent. Oxygen K-edge X-ray excitation spectra provide a sensitive probe of the local atomic and electronic surrounding of the excited sites. We used ab initio molecular dynamics simulations together with extensive spectrum calculations to relate the features found in experimental oxygen K-edge spectra of a concentration series of aqueous NaCl with the induced structural changes upon solvation of the salt and distill the spectral fingerprints of the first hydration shells around the Na+- and Cl−-ions. By this combined experimental and theoretical approach, we find the strongest spectral changes to indeed result from the first hydration shells of both ions and relate the observed shift of spectral weight from the post- to the main-edge to the origin of the post-edge as a shape resonance. © 2022 The Royal Society of Chemistry.
    view abstractdoi: 10.1039/d2cp00162d
  • 2022 • 377 The orthorhombic-tetragonal morphotropic phase boundary in high-pressure synthesized BiMg0.5Ti0.5O3–BiZn0.5Ti0.5O3 perovskite solid solutions
    Salak, A.N. and Shvartsman, V.V. and Cardoso, J.P. and Pushkarev, A.V. and Radyush, Y.V. and Olekhnovich, N.M. and Khalyavin, D.D. and Vieira, J.M. and Čižmár, E. and Feher, A.
    Journal of Physics and Chemistry of Solids 161 (2022)
    (1–x)BiMg0.5Ti0.5O3−xBiZn0.5Ti0.5O3 [(1−x)BMT–xBZT] ceramics of perovskite solid solutions, in which BMT and BZT are lead-free structural analogs of PbZrO3 and PbTiO3, respectively, have been synthesized under high pressure. It was found that the as-prepared compositions with a relative BZT content of &lt;75 mol% are orthorhombic (space group Pnnm), while those with a BZT content above this value are tetragonal (P4mm). In the solution with x = 0.75, both phases coexist forming a morphotropic phase boundary (MPB). The compositional dependence of the normalized unit cell volume exhibits a ∼5% jump at x = 0.75. At the same time, the microstructure of the obtained (1–x)BMT−xBZT ceramics shows no particular variation with the chemical composition over MPB. Piezoresponse force microscopy measurements indicate the ferroelectric state of the studied materials and allowed one to estimate their intrinsic piezoelectric coefficients. © 2021 Elsevier Ltd
    view abstractdoi: 10.1016/j.jpcs.2021.110392
  • 2022 • 376 Elucidating dislocation core structures in titanium nitride through high-resolution imaging and atomistic simulations
    Salamania, J. and Sangiovanni, D.G. and Kraych, A. and Calamba Kwick, K.M. and Schramm, I.C. and Johnson, L.J.S. and Boyd, R. and Bakhit, B. and Hsu, T.W. and Mrovec, M. and Rogström, L. and Tasnádi, F. and Abrikosov, I.A. and Odén, M.
    Materials and Design 224 (2022)
    Although titanium nitride (TiN) is among the most extensively studied and thoroughly characterized thin-film ceramic materials, detailed knowledge of relevant dislocation core structures is lacking. By high-resolution scanning transmission electron microscopy (STEM) of epitaxial single crystal (001)-oriented TiN films, we identify different dislocation types and their core structures. These include, besides the expected primary a/2{110}〈11–0〉 dislocation, Shockley partial dislocations a/6{111}〈112–〉 and sessile Lomer edge dislocations a/2{100}〈011〉. Density-functional theory and classical interatomic potential simulations complement STEM observations by recovering the atomic structure of the different dislocation types, estimating Peierls stresses, and providing insights on the chemical bonding nature at the core. The generated models of the dislocation cores suggest locally enhanced metal–metal bonding, weakened Ti-N bonds, and N vacancy-pinning that effectively reduces the mobilities of {110}〈11–0〉 and {111}〈112–〉 dislocations. Our findings underscore that the presence of different dislocation types and their effects on chemical bonding should be considered in the design and interpretations of nanoscale and macroscopic properties of TiN. © 2022 The Authors
    view abstractdoi: 10.1016/j.matdes.2022.111327
  • 2022 • 375 Tandem.MINT Taking advantage of the pandemic
    Salzinger, J. and Schiffmann, L.-K. and Berbuir, U. and Frerich, S.
    International Conference on Higher Education Advances 2022-June 993-1000 (2022)
    doi: 10.4995/HEAd22.2022.14235
  • 2022 • 374 Discovering atomistic pathways for supply of metal atoms from methyl-based precursors to graphene surface
    Sangiovanni, D.G. and Faccio, R. and Gueorguiev, G.K. and Kakanakova-Georgieva, A.
    Physical Chemistry Chemical Physics 25 829-837 (2022)
    doi: 10.1039/d2cp04091c
  • 2022 • 373 Operando Scanning Electrochemical Probe Microscopy during Electrocatalysis
    Santana Santos, C. and Jaato, B.N. and Sanjuán, I. and Schuhmann, W. and Andronescu, C.
    Chemical Reviews (2022)
    doi: 10.1021/acs.chemrev.2c00766
  • 2022 • 372 Correlative Electrochemical Microscopy for the Elucidation of the Local Ionic and Electronic Properties of the Solid Electrolyte Interphase in Li-Ion Batteries
    Santos, C.S. and Botz, A. and Bandarenka, A.S. and Ventosa, E. and Schuhmann, W.
    Angewandte Chemie - International Edition 61 (2022)
    The solid-electrolyte interphase (SEI) plays a key role in the stability of lithium-ion batteries as the SEI prevents the continuous degradation of the electrolyte at the anode. The SEI acts as an insulating layer for electron transfer, still allowing the ionic flux through the layer. We combine the feedback and multi-frequency alternating-current modes of scanning electrochemical microscopy (SECM) for the first time to assess quantitatively the local electronic and ionic properties of the SEI varying the SEI formation conditions and the used electrolytes in the field of Li-ion batteries (LIB). Correlations between the electronic and ionic properties of the resulting SEI on a model Cu electrode demonstrates the unique feasibility of the proposed strategy to provide the two essential properties of an SEI: ionic and electronic conductivity in dependence on the formation conditions, which is anticipated to exhibit a significant impact on the field of LIBs. © 2022 The Authors. Angewandte Chemie International Edition published by Wiley-VCH GmbH.
    view abstractdoi: 10.1002/anie.202202744
  • 2022 • 371 Comprehensive investigation of crystallographic, spin-electronic and magnetic structure of (Co0.2Cr0.2Fe0.2Mn0.2Ni0.2)3O4: Unraveling the suppression of configuration entropy in high entropy oxides
    Sarkar, A. and Eggert, B. and Witte, R. and Lill, J. and Velasco, L. and Wang, Q. and Sonar, J. and Ollefs, K. and Bhattacharya, S.S. and Brand, R.A. and Wende, H. and de Groot, F.M.F. and Clemens, O. and Hahn, H. and Kruk, R.
    Acta Materialia 226 (2022)
    High entropy oxides (HEOs) are a rapidly emerging class of functional materials consisting of multiple principal cations. The original paradigm of HEOs assumes cationic occupations with the highest possible configurational entropy allowed by the composition and crystallographic structure. However, the fundamental question remains on the actual degree of configurational disorder in HEOs, especially, in systems with a low enthalpy barriers for cation anti-site mixing. Considering the experimental limitations due to the presence of multiple principal cations in HEOs, here we utilize a robust and cross-referenced characterization approach using soft X-ray magnetic circular dichroism, hard X-ray absorption spectroscopy, Mössbauer spectroscopy, neutron powder diffraction and SQUID magnetometry to study the competition between crystal field stabilization energy and configurational entropy governing the cation occupation in a spinel HEO (S-HEO), (Co0.2Cr0.2Fe0.2Mn0.2Ni0.2)3O4. In contrast to the previous studies, the derived complete structural and spin-electronic model, (Co0.6Fe0.4)(Cr0.3Fe0.1Mn0.3Ni0.3)2O4, highlights a significant deviation from the hitherto assumed paradigm of entropy-driven non-preferential distribution of cations in HEOs. An immediate correlation of this result can be drawn with bulk as well as the local element specific magnetic properties, which are intrinsically dictated by cationic occupations in spinels. The real local lattice picture presented here provides an alternate viewpoint on ionic arrangement in HEOs, which is of fundamental interest for predicting and designing their structure-dependent functionalities. © 2021 Acta Materialia Inc.
    view abstractdoi: 10.1016/j.actamat.2021.117581
  • 2022 • 370 Machine learning for molecular simulations of crystal nucleation and growth
    Sarupria, S. and Hall, S.W. and Rogal, J.
    MRS Bulletin (2022)
    Abstract: Molecular simulations are a powerful tool in the study of crystallization and polymorphic transitions yielding detailed information of transformation mechanisms with high spatiotemporal resolution. However, characterizing various crystalline and amorphous phases as well as sampling nucleation events and structural transitions remain extremely challenging tasks. The integration of machine learning with molecular simulations has the potential of unprecedented advancement in the area of crystal nucleation and growth. In this article, we discuss recent progress in the analysis and sampling of structural transformations aided by machine learning and the resulting potential future directions opening in this area. Graphical Abstract: [Figure not available: see fulltext.]. © 2022, The Author(s), under exclusive License to the Materials Research Society.
    view abstractdoi: 10.1557/s43577-022-00407-1
  • 2022 • 369 Deep learning framework for uncovering compositional and environmental contributions to pitting resistance in passivating alloys
    Sasidhar, K.N. and Siboni, N.H. and Mianroodi, J.R. and Rohwerder, M. and Neugebauer, J. and Raabe, D.
    npj Materials Degradation 6 (2022)
    We have developed a deep-learning-based framework for understanding the individual and mutually combined contributions of different alloying elements and environmental conditions towards the pitting resistance of corrosion-resistant alloys. A fully connected deep neural network (DNN) was trained on previously published datasets on corrosion-relevant electrochemical metrics, to predict the pitting potential of an alloy, given the chemical composition and environmental conditions. Mean absolute error of 170 mV in the predicted pitting potential, with an R-square coefficient of 0.61 was obtained after training. The trained DNN model was used for multi-dimensional gradient descent optimization to search for conditions maximizing the pitting potential. Among environmental variables, chloride-ion concentration was universally found to be detrimental. Increasing the amounts of dissolved nitrogen/carbon was found to have the strongest beneficial influence in many alloys. Supersaturating transition metal high entropy alloys with large amounts of interstitial nitrogen/carbon has emerged as a possible direction for corrosion-resistant alloy design. © 2022, The Author(s).
    view abstractdoi: 10.1038/s41529-022-00281-x
  • 2022 • 368 Damage localization and characterization using one-dimensional convolutional neural network and a sparse network of transducers
    Sattarifar, A. and Nestorović, T.
    Engineering Applications of Artificial Intelligence 115 (2022)
    Early damage identification and continuous system monitoring save dramatically maintenance costs and increase the lifespan of priceless structures. Convolutional neural networks (CNNs) have attracted the attention of the structural health monitoring (SHM) community in recent years due to their great potential for identifying underlying data patterns. However, employing two-dimensional convolutional layers in a CNN necessitates the use of strong computing resources. Therefore, based on the present state-of-the-art technical solutions, a two-dimensional CNN is not suitable for real-time SHM applications with stand-alone processing units. One-dimensional convolutional networks (1D-CNN) have recently been employed in Ultrasonic Guided Wave-based (UGW-based) damage detection to address the aforementioned disadvantage. In this paper, a methodology for damage assessment at three levels – detection, localization, and characterization – based on 1D-CNN is put forward. Furthermore, the sequence length of the time-domain signals is significantly shortened by the application of a novel approach for processing them. Additionally, it is shown to what extend this method can improve the distinguishability between datapoints obtained from various damage scenarios. Consequently, by reducing the dimensionality of the problem, the proposed approach significantly reduces the memory usage of the classification algorithm. Experimental measurements as well as Numerical simulations, in which various damage scenarios such as corrosion, circular hole and cracks have been considered, are carried out to evaluate the efficacy of the proposed algorithm. It is shown that the suggested approach has benefits in terms of true classification rate of instances (above 93 percent for detection, localization, and characterization), computing time, in-situ monitoring, and noise resilience. © 2022 Elsevier Ltd
    view abstractdoi: 10.1016/j.engappai.2022.105273
  • 2022 • 367 Emergence of Machine Learning Techniques in Ultrasonic Guided Wave-based Structural Health Monitoring: A Narrative Review
    Sattarifar, A. and Nestorović, T.
    International Journal of Prognostics and Health Management 13 (2022)
    Identification of damage in its early stage can have a great contribution in decreasing the maintenance costs and pro-longing the life of valuable structures. Although conventional damage detection techniques have a mature background, their widespread application in industrial practice is still missing. In recent years the application of Machine Learning (ML) algorithms have been more and more exploited in structural health monitoring systems (SHM). Because of the superior capabilities of ML approaches in recognizing and classifying available patterns in a dataset, they have demonstrated a significant improvement in traditional damage identification algorithms. This review study focuses on the use of machine learning (ML) approaches in Ultrasonic Guided Wave (UGW)-based SHM, in which a structure is continually monitored using permanent sensors. Accordingly, multiple steps required for performing damage detection through UGWs are stated. Moreover, it is outlined that the employment of ML techniques for UGW-based damage detection can be sub-tended into two main phases: (1) extracting features from the data set, and reducing the dimension of the data space, (2) processing the patterns for revealing patterns, and classification of instances. With this regard, the most frequent techniques for the realization of those two phases are elaborated. This study shows the great potential of ML algorithms to as-sist and enhance UGW-based damage detection algorithms. © 2022, Prognostics and Health Management Society. All rights reserved.
    view abstractdoi: 10.36001/ijphm.2022.v13i1.3107
  • 2022 • 366 Unravelling Anion Solvation in Water-Alcohol Mixtures by Single Entity Electrochemistry
    Saw, E.N. and Kanokkanchana, K. and Amin, H.M.A. and Tschulik, K.
    ChemElectroChem (2022)
    Single entity electrochemistry is employed to gain insights into ion solvation in solvent mixtures. To this end, the time required for the oxidation of individual indicator nanoparticles to sparingly soluble products is used to probe ionic diffusion, and hence gain new insights into the solvation properties of solvent mixtures. Herein, water-ethanol or water-methanol mixtures of different compositions are analyzed following this new approach, using silver nanoparticle oxidation in the presence of chloride and iodide as a complementary indicator reaction. For increasing concentrations of the bulkier alcohol molecules in the mixtures with water, an increasing content of alcohol molecules in the halide's solvation shell is detected by the observation of hindered halide diffusion. The extent of this solvent replacement is shown to scale with the charge density of the ions and the experimental results are rationalized with respect to literature-derived thermodynamic data, highlighting the ability of single entity electrochemistry to explore solvation in solvent mixtures. © 2022 The Authors. ChemElectroChem published by Wiley-VCH GmbH.
    view abstractdoi: 10.1002/celc.202101435
  • 2022 • 365 Domain truncation methods for the wave equation in a homogenization limit
    Schäffner, M. and Schweizer, B. and Tjandrawidjaja, Y.
    Applicable Analysis 101 4149-4170 (2022)
    We consider the wave equation (Formula presented.) on an unbounded domain (Formula presented.) for highly oscillatory coefficients (Formula presented.) with the scaling (Formula presented.). We consider settings in which the homogenization process for this equation is well understood, which means that (Formula presented.) holds for the solution (Formula presented.) of the homogenized problem (Formula presented.). In this context, domain truncation methods are studied. The goal is to calculate an approximate solution (Formula presented.) on a subdomain, say (Formula presented.). We are ready to solve the ε-problem on (Formula presented.), but we want to solve only homogenized problems on the unbounded domains (Formula presented.) or (Formula presented.). The main task is to define transmission conditions at the interface to have small differences (Formula presented.). We present different methods and corresponding (Formula presented.) error estimates. © 2022 Informa UK Limited, trading as Taylor & Francis Group.
    view abstractdoi: 10.1080/00036811.2022.2054416
  • 2022 • 364 Lifecycle-Based View on Cyber-Physical System Models Using Extended Hidden Markov Models
    Schaffeld, M. and Bernemann, R. and Weis, T. and Konig, B. and Matkovic, V.
    2022 20th ACM-IEEE International Conference on Formal Methods and Models for System Design, MEMOCODE 2022 (2022)
    doi: 10.1109/MEMOCODE57689.2022.9954592
  • 2022 • 363 Environment-induced decay dynamics of antiferromagnetic order in Mott-Hubbard systems
    Schaller, G. and Queisser, F. and Szpak, N. and König, J. and Schützhold, R.
    Physical Review B 105 (2022)
    We study the dissipative Fermi-Hubbard model in the limit of weak tunneling and strong repulsive interactions, where each lattice site is tunnel-coupled to a Markovian fermionic bath. For cold baths at intermediate chemical potentials, the Mott insulator property remains stable and we find a fast relaxation of the particle number towards half filling. On longer time scales, we find that the antiferromagnetic order of the Mott-Néel ground state on bipartite lattices decays, even at zero temperature. For zero and nonzero temperatures, we quantify the different relaxation time scales by means of waiting time distributions, which can be derived from an effective (non-Hermitian) Hamiltonian and obtain fully analytic expressions for the Fermi-Hubbard model on a tetramer ring. © 2022 American Physical Society.
    view abstractdoi: 10.1103/PhysRevB.105.115139
  • 2022 • 362 ERK1/2 Activity Is Critical for the Outcome of Ischemic Stroke
    Schanbacher, C. and Bieber, M. and Reinders, Y. and Cherpokova, D. and Teichert, C. and Nieswandt, B. and Sickmann, A. and Kleinschnitz, C. and Langhauser, F. and Lorenz, K.
    International Journal of Molecular Sciences 23 (2022)
    Ischemic disorders are the leading cause of death worldwide. The extracellular signal-regulated kinases 1 and 2 (ERK1/2) are thought to affect the outcome of ischemic stroke. However, it is under debate whether activation or inhibition of ERK1/2 is beneficial. In this study, we report that the ubiquitous overexpression of wild-type ERK2 in mice (ERK2wt ) is detrimental after transient occlusion of the middle cerebral artery (tMCAO), as it led to a massive increase in infarct volume and neurological deficits by increasing blood–brain barrier (BBB) leakiness, inflammation, and the number of apoptotic neurons. To compare ERK1/2 activation and inhibition side-by-side, we also used mice with ubiquitous overexpression of the Raf-kinase inhibitor protein (RKIPwt ) and its phosphorylation-deficient mutant RKIPS153A, known inhibitors of the ERK1/2 signaling cascade. RKIPwt and RKIPS153A attenuated ischemia-induced damages, in particular via anti-inflammatory signaling. Taken together, our data suggest that stimulation of the Raf/MEK/ERK1/2-cascade is severely detrimental and its inhibition is rather protective. Thus, a tight control of the ERK1/2 signaling is essential for the outcome in response to ischemic stroke. © 2022 by the authors. Licensee MDPI, Basel, Switzerland.
    view abstractdoi: 10.3390/ijms23020706
  • 2022 • 361 Rapid thermal processing of garnet-based composite cathodes
    Scheld, W.S. and Lobe, S. and Dellen, C. and Ihrig, M. and Häuschen, G. and Hoff, L.C. and Finsterbusch, M. and Uhlenbruck, S. and Guillon, O. and Fattakhova-Rohlfing, D.
    Journal of Power Sources 545 (2022)
    doi: 10.1016/j.jpowsour.2022.231872
  • 2022 • 360 Rapid thermal sintering of screen-printed LiCoO2 films
    Scheld, W.S. and Lobe, S. and Uhlenbruck, S. and Dellen, C. and Sohn, Y.J. and Hoff, L.C. and Vondahlen, F. and Guillon, O. and Fattakhova-Rohlfing, D.
    Thin Solid Films 749 (2022)
    doi: 10.1016/j.tsf.2022.139177
  • 2022 • 359 Strong magnetoelectric coupling at an atomic nonmagnetic electromagnetic probe in bismuth ferrite
    Schell, J. and Schmuck, M. and Efe, İ. and Dang, T.T. and Gonçalves, J.N. and Lewin, D. and Castillo, M.E. and Shvartsman, V.V. and Costa, Â.R.G. and Köster, U. and Vianden, R. and Noll, C. and Lupascu, D.C.
    Physical Review B 105 (2022)
    Isolated nonmagnetic substitutional defect ions experience huge coupled electric magnetic interaction in the single-phase multiferroic BiFeO3. In the ferroelectric state above the magnetic Néel temperature TN, the electric environment generates a single symmetric electric field gradient (EFG) parallel to the electric polarization direction. Below TN, a distinct magnetic interaction arises, monitored by the probe nuclei via their magnetic moment. Two magnetic environments arise, given by the relative angle of the local magnetic moment within its easy magnetic plane with respect to the EFG orientation. The angle between field gradient orientation and magnetic field direction is the most stable fitting parameter. The magnetic interaction concomitantly increases the EFG dramatically which reflects an outstandingly large local magnetoelectric coupling. In the set of best fits, two different electric environments form concurrently with two distinctly different local magnetic fields. The magnetic ordering in BiFeO3 thus completely distorts the electric environment of the nonmagnetic probe nucleus. The implications for the local effect of dopants in BiFeO3 are discussed. A third probe environment arising independent of temperature is identified and associated with an iron vacancy. © 2022 American Physical Society.
    view abstractdoi: 10.1103/PhysRevB.105.094102
  • 2022 • 358 Silicon based Metamaterials for Dielectric Waveguides in the THz Range
    Schenkel, F. and Barengolts, I. and Schmitt, L. and Rolfes, I. and Hoffmann, M. and Barowski, J.
    Mediterranean Microwave Symposium 2022-May (2022)
    doi: 10.1109/MMS55062.2022.9825523
  • 2022 • 357 Contact-Free Plasma State Supervision Utilizing a Modified Industrial 25 GHz FMCW Radar System
    Schenkel, F. and Baer, C. and Rolfes, I. and Schulz, C.
    Asia-Pacific Microwave Conference Proceedings, APMC 2022-November 937-939 (2022)
  • 2022 • 356 Chiral superconductivity with enhanced quantized Hall responses in moiré transition metal dichalcogenides
    Scherer, M.M. and Kennes, D.M. and Classen, L.
    npj Quantum Materials 7 (2022)
    doi: 10.1038/s41535-022-00504-z
  • 2022 • 355 Gold Nanorods Induce Endoplasmic Reticulum Stress and Autocrine Inflammatory Activation in Human Neutrophils
    Schirrmann, R. and Erkelenz, M. and Lamers, K. and Sritharan, O. and Nachev, M. and Sures, B. and Schlücker, S. and Brandau, S.
    ACS Nano 16 11011-11026 (2022)
    Gold nanorods (AuNRs) are promising agents for diverse biomedical applications such as drug and gene delivery, bioimaging, and cancer treatment. Upon in vivo application, AuNRs quickly interact with cells of the immune system. On the basis of their strong intrinsic phagocytic activity, polymorphonuclear neutrophils (PMNs) are specifically equipped for the uptake of particulate materials such as AuNRs. Therefore, understanding the interaction of AuNRs with PMNs is key for the development of safe and efficient therapeutic applications. In this study, we investigated the uptake, intracellular processing, and cell biological response induced by AuNRs in PMNs. We show that uptake of AuNRs mainly occurs via phagocytosis and macropinocytosis with rapid deposition of AuNRs in endosomes within 5 min. Within 60 min, AuNR uptake induced an unfolded protein response (UPR) along with induction of inositol-requiring enzyme 1 α (IREα) and features of endoplasmic reticulum (ER) stress. This early response was followed by a pro-inflammatory autocrine activation loop that involves LOX1 upregulation on the cell surface and increased secretion of IL8 and MMP9. Our study provides comprehensive mechanistic insight into the interaction of AuNRs with immune cells and suggests potential targets to limit the unwanted immunopathological activation of PMNs during application of AuNRs. © 2022 American Chemical Society.
    view abstractdoi: 10.1021/acsnano.2c03586
  • 2022 • 354 Unraveling the influence of dissolved gases on permeate flux in organic solvent nanofiltration – Experimental analysis
    Schlüter, S. and Huxoll, F. and Grenningloh, K. and Sadowski, G. and Petzold, M. and Böhm, L. and Kraume, M. and Skiborowski, M.
    Separation and Purification Technology 295 (2022)
    The first step in quantifying the performance of organic solvent nanofiltration membranes are usually lab-scale experiments with respect to flux and rejection. The necessary pressurization of the feed is either realized mechanically by a high-pressure pump or by means of a pressurized inert gas. While the latter option is most frequently applied, the gas may dissolve in the feed mixture and permeate through the membrane, affecting the transport of the other components. This potential effect is commonly neglected, inherently assuming that the gas solubility is negligible. The current study provides a systematic experimental investigation and analysis of the impact of dissolved gases on solvent flux for a hydrophilic DuraMem membrane, with gas solubilities assessed through PC-SAFT. The results prove that a gas with low solubility has a negligible effect on the solvent flux. In contrast, an increasing gas solubility may result in significant gas flux through the membrane with a considerable effect on the solvent flux. Furthermore, the correlation of the solvent flux with the gas solubility in the feed mixture is strongly non-linear. Therefore, gas solubility is recommended to be critically evaluated when conducting OSN experiments, specifically considering the final application. In that context, the permeation of dissolved gas has to be actively accounted for in OSN experiments for gas–liquid systems. © 2022 Elsevier B.V.
    view abstractdoi: 10.1016/j.seppur.2022.121265
  • 2022 • 353 Influence of the cutting edge on the surface integrity in BTA deep hole drilling-part 1: Design of experiments, roughness and forces
    Schmidt, R. and Strodick, S. and Walther, F. and Biermann, D. and Zabel, A.
    Procedia CIRP 108 329-334 (2022)
    doi: 10.1016/j.procir.2022.03.055
  • 2022 • 352 Measurement and analysis of the thermal load in the bore subsurface zone during BTA deep hole drilling
    Schmidt, R. and Brause, L. and Strodick, S. and Walther, F. and Biermann, D. and Zabel, A.
    Procedia CIRP 107 375-380 (2022)
    doi: 10.1016/j.procir.2022.04.061
  • 2022 • 351 Data-oriented description of texture-dependent anisotropic material behavior
    Schmidt, J. and Biswas, A. and Vajragupta, N. and Hartmaier, A.
    Modelling and Simulation in Materials Science and Engineering 30 (2022)
    doi: 10.1088/1361-651X/ac7739
  • 2022 • 350 Cost Analysis of Automated Additive Printer Farms
    Schmidt, C. and Finsterwalder, F. and Griesbaum, R. and Sehrt, J.T.
    IOP Conference Series: Earth and Environmental Science 1048 (2022)
    Automated additive printer farms, which operate several printers in parallel and thus increase the productivity, are an efficient way to realize a fully flexible mass production, as has been shown by a number of examples. By means of a specifically developed calculation method and virtual representations of various printer farm concepts in a simulation environment, various farm concepts are analyzed regarding the cost structure and the productivity. Also, an automated farm consisting of several low-cost printers is compared to an industrial printer. Subsequently, future scenarios are set up taking into account economic and technological trends allowing an estimation of the impact on the manufacturing costs of automated additive printer farms. In this paper, the analysis is based upon the Fused Layer Modeling (FLM) process, but to a large extent the findings can be transferred to other additive manufacturing processes, for example stereolithography (SL) or digital light processing (DLP). © 2022 Published under licence by IOP Publishing Ltd.
    view abstractdoi: 10.1088/1755-1315/1048/1/012008
  • 2022 • 349 Compensating Probe Misplacements in On-Wafer S-Parameters Measurements
    Schmidt, R. and Clochiatti, S. and Mutlu, E. and Weimann, N. and Ferrero, A. and Dieudonne, M. and Schreurs, D.M.M.-P.
    IEEE Transactions on Microwave Theory and Techniques 70 5213-5223 (2022)
    As the maximum frequency of electronics is rising, on-wafer measurements play an important role in modeling of integrated devices. Most of the time, due to the lack of measurement accuracy beyond 110 GHz, such models are usually extracted at frequencies much below their working frequencies and are subsequently extrapolated. The validity of such models is then mostly verified after fabrication of the complete chip, with a simple pass and fail test. This is stating the necessity of enhancing measurement results by any means possible, i.e., to reduce the overall uncertainty in such measurements. It is widely accepted that one of the main sources of uncertainty in such measurements is probe contact repeatability, since it is difficult to reach position accuracy below a few micrometers. We are presenting in this article a method to model the S -parameter variation with probe position on the pads, which can then be used to either estimate contact repeatability uncertainty or further enhance measurement results. The approach is validated based on the measurements performed at 500 GHz. © 1963-2012 IEEE.
    view abstractdoi: 10.1109/TMTT.2022.3205606
  • 2022 • 348 Three-body bound states in antiferromagnetic spin ladders
    Schmiedinghoff, G. and Müller, L. and Kumar, U. and Uhrig, G.S. and Fauseweh, B.
    Communications Physics 5 (2022)
    Stable bound quantum states are ubiquitous in nature. Mostly, they result from the interaction of only pairs of particles, so called two-body interactions, even when large complex many-particle structures are formed. We show that three-particle bound states occur in a generic, experimentally accessible solid state system: antiferromagnetic spin ladders, related to high-temperature superconductors. This binding is induced by genuine three-particle interactions; without them there is no bound state. We compute the dynamic exchange structure factor required for the experimental detection of the predicted state by resonant inelastic X-ray scattering for realistic material parameters. Our work enables us to quantify these elusive interactions and unambiguously establishes their effect on the dynamics of the quantum many-particle state. © 2022, The Author(s).
    view abstractdoi: 10.1038/s42005-022-00986-0
  • 2022 • 347 Efficient flow equations for dissipative systems
    Schmiedinghoff, G. and Uhrig, G.S.
    SciPost Physics 13 (2022)
    doi: 10.21468/SciPostPhys.13.6.122
  • 2022 • 346 A passive acceleration sensor with mechanical 6 bit memory and mechanical analog-to-digital converter
    Schmitt, P. and Hoffmann, M.
    Micro and Nano Engineering 15 (2022)
    doi: 10.1016/j.mne.2022.100142
  • 2022 • 345 THz Phase Shifter based on MEMS-Actuated Slot Waveguides
    Schmitt, L. and Barowski, J. and Hoffmann, M.
    2022 5th International Workshop on Mobile Terahertz Systems, IWMTS 2022 (2022)
    doi: 10.1109/IWMTS54901.2022.9832456
  • 2022 • 344 Tracing the Force-Displacement Characteristics of Non-Linear Microsystems by In-Situ Characterization
    Schmitt, P. and Hoffmann, M.
    IEEE Symposium on Mass Storage Systems and Technologies 2022-January 691-694 (2022)
    doi: 10.1109/MEMS51670.2022.9699564
  • 2022 • 343 A Passive Micromechanical Counting Mechanism
    Schmitt, P. and Hoffmann, M.
    Proceedings of IEEE Sensors 2022-October (2022)
    doi: 10.1109/SENSORS52175.2022.9967002
  • 2022 • 342 Experimental and numerical investigations of micro-meso damage evolution for a WC/Co-type tool material
    Schneider, Y. and Weber, U. and Xu, C. and Zielke, R. and Schmauder, S. and Tillmann, W.
    Materialia 21 (2022)
    Commercial Co/WC/diamond composites with 90vol.% Co also belong to hard metals and, as a kind of tool materials, are very useful. Their deformation behavior can be both ductile and quasi-brittle, determined by the diamond portion and local morphology. Another characteristic is that submicron-sized WC particles, possessing non-negligible strengthening influence due to the size effect, cannot be fully present in a representative microstructure. This work emphasizes the local damage evolutions’ dependence on microstructural features. Rice&Tracey damage and cohesive zone model describe the ductile and quasi-brittle damage behavior. The mechanism-based strain gradient plasticity takes the size effect of submicron-sized WC particles into consideration. Both real and artificial microstructures are used. Besides homogeneous boundary conditions (BCs), the periodic BCs are also applied in a 2D damage simulation. This work proves that FE models with two phases, the homogenized Co-WC matrix and diamond particles, can correctly predict damage evolution. FE results show that the WC phase has a higher mean stress value than the diamond phase, which is proved by the nano-indentation test. From FE simulation results, local hot spots appear in the matrix closed to sharp diamond corners/edges and crossing regions of shear bands. The experimental and numerical results are compared on micro and macro scales. For the local strain distribution and the damage development, numerical predictions match the reality well, even in morphological details. Furthermore, since the published data about WC-Co type tool materials with Co>50vol.% are rare, the obtained knowledge in this work also contributes to the data collection. © 2022 The Authors
    view abstractdoi: 10.1016/j.mtla.2022.101343
  • 2022 • 341 AI-methods for the integration of structural design knowledge in early phases of the building design process [KI-Methoden zur Integration tragwerksplanerischen Wissens in frühe Phasen des Gebäudeentwurfsprozesses]
    Schnellenbach-Held, M. and Steiner, D.
    Bautechnik 99 191-198 (2022)
    AI-methods for the integration of structural design knowledge in early phases of the building design process. The early integration of the structural design expertise in the building planning process allows an efficient support of the involved highly complex decision-making. A knowledge-based system (KBS) is developed for the supply and the usage of suitable engineering experience knowledge. This performs an evaluation of bearing structures and the proposal of design options through the application of development level dependent fuzzy knowledge bases and related inference systems. The levels of development include the assessment of structures based on the possibility theory and comprises concepts of adaptive detailing. An imitation of the human decision-making behavior is achieved by the use of an easily understandable formulation of rules following the Modus Ponens and Fuzzy Logic inference mechanisms. Acquisition of applicable knowledge is based on parametric studies covering the calculation and design of structural elements that initially are carried out for reinforced concrete components. Considerable value ranges are determined based on practical experiences. Additionally, mechanisms for the consideration of uncertain parameters are provided. The resulting (KBS) system enables an efficiency increase in the early planning process. © 2022, Ernst und Sohn. All rights reserved.
    view abstractdoi: 10.1002/bate.202000090
  • 2022 • 340 Selective [2+1+1] Fragmentation of P4 by heteroleptic Metallasilylenes
    Schoening, J. and Gehlhaar, A. and Wölper, C. and Schulz, S.
    Chemistry - A European Journal 28 (2022)
    Small-molecule activation by low-valent main-group element compounds is of general interest. We here report the synthesis and characterization (1H, 13C, 29Si NMR, IR, sc-XRD) of heteroleptic metallasilylenes L1(Cl)MSiL2 (M=Al 1, Ga 2, L1=HC[C(Me)NDipp]2, Dipp=2,6-iPr2C6H3; L2=PhC(NtBu)2). Their electronic nature was analyzed by quantum chemical computations, while their promising potential in small-molecule activation was demonstrated in reactions with P4, which occurred with unprecedented [2+1+1] fragmentation of the P4 tetrahedron and formation of L1(Cl)MPSi(L2)PPSi(L2)PM(Cl)L1 (M=Al 3, Ga 4). © 2022 The Authors. Chemistry - A European Journal published by Wiley-VCH GmbH.
    view abstractdoi: 10.1002/chem.202201031
  • 2022 • 339 Synthesis, electronic nature, and reactivity of selected silylene carbonyl complexes
    Schoening, J. and Ganesamoorthy, C. and Wölper, C. and Solel, E. and Schreiner, P.R. and Schulz, S.
    Dalton Transactions 51 8249-8257 (2022)
    Room-temperature stable main group element carbonyl complexes are rare. Here we report on the synthesis of two such complexes, namely gallium-substituted silylene-carbonyl complexes [L(X)Ga]2SiCO (X = I 2, Me 3; L = HC[C(Me)NDipp]2, Dipp = 2,6-iPr2C6H3) by reaction of three equivalents of LGa with IDippSiI4 (IDipp = 1,3-bis(2,6-iPr2C6H3)-imidazol-2-ylidene) or by salt elimination from [L(Br)Ga]2SiCO with MeLi. Both silylene carbonyl complexes were spectroscopically characterized as well as with single crystal X-ray diffraction (sc-XRD), while their electronic nature and the specific influence of the Ga-substituents X was evaluated by quantum chemical computations. In addition, we report the oxidative addition reaction of [L(Br)Ga]2SiCO with NH3, yielding [L(Br)Ga]2Si(H)NH24, demonstrating the promising potential of such complexes for small molecule activation. © 2022 The Royal Society of Chemistry
    view abstractdoi: 10.1039/d2dt01335e
  • 2022 • 338 Small-Molecule Activation by Heteroleptic Metallasilylenes
    Schoening, J. and Wölper, C. and Schulz, S.
    European Journal of Inorganic Chemistry (2022)
    We report on reactions of heteroleptic metallasilylenes L1(Cl)MSiL2 (M=Al 1, Ga 2, L1=HC[C(Me)NDipp]2, Dipp=2,6-iPr2C6H3; L2=PhC(NtBu)2) with CO2, N2O, and Me3SiN3, yielding the corresponding carbonate complexes L1(Cl)MOSi(CO3-κ2O,O−)L2 (M=Al 3, Ga 4), silanoic esters L1(Cl)MOSi(O)L2 (M=Al 5, Ga 6), and silaimine L1(Cl)GaSi(NSiMe3)L2 (8), whereas {L2Si[N(SiMe3)Al(Cl)C(Me)NDipp][CHC(Me)N(Dipp)]} 7 was formed by C−C bond cleavage of the L1 ligand. Compounds 3–8 were characterized by NMR (1H, 13C) and IR spectroscopy, elemental analysis and single crystal X-ray diffraction. © 2022 The Authors. European Journal of Inorganic Chemistry published by Wiley-VCH GmbH.
    view abstractdoi: 10.1002/ejic.202200638
  • 2022 • 337 MECHANISM-BASED ASSESSMENT OF CELLULOSE-BASED BIOCOMPOSITE COTTONID FOR SUSTAINABLE CONSTRUCTION
    Scholz, R. and Walther, F.
    ECCM 2022 - Proceedings of the 20th European Conference on Composite Materials: Composites Meet Sustainability 1 616-623 (2022)
  • 2022 • 336 Fast Sampling of Synthetic Apertures in Short Range THz Imaging Using Travelling Salesman Approach
    Schorlemer, J. and Batra, A. and Kaiser, T. and Gohringer, D. and Rolfes, I. and Barowski, J.
    Asia-Pacific Microwave Conference Proceedings, APMC 2022-November 330-332 (2022)
  • 2022 • 335 A Statistical FDFD Simulator for the Generation of Labeled Training Data Sets in the Context of Humanitarian Demining using GPR
    Schorlemer, J. and Jebramcik, J. and Baer, C. and Rolfes, I. and Schulz, C.
    2022 IEEE MTT-S International Conference on Numerical Electromagnetic and Multiphysics Modeling and Optimization, NEMO 2022 (2022)
    doi: 10.1109/NEMO51452.2022.10038521
  • 2022 • 334 Cathepsin D as biomarker in cerebrospinal fluid of nusinersen-treated patients with spinal muscular atrophy
    Schorling, D.C. and Kölbel, H. and Hentschel, A. and Pechmann, A. and Meyer, N. and Wirth, B. and Rombo, R. and Sickmann, A. and Kirschner, J. and Schara-Schmidt, U. and Lochmüller, H. and Roos, A. and Abele, T.B. and Andres, B....
    European Journal of Neurology 29 2084-2096 (2022)
    Background and purpose: The therapeutic landscape of spinal muscular atrophy (SMA) has changed dramatically during the past 4 years, but treatment responses differ remarkably between individuals, and therapeutic decision-making remains challenging, underlining the persistent need for validated biomarkers. Methods: We applied untargeted proteomic analyses to determine biomarkers in cerebrospinal fluid (CSF) samples of SMA patients under treatment with nusinersen. Identified candidate proteins were validated in CSF samples of SMA patients by Western blot and enzyme-linked immunosorbent assay. Furthermore, levels of peripheral neurofilament heavy and light chain were determined. Results: Untargeted proteomic analysis of CSF samples of three SMA type 1 patients revealed the lysosomal protease cathepsin D as a candidate biomarker. Subsequent validation analysis in a larger cohort of 31 pediatric SMA patients (type 1, n = 12; type 2, n = 9; type 3, n = 6; presymptomatically treated, n = 4; age = 0–16 years) revealed a significant decline of cathepsin D levels in SMA patients aged ≥2 months at the start of treatment. Although evident in all older age categories, this decline was only significant in the group of patients who showed a positive motor response. Moreover, downregulation of cathepsin D was evident in muscle biopsies of SMA patients. Conclusions: We identified a decline of cathepsin D levels in CSF samples of SMA patients under nusinersen treatment that was more pronounced in the group of "treatment responders" than in "nonresponders." We believe that our results indicate a suitability of cathepsin D levels as a possible biomarker in SMA also in older patients, in combination with analysis of peripheral neurofilament light chain in adolescents or alone in adult patients. © 2022 The Authors. European Journal of Neurology published by John Wiley & Sons Ltd on behalf of European Academy of Neurology.
    view abstractdoi: 10.1111/ene.15331
  • 2022 • 333 Prediction of ductile damage evolution based on experimental data using artificial neural networks
    Schowtjak, A. and Gerlach, J. and Muhammad, W. and Brahme, A.P. and Clausmeyer, T. and Inal, K. and Tekkaya, A.E.
    International Journal of Solids and Structures 257 (2022)
    doi: 10.1016/j.ijsolstr.2022.111950
  • 2022 • 332 Short Review of EMB Systems Related to Safety Concepts
    Schrade, S. and Nowak, X. and Verhagen, A. and Schramm, D.
    Actuators 11 (2022)
    A growing interest in Electromechanical Brakes (EMBs) is discernible in the automotive industry. Nevertheless, no EMBs have ever been deployed for series production, although countless publications have been made, and patents have been filed. One reason for this is the need for the optimization of functional safety. Due to the missing mechanical/hydraulic link between the driver and the actuator, sophisticated concepts need to be elaborated upon. This paper presents the current state of the art of safety concepts for EMB systems (only publicly available publications are reviewed). An analysis of current regulatory and safety requirements is conducted to provide a base for design options. These design options are explored on the basis of an extensive patent and literature research. The various discovered designs are summarized and analyzed according to their (a) EMB actuators; (b) control topology; (c) energy supply; and (d) communication architecture. This paper concludes by revealing the weak points of the current systems. © 2022 by the authors.
    view abstractdoi: 10.3390/act11080214
  • 2022 • 331 Oxide ceramic electrolytes for all-solid-state lithium batteries - cost-cutting cell design and environmental impact
    Schreiber, A. and Rosen, M. and Waetzig, K. and Nikolowski, K. and Schiffmann, N. and Wiggers, H. and Küpers, M. and Fattakhova-Rohlfing, D. and Kuckshinrichs, W. and Guillon, O. and Finsterbusch, M.
    Green Chemistry 25 399-414 (2022)
    doi: 10.1039/d2gc03368b
  • 2022 • 330 An efficient numerical scheme for the FE-approximation of magnetic stray fields in infinite domains
    Schröder, J. and Reichel, M. and Birk, C.
    Computational Mechanics 70 141-153 (2022)
    doi: 10.1007/s00466-022-02162-1
  • 2022 • 329 Phase-field modeling of fracture in high performance concrete during low-cycle fatigue: Numerical calibration and experimental validation
    Schröder, J. and Pise, M. and Brands, D. and Gebuhr, G. and Anders, S.
    Computer Methods in Applied Mechanics and Engineering 398 (2022)
    doi: 10.1016/j.cma.2022.115181
  • 2022 • 328 Lagrange and H(curl , B) based finite element formulations for the relaxed micromorphic model
    Schröder, J. and Sarhil, M. and Scheunemann, L. and Neff, P.
    Computational Mechanics 70 1309-1333 (2022)
    Modeling the unusual mechanical properties of metamaterials is a challenging topic for the mechanics community and enriched continuum theories are promising computational tools for such materials. The so-called relaxed micromorphic model has shown many advantages in this field. In this contribution, we present significant aspects related to the relaxed micromorphic model realization with the finite element method (FEM). The variational problem is derived and different FEM-formulations for the two-dimensional case are presented. These are a nodal standard formulation H1(B) × H1(B) and a nodal-edge formulation H1(B) × H(curl , B) , where the latter employs the Nédélec space. In this framework, the implementation of higher-order Nédélec elements is not trivial and requires some technicalities which are demonstrated. We discuss the computational convergence behavior of Lagrange-type and tangential-conforming finite element discretizations. Moreover, we analyze the characteristic length effect on the different components of the model and reveal how the size-effect property is captured via this characteristic length parameter. © 2022, The Author(s).
    view abstractdoi: 10.1007/s00466-022-02198-3
  • 2022 • 327 Challenges for the Least-Squares Finite Element Method in Solid Mechanics
    Schröder, J. and Igelbüscher, M.
    Current Trends and Open Problems in Computational Mechanics 485-495 (2022)
    doi: 10.1007/978-3-030-87312-7_47
  • 2022 • 326 Novel Finite Elements - Mixed, Hybrid and Virtual Element Formulations at Finite Strains for 3D Applications
    Schröder, J. and Wriggers, P. and Kraus, A. and Viebahn, N.
    Lecture Notes in Applied and Computational Mechanics 98 37-67 (2022)
    The main goal of this research project is to develop new finite-element formulations as a suitable basis for the stable calculation of modern isotropic and anisotropic materials with a complex nonlinear material behavior. New ideas are pursued in a strict variational framework, based either on a mixed or virtual FE approach. A novel extension of the classical Hellinger-Reissner formulation to non-linear applications is developed. Herein, the constitutive relation of the interpolated stresses and strains is determined with help of an iterative procedure. The extension of the promising virtual finite element method (VEM) is part of the further investigation. Particularly, different stabilization methods are investigated in detail, needed in the framework of complex nonlinear constitutive behavior. Furthermore the interpolation functions for the VEM is extended from linear to quadratic functions to obtain better convergence rates. Especially in this application the flexibility of the VEM regarding the mesh generation will constitute a huge benefit. As a common software development platform the AceGen environment is applied providing a flexible tool for the generation of efficient finite element code. © 2022, The Author(s), under exclusive license to Springer Nature Switzerland AG.
    view abstractdoi: 10.1007/978-3-030-92672-4_2
  • 2022 • 325 Preface
    Schröder, J. and Wriggers, P.
    Lecture Notes in Applied and Computational Mechanics 98 v-vi (2022)
  • 2022 • 324 Tuning the magnetic phase diagram of Ni-Mn-Ga by Cr and Co substitution
    Schröter, M. and Herper, H.C. and Grünebohm, A.
    Journal of Physics D: Applied Physics 55 (2022)
    Ni-Mn-based Heusler alloys have a high technical potential related to a large change of magnetization at the structural phase transition. These alloys show a subtle dependence of magnetic properties and structural phase stability on composition and substitution by 3d elements and although they have been extensively investigated, there are still ambiguities in the published results and their interpretation. To shed light on the large spread of reported properties, we perform a comprehensive study by means of density functional theory calculations. We focus on Cr and Co co-substitution whose benefit has been predicted previously for the expensive Ni-Mn-In-based alloy and study the more abundant iso-electronic counterpart Ni-Mn-Ga. We observe that substituting Ni partially by Co and/or Cr enhances the magnetization of the Heusler alloy and at the same time reduces the structural transition temperature. Thereby, Cr turns out to be more efficient to stabilize the ferromagnetic alignment of the Mn spins by strong antiferromagnetic interactions between Mn and Cr atoms. In a second step, we study Cr on the other sublattices and observe that an increase in the structural transition temperature is possible, but depends critically on the short-range order of Mn and Cr atoms. Based on our results, we are able to estimate composition dependent magnetic phase diagrams. In particular, we demonstrate that neither the atomic configuration with the lowest energy nor the results based on the coherent potential approximation are representative for materials with a homogeneous distribution of atoms and we also predict a simple method for fast screening of different concentrations which can be viewed as a blueprint for the study of high entropy alloys. Our results help to explain the large variation of experimentally found materials properties. © 2021 The Author(s). Published by IOP Publishing Ltd.
    view abstractdoi: 10.1088/1361-6463/ac2a66
  • 2022 • 323 Optical absorption spectroscopy of reactive oxygen and nitrogen species in a surface dielectric barrier discharge
    Schücke, L. and Bodnar, A. and Friedrichs, N. and Böddecker, A. and Peters, N. and Ollegott, K. and Oberste-Beulmann, C. and Wirth, P. and Nguyen-Smith, R.T. and Korolov, I. and Gibson, A.R. and Muhler, M. and Awakowicz, P.
    Journal of Physics D: Applied Physics 55 (2022)
    A twin surface dielectric barrier discharge (SDBD) ignited in a dry synthetic air gas stream is studied regarding the formation of reactive oxygen and nitrogen species (RONS) and their impact on the conversion of admixed n-butane. The discharge is driven by a damped sinusoidal voltage waveform at peak-to-peak amplitudes of 8 kVpp-13 kVpp and pulse repetition frequencies of 250 Hz-4000 Hz. Absolute densities of O3, NO2, NO3, as well as estimates of the sum of the densities of N2O4 and N2O5 are determined temporally resolved by means of optical absorption spectroscopy using a laser driven broadband light source, suitable interference filters, and a photodiode detector. The measured densities are acquired across the center of the reactor chamber as well as at the outlet of the chamber. The temporal and spatial evolution of the species' densities is correlated to the conversion of n-butane at concentrations of 50 ppm and 400 ppm, measured by means of flame ionization detectors. The n-butane is admixed either before or after the reactor chamber, in order to separate the impact of short- and long-lived reactive species on the conversion process. It is found that, despite the stationary conversion at the selected operating points, at higher voltages and repetition frequencies the densities of the measured species are not in steady state. Based on the produced results it is presumed that the presence of n-butane modifies the formation and consumption pathways of O3. At the same time, there is no significant impact on the formation of dinitrogen oxides (N2O4 and N2O5). Furthermore, a comparatively high conversion of n-butane, when admixed at the outlet of the reactor chamber is observed. These findings are discussed together with known rate coefficients for the reactions of n-butane with selected RONS. © 2022 The Author(s). Published by IOP Publishing Ltd
    view abstractdoi: 10.1088/1361-6463/ac5661
  • 2022 • 322 Effects of Microstructure Modification by Friction Surfacing on Wear Behavior of Al Alloys with Different Si Contents
    Schütte, M.R. and Ehrich, J. and Linsler, D. and Hanke, S.
    Materials 15 (2022)
    In this work, Al alloys with 6.6%, 10.4%, and 14.6% Si were deposited as thick coatings by Friction Surfacing (FS), resulting in grain refinement and spheroidization of needle-shaped eutectic Si phase. Lubricated sliding wear tests were performed on a pin-on-disc tribometer using Al-Si alloys in as-cast and FS processed states as pins and 42CrMo4 steel discs. The chemical composition of the worn surfaces was analyzed by X-ray photoelectron spectroscopy (XPS). The wear mechanisms were studied by scanning electron microscopy (SEM) and focused ion beam (FIB), and the wear was evaluated by measuring the weight loss of the samples. For the hypoeutectic alloys, spheroidization of the Si phase particles in particular leads to a significant improvement in wear resistance. The needle-shaped Si phase in as-cast state fractures during the wear test and small fragments easily detach from the surface. The spherical Si phase particles in the FS state also break away from the surface, but to a smaller extent. No reduction in wear due to FS was observed for the hypereutectic alloy. Here, large bulky primary Si phase particles are already present in the as-cast state and do not change significantly during FS, providing high wear resistance in both material states. This study highlights the mechanisms and limitations of improved wear resistance of Si-rich Al alloys deposited as thick coatings by Friction Surfacing. © 2022 by the authors. Licensee MDPI, Basel, Switzerland.
    view abstractdoi: 10.3390/ma15051641
  • 2022 • 321 Group 15/16 single-source precursors for energy materials
    Schulz, S.
    Nanomaterials via Single-Source Precursors: Synthesis, Processing and Applications 313-356 (2022)
    Group 15/16 compounds of the heaviest elements of both groups (Sb, Bi; Se, Te) containing at least one direct (polar-covalent) element-element bond are capable to serve as single-source precursors for the synthesis of the corresponding tetradymite-type layered materials Sb2E3 and Bi2E3 (E = Se, Te). These materials are of intense interest for technical applications in thermoelectric devices and represent prototypes of the so-called topological insulators. We herein summarize synthesis and solid-state structures of such compounds and their use in materials synthesis. Nanoparticles are typically formed in solution-based processes, whereas gas-phase processes such as metal organic chemical vapor deposition are used to produce thin (epitaxial) films. © 2022 Elsevier Inc. All rights reserved.
    view abstractdoi: 10.1016/B978-0-12-820340-8.00010-1
  • 2022 • 320 Production and Subsequent Forming of Chip-Based Aluminium Sheets Without Remelting
    Schulze, A. and Hering, O. and Tekkaya, A.E.
    International Journal of Precision Engineering and Manufacturing - Green Technology 9 1035-1048 (2022)
    Bent components and deep drawn cups are produced by direct usage of aluminium chips without melting following a new process chain: hot extrusion of aluminium chips to a cylindrical open profile, flattening, subsequent rolling and bending or deep drawing. The properties of the hot extruded chip-based AA6060 sheets are examined by tensile tests and microstructural investigations and the results are compared with those obtained from material extruded from conventional cast billets. The chip-based sheets were used to form components by bending or deep drawing. No significant differences between the bent components or deep-drawn cups made of chips and those from cast material are observed regarding their capability for further plastic forming operations. This makes the new process route a resource-efficient alternative for the production of aluminium sheet products. © 2021, The Author(s).
    view abstractdoi: 10.1007/s40684-021-00395-8
  • 2022 • 319 Revealing the Heterogeneity of Large-Area MoS2 Layers in the Electrocatalytic Hydrogen Evolution Reaction
    Schumacher, S. and Madauß, L. and Liebsch, Y. and Tetteh, E.B. and Varhade, S. and Schuhmann, W. and Schleberger, M. and Andronescu, C.
    ChemElectroChem 9 (2022)
    doi: 10.1002/celc.202200586
  • 2022 • 318 High-throughput discovery of hydrogen evolution electrocatalysts in the complex solid solution system Co-Cr-Fe-Mo-Ni
    Schumacher, S. and Baha, S. and Savan, A. and Andronescu, C. and Ludwig, A.
    Journal of Materials Chemistry A (2022)
    doi: 10.1039/d2ta01652d
  • 2022 • 317 Halogen and structure sensitivity of halobenzene adsorption on copper surfaces
    Schunke, C. and Miller, D.P. and Zurek, E. and Morgenstern, K.
    Physical Chemistry Chemical Physics 24 4485-4492 (2022)
    The adsorption orientation of molecules on surfaces influences their reactivity, but it is still challenging to tailor the interactions that govern their orientation. Here, we investigate how the substituent and the surface structure alter the adsorption orientation of halogenated benzene molecules from parallel to tilted relative to the surface plane. The deviation of the parallel orientation of bromo-, chloro-, and fluorobenzene molecules adsorbed on Cu(111) and Cu(110) surfaces is determined, utilising the surface selection rule in reflection-absorption infrared spectroscopy. On Cu(111), all three halogenated molecules are adsorbed with their molecular plane almost parallel to the surface at low coverages. However, they are tilted at higher coverages; yet, the threshold coverages differ. On Cu(110), merely bromo- and chlorobenzene follow this trend, albeit with a lower threshold for both. In contrast, fluorobenzene molecules are tilted already at low coverages. The substantial influence of the halogen atom and the surface structure on the adsorption orientation, resulting from an interplay of molecule-molecule and molecule-surface interactions, is highly relevant for reactivity confined to two dimensions. © 2022 the Owner Societies.
    view abstractdoi: 10.1039/d1cp05660c
  • 2022 • 316 Short-Term Heat Treatment of the High-Alloy Cold-Work Tool Steel X153CrMoV12: Calculation of Metastable Microstructural States
    Schuppener, J. and Müller, S. and Benito, S. and Weber, S.
    Steel Research International (2022)
    The influence of short-time heat treatment on the widely used and commercially available ledeburitic cold-work tool steel 1.2379 (X153CrMoV12; AISI D2) is examined herein. Starting from a soft annealed initial condition, the influence of different austenitizing temperatures and holding times on the metastable microstructural states after heat treatment/hardening is investigated. The experimental implementation of the heat treatment is used in a quenching dilatometer, and a microstructural simulation model is built using these results. As validation of the model, on the one hand, the martensite start temperature (Ms) is used, measured experimentally by dilatometry. Additionally, the carbide content and distribution, as determined by quantitative image analysis, are compared with the simulated data and used as an indicator of the model accuracy. Through the developed simulation model, arbitrary heat treatment-induced metastable microstructural states can be calculated. As a possible application of this model, the live-adaption of the industrial heat treatment process in dependence on the batch chemical composition is discussed. © 2022 The Authors. Steel Research International published by Wiley-VCH GmbH.
    view abstractdoi: 10.1002/srin.202200452
  • 2022 • 315 Impact of cobalt content and grain growth inhibitors in laser-based powder bed fusion of WC-Co
    Schwanekamp, T. and Marginean, G. and Reuber, M. and Ostendorf, A.
    International Journal of Refractory Metals and Hard Materials 105 (2022)
    Processing of tungsten carbide‑cobalt (WC-Co) by laser-based powder bed fusion (PBF-LB) can result in characteristic microstructure defects such as cracks, pores, undesired phases and tungsten carbide (WC) grain growth, due to the heterogeneous energy input and the high thermal gradients. Besides the processing conditions, the material properties are affected by the initial powder characteristics. In this paper, the impact of powder composition on microstructure, phase formation and mechanical properties in PBF-LB of WC-Co is studied. Powders with different cobalt contents from 12 wt.-% to 25 wt.-% are tested under variation of the laser parameters. Furthermore, the impact of vanadium carbide (VC) and chromium (Cr) additives is investigated. Both are known as grain growth inhibitors for conventional sintering processes. The experiments are conducted at a pre-heating temperature of around 800 °C to prevent crack formation in the samples. Increasing laser energy input reduces porosity but leads to severe embrittlement for low cobalt content and to abnormal WC grain growth for high cobalt content. It is found that interparticular porosity at low laser energy is more severe for low cobalt content due to poor wetting of the liquid phase. Maximum bending strength of σB &gt; 1200 MPa and Vickers hardness of approx. 1000 HV3 can be measured for samples generated from WC-Co 83/17 powder with medium laser energy input. The addition of V and Cr leads to increased formation of additional phases such as Co3W3C, Co3V and Cr23C6 and to increased lateral and multi-laminar growth of the WC grains. In contrast to conventional sintering, a grain growth inhibiting effect of V and Cr in the laser molten microstructure is not achieved. © 2022 Elsevier Ltd
    view abstractdoi: 10.1016/j.ijrmhm.2022.105814
  • 2022 • 314 Reduction of biofilm accumulation by constant and alternating potentials in static and dynamic field experiments
    Schwarze, J. and Koc, J. and Koschitzki, F. and Gardner, H. and Hunsucker, K.Z. and Swain, G.W. and Rosenhahn, A.
    Biofouling (2022)
    The application of electric fields to conductive coatings is an environmentally friendly way to reduce biofilm formation. In particular alternating potentials (APs) have received increasing attention in recent studies. Here, an electrochemical rotating disk setup for dynamic field exposure experiments was developed to study how APs alter the attachment of fouling organisms in a multispecies ocean environment. A specific focus of the device design was proper integration of the potentiostat in the strongly corroding saltwater environment. The effect of APs on the accumulation of fouling organisms in short term field exposures was studied. Potentials on conductive gold surfaces were periodically switched between −0.3 V and 0.3 V or between −0.8 V and 0.6 V at a frequency of 0.5 Hz. APs were capable of significantly reducing the attachment of marine fouling organisms compared with the conductive samples immersed at open circuit potentials. © 2022 Informa UK Limited, trading as Taylor & Francis Group.
    view abstractdoi: 10.1080/08927014.2022.2027923
  • 2022 • 313 Probing the methanol-assisted autocatalytic formation of methanol over Cu/ZnO/Al2O3 by high-pressure methanol and methyl formate pulses
    Schwiderowski, P. and Stürmer, S. and Muhler, M.
    Reaction Chemistry and Engineering 7 2224-2230 (2022)
    Using high-pressure methanol and methyl formate pulses as a surface-sensitive operando method for high-pressure methanol synthesis over Cu/ZnO/Al2O3, the recently found autocatalytic pathway was confirmed. The autocatalytic effect is assumed to result from the faster hydrogenation of the formed methyl formate ester at high methoxy coverages compared with the rate-determining hydrogenation of formate to dioxomethylene. When pulsing increasing amounts of methanol at 60 bar and 210 °C under kinetically controlled conditions in 13.5 vol% CO, 3.5 vol% CO2, and 73.5 vol% H2, higher amounts of methanol were observed in response. The surplus of formed methanol was found to increase exponentially as a function of the dosed amount of methanol and the applied residence time. To further investigate the methanol-assisted autocatalytic pathway, methyl formate as the predicted intermediate was pulsed, which was rapidly converted into methanol. Instead of the expected 2 : 1 stoichiometry of methanol : methyl formate, only one methanol molecule was produced per dosed methyl formate molecule. It is concluded that methyl formate is split into methoxy and formate species by dissociative adsorption, but only methoxy species are rapidly further hydrogenated to desorbing methanol, whereas formate hydrogenation to methanol is too slow on the time scale of the pulse experiments. © 2022 The Royal Society of Chemistry.
    view abstractdoi: 10.1039/d2re00185c
  • 2022 • 312 Current developments in CO2 hydrogenation towards methanol: A review related to industrial application
    Schwiderowski, P. and Ruland, H. and Muhler, M.
    Current Opinion in Green and Sustainable Chemistry 38 (2022)
    doi: 10.1016/j.cogsc.2022.100688
  • 2022 • 311 Dynamic cryo-mechanical properties of additively manufactured nanocrystalline nickel 3D microarchitectures
    Schwiedrzik, J. and Ramachandramoorthy, R. and Edwards, T.E.J. and Schürch, P. and Casari, D. and Duarte, M.J. and Mohanty, G. and Dehm, G. and Maeder, X. and Philippe, L. and Breguet, J.-M. and Michler, J.
    Materials and Design 220 (2022)
    doi: 10.1016/j.matdes.2022.110836
  • 2022 • 310 Strain stiffening of Ndc80 complexes attached to microtubule plus ends
    Schwietert, F. and Volkov, V.A. and Huis in ’t Veld, P.J. and Dogterom, M. and Musacchio, A. and Kierfeld, J.
    Biophysical Journal 121 4048-4062 (2022)
    In the mitotic spindle, microtubules attach to chromosomes via kinetochores. The microtubule-binding Ndc80 complex is an integral part of kinetochores, and is essential for kinetochores to attach to microtubules and to transmit forces from dynamic microtubule ends to the chromosomes. The Ndc80 complex has a rod-like appearance with globular domains at its ends that are separated by a long coiled coil. Its mechanical properties are considered important for the dynamic interaction between kinetochores and microtubules. Here, we present a novel method that allows us to time trace the effective stiffness of Ndc80 complexes following shortening microtubule ends against applied force in optical trap experiments. Applying this method to wild-type Ndc80 and three variants (calponin homology (CH) domains mutated or Hec1 tail unphosphorylated, phosphorylated, or truncated), we reveal that each variant exhibits strain stiffening; i.e., the effective stiffness increases under tension that is built up by a depolymerizing microtubule. The strain stiffening relation is roughly linear and independent of the state of the microtubule. We introduce structure-based models that show that the strain stiffening can be traced back to the specific architecture of the Ndc80 complex with a characteristic flexible kink, to thermal fluctuations of the microtubule, and to the bending elasticity of flaring protofilaments, which exert force to move the Ndc80 complexes. Our model accounts for changes in the amount of load-bearing attachments at various force levels and reproduces the roughly linear strain stiffening behavior, highlighting the importance of force-dependent binding affinity. © 2022 Biophysical Society
    view abstractdoi: 10.1016/j.bpj.2022.09.039
  • 2022 • 309 Evolution of Artificial Arginine Analogues—Fluorescent Guanidiniocarbonyl-Indoles as Efficient Oxo-Anion Binders
    Sebena, D. and Rudolph, K. and Roy, B. and Wölper, C. and Nitschke, T. and Lampe, S. and Giese, M. and Voskuhl, J.
    Molecules 27 (2022)
    doi: 10.3390/molecules27093005
  • 2022 • 308 Determination and analysis of the constitutive parameters of temperature-dependent dislocation-density-based crystal plasticity models
    Sedighiani, K. and Traka, K. and Roters, F. and Raabe, D. and Sietsma, J. and Diehl, M.
    Mechanics of Materials 164 (2022)
    Physics-based crystal plasticity models rely on certain statistical assumptions about the collective behavior of dislocation populations on one slip system and their interactions with the dislocations on the other slip systems. One main advantage of using such physics-based constitutive dislocation models in crystal plasticity kinematic frameworks is their suitability for predicting the mechanical behavior of polycrystals over a wide range of deformation temperatures and strain rates with the same physics-based parameter set. In this study, the ability of a widely used temperature-dependent dislocation-density-based crystal plasticity formulation to reproduce experimental results, with a main focus on the yield stress behavior, is investigated. First, the material parameters are identified from experimental macroscopic stress–strain curves using a computationally efficient optimization methodology that uses a genetic algorithm along with the response surface methodology. For this purpose, a systematic set of compression tests on interstitial free (IF) steel samples is performed at various temperatures and strain rates. Next, the influence of the individual parameters on the observed behavior is analyzed. Based on mutual interactions between various parameters, the ability to find a unique parameter set is discussed. This allows identifying shortcomings of the constitutive law and sketch ideas for possible improvements. Particular attention is directed toward identifying possibly redundant material parameters, narrowing the acceptable range of material parameters based on physical criteria, and modifying the crystal plasticity formulation numerically for high-temperature use. © 2021 The Author(s)
    view abstractdoi: 10.1016/j.mechmat.2021.104117
  • 2022 • 307 Crystal plasticity simulation of in-grain microstructural evolution during large deformation of IF-steel
    Sedighiani, K. and Traka, K. and Roters, F. and Sietsma, J. and Raabe, D. and Diehl, M.
    Acta Materialia 237 (2022)
    High-resolution three-dimensional crystal plasticity simulations are used to investigate deformation heterogeneity and microstructure evolution during cold rolling of interstitial free (IF-) steel. A Fast Fourier Transform (FFT)-based spectral solver is used to conduct crystal plasticity simulations using a dislocation-density-based crystal plasticity model. The in-grain texture evolution and misorientation spread are consistent with experimental results obtained using electron backscatter diffraction (EBSD) experiments. The crystal plasticity simulations show that two types of strain localization features develop during the large strain deformation of IF-steel. The first type forms band-like areas with large strain accumulation that appear as river patterns extending across the specimen. In addition to these river-like patterns, a second type of strain localization with rather sharp and highly localized in-grain shear bands is identified. These localized features are dependent on the crystallographic orientation of the grain and extend within a single grain. In addition to the strain localization, the evolution of in-grain orientation gradients, misorientation features, dislocation density, kernel average misorientation, and stress in major texture components are discussed. © 2022 The Author(s)
    view abstractdoi: 10.1016/j.actamat.2022.118167
  • 2022 • 306 On the influence of the amorphous phase on the stability of crystals in poly(cis-1,4-isoprene) networks
    Segiet, D. and Weckes, S. and Austermuehl, J. and Tiller, J.C. and Katzenberg, F.
    Journal of Applied Polymer Science 139 (2022)
    Crosslinked natural rubber and synthetic rubber samples are additivated with up to 9 wt% stearic acid (StA) to better understand the influence of StA on the melting temperature Tm of strain-induced crystallized poly(cis-1,4-isoprene) crystals. To this end, lamellae thicknesses are determined from wide-angle x-ray patterns and used to calculate the crystal size dependent melting temperature Tm,calc. Comparing the measured Tm with Tm,calc reveals that Tm deviates downward from Tm,calc and converges Tm,calc with increasing StA concentration until it is identical to Tm,calc, in case of room temperature strain-induced crystallization. In case of strain-induced crystallization at 80°C, it was found that Tm is identical with Tm,calc without added StA and deviates upward from Tm,calc with increasing amount of added StA. We suggest that this is due to internal stress onto the polymer crystals exerted by highly strained macromolecules in the surrounding amorphous phase. Whether this stress has a stabilizing or destabilizing effect on the crystals is assumed to depend on its intensity and direction, which can be efficiently altered by the amount and the location of StA crystals in the amorphous phase. © 2022 The Authors. Journal of Applied Polymer Science published by Wiley Periodicals LLC.
    view abstractdoi: 10.1002/app.53146
  • 2022 • 305 Enzymatic synthesis of novel aromatic-aliphatic polyesters with increased hydroxyl group density
    Seithümmer, J. and Öztürk, M. and Wunschik, D.S. and Prießen, J. and Schultz, H.J. and Dornbusch, M. and Gutmann, J.S. and Hoffmann-Jacobsen, K.
    Biotechnology Journal 17 (2022)
    doi: 10.1002/biot.202100452
  • 2022 • 304 Comparison of 5- and 6-membered cyclic carbonate-polyisocyanate adducts for high performance coatings
    Seithümmer, J. and Knospe, P. and Reichmann, R. and Gutmann, J.S. and Hoffmann-Jacobsen, K. and Dornbusch, M.
    Journal of Coatings Technology and Research (2022)
    doi: 10.1007/s11998-022-00665-3
  • 2022 • 303 LES of nanoparticle synthesis in the spraysyn burner: A comparison against experiments
    Sellmann, J. and Wollny, P. and Baik, S.-J. and Suleiman, S. and Schneider, F. and Schulz, C. and Wiggers, H. and Wlokas, I. and Kempf, A.M.
    Powder Technology 404 (2022)
    The synthesis of iron oxide nanoparticles from iron nitrate in the SpraySyn spray flame reactor was investigated by experiment and simulation. The focus was on the spray and flame structure, the particle growth by nucleation and coagulation, and the unresolved effects and their impact on the dispersed phase. The reacting flow was modeled in large eddy simulations with the premixed flamelet generated manifolds technique, including modifications for aerosol nucleation. Particle dynamics were described with a sectional model and a subgrid scale coagulation kernel. The particle size distributions at different distances from the burner surface were obtained using a particle mass spectrometer. The experiments and simulations are in good agreement for the flame centreline velocity and both size distribution and mean size of the particles (for particles larger 1 nm - the approximate detection limit of the experiment). Furthermore, simulations enabled to interpret the temporal evolution of the particle size distribution. © 2022 Elsevier B.V.
    view abstractdoi: 10.1016/j.powtec.2022.117466
  • 2022 • 302 Trapping an Oxidized and Protonated Intermediate of the [FeFe]-Hydrogenase Cofactor under Mildly Reducing Conditions
    Senger, M. and Duan, J. and Pavliuk, M.V. and Apfel, U.-P. and Haumann, M. and Stripp, S.T.
    Inorganic Chemistry 61 10036-10042 (2022)
    doi: 10.1021/acs.inorgchem.2c00954
  • 2022 • 301 The effect of buoyancy driven convection on the growth and dissolution of bubbles on electrodes
    Sepahi, F. and Pande, N. and Chong, K.L. and Mul, G. and Verzicco, R. and Lohse, D. and Mei, B.T. and Krug, D.
    Electrochimica Acta 403 (2022)
    Enhancing the efficiency of water electrolysis, which can be severely impacted by the nucleation and growth of bubbles, is key in the energy transition. In this combined experimental and numerical study, in-situ bubble evolution and dissolution processes are imaged and compared to numerical simulations employing the immersed boundary method. We find that it is crucial to include solutal driven natural convection in order to represent the experimentally observed bubble behaviour even though such effects have commonly been neglected in modelling efforts so far. We reveal how the convective patterns depend on current densities and bubble spacings, leading to distinctively different bubble growth and shrinkage dynamics. Bubbles are seen to promote the convective instability if their spacing is large (≥4 mm for the present conditions), whereas the onset of convection is delayed if the inter-bubble distance is smaller. Our approach and our results can help devise efficient mass transfer solutions for gas evolving electrodes. © 2021 The Authors
    view abstractdoi: 10.1016/j.electacta.2021.139616
  • 2022 • 300 Non-uniform He bubble formation in W/W2C composite: Experimental and ab-initio study
    Šestan, A. and Sreekala, L. and Markelj, S. and Kelemen, M. and Zavašnik, J. and Liebscher, C.H. and Dehm, G. and Hickel, T. and Čeh, M. and Novak, S. and Jenuš, P.
    Acta Materialia 226 (2022)
    Tungsten-tungsten carbide (W/W2C) composites are considered as possible structural materials for future nuclear fusion reactors. Here, we report on the effect of helium (He) implantation on microstructure evolution of polycrystalline W/W2C composite consolidated by field-assisted sintering technique (FAST), homogenously implanted at room temperature with 1 MeV 4He+ ions at the fluence of 8 × 1016 ions cm−2 and annealed at 1873 K for 20 minutes. Samples were analysed by scanning and transmission electron microscopy to study the presence and size of He bubbles. Monomodal He bubbles in W (30-80 nm) are limited to point defects and grain boundaries, with a considerable void denuded zone (150 nm). Bubbles do not form in W2C, but at the W|W2C interface and are considerably larger (200-400 nm). The experimental observations on He behaviour and migration in W and W2C were assessed by density functional theory (DFT) calculations, suggesting He migration and accumulation in the composite are determined by the effective He-He binding in clusters, which will give rise to decohesion. In the presence of He clusters, the decohesion of bulk W into free surfaces is energetically highly favourable but not sufficient in the W2C; hence bubbles are only observed in W grains and interfaces and not within bulk W2C. © 2022
    view abstractdoi: 10.1016/j.actamat.2021.117608
  • 2022 • 299 Magnetic Resonance Imaging–based biomechanical simulation of cartilage: A systematic review
    Seyedpour, S.M. and Nafisi, S. and Nabati, M. and Pierce, D.M. and Reichenbach, J.R. and Ricken, T.
    Journal of the Mechanical Behavior of Biomedical Materials 126 (2022)
    MRI-based mathematical and computational modeling studies can contribute to a better understanding of the mechanisms governing cartilage's mechanical performance and cartilage disease. In addition, distinct modeling of cartilage is needed to optimize artificial cartilage production. These studies have opened up the prospect of further deepening our understanding of cartilage function. Furthermore, these studies reveal the initiation of an engineering-level approach to how cartilage disease affects material properties and cartilage function. Aimed at researchers in the field of MRI-based cartilage simulation, research articles pertinent to MRI-based cartilage modeling were identified, reviewed, and summarized systematically. Various MRI applications for cartilage modeling are highlighted, and the limitations of different constitutive models used are addressed. In addition, the clinical application of simulations and studied diseases are discussed. The paper's quality, based on the developed questionnaire, was assessed, and out of 79 reviewed papers, 34 papers were determined as high-quality. Due to the lack of the best constitutive models for various clinical conditions, researchers may consider the effect of constitutive material models on the cartilage disease simulation. In the future, research groups may incorporate various aspects of machine learning into constitutive models and MRI data extraction to further refine the study methodology. Moreover, researchers should strive for further reproducibility and rigorous model validation and verification, such as gait analysis. © 2021
    view abstractdoi: 10.1016/j.jmbbm.2021.104963
  • 2022 • 298 Coulomb blockade: Toward charge control of self-assembled GaN quantum dots at room temperature
    Sgroi, C.A. and Brault, J. and Duboz, J.-Y. and Chenot, S. and Vennéguès, P. and Ludwig, Ar. and Wieck, A.D.
    Applied Physics Letters 120 (2022)
    We present capacitance-voltage [C(V)] measurements of self-assembled wurtzite-GaN quantum dots (QDs). The QDs are embedded in a charge-tunable diode structure and were grown by molecular beam epitaxy in the Stranski-Krastanov growth method. The internal electric fields present in GaN and its alloys together with its wide bandgap make this material system an ideal candidate for high-temperature quantum applications. Charges and the internal electric fields influence the energy spacing in the QDs. We correlate photoluminescence measurements with C(V) measurements and show single-electron charging of the QDs and a Coulomb blockade energy of around 60 meV at room temperature. This finding demonstrates the possibility of quantum applications at room temperature. © 2022 Author(s).
    view abstractdoi: 10.1063/5.0073864
  • 2022 • 297 Integration of GaAs waveguides on a silicon substrate for quantum photonic circuits
    Shadmani, A. and Thomas, R.A. and Liu, Z. and Papon, C. and Heck, M.J.R. and Volet, N. and Scholz, S. and Wieck, A.D. and Ludwig, Ar. and Lodahl, P. and Midolo, L.
    Optics Express 30 37595-37602 (2022)
    We report a method for integrating GaAs waveguide circuits containing self-assembled quantum dots on a Si/SiO2 wafer, using die-to-wafer bonding. The large refractive-index contrast between GaAs and SiO2 enables fabricating single-mode waveguides without compromising the photon-emitter coupling. Anti-bunched emission from individual quantum dots is observed, along with a waveguide propagation loss &lt;7 dB/mm, which is comparable with the performance of suspended GaAs circuits. These results enable the integration of quantum emitters with different material platforms, towards the realization of scalable quantum photonic integrated circuits. © 2022 Optica Publishing Group under the terms of the Optica Open Access Publishing Agreement.
    view abstractdoi: 10.1364/OE.467920
  • 2022 • 296 Integration of GaAs waveguides with quantum dots on Silicon substrates for quantum photonic circuits
    Shadmani, A. and Thomas, R. and Liu, Z. and Volet, N. and Heck, M.J.R. and Scholz, S. and Wieck, A.D. and Ludwig, Ar. and Lodahl, P. and Midolo, L.
    2022 Conference on Lasers and Electro-Optics, CLEO 2022 - Proceedings (2022)
    We present the heterogeneous integration of GaAs membranes with embedded quantum dots on a Silicon substrate, based on die-to-die bonding method. We demonstrate light transmission in GaAs nanobeam waveguides and emission from individual quantum emitters. © Optica Publishing Group 2022, © 2022 The Author(s)
    view abstract
  • 2022 • 295 Spin dynamics of charged excitons in ultrathin (In,Al)(Sb,As)/AlAs and Al(Sb,As)/AlAs quantum wells with an indirect band gap
    Shamirzaev, T.S. and Yakovlev, D.R. and Kopteva, N.E. and Kudlacik, D. and Glazov, M.M. and Krechetov, A.G. and Gutakovskii, A.K. and Bayer, M.
    Physical Review B 106 (2022)
    doi: 10.1103/PhysRevB.106.075407
  • 2022 • 294 Fully-resolved simulations of volatile combustion and NOx formation from single coal particles in recycled flue gas environments
    Shamooni, A. and Stein, O.T. and Kronenburg, A. and Kempf, A.M. and Debiagi, P. and Li, T. and Dreizler, A. and Böhm, B. and Hasse, C.
    Proceedings of the Combustion Institute (2022)
    The interaction of coal particles and recycled/recirculated flue gas (RFG) with elevated temperatures and low levels of oxygen occurs in various pulverised coal combustion scenarios. In this work, the effect of oxygen level and temperature on single coal particle combustion characteristics and NOx formation in N2 diluent is studied by means of fully-resolved particle simulations. Comprehensive gas-phase kinetics are utilised to consider the critical pathways of NOx formation including tar-N. Results show that higher RFG temperatures decrease the time to reach the peaks of temperature and species profiles and increase the corresponding peak values. When decreasing O2 , irrespective of the RFG temperature, the fuel release period is prolonged, the volatile combustion time increases and the combustion process becomes overall less intense. The reduction of O2 in RFG results in a significant decrease of NO production, while the reduction of the RFG temperature has a smaller effect. The analysis of the key reactions that contribute to NO production in the region around stoichiometry shows that fuel-NOx is the major contributor. Both NH3 and HCN in fuel-N play a major role, while tar-N only contributes in the case with the lowest temperature and O2 concentration. The classical NOx formation pathways are negligible and the initiation reaction of the Zeldovich mechanism is even reversed, i.e. NO→+N N2 is dominantandcontributestoNO destruction. The destructionof NO mainlyoccursinarich region close to the particle surface where abundant tar species and their derivatives play a major role for NO destruction via the re-burn mechanism. The prompt mechanism is also active in this region and eventually contributes to NO reduction via production of HCN which is the feed to the re-burn mechanism. © 2022 The Author(s). Published by Elsevier Inc.
    view abstractdoi: 10.1016/j.proci.2022.07.034
  • 2022 • 293 High-dimensional neural network potentials for accurate vibrational frequencies: the formic acid dimer benchmark
    Shanavas Rasheeda, D. and Martín Santa Daría, A. and Schröder, B. and Mátyus, E. and Behler, J.
    Physical Chemistry Chemical Physics 24 29381-29392 (2022)
    In recent years, machine learning potentials (MLP) for atomistic simulations have attracted a lot of attention in chemistry and materials science. Many new approaches have been developed with the primary aim to transfer the accuracy of electronic structure calculations to large condensed systems containing thousands of atoms. In spite of these advances, the reliability of modern MLPs in reproducing the subtle details of the multi-dimensional potential-energy surface is still difficult to assess for such systems. On the other hand, moderately sized systems enabling the application of tools for thorough and systematic quality-control are nowadays rarely investigated. In this work we use benchmark-quality harmonic and anharmonic vibrational frequencies as a sensitive probe for the validation of high-dimensional neural network potentials. For the case of the formic acid dimer, a frequently studied model system for which stringent spectroscopic data became recently available, we show that high-quality frequencies can be obtained from state-of-the-art calculations in excellent agreement with coupled cluster theory and experimental data. © 2022 The Royal Society of Chemistry.
    view abstractdoi: 10.1039/d2cp03893e
  • 2022 • 292 Experimental Investigation of the Pressure Dependence of Iso-Octane Combustion
    Shaqiri, S. and Kaczmarek, D. and vom Lehn, F. and Beeckmann, J. and Pitsch, H. and Kasper, T.
    Frontiers in Energy Research 10 (2022)
    Iso-octane is frequently used as a surrogate fuel or as a component in primary reference fuel blends when low-temperature combustion strategies in engines are investigated. To develop control strategies for these engines, the reaction kinetics of iso-octane must be known starting from the low temperatures and intermediate pressures before ignition to the high temperatures and pressures of combustion. This work adds new experimental data sets to the validation data for reaction mechanism development by investigating the oxidation of iso-octane in stoichiometric mixtures in a flow reactor at pressures of p = 1, 10, and 20 bar and 473K ≤ T ≤ 973 K. The experimental data are compared to simulations with recent reaction mechanisms [Atef et al., Combustion and Flame 178, (2017), Bagheri et al., Combustion and Flame 212, (2020), Cai et al., Proceedings of the Combustion Institute 37, (2018), Fang et al., Combustion and Flame 214, (2020)]. The comparison between experimental and simulated mole fractions as function of temperature show reasonable agreement for all investigated pressures. In particular, the experimentally observed onset of low-temperature reactivity above a certain pressure, the shift of the negative temperature coefficient (NTC) regime with increasing pressure to higher temperatures, and the acceleration of the high-temperature chemistry are captured well in the simulations. Deviations between experimental and simulated results are discussed in detail for the reactivity of iso-octane and some key intermediates such as 2,2,4,4-tetramethyl-tetrahydrofuran, iso-butene and acetone at low temperatures. Copyright © 2022 Shaqiri, Kaczmarek, vom Lehn, Beeckmann, Pitsch and Kasper.
    view abstractdoi: 10.3389/fenrg.2022.859112
  • 2022 • 291 Development of Ultrafine–Grained and Nanostructured Bioinert Alloys Based on Titanium, Zirconium and Niobium and Their Microstructure, Mechanical and Biological Properties
    Sharkeev, Y. and Eroshenko, A. and Legostaeva, E. and Kovalevskaya, Z. and Belyavskaya, O. and Khimich, M. and Epple, M. and Prymak, O. and Sokolova, V. and Zhu, Q. and Zeming, S. and Hongju, Z.
    Metals 12 (2022)
    doi: 10.3390/met12071136
  • 2022 • 290 Selective 1,2 addition of polar X–H bonds to the Ga–P double bond of gallaphosphene L(Cl)GaPGaL
    Sharma, M.K. and Wölper, C. and Schulz, S.
    Dalton Transactions 51 1612-1616 (2022)
    Gallaphosphene L(Cl)GaPGaL 1 (L = HC[C(Me)N(2,6-i-Pr2-C6H3)]2) reacts at ambient temperature with a series of polar X–H bonds, i.e. ammonia, primary amines, water, phenol, thiophenol, and selenophenol, selectively with 1,2 addition at the polar Ga–P double bond. The gallium atom serves as electrophile and the phosphorous atom is protonated in all reactions. The resulting complexes L(Cl)GaP(H)Ga(X)L (X = NH22, NHi-Pr 3, NHPh 4, OH 5, OXyl 6, SPh 7, SePh 8) were characterized by IR and heteronuclear (1H, 13C{1H}, 31P{1H}) NMR spectroscopy, elemental analysis, and single-crystal X-ray diffraction. This journal is © The Royal Society of Chemistry
    view abstractdoi: 10.1039/d1dt04299h
  • 2022 • 289 Bis-Phosphaketenes LM(PCO)2 (M=Ga, In): A New Class of Reactive Group 13 Metal-Phosphorus Compounds
    Sharma, M.K. and Dhawan, P. and Helling, C. and Wölper, C. and Schulz, S.
    Chemistry - A European Journal (2022)
    Phosphaketenes are versatile reagents in organophosphorus chemistry. We herein report on the synthesis of novel bis-phosphaketenes, LM(PCO)2 (M=Ga 2 a, In 2 b; L=HC[C(Me)N(Ar)]2; Ar=2,6-i-Pr2C6H3) by salt metathesis reactions and their reactions with LGa to metallaphosphenes LGa(OCP)PML (M=Ga 3 a, In 3 b). 3 b represents the first compound with significant In−P π-bonding contribution as was confirmed by DFT calculations. Compounds 3 a and 3 b selectively activate the N−H and O−H bonds of aniline and phenol at the Ga−P bond and both reactions proceed with a rearrangement of the phosphaethynolate group from Ga−OCP to M−PCO bonding. Compounds 2–5 are fully characterized by heteronuclear (1H, 13C{1H}, 31P{1H}) NMR and IR spectroscopy, elemental analysis, and single crystal X-ray diffraction (sc-XRD). © 2022 The Authors. Chemistry - A European Journal published by Wiley-VCH GmbH
    view abstractdoi: 10.1002/chem.202200444
  • 2022 • 288 Modulating the frontier orbitals of L(X)Ga-substituted diphosphenes [L(X)GaP]2 (X = Cl, Br) and their facile oxidation to radical cations
    Sharma, M.K. and Chabbra, S. and Wölper, C. and Weinert, H.M. and Reijerse, E.J. and Schnegg, A. and Schulz, S.
    Chemical Science (2022)
    Modulating the electronic structures of main group element compounds is crucial to control their chemical reactivity. Herein we report on the synthesis, frontier orbital modulation, and one-electron oxidation of two L(X)Ga-substituted diphosphenes [L(X)GaP]2 (X = Cl 2a, Br 2b; L = HC[C(Me)N(Ar)]2, Ar = 2,6-i-Pr2C6H3). Photolysis of L(Cl)GaPCO 1 gave [L(Cl)GaP]22a, which reacted with Me3SiBr with halide exchange to [L(Br)GaP]22b. Reactions with MeNHC (MeNHC = 1,3,4,5-tetramethylimidazol-2-ylidene) gave the corresponding carbene-coordinated complexes L(X)GaPP(MeNHC)Ga(X)L (X = Cl 3a, Br 3b). DFT calculations revealed that the carbene coordination modulates the frontier orbitals (i.e. HOMO/LUMO) of diphosphenes 2a and 2b, thereby affecting the reactivity of 3a and 3b. In marked contrast to diphosphenes 2a and 2b, the cyclic voltammograms (CVs) of the carbene-coordinated complexes each show one reversible redox event at E1/2 = −0.65 V (3a) and −0.36 V (3b), indicating their one-electron oxidation to the corresponding radical cations as was confirmed by reactions of 3a and 3b with the [FeCp2][B(C6F5)4], yielding the radical cations [L(X)GaPP(MeNHC)Ga(X)L]B(C6F5)4 (X = Cl 4a, Br 4b). The unpaired spin in 4a (79%) and 4b (80%) is mainly located at the carbene-uncoordinated phosphorus atoms as was revealed by DFT calculations and furthermore experimentally proven in reactions with nBu3SnH, yielding the diphosphane cations [L(X)GaPHP(MeNHC)Ga(X)L]B(C6F5)4 (X = Cl 5a, Br 5b). Compounds 2-5 were fully characterized by NMR and IR spectroscopy as well as by single crystal X-ray diffraction (sc-XRD), and compounds 4a and 4b were further studied by EPR spectroscopy, while their bonding nature was investigated by DFT calculations. © 2022 The Royal Society of Chemistry.
    view abstractdoi: 10.1039/d2sc04207j
  • 2022 • 287 See-through Soil Measurements at 300 GHz
    Sheikh, F. and Zantah, Y. and Abbas, A.A. and Kaiser, T.
    International Conference on Infrared, Millimeter, and Terahertz Waves, IRMMW-THz 2022-August (2022)
    doi: 10.1109/IRMMW-THz50927.2022.9895574
  • 2022 • 286 Angle of Arrival and Angle of Departure Analysis in Scattering Environment for THz Wireless Links
    Sheikh, F. and Kaiser, T.
    2022 IEEE International Symposium on Antennas and Propagation and USNC-URSI Radio Science Meeting, AP-S/URSI 2022 - Proceedings 1688-1689 (2022)
    doi: 10.1109/AP-S/USNC-URSI47032.2022.9886074
  • 2022 • 285 Look Through Hygroscopic Indoor Materials at Frequencies from 750 GHz to 1.1 THz
    Sheikh, F. and Batra, A. and Prokscha, A. and Lessy, D. and Kaiser, T.
    AMTA 2022 - Proceedings: 2022 Antenna Measurement Techniques Association Symposium (2022)
    doi: 10.23919/AMTA55213.2022.9955003
  • 2022 • 284 Oxygen vacancies-enriched Ta-doped Bi2WO6 with Pt as cocatalyst for boosting the dehydrogenation of benzyl alcohol in water
    Shen, Z. and Hu, Y. and Pan, Q. and Huang, C. and Zhu, B. and Xia, W. and Wang, H. and Yue, J. and Muhler, M. and Zhao, G. and Wang, X. and Huang, X.
    Applied Surface Science 571 (2022)
    Selective photocatalytic oxidation of alcohols into value-added aldehydes or ketones is a promising alternative for alcohol oxidation concerning the mild reaction conditions and the controllable selectivity. To increase the activity, defective Bi2WO6 with abundant oxygen vacancies (OVs) was synthesized via substitution of W by Ta. The resulting Ta-doped Bi2WO6 loaded with Pt nanoparticles as co-catalyst efficiently converted aromatic and aliphatic alcohols into the corresponding carbonyl compounds with high selectivity (&gt;99%) in aqueous solution under visible-light irradiation and anaerobic conditions, with equivalent H2 as a coupled product. The optimal amount of benzyl alcohol converted by the Ta-doped catalyst was two times higher than that of the undoped catalyst. Surface OVs were found to favor the dissociative adsorption of the alcohols and to prolong the life time of the charge carriers. More importantly, isotopic labelling experiments confirmed that over Pt-loaded pristine undoped Bi2WO6, the coupled H2 product results from water reduction, while over Pt-loaded Ta-doped Bi2WO6, the produced H2 originates from benzyl alcohol, implying that benzyl alcohol can be photo-oxidized via a complete dehydrogenation pathway. Thus, enriched surface OVs in photocatalysts can activate α-C-H bonds in alcohols, boosting the photocatalytic oxidation performance. © 2021 Elsevier B.V.
    view abstractdoi: 10.1016/j.apsusc.2021.151370
  • 2022 • 283 Experimental and Numerical Investigation of Fluid-structure Interaction for a Submerged Oscillating Cylinder in a Lock-in Region
    Sheshtawy, H.E. and Youssef, M. and Moctar, O.E. and Schellin, T.E.
    International Journal of Offshore and Polar Engineering 32 74-80 (2022)
    doi: 10.17736/ijope.2022.ts24
  • 2022 • 282 EXPERIMENTAL INVESTIGATION OF FLOW AROUND A SINGLE CIRCULAR CYLINDER FREELY VIBRATING IN TWO DEGREES-OF-FREEDOM
    el Sheshtawy, H. and el Moctar, O. and Tödter, S. and Schellin, T.E.
    Proceedings of the International Conference on Offshore Mechanics and Arctic Engineering - OMAE 7 (2022)
    doi: 10.1115/OMAE2022-801150
  • 2022 • 281 A Compact Fiber-Coupled NIR/MIR Laser Absorption Instrument for the Simultaneous Measurement of Gas-Phase Temperature and CO, CO2, and H2O Concentration
    Shi, L. and Endres, T. and Jeffries, J.B. and Dreier, T. and Schulz, C.
    Sensors 22 (2022)
    A fiber-coupled, compact, remotely operated laser absorption instrument is developed for CO, CO2, and H2O measurements in reactive flows at the elevated temperatures and pressures expected in gas turbine combustor test rigs with target pressures from 1–25 bar and temperatures of up to 2000 K. The optical engineering for solutions of the significant challenges from the ambient acoustic noise (~120 dB) and ambient test rig temperatures (60 °C) are discussed in detail. The sensor delivers wavelength-multiplexed light in a single optical fiber from a set of solid-state lasers ranging from diodes in the near-infrared (~1300 nm) to quantum cascade lasers in the mid-infrared (~4900 nm). Wavelength-multiplexing systems using a single optical fiber have not previously spanned such a wide range of laser wavelengths. Gas temperature is inferred from the ratio of two water vapor transitions. Here, the design of the sensor, the optical engineering required for simultaneous fiber delivery of a wide range of laser wavelengths on a single optical line-of-sight, the engineering required for sensor survival in the harsh ambient environment, and laboratory testing of sensor performance in the exhaust gas of a flat flame burner are presented. © 2022 by the authors. Licensee MDPI, Basel, Switzerland.
    view abstractdoi: 10.3390/s22031286
  • 2022 • 280 Effect of High-Pressure Torsion on the Microstructure and Magnetic Properties of Nanocrystalline CoCrFeNiGax (x = 0.5, 1.0) High Entropy Alloys
    Shkodich, N. and Staab, F. and Spasova, M. and Kuskov, K.V. and Durst, K. and Farle, M.
    Materials 15 (2022)
    doi: 10.3390/ma15207214
  • 2022 • 279 Optimal Data-Generation Strategy for Machine Learning Yield Functions in Anisotropic Plasticity
    Shoghi, R. and Hartmaier, A.
    Frontiers in Materials 9 (2022)
    doi: 10.3389/fmats.2022.868248
  • 2022 • 278 Anisotropic carrier dynamics in a laser-excited Fe1/(MgO)3(001) heterostructure from real-time time-dependent density functional theory
    Shomali, E. and Gruner, M.E. and Pentcheva, R.
    Physical Review B 105 (2022)
    doi: 10.1103/PhysRevB.105.245103
  • 2022 • 277 Wear Mechanism Classification Using Artificial Intelligence
    Sieberg, P.M. and Kurtulan, D. and Hanke, S.
    Materials 15 (2022)
    doi: 10.3390/ma15072358
  • 2022 • 276 Ensuring the Reliability of Virtual Sensors Based on Artificial Intelligence within Vehicle Dynamics Control Systems
    Sieberg, P.M. and Schramm, D.
    Sensors 22 (2022)
    The use of virtual sensors in vehicles represents a cost-effective alternative to the installation of physical hardware. In addition to physical models resulting from theoretical modeling, artificial intelligence and machine learning approaches are increasingly used, which incorporate experimental modeling. Due to the resulting black-box characteristics, virtual sensors based on artificial intelligence are not fully reliable, which can have fatal consequences in safety-critical applications. Therefore, a hybrid method is presented that safeguards the reliability of artificial intelligence-based estimations. The application example is the state estimation of the vehicle roll angle. The state estimation is coupled with a central predictive vehicle dynamics control. The implementation and validation is performed by a co-simulation between IPG CarMaker and MATLAB/Simulink. By using the hybrid method, unreliable estimations by the artificial intelligence-based model resulting from erroneous input signals are detected and handled. Thus, a valid and reliable state estimate is available throughout. © 2022 by the authors. Licensee MDPI, Basel, Switzerland.
    view abstractdoi: 10.3390/s22093513
  • 2022 • 275 Towards a mechanistic understanding of the sol-gel syntheses of ternary carbides
    Siebert, J.P. and Juelsholt, M. and Günzing, D. and Wende, H. and Ollefs, K. and Birkel, C.S.
    Inorganic Chemistry Frontiers 9 1565-1574 (2022)
    Sol-gel chemistry, while being extremely established, is to this day not fully understood, and much of the underlying chemistry and mechanisms are yet to be unraveled. Here, we elaborate on the sol-gel chemistry of Cr2GaC, the first layered ternary carbide belonging to the MAX phase family to ever be synthesized using this wet chemical approach. Leveraging a variety of both in- and ex situ characterization techniques, including X-ray and neutron powder diffraction, X-ray absorption fine structure analyses, total scattering analyses, and differential scanning calorimetry coupled with mass spectrometry, in-depth analyses of the local structures and reaction pathways are elucidated. While the metals first form tetrahedrally and octahedrally coordinated oxidic structures, that subsequently grow and crystallize into oxides, the carbon source citric acid sits on a separate reaction pathway, that does not merge with the metals until the very end. In fact, after decomposing it remains nanostructured and disordered graphite until the temperature allows for the reduction of the metal oxides into the layered carbide. Based on this, we hypothesize that the method is mostly applicable to systems where the needed metals are reducible by graphite around the formation temperature of the target phase. © 2022 The Royal Society of Chemistry
    view abstractdoi: 10.1039/d2qi00053a
  • 2022 • 274 Noble-metal-free electrocatalysts for water splitting metal chalcogenides
    Siegmund, D. and Apfel, U.-P.
    Catalytic Science Series 22 19-79 (2022)
    doi: 10.1142/9781800611573_0002
  • 2022 • 273 The Journal of Chemical & Engineering Data: Introduction of Topical Sections and Updates from the Editorial Team
    Siepmann, J.I. and Gardas, R. and Kofke, D.A. and Nieto De Castro, C. and Paulechka, E. and Pini, R. and Sadowski, G. and Schwarz, C.E.
    Journal of Chemical and Engineering Data 67 1-2 (2022)
    doi: 10.1021/acs.jced.1c00969
  • 2022 • 272 Bandwidth Enhanced Circularly Polarized mm-Wave Antenna with On-Chip Ground Plane
    Sievert, B. and Wittemeier, J. and Svejda, J. and Pohl, N. and Erni, D. and Rennings, A.
    IEEE Transactions on Antennas and Propagation 1-1 (2022)
    doi: 10.1109/TAP.2022.3184539
  • 2022 • 271 Bandwidth-Enhanced Circularly Polarized mm-Wave Antenna with On-Chip Ground Plane
    Sievert, B. and Wittemeier, J. and Svejda, J.T. and Pohl, N. and Erni, D. and Rennings, A.
    IEEE Transactions on Antennas and Propagation 70 9139-9148 (2022)
    doi: 10.1109/TAP.2022.3184539
  • 2022 • 270 An Analytical Model to Approximate the Radiation Conductance of Microstrip Gaps
    Sievert, B. and Degen, M. and Svejda, J.T. and Erni, D. and Rennings, A.
    2022 52nd European Microwave Conference, EuMC 2022 238-241 (2022)
    doi: 10.23919/EuMC54642.2022.9924365
  • 2022 • 269 Redox Replacement of Silver on MOF-Derived Cu/C Nanoparticles on Gas Diffusion Electrodes for Electrocatalytic CO2 Reduction
    Sikdar, N. and Junqueira, J.R.C. and Öhl, D. and Dieckhöfer, S. and Quast, T. and Braun, M. and Aiyappa, H.B. and Seisel, S. and Andronescu, C. and Schuhmann, W.
    Chemistry - A European Journal 28 (2022)
    Bimetallic tandem catalysts have emerged as a promising strategy to locally increase the CO flux during electrochemical CO2 reduction, so as to maximize the rate of conversion to C−C-coupled products. Considering this, a novel Cu/C−Ag nanostructured catalyst has been prepared by a redox replacement process, in which the ratio of the two metals can be tuned by the replacement time. An optimum Cu/Ag composition with similarly sized particles showed the highest CO2 conversion to C2+ products compared to non-Ag-modified gas-diffusion electrodes. Gas chromatography and in-situ Raman measurements in a CO2 gas diffusion cell suggest the formation of top-bound linear adsorbed *CO followed by consumption of CO in the successive cascade steps, as evidenced by the increasingνC−H bands. These findings suggest that two mechanisms operate simultaneously towards the production of HCO2H and C−C-coupled products on the Cu/Ag bimetallic surface. © 2022 The Authors. Chemistry - A European Journal published by Wiley-VCH GmbH.
    view abstractdoi: 10.1002/chem.202104249
  • 2022 • 268 Single Particle Electrochemical Oxidation of Polyvinylpyrrolidone-Capped Silver Nanospheres, Nanocubes, and Nanoplates in Potassium Nitrate and Potassium Hydroxide Solutions
    Sikes, J.C. and Niyonshuti, I.I. and Kanokkanchana, K. and Chen, J. and Tschulik, K. and Fritsch, I.
    Journal of the Electrochemical Society 169 (2022)
    Single particle electrochemical oxidation of polyvinylpyrrolidone-capped silver nanoparticles at a microdisk electrode is investigated as a function of particle shape (spheres, cubes, and plates) in potassium nitrate and potassium hydroxide solutions. In potassium nitrate, extreme anodic potentials (1500 mV vs Ag/AgCl (3 M KCl)) are necessary to achieve oxidation, while lower anodic potentials are required in potassium hydroxide (900 mV vs Ag/AgCl (saturated KCl)). Upon oxidation, silver oxide is formed, readily catalyzing water oxidation, producing a spike-step current response. The spike duration for each particle is used to probe effects of particle shape on the oxidation mechanism, and is substantially shorter in nitrate solution at the large overpotentials than in hydroxide solution. The integration of current spikes indicates oxidation to a mixed-valence complex. In both electrolytes, the rate of silver oxidation strongly depends on silver content of the nanoparticles, rather than the shape-dependent variable surface area. The step height, which reflects rate of water oxidation, also tracks the silver content more so than shape. The reactivity of less-protected citrate-capped particles toward silver oxidation is also compared with that of the polymer-capped particles under these anodic conditions in the nitrate and hydroxide solutions. © 2022 Electrochemical Society Inc.. All rights reserved.
    view abstractdoi: 10.1149/1945-7111/ac63f3
  • 2022 • 267 Characterization of Nanoparticles in Diverse Mixtures Using Localized Surface Plasmon Resonance and Nanoparticle Tracking by Dark-Field Microscopy with Redox Magnetohydrodynamics Microfluidics
    Sikes, J.C. and Wonner, K. and Nicholson, A. and Cignoni, P. and Fritsch, I. and Tschulik, K.
    ACS Physical Chemistry Au 2 289-298 (2022)
    doi: 10.1021/acsphyschemau.1c00046
  • 2022 • 266 Laser-induced incandescence for non-soot nanoparticles: recent trends and current challenges
    Sipkens, T.A. and Menser, J. and Dreier, T. and Schulz, C. and Smallwood, G.J. and Daun, K.J.
    Applied Physics B: Lasers and Optics 128 (2022)
    Laser-induced incandescence (LII) is a widely used combustion diagnostic for in situ measurements of soot primary particle sizes and volume fractions in flames, exhaust gases, and the atmosphere. Increasingly, however, it is applied to characterize engineered nanomaterials, driven by the increasing industrial relevance of these materials and the fundamental scientific insights that may be obtained from these measurements. This review describes the state of the art as well as open research challenges and new opportunities that arise from LII measurements on non-soot nanoparticles. An overview of the basic LII model, along with statistical techniques for inferring quantities-of-interest and associated uncertainties is provided, with a review of the application of LII to various classes of materials, including elemental particles, oxide and nitride materials, and non-soot carbonaceous materials, and core–shell particles. The paper concludes with a discussion of combined and complementary diagnostics, and an outlook of future research. © 2022, The Author(s).
    view abstractdoi: 10.1007/s00340-022-07769-z
  • 2022 • 265 Bimetallic MxRu100−x nanoparticles (M = Fe, Co) on supported ionic liquid phases (MxRu100−x@SILP) as hydrogenation catalysts: Influence of M and M:Ru ratio on activity and selectivity
    Sisodiya-Amrute, S. and Van Stappen, C. and Rengshausen, S. and Han, C. and Sodreau, A. and Weidenthaler, C. and Tricard, S. and DeBeer, S. and Chaudret, B. and Bordet, A. and Leitner, W.
    Journal of Catalysis 407 141-148 (2022)
    Bimetallic iron-ruthenium and cobalt-ruthenium nanoparticles with systematic variations in the Fe:Ru and Co:Ru ratios are prepared following an organometallic approach and immobilized on an imidazolium-based supported ionic liquid phase (SILP). Resulting MxRu100-x@SILP materials are characterized by electron microscopy, X-ray diffraction and X-ray absorption spectroscopy, confirming the formation of small, well-dispersed and alloyed zero-valent bimetallic nanoparticles. A systematic comparison of the performances of FexRu100−x@SILP and CoxRu100−x@SILP catalysts is made using the hydrogenation of benzilideneacetone as model reaction. The M:Ru ratio is found to have a critical influence on activity and selectivity, with clear synergistic effects arising from the combination of the noble and 3d metals. CoxRu100−x@SILP catalysts are significantly more reactive to reach a given selectivity at a systematically higher content of the 3d metal as compared to the FexRu100−x@SILP catalysts, evidencing a remarkable influence of the nature of the “diluting” 3d metal on the overall performance of the MxRu100−x@SILP catalysts. © 2022 The Author(s)
    view abstractdoi: 10.1016/j.jcat.2022.01.030
  • 2022 • 264 Photochemical Sandmeyer-type Halogenation of Arenediazonium Salts
    Sivendran, N. and Belitz, F. and Sowa Prendes, D. and Manu Martínez, Á. and Schmid, R. and Gooßen, L.J.
    Chemistry - A European Journal 28 (2022)
    Trihalide salts were found to efficiently promote photochemical dediazotizing halogenations of diazonium salts. In contrast to classical Sandmeyer reactions, no metal catalysts are required to achieve high yields and outstanding selectivities for halogenation over competing hydridodediazotization. Convenient protocols are disclosed for synthetically meaningful brominations, iodinations, and chlorinations of diversely functionalized derivatives. © 2021 The Authors. Chemistry - A European Journal published by Wiley-VCH GmbH
    view abstractdoi: 10.1002/chem.202103669
  • 2022 • 263 MD studies of methanol confined in the metal-organic framework MOF MIL-88B-Cl
    Siwaipram, S. and Bopp, P.A. and Ponchai, P. and Soetens, J.-C. and Hasegawa, J.-Y. and Schmid, R. and Bureekaew, S.
    Journal of Molecular Liquids 359 (2022)
    The lattice of the flexible Metal–Organic Framework (MOF) MIL-88B(Fe)-Cl is strongly modified when it is subjected to methanol vapor, increasing its volume by more than 130 %. We use a newly developed interaction model belonging to the extended MOF-FF family to perform classical Molecular Dynamics (MD) simulations of this MOF with varying amounts of methanol guest molecules. This work focuses on the evolving intermolecular structure of the counterions and guest molecules when their number is increased from 1 to 30 per cavity. Two mobile Cl−-counterions are, on the average, present in each lattice cavity to neutralize the framework charges. At low loadings (in the closed (or semi-closed) systems), the methanol molecules aggregate around these ions, which are themselves pegged, at the time scale of the simulation, to the Fe3-centers of the MOF. At loadings just below the transition, such methanol aggregates may link two counterions on opposite Fe3-centers, thus preventing the MOF from opening unless more methanol is added. In all closed systems, the methanol self-diffusion is almost two orders of magnitude lower than in the bulk liquid. Once the MOF opens, i.e., at loadings higher than about 12 to 13 methanol molecules per cavity, structural features typical of liquid methanol become more and more apparent. However, the evolution is not monotonous, there is a transitional region up to about 22 molecules par cavity. Increasing the loading further, all features more and more resemble the ones of bulk liquid methanol. © 2022 Elsevier B.V.
    view abstractdoi: 10.1016/j.molliq.2022.119252
  • 2022 • 262 Physical and mechanical properties of winter first-year ice in the Antarctic marginal ice zone along the Good Hope Line
    Skatulla, S. and Audh, R.R. and Cook, A. and Hepworth, E. and Johnson, S. and Lupascu, D.C. and MacHutchon, K. and Marquart, R. and Mielke, T. and Omatuku, E. and Paul, F. and Rampai, T. and Schröder, J. and Schwarz, C. and Vichi, M.
    Cryosphere 16 2899-2925 (2022)
    As part of the 2019 Southern oCean seAsonal Experiment (SCALE) Winter Cruise of the South African icebreaker SA Agulhas II, first-year ice was sampled at the advancing outer edge of the Antarctic marginal ice zone along a 150km Good Hope Line transect. Ice cores were extracted from four solitary pancake ice floes of 1.83-2.95m diameter and 0.37-0.45m thickness as well as a 12×4m pancake ice floe of 0.31-0.76m thickness that was part of a larger consolidated pack ice domain. The ice cores were subsequently analysed for temperature, salinity, texture, anisotropic elastic properties and compressive strength. All ice cores from both solitary pancake ice floes and consolidated pack ice exhibited predominantly granular textures. The vertical distributions of salinity, brine volume and mechanical properties were significantly different for the two ice types. High salinity values of 12.6±4.9PSU were found at the topmost layer of the solitary pancake ice floes but not for the consolidated pack ice. The uniaxial compressive strengths for pancake ice and consolidated pack ice were determined as 2.3±0.5 and 4.1±0.9MPa, respectively. Young's and shear moduli in the longitudinal core direction of solitary pancake ice were obtained as 3.7±2.0 and 1.3±0.7GPa, respectively, and of consolidated pack ice as 6.4±1.6 and 2.3±0.6GPa, respectively. Comparing Young's and shear moduli measured in longitudinal and transverse core directions, a clear directional dependency was found, in particular for the consolidated pack ice. © Copyright:
    view abstractdoi: 10.5194/tc-16-2899-2022
  • 2022 • 261 On [H1]3×3 , [H(curl)] 3 and H(sym Curl) finite elements for matrix-valued Curl problems
    Sky, A. and Muench, I. and Neff, P.
    Journal of Engineering Mathematics 136 (2022)
    In this work we test the numerical behaviour of matrix-valued fields approximated by finite element subspaces of [H1]3×3, [H(curl)] 3 and H(symCurl) for a linear abstract variational problem connected to the relaxed micromorphic model. The formulation of the corresponding finite elements is introduced, followed by numerical benchmarks and our conclusions. The relaxed micromorphic continuum model reduces the continuity assumptions of the classical micromorphic model by replacing the full gradient of the microdistortion in the free energy functional with the Curl. This results in a larger solution space for the microdistortion, namely [H(curl)] 3 in place of the classical [H1]3×3. The continuity conditions on the microdistortion can be further weakened by taking only the symmetric part of the Curl. As shown in recent works, the new appropriate space for the microdistortion is then H(symCurl). The newly introduced space gives rise to a new differential complex for the relaxed micromorphic continuum theory. © 2022, The Author(s).
    view abstractdoi: 10.1007/s10665-022-10238-3
  • 2022 • 260 Primal and mixed finite element formulations for the relaxed micromorphic model
    Sky, A. and Neunteufel, M. and Muench, I. and Schöberl, J. and Neff, P.
    Computer Methods in Applied Mechanics and Engineering 399 (2022)
    The classical Cauchy continuum theory is suitable to model highly homogeneous materials. However, many materials, such as porous media or metamaterials, exhibit a pronounced microstructure. As a result, the classical continuum theory cannot capture their mechanical behaviour without fully resolving the underlying microstructure. In terms of finite element computations, this can be done by modelling the entire body, including every interior cell. The relaxed micromorphic continuum offers an alternative method by instead enriching the kinematics of the mathematical model. The theory introduces a microdistortion field, encompassing nine extra degrees of freedom for each material point. The corresponding elastic energy functional contains the gradient of the displacement field, the microdistortion field and its Curl (the micro-dislocation). Therefore, the natural spaces of the fields are [H1]3 for the displacement and [H(curl)]3 for the microdistortion, leading to unusual finite element formulations. In this work we describe the construction of appropriate finite elements using Nédélec and Raviart–Thomas subspaces, encompassing solutions to the orientation problem and the discrete consistent coupling condition. Further, we explore the numerical behaviour of the relaxed micromorphic model for both a primal and a mixed formulation. The focus of our benchmarks lies in the influence of the characteristic length Lc and the correlation to the classical Cauchy continuum theory. © 2022 Elsevier B.V.
    view abstractdoi: 10.1016/j.cma.2022.115298
  • 2022 • 259 Modeling of Particle Dissolution Behavior Using a Geometrical Phase-Field Approach
    Sleziona, D. and Ely, D.R. and Thommes, M.
    Molecular Pharmaceutics 19 3749-3756 (2022)
    Material dissolution is a critical attribute of many products in a wide variety of industries. The idealized view of dissolution through established prediction tools should be reconsidered because the number of new substances with low aqueous solubility is increasing. Due to this, a fundamental understanding of the dissolution process is desired. The aim of this study was to develop a tool to predict crystal dissolution performance based on experimentally measurable physical parameters. A numerical simulation, called the phase-field method, was used to simultaneously solve the time evolution of the phase and concentration fields of dissolving particles. This approach applies to diffusion-limited as well as surface reaction-limited systems. The numerical results were compared to analytical solutions, and the influence of particle shape and interparticle proximity on the dissolution process was numerically investigated. Dissolution behaviors of two different substances were modeled. A diffusion-limited model compound, xylitol, with a high aqueous solubility and a surface reaction-limited model compound, griseofulvin, with a low aqueous solubility were chosen. The results of the simulations demonstrated that phase-field modeling is a powerful approach for predicting the dissolution behaviors of pure crystalline substances. © 2022 American Chemical Society. All rights reserved.
    view abstractdoi: 10.1021/acs.molpharmaceut.2c00214
  • 2022 • 258 Theoretical simulation and experimental verification of dynamic caustic manipulation using a deformable mirror for laser material processing
    Smarra, M. and Gurevich, E.L. and Ostendorf, A.
    Optics and Laser Technology 149 (2022)
    The influence of a deformable mirror on spatial light modulation in ultrafast lasers processing is demonstrated. The deformable mirror was integrated into an optical setup which contains an additional lens for generating a nearly linear focus shift in the focal plane behind the f-theta lens. The deformation of the mirror surface can be described by the Zernike terms Defocus, Astigmatism, and a combination of both, resulting in a cylindric lens behavior. The influence of the mirror surface deformation in this optical setup on the intensity distribution in the focal plane was simulated. From the simulation results, the caustic in the focal plane was calculated. The simulation results were compared to experiments using a picosecond laser with a maximum pulse energy of about 60 µJ. We demonstrate that the initial astigmatism of the raw beam can be reduced using the deformable mirror. A linear focus shift (R2=98.7%) and the generation of elliptical/ line intensity distributions are shown. Line intensity distribution was used to demonstrate slit drilling application in thin metal foils. © 2021
    view abstractdoi: 10.1016/j.optlastec.2021.107814
  • 2022 • 257 Inner relaxations in equiatomic single-phase high-entropy cantor alloy
    Smekhova, A. and Kuzmin, A. and Siemensmeyer, K. and Abrudan, R. and Reinholz, U. and Buzanich, A.G. and Schneider, M. and Laplanche, G. and Yusenko, K.V.
    Journal of Alloys and Compounds 920 (2022)
    The superior properties of high-entropy multi-functional materials are strongly connected with their atomic heterogeneity through many different local atomic interactions. The detailed element-specific studies on a local scale can provide insight into the primary arrangements of atoms in multicomponent systems and benefit to unravel the role of individual components in certain macroscopic properties of complex compounds. Herein, multi-edge X-ray absorption spectroscopy combined with reverse Monte Carlo simulations was used to explore a homogeneity of the local crystallographic ordering and specific structure relaxations of each constituent in the equiatomic single-phase face-centered cubic CrMnFeCoNi high-entropy alloy at room temperature. Within the considered fitting approach, all five elements of the alloy were found to be distributed at the nodes of the fcc lattice without any signatures of the additional phases at the atomic scale and exhibit very close statistically averaged interatomic distances (2.54 – 2.55 Å) with their nearest-neighbors. Enlarged structural displacements were found solely for Cr atoms. The macroscopic magnetic properties probed by conventional magnetometry demonstrate no opening of the hysteresis loops at 5 K and illustrate a complex character of the long-range magnetic order after field-assisted cooling in± 5 T. The observed magnetic behavior is assigned to effects related to structural relaxations of Cr. Besides, the advantages and limitations of the reverse Monte Carlo approach to studies of multicomponent systems like high-entropy alloys are highlighted. © 2022 Elsevier B.V.
    view abstractdoi: 10.1016/j.jallcom.2022.165999
  • 2022 • 256 Trimetallic Pentlandites (Fe,Co,Ni)9S8for the Electrocatalytical HER in Acidic Media
    Smialkowski, M. and Siegmund, D. and Stier, K. and Hensgen, L. and Checinski, M.P. and Apfel, U.-P.
    ACS Materials Au 2 474-481 (2022)
    doi: 10.1021/acsmaterialsau.2c00016
  • 2022 • 255 Properties of gas-atomized Cu-Ti-based metallic glass powders for additive manufacturing
    Soares Barreto, E. and Frey, M. and Wegner, J. and Jose, A. and Neuber, N. and Busch, R. and Kleszczynski, S. and Mädler, L. and Uhlenwinkel, V.
    Materials and Design 215 (2022)
    Laser powder bed fusion (PBF-LB/M) of bulk metallic glasses permits large and complex components to solidify to an amorphous state, thus expanding the processing possibilities of this material class. Here, the Cu-Ti-Zr-Ni family, also known as Vitreloy 101, is systematically investigated for processing of the PBF-LB/M powder itself. Gas atomization was used to produce powder of Vit101 and derivates micro-alloyed with Si and Sn. The influence of atomization and alloy composition on glass formation, oxygen content, particle morphology, and flowability were investigated. Amorphous powder was successfully obtained using industrial-grade purity as feedstock for the atomization. The oxygen content within the powder was controlled by the surface-to-volume ratio, without significant influence of the different atomization parameters and the microalloying itself. The powder displayed high circularity with sufficient flowability after drying. Our results contribute to the investigation of Vitreloy 101 alloys as promising candidates for PBF-LB/M applications. © 2022 The Author(s)
    view abstractdoi: 10.1016/j.matdes.2022.110519
  • 2022 • 254 Ab initio investigations of point and complex defect structures in B2-FeAl
    Sözen, H.I. and Mendive-Tapia, E. and Hickel, T. and Neugebauer, J.
    Physical Review Materials 6 (2022)
    We study single-site and two-site defect structures in B2-type Fe-Al alloys by means of density functional theory supercell calculations. The defect formation energies are calculated as functions of the chemical potential, which are used to obtain the dependence of the defect concentrations on Al content at different temperatures. We also examine the converging behavior of the formation energies with respect to the supercell size to study the corresponding limit of dilute defects. The effect of magnetism is investigated by considering nonmagnetic, ferromagnetic, and paramagnetic states, calculations for the latter showing that the magnitude of the local magnetic moments strongly impacts the defect formation energies. The methodological studies are used to provide explanations for the wide spread of defect formation energies reported by experiments and other theoretical investigations. Based on these insights, the stability of the B2-FeAl structure as a function of Al concentration is obtained and discussed. © 2022 authors. Published by the American Physical Society.published article's title, journal citation, and DOI. Open access publication funded by the Max Planck Society.
    view abstractdoi: 10.1103/PhysRevMaterials.6.023603
  • 2022 • 253 Uptake of Functional Ultrasmall Gold Nanoparticles in 3D Gut Cell Models
    Sokolova, V. and Ebel, J.-F. and Kollenda, S. and Klein, K. and Kruse, B. and Veltkamp, C. and Lange, C.M. and Westendorf, A.M. and Epple, M.
    Small 18 (2022)
    doi: 10.1002/smll.202201167
  • 2022 • 252 Magnetic and structural properties of Co-Ni-Z (Z= Al, Ga, In, Sn) Heusler alloys: Effect of structural motives and chemical disorder
    Sokolovskiy, V. and Miroshkina, O.N. and Sanosyan, A. and Baigutlin, D. and Buchelnikov, V. and Gruner, M.E.
    Journal of Magnetism and Magnetic Materials 546 (2022)
    Ground state properties of Ni-excess Co2Ni1+xZ1−x (Z= Al, Ga, In, Sn) full Heusler alloys are investigated by abinitio calculations. We consider the effect of different structural motives and chemical disorder on structural stability and magnetic characteristics of these alloys. Co-Ni-(In, Sn) are found to be unstable with respect to decomposition into pure bulk elements. Co2Ni(Al, Ga) are stable, however, introducing the Ni excess destabilizes these alloys making off-stoichiometric Co2Ni1+xAl1−x and Co2Ni1+xGa1−x unstable at x&gt;0.5 and x&gt;0.25, respectively. Saturation magnetization Ms of Co2Ni(Al, Ga) is of the same order like other Co2Ni-based Heusler alloys. Our study showed that an effective way to increase Ms is the introducing of chemical disorder. For stable compounds in which a tetragonal structure with alternating planes of Co and Ni exists, we calculate the magnetocrystalline anisotropy energy (MAE) given large values about −2 MJ/m3 with in-plane favorable spin configuration. The deviation from stoichiometry reduces the MAE by a factor of two. © 2021 Elsevier B.V.
    view abstractdoi: 10.1016/j.jmmm.2021.168728
  • 2022 • 251 Impact of local arrangement of Fe and Ni on the phase stability and magnetocrystalline anisotropy in Fe-Ni-Al Heusler alloys
    Sokolovskiy, V.V. and Miroshkina, O.N. and Buchelnikov, V.D. and Gruner, M.E.
    Physical Review Materials 6 (2022)
    On the basis of density functional calculations, we report on a comprehensive study of the influences of atomic arrangement and Ni substitution for Al on the ground-state structural and magnetic properties for Fe2Ni1+xAl1-x Heusler alloys. We discuss systematically the competition between five Heusler-type structures formed by shuffles of Fe and Ni atoms and their thermodynamic stability. All Ni-rich Fe2Ni1+xAl1-x tend to decompose into a dual-phase mixture consisting of Fe2NiAl and FeNi. The successive replacement of Ni by Al leads to a change of ground-state structure and eventually an increase in magnetocrystalline anisotropy energy (MAE). We predict for stoichiometric Fe2NiAl a ground-state structure with nearly cubic lattice parameters but alternating layers of Fe and Ni possessing a uniaxial MAE that is even larger than tetragonal L10-FeNi. This opens an alternative route for improving the phase stability and magnetic properties in FeNi-based permanent magnets. © 2022 American Physical Society.
    view abstractdoi: 10.1103/PhysRevMaterials.6.025402
  • 2022 • 250 Nonparametric and high-dimensional functional graphical models
    Solea, E. and Dette, H.
    Electronic Journal of Statistics 16 6175-6231 (2022)
    doi: 10.1214/22-EJS2087
  • 2022 • 249 Tuning the High-Pressure Phase Behaviour of Highly Compressible Zeolitic Imidazolate Frameworks: From Discontinuous to Continuous Pore Closure by Linker Substitution
    Song, J. and Pallach, R. and Frentzel-Beyme, L. and Kolodzeiski, P. and Kieslich, G. and Vervoorts, P. and Hobday, C.L. and Henke, S.
    Angewandte Chemie - International Edition 61 (2022)
    doi: 10.1002/anie.202117565
  • 2022 • 248 Green steel at its crossroads: Hybrid hydrogen-based reduction of iron ores
    Souza Filho, I.R. and Springer, H. and Ma, Y. and Mahajan, A. and da Silva, C.C. and Kulse, M. and Raabe, D.
    Journal of Cleaner Production 340 (2022)
    Iron- and steelmaking cause ∼7% of the global CO2 emissions, due to the use of carbon for the reduction of iron ores. Replacing carbon by hydrogen as the reductant offers a pathway to massively reduce these emissions. However, the production of hydrogen using renewable energy will remain as one of the bottlenecks at least during the next two decades, because making the gigantic annual crude steel production of 1.8 billion tons sustainable requires a minimum stoichiometric amount of ∼97 million tons of green hydrogen per year. Another fundamental aspect to render the ironmaking sector more sustainable lies in an optimal utilization of green hydrogen and energy, thus reducing efforts for costly in-process hydrogen recycling. We therefore demonstrate here how the efficiency in hydrogen and energy consumption during iron ore reduction can be dramatically improved by the knowledge-based combination of two technologies: partially reducing the ore at low temperature via solid-state direct reduction (DR) to a kinetically defined degree, and subsequently melting and completely transforming it to iron under a reducing plasma (i.e. via hydrogen plasma reduction, HPR). Results suggest that an optimal transition point between these two technologies occurs where their efficiency in hydrogen utilization is equal. We found that the reduction of hematite through magnetite into wüstite via DR is clean and efficient, but it gets sluggish and inefficient when iron forms at the outermost layers of the iron ore pellets. Conversely, HPR starts violent and unstable with arc delocalization, but proceeds smoothly and efficiently when processing semi-reduced oxides, an effect which might be related to the material's high electrical conductivity. We performed hybrid reduction experiments by partially reducing hematite pellets via DR at 700 °C to 38% global reduction (using a standard thermogravimetry system) and subsequently transferring them to HPR, conducted with a lean gas mixture of Ar-10%H2 in an arc-melting furnace, to achieve full conversion into liquid iron. This hybrid approach allows to exploit the specific characteristics and kinetically favourable regimes of both technologies, while simultaneously showing the potential to keep the consumption of energy and hydrogen low and improve both, process stability and furnace longevity by limiting its overexposure to plasma radiation. © 2022 Elsevier Ltd
    view abstractdoi: 10.1016/j.jclepro.2022.130805
  • 2022 • 247 Comparison of ultrashort pulse ablation of gold in air and water by time-resolved experiments
    Spellauge, M. and Doñate-Buendía, C. and Barcikowski, S. and Gökce, B. and Huber, H.P.
    Light: Science and Applications 11 (2022)
    doi: 10.1038/s41377-022-00751-6
  • 2022 • 246 Effects of steel fibres on hammer drilling in concrete for the installation of post-installed anchors
    Spyridis, P. and Walter, L. and Biermann, D. and Dreier, J.
    Journal of Building Engineering 52 (2022)
    doi: 10.1016/j.jobe.2022.104395
  • 2022 • 245 Multilateral Assessment of Anchorage Bond Characteristics in Steel Fibre Reinforced Concrete
    Spyridis, P. and Dreier, J. and Mellios, N. and Walter, L. and Biermann, D.
    Polymers 14 (2022)
    doi: 10.3390/polym14071411
  • 2022 • 244 Unveiling nonmonotonic chemical trends in the solubility of H in complex Fe-Cr-Mn carbides by means of ab initio based approaches
    Sreekala, L. and Dey, P. and Hickel, T. and Neugebauer, J.
    Physical Review Materials 6 (2022)
    The microstructure of advanced high-strength steels often shows a sensitive dependence on alloying. For example, adding Cr to improve the corrosion resistance of medium-Mn steels also enhances the precipitation of carbides. The current study focuses on the behavior of H in such complex multicomponent carbides by employing different methodological strategies. We systematically analyze the impact of Cr, Mn, and Fe using density functional theory (DFT) for two prototype precipitate phases, M3C and M23C6, where M represents the metal sublattice. Our results show that the addition of these alloying elements yields strong nonmonotonic chemical trends for the H solubility. We identify magnetovolume effects as the origin for this behavior, which depend on the considered system, the sites occupied by H, and short- vs long-range interactions between H and the alloying elements. We further show that the H solubility is directly correlated with the occupation of its nearest-neighbor shells by Cr and Mn. Based on these insights, DFT data from H containing binary-metal carbides are used to design a ridge regression based model that predicts the solubility of H in the ternary-metal carbides (Fe-Cr-Mn-C). © 2022 authors. Published by the American Physical Society.
    view abstractdoi: 10.1103/PhysRevMaterials.6.014403
  • 2022 • 243 Concentration Dependent Effect of Quaternary Amines on the Adhesion of U251-MG Cells
    Stamm, N. and Glotzbach, K. and Faissner, A. and Weberskirch, R.
    Gels 8 (2022)
    doi: 10.3390/gels8120827
  • 2022 • 242 Angular-dependent interatomic potential for large-scale atomistic simulation of the Fe-Cr-H ternary system
    Starikov, S. and Smirnova, D. and Pradhan, T. and Gordeev, I. and Drautz, R. and Mrovec, M.
    Physical Review Materials 6 (2022)
    doi: 10.1103/PhysRevMaterials.6.043604
  • 2022 • 241 Investigation of the Adsorption of Hydrogen Sulfide on Faujasite Zeolites Focusing on the Influence of Cations
    Starke, A. and Pasel, C. and Bläker, C. and Eckardt, T. and Zimmermann, J. and Bathen, D.
    ACS Omega 7 43665-43677 (2022)
    doi: 10.1021/acsomega.2c04606
  • 2022 • 240 A Fully Integrated 0.48 THz FMCW Radar Transceiver MMIC in a SiGe-Technology
    Starke, D. and Wittemeier, J. and Vogelsang, F. and Sievert, B. and Erni, D. and Rennings, A. and Rucker, H. and Pohl, N.
    2022 17th European Microwave Integrated Circuits Conference, EuMIC 2022 56-59 (2022)
    doi: 10.23919/EuMIC54520.2022.9923443
  • 2022 • 239 Disproportional surface segregation in ligand-free gold-silver alloy solid solution nanoparticles, and its implication for catalysis and biomedicine
    Stein, F. and Kohsakowski, S. and Martinez-Hincapie, R. and Reichenberger, S. and Rehbock, C. and Colic, V. and Guay, D. and Barcikowski, S.
    Faraday Discussions (2022)
    doi: 10.1039/d2fd00092j
  • 2022 • 238 Adsorption of Mercury on Chlorine-Modified Activated Carbon: Breakthrough Curves and Temperature-Programmed Desorption
    Steinhaus, J. and Pasel, C. and Bläker, C. and Bathen, D.
    ACS Omega 7 23833-23841 (2022)
    doi: 10.1021/acsomega.2c02515
  • 2022 • 237 Growth Rate and Thermal Properties of DNA Origami Filaments
    Stenke, L.J. and Saccà, B.
    Nano Letters (2022)
    Synthetic DNA filaments exploit the programmability of the individual units and their predictable self-association to mimic the structural and dynamic features of natural protein filaments. Among them, DNA origami filamentous structures are of particular interest, due to the versatility of morphologies, mechanical properties, and functionalities attainable. We here explore the thermodynamic and kinetic properties of linear structures grown from a ditopic DNA origami unit, i.e., a monomer with two distinct interfaces, and employ either base-hybridization or base-stacking interactions to trigger the dimerization and polymerization process. By observing the temporal evolution of the system toward equilibrium, we reveal kinetic aspects of filament growth that cannot be easily captured by postassembly studies. Our work thus provides insights into the thermodynamics and kinetics of hierarchical DNA origami assembly and shows how it can be mastered by the anisotropy of the building unit and its self-association mode. © 2022 The Authors. Published by American Chemical Society.
    view abstractdoi: 10.1021/acs.nanolett.2c02255
  • 2022 • 236 Design, Mechanical Properties, and Dynamics of Synthetic DNA Filaments
    Stenke, L.J. and Saccà, B.
    Bioconjugate Chemistry (2022)
    Over the past 40 years, structural and dynamic DNA nanotechnologies have undoubtedly demonstrated to be effective means for organizing matter at the nanoscale and reconfiguring equilibrium structures, in a predictable fashion and with an accuracy of a few nanometers. Recently, novel concepts and methodologies have been developed to integrate nonequilibrium dynamics into DNA nanostructures, opening the way to the construction of synthetic materials that can adapt to environmental changes and thus acquire new properties. In this Review, we summarize the strategies currently applied for the construction of synthetic DNA filaments and conclude by reporting some recent and most relevant examples of DNA filaments that can emulate typical structural and dynamic features of the cytoskeleton, such as compartmentalization in cell-like vesicles, support for active transport of cargos, sustained or transient growth, and responsiveness to external stimuli. ©
    view abstractdoi: 10.1021/acs.bioconjchem.2c00312
  • 2022 • 235 Improving the Defect Tolerance of PBF-LB/M Processed 316L Steel by Increasing the Nitrogen Content
    Stern, F. and Becker, L. and Cui, C. and Tenkamp, J. and Uhlenwinkel, V. and Steinbacher, M. and Boes, J. and Lentz, J. and Fechte-Heinen, R. and Weber, S. and Walther, F.
    Advanced Engineering Materials (2022)
    Nitrogen (N) in steels can improve their mechanical strength by solid solution strengthening. Processing N-alloyed steels with additive manufacturing, here laser powder bed fusion (PBF-LB), is challenging as the N-solubility in the melt can be exceeded. This degassing of N counteracts its intended positive effects. Herein, the PBF-LB processed 316L stainless steel with increased N-content is investigated and compared to PBF-LB 316L with conventional N-content. The N is introduced into the steel by nitriding the powder and mixing it with the starting powder to achieve an N-content of approximately 0.16 mass%. Thermodynamic calculations for maximum solubility to avoid N outgassing and pore formation under PBF-LB conditions are performed beforehand. Based on the results, a higher defect tolerance under fatigue characterized by Murakami model can be achieved without negatively influencing the PBF-LB processability of the 316L steel. The increased N-content leads to higher hardness (+14%), yield strength (+16%), tensile strength (+9%), and higher failure stress in short time fatigue test (+16%). © 2022 The Authors. Advanced Engineering Materials published by Wiley-VCH GmbH.
    view abstractdoi: 10.1002/adem.202200751
  • 2022 • 234 Characterization of Flow Curves for Ultra-Thin Steel Sheets With the In-Plane Torsion Test
    Stiebert, F. and Traphöner, H. and Meya, R. and Tekkaya, A.E.
    Journal of Manufacturing Science and Engineering, Transactions of the ASME 144 (2022)
    The in-plane torsion test (IPT) is a shear test that has already been successfully used to determine flow curves up to high strains for thin sheets with thicknesses between 0.5 mm and 3.0 mm. In the same way as with other shear tests, the formation of wrinkles is a major challenge in determining flow curves with the IPT, especially when testing ultrathin sheets with a thickness between 0.1 mm and 0.5 mm. A new method for suppressing wrinkling is introduced, in which the formation of wrinkles is avoided by arranging and gluing single sheets to multi-layered specimens. The influence of the used adhesive on the determination of flow curves is negligible. The proposed method is used to identify flow curves for two materials, the high-strength steel TH620 and the soft steel TS230, used in the packaging industry. The materials are tested in sheet thicknesses between 0.17 mm and 0.6 mm. The determined equivalent plastic strains for the TH620 with a sheet thickness of 0.20 mm could be increased from 0.38 (bulge-test) to over 0.8 with the new method using four-layered specimens. Copyright © 2021 by ASME.
    view abstractdoi: 10.1115/1.4051919
  • 2022 • 233 Fluorinated β-diketonate complexes M(tfac)2(TMEDA) (M = Fe, Ni, Cu, Zn) as precursors for the MOCVD growth of metal and metal oxide thin films
    Stienen, C. and Grahl, J. and Wölper, C. and Schulz, S. and Bendt, G.
    RSC Advances 12 22974-22983 (2022)
    Partially fluorinated β-diketonate complexes M(tfac)2(TMEDA) (M = Fe 1, Ni 2, Cu 3, Zn 4; tfac = 1,1,1-trifluoro-2,4-pentanedionate; TMEDA = N,N,N′,N′-tetramethylethylenediamine) were synthesized and structurally (sc-XRD) and thermochemically (TGA) characterised. A new polymorph of Fe(tfac)2(TMEDA) was found. The structural and physicochemical properties of 1-4 were compared with related M(acac)2(TMEDA) and M(hfac)2(TMEDA) (acac = 2,4-pentanedionate, hfac = 1,1,1,5,5,5-hexafluoro-2,4-pentanedionate) β-diketonate complexes to evaluate the effect of the degree of fluorination. A positive effect on the thermal behaviour of the metal acetylacetonates was observed, but no discernible trends. Application of complexes 1-4 as precursors in a MOCVD process yielded either metal (Ni, Cu) or metal oxide thin films (Fe3O4, ZnO), which were further oxidized to NiO, CuO and α-Fe2O3 films by calcination in air at 500 °C. © 2022 The Royal Society of Chemistry.
    view abstractdoi: 10.1039/d2ra01338j
  • 2022 • 232 Inverse modeling of cancellous bone using artificial neural networks
    Stieve, V. and Blaszczyk, M. and Hackl, K.
    ZAMM Zeitschrift fur Angewandte Mathematik und Mechanik (2022)
    Artificial neural networks are used to solve different tasks of daily life, engineering and medicine. In this work, we investigate its suitability for the examination of simulation results of cancellous bone with the aim to evaluate whether the bone is affected by osteoporosis. This bone disease is characterized by a reduction of the cortical bone phase, one of the two main components of the bone. The neural network predicts the simulated volume fraction in different parts of a cylinder, which models the bone. As a basis for its calculations, the neural network gets the information about the magnetic field inside the cylinder from finite element simulations. Examinations show that it is possible to train neural networks on solving that task with very high accuracies. © 2022 The Authors. ZAMM - Journal of Applied Mathematics and Mechanics published by Wiley-VCH GmbH.
    view abstractdoi: 10.1002/zamm.202100541
  • 2022 • 231 Scrutinizing the Debye plasma model: Rydberg excitons unravel the properties of low-density plasmas in semiconductors
    Stolz, H. and Semkat, D. and Schwartz, R. and Heckötter, J. and Aßmann, M. and Kraeft, W.-D. and Fehske, H. and Bayer, M.
    Physical Review B 105 (2022)
    For low-density plasmas, the classical limit described by the Debye-Hückel theory is still considered as an appropriate description even though a clear experimental proof of this paradigm is lacking due to the problems in determining the plasma-induced shift of single-particle energies in atomic systems. We show that Rydberg excitons in states with a high principal quantum number are highly sensitive probes for their surrounding making it possible to unravel accurately the basic properties of low-density nondegenerate electron-hole plasmas. To this end, we accurately measure the parameters of Rydberg excitons such as energies and linewidths in absorption spectra of bulk cuprous oxide crystals in which a tailored electron-hole plasma has been generated optically. Since from the absorption spectra exciton energies, as well as the shift of the single-particle energies given by the band edge, can be directly derived, the measurements allow us to determine the plasma density and temperature independently, which has been a notoriously hard problem in semiconductor physics. Our analysis shows unambiguously that the impact of the plasma cannot be described by the classical Debye model, but requires a quantum many-body theory, not only for the semiconductor plasma investigated here, but in general. Furthermore, it reveals an exciton scattering mechanism with coupled plasmon-phonon modes becoming important even at very low plasma densities. © 2022 American Physical Society.
    view abstractdoi: 10.1103/PhysRevB.105.075204
  • 2022 • 230 Incorporation of Fluoride into Human Teeth after Immersion in Fluoride-Containing Solutions
    Storsberg, J. and Loza, K. and Epple, M.
    Dentistry Journal 10 (2022)
    doi: 10.3390/dj10080153
  • 2022 • 229 Tension and interaction resistance of austenitic and duplex stainless steel bolts
    Stranghöner, N. and Abraham, C.
    Journal of Constructional Steel Research 198 (2022)
    The current design rules in EN 1993-1-4 for non-preloaded stainless steel bolted connections under pure shear and tension are essentially based on the regulations for carbon steel bolted connections. Furthermore, the load bearing behaviour under combined tension and shear (category A + D bolted connections) was adopted from EN 1993-1-8 as well. Recent research activities within the German IGF research project “Load-bearing capacity of bolted connections loaded in shear and tension made of stainless steel M12 to M36” (P 1386/IGF-No. 20651 N) showed that stainless steel bolting assemblies behave different. Herein, systematic experimental investigations and an extensive literature review into the shear, tension and interaction resistance of stainless steel bolts were conducted. Furthermore, reliability analyses according to EN 1990, Annex D were accomplished to prove the partial safety factor of γM2 = 1.25 for connections made of stainless steel bolting assemblies. The results regarding the shear resistance have already been presented in a former paper in this journal. In these investigations, it could be shown that an increase of the tension resistance Ft,Rd with k2 = 1.0 is in principle possible following the normative regulations of EN ISO 3506-1 regarding the minimum ultimate tensile strength as well as North American ANSI/AISC 360 and Australian Standard AS 4100. Furthermore, a new interaction approach for both unthreaded and threaded part of the bolt lying in the shear plane could be proposed which has statistically been verified for all property classes with γM* &lt; γΜ2 = 1.25. The new regulations have already been implemented in the current revision of EN 1993-1-4. The background for the new regulations is presented in this contribution. © 2022 Elsevier Ltd
    view abstractdoi: 10.1016/j.jcsr.2022.107536
  • 2022 • 228 New design rules for bolted connections made of stainless steel [Neue Bemessungsregeln für geschraubte Verbindungen aus nichtrostendem Stahl]
    Stranghöner, N. and Abraham, C.
    Stahlbau 91 454-470 (2022)
    New design rules for bolted connections made of stainless steel. The tensile/shear behaviour of stainless steel bolts is significantly influenced by their specific material properties (non-linearity, strain hardening). However, this is currently only taken into account to a limited extent in the design. Essentially, the design according to EN 1993-1-4 is based on regulations of EN 1993-1-8, which were derived for bolts made of carbon steel. At national level, the shear capacities of stainless austenitic bolts have already been designed differently, based on a few investigations. For duplex stainless bolts, there have been no specific regulations at all so far. Within the framework of the IGF research project no. 20651 N “Development of a normative basis of the load bearing capacity of bolted connections loaded in shear and tension made of austenitic and austenitic-ferritic (duplex) stainless steel M12 to M36”, experimental and numerical investigations as well as statistical evaluations according to EN 1990 on the tensile, shear and combined tensile-shear load-bearing capacity of bolts made of stainless steel were carried out systematically for the first time. The results have currently been implemented into the revision of EN 1993-1-4. In addition, the bearing resistance of stainless steel plates was investigated. Ultimately, the new regulations lead to a more economical design of bolted connections made of stainless steel. © 2022, Ernst und Sohn. All rights reserved.
    view abstractdoi: 10.1002/stab.202200026
  • 2022 • 227 Slip-resistant connections with imperfections [Gleitfeste Verbindungen mit Imperfektionen]
    Stranghöner, N. and Makevičius, L. and Flügge, W. and Henkel, K.-M. and Glienke, R. and Dörre, M. and Schwarz, M. and Rudolf, A. and Fiedler, S.
    Stahlbau 91 442-453 (2022)
    Slip-resistant connections with imperfections. Slip-resistant connections are traditionally used in steel and plant structures whenever slip and deformation in the bolted connections must be minimized. The current test procedure according to EN 1090-2, Annex G is limited to the basic load-bearing behaviour under laboratory conditions. For the industry, important questions are to which extent production-, assembly- and operation-related influences have to be considered in the design of slip-resistant connections, as they affect the economic efficiency of this type of connection. In the frame of the IGF research project 19749 BG “Influence of manufacturing- and assembly-related imperfections on the bearing behaviour of bolted slip-resistant connections in steel structures” carried out by the Institute for Metal and Lightweight Structures (IML) of the University of Duisburg-Essen in cooperation with Fraunhofer Institute for Large Structures in Production Engineering (IGP), Rostock and Institute for Corrosion Protection Dresden GmbH (IKS), systematic investigations into slip-resistant connections of categories B/C according to EN 1993-1-8 were carried out. Herein, reference tests were conducted without imperfections and then compared with connections with artificial imperfections. Based on the test results, the influence of different imperfections on the load-bearing behaviour of slip-resistant connections in steel construction could be determined. © 2022, Ernst und Sohn. All rights reserved.
    view abstractdoi: 10.1002/stab.202200028
  • 2022 • 226 Disproportionation of Nitric Oxide at a Surface-Bound Nickel Porphyrinoid
    Stredansky, M. and Moro, S. and Corva, M. and Sturmeit, H. and Mischke, V. and Janas, D. and Cojocariu, I. and Jugovac, M. and Cossaro, A. and Verdini, A. and Floreano, L. and Feng, Z. and Sala, A. and Comelli, G. and Windischbach...
    Angewandte Chemie - International Edition 61 (2022)
    doi: 10.1002/anie.202201916
  • 2022 • 225 Dislocation structure analysis in the strain gradient of torsion loading: A comparison between modelling and experiment
    Stricker, M. and Ziemann, M. and Walter, M. and Weygand, S.M. and Gruber, P. and Weygand, D.
    Modelling and Simulation in Materials Science and Engineering 30 (2022)
    Complex stress states due to torsion lead to dislocation structures characteristic for the chosen torsion axis. The formation mechanism of these structures and the link to the overall plastic deformation are unclear. Experiments allow the analysis of cross sections only ex situ or are limited in spacial resolution which prohibits the identification of the substructures which form within the volume. Discrete dislocation dynamics simulations give full access to the dislocation structure and their evolution in time. By combining both approaches and comparing similar measures the dislocation structure formation in torsion loading of micro wires is explained. For the «100»torsion axis, slip traces spanning the entire sample in both simulation and experiment are observed. They are caused by collective motion of dislocations on adjacent slip planes. Thus these slip traces are not atomically sharp. Torsion loading around a «111»axis favors plasticity on the primary slip planes perpendicular to the torsion axis and dislocation storage through cross-slip and subsequent collinear junction formation. Resulting hexagonal dislocation networks patches are small angle grain boundaries. Both, experiments and discrete dislocation simulations show that dislocations cross the neutral fiber. This feature is discussed in light of the limits of continuum descriptions of plasticity. © 2022 The Author(s). Published by IOP Publishing Ltd.
    view abstractdoi: 10.1088/1361-651X/ac4d77
  • 2022 • 224 Influence of the cutting edge on the surface integrity in BTA deep hole drilling-part 2: Residual stress, microstructure and microhardness
    Strodick, S. and Schmidt, R. and Biermann, D. and Zabel, A. and Walther, F.
    Procedia CIRP 108 276-281 (2022)
    doi: 10.1016/j.procir.2022.03.047
  • 2022 • 223 Innovative X-ray diffraction and micromagnetic approaches for reliable residual stress assessment in deep rolled and microfinished AISI 4140 components
    Strodick, S. and Vogel, F. and Tilger, M. and Denstorf, M. and Kipp, M. and Baak, N. and Kukui, D. and Biermann, D. and Barrientos, M.M. and Walther, F.
    Journal of Materials Research and Technology 20 2942-2959 (2022)
    doi: 10.1016/j.jmrt.2022.07.168
  • 2022 • 222 Reliable surface integrity characterization of bores [Gezielte Oberflächenkonditionierung beim BTA-Tiefbohren Mikromagnetische Charakteri-sierung der Bohrungsintegrität]
    Strodick, S. and Schmidt, R. and Brause, L. and Zabel, A. and Biermann, D. and Walther, F.
    WT Werkstattstechnik 112 757-761 (2022)
    doi: 10.37544/1436-4980-2022-11-12-31
  • 2022 • 221 Discovery of High-Entropy Oxide Electrocatalysts: From Thin-Film Material Libraries to Particles
    Strotkötter, V. and Krysiak, O.A. and Zhang, J. and Wang, X. and Suhr, E. and Schuhmann, W. and Ludwig, Al.
    Chemistry of Materials 34 10291-10303 (2022)
    doi: 10.1021/acs.chemmater.2c01455
  • 2022 • 220 Spin pumping at interfaces with ferro- and paramagnetic Fe60Al40films acting as spin source and spin sink
    Strusch, T. and Lenz, K. and Meckenstock, R. and Bali, R. and Ehrler, J. and Lindner, J. and Fassbender, J. and Farle, M. and Potzger, K. and Semisalova, A.
    Journal of Applied Physics 132 (2022)
    doi: 10.1063/5.0125699
  • 2022 • 219 Proteome-Based Clustering Approaches Reveal Phylogenetic Insights into Amphistegina
    Stuhr, M. and Blank-Landeshammer, B. and Meyer, A. and Baumeister, V. and Rahnenführer, J. and Sickmann, A. and Westphal, H.
    Journal of Earth Science (2022)
    Foraminifera are highly diverse and have a long evolutionary history. As key bioindicators, their phylogenetic schemes are of great importance for paleogeographic applications, but may be hard to recognize correctly. The phylogenetic relationships within the prominent genus Amphistegina are still uncertain. Molecular studies on Amphistegina have so far only focused on genetic diversity within single species and suggested a cryptic diversity that demands for further investigations. Besides molecular sequencing-based approaches, different mass spectrometry-based proteomics approaches are increasingly used to give insights into the relationship between samples and organisms, especially as these do not require reference databases. To better understand the relationship of amphisteginids and test different proteomics-based approaches we applied de novo peptide sequencing and similarity clustering to several populations of Amphistegina lobifera, A. lessonii and A. gibbosa. We also analyzed the dominant photosymbiont community to study their influence on holobiont proteomes. Our analyses indicate that especially de novo peptide sequencing allows to reconstruct the relationship among foraminiferal holobionts, although the detected separation of A. gibbosa from A. lessonii and A. lobifera may be partly influenced by their different photosymbiont types. The resulting dendrograms reflect the separation in two lineages previously suggested and provide a basis for future studies. © 2022, China University of Geosciences (Wuhan) and Springer-Verlag GmbH Germany, Part of Springer Nature.
    view abstractdoi: 10.1007/s12583-022-1609-1
  • 2022 • 218 The AlMo0.5NbTa0.5TiZr refractory high entropy superalloy: Experimental findings and comparison with calculations using the CALPHAD method
    Suárez Ocaño, P. and Fries, S.G. and Lopez-Galilea, I. and Darvishi Kamachali, R. and Roik, J. and Agudo Jácome, L.
    Materials and Design 217 (2022)
    doi: 10.1016/j.matdes.2022.110593
  • 2022 • 217 Application of Design of Experiments for Catalytic Oxygen Removal over Pt/γ-Al2O3 Catalyst
    Suh, S.Y. and Geitner, C. and Hänel, M. and Wiesmann, T. and Watermann, C.M. and Lohmann, H. and Apfel, U.-P. and Zeidler-Fandrich, B.
    Chemie-Ingenieur-Technik 94 1509-1515 (2022)
    doi: 10.1002/cite.202200035
  • 2022 • 216 Process Monitoring of a Vibration Dampening CFRP Drill Tube in BTA deep hole drilling using Fibre-Bragg-Grating Sensors
    Summa, J. and Michel, S. and Kurkowski, M. and Biermann, D. and Stommel, M. and Herrmann, H.-G.
    Procedia CIRP 115 119-124 (2022)
    doi: 10.1016/j.procir.2022.10.060
  • 2022 • 215 Thermodynamics-guided alloy and process design for additive manufacturing
    Sun, Z. and Ma, Y. and Ponge, D. and Zaefferer, S. and Jägle, E.A. and Gault, B. and Rollett, A.D. and Raabe, D.
    Nature Communications 13 (2022)
    In conventional processing, metals go through multiple manufacturing steps including casting, plastic deformation, and heat treatment to achieve the desired property. In additive manufacturing (AM) the same target must be reached in one fabrication process, involving solidification and cyclic remelting. The thermodynamic and kinetic differences between the solid and liquid phases lead to constitutional undercooling, local variations in the solidification interval, and unexpected precipitation of secondary phases. These features may cause many undesired defects, one of which is the so-called hot cracking. The response of the thermodynamic and kinetic nature of these phenomena to high cooling rates provides access to the knowledge-based and tailored design of alloys for AM. Here, we illustrate such an approach by solving the hot cracking problem, using the commercially important IN738LC superalloy as a model material. The same approach could also be applied to adapt other hot-cracking susceptible alloy systems for AM. © 2022, The Author(s).
    view abstractdoi: 10.1038/s41467-022-31969-y
  • 2022 • 214 Structural changes across thermodynamic maxima in supercooled liquid tellurium: A water-like scenario
    Sun, P. and Monaco, G. and Zalden, P. and Sokolowski-Tinten, K. and Antonowicz, J. and Sobierajski, R. and Kajihara, Y. and Baron, A.Q.R. and Fuoss, P. and Chuang, A.C. and Park, J.-S. and Almer, J. and Hastings, J.B.
    Proceedings of the National Academy of Sciences of the United States of America 119 (2022)
    Liquid polymorphism is an intriguing phenomenon that has been found in a few single-component systems, the most famous being water. By supercooling liquid Te to more than 130 K below its melting point and performing simultaneous small-angle and wide-angle X-ray scattering measurements, we observe clear maxima in its thermodynamic response functions around 615 K, suggesting the possible existence of liquid polymorphism. A close look at the underlying structural evolution shows the development of intermediate-range order upon cooling, most strongly around the thermodynamic maxima, which we attribute to bond-orientational ordering. The striking similarities between our results and those of water, despite the lack of hydrogen-bonding and tetrahedrality in Te, indicate that water-like anomalies may be a general phenomenon among liquid systems with competing bond- and density-ordering. Copyright © 2022 the Author(s). Published by PNAS. This article is distributed under Creative Commons Attribution-NonCommercial-NoDerivatives License 4.0 (CC BY-NC-ND).
    view abstractdoi: 10.1073/pnas.2202044119
  • 2022 • 213 Maintaining Antibacterial Activity against Biofouling Using a Quaternary Ammonium Membrane Coupling with Electrorepulsion
    Sun, J. and Zhang, B. and Yu, B. and Ma, B. and Hu, C. and Ulbricht, M. and Qu, J.
    Environmental Science and Technology (2022)
    doi: 10.1021/acs.est.2c08707
  • 2022 • 212 Physical metallurgy of medium-Mn advanced high-strength steels
    Sun, B. and Kwiatkowski da Silva, A. and Wu, Y. and Ma, Y. and Chen, H. and Scott, C. and Ponge, D. and Raabe, D.
    International Materials Reviews (2022)
    doi: 10.1080/09506608.2022.2153220
  • 2022 • 211 Temperature and Strain Rate Effects on the Uniaxial Tensile Behaviour of ETFE Foils
    Surholt, F. and Uhlemann, J. and Stranghöner, N.
    Polymers 14 (2022)
    With the first use of ETFE foils in building structures in the 1980s at the Burgers’ Zoo in Arnhem, Netherlands, the implementation of ETFE foils in roof and façade systems in large-span structures has become steadily more prominent. To safely design ETFE foil structures, their mechanical behaviour has to be fundamentally understood. Until now, several research studies have been published investigating this material’s behaviour. However, the parameters influencing these plastic’s mechanical behaviour, such as the strain rate or the test temperature, have only been investigated separately but not simultaneously. In this contribution, an analytical model is presented which describes the mechanical behaviour of ETFE foils under varying test temperatures and strain rates simultaneously. The material model has been checked against experimental results achieved for materials from three different international producers and two different commonly used foil thicknesses with significant differences in their mechanical responses (so that it can be assumed that the international market is represented). In the first step, uniaxial tensile tests on strip specimens were performed to describe the nonlinear and viscoelastic temperature- and strain rate-dependent material behaviour under uniaxial tension. The achieved stress-strain curves exhibited, as expected, the two commonly so-called yield points, which can be taken as separators for three different material stages: viscoelastic, viscoelastic-plastic, and viscoplastic. In the second step, by separating the uniaxial tensile response into these three stages, two interdependent functions could be derived based on the well-known Ramberg-Osgood material model to simulate the viscoelastic and viscoelastic-plastic material behaviour of ETFE foils. For this purpose, analytical functions were developed to calculate the model parameters considering the influence of the test temperature and the test speed. It can be shown that the newly developed analytical material model fits well with the experimental results. With the use of the derived nonlinear material model, design engineers can predict the material’s mechanical behaviour considering the environmental conditions on site while maintaining independence from the material’s supplier. © 2022 by the authors.
    view abstractdoi: 10.3390/polym14153156
  • 2022 • 210 Mechanical-technological behaviour of ETFE foils and their welded connections [Mechanisch-technologisches Verhalten von ETFE-Folien und deren Schweißverbindungen]
    Surholt, F. and Runge, D. and Uhlemann, J. and Stranghöner, N.
    Stahlbau 91 513-523 (2022)
    Mechanical-technological behaviour of ETFE foils and their welded connections. The thermoplastic fluoropolymer ethylene/tetrafluoroethylene, ETFE, has been increasingly used in membrane structures in the construction industry since the 1980s. The plastic ETFE exhibits a nonlinear, viscoelastic material behaviour that has not yet been fully investigated. However, when building membrane structures with ETFE foils, knowledge of the nonlinear, viscoelastic material behaviour is essential in order to be able to build wide, open and at the same time safe and economical structures. The material behaviour can be divided into short-term tensile behaviour and long-term behaviour, both under monoaxial and biaxial stresses. For the assembly of the surface structures, welding of the individual cut length is essential, since the basic material is only available in limited product widths. So far, there have only been a few studies on the load-bearing behaviour of welded ETFE foils. This article provides a brief overview of the material behaviour of ETFE foils in short-term tensile tests as well as long-term tests in monoaxial and biaxial stress conditions. In addition, material models are presented which describe the material behaviour in the above-mentioned tests or stress-states. Furthermore, first insights into the fracture behaviour of welded ETFE foils are given. © 2022, Ernst und Sohn. All rights reserved.
    view abstractdoi: 10.1002/stab.202200039
  • 2022 • 209 Slotted Y-branch laser for cw-THz thickness measurements at 1 THz
    Surkamp, N. and Gerling, A. and OGorman, J. and Honsberg, M. and Schmidtmann, S. and Nandi, U. and Preu, S. and Sacher, J. and Brenner, C. and Hofmann, M.R.
    Proceedings of SPIE - The International Society for Optical Engineering 12021 (2022)
    doi: 10.1117/12.2609787
  • 2022 • 208 A pressure-jump study on the interaction of osmolytes and crowders with cubic monoolein structures
    Surmeier, G. and Paulus, M. and Schneider, E. and Dogan, S. and Tolan, M. and Nase, J.
    Soft Matter 18 990-998 (2022)
    Many vital processes that take place in biological cells involve remodeling of lipid membranes. These processes take place in a milieu that is packed with various solutes, ranging from ions and small organic osmolytes to proteins and other macromolecules, occupying about 30% of the available volume. In this work, we investigated how molecular crowding, simulated with the polymer polyethylene glycol (PEG), and the osmolytes urea and trimethylamine-N-oxide (TMAO) affect the equilibration of cubic monoolein structures after a phase transition from a lamellar state induced by an abrupt pressure reduction. In absence of additives, swollen cubic crystallites form after the transition, releasing excess water over several hours. This process is reflected in a decreasing lattice constant and was monitored with small angle X-ray scattering. We found that the osmotic pressure exerted by PEG and TMAO, which are displaced from narrow inter-bilayer spaces, accelerates the equilibration. When the radius of gyration of the added PEG was smaller than the radius of the water channels of the cubic phase, the effect became more pronounced with increasing molecular weight of the polymers. As the release of hydration water from the cubic structures is accompanied by an increasing membrane curvature and a reduction of the interface between lipids and aqueous phase, urea, which has a slight affinity to reside near membrane surfaces, stabilized the swollen crystallites and slowed down the equilibration dynamics. Our results support the view that cellular solutes are important contributors to dynamic membrane processes, as they can accelerate dehydration of inter-bilayer spaces and promote or counteract membrane curvature. This journal is © The Royal Society of Chemistry.
    view abstractdoi: 10.1039/d1sm01425k
  • 2022 • 207 The interaction of viral fusion peptides with lipid membranes
    Surmeier, G. and Dogan-Surmeier, S. and Paulus, M. and Albers, C. and Latarius, J. and Sternemann, C. and Schneider, E. and Tolan, M. and Nase, J.
    Biophysical Journal 121 3811-3825 (2022)
    In this paper, we studied fusogenic peptides of class I-III fusion proteins, which are relevant to membrane fusion for certain enveloped viruses, in contact with model lipid membranes. We resolved the vertical structure and examined the adsorption or penetration behavior of the fusogenic peptides at phospholipid Langmuir monolayers with different initial surface pressures with x-ray reflectometry. We show that the fusion loops of tick-borne encephalitis virus (TBEV) glycoprotein E and vesicular stomatitis virus (VSV) G-protein are not able to insert deeply into model lipid membranes, as they adsorbed mainly underneath the headgroups with only limited penetration depths into the lipid films. In contrast, we observed that the hemagglutinin 2 fusion peptide (HA2-FP) and the VSV-transmembrane domain (VSV-TMD) can penetrate deeply into the membranes. However, in the case of VSV-TMD, the penetration was suppressed already at low surface pressures, whereas HA2-FP was able to insert even into highly compressed films. Membrane fusion is accompanied by drastic changes of the membrane curvature. To investigate how the peptides affect the curvature of model lipid membranes, we examined the effect of the fusogenic peptides on the equilibration of cubic monoolein structures after a phase transition from a lamellar state induced by an abrupt hydrostatic pressure reduction. We monitored this process in presence and absence of the peptides with small-angle x-ray scattering and found that HA2-FP and VSV-TMD drastically accelerate the equilibration, while the fusion loops of TBEV and VSV stabilize the swollen state of the lipid structures. In this work, we show that the class I fusion peptide of HA2 penetrates deeply into the hydrophobic region of membranes and is able to promote and accelerate the formation of negative curvature. In contrast, we found that the class II and III fusion loops of TBEV and VSV tend to counteract negative membrane curvature. © 2022 Biophysical Society
    view abstractdoi: 10.1016/j.bpj.2022.09.011
  • 2022 • 206 Structural Insights into Hysteretic Spin-Crossover in a Set of Iron(II)-2,6-bis(1H-Pyrazol-1-yl)Pyridine) Complexes
    Suryadevara, N. and Mizuno, A. and Spieker, L. and Salamon, S. and Sleziona, S. and Maas, A. and Pollmann, E. and Heinrich, B. and Schleberger, M. and Wende, H. and Kuppusamy, S.K. and Ruben, M.
    Chemistry - A European Journal 28 (2022)
    Bistable spin-crossover (SCO) complexes that undergo abrupt and hysteretic (ΔT1/2) spin-state switching are desirable for molecule-based switching and memory applications. In this study, we report on structural facets governing hysteretic SCO in a set of iron(II)-2,6-bis(1H-pyrazol-1-yl)pyridine) (bpp) complexes – [Fe(bpp−COOEt)2](X)2⋅CH3NO2 (X=ClO4, 1; X=BF4, 2). Stable spin-state switching – T1/2=288 K; ΔT1/2=62 K – is observed for 1, whereas 2 undergoes above-room-temperature lattice-solvent content-dependent SCO – T1/2=331 K; ΔT1/2=43 K. Variable-temperature single-crystal X-ray diffraction studies of the complexes revealed pronounced molecular reorganizations – from the Jahn-Teller-distorted HS state to the less distorted LS state – and conformation switching of the ethyl group of the COOEt substituent upon SCO. Consequently, we propose that the large structural reorganizations rendered SCO hysteretic in 1 and 2. Such insights shedding light on the molecular origin of thermal hysteresis might enable the design of technologically relevant molecule-based switching and memory elements. © 2021 The Authors. Chemistry - A European Journal published by Wiley-VCH GmbH
    view abstractdoi: 10.1002/chem.202103853
  • 2022 • 205 Gröbner bases plugged into graphical skills to solve a set of multiple bifurcation equations in structural compound stability problems
    Tanaka, M. and Matsubara, S. and Schröder, J. and Fujii, F.
    International Journal for Numerical Methods in Engineering 123 5779-5800 (2022)
    A core issue in structural multiple bifurcations (MB) in computational engineering is to identify all existing branching paths emanating from the MB point in compound stability problems. The governing MB equations (MBEs) will commonly result in a set of three (or occasionally two) polynomial equations in asymptotic stability theory when the singular stiffness matrix is subject to a rank deficiency of two (i.e., two null eigenvalues). However, no general solution strategy has been established to solve MBEs so far. This study proposes innovative graphical solution ideas to intuitively visualize multiple path branching in 2D- and 3D-spaces of variables. Although the graphical skills display real solutions in specified search areas on a graphical monitor, it is not assured that “all” real roots are detected. The total number of identified real and complex roots of simultaneous equations must be generally consistent with that predicted algebraically to ensure that all real and complex roots are captured in MB. In computational algebra, Gröbner bases are employed to convert a set of polynomial equations into single recursively solvable equations and can be plugged into visualization steps. Therefore, Gröbner bases and graphical skills are complementary and can be applied to numerically solve a set of plate/shell structural MBEs. © 2022 John Wiley & Sons, Ltd.
    view abstractdoi: 10.1002/nme.7088
  • 2022 • 204 Magnetic phase diagram of (Mo2/3RE1/3)2AlC, RE = Tb and Dy, studied by magnetization, specific heat, and neutron diffraction analysis
    Tao, Q. and Barbier, M. and Mockute, A. and Ritter, C. and Salikhov, R. and Wiedwald, U. and Calder, S. and Opagiste, C. and Galera, R.-M. and Farle, M. and Ouisse, T. and Rosen, J.
    Journal of Physics Condensed Matter 34 (2022)
    doi: 10.1088/1361-648X/ac5bcf
  • 2022 • 203 Asymmetric interfaces in epitaxial off-stoichiometric Fe3+x Si1−x /Ge/Fe3+x Si1−x hybrid structures: Effect on magnetic and electric transport properties
    Tarasov, A.S. and Tarasov, I.A. and Yakovlev, I.A. and Rautskii, M.V. and Bondarev, I.A. and Lukyanenko, A.V. and Platunov, M.S. and Volochaev, M.N. and Efimov, D.D. and Goikhman, A.Yu. and Belyaev, B.A. and Baron, F.A. and Shanid...
    Nanomaterials 12 (2022)
    Three-layer iron-rich Fe3+x Si1−x /Ge/Fe3+x Si1−x (0.2 &lt; x &lt; 0.64) heterostructures on a Si(111) surface with Ge thicknesses of 4 nm and 7 nm were grown by molecular beam epitaxy. Systematic studies of the structural and morphological properties of the synthesized samples have shown that an increase in the Ge thickness causes a prolonged atomic diffusion through the interfaces, which significantly increases the lattice misfits in the Ge/Fe3+x Si1−x heterosystem due to the incorporation of Ge atoms into the Fe3+x Si1−x bottom layer. The resultant lowering of the total free energy caused by the development of the surface roughness results in a transition from an epitaxial to a polycrystalline growth of the upper Fe3+x Si1−x. The average lattice distortion and residual stress of the upper Fe3+x Si1−x were determined by electron diffraction and theoretical calculations to be equivalent to 0.2 GPa for the upper epitaxial layer with a volume misfit of −0.63% compared with a undistorted counterpart. The volume misfit follows the resultant interatomic misfit of |0.42|% with the bottom Ge layer, independently determined by atomic force microscopy. The variation in structural order and morphology significantly changes the magnetic properties of the upper Fe3+x Si1−x layer and leads to a subtle effect on the transport properties of the Ge layer. Both hysteresis loops and FMR spectra differ for the structures with 4 nm and 7 nm Ge layers. The FMR spectra exhibit two distinct absorption lines corresponding to two layers of ferromagnetic Fe3+x Si1−x films. At the same time, a third FMR line appears in the sample with the thicker Ge. The angular dependences of the resonance field of the FMR spectra measured in the plane of the film have a pronounced easy-axis type anisotropy, as well as an anisotropy corresponding to the cubic crystal symmetry of Fe3+x Si1−x, which implies the epitaxial orientation relationship of Fe3+x Si1−x (111)[0−11] || Ge(111)[1−10] || Fe3+x Si1−x (111)[0−11] || Si(111)[1−10]. Calculated from ferromagnetic resonance (FMR) data saturation magnetization exceeds 1000 kA/m. The temperature dependence of the electrical resistivity of a Ge layer with thicknesses of 4 nm and 7 nm is of semiconducting type, which is, however, determined by different transport mechanisms. © 2021 by the authors. Licensee MDPI, Basel, Switzerland.
    view abstractdoi: 10.3390/nano12010131
  • 2022 • 202 3D-Printed Metallic Helix Antennas for Orientation Insensitive Polarization-division Multiplexing at Terahertz Frequencies
    Tebart, J. and Stohr, A. and Klein, A.K.
    International Conference on Infrared, Millimeter, and Terahertz Waves, IRMMW-THz 2022-August (2022)
    The improvements in 3D-printing increasingly enable their use for Terahertz components. Here we present helical antennas integrated with WR3 rectangular waveguides produced by a 3D metal printer. The constrains in resolution forces the design to deviate from the ideal dimensions for gain, but the flexibility of the production technique allows for the integration of reflector dishes directly on the waveguide, which mitigates these effects. Despite the deviation from traditional helical antenna design rules, the circular polarization is maintained. Hence, this fabrication method delivers orientation insensitive antennas for polarization-division multiplexing. © 2022 IEEE.
    view abstractdoi: 10.1109/IRMMW-THz50927.2022.9895589
  • 2022 • 201 Numerical simulation of real gas one-component two-phase flow using a Roe-based scheme
    Tegethoff, K. and Schuster, S. and Brillert, D.
    Computers and Fluids 245 (2022)
    doi: 10.1016/j.compfluid.2022.105560
  • 2022 • 200 High-pressure CO, H2, CO2 and Ethylene Pulses Applied in the Hydrogenation of CO to Higher Alcohols over a Bulk Co-Cu Catalyst
    Telaar, P. and Schwiderowski, P. and Schmidt, S. and Stürmer, S. and Muhler, M.
    ChemCatChem 14 (2022)
    The reaction pathways of higher alcohol synthesis over a bulk Co−Cu catalyst (Co : Cu=2 : 1) were investigated by applying high-pressure pulse experiments as a surface-sensitive operando method at 280 °C and 60 bar. Using high-pressure CO and H2 pulses in a syngas flow with a H2:CO ratio of 1, it was shown that the surface of the working 2CoCu catalyst is saturated with adsorbed CO, but not with adsorbed atomic hydrogen, because only the H2 pulses increased the yields of all alcohols and alkanes. The reverse water gas shift reaction (WGSR) was investigated by pulsing CO2. The CO2 pulses poisoned the formation of methanol, ethanol, and 1-propanol, and the absence of significant CO and H2O responses indicates that the WGSR is not efficiently catalyzed by the applied 2CoCu catalyst excluding the presence of exposed Cu0 sites. A series of ethylene pulses showed that when a threshold mole fraction of ethylene of about 1 vol % is surpassed, 2CoCu is an active catalyst for the hydroformylation of ethylene to 1-propanol pointing to the presence of highly coordinatively unsaturated Co sites. © 2022 The Authors. ChemCatChem published by Wiley-VCH GmbH.
    view abstractdoi: 10.1002/cctc.202200385
  • 2022 • 199 Characterization of the high-temperature behavior of PBF-EB/M manufactured γ titanium aluminides
    Teschke, M. and Moritz, J. and Telgheder, L. and Marquardt, A. and Leyens, C. and Walther, F.
    Progress in Additive Manufacturing (2022)
    Due to their high specific strength and temperature resistance, γ-titanium aluminides (γ-TiAl) have a growing importance for automotive and aerospace applications. However, conventional processing is very challenging due to the inherent brittleness of the material. Therefore, new manufacturing techniques and methods have to be established. Additive manufacturing techniques such as electron powder bed fusion (PBF-EB/M) are favored, since they enable near net shape manufacturing of highly complex geometries. The high preheating temperatures, which typically occur during PBF-EB/M, can significantly improve the processability of TiAl and facilitate the fabrication of complex parts. In this study, a previously optimized material condition of the β-solidifying TNM alloy TNM-B1 (Ti-43.5Al-4Nb-1Mo-0.1B) was manufactured by PBF-EB/M. The resulting microstructure, defect distribution and morphology, and mechanical properties were characterized by means of characterization methods, e.g., CT, SEM, light microscopy, hardness measurements, and tensile tests. A special focus was on the mechanical high-temperature behavior. The pronounced sensitivity of the material to defects and internal notches, e.g., due to lack of fusion defects (misconnections) which were found in the as-built condition, was identified as a main cause for premature failure below the yield point due to the low ductility. This failure was analyzed and potential improvements were identified. © 2022, The Author(s).
    view abstractdoi: 10.1007/s40964-022-00274-x
  • 2022 • 198 Defect-based characterization of the fatigue behavior of additively manufactured titanium aluminides
    Teschke, M. and Moritz, J. and Tenkamp, J. and Marquardt, A. and Leyens, C. and Walther, F.
    International Journal of Fatigue 163 (2022)
    The additively manufactured titanium aluminide alloy TNM-B1 was characterized microstructurally and mechanically in the as-built and hot isostatically pressed (HIP) condition. Tensile and constant amplitude tests were performed at room temperature and 800 °C. Using fractographic SEM images, the fracture-inducing defect was identified. With the HIP, defect number and size could be reduced, increasing fatigue strength by 43% to 500 MPa. Using the model approaches of Murakami and Shiozawa, the fatigue life was correlated with the local stress intensity factor and could be described as function of the stress amplitude as well as the size and location of fracture-inducing defects. © 2022 Elsevier Ltd
    view abstractdoi: 10.1016/j.ijfatigue.2022.107047
  • 2022 • 197 Linear response for pseudo-Hermitian Hamiltonian systems: Application to PT -symmetric qubits
    Tetling, L. and Fistul, M.V. and Eremin, I.M.
    Physical Review B 106 (2022)
    doi: 10.1103/PhysRevB.106.134511
  • 2022 • 196 [NiFe]-(Oxy)Sulfides Derived from NiFe2O4 for the Alkaline Hydrogen Evolution Reaction
    Tetzlaff, D. and Alagarasan, V. and Simon, C. and Siegmund, D. and Puring, K.J. and Marschall, R. and Apfel, U.-P.
    Energies 15 (2022)
    The development of noble-metal-free electrocatalysts is regarded as a key factor for realizing industrial-scale hydrogen production powered by renewable energy sources. Inspired by nature, which uses Fe-and Ni-containing enzymes for efficient hydrogen generation, Fe/Ni-containing chalcogenides, such as oxides and sulfides, received increasing attention as promising electrocatalysts to produce hydrogen. We herein present a novel synthetic procedure for mixed Fe/Ni (oxy)sulfide materials by the controlled (partial) sulfidation of NiFe2O4 (NFO) nanoparticles in H2S-containing atmospheres. The variation in H2S concentration and the temperature allows for a precise control of stoichiometry and phase composition. The obtained sulfidized materials (NFS) catalyze the hydrogen evolution reaction (HER) with increased activity in comparison to NFO, up to −10 and −100 mA cm−2 at an overpotential of approx. 250 and 450 mV, respectively. © 2022 by the authors. Licensee MDPI, Basel, Switzerland.
    view abstractdoi: 10.3390/en15020543
  • 2022 • 195 Ti-Si-B-C-N plasma enhanced chemical vapor deposition nanocomposite coatings for high temperature applications
    Thewes, A. and Bröcker, L. and George, E.T.K. and Bräuer, G. and Paulus, M. and Sternemann, C. and Paschke, H. and Brückner, T. and Lechner, S. and Müller, S.
    Thin Solid Films 760 (2022)
    With increased demands for service lifetime of tools in hot forming applications, e.g. hot extrusion and die-casting, surface modifications of hot working steels are necessary to improve the surface's thermal stability and oxidation resistance. The machining of aluminum and copper is especially challenging, considering its tendency to stick at the tools’ surface, which is increasingly impactful at elevated temperatures. Developing Ti-Si-B-C-(N) nanocomposite coatings with plasma-enhanced chemical vapor deposition is a promising approach to overcome these deficiencies, because, with an adequate Si-content, thermal stability and oxidation resistance can be increased by forming a thin, amorphous Si3N4 tissue layer between the nanocrystalline grains of the coating. In this study, the influence of nitrogen on the coatings’ thermal properties is under investigation for N-content in the range between 0.0 at.-% and 14.6 at.-%. Different oxidation resistance in dependence of the N-content was observed at high temperatures (T = 750-900 °C) in-situ by X-ray diffraction in air. The multiphase coatings form compositionally complex nanostructures with an average grain size of ca. 4 to 7 nm. The hardness is strongly affected by nanocomposite structure and residual elements like O and Cl incorporated during coating deposition, whereas the influence of N-content on Ti-Si-B-C-(N) coatings is less significant regarding mechanical properties. Considering the thermal properties, the N-content has been proven to be of central importance. Oxidation was observed in the range between 800 °C and 900 °C, underlining the possible application as protective coating for hot forming tools. © 2022
    view abstractdoi: 10.1016/j.tsf.2022.139507
  • 2022 • 194 Multifunctional Organocatalysts - Singly-Linked and Macrocyclic Bisphosphoric Acids for Asymmetric Phase-Transfer and Brønsted-Acid Catalysis
    Thiele, M. and Rose, T. and Lõkov, M. and Stadtfeld, S. and Tshepelevitsh, S. and Parman, E. and Opara, K. and Wölper, C. and Leito, I. and Grimme, S. and Niemeyer, J.
    Chemistry - A European Journal (2022)
    The linking of phosphoric acids via covalent or mechanical bonds has proven to be a successful strategy for the design of novel organocatalysts. Here, we present the first systematic investigation of singly-linked and macrocyclic bisphosphoric acids, including their synthesis and their application in phase-transfer and Brønsted acid catalysis. We found that the novel bisphosphoric acids show dramatically increased enantioselectivities in comparison to their monophosphoric acid analogues. However, the nature, length and number of linkers has a profound influence on the enantioselectivities. In the asymmetric dearomative fluorination via phase-transfer catalysis, bisphosphoric acids with a single, rigid bisalkyne-linker give the best results with moderate to good enantiomeric excesses. In contrast, bisphosphoric acids with flexible linkers give excellent enantioselectivities in the transfer-hydrogenation of quinolines via cooperative Brønsted acid catalysis. In the latter case, sufficiently long linkers are needed for high stereoselectivities, as found experimentally and supported by DFT calculations. © 2022 The Authors. Chemistry - A European Journal published by Wiley-VCH GmbH.
    view abstractdoi: 10.1002/chem.202202953
  • 2022 • 193 Ultrafast transport-mediated homogenization of photoexcited electrons governs the softening of the A1g phonon in bismuth
    Thiemann, F. and Sciaini, G. and Kassen, A. and Hagemann, U. and Meyer Zu Heringdorf, F. and Horn-Von Hoegen, M.
    Physical Review B 106 (2022)
    doi: 10.1103/PhysRevB.106.014315
  • 2022 • 192 In-flight detection of few electrons using a singlet-triplet spin qubit
    Thiney, V. and Mortemousque, P.-A. and Rogdakis, K. and Thalineau, R. and Ludwig, Ar. and Wieck, A.D. and Urdampilleta, M. and Bäuerle, C. and Meunier, T.
    Physical Review Research 4 (2022)
    doi: 10.1103/PhysRevResearch.4.043116
  • 2022 • 191 Cratering Induced by Slow Highly Charged Ions on Ultrathin PMMA Films
    Thomaz, R.S. and Ernst, P. and Grande, P.L. and Schleberger, M. and Papaléo, R.M.
    Atoms 10 (2022)
    doi: 10.3390/atoms10040096
  • 2022 • 190 Crystallographic Analysis of Plate and Lath Martensite in Fe-Ni Alloys
    Thome, P. and Schneider, M. and Yardley, V.A. and Payton, E.J. and Eggeler, G.
    Crystals 12 (2022)
    In the present work, we use an advanced EBSD method to analyze the two prominent types of martensite microstructures that are found in the binary Fe-Ni system, lath martensite (27.5 at.% Ni) and plate martensite (29.5 at.% Ni). We modify, document, and apply an analytical EBSD procedure, which was originally proposed by Yardley and Payton, 2014. It analyzes the distributions of the three KSI-angles (ξ1, ξ2, and ξ3, KSI after Kurdjumov and Sachs), which describe small angular deviations between crystal planes in the unit cells of martensite and austenite—which are related through specific orientation relationships. The analysis of the angular distributions can be exploited to obtain high-resolution, color-coded micrographs of martensitic microstructures, which, for example, visualize the difference between lath and plate martensite and appreciate the microstructural features, like midribs in large plate martensite crystals. The differences between the two types of martensite also manifest themselves in different distributions of the KSI-angles (wider for lath and narrower for plate martensite). Finally, our experimental results prove that local distortions result in scatter, which is larger than the differences between the orientation relationships of Kurdjumov/Sachs, Nishiyama/Wassermann, and Greninger/Troiano. © 2022 by the authors. Licensee MDPI, Basel, Switzerland.
    view abstractdoi: 10.3390/cryst12020156
  • 2022 • 189 Wake Effects on Wave-Induced Loads Acting on Cylinders in a Tripod Configuration
    Thome, M. and el Moctar, O. and Schellin, T.E.
    Journal of Marine Science and Engineering 10 (2022)
    doi: 10.3390/jmse10091211
  • 2022 • 188 WAVE-INDUCED LOADS ACTING ON MONOPILE CONFIGURATIONS CONSIDERING WAKE EFFECTS
    Thome, M. and el Moctar, O. and Schellin, T.
    Proceedings of the International Conference on Offshore Mechanics and Arctic Engineering - OMAE 5-B (2022)
    doi: 10.1115/OMAE2022-78835
  • 2022 • 187 HYDROGEN COMPRESSION - TOWARDS A NEW STRATEGY FOR THE DESIGN OF HYDROGEN COMPRESSORS
    Tiainen, J. and Turunen-Saaresti, T. and Mäki-Iso, M. and Schuster, S. and Brillert, D.
    Proceedings of the ASME Turbo Expo 10-B (2022)
    doi: 10.1115/GT2022-78626
  • 2022 • 186 Quantifying the Energy Losses in CsPbI2Br Perovskite Solar Cells with an Open-Circuit Voltage of up to 1.45 v
    Tian, J. and Zhang, K. and Xie, Z. and Peng, Z. and Zhang, J. and Osvet, A. and Lüer, L. and Kirchartz, T. and Rau, U. and Li, N. and Brabec, C.J.
    ACS Energy Letters 4071-4080 (2022)
    CsPbI2Br perovskite solar cells (PSCs) have attracted much interest because of their thermodynamic stability, relatively stable cubic perovskite phase, and their potential as a top cell for tandem applications. However, the open-circuit voltage (VOC) reported to date is in most cases well below the detailed balance (DB) limit for single-junction PSCs. Here, we demonstrate that adding lead acetate to the CsPbI2Br precursor allows us to substantially reduce losses due to nonradiative recombination. Corresponding champion devices reach a power conversion efficiency (-) of 16.7% and a highest VOC value of 1.45 V, which represents 90% of the DB limit for single-junction PSCs at a bandgap of 1.89 eV. In order to disentangle the nonradiative recombination loss mechanisms, we quantify the origin of energy losses by calculating the radiative limit of the open-circuit voltage (VOCrad) and the quasi-Fermi level splitting (QFLS) of perovskite films with and without other functional layers. We further analyze the strategies to reduce the residual losses in order to push the efficiency beyond the 90% theoretical limit. © 2022 American Chemical Society. All rights reserved.
    view abstractdoi: 10.1021/acsenergylett.2c01883
  • 2022 • 185 Rotationally Symmetric Lens Antenna with Biconical Feed for Broadband Measurement Applications
    Tian, Z. and Sievert, B. and Eube, M. and Hildenhagen, P. and Erni, D. and Rennings, A.
    2022 52nd European Microwave Conference, EuMC 2022 612-615 (2022)
    doi: 10.23919/EuMC54642.2022.9924442
  • 2022 • 184 The effect of argon as atomization gas on the microstructure, machine hammer peening post-treatment, and corrosion behavior of twin wire arc sprayed (Twas) znal4 coatings
    Tillmann, W. and Abdulgader, M. and Wirtz, A. and Milz, M.P. and Biermann, D. and Walther, F.
    Coatings 12 (2022)
    In the twin wire arc spraying (TWAS) process, it is common to use compressed air as atomizing gas. Nitrogen or argon also are used to reduce oxidation and improve coating performance. The heat required to melt the feedstock material depends on the electrical conductivity of the wires used and the ionization energy of both the feedstock material and atomization gas. In the case of ZnAl4, no phase changes were recorded in the obtained coatings by using either compressed air or argon as atomization gas. This fact has led to the assumption that the melting behavior of ZnAl4 with its low melting and evaporating temperature is different from materials with a higher melting point, such as Fe and Ni, which also explains the unexpected compressive residual stresses in the as-sprayed conditions. The heavier atomization gas, argon, led to slightly higher compressive stresses and oxide content. Compressed air as atomization gas led to lower porosity, decreased surface roughness, and better corrosion resistance. In the case of argon, Al precipitated in the form of small particles. The post-treatment machine hammer peening (MHP) has induced horizontal cracks in compressed air sprayed coatings. These cracks were mainly initiated in the oxidized Al phase. © 2021 by the authors. Licensee MDPI, Basel, Switzerland.
    view abstractdoi: 10.3390/coatings12010032
  • 2022 • 183 Qualification of the Low-pressure Cold Gas Spraying for the Additive Manufacturing of Copper–Nickel–Diamond Grinding Wheels
    Tillmann, W. and Zajaczkowski, J. and Baumann, I. and Kipp, M. and Biermann, D.
    Journal of Thermal Spray Technology 31 206-216 (2022)
    Grinding wheels are usually manufactured by powder metallurgical processes, i.e., by molding and sintering. Since this requires the production of special molds and the sintering is typically carried out in a continuous furnace, this process is time-consuming and cost-intensive. Therefore, it is only worthwhile for medium and large batches. Another influencing factor of the powder metallurgical process route is the high thermal load during the sintering process. Due to their high thermal sensitivity, superabrasives such as diamond or cubic boron nitride are very difficult to process in this way. In this study, a novel and innovative approach is presented, in which superabrasive grinding wheels are manufactured by thermal spraying. For this purpose, flat samples as well as grinding wheel bodies were coated by low-pressure (LP) cold gas spraying with a blend of a commercial Cu-Al2O3 cold gas spraying powder and nickel-coated diamonds. The coatings were examined metallographically in terms of their composition. A well-embedded superabrasive content of 12 % was achieved. After the spraying process, the grinding wheels were conditioned and tested for the grinding application of cemented carbides and the topographies of both the grinding wheel and the cemented carbide were evaluated. Surface qualities of the ground surface that are comparable to those of other finishing processes were reached. This novel process route offers great flexibility in the combination of binder and hard material as well as a cost-effective single-part and small-batch production. © 2021, The Author(s).
    view abstractdoi: 10.1007/s11666-021-01291-y
  • 2022 • 182 Rare-earth modified amorphous carbon films: Effects of erbium and gadolinium on the structural evolution and mechanical properties
    Tillmann, W. and Lopes Dias, N.F. and Stangier, D. and Berndt, J. and Klemme, S. and Kesper, L. and Berges, U. and Westphal, C. and Thomann, C.A. and Debus, J.
    Diamond and Related Materials 123 (2022)
    Modifying amorphous carbon (a-C) with rare-earth elements is a highly auspicious concept to synthetize functional films with unique characteristics. Among the rare earth elements, Er and Gd demonstrate abundant physicochemical properties and, hence, are of remarkable interest for the element modification of a-C films. Therefore, Er-containing a-C:Er and Gd-containing a-C:Gd films are prepared in a reactive-free magnetron sputtering process. The a-C:Er and a-C:Gd films have an amount of up to 5 at.-% Er and 4.8 at.-% Gd. High-resolution x-ray photoelectron spectroscopy analyses show the formation of Er[sbnd]C and Gd[sbnd]C components, which rise proportionally with increasing amount of the rare-earth element. The addition of Er and Gd lowers the sp3 content of C bonds. At the highest concentrations of the respective rare-earth elements, the a-C:Er and a-C:Gd films exhibit a reduced sp3 content of 8%. The number and size of sp2‑carbon clusters in the amorphous network are enhanced with increasing amount of Er and Gd which is evaluated by Raman scattering measurements. X-ray diffraction analyses reveal Er and Gd carbide phases, indicating the formation of a nanocomposite structure consisting of carbidic nanocrystallites and an a-C network. In nanoindentation tests, the non-modified a-C demonstrates a hardness of (21.7 ± 1.6) GPa and an elastic modulus of (232 ± 10) GPa. With increasing Er and Gd contents, the hardness linearly decreases to (16.7 ± 0.9) GPa and (14.8 ± 0.9) GPa, respectively. An analogous behavior is also identified for the elastic modulus. The reduced hardness and elastic modulus are attributed to the lower sp3 content and the larger number and size of the sp2-hybridized carbon atoms. Additionally, the adhesion was slightly improved by the addition of Er and Gd in comparison to non-modified a-C. © 2022 Elsevier B.V.
    view abstractdoi: 10.1016/j.diamond.2022.108898
  • 2022 • 181 Silicon- and tungsten-containing hydrogen-free and hydrogenated amorphous carbon films for friction-reducing applications
    Tillmann, W. and Wittig, A. and Dias, N.F.L. and Stangier, D. and Thomann, C.A. and Moldenhauer, H. and Debus, J.
    Diamond and Related Materials 123 (2022)
    For tribological applications, adding Si or W to hydrogen-free a-C or hydrogenated a-C:H is highly beneficial to tailor the film properties. Hence, a direct comparison between Si- and W-containing a-C and a-C:H considerably enhances the understanding of both the interaction between Si or W and the hydrogenation state as well as its effect on the structure and tribo-mechanical properties of these films. Therefore, non-modified a-C(:H), Si-containing a-C(:H):Si, and W-containing a-C(:H):W films were systematically grown in a mid-frequency magnetron sputtering process. The formation of W-based nanocrystallites within a-C(:H):W is identified by x-ray diffraction, whereas a-C(:H):Si still possesses an amorphous character. Raman scattering spectra show higher I(D)/I(G) ratios for hydrogen-free a-C(:X) films compared to the respective a-C(:H):X, indicating a higher number and larger sizes of sp2 clusters in the carbon network. For the hydrogenated a-C:H:X films, the reduced number of sp2 clusters is related to the presence of terminating C[sbnd]H bonds, which were detected as stretching modes. Among the different films, a-C:W has the highest I(D)/I(G) ratio, while a-C:H and a-C:H:Si exhibit the lowest I(D)/I(G) values. While a-C:Si and a-C:H:Si are characterized by comparable hardness values of (18.7 ± 1.3) and (18.4 ± 1.1) GPa, a-C:W has a lower hardness of (13.8 ± 1.0) GPa compared to a-C:H:W with (17.5 ± 0.9) GPa. Among all modified a-C(:H):X films, a-C:Si and a-C:H:Si reveal the lowest coefficients of friction, but show highest wear rates in dry sliding against 100Cr6 steel. Contrarily, a-C:W has higher friction and wear than a-C:H:W. Consequently, the Si-containing a-C(:H):Si films demonstrate comparable tribo-mechanical properties, while the hydrogenation state leads to different tribo-mechanical properties of a-C(:H):W. © 2022
    view abstractdoi: 10.1016/j.diamond.2022.108866
  • 2022 • 180 WC Decomposition Phenomena in ID-HVOF-Sprayed WC-CoCr Coatings Using Fine Powder Feedstock
    Tillmann, W. and Hagen, L. and Baumann, I. and Paulus, M.
    Coatings 12 (2022)
    Over the last few decades, the high velocity oxygen fuel (HVOF) spraying of WC-CoCr for internal diameter (ID) coating has attracted much interest for hard chrome replacement. Current demands for the ID coating of small cylindrical parts necessitates the use of specialized spray gun equipment and powder feedstocks with small particle size fractions. Due to the limited spray distance inside cylindrical parts with small IDs, the process control, spraying fine WC-CoCr powders, meets new challenges to avoid significant WC decomposition, which increases the risk of mechanical degradation. Within the scope of this study, ID-HVOF spraying using a fine-structured WC-CoCr (−15 + 5 µm) feedstock with a mean WC particle size of 400 nm is examined with respect to the WC decomposition phenomena using X-ray diffraction (XRD). Hence, a statistical design of experiments (DoE) is utilized to systematically analyze various spray parameter settings along with their interaction as part of the WC to W2C conversion. © 2022 by the authors. Licensee MDPI, Basel, Switzerland.
    view abstractdoi: 10.3390/coatings12020124
  • 2022 • 179 Adapting the Surface Integrity of High-Speed Steel Tools for Sheet-Bulk Metal Forming
    Tillmann, W. and Stangier, D. and Meijer, A. and Krebs, E. and Ott, A. and Platt, T. and Lopes Dias, N.F. and Hagen, L. and Biermann, D.
    Journal of Manufacturing and Materials Processing 6 (2022)
    doi: 10.3390/jmmp6020037
  • 2022 • 178 HiPIMS of MoS2 – Current-voltage characteristics
    Tillmann, W. and Wittig, A. and Stangier, D. and Thomann, C.-A. and Debus, J. and Aurich, D. and Bruemmer, A.
    Materials Letters 320 (2022)
    doi: 10.1016/j.matlet.2022.132340
  • 2022 • 177 Statistical Comparison of Processing Different Powder Feedstock in an HVOF Thermal Spray Process
    Tillmann, W. and Kuhnt, S. and Baumann, I.T. and Kalka, A. and Becker-Emden, E.-C. and Brinkhoff, A.
    Journal of Thermal Spray Technology 31 1476-1489 (2022)
    Cermet coatings such as WC-Co and Cr3C2-NiCr are frequently applied by means of thermal spray processes to protect highly stressed surfaces against wear. The investigation of the respective spray materials and their coating properties and in-flight particle properties are often carried out in separate experiments. In this study, the coating characteristics (hardness, deposition rate, porosity, thickness) and in-flight particle properties (particle velocity and temperature) of three different WC-based powders and a Cr3C2-NiCr powder processed by means of an HVOF process are investigated as a function of some key process parameters such as kerosene flow rate, lambda, spray distance and feeder disc velocity. These parameters were varied within a design of experiments, whilst all other parameters were fixed. Both the design of experiments plan and the settings of the fixed parameters were defined identically. The in-flight particle properties and coating characteristics are statistically modeled as a function of the process parameters and their influences are compared. A well-selected, limited number of experimental runs using statistical design of experiment (DoE) enable this comparison. The deployed statistical models are generalized linear models with Gamma-distributed responses. The models show that particle velocity and particle temperature mainly depend on kerosene flow rate and spray distance. However, in the case of particle temperature, the model coefficients for Cr3C2-NiCr and WC powders have different signs, reflecting different qualitative behavior. © 2022, The Author(s).
    view abstractdoi: 10.1007/s11666-022-01392-2
  • 2022 • 176 An investigation of the influence of integration of steel heat treatment and brazing process on the microstructure and performance of vacuum-brazed cemented carbide/steel joints
    Tillmann, W. and Ulitzka, T. and Dahl, L. and Wojarski, L. and Ulitzka, H.
    Welding in the World (2022)
    Cemented carbides are commonly brazed to transformation hardening tool steels without taking a proper and adequate steel heat treatment into account. This publication shows the limits and possibilities of integrating a steel heat treatment, including a quenching process, into a vacuum brazing process. Therefore, copper-based filler metals are selected to ensure the steel component’s high and homogenous hardness and supply a high joint quality. In this context, the aimed steel hardness was chosen in the range between 400 and 440 HV1 based on industrial experiences. This specific hardness range for the steel component was set to avoid wear of machining tools in subsequent machining steps if the steel hardness is too high and to prevent wear and deformation of the tool itself in case of a steel hardness too low. When using the transformation hardening tool steel 1.2344, the obtained shear strength values did not exceed a threshold of 20 MPa which can be attributed to the required N2-quenching from brazing respectively solution annealing temperature. However, the steel components featured a hardness of 527.1 HV1 for the specimens brazed with pure copper at 1100 °C and 494.0 HV1 for those brazed with a CuGeNi filler metal at 1040 °C. This publication also shows an alternative route to manufacture long-lasting tools with a cemented carbide/steel joint by applying the difficult to wet and not well researched, but for many other reasons very suitable precipitation hardening maraging steel. Especially, the comparable low coefficient of thermal expansion (CTE) and the capability of the lath martensite to compensate large amounts of externally imposed stresses during the austenite-to-martensite transformation as well as the cooling rate independent of the hardening mechanism of the maraging steel and a pre-applied nickel coating including the corresponding diffusion processes are responsible for a sound joint with a shear strength &gt; 300 MPa. Moreover, the subsequent tempering process at 580 °C for 3 h provides the maraging steel joining partner with a hardness of 426.6 ± 6.0 HV1. © 2022, The Author(s).
    view abstractdoi: 10.1007/s40194-022-01266-9
  • 2022 • 175 Effect of Ag Doping on the Microstructure and Electrochemical Response of TiAlN Coatings Deposited by DCMS/HiPIMS Magnetron Sputtering
    Tillmann, W. and Grisales, D. and Echavarría, A.M. and Calderón, J.A. and Gaitan, G.B.
    Journal of Materials Engineering and Performance (2022)
    Incorporation of silver particles in nitride coatings has been used to improve the mechanical resistance of steels, but few details are known about the effect of the incorporation of these metals on the electrochemical behavior. In order to evaluate the corrosion resistance and the possible formation of a galvanic couple between the ceramic matrix of TiAlN and the metallic Ag, a TiAlN composite coating doped with four different contents of silver (0.8-25 at.%) was deposited on AISI H11 hot working steel, using the hybrid DCMS/HiPIMS magnetron sputtering technique. The microstructure, topography, elemental chemical, and phase composition of the coatings were determined using SEM/EDS, AFM, XRD, and XPS characterization techniques. The electrochemical behavior was evaluated by electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization. The TiAlN matrix and TiAlN(Ag)-coated samples exhibit higher impedance modulus values than steel substrate, indicating better anticorrosion performance. The anodic current density of the Ag-doped coating increases with the Ag content, suggesting enhanced silver release to the surrounding electrolyte. The TiAlN coating doped with 0.8 at.% silver exhibited the highest corrosion resistance at long immersion times. Finally, it must be noted that all the coatings exhibited corrosion protection to the AISI H11 steel substrate. © 2021, ASM International.
    view abstractdoi: 10.1007/s11665-021-06467-9
  • 2022 • 174 Characterization of the Microstructure and Thermomechanical Properties of Invar 36 Coatings Deposited by HVOF and Cold Gas Processes
    Tillmann, W. and Khalil, O. and Baumann, I.
    Journal of Thermal Spray Technology 31 2476-2488 (2022)
    The effect of impact velocity and temperature of invar particles deposited by high-velocity oxygen fuel (HVOF) and cold spray processes on the microstructure and oxidation content of invar coatings is not fully understood. Additionally, the effect of coating thickness on the coefficient of thermal expansion (CTE) of the coated material and the influence of cold working on the coating hardness are also insufficiently investigated. In the present study, invar coatings were deposited at temperatures close to and below the melting point of invar particles to maintain low CTE. It was found that particle impact temperature and velocity strongly affect pore formation and cohesiveness but slightly affect the hardness of invar coatings. Higher particle impact velocities with impact temperatures close to the invar’s melting point enhance highly the cohesiveness of HVOF-invar coatings. Furthermore, invar coatings stabilize the CTE of the coated material up to a temperature of 227 °C. An increment in the coating’s thickness of 150 µm leads to reducing the CTE of the coated material (Al) in the in-plane direction by 7.65%. Applying cold working using 200 kN compression increases the hardness of the treated coatings by 6% while machine hammer peening (MHP) has a slight effect. © 2022, The Author(s).
    view abstractdoi: 10.1007/s11666-022-01458-1
  • 2022 • 173 Tribo-functional PVD thin films deposited onto additively manufactured Ti6Al7Nb for biomedical applications
    Tillmann, W. and Lopes Dias, N.F. and Kokalj, D. and Stangier, D. and Hein, M. and Hoyer, K.-P. and Schaper, M. and Gödecke, D. and Oltmanns, H. and Meißner, J.
    Materials Letters 321 (2022)
    For biomedical applications, the additive manufacturing of titanium-based alloys in combination with a subsequent physical vapor deposition (PVD) of tribo-functional thin films enables producing complex-shaped implants and devices with improved tribological behavior. Titanium nitride (TiN), titanium carbonitride (TiCN), amorphous carbon (a-C), and Ag-containing amorphous carbon (a–C:Ag) thin films were coated on laser powder bed fused (L-PBF) Ti6Al7Nb substrates by magnetron sputtering. TiN exhibits a high adhesion on Ti6Al7Nb, whereas TiCN, a–C, and a–C:Ag have a lower adhesion strength. In lubricated tribometer tests against Al2O3, the PVD thin films are highly effective in improving the tribological properties of additively manufactured Ti6Al7Nb. TiCN, a–C, and a–C:Ag show lower friction than uncoated Ti6Al7Nb and TiN, with a–C and a–C:Ag having the lowest coefficients of friction. Compared to uncoated Ti6Al7Nb, the PVD films also considerably reduce both the wear and counterpart wear. © 2022 Elsevier B.V.
    view abstractdoi: 10.1016/j.matlet.2022.132384
  • 2022 • 172 Heat treatment of binder jet printed 17–4 PH stainless steel for subsequent deposition of tribo-functional diamond-like carbon coatings
    Tillmann, W. and Lopes Dias, N.F. and Stangier, D. and Schaak, C. and Höges, S.
    Materials and Design 213 (2022)
    Diamond-like carbon (DLC) coatings deposited on additively manufactured steel greatly improve the tribological properties. However, a high substrate hardness is crucial to sustaining high mechanical loads in the tribological contact. Herein, the heat treatment of binder jet printed 17–4 PH enhances the hardness from 24 to 39 HRC. Binder jet printed 17–4 PH substrates are coated by DLC of the types hydrogen-free amorphous carbon (a-C) of ∼23 GPa and hydrogenated amorphous carbon (a-C:H) of ∼20 GPa. The influence of the heat treatment on the tribo-mechanical properties of the DLC coatings is investigated. 17–4 PH demonstrates high friction and wear against steel counterparts, but the wear rate is reduced from 693 ± 43 × 10–6 mm3/Nm to 492 ± 41 × 10-6 mm3/Nm by heat treating the steel. Both a–C and a–C:H are effective in reducing the friction and wear with wear rates below 0.3 × 10–6 mm3/Nm. The a–C and a–C:H coatings demonstrate lower plastic wear on heat treated 17–4 PH due to the higher substrate hardness. Consequently, the heat treatment is an essential process step to ensure maximum tribological functionality of the DLC coating on additively manufactured 17–4 PH steel. © 2021 The Authors
    view abstractdoi: 10.1016/j.matdes.2021.110304
  • 2022 • 171 Deciphering the Structural and Chemical Transformations of Oxide Catalysts during Oxygen Evolution Reaction Using Quick X-ray Absorption Spectroscopy and Machine Learning
    Timoshenko, J. and Haase, F.T. and Saddeler, S. and Rüscher, M. and Jeon, H.S. and Herzog, A. and Hejral, U. and Bergmann, A. and Schulz, S. and Roldan Cuenya, B.
    Journal of the American Chemical Society (2022)
    doi: 10.1021/jacs.2c11824
  • 2022 • 170 CARS Imaging Advances Early Diagnosis of Cardiac Manifestation of Fabry Disease
    Tolstik, E. and Ali, N. and Guo, S. and Ebersbach, P. and Möllmann, D. and Arias-Loza, P. and Dierks, J. and Schuler, I. and Freier, E. and Debus, J. and Baba, H.A. and Nordbeck, P. and Bocklitz, T. and Lorenz, K.
    International Journal of Molecular Sciences 23 (2022)
    doi: 10.3390/ijms23105345
  • 2022 • 169 50-W average power Ho:YAG SESAM-modelocked thin-disk oscillator at 2.1 µm
    Tomilov, S. and Wang, Y. and Hoffmann, M. and Heidrich, J. and Golling, M. and Keller, U. and Saraceno, C.J.
    Optics express 30 27662-27673 (2022)
    doi: 10.1364/OE.460298
  • 2022 • 168 Non-gradient full waveform inversion approaches for exploration during mechanized tunneling applied to surrogate laboratory measurements
    Trapp, M. and Nestorović, T.
    Tunnelling and Underground Space Technology 120 (2022)
    Drilling into unknown soil during mechanized tunneling may cause damage of the tunnel boring machine or delays in the construction process. A full waveform inversion can prevent these issues supplying a detailed image of the subsoil, but claims several challenges like the need for an adequate method or the need for an appropriate utilization of seismic sources and receivers. In this research, a small-scale surrogate model is constructed in order to create representative tunneling field data in a laser laboratory. With the experimental model, ultrasonic data is generated. After constructing an adequate forward model, two non-gradient full waveform inversion methods based on parameter identification are applied to the measurement data in order to determine the inner structure of the model out of seismic waveforms. Furthermore, the positioning of seismic sources and receivers is investigated. The algorithms are found to perform well on the acquired measurement data, with different precisions dependent on the utilized method and on the source-receiver configuration. The comparability of the ultrasonic data to tunneling field data is analyzed. © 2021 Elsevier Ltd
    view abstractdoi: 10.1016/j.tust.2021.104252
  • 2022 • 167 Photon Echo Polarimetry of Excitons and Biexcitons in a CH3NH3PbI3Perovskite Single Crystal
    Trifonov, A.V. and Grisard, S. and Kosarev, A.N. and Akimov, I.A. and Yakovlev, D.R. and Höcker, J. and Dyakonov, V. and Bayer, M.
    ACS Photonics 9 621-629 (2022)
    Lead halide perovskites show remarkable performance when used in photovoltaic and optoelectronic devices. However, the peculiarities of light-matter interactions in these materials in general are far from being fully explored experimentally and theoretically. Herein, we specifically address the energy level order of optical transitions and demonstrate photon echoes in a methylammonium lead triiodide single crystal, thereby determining the optical coherence times (T2) for excitons and biexcitons at cryogenic temperature to be 0.79 and 0.67 ps, respectively. Most importantly, we have developed an experimental photon-echo polarimetry method that not only identifies the contributions from exciton and biexciton complexes but also allows accurate determination of the biexciton binding energy of 2.4 meV, even though the period of quantum beats between excitons and biexcitons is much longer than the coherence times of the resonances. Our experimental and theoretical analysis methods contribute to the understanding of the complex mechanism of quasiparticle interactions at moderate pump density and show that even in high-quality perovskite crystals and at very low temperatures, inhomogeneous broadening of excitonic transitions due to local crystal potential fluctuations is a source of optical dephasing. ©
    view abstractdoi: 10.1021/acsphotonics.1c01603
  • 2022 • 166 Electronic cigarette liquids impair metabolic cooperation and alter proteomic profiles in V79 cells
    Trifunovic, S. and Smiljanić, K. and Sickmann, A. and Solari, F.A. and Kolarevic, S. and Divac Rankov, A. and Ljujic, M.
    Respiratory Research 23 (2022)
    Background: Although still considered a safer alternative to classical cigarettes, growing body of work points to harmful effects of electronic cigarettes (e-cigarettes) affecting a range of cellular processes. The biological effect of e-cigarettes needs to be investigated in more detail considering their widespread use. Methods: In this study, we treated V79 lung fibroblasts with sub-cytotoxic concentration of e-cigarette liquids, with and without nicotine. Mutagenicity was evaluated by HPRT assay, genotoxicity by comet assay and the effect on cellular communication by metabolic cooperation assay. Additionally, comprehensive proteome analysis was performed via high resolution, parallel accumulation serial fragmentation-PASEF mass spectrometry. Results: E-cigarette liquid concentration used in this study showed no mutagenic or genotoxic effect, however it negatively impacted metabolic cooperation between V79 cells. Both e-cigarette liquids induced significant depletion in total number of proteins and impairment of mitochondrial function in treated cells. The focal adhesion proteins were upregulated, which is in accordance with the results of metabolic cooperation assay. Increased presence of posttranslational modifications (PTMs), including carbonylation and direct oxidative modifications, was observed. Data are available via ProteomeXchange with identifier PXD032071. Conclusions: Our study revealed impairment of metabolic cooperation as well as significant proteome and PTMs alterations in V79 cells treated with e-cigarette liquid warranting future studies on e-cigarettes health impact. © 2022, The Author(s).
    view abstractdoi: 10.1186/s12931-022-02102-w
  • 2022 • 165 Deformation and phase transformation in polycrystalline cementite (Fe3C) during single- and multi-pass sliding wear
    Tsybenko, H. and Tian, C. and Rau, J. and Breitbach, B. and Schreiber, P. and Greiner, C. and Dehm, G. and Brinckmann, S.
    Acta Materialia 227 (2022)
    Cementite (Fe3C) plays a major role in the tribological performance of rail and bearing steels. Nonetheless, the current understanding of its deformation behavior during wear is limited because it is conventionally embedded in a matrix. Here, we investigate the deformation and chemical evolution of bulk polycrystalline cementite during single-pass sliding at a contact pressure of 31 GPa and reciprocating multi-pass sliding at 3.3 GPa. The deformation behavior of cementite was studied by electron backscatter diffraction for slip trace analysis and transmission electron microscopy. Our results demonstrate activation of several deformation mechanisms below the contact surface: dislocation slip, shear band formation, fragmentation, grain boundary sliding, and grain rotation. During sliding wear, cementite ductility is enhanced due to the confined volume, shear/compression domination, and potentially frictional heating. The microstructural alterations during multi-pass wear increase the subsurface nanoindentation hardness by up to 2.7 GPa. In addition, we report Hägg carbide (Fe5C2) formation in the uppermost deformed regions after both sliding experiments. Based on the results of electron and X-ray diffraction, as well as atom probe tomography, we propose potential sources of excess carbon and mechanisms that promote the phase transformation. © 2022 The Author(s)
    view abstractdoi: 10.1016/j.actamat.2022.117694
  • 2022 • 164 Accuracy Limits of Chipless RFID Based Indoor Localization System at THz band
    Tubail, D. and El-Absi, M. and Ikki, S. and Kaiser, T.
    2022 5th International Workshop on Mobile Terahertz Systems, IWMTS 2022 (2022)
    doi: 10.1109/IWMTS54901.2022.9832451
  • 2022 • 163 Bismuth-based halide perovskite and perovskite-inspired light absorbing materials for photovoltaics
    Ünlü, F. and Deo, M. and Mathur, S. and Kirchartz, T. and Kulkarni, A.
    Journal of Physics D: Applied Physics 55 (2022)
    The efficiency of organic-inorganic hybrid lead halide perovskite solar cells (PSCs) has increased over 25% within a frame of ten years, which is phenomenal and indicative of the promising potential of perovskite materials in impacting the next generation solar cells. Despite high technology readiness of PSCs, the presence of lead has raised concerns about the adverse effect of lead on human health and the environment that may slow down or inhibit the commercialization of PSCs. Thus, there is a dire need to identify materials with lower toxicity profile and comparable optoelectronic properties in regard to lead-halide perovskites. In comparison to tin-, germanium-, and copper-based PSCs, which suffer from stability issues under ambient operation, bismuth-based perovskite and perovskite-inspired materials have gained attention because of their enhanced stability in ambient atmospheric conditions. In this topical review, we initially discuss the background of lead and various lead-free perovskite materials and further discuss the fundamental aspects of various bismuth-based perovskite and perovskite-inspired materials having a chemical formula of A3Bi2X9, A2B'BiX6, B' aBibXa+3b (A = Cs+, MA+ and bulky organic ligands; B' = Ag+, Cu+; X = I-, Cl-, Br-) and bismuth triiodide (BiI3) semiconducting material particularly focusing on their structure, optoelectronic properties and the influence of compositional variation on the photovoltaic device performance and stability. © 2021 IOP Publishing Ltd Printed in the UK.
    view abstractdoi: 10.1088/1361-6463/ac3033
  • 2022 • 162 Design and execution of membrane structures according to prCEN/TS 19102 [Bemessung und Ausführung von Membrantragwerken nach prCEN/TS 19102]
    Uhlemann, J. and Stimpfle, B. and Stranghöner, N.
    Stahlbau 91 504-512 (2022)
    Design and execution of membrane structures according to prCEN/TS 19102. This paper reflects the progressive development of the first European design standard for membrane structures. It will be published in future as CEN/TS 19102 “Design of tensioned membrane structures”. In addition to design rules, it will also contain interim execution rules based on the design concept. The current status of the planned regulations in these two areas is presented in this article. © 2022, Ernst und Sohn. All rights reserved.
    view abstractdoi: 10.1002/stab.202200036
  • 2022 • 161 European Harmonized Design for Membrane Structures
    Uhlemann, J. and Stranghöner, N.
    IABSE Symposium Prague, 2022: Challenges for Existing and Oncoming Structures - Report 956-962 (2022)
    Numerous activities of the last years to harmonize and standardize design procedures for membrane structures made from structural textiles or foils lead to a new European standard expected to be published in 2022: CEN/TS 19102 “Design of tensioned membrane structures”. This document is a milestone on the path to a Eurocode for membrane structures. First time it provides unified design rules harmonized among many experts in the field across Europe. It covers coated and uncoated fabrics as well as foils, mechanically as well as pneumatically prestressed structures. Ultimate and serviceability limit state approaches are based on the concepts of EN 1990. The new standard gives the frame for materials and their requirements, static verification of materials and connections, and it defines required experimental tests. It is also planned to provide execution rules together with the design rules in order to ensure reliable and safe membrane structures. This contribution gives an overview of the new standard and shows the approaches by means of examples. © 2022 IABSE Symposium Prague, 2022: Challenges for Existing and Oncoming Structures - Report. All rights reserved.
    view abstract
  • 2022 • 160 Simulation of Arterial Walls: Growth, Fiber Reorientation, and Active Response
    Uhlmann, K. and Zahn, A. and Balzani, D.
    Studies in Mechanobiology, Tissue Engineering and Biomaterials 24 181-209 (2022)
    doi: 10.1007/978-3-030-92339-6_8
  • 2022 • 159 Acoustoelastic Modes in Rotor-Cavity Systems: An Overview on Frequency Shift Effects Supported with Measurements
    Unglaube, T. and Brillert, D.
    International Journal of Turbomachinery, Propulsion and Power 7 (2022)
    doi: 10.3390/ijtpp7020015
  • 2022 • 158 Opportunities for variable rotor lead in screw compressors depending on dimensionless numbers
    Utri, M. and Brümmer, A.
    Proceedings of the Institution of Mechanical Engineers, Part E: Journal of Process Mechanical Engineering 236 4-13 (2022)
    doi: 10.1177/0954408918802716
  • 2022 • 157 The origin of jerky dislocation motion in high-entropy alloys
    Utt, D. and Lee, S. and Xing, Y. and Jeong, H. and Stukowski, A. and Oh, S.H. and Dehm, G. and Albe, K.
    Nature Communications 13 (2022)
    doi: 10.1038/s41467-022-32134-1
  • 2022 • 156 Synthesis and tribological behavior of bio-based lubrication greases with bio-based polyester thickener systems
    Vafaei, S. and Jopen, M. and Jacobs, G. and König, F. and Weberskirch, R.
    Journal of Cleaner Production 364 (2022)
    Commercially available lubricating greases on the market with accepted performance are mostly produced based on petrochemical materials. More recently, there has been an increasing interest to develop sustainable and environment friendly lubricating greases. In this work we have synthesized bio-based and potentially biodegradable lubricating greases with polyester-based thickener systems and castor oil as the base oil. The greases were characterized by their film thickness and friction coefficients on ball-on-disc tribometer, as well as in oscillatory measurements on a rheometer. Furthermore, tribological results are compared with a petrochemical urea-grease as reference and previously-published bio-based grease with polyurea thickener system. The produced greases with polyester thickener systems have shown promising tribological performance compared to the available-on-market petrochemical reference grease regarding the film thickness formation and friction coefficients. © 2022 Elsevier Ltd
    view abstractdoi: 10.1016/j.jclepro.2022.132659
  • 2022 • 155 Engineering mesoporous silica nanoparticles for drug delivery: where are we after two decades?
    Vallet-Regí, M. and Schüth, F. and Lozano, D. and Colilla, M. and Manzano, M.
    Chemical Society Reviews 51 5365-5451 (2022)
    The present review details a chronological description of the events that took place during the development of mesoporous materials, their different synthetic routes and their use as drug delivery systems. The outstanding textural properties of these materials quickly inspired their translation to the nanoscale dimension leading to mesoporous silica nanoparticles (MSNs). The different aspects of introducing pharmaceutical agents into the pores of these nanocarriers, together with their possible biodistribution and clearance routes, would be described here. The development of smart nanocarriers that are able to release a high local concentration of the therapeutic cargo on-demand after the application of certain stimuli would be reviewed here, together with their ability to deliver the therapeutic cargo to precise locations in the body. The huge progress in the design and development of MSNs for biomedical applications, including the potential treatment of different diseases, during the last 20 years will be collated here, together with the required work that still needs to be done to achieve the clinical translation of these materials. This review was conceived to stand out from past reports since it aims to tell the story of the development of mesoporous materials and their use as drug delivery systems by some of the story makers, who could be considered to be among the pioneers in this area. © 2022 The Royal Society of Chemistry
    view abstractdoi: 10.1039/d1cs00659b
  • 2022 • 154 Pivotal tests for relevant differences in the second order dynamics of functional time series
    VAN DELFT, A. and Dette, H.
    Bernoulli 28 2260-2293 (2022)
    doi: 10.3150/21-BEJ1418
  • 2022 • 153 A Perspective on Thermally Sprayed Thermal Barrier Coatings: Current Status and Trends
    Vaßen, R. and Bakan, E. and Mack, D.E. and Guillon, O.
    Journal of Thermal Spray Technology 31 685-698 (2022)
    For more than 6 decades, thermal barrier coatings have been used to protect structural parts in both stationary and aviation gas turbines. These coatings allow the use of significant higher operation temperatures and hence increased efficiencies. In the 1970s, yttria-stabilized zirconia (YSZ) was identified as outstanding material for this application. As major deposition technologies both electron beam physical vapor deposition (EB-PVD) and atmospheric plasma spraying (APS) have been established. Although the topic is already rather old, there are still frequent activities ongoing to further improve the technology, both with respect to materials and microstructural issues also regarding the use of advanced coating technologies, especially in the field of thermal spray. The paper tries to summarize major developments in both fields, the materials and the processing focusing on thermal spray methods. The impact of both materials and processing are summarized by the results of burner rig tests for various systems. Furthermore, a short outlook on possible future directions of developments will be given. © 2022, The Author(s).
    view abstractdoi: 10.1007/s11666-022-01330-2
  • 2022 • 152 Metal-insulator transition and robust thermoelectricity via strain-tuned interplay between structural and electronic properties in (SrVO3)1/(SrTiO3)1(001) superlattices
    Verma, M. and Pentcheva, R.
    Physical Review Research 4 (2022)
    Exploring the origin of the metal-to-insulator transition (MIT) in transition metal oxide heterostructures is of high interest in current condensed matter physics research. Here based on density functional theory calculations with the meta-GGA exchange correlation functional SCAN, we find distinct mechanisms of MIT in (SrVO3)1/(SrTiO3)1(001) superlattices (SLs). The SCAN functional is sufficient to determine the ground state structure and possible symmetry breaking at a given lateral lattice constant and best describes the electronic and magnetic properties of the weakly correlated (SrRuO3)1/(SrTiO3)1(001) SL and its constituents by minimizing the self-interaction error. However, an additional Hubbard U term is necessary for the strongly correlated (SrVO3)1/(SrTiO3)1(001)SLs. We show that SCAN + U always favors the monoclinic (P21/c) symmetry in (SrXO3)1/(SrTiO3)1(001)SLs, X=V and Ru, irrespective of the in-plane lattice constant and X. For the orthorhombic (SrVO3)1/(SrTiO3)1(001)SL(Cmmm) at aSTO (tensile strain +1.7%), we report strong correlation and confinement driven Mott-Hubbard type MIT via long-range stripe antiferromagnetic ordering, whereas, under compressive strain (-3.6%) at aYAO, the interplay of confinement, correlation, and finite octahedral tilts and rotations lead to monoclinic (P21/c) symmetry, which drives an orbital reconstruction and a concomitant MIT with ferromagnetic spin alignment. Lastly, using Boltzmann transport theory within the constant relaxation time approximation, for (SrVO3)1/(SrTiO3)1(001)SL at aSTO, we obtain large n-type Seebeck coefficients S of -566 (in-plane) and -454 μV/K (cross-plane), respectively, along with an in-plane (cross-plane) power factor of 31.4 (8.5) μWK-2cm-1 (assuming τ=4 fs) at 300 K. These values directly categorize (SrVO3)1/(SrTiO3)1(001)SL as a promising oxide thermoelectric material. © 2022 authors. Published by the American Physical Society.
    view abstractdoi: 10.1103/PhysRevResearch.4.033013
  • 2022 • 151 Effects of Dispersion and Charge-Transfer Interactions on Structures of Heavy Chalcogenide Compounds: A Quantum Chemical Case Study for (Et2Bi)2Te
    van der Vight, F. and Schulz, S. and Jansen, G.
    ChemPlusChem (2022)
    The reasons for the unusually small Bi−Te−Bi bond angle of 86.6° observed in the crystal strucure of (Et2Bi)2Te are investigated by quantum chemical calculations. With the help of coupled cluster theory at the CCSD(T) level it is demonstrated that the structure of an isolated monomer should have a bond angle larger than 90°, despite a Bi−Bi distance in good agreement with the value of 4.09 Å found in the crystal structure. The discrepancy is resolved by a lengthening of the Bi−Te bond in the crystal, which is shown to be caused by partial electron transfer from neighbouring molecules to the Bi−Te σ* orbital. Through symmetry-adapted perturbation theory at the DFT-SAPT level it is shown that London dispersion interactions are highly important for the packing of molecules in the solid state and, in turn, for the small Bi−Te−Bi bond angle. © 2022 The Authors. ChemPlusChem published by Wiley-VCH GmbH.
    view abstractdoi: 10.1002/cplu.202100487
  • 2022 • 150 Increased adhesion of thermal sprayed coatings – Innovative process combination enables substitution of conventional blasting processes [Innovative Verfahrenskombination ermöglicht Substitution konventioneller Strahlprozesse Erhöhte Haftfestigkeit thermischer Spritzschichten]
    Vogel, F. and Diaz, M.R. and Biermann, D. and Möhwald, K.
    WT Werkstattstechnik 112 28-33 (2022)
    To enable thermal sprayed coatings with increased adhesion, the Institute of Machining Technology (ISF) of TU Dortmund University together with the Institute of Materials Science (IW) of Leibniz Universität Hannover developed an innovative process combination. This serves as a basis for investigating whether the coating properties can be further optimized by an additional process step to allow for the production of wear-resistant coatings in the future without substrate activation by blasting. © 2022, VDI Fachmedien GmBH & Co. KG. All rights reserved.
    view abstractdoi: 10.37544/1436-4980-2021-1-2-32
  • 2022 • 149 Charging of Dielectric Surfaces in Contact with Aqueous Electrolytesthe Influence of CO2
    Vogel, P. and Möller, N. and Qaisrani, M.N. and Bista, P. and Weber, S.A.L. and Butt, H.-J. and Liebchen, B. and Sulpizi, M. and Palberg, T.
    Journal of the American Chemical Society 144 21080-21087 (2022)
    The charge state of dielectric surfaces in aqueous environments is of fundamental and technological importance. Here, we study the influence of dissolved molecular CO2on the charging of three chemically different surfaces (SiO2, Polystyrene, Perfluorooctadecyltrichlorosilane). We determine their charge state from electrokinetic experiments. We compare an ideal, CO2-free reference system to a system equilibrated against ambient CO2conditions. In the reference system, the salt-dependent decrease of the magnitudes of ζ-potentials follows the expectations for a constant charge scenario. In the presence of CO2, the starting potential is lower by some 50%. The following salt-dependent decrease is weakened for SiO2and inverted for the organic surfaces. We show that screening and pH-driven charge regulation alone cannot explain the observed effects. As an additional cause, we tentatively suggest dielectric regulation of surface charges due to a diffusively adsorbed thin layer of molecular CO2. The formation of such a dynamic layer, even at the hydrophilic and partially ionized silica surfaces, is supported by a minimal theoretical model and results from molecular simulations. © 2022 American Chemical Society. All rights reserved.
    view abstractdoi: 10.1021/jacs.2c06793
  • 2022 • 148 Limit theorems for Bessel and Dunkl processes of large dimensions and free convolutions
    Voit, M. and Woerner, J.H.C.
    Stochastic Processes and their Applications 143 207-253 (2022)
    We study Bessel and Dunkl processes (Xt,k)t≥0 on RN with possibly multivariate coupling constants k≥0. These processes describe interacting particle systems of Calogero–Moser–Sutherland type with N particles. For the root systems AN−1 and BN these Bessel processes are related with β-Hermite and β-Laguerre ensembles. Moreover, for the frozen case k=∞, these processes degenerate to deterministic or pure jump processes. We use the generators for Bessel and Dunkl processes of types A and B and derive analogues of Wigner's semicircle and Marchenko–Pastur limit laws for N→∞ for the empirical distributions of the particles with arbitrary initial empirical distributions by using free convolutions. In particular, for Dunkl processes of type B new non-symmetric semicircle-type limit distributions on R appear. Our results imply that the form of the limiting measures is already completely determined by the frozen processes. Moreover, in the frozen cases, our approach leads to a new simple proof of the semicircle and Marchenko–Pastur limit laws for the empirical measures of the zeros of Hermite and Laguerre polynomials respectively. © 2021 Elsevier B.V.
    view abstractdoi: 10.1016/j.spa.2021.10.005
  • 2022 • 147 The differential equations associated with Calogero-Moser-Sutherland particle models in the freezing regime
    Voit, M. and Woerner, J.H.C.
    Hokkaido Mathematical Journal 51 153-174 (2022)
    Multivariate Bessel processes describe Calogero-Moser-Sutherland particle models. They depend on a root system and a multiplicity k. Recently, several stochastic limit theorems for k → ∞ were derived where the limits depend on the solutions of associated ODEs in these freezing regimes. In this paper we study these ODEs which are singular on the boundaries of their domains. We prove that for arbitrary initial conditions on the boundary, the ODEs have unique solutions in their domains for t > 0. © 2022, Hokkaido Mathematical Journal. All Rights Reserved.
    view abstractdoi: 10.14492/HOKMJ/2020-307
  • 2022 • 146 Axial pulsator increases process reliability in drilling with step drilling tools: Combining Laser drilling process for pilot holes and single-lip deep hole drilling [Laserpilotieren und Einlippentiefbohren kombinieren]
    Volke, P. and Michel, S. and Biermann, D.
    VDI-Z Integrierte Produktion 164 58-61 (2022)
  • 2022 • 145 Friction characterisation during machining of 1.4404 [Reibungscharakterisierung bei der Zerspanung von 1.4404]
    Volke, P. and Saelzer, J. and Biermann, D.
    WT Werkstattstechnik 112 436-441 (2022)
    doi: 10.37544/1436-4980-2022-6-86
  • 2022 • 144 SUSTAINABLE PRODUCTION OF ROTATIONALLY SYMMETRICAL COMPONENTS: APPROACHES TO RESOURCE SAVING ON TOOL AND WORKPIECE
    Volke, P. and Brock, G. and Berger, S. and Saelzer, J. and Nickel, J. and Biermann, D.
    ASME International Mechanical Engineering Congress and Exposition, Proceedings (IMECE) 2-B (2022)
    doi: 10.1115/IMECE2022-95378
  • 2022 • 143 Microscopic Origin of the Effective Spin-Spin Interaction in a Semiconductor Quantum Dot Ensemble
    Vonhoff, F. and Fischer, A. and Deltenre, K. and Anders, F.B.
    Physical Review Letters 129 (2022)
    doi: 10.1103/PhysRevLett.129.167701
  • 2022 • 142 Additive Manufacturing of Columnar Thermal Barrier Coatings by Laser Cladding of Ceramic Feedstock
    Vorkötter, C. and Mack, D.E. and Vaßen, R. and Guillon, O.
    Advanced Materials Technologies 7 (2022)
    This study presents a new laser-cladding-based additive manufacturing technique named Clad2Z. Using a robot-mounted confocal powder nozzle with axial infrared laser beam, ceramic columns with a diameter of 450 µm and an adjustable height are developed. Influence of laser parameters and robot movements on shape and microstructure is analyzed. As an example application, the common material yttria-stabilized zirconia (YSZ) is used to deposit columnar-structured thermal barrier coatings (TBCs). The excellent thermal cycling performance of the Clad2Z samples is demonstrated by burner rig tests and comparing lifetime and failure mechanism with conventional TBC systems. © 2022 The Authors. Advanced Materials Technologies published by Wiley-VCH GmbH.
    view abstractdoi: 10.1002/admt.202200098
  • 2022 • 141 Effect of Low-CTE Oxide-Dispersion-Strengthened Bond Coats on Columnar-Structured YSZ Coatings
    Vorkötter, C. and Mack, D.E. and Zhou, D. and Guillon, O. and Vaßen, R.
    Coatings 12 (2022)
    Thermal barrier coatings (TBCs) are commonly used to protect gas turbine components from high temperatures and oxidation. Such coatings consist of ceramic top coats and metallic bond coats. The mismatch in thermal expansion of the top coat, the bond coat and the component material is one main factor leading to the failure of the coating system. Columnar-structured top coats offer an enhanced tolerance to the strain during thermal cycling. On a flat bond coated surface, these TBCs reach higher thermal cycling performance. However, on rough surfaces, as used for thermal spray coatings, the performance of these thermal barrier coatings seems to be restricted or even stays below the performance of atmospheric-plasma-sprayed (APS) thermal barrier coatings. This low performance is linked to out-of-plane stresses at the interface between the top coat and the bond coat. In this study, a thin additional oxide-dispersion-strengthened (ODS) bond coat with high alumina content provides a reduced mismatch of the coefficient of thermal expansion (CTE) between the top coat and the bond coat. Columnar suspension plasma sprayed (SPS), yttria-stabilized zirconia (YSZ) TBCs were combined with low-CTE ODS bond coats. The behavior of these TBCs was characterized with respect to thermal cycling performance and degradation in a burner-rig facility. The comparison showed an up-to-four-fold increase in the performance of the new system. © 2022 by the authors. Licensee MDPI, Basel, Switzerland.
    view abstractdoi: 10.3390/coatings12030396
  • 2022 • 140 A rank-one convex, nonpolyconvex isotropic function on with compact connected sublevel sets
    Voss, J. and Ghiba, I.-D. and Martin, R.J. and Neff, P.
    Proceedings of the Royal Society of Edinburgh Section A: Mathematics (2022)
    According to a 2002 theorem by Cardaliaguet and Tahraoui, an isotropic, compact and connected subset of the group of invertible - - matrices is rank-one convex if and only if it is polyconvex. In a 2005 Journal of Convex Analysis article by Alexander Mielke, it has been conjectured that the equivalence of rank-one convexity and polyconvexity holds for isotropic functions on as well, provided their sublevel sets satisfy the corresponding requirements. We negatively answer this conjecture by giving an explicit example of a function which is not polyconvex, but rank-one convex as well as isotropic with compact and connected sublevel sets. Copyright © The Author(s), 2022. Published by Cambridge University Press on behalf of The Royal Society of Edinburgh.
    view abstractdoi: 10.1017/prm.2021.9
  • 2022 • 139 Numerical Approaches for Investigating Quasiconvexity in the Context of Morrey’s Conjecture
    Voss, J. and Martin, R.J. and Sander, O. and Kumar, S. and Kochmann, D.M. and Neff, P.
    Journal of Nonlinear Science 32 (2022)
    Deciding whether a given function is quasiconvex is generally a difficult task. Here, we discuss a number of numerical approaches that can be used in the search for a counterexample to the quasiconvexity of a given function W. We will demonstrate these methods using the planar isotropic rank-one convex function Wmagic+(F)=λmaxλmin-logλmaxλmin+logdetF=λmaxλmin+2logλmin,where λmax≥ λmin are the singular values of F, as our main example. In a previous contribution, we have shown that quasiconvexity of this function would imply quasiconvexity for all rank-one convex isotropic planar energies W: GL +(2) → R with an additive volumetric-isochoric split of the form W(F)=Wiso(F)+Wvol(detF)=W~iso(FdetF)+Wvol(detF)with a concave volumetric part. This example is therefore of particular interest with regard to Morrey’s open question whether or not rank-one convexity implies quasiconvexity in the planar case. © 2022, The Author(s).
    view abstractdoi: 10.1007/s00332-022-09820-x
  • 2022 • 138 Morrey’s Conjecture for the Planar Volumetric-Isochoric Split: Least Rank-One Convex Energy Functions
    Voss, J. and Martin, R.J. and Ghiba, I.-D. and Neff, P.
    Journal of Nonlinear Science 32 (2022)
    We consider Morrey’s open question whether rank-one convexity already implies quasiconvexity in the planar case. For some specific families of energies, there are precise conditions known under which rank-one convexity even implies polyconvexity. We will extend some of these findings to the more general family of energies W: GL +(n) → R with an additive volumetric-isochoric split, i.e. W(F)=Wiso(F)+Wvol(detF)=W~iso(FdetF)+Wvol(detF),which is the natural finite extension of isotropic linear elasticity. Our approach is based on a condition for rank-one convexity which was recently derived from the classical two-dimensional criterion by Knowles and Sternberg and consists of a family of one-dimensional coupled differential inequalities. We identify a number of “least” rank-one convex energies and, in particular, show that for planar volumetric-isochorically split energies with a concave volumetric part, the question of whether rank-one convexity implies quasiconvexity can be reduced to the open question of whether the rank-one convex energy function Wmagic+(F)=λmaxλmin-logλmaxλmin+logdetF=λmaxλmin+2logλminis quasiconvex. In addition, we demonstrate that under affine boundary conditions, Wmagic+(F) allows for non-trivial inhomogeneous deformations with the same energy level as the homogeneous solution, and show a surprising connection to the work of Burkholder and Iwaniec in the field of complex analysis. © 2022, The Author(s).
    view abstractdoi: 10.1007/s00332-022-09827-4
  • 2022 • 137 Identification of the main mixing process in the synthesis of alloy nanoparticles by laser ablation of compacted micropowder mixtures
    Waag, F. and Fares, W.I.M.A. and Li, Y. and Andronescu, C. and Gökce, B. and Barcikowski, S.
    Journal of Materials Science 57 3041-3056 (2022)
    Alloy nanoparticles offer the possibility to tune functional properties of nanoscale structures. Prominent examples of tuned properties are the local surface plasmon resonance for sensing applications and adsorption energies for applications in catalysis. Laser synthesis of colloidal nanoparticles is well suited for generating alloy nanoparticles of desired compositions. Not only bulk alloys but also compacted mixtures of single-metal micropowders can serve as ablation targets. However, it is still unknown how mixing of the individual metals transfers from the micro- to the nanoscale. This work experimentally contributes to the elucidation of the mixing processes during the laser-based synthesis of alloy nanoparticles. Key parameters, such as the initial state of mixing in the ablation target, the laser pulse duration, the laser spot size, and the ablation time, are varied. Experiments are performed on a cobalt-iron alloy, relevant for application in oxidation catalysis, in ethanol. The extent of mixing in the targets after ablation and in individual nanoparticles are studied by energy-dispersive X-ray spectroscopy and by cyclic voltammetry at relevant conditions for the oxygen evolution reaction, as model reaction. The results point at the benefits of well pre-mixed ablation targets and longer laser pulse durations for the laser-based synthesis of alloy nanoparticles. Graphical abstract: [Figure not available: see fulltext.] © 2021, The Author(s).
    view abstractdoi: 10.1007/s10853-021-06731-2
  • 2022 • 136 Effects of Cr/Ni ratio on physical properties of Cr-Mn-Fe-Co-Ni high-entropy alloys
    Wagner, C. and Ferrari, A. and Schreuer, J. and Couzinié, J.-P. and Ikeda, Y. and Körmann, F. and Eggeler, G. and George, E.P. and Laplanche, G.
    Acta Materialia 227 (2022)
    Physical properties of ten single-phase FCC CrxMn20Fe20Co20Ni40-x high-entropy alloys (HEAs) were investigated for 0 ≤ x ≤ 26 at%. The lattice parameters of these alloys were nearly independent of composition while solidus temperatures increased linearly by ∼30 K as x increased from 0 to 26 at.%. For x ≥ 10 at.%, the alloys are not ferromagnetic between 100 and 673 K and the temperature dependencies of their coefficients of thermal expansion and elastic moduli are independent of composition. Magnetic transitions and associated magnetostriction were detected below ∼200 K and ∼440 K in Cr5Mn20Fe20Co20Ni35 and Mn20Fe20Co20Ni40, respectively. These composition and temperature dependencies could be qualitatively reproduced by ab initio simulations that took into account a ferrimagnetic ↔ paramagnetic transition. Transmission electron microscopy revealed that plastic deformation occurs initially by the glide of perfect dislocations dissociated into Shockley partials on {111} planes. From their separations, the stacking fault energy (SFE) was determined, which decreases linearly from 69 to 23 mJ·m−2 as x increases from 14 to 26 at.%. Ab initio simulations were performed to calculate stable and unstable SFEs and estimate the partial separation distances using the Peierls-Nabarro model. While the compositional trends were reasonably well reproduced, the calculated intrinsic SFEs were systematically lower than the experimental ones. Our ab initio simulations show that, individually, atomic relaxations, finite temperatures, and magnetism strongly increase the intrinsic SFE. If these factors can be simultaneously included in future computations, calculated SFEs will likely better match experimentally determined SFEs. © 2022
    view abstractdoi: 10.1016/j.actamat.2022.117693
  • 2022 • 135 A Compact Measurement Setup for the Validation of MIMO arrays in D-band and W-band
    Wagner, J. and Dahl, C. and Rolfes, I. and Barowski, J.
    2022 German Microwave Conference, GeMiC 2022 45-48 (2022)
    This paper presents a measurement setup for scanning the virtual array of a Multiple Input-Multiple Output (MIMO) system which can be used to validate MIMO array concepts. Two FMCW (Frequency-Modulated Continuous Wave) radar sensors are used for this purpose, mounted on a 2D linear rail. Resulting MIMO images can be matched to corresponding radar cross section (RCS) values using the described calibration method. In order to increase the image quality, averaging is used for a larger signal-to-noise ratio (SNR). Measurements show that the achieved angular resolution matches with theoretically possible values. © 2022 IMA.
    view abstract
  • 2022 • 134 Comparative Study of Automotive MIMO Radar Measurements in W-Band and D-Band
    Wagner, J. and Dahl, C. and Rolfes, I. and Barowski, J.
    2022 19th European Radar Conference, EuRAD 2022 257-260 (2022)
    doi: 10.23919/EuRAD54643.2022.9924831
  • 2022 • 133 Micro structuring tool steel components using Precise Electrochemical Machining (PECM)
    Wali, A. and Platt, T. and Meijer, A. and Biermann, D.
    Production Engineering (2022)
    doi: 10.1007/s11740-022-01167-2
  • 2022 • 132 A Novel Test Rig Using Air for Investigation of Vibration and Interaction of Two Steam Turbine Control Valves
    Wallat, S. and Preibisch, S. and Strauch, M. and Brillert, D.
    Journal of Engineering for Gas Turbines and Power 144 (2022)
    doi: 10.1115/1.4052160
  • 2022 • 131 VORTEX-GENERATORS REDUCE THE DYNAMIC AXIAL FORCES IN THE MODEL OF A STEAM TURBINE CONTROL VALVE
    Wallat, S. and Musch, C. and Brillert, D.
    Proceedings of the ASME Turbo Expo 2 (2022)
    doi: 10.1115/GT2022-80688
  • 2022 • 130 Fluid-structure interaction simulation of tissue degradation and its effects on intra-aneurysm hemodynamics
    Wang, H. and Uhlmann, K. and Vedula, V. and Balzani, D. and Varnik, F.
    Biomechanics and Modeling in Mechanobiology (2022)
    Tissue degradation plays a crucial role in vascular diseases such as atherosclerosis and aneurysms. Computational modeling of vascular hemodynamics incorporating both arterial wall mechanics and tissue degradation has been a challenging task. In this study, we propose a novel finite element method-based approach to model the microscopic degradation of arterial walls and its interaction with blood flow. The model is applied to study the combined effects of pulsatile flow and tissue degradation on the deformation and intra-aneurysm hemodynamics. Our computational analysis reveals that tissue degradation leads to a weakening of the aneurysmal wall, which manifests itself in a larger deformation and a smaller von Mises stress. Moreover, simulation results for different heart rates, blood pressures and aneurysm geometries indicate consistently that, upon tissue degradation, wall shear stress increases near the flow-impingement region and decreases away from it. These findings are discussed in the context of recent reports regarding the role of both high and low wall shear stress for the progression and rupture of aneurysms. © 2022, The Author(s).
    view abstractdoi: 10.1007/s10237-022-01556-7
  • 2022 • 129 Effect of laser shock peening without protective coating on the surface mechanical properties of NiTi alloy
    Wang, H. and Keller, S. and Chang, Y. and Kashaev, N. and Yan, K. and Gurevich, E.L. and Ostendorf, A.
    Journal of Alloys and Compounds 896 (2022)
    We study the effect of laser shock peening (LSP) without protective coating on the surface mechanical property of NiTi alloy. The Vickers microhardness and wear resistance are measured to determine the mechanical property of NiTi samples treated with different LSP parameters (3 J with 10 ns and 5 J with 20 ns). From the electron backscatter diffraction (EBSD) analysis, it can be found that the laser shock peening does not induce obvious grain refinement in the surface region of NiTi alloy. Both compressive and tensile residual stress in the top layer are determined using the hole drilling method. The results show that the LSP treatment without a protective coating increases the roughness and enhances the surface mechanical properties of NiTi alloy. © 2021 Elsevier B.V.
    view abstractdoi: 10.1016/j.jallcom.2021.163011
  • 2022 • 128 The dual role of martensitic transformation in fatigue crack growth
    Wang, X. and Liu, C. and Sun, B. and Ponge, D. and Jiang, C. and Raabe, D.
    Proceedings of the National Academy of Sciences of the United States of America 119 (2022)
    Deformation-induced martensitic transformation (DIMT) has been used for designing high-performance alloys to prevent structural failure under static loads. Its effectiveness against fatigue, however, is unclear. This limits the application of DIMT for parts that are exposed to variable loads, although such scenarios are the rule and not the exception for structural failure. Here we reveal the dual role of DIMT in fatigue crack growth through in situ observations. Two antagonistic fatigue mechanisms mediated by DIMT are identified, namely, transformation-mediated crack arresting, which prevents crack growth, and transformation-mediated crack coalescence, which promotes crack growth. Both mechanisms are due to the hardness and brittleness of martensite as a transformation product, rather than to the actual transformation process itself. In fatigue crack growth, the prevalence of one mechanism over the other critically depends on the crack size and the mechanical stability of the parent austenite phase. Elucidating the two mechanisms and their interplay allows for the microstructure design and safe use of metastable alloys that experience fatigue loads. The findings also generally reveal how metastable alloy microstructures must be designed for materials to be fatigue-resistant. © 2022 National Academy of Sciences. All rights reserved.
    view abstractdoi: 10.1073/pnas.2110139119
  • 2022 • 127 Tuning Electronic Structures of Covalent Co Porphyrin Polymers for Electrocatalytic CO2Reduction in Aqueous Solutions
    Wang, Y. and Zhang, X.-P. and Lei, H. and Guo, K. and Xu, G. and Xie, L. and Li, X. and Zhang, W. and Apfel, U.-P. and Cao, R.
    CCS Chemistry 41 2959-2967 (2022)
    doi: 10.31635/ccschem.022.202101706
  • 2022 • 126 Powder preparation during ball milling and laser additive manufacturing of aluminum matrix nanocomposites: Powder properties, processability and mechanical property
    Wang, R. and Xi, L. and Ding, K. and Gökce, B. and Barcikowski, S. and Gu, D.
    Advanced Powder Technology 33 (2022)
    doi: 10.1016/j.apt.2022.103687
  • 2022 • 125 Grating-Lobe Suppression for Periodic Leaky-Wave Antennas at the Full Array Level
    Wang, P.-Y. and Lyu, Y.-L. and Meng, F.-Y. and Rennings, A. and Erni, D.
    IEEE Antennas and Wireless Propagation Letters 21 2115-2119 (2022)
    doi: 10.1109/LAWP.2022.3191981
  • 2022 • 124 An Electronically Beam Steering Array Based on Liquid Crystals Operating in W-Band
    Wang, P.-Y. and Rennings, A. and Erni, D.
    2022 5th International Workshop on Mobile Terahertz Systems, IWMTS 2022 (2022)
    doi: 10.1109/IWMTS54901.2022.9832446
  • 2022 • 123 Sidelobe Suppression for Leaky-Wave Antennas Using a Complementary Paired Configuration
    Wang, P. and Lyu, Y. and Meng, F. and Rennings, A. and Erni, D.
    IEEE Antennas and Wireless Propagation Letters 1-5 (2022)
    doi: 10.1109/LAWP.2022.3196399
  • 2022 • 122 Generation of a Single-Cycle Acoustic Pulse: A Scalable Solution for Transport in Single-Electron Circuits
    Wang, J. and Ota, S. and Edlbauer, H. and Jadot, B. and Mortemousque, P.-A. and Richard, A. and Okazaki, Y. and Nakamura, S. and Ludwig, Ar. and Wieck, A.D. and Urdampilleta, M. and Meunier, T. and Kodera, T. and Kaneko, N.-H. and...
    Physical Review X 12 (2022)
    The synthesis of single-cycle pulses of compressed light and microwave signals sparked novel areas of fundamental research. In the field of acoustics, however, such a generation has not been introduced yet. For numerous applications, the large spatial extent of surface acoustic waves (SAW) causes unwanted perturbations and limits the accuracy of physical manipulations. Particularly, this restriction applies to SAW-driven quantum experiments with single flying electrons, where extra modulation renders the exact position of the transported electron ambiguous and leads to undesired spin mixing. Here, we address this challenge by demonstrating single-shot chirp synthesis of a strongly compressed acoustic pulse. Employing this solitary SAW pulse to transport a single electron between distant quantum dots with an efficiency exceeding 99%, we show that chirp synthesis is competitive with regular transduction approaches. Performing a time-resolved investigation of the SAW-driven sending process, we outline the potential of the chirped SAW pulse to synchronize single-electron transport from many quantum-dot sources. By superimposing multiple pulses, we further point out the capability of chirp synthesis to generate arbitrary acoustic waveforms tailorable to a variety of (opto)nanomechanical applications. Our results shift the paradigm of compressed pulses to the field of acoustic phonons and pave the way for a SAW-driven platform of single-electron transport that is precise, synchronized, and scalable. © 2022 authors. Published by the American Physical Society.
    view abstractdoi: 10.1103/PhysRevX.12.031035
  • 2022 • 121 Effect of laser shock peening with square laser spot on hardness and residual stress of Ti6Al4V alloy
    Wang, H. and Kaufman, J. and Brajer, J. and Gurevich, E.L. and Ostendorf, A.
    Proceedings of SPIE - The International Society for Optical Engineering 11994 (2022)
    doi: 10.1117/12.2611090
  • 2022 • 120 Tetraphenylethylene-embedded [15]paracyclophanes: AIEgen and macrocycle merged novel supramolecular hosts used for sensing Ni2+ ions
    Wang, K. and Huang, X. and Mohan, M. and Zhang, K. and Zuo, M. and Shen, Y. and Zhao, Y. and Niemeyer, J. and Hu, X.-Y.
    Chemical Communications 58 6196-6199 (2022)
    Transformation of [15]paracyclophanes ([15]PCP) into fluorophores has been achieved by embedding tetraphenylethene (TPE) units into their skeletons at the meso-positions. The obtained two hosts demonstrated distinct aggregation-induced emission (AIE) properties and their fluorescence could be selectively quenched by Ni2+ ions. © 2022 The Royal Society of Chemistry
    view abstractdoi: 10.1039/d2cc01491b
  • 2022 • 119 High stress twinning in a compositionally complex steel of very high stacking fault energy
    Wang, Z. and Lu, W. and An, F. and Song, M. and Ponge, D. and Raabe, D. and Li, Z.
    Nature Communications 13 (2022)
    Deformation twinning is rarely found in bulk face-centered cubic (FCC) alloys with very high stacking fault energy (SFE) under standard loading conditions. Here, based on results from bulk quasi-static tensile experiments, we report deformation twinning in a micrometer grain-sized compositionally complex steel (CCS) with a very high SFE of ~79 mJ/m2, far above the SFE regime for twinning (&lt;~50 mJ/m2) reported for FCC steels. The dual-nanoprecipitation, enabled by the compositional degrees of freedom, contributes to an ultrahigh true tensile stress up to 1.9 GPa in our CCS. The strengthening effect enhances the flow stress to reach the high critical value for the onset of mechanical twinning. The formation of nanotwins in turn enables further strain hardening and toughening mechanisms that enhance the mechanical performance. The high stress twinning effect introduces a so far untapped strengthening and toughening mechanism, for enabling the design of high SFEs alloys with improved mechanical properties. © 2022, The Author(s).
    view abstractdoi: 10.1038/s41467-022-31315-2
  • 2022 • 118 In Situ Monitoring of Palladium-Catalyzed Chemical Reactions by Nanogap-Enhanced Raman Scattering using Single Pd Cube Dimers
    Wang, D. and Shi, F. and Jose, J. and Hu, Y. and Zhang, C. and Zhu, A. and Grzeschik, R. and Schlücker, S. and Xie, W.
    Journal of the American Chemical Society 144 5003-5009 (2022)
    The central dilemma in label-free in situ surface-enhanced Raman scattering (SERS) for monitoring of heterogeneously catalyzed reactions is the need of plasmonically active nanostructures for signal enhancement. Here, we show that the assembly of catalytically active transition-metal nanoparticles into dimers boosts their intrinsically insufficient plasmonic activity at the monomer level by several orders of magnitude, thereby enabling the in situ SERS monitoring of various important heterogeneously catalyzed reactions at the single-dimer level. Specifically, we demonstrate that Pd nanocubes (NCs), which alone are not sufficiently plasmonically active as monomers, can act as a monometallic yet bifunctional platform with both catalytic and satisfactory plasmonic activity via controlled assembly into single dimers with an ∼1 nm gap. Computer simulations reveal that the highest enhancement factors (EFs) occur at the corners of the gap, which has important implications for the SERS-based detection of catalytic conversions: it is sufficient for molecules to come in contact with the "hot spot corners", and it is not required that they diffuse deeply into the gap. For the widely employed Pd-catalyzed Suzuki-Miyaura cross-coupling reaction, we demonstrate that such Pd NC dimers can be employed for in situ kinetic SERS monitoring, using a whole series of aryl halides as educts. Our generic approach based on the controlled assembly into dimers can easily be extended to other transition-metal nanostructures. © 2022 American Chemical Society.
    view abstractdoi: 10.1021/jacs.1c13240
  • 2022 • 117 Design and Application of a High-Surface-Area Mesoporous δ-MnO2Electrocatalyst for Biomass Oxidative Valorization
    Wang, C. and Bongard, H.-J. and Weidenthaler, C. and Wu, Y. and Schüth, F.
    Chemistry of Materials 34 3123-3132 (2022)
    The design and application of electrocatalysts based on Earth-abundant transition-metal oxides for biomass valorization remain relatively underexplored. Here, we report a nanocasting route to synthesize mesoporous δ-MnO2 with a high surface area (198 m2/g), high pore volume, and narrow pore size distributions to address this issue. By taking structural advantages of mesoporous oxides, this mesoporous δ-MnO2 is employed as a highly efficient, selective, and robust anode for 5-hydroxymethylfurfural (HMF) electrochemical oxidation to 2,5-furandicarboxylic acid (FDCA) with a high yield (98%) and faradic efficiency (98%) under alkaline conditions. The electrocatalyst is also effective for the more difficult HMF electro-oxidation under acidic conditions, forming both FDCA and maleic acid as value-added products in a potential-dependent manner. Experimental results combined with theoretical calculations provide insights into the reaction kinetics and the reaction pathways of electrochemical HMF oxidation over this advanced electrocatalyst. This work thus showcases the rational design of non-noble metal electrodes for multiple applications, such as oxygen evolution, water electrolysis, and biomass upgrading with high energy efficiency. © 2022 The Authors. Published by American Chemical Society and Division of Chemical Education, Inc.
    view abstractdoi: 10.1021/acs.chemmater.1c04223
  • 2022 • 116 Effects of Extracellular Vesicles from Osteogenic Differentiated Human BMSCs on Osteogenic and Adipogenic Differentiation Capacity of Naïve Human BMSCs
    Wang, C. and Stöckl, S. and Li, S. and Herrmann, M. and Lukas, C. and Reinders, Y. and Sickmann, A. and Grässel, S.
    Cells 11 (2022)
    Osteoporosis, or steroid-induced osteonecrosis of the hip, is accompanied by increased bone marrow adipogenesis. Such a disorder of adipogenic/osteogenic differentiation, affecting bone-marrow-derived mesenchymal stem cells (BMSCs), contributes to bone loss during aging. Here, we investigated the effects of extracellular vesicles (EVs) isolated from human (h)BMSCs during different stages of osteogenic differentiation on the osteogenic and adipogenic differentiation capacity of naïve (undifferentiated) hBMSCs. We observed that all EV groups increased viability and proliferation capacity and suppressed the apoptosis of naïve hBMSCs. In particular, EVs derived from hBMSCs at late-stage osteogenic differentiation promoted the osteogenic potential of naïve hBMSCs more effectively than EVs derived from naïve hBMSCs (naïve EVs), as indicated by the increased gene expression of COL1A1 and OPN. In contrast, the adipogenic differentiation capacity of naïve hBMSCs was inhibited by treatment with EVs from osteogenic differentiated hBMSCs. Proteomic analysis revealed that osteogenic EVs and naïve EVs contained distinct protein profiles, with pro-osteogenic and anti-adipogenic proteins encapsulated in osteogenic EVs. We speculate that osteogenic EVs could serve as an intercellular communication system between bone- and bone-marrow adipose tissue, for transporting osteogenic factors and thus favoring pro-osteogenic processes. Our data may support the theory of an endocrine circuit with the skeleton functioning as a ductless gland. © 2022 by the authors.
    view abstractdoi: 10.3390/cells11162491
  • 2022 • 115 Progress in alumina ceramic membranes for water purification: Status and prospects
    Wang, Y. and Ma, B. and Ulbricht, M. and Dong, Y. and Zhao, X.
    Water Research 226 (2022)
    Ceramic membranes have gained increasing attention in recent years for the removal of various contaminants from water. Alumina membrane is considered as one of the most important ceramic membranes, which plays important roles not only in separation processes such as microfiltration, ultrafiltration, and nanofiltration, but also in catalysis- and adsorption- enhanced separation applications in water purification and wastewater treatment. However, there is currently still lack of a comprehensive critical review about alumina membranes for water purification. In this review, we first discuss recent developments of alumina membranes, and then critically introduce the state-of-the-art strategies for lowering fabrication cost, improving membrane performances and mitigating membrane fouling. Especially, aiming to improve membrane performance, some emerging methods are summarized such as tailoring membrane structure, developing flexible membranes, designing nano-pores for precise separation, and enhancing multi-functionalities. In addition, engineering applications of alumina membranes for water purification are also briefly introduced. Finally, the prospects for future research on alumina membranes are proposed, such as economic preparation/application, challenging precise separation, enriching multi-functionalities, and clarifying separation mechanisms. © 2022 Elsevier Ltd
    view abstractdoi: 10.1016/j.watres.2022.119173
  • 2022 • 114 Gaining the Freedom of Scalable Gas Diffusion Electrodes for the CO2 Reduction Reaction
    Wang, X. and Tomon, C. and Bobrowski, T. and Wilde, P. and Junqueira, J.R.C. and Quast, T. and He, W. and Sikdar, N. and Weidner, J. and Schuhmann, W.
    ChemElectroChem 9 (2022)
    doi: 10.1002/celc.202200675
  • 2022 • 113 Norman Chigier (1933 – 2022)
    Wang, H. and Schulz, C.
    Progress in Energy and Combustion Science 93 (2022)
    doi: 10.1016/j.pecs.2022.101041
  • 2022 • 112 Aminophosphine-based continuous liquid-phase synthesis of InP and InP/ZnS quantum dots in a customized tubular flow reactor
    Wang, Z. and Segets, D.
    Reaction Chemistry and Engineering 8 316-322 (2022)
    doi: 10.1039/d2re00378c
  • 2022 • 111 Binding Methylarginines and Methyllysines as Free Amino Acids: A Comparative Study of Multiple Host Classes**
    Warmerdam, Z. and Kamba, B.E. and Le, M.-H. and Schrader, T. and Isaacs, L. and Bayer, P. and Hof, F.
    ChemBioChem 23 (2022)
    Methylated free amino acids are an important class of targets for host-guest chemistry that have recognition properties distinct from those of methylated peptides and proteins. We present comparative binding studies for three different host classes that are each studied with multiple methylated arginines and lysines to determine fundamental structure-function relationships. The hosts studied are all anionic and include three calixarenes, two acyclic cucurbiturils, and two other cleft-like hosts, a clip and a tweezer. We determined the binding association constants for a panel of methylated amino acids using indicator displacement assays. The acyclic cucurbiturils display stronger binding to the methylated amino acids, and some unique patterns of selectivity. The two other cleft-like hosts follow two different trends, shallow host (clip) following similar trends to the calixarenes, and the other more closed host (tweezer) binding certain less-methylated amino acids stronger than their methylated counterparts. Molecular modelling sheds some light on the different preferences of the various hosts. The results identify hosts with new selectivities and with affinities in a range that could be useful for biomedical applications. The overall selectivity patterns are explained by a common framework that considers the geometry, depth of binding pockets, and functional group participation across all host classes. © 2021 The Authors. ChemBioChem published by Wiley-VCH GmbH
    view abstractdoi: 10.1002/cbic.202100502
  • 2022 • 110 A Concept for Using Road Wetness Information in an All-Wheel-Drive Control
    Warth, G. and Sieberg, P. and Unterreiner, M. and Schramm, D.
    Energies 15 (2022)
    This paper presents a concept for using road wetness information in an all-wheel-drive (AWD) control that distributes drive torques in the longitudinal direction. Driving on wet roads requires special attention. Not only does the road surface friction coefficient decrease, but driving dynamics targets must be adjusted to prevent vehicle instability under wet conditions. As an exemplary application, the otherwise generic control concept is implemented on an AWD vehicle with a torque-on-demand transfer case. Therefore, the AWD topology of a drive train with a torque-on-demand transfer case is analysed in advance in terms of occurring torques and rotational speeds. In the fol-lowing, the vehicle dynamics goals for driving in wet road conditions are described—divided into primary and secondary goals. Starting from a state-of-the art AWD control, an adaptive control strategy is derived by superimposing a wetness coordination unit. With the knowledge of occurring road wetness, this unit adapts newly introduced parameters in order to meet the target driving behaviour under wet conditions. Lastly, the derived AWD control is implemented into a 14-DOF, non-linear vehicle model in Matlab/Simulink, which is used as a virtual plant. The performance of the developed concept is assessed by the driving maneuver “Power On Cornering“ (PON), which means an acceleration out of steady-state circular motion. As its essential benefit, the AWD control enables a maximum spread between driving stability, agility and traction under combined dynamics when using wetness information. The newly introduced wetness coordination unit uses only a few additional and physically interpretable key parameters for this purpose, without significantly increasing the controller complexity. © 2022 by the authors. Licensee MDPI, Basel, Switzerland.
    view abstractdoi: 10.3390/en15041284
  • 2022 • 109 Concept of a Teleoperation System for Inland Shipping Vessels
    Weber, T. and Hurten, C. and Schramm, D.
    IEEE Conference on Intelligent Transportation Systems, Proceedings, ITSC 2022-October 349-354 (2022)
    doi: 10.1109/ITSC55140.2022.9921862
  • 2022 • 108 Joining of metal-thermoplastic-tube-joints by hydraulic expansion
    Weber, F. and Lehmenk hler, P. and Hahn, M. and Erman Tekkaya, A.
    Proceedings of ASME 2022 17th International Manufacturing Science and Engineering Conference, MSEC 2022 2 (2022)
    doi: 10.1115/MSEC2022-84991
  • 2022 • 107 Mechanical in vitro fatigue testing of implant materials and components using advanced characterization techniques
    Wegner, N. and Klein, M. and Scholz, R. and Kotzem, D. and Macias Barrientos, M. and Walther, F.
    Journal of Biomedical Materials Research - Part B Applied Biomaterials 110 898-909 (2022)
    Implants of different material classes have been used for the reconstruction of damaged hard and soft tissue for decades. The aim is to increase and subsequently maintain the patient's quality of life through implantation. In service, most implants are subjected to cyclic loading, which must be taken particularly into consideration, since the fatigue strength is far below the yield and tensile strength. Inaccurate estimation of the structural strength of implants due to the consideration of yield or tensile strength leads to a miscalculation of the implant's fatigue strength and lifetime, and therefore, to its unexpected early fatigue failure. Thus, fatigue failure of an implant based on overestimated performance capability represents acute danger to human health. The determination of fatigue strength by corresponding tests investigating various stress amplitudes is time-consuming and cost-intensive. This study summarizes four investigation series on the fatigue behavior of different implant materials and components, following a standard and an in vitro short-time testing procedure, which evaluates the material reaction in one enhanced test set-up. The test set-up and the applied characterization methods were adapted to the respective application of the implant with the aim to simulate the surrounding of the human body with laboratory in vitro tests only. It could be shown that by using the short-time testing method the number of tests required to determine the fatigue strength can be drastically reduced. In future, therefore it will be possible to exclude unsuitable implant materials or components before further clinical investigations by using a time-efficient and application-oriented testing method. © 2021 Wiley Periodicals LLC.
    view abstractdoi: 10.1002/jbm.b.34970
  • 2022 • 106 Electrochemical Short-Time Testing Method for Simulating the Degradation Behavior of Magnesium-Based Biomaterials
    Wegner, N. and Vergin, J. and Walther, F.
    Metals 12 (2022)
    In regenerative medicine, degradable, magnesium-based biomaterials represent a promising material class. The low corrosion resistance typical for magnesium is advantageous for this application since the entire implant degrades in the presence of the aqueous body fluids after fulfilling the intended function, making a second operation for implant removal obsolete. To ensure sufficient stability within the functional phase, the degradation behavior must be known for months. In order to reduce time and costs for these long-time investigations, an electrochemical short-time testing method is developed and validated, accelerating the dissolution process of a magnesium alloy with and without surface modification based on galvanostatic anodic polarization, enabling a simulation of longer immersion times. During anodic polarization, the hydrogen gas formed by the corrosion process increases linearly. Moreover, the gas volume shows a linear relationship to the dissolving mass, enabling a defined dissolution of magnesium. As a starting point, corrosion rates of both variants from three-week immersion tests are used. A simplified relationship between the current density and the dissolution rate, determined experimentally, is used to design the experiments. Ex situ µ-computed tomography scans are performed to compare the degradation morphologies of both test strategies. The results demonstrate that a simulation of the degradation rates and, hence, considerable time saving based on galvanostatic anodic polarization is possible. Since the method is accompanied by a changed degradation morphology, it is suitable for a worst-case estimation allowing the exclusion of new, unsuitable magnesium systems before subsequent preclinical studies. © 2022 by the authors. Licensee MDPI, Basel, Switzerland.
    view abstractdoi: 10.3390/met12040591
  • 2022 • 105 Post-traumatic necrosis of the humeral head-Endoprosthesis or joint preservation [Posttraumatische Humeruskopfnekrose – Endoprothese oder Gelenkerhalt]
    Wegner, A. and Wassenaar, D. and Busch, A. and Stanjek, M. and Mayer, C. and Jäger, M.
    Orthopadie (Heidelberg, Germany) 51 822-828 (2022)
    doi: 10.1007/s00132-022-04307-9
  • 2022 • 104 Structural deviations of bulk metallic glasses in downfacing surfaces fabricated via Laser Powder Bed Fusion
    Wegner, J. and Best, J.P. and Schnell, N. and Kleszczynski, S.
    Procedia CIRP 111 105-110 (2022)
    doi: 10.1016/j.procir.2022.08.147
  • 2022 • 103 Si-addition contributes to overcoming the strength-ductility trade-off in high-entropy alloys
    Wei, D. and Gong, W. and Tsuru, T. and Lobzenko, I. and Li, X. and Harjo, S. and Kawasaki, T. and Do, H.-S. and Bae, J.W. and Wagner, C. and Laplanche, G. and Koizumi, Y. and Adachi, H. and Aoyagi, K. and Chiba, A. and Lee, B.-J. ...
    International Journal of Plasticity 159 (2022)
    doi: 10.1016/j.ijplas.2022.103443
  • 2022 • 102 In Situ Analytical Methods for the Characterization of Mechanochemical Reactions
    Weidenthaler, C.
    Crystals 12 (2022)
    The interest in mechanochemical reactions and their fields of application have increased enormously in recent times. Mechanically activated reactions offer the advantage of cost-efficiency as well as environmentally friendly syntheses routes. In contrast to thermally induced processes, the energy transfer via the milling media takes place on a local scale. This leads to unique reaction pathways, which often also result in the formation of metastable phases. For the understanding of reaction pathways on a mechanistic level, it is very important to follow the processes taking place in the grinding jar during milling. Besides the measurement of pressure and temperature changes during a mechanochemical reaction, in situ high energy synchrotron X-ray powder diffraction and Raman spectroscopy experiments have been successfully implemented over the last 10 years. This review will highlight the developments which were achieved in the field of in situ monitoring of mechanochemical reactions and their input to the understanding of mechanochemistry. © 2022 by the author. Licensee MDPI, Basel, Switzerland.
    view abstractdoi: 10.3390/cryst12030345
  • 2022 • 101 In-situ Investigations of Co@Al2O3 Ammonia Decomposition Catalysts: The Interaction between Support and Catalyst
    Weidenthaler, C. and Schmidt, W. and Leiting, S. and Ternieden, J. and Kostis, A. and Ulucan, T.H. and Budiyanto, E.
    ChemCatChem 14 (2022)
    Cracking of ammonia, a hydrogen carrier with high storage capacity, gains increasing attention for fuel cell systems for heavy load transportation. In this work, we studied the influence of metal loading and synthesis temperatures on the properties of Co@Al2O3 catalysts. The combination of in situ bulk characterization methods with in situ surface spectroscopy provides insights into the structure-property relation of the Co catalyst on the γ-Al2O3 support. At too high temperatures, the formation of CoAl2O4 during synthesis or during the catalytic reaction itself results in inactive mixed metal aluminium spinels which do not contribute to the catalytic reaction. The amount of ‘active’ Co catalyst thus varies significantly as well as its catalytic activity. The latter is correlated to the size of the reduced Co particles on the alumina support. The experiments also highlight that the state of the catalyst changes after reaction which strongly emphasizes the necessity of in situ studies. © 2022 The Authors. ChemCatChem published by Wiley-VCH GmbH.
    view abstractdoi: 10.1002/cctc.202200688
  • 2022 • 100 GOAT: a multipurpose optical simulation tool
    Weigel, T. and Schweiger, G. and Ostendorf, A.
    Journal of the Optical Society of America B: Optical Physics 39 2061-2065 (2022)
    Many solutions exist for optical simulations. Many of them are isolated solutions, are complex to use due to their wide range of applications, or are difficult to adapt to new problems. Therefore, there is a need for easy-to-use, flexibly adaptable program packages. For this reason, we present here a programming library for the simulation of optical problems, which is based on geometrical optics due to its high flexibility. Special attention was paid to a flexible adaptability to different problems and an easy usability. The program package is freely available as an open-source project implemented in C++ and can be downloaded from the GitHub platform (Weigel, GitHub, 2021). © 2022 Optica Publishing Group.
    view abstractdoi: 10.1364/JOSAB.459574
  • 2022 • 99 Advanced Molecular Tweezers with Lipid Anchors against SARS-CoV-2 and Other Respiratory Viruses
    Weil, T. and Kirupakaran, A. and Le, M.-H. and Rebmann, P. and Mieres-Perez, J. and Issmail, L. and Conzelmann, C. and Müller, J.A. and Rauch, L. and Gilg, A. and Wettstein, L. and Groß, R. and Read, C. and Bergner, T. and Påls...
    Journal of the American Chemical Society 2 2187-2202 (2022)
    The COVID-19 pandemic caused by SARS-CoV-2 presents a global health emergency. Therapeutic options against SARS-CoV-2 are still very limited but urgently required. Molecular tweezers are supramolecular agents that destabilize the envelope of viruses resulting in a loss of viral infectivity. Here, we show that first-generation tweezers, CLR01 and CLR05, disrupt the SARS-CoV-2 envelope and abrogate viral infectivity. To increase the antiviral activity, a series of 34 advanced molecular tweezers were synthesized by insertion of aliphatic or aromatic ester groups on the phosphate moieties of the parent molecule CLR01. A structure-activity relationship study enabled the identification of tweezers with a markedly enhanced ability to destroy lipid bilayers and to suppress SARS-CoV-2 infection. Selected tweezer derivatives retain activity in airway mucus and inactivate the SARS-CoV-2 wildtype and variants of concern as well as respiratory syncytial, influenza, and measles viruses. Moreover, inhibitory activity of advanced tweezers against respiratory syncytial virus and SARS-CoV-2 was confirmed in mice. Thus, potentiated tweezers are broad-spectrum antiviral agents with great prospects for clinical development to combat highly pathogenic viruses. © 2022 American Chemical Society. All rights reserved.
    view abstractdoi: 10.1021/jacsau.2c00220
  • 2022 • 98 Synthesis of distibiranes and azadistibiranes by cycloaddition reactions of distibenes with diazomethanes and azides
    Weinert, H.M. and Wölper, C. and Schulz, S.
    Chemical Science 13 3775-3786 (2022)
    Cycloaddition reactions of distibene [L(Me2N)GaSb]2 (L = HC[C(Me)NDipp]2; Dipp = 2,6-i-Pr2C6H3) 00000000 00000000 00000000 00000000 11111111 00000000 11111111 00000000 00000000 00000000 with a series of organoazides RN3 (R = Ph, p-CF3Ph, 1-adamantyl (ada)) yielded azadistibiranes [L(Me2N)GaSb]2NR (R = Ph 1, p-CF3Ph 2, ada 3), whereas Me3SiN3 reacted with insertion into one Ga-Sb bond and formation of L(Me2N)GaSbSb(NSiMe3)Ga(NMe2)L (4). Analogous compounds 5 and 6 formed after heating of 1 and 2 above 60 °C. Prolonged heating of 5 resulted in a [2 + 2] cycloaddition accompanied by elimination of LGa(NMe2)2 and formation of tetrastibacyclobutane 7, while the reaction of 5 with a second equivalent of PhN3 gave heteroleptic azadistibirane 9, which isomerized at elevated temperature to distibene 10. Cycloaddition also occurred in reactions of [L(X)GaSb]2 (X = NMe2, OEt, Cl) with Me3Si(H)CN2, yielding distibiranes [L(X)GaSb]2C(H)SiMe3 (X = NMe211, OEt 12, Cl 13). Compounds 1-13 were characterized by IR, UV-Vis and NMR spectroscopy and sc-XRD. The mechanism of the reaction of [L(Me2N)GaSb]2 with PhN3 and Me3SiN3 and the electronic nature of the resulting compounds were studied by DFT calculations. © 2022 The Royal Society of Chemistry
    view abstractdoi: 10.1039/d2sc00314g
  • 2022 • 97 Flame structure analysis and flamelet modeling of turbulent pulverized solid fuel combustion with flue gas recirculation
    Wen, X. and Shamooni, A. and Nicolai, H. and Stein, O.T. and Kronenburg, A. and Kempf, A.M. and Hasse, C.
    Proceedings of the Combustion Institute (2022)
    In this work, carrier-phase direct numerical simulation (CP-DNS) is conducted for a pulverized coal flame in a temporally evolving turbulent jet with flue gas recirculation (FGR). Detailed gas phase kinetics are considered and heavy hydrocarbon molecules up to C20 are included to accurately represent tars in the volatile matter. The structure of the pulverized coal flame is analyzed with different flamelet models considering two mixing scenarios, namely the mixing of recirculated flue gases with the other fuel or oxidizer streams. In the first model approach, the mixing of recirculated flue gases with the gaseous fuels released from the coal particle is characterized with a fuel-split-based flamelet (FLT-FS) model. In the second approach, the mixing of flue gases with the transport air is described with an oxidizer-split-based flamelet (FLT-OS) model. In total, five trajectory variables are introduced in the flamelet table to represent the pulverized coal combustion states with FGR. The suitability of the flamelet models is evaluated through an a priori analysis for both the fully ignited state, as well as (more challenging) the igniting states. Comparisons show that both the FLT-FS model and the FLT-OS model perform well in predicting the thermo-chemical quantities for the fully ignited state. The FLT-OS model performs slightly better than the FLT-FS model in predicting the gas temperature and specific species mass fractions. This is due to the fact that the partial oxidization of the gaseous fuels by the hot flue gases outside the mixing layers cannot be reproduced by the FLT-FS model. While the state at the beginning of ignition can still be accurately predicted by the FLT-OS model, discrepancies can be observed for the tar species C20H10 and the intermediate species CO at a later stage when many particles ignite and the reason for this is explained. Further analysis in the flamelet solution spaces shows that the gaseous fuels are ignited on the fuel-lean side. The time evolution of the gas temperature from the beginning of ignition to the fully ignited state can be overall characterized by both flamelet models. © 2022 Elsevier Ltd. All rights reserved.
    view abstractdoi: 10.1016/j.proci.2022.07.183
  • 2022 • 96 Production of the Future - MaturityModel as an Analytical Tool [Produktion der Zukunft - Reifegradmodell als Analyseinstrument]
    Wessing, S. and Müller, E.
    ZWF Zeitschrift fuer Wirtschaftlichen Fabrikbetrieb 117 410-414 (2022)
    For the future-oriented design of value added-processes or factory planning, the current degree of implementation regarding Industry 4.0, digitalization, or sustainability is of great importance for companies. This article, therefore, analyzes the focal points for modern production processes and systems and defines the results in a pillar model entitled .,Production of the Future". This consists of nine central areas and is described in more detail by the German word composition .,LAND"(lean, automated, sustainable, and digital). To measure the current implementation status, a maturity model with five maturity levels for each section is developed based on the pillar model. For companies, the application of the maturity model offers the opportunity to determine their strengths and weaknesses regarding topics of the production of the future and, if necessary, to introduce activities for changing to modern and economic production. © 2022 Walter de Gruyter GmbH, Berlin/Boston, Germany.
    view abstractdoi: 10.1515/zwf-2022-1081
  • 2022 • 95 Covalent Allosteric Inhibitors of Akt Generated Using a Click Fragment Approach
    van der Westhuizen, L. and Weisner, J. and Taher, A. and Landel, I. and Quambusch, L. and Lindemann, M. and Uhlenbrock, N. and Müller, M.P. and Green, I.R. and Pelly, S.C. and Rauh, D. and van Otterlo, W.A.L.
    ChemMedChem (2022)
    Akt is a protein kinase that has been implicated in the progression of cancerous tumours. A number of covalent allosteric Akt inhibitors are known, and based on these scaffolds, a small library of novel potential covalent allosteric imidazopyridine-based inhibitors was designed. The envisaged compounds were synthesised, with click chemistry enabling a modular approach to a number of the target compounds. The binding modes, potencies and antiproliferative activities of these synthesised compounds were explored, thereby furthering the structure activity relationship knowledge of this class of Akt inhibitors. Three novel covalent inhibitors were identified, exhibiting moderate activity against Akt1 and various cancer cell lines, potentially paving the way for future covalent allosteric inhibitors with improved properties. © 2022 The Authors. ChemMedChem published by Wiley-VCH GmbH
    view abstractdoi: 10.1002/cmdc.202100776
  • 2022 • 94 Modified Z-phase formation in a 12% Cr tempered martensite ferritic steel during long-term creep
    Westraadt, J.E. and Goosen, W.E. and Kostka, A. and Wang, H. and Eggeler, G.
    Materials Science and Engineering A 855 (2022)
    doi: 10.1016/j.msea.2022.143857
  • 2022 • 93 Water-Based Synthesis of Ultrasmall Nanoparticles of Platinum Group Metal Oxides (1.8 nm)
    Wetzel, O. and Prymak, O. and Loza, K. and Gumbiowski, N. and Heggen, M. and Bayer, P. and Beuck, C. and Weidenthaler, C. and Epple, M.
    Inorganic Chemistry 61 5133-5147 (2022)
    doi: 10.1021/acs.inorgchem.2c00281
  • 2022 • 92 Supersolidus Liquid Phase Sintering and Heat Treatment on Atomic Diffusion Additive Manufacturing Produced Ledeburitic Cold Work Tool Steel [Supersolidus-Flüssigphasensintern und Wärmebehandlung an Atomic Diffusion Additive Manufacturing hergestelltem ledeburitischen Kaltarbeitsstahl]
    Wieczorek, L. and Katzwinkel, T. and Blüm, M. and Löwer, M. and Röttger, A.
    HTM - Journal of Heat Treatment and Materials 77 269-283 (2022)
    In this work, the possibility of manufacturing complex-shaped components from a carbon-martensitic hardenable cold-work steel (1.2379; X153CrMoV12; D2) is investigated. For this purpose, cube-shaped samples with an edge length of 10 mm were produced using the fused-filament fabrication process, which were post-compacted after solvent debinding by supersolidus liquid-phase sintering. Using the knowledge of liquid phase volume content as a function of temperature, supersolidus liquid phase sintering experiments were performed. The microstructure formation process was characterized by electron microscopy and X-ray diffraction. The microstructure and hardness of the processed samples were compared in the heat-treated condition with the properties of the same steel 1.2379 (X153CrMoV12; D2) in the as-cast, deformed and heat-treated condition. The results demonstrate effective post-densificationc close to theoretical density of cold-work tool steel samples fabricated by fused-filamet fabrication using supersolidus liquid-phase sintering at 1280 °C. The defect-free microstructure in the heat-treated state is characterized by a martensitic matrix and eutectic Cr-rich M7 C3 and small amounts of V-rich MC carbides. The hardness of the annealed Supersolidus liquid phase sintering samples are 681 ± 5 HV10, which is above the level of the reference material 1.2379 (629 ± 7 HV10) in the as-cast, formed and heat-treated condition. © 2022 L. Wieczorek, T. Katzwinkel, M. Blüm, M. Löwer, A. Röttger, publiziert von De Gruyter.
    view abstractdoi: 10.1515/htm-2022-1019
  • 2022 • 91 Design and synthesis of Nrf2-derived hydrocarbon stapled peptides for the disruption of protein-DNA-interactions
    Wiedemann, B. and Kamps, D. and Depta, L. and Weisner, J. and Cvetreznik, J. and Tomassi, S. and Gentz, S. and Hoffmann, J.-E. and Müller, M.P. and Koch, O. and Dehmelt, L. and Rauh, D.
    PLoS ONE 17 (2022)
    Misregulation and mutations of the transcription factor Nrf2 are involved in the development of a variety of human diseases. In this study, we employed the technology of stapled peptides to address a protein-DNA-complex and designed a set of Nrf2-based derivatives. Varying the length and position of the hydrocarbon staple, we chose the best peptide for further evaluation in both fixed and living cells. Peptide 4 revealed significant enrichment within the nucleus compared to its linear counterpart 5, indicating potent binding to DNA. Our studies suggest that these molecules offer an interesting strategy to target activated Nrf2 in cancer cells. Copyright: © 2022 Wiedemann et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
    view abstractdoi: 10.1371/journal.pone.0267651
  • 2022 • 90 Exploring the Impact of the Linker Length on Heat Transport in Metal-Organic Frameworks
    Wieser, S. and Kamencek, T. and Schmid, R. and Bedoya-Martínez, N. and Zojer, E.
    Nanomaterials 12 (2022)
    Metal–organic frameworks (MOFs) are a highly versatile group of porous materials suit-able for a broad range of applications, which often crucially depend on the MOFs’ heat transport properties. Nevertheless, detailed relationships between the chemical structure of MOFs and their thermal conductivities are still largely missing. To lay the foundations for developing such rela-tionships, we performed non-equilibrium molecular dynamics simulations to analyze heat transport in a selected set of materials. In particular, we focus on the impact of organic linkers, the inorganic nodes and the interfaces between them. To obtain reliable data, great care was taken to generate and thoroughly benchmark system-specific force fields building on ab-initio-based refer-ence data. To systematically separate the different factors arising from the complex structures of MOF, we also studied a series of suitably designed model systems. Notably, besides the expected trend that longer linkers lead to a reduction in thermal conductivity due to an increase in porosity, they also cause an increase in the interface resistance between the different building blocks of the MOFs. This is relevant insofar as the interface resistance dominates the total thermal resistance of the MOF. Employing suitably designed model systems, it can be shown that this dominance of the interface resistance is not the consequence of the specific, potentially weak, chemical interactions between nodes and linkers. Rather, it is inherent to the framework structures of the MOFs. These findings improve our understanding of heat transport in MOFs and will help in tailoring the thermal conductivities of MOFs for specific applications. © 2022 by the authors. Licensee MDPI, Basel, Switzerland.
    view abstractdoi: 10.3390/nano12132142
  • 2022 • 89 Weak itinerant magnetic phases of La2Ni7
    Wilde, J.M. and Sapkota, A. and Tian, W. and Bud'Ko, S.L. and Ribeiro, R.A. and Kreyssig, A. and Canfield, P.C.
    Physical Review B 106 (2022)
    La2Ni7 is an intermetallic compound that is thought to have itinerant magnetism with small moment (∼0.15μB/Ni) ordering below 65 K. A recent study of single crystal samples by Ribeiro et al. [Phys. Rev. B 105, 014412 (2022)2469-995010.1103/PhysRevB.105.014412] determined detailed anisotropic H-T phase diagrams and revealed three zero-field magnetic phase transitions at T1∼61.0 K, T2∼56.5 K, and T3∼42 K. In that study only the highest temperature phase is shown to have a clear ferromagnetic component. Here we present a single crystal neutron diffraction study determining the propagation vector and magnetic moment direction of the three magnetically ordered phases, two incommensurate and one commensurate, as a function of temperature. The higher temperature phases have similar, incommensurate propagation vectors, but with different ordered moment directions. At lower temperatures, the magnetic order becomes commensurate with magnetic moments along the c direction as part of a first-order magnetic phase transition. We find that the low-temperature commensurate magnetic order is consistent with a proposal from earlier DFT calculations. © 2022 American Physical Society.
    view abstractdoi: 10.1103/PhysRevB.106.075118
  • 2022 • 88 Canted antiferromagnetic phases in the candidate layered Weyl material EuMnSb2
    Wilde, J.M. and Riberolles, S.X.M. and Das, A. and Liu, Y. and Heitmann, T.W. and Wang, X. and Straszheim, W.E. and Bud'Ko, S.L. and Canfield, P.C. and Kreyssig, A. and McQueeney, R.J. and Ryan, D.H. and Ueland, B.G.
    Physical Review B 106 (2022)
    EuMnSb2 is a candidate topological material which can be tuned towards a Weyl semimetal, but there are differing reports for its antiferromagnetic (AFM) phases. The coupling of bands dominated by pure Sb layers hosting topological fermions to Mn and Eu magnetic states provides a potential path to tune the topological properties. Here we present single-crystal neutron diffraction, magnetization, and heat-capacity data as well as polycrystalline Eu151 Mössbauer data which show that three AFM phases exist as a function of temperature, and we present a detailed analysis of the magnetic structure in each phase. The Mn magnetic sublattice orders into a C-type AFM structure below TNMn=323(1)K with the ordered Mn magnetic moment μMn lying perpendicular to the layers. AFM ordering of the Eu sublattice occurs below TNEu1=23(1)K with the ordered Eu magnetic moment μEu canted away from the layer normal and μMn retaining its higher temperature order. μEu is ferromagnetically aligned within each Eu layer but exhibits a complicated AFM layer stacking. Both of these higher-temperature phases are described by magnetic space group (MSG) Pn′m′a′ with the chemical and magnetic unit cells having the same dimensions. Cooling below TNEu2=9(1)K reveals a third AFM phase where μMn remains unchanged but μEu develops an additional substantial in-plane canting. This phase has MSG P1121a′. We also find some evidence of short-range magnetic correlations associated with the Eu between 12K T 30K. Using the determined magnetic structures, we postulate the signs of nearest-neighbor intralayer and interlayer exchange constants and the magnetic anisotropy within a general Heisenberg model. We then discuss implications of the various AFM states in EuMnSb2 and their potential for tuning topological properties. © 2022 American Physical Society. All rights reserved.
    view abstractdoi: 10.1103/PhysRevB.106.024420
  • 2022 • 87 Amphiphilic polymer conetworks with ideal and non-ideal swelling behavior demonstrated by small angle X-ray scattering
    Wilhelm, S.A. and Maricanov, M. and Brandt, V. and Katzenberg, F. and Tiller, J.C.
    Polymer 242 (2022)
    Amphiphilic polymer conetworks (APCNs) combine two incompatible properties within one material by featuring two interconnected independently swelling nanophases. To simultaneously address both properties, the APCNs need to be swellable in orthogonal solvents without changing their nanostructure. This has not been demonstrated yet. Two novel APCN families applying the macromeric cross-linker approach have been synthesized by cross-linking the hydrophilic poly(2-hydroxyethyl acrylate) (PHEA) or poly(N,N-dimethylacrylamide) (PDMA), respectively, with the hydrophobic poly(2-(1-ethylpentyl)-2-oxazoline) (PEPOx). For the first time, the APCN PHEA-l-PEPOx could be proven to swell in two orthogonal solvents, water and n-heptane, retaining its nanostructure in a broad range of compositions by using small-angle X-ray scattering (SAXS). PDMA-l-PEPOx seems to show a similar behavior according to swelling experiments, but SAXS revealed that particularly the PDMA phase reversibly changes its nanostructure upon swelling. Thus, the structural integrity of APCNs upon swelling depends on the topology as well as the chemical nature of the polymer phases. Altogether, SAXS experiments are required and well suited to judge changes in nanostructure upon swelling of APCNs. © 2022
    view abstractdoi: 10.1016/j.polymer.2022.124582
  • 2022 • 86 In-line monitoring of solid dispersion preparation in small scale extrusion based on UV–vis spectroscopy
    Winck, J. and Daalmann, M. and Berghaus, A. and Thommes, M.
    Pharmaceutical Development and Technology 27 1009-1015 (2022)
    doi: 10.1080/10837450.2022.2144887
  • 2022 • 85 Simulation of crack propagation based on eigenerosion in brittle and ductile materials subject to finite strains
    Wingender, D. and Balzani, D.
    Archive of Applied Mechanics (2022)
    In this paper, a framework for the simulation of crack propagation in brittle and ductile materials is proposed. The framework is derived by extending the eigenerosion approach of Pandolfi and Ortiz (Int J Numer Methods Eng 92(8):694–714, 2012. https://doi.org/10.1002/nme.4352) to finite strains and by connecting it with a generalized energy-based, Griffith-type failure criterion for ductile fracture. To model the elasto-plastic response, a classical finite strain formulation is extended by viscous regularization to account for the shear band localization prior to fracture. The compression–tension asymmetry, which becomes particularly important during crack propagation under cyclic loading, is incorporated by splitting the strain energy density into a tensile and compression part. In a comparative study based on benchmark problems, it is shown that the unified approach is indeed able to represent brittle and ductile fracture at finite strains and to ensure converging, mesh-independent solutions. Furthermore, the proposed approach is analyzed for cyclic loading, and it is shown that classical Wöhler curves can be represented. © 2022, The Author(s).
    view abstractdoi: 10.1007/s00419-021-02101-1
  • 2022 • 84 Simulation of crack propagation through voxel-based, heterogeneous structures based on eigenerosion and finite cells
    Wingender, D. and Balzani, D.
    Computational Mechanics 70 385-406 (2022)
    doi: 10.1007/s00466-022-02172-z
  • 2022 • 83 Magnetic response of CoFe2O4nanoparticles confined in a PNIPAM microgel network
    Witt, M.U. and Landers, J. and Hinrichs, S. and Salamon, S. and Kopp, J. and Hankiewicz, B. and Wende, H. and Von Klitzing, R.
    Soft Matter 18 1089-1099 (2022)
    The paper addresses coupling of magnetic nanoparticles (MNPs) with the polymer matrix of temperature-sensitive microgels and their response to magnetic fields. Therefore, CoFe2O4@CA (CA = citric acid) NPs are embedded within N-isopropylacrylamid (NIPAM) based microgels. The volume phase transition (VPT) of the magnetic microgels and the respective pure microgels is studied by dynamic light scattering and electrophoretic mobility measurements. The interaction between MNPs and microgel network is studied via magnetometry and AC-susceptometry using a superconducting quantum interference device (SQUID). The data show a significant change of the magnetic properties by crossing the VPT temperature (VPTT). The change is related to the increased confinement of the MNP due to the shrinking of the microgels. Modifying the microgel with hydrophobic allyl mercaptan (AM) affects the swelling ability and the magnetic response, i.e. the coupling of MNPs with the polymer matrix. Modeling the AC-susceptibility data results in an effective size distribution. This distribution represents the varying degree of constraint in MNP rotation and motion by the microgel network. These findings help to understand the interaction between MNPs and the microgel matrix to design multi responsive systems with tunable particle matrix coupling strength for future applications. This journal is © The Royal Society of Chemistry.
    view abstractdoi: 10.1039/d1sm01597d
  • 2022 • 82 Preparation of N-doped carbon materials from cellulose:chitosan blends and their potential application in electrocatalytic oxygen reduction
    Wittmar, A.S.M. and Ropertz, M. and Braun, M. and Hagemann, U. and Andronescu, C. and Ulbricht, M.
    Polymer Bulletin (2022)
    doi: 10.1007/s00289-022-04429-2
  • 2022 • 81 From Inert to Catalytically Active Milling Media: Galvanostatic Coating for Direct Mechanocatalysis
    Wohlgemuth, M. and Mayer, M. and Rappen, M. and Schmidt, F. and Saure, R. and Grätz, S. and Borchardt, L.
    Angewandte Chemie - International Edition (2022)
    doi: 10.1002/anie.202212694
  • 2022 • 80 Entropy Profiling for the Diagnosis of NCA/Gr-SiOx Li-Ion Battery Health
    Wojtala, M.E. and Zülke, A.A. and Burrell, R. and Nagarathinam, M. and Li, G. and Hoster, H.E. and Howey, D.A. and Mercer, M.P.
    Journal of the Electrochemical Society 169 (2022)
    doi: 10.1149/1945-7111/ac87d1
  • 2022 • 79 Factors Influencing the Crystallization-Onset Time of Metastable ASDs
    Wolbert, F. and Fahrig, I.-K. and Gottschalk, T. and Luebbert, C. and Thommes, M. and Sadowski, G.
    Pharmaceutics 14 (2022)
    In formulation development, amorphous solid dispersions (ASD) are considered to improve the bioavailability of poorly water-soluble active pharmaceutical ingredients (APIs). However, the crystallization of APIs often limits long-term stability and thus the shelf life of ASDs. It has already been shown earlier that the long-term stability of ASDs strongly depends on the storage conditions (relative humidity, temperature), the manufacturing methods, and the resulting particle sizes. In this work, ASDs composed of the model APIs Griseofulvin (GRI) or Itraconazole (ITR) and the polymers poly (vinylpyrrolidone-co-vinyl acetate) (PVPVA) or Soluplus® were manufactured via spray drying and hot-melt extrusion. Each API/polymer combination was manufactured using the two manufacturing methods with at least two different API loads and two particle-size distributions. It was a priori known that these ASDs were metastable and would crystallize over time, even in the dry stage. The amount of water absorbed by the ASD from humid air (40◦ C/75% relative humidity), the solubility of the API in the ASD at humid conditions, and the resulting glass-transition temperature were predicted using the Perturbed-Chain Statistical Associating Fluid Theory (PC-SAFT) and the Gordon–Taylor approach, respectively. The onset of crystallization was determined via periodic powder X-ray diffraction (PXRD) measurements. It was shown that simple heuristics such as “larger particles always crystallize later than smaller particles” are correct within one manufacturing method but cannot be transferred from one manufacturing method to another. Moreover, amorphous phase separation in the ASDs was shown to also influence their crystallization kinetics. Counterintuitively, phase separation accelerated the crystallization time, which could be explained by the glass-transition temperatures of the evolving phases. © 2022 by the authors. Licensee MDPI, Basel, Switzerland.
    view abstractdoi: 10.3390/pharmaceutics14020269
  • 2022 • 78 The Shelf Life of ASDs: 1. Measuring the Crystallization Kinetics at Humid Conditions
    Wolbert, F. and Nikoleit, K. and Steinbrink, M. and Luebbert, C. and Sadowski, G.
    Molecular Pharmaceutics 19 2483-2494 (2022)
    Amorphous solid dispersions (ASDs), where an active pharmaceutical ingredient (API) is dissolved in a polymer, are a favored formulation technique to achieve sufficient bioavailability of poorly water-soluble APIs. The shelf life of such ASDs is often limited by API crystallization. Crystallization depends strongly on the storage conditions (relative humidity and temperature) and the polymer selected for generating the ASD. Determining the crystallization kinetics of ASDs under various conditions requires suitable analytical methods. In this work, two different analytical methods were compared and cross-validated: The first builds on water-sorption measurements combined with thermodynamic predictions (Eur. J. Pharm. Biopharm. 2018, 127, 183-193, DOI: 10.1016/j.toxrep.2018.11.002), whereas the second applies Raman spectroscopy. Using the two independent methods, factors influencing the crystallization kinetics of ASDs containing the API griseofulvin were investigated quantitatively. It was found that crystallization kinetics increases with increasing temperature and relative humidity. Additionally, the influence of different polymers (poly(vinylpyrrolidone-co-vinyl acetate) and Soluplus) on crystallization kinetics were investigated. The experimentally obtained crystallization kinetics were described using the Johnson-Mehl-Avrami-Kolmogorov model and are the basis for future shelf life predictions at desired storage conditions. © 2022 The Authors. Published by American Chemical Society.
    view abstractdoi: 10.1021/acs.molpharmaceut.2c00188
  • 2022 • 77 Silencing of proinflammatory NF-κB and inhibition of herpes simplex virus (HSV) replication by ultrasmall gold nanoparticles (2 nm) conjugated with small-interfering RNA
    Wolff, N. and Kollenda, S. and Klein, K. and Loza, K. and Heggen, M. and Brochhagen, L. and Witzke, O. and Krawczyk, A. and Hilger, I. and Epple, M.
    Nanoscale Advances (2022)
    doi: 10.1039/d2na00250g
  • 2022 • 76 Operando electrochemical SERS monitors nanoparticle reactions by capping agent fingerprints
    Wonner, K. and Murke, S. and Alfarano, S.R. and Hosseini, P. and Havenith, M. and Tschulik, K.
    Nano Research (2022)
    Nanomaterials are frequently employed in daily life goods, including health, textile, and food industry. A comprehensive picture is lacking on the role of the capping agents, added ligand molecules, in case of nanoparticle reactions and degradation in aqueous solutions, like surface waters or biofluids. Here, we aim to elucidate the capping agent influence on nanoparticle reactivity probing two commonly employed capping agents citrate and polyvinylpyrrolidone (PVP). Their influence on silver nanoparticle (AgNP) transformation is studied, which is particularly important due to its application as an antimicrobial agent. We induce oxidation and reduction processes of AgNPs in halide solutions and we monitor the associated transformations of particles and capping agents by spectro-electrochemical surface-enhanced Raman spectroscopy (SERS). Raman bands of the capping agents are used here to track chemical changes of the nanoparticles under operando conditions. The sparingly soluble and non-plasmon active silver salts (AgBr and AgCl) are formed under potential bias. In addition, we spectroscopically observe plasmon-mediated structural changes of citrate to cis- or trans-aconitate, while PVP is unaltered. The different behavior of the capping agents implies a change in the physical properties on the surface of AgNPs, in particular with respect to the surface accessibility. Moreover, we showcase that reactions of the capping agents induced by different external stimuli, such as applied bias or laser irradiation, can be assessed. Our results demonstrate how SERS of capping agents can be exploited to operando track nanoparticle conversions in liquid media. This approach is envisaged to provide a more comprehensive understanding of nanoparticle fates in complex liquid environments and varied redox conditions. [Figure not available: see fulltext.] © 2021, The Author(s).
    view abstractdoi: 10.1007/s12274-021-3999-2
  • 2022 • 75 The Influence of Nanoconfinement on Electrocatalysis
    Wordsworth, J. and Benedetti, T.M. and Somerville, S.V. and Schuhmann, W. and Tilley, R.D. and Gooding, J.J.
    Angewandte Chemie - International Edition 61 (2022)
    The use of nanoparticles and nanostructured electrodes are abundant in electrocatalysis. These nanometric systems contain elements of nanoconfinement in different degrees, depending on the geometry, which can have a much greater effect on the activity and selectivity than often considered. In this Review, we firstly identify the systems containing different degrees of nanoconfinement and how they can affect the activity and selectivity of electrocatalytic reactions. Then we follow with a fundamental understanding of how electrochemistry and electrocatalysis are affected by nanoconfinement, which is beginning to be uncovered, thanks to the development of new, atomically precise manufacturing and fabrication techniques as well as advances in theoretical modeling. The aim of this Review is to help us look beyond using nanostructuring as just a way to increase surface area, but also as a way to break the scaling relations imposed on electrocatalysis by thermodynamics. © 2022 The Authors. Angewandte Chemie International Edition published by Wiley-VCH GmbH.
    view abstractdoi: 10.1002/anie.202200755
  • 2022 • 74 Controlled Synthesis of Chromium-Oxide-Based Protective Layers on Pt: Influence of Layer Thickness on Selectivity
    Worsley, M. and Smulders, V. and Mei, B.
    Catalysts 12 (2022)
    Chromium-oxyhydroxide (CrxOyHz)-based thin films have previously been shown in photocatalysis and industrial chlorate production to prevent unwanted reduction reactions to occur, thereby enhancing the selectivity for hydrogen evolution and thus the overall process efficiency. Here, a highly reproducible synthesis protocol was developed to allow for the electrodeposition of CrxOyHz-based thin films with controlled thickness in the range of the sub-monolayer up to (&gt;4) multilayer coverage. Electrodeposited CrxOyHz coatings were electrochemically characterized using voltammetry and stripping experiments, allowing thickness-dependent film selectivity to be deduced in detail. The results are discussed in terms of mass transport properties and structure of the electrodeposited chromium oxyhydroxide films. It is shown that the permeation of diatomic probe molecules, such as O2 and CO, was significantly reduced by films as thin as four monolayers. Importantly, it is shown that the prepared thin film coatings enabled prolonged hydrogen oxidation in the presence of CO (up to 5 vol.%), demonstrating the benefits of thin-film-protected electrocatalysts. In general, this study provides insight into the synthesis and use of thin-film-protected electrodes leading to improvements in (electro)catalyst selectivity and durability. © 2022 by the authors.
    view abstractdoi: 10.3390/catal12101077
  • 2022 • 73 Ferromagnetic Cobalt Disulfide: A CVD Pathway Toward High-Quality and Phase-Pure Thin Films
    Wree, J.-L. and Glauber, J.-P. and Zanders, D. and Rogalla, D. and Becher, M. and Griffiths, M.B.E. and Ostendorf, A. and Barry, S.T. and Ney, A. and Devi, A.
    ACS Applied Electronic Materials 4 3772-3779 (2022)
    doi: 10.1021/acsaelm.2c00685
  • 2022 • 72 Plasma-Enhanced Atomic Layer Deposition of Molybdenum Oxide Thin Films at Low Temperatures for Hydrogen Gas Sensing
    Wree, J.-L. and Rogalla, D. and Ostendorf, A. and Schierbaum, K.D. and Devi, A.
    ACS Applied Materials and Interfaces (2022)
    doi: 10.1021/acsami.2c19827
  • 2022 • 71 First paleoparasitological evidence of Muellerius sp. in sheep or goat dated to the Sasanian Empire (500 CE) in ancient Iran
    Wu, T.K. and Heidari, Z. and Makki, M.S. and Yazdi, B. and Aali, A. and Stöllner, T. and Boenke, N. and Bowman, D.D. and Mowlavi, G.
    Veterinary Parasitology: Regional Studies and Reports 34 (2022)
    A fecal pellet was recovered in an ancient salt mine in Chehrabad located in western Iran (36.55° N, 47.51° E). Based on prior publications showing the success of the salt mine's environment to preserve various life forms, it was decided to try and ascertain whether this faex contained any parasites of paleoparasitologic interest. The rehydration involved placing the pellet in an aqueous solution of 0.5% trisodium phosphate for a week, followed by the examination of aliquots of the entire rehydrated sample on a total of 153 microscope slides. The examination of the rehydrated material revealed the presence of two larval nematodes; there were no eggs or oocysts recovered. The larvae were photographed and measured, and the decision was made not to submit the two larvae to grinding and DNA extraction for molecular diagnostics due to their excellent state of preservation. The larvae were identified as first-stage larvae that appear to represent the genus Muellerius. Herein are reported the finding of two first-stage larvae of Muellerius nematodes (Metastrongyloidea, Protostrongylidae) from the rehydrated fecal pellet collected in a Chehrabad salt mine from the era of the Sasanian Empire. © 2022 Elsevier B.V.
    view abstractdoi: 10.1016/j.vprsr.2022.100758
  • 2022 • 70 Long-term direct ultrafiltration without chemical cleaning for purification of micro-polluted water in rural regions: Feasibility and application prospects
    Wu, S. and Lu, C. and Ma, B. and Liu, R. and Hu, C. and Ulbricht, M. and Qu, J.
    Chemical Engineering Journal 443 (2022)
    Water treatment technologies that feature a simple operation, affordable cost, and low chemical addition are necessary to achieve the goal of supplying clean water to rural regions. In this study, an automated-control direct ultrafiltration (UF) process without chemical cleaning was operated and investigated using the micro-polluted surface water at a mountain village in China as feed. During the approximately 2.5-year operation, the UF process operated steady without pretreatment and chemical cleaning, and clean drinking water that met the Chinese drinking water standard (GB 5749–2006) was continuously available. Despite occasional shock loading (84.7 NTU), the turbidity (the major contaminant of feed water) was low (0.3 ± 0.1 NTU) in the effluent, and the filtration resistance remained at (14.7 ± 0.7) × 1012 m−1 except for the initial increase. Compared with organic substances, inorganic substances were dominant constituents of cake layer. Alumina or silica particles were easily removed by frequent backwashing and were distributed on the outer surface (newly formed) of cake layer. In contrast, the bulk cake layer was predominantly composed of CaCO3 scales, indicating its major role in membrane fouling. Regarding organic fouling, low-molecular-weight hydrophilic carbohydrate-like compounds, which were related to bacterial activities, were dominant compositions (91.5%). Proteobacteria made a major contribution to bacterial communities (52.2%). Because of the simple process (almost unattended) and no chemical cleaning, the operation and maintenance cost was only 5.3 cents·m−3 during the entire operation. These findings demonstrate that direct UF without chemical cleaning has significant application potential in rural regions with micro-polluted water. © 2022 Elsevier B.V.
    view abstractdoi: 10.1016/j.cej.2022.136531
  • 2022 • 69 LUBAC assembles a ubiquitin signaling platform at mitochondria for signal amplification and transport of NF-κB to the nucleus
    Wu, Z. and Berlemann, L.A. and Bader, V. and Sehr, D.A. and Dawin, E. and Covallero, A. and Meschede, J. and Angersbach, L. and Showkat, C. and Michaelis, J.B. and Münch, C. and Rieger, B. and Namgaladze, D. and Herrera, M.G. and...
    EMBO Journal 41 (2022)
    doi: 10.15252/embj.2022112006
  • 2022 • 68 Human Detection with A Feedforward Neural Network for Small Microcontrollers
    Wulfert, L. and Wiede, C. and Verbunt, M.H. and Gembaczka, P. and Grabmaier, A.
    2022 7th International Conference on Frontiers of Signal Processing, ICFSP 2022 14-22 (2022)
    doi: 10.1109/ICFSP55781.2022.9924667
  • 2022 • 67 Activation and Stabilization of Lipase B from Candida antarctica by Immobilization on Polymer Brushes with Optimized Surface Structure
    Wunschik, D.S. and Lorenz, A. and Ingenbosch, K.N. and Gutmann, J.S. and Hoffmann-Jacobsen, K.
    Applied Biochemistry and Biotechnology 194 3384-3399 (2022)
    doi: 10.1007/s12010-022-03913-9
  • 2022 • 66 Model for non-equilibrium vacancy diffusion applied to study the Kirkendall effect in high-entropy alloys
    Xia, C.-H. and Kundin, J. and Steinbach, I. and Divinski, S.
    Acta Materialia 232 (2022)
    The effect of the non-equilibrium vacancy on the Kirkendall porosity formation was studied by means of a developed model of the multi-component diffusion with vacancies (MDV) which includes the intrinsic fluxes with vacancy gradient and non-ideal sources and sinks for vacancies. For this study, the diffusion couple experiments in multi-component alloys were chosen. To handle the case of concentration-dependent equilibrium vacancy concentration, we introduced the interaction parameters between the components and vacancies, which can have strong effects on the equilibrium vacancy concentration in alloys and on thermodynamic factors. The diffusion profiles of components and vacancies were simulated by using thermodynamic and kinetic data. The different intensity of the vacancy annihilation/generation and different initial vacancy distributions were considered. Furthermore, we show that the conventional model of diffusion in multi-component systems is a particular case of the MDV with a specific sink/source term. The conventional model was extended by the vacancy diffusion term, similar to the MDV, which significantly reduces the vacancy gradient and the pore formation near the Matano plane. The numerical results demonstrate that the diffusion profiles of substitutional components slightly depend on the sink/source intensity if the none-zero net flux of substitutional components is not significant and the sources and sinks of vacancies are not sparse, whereas the porosity depends very strongly and correlates with the vacancy distribution. For the simulation of variable equilibrium vacancy concentrations using the MDV, the corresponding interaction parameters related to vacancies are necessary to be included in the thermodynamic assessment. © 2022 Acta Materialia Inc.
    view abstractdoi: 10.1016/j.actamat.2022.117966
  • 2022 • 65 3D atomic-scale imaging of mixed Co-Fe spinel oxide nanoparticles during oxygen evolution reaction
    Xiang, W. and Yang, N. and Li, X. and Linnemann, J. and Hagemann, U. and Ruediger, O. and Heidelmann, M. and Falk, T. and Aramini, M. and DeBeer, S. and Muhler, M. and Tschulik, K. and Li, T.
    Nature Communications 13 (2022)
    The three-dimensional (3D) distribution of individual atoms on the surface of catalyst nanoparticles plays a vital role in their activity and stability. Optimising the performance of electrocatalysts requires atomic-scale information, but it is difficult to obtain. Here, we use atom probe tomography to elucidate the 3D structure of 10 nm sized Co2FeO4 and CoFe2O4 nanoparticles during oxygen evolution reaction (OER). We reveal nanoscale spinodal decomposition in pristine Co2FeO4. The interfaces of Co-rich and Fe-rich nanodomains of Co2FeO4 become trapping sites for hydroxyl groups, contributing to a higher OER activity compared to that of CoFe2O4. However, the activity of Co2FeO4 drops considerably due to concurrent irreversible transformation towards CoIVO2 and pronounced Fe dissolution. In contrast, there is negligible elemental redistribution for CoFe2O4 after OER, except for surface structural transformation towards (FeIII, CoIII)2O3. Overall, our study provides a unique 3D compositional distribution of mixed Co-Fe spinel oxides, which gives atomic-scale insights into active sites and the deactivation of electrocatalysts during OER. © 2022, The Author(s).
    view abstractdoi: 10.1038/s41467-021-27788-2
  • 2022 • 64 Molecular Emissions from Stretched Excitation Pulse in Nanosecond Phase-Selective Laser-Induced Breakdown Spectroscopy of TiO2 Nanoaerosols
    Xiong, G. and Zhang, Y. and Schulz, C. and Tse, S.D.
    Applied Spectroscopy (2022)
    In phase-selective laser-induced breakdown spectroscopy (PS-LIBS), gas-borne nanoparticles are irradiated with laser pulses (∼2.4 GW/cm2) resulting in breakdown of the nanoparticle phase but not the surrounding gas phase. In this work, the effect of excitation laser-pulse duration and energy on the intensity and duration of TiO2–nanoparticle PS-LIBS emission signal is investigated. Laser pulses from a frequency-doubled neodymium-doped yttrium aluminum garnet (Nd:YAG) laser (532 nm) are stretched from 8 ns (full width at half maximum, FWHM) up to ∼30 ns at fixed pulse energy using combinations of two optical cavities. The intensity of the titanium atomic emissions at around 500 nm wavelength increases by ∼60%, with the stretched pulse and emissions at around 482 nm, attributed to TiO, enhanced over 10 times. While the atomic emissions rise with the stretched laser pulse and decay around 20 ns after the end of the laser pulse, the TiO emissions reach their peak intensity at about 20 ns later and last longer. At low laser energy (i.e., 1 mJ/pulse, or 80 MW/cm2), the TiO emissions dominate, but their increase with laser energy is lower compared to the atomic emissions. The origin of the 482 nm emission is explored by examining several different aerosol setups, including Ti–O, Ti–N, and Ti–O–N from a spark particle generator and Ti–O–N–C–H aerosol from flame synthesis. The 482 nm emissions are attributed to electronically excited TiO, likely resulting from the reaction of excited titanium atoms with surrounding oxidizing (carbonaceous and/or radical) species. The effects of pulse length are attributed to the shift of absorption from the initial interaction with the particle to the prolonged interaction with the plasma through inverse bremsstrahlung. © The Author(s) 2022.
    view abstractdoi: 10.1177/00037028211072583
  • 2022 • 63 A reliable and unobtrusive approach to display area detection for imperceptible display camera communication
    Xu, J. and Klein, J. and Jochims, J. and Weissner, N. and Kays, R.
    Journal of Visual Communication and Image Representation 85 (2022)
    Object framework detection has been extensively studied in computer vision for applications such as document digitization and whiteboard scanning. Similarly, it is essential for display-camera communication systems, particularly when imperceptible data modulation is employed to enable simultaneous video playback and data transmission. Reliable and accurate localization of the encoded display area is critical for data demodulation and decoding. However, existing systems typically adapt established methods developed for other applications that do not meet the system requirements for high-rate data transmission. In this article, we propose a novel method for display area detection in the camera images by embedding a new localization marker into the display corners. While the localization marker is less obtrusive than conventional fiducial markers, our detection algorithm demonstrated excellent reliability regardless of the display content and background, according to simulation and experimental results. In addition, the detector achieved subpixel accuracy and real-time performance with modern smartphones. © 2022 Elsevier Inc.
    view abstractdoi: 10.1016/j.jvcir.2022.103510
  • 2022 • 62 Symbol Position Recovery for Optical Camera Communication with High-Density Matrix Codes
    Xu, J. and Brauers, C. and Klein, J. and Jochims, J. and Kays, R.
    IEEE Transactions on Circuits and Systems for Video Technology 1-1 (2022)
    doi: 10.1109/TCSVT.2022.3231648
  • 2022 • 61 Coherent Phononics of van der Waals Layers on Nanogratings
    Yan, W. and Akimov, A.V. and Barra-Burillo, M. and Bayer, M. and Bradford, J. and Gusev, V.E. and Hueso, L.E. and Kent, A. and Kukhtaruk, S. and Nadzeyka, A. and Patanè, A. and Rushforth, A.W. and Scherbakov, A.V. and Yaremkevich...
    Nano Letters 22 6509-6515 (2022)
    doi: 10.1021/acs.nanolett.2c01542
  • 2022 • 60 A study into the FSI modelling of flat plate water entry and related uncertainties
    Yan, D. and Mikkola, T. and Lakshmynarayanana, A. and Tödter, S. and Schellin, T.E. and Neugebauer, J. and Moctar, O.E. and Hirdaris, S.
    Marine Structures 86 (2022)
    doi: 10.1016/j.marstruc.2022.103296
  • 2022 • 59 Fabrication of thin sheets of the sodium superionic conductor Na5YSi4O12 with tape casting
    Yang, A. and Ye, R. and Li, X. and Lu, Q. and Song, H. and Grüner, D. and Ma, Q. and Tietz, F. and Fattakhova-Rohlfing, D. and Guillon, O.
    Chemical Engineering Journal 435 (2022)
    All-solid-state sodium batteries (ASSNBs), which combine the benefits of high safety and low cost, are expected to be an alternative or complementary storage technology to lithium ion batteries. Herein, we developed an aqueous tape casting technique for the continuous fabrication of ceramic sheets made of silicate-based Na5YSi4O12 (NYS) Na+ ion superionic conductor for the first time. After sintering, the ceramics showed a total conductivity of 1.0 mS cm−1 at room-temperature, low total activation energy of 0.30 eV, and wide electrochemical window of over 8 V. The critical current density of NYS tape against Na-metal electrodes can reach 2.2 mA cm−2 and the galvanostatic cycling time is over 280 h under 0.8 mA cm−2 and 0.8 mAh cm−2. The obtained tape has high crystalline purity, dense microstructure, favorable mechanical properties (hardness H of 2 GPa and elastic modulus E of 45 GPa). This work not only highlights the potential of the scarcely studied silicate-based NYS ionic conductor as a functional separator, but also presents a cost-efficient and eco-friendly continuous fabrication using the aqueous tape casting technique, thus being expected to boost the practical application of NYS as solid-state electrolyte in ASSNBs. © 2022 Elsevier B.V.
    view abstractdoi: 10.1016/j.cej.2022.134774
  • 2022 • 58 Normal Indentation of Rock Specimens with a Blunt Tool: Role of Specimen Size and Indenter Geometry
    Yang, H. and Renner, J. and Brackmann, L. and Röttger, A.
    Rock Mechanics and Rock Engineering 55 2027-2047 (2022)
    Indentation testing has been widely used in laboratory environments to investigate the processes leading to rock fragmentation in drilling, mechanized tunneling, and mining. Rock specimens for laboratory testing are limited to finite size, potentially causing size effects that have to be accounted for when transferring results to in situ applications. We present an integrated experimental and theoretical investigation of the specimen size effect in indentation testing (a) to address the limited understanding of its causes and the lack of tools to analyze tests on variable specimen sizes and (b) to identify to what extent an indenter mimicking the shape of a cutter on a tunneling machine can be approximated by a conventional indenter geometry. We performed indentation tests on cylindrical specimens of a porous sandstone with aspect ratios (diameter/height) ranging from 0.3 to 1.7, using a blunt-truncated indenter and monitoring the fracturing process by the acoustic emission technique. A damage zone, enclosing a zone of crushed grains immediately below the indenter tip, forms and grows due to tool penetration. Eventually, all specimens failed as a result of the propagation of a sub-vertical fracture, initiated close to peak indentation pressure. Peak force, its corresponding penetration depth, and peak indentation pressure increase with specimen size, more significantly with specimen diameter than with height. We developed a semi-analytical model based on cavity-expansion theory and linear elastic fracture mechanics for the formation of the damage zone and the nucleation and propagation of the macroscopic vertical fracture, respectively, whose predictions are in good agreement with our experimental data. The observed increases of peak indentation pressure with specimen size can be explained by the effect of the free surfaces on damage zone growth rather than on fracture propagation. The model permits evaluating the specimen size effect through the ratio between two geometrical parameters, specimen diameter and tip width of the truncated indenter, which has to be larger than around 102 for the size effect to be insignificant. The model permits upscaling of experimental results to in situ conditions based on geometrical indenter parameters and commonly used material parameters. © 2022, The Author(s), under exclusive licence to Springer-Verlag GmbH Austria, part of Springer Nature.
    view abstractdoi: 10.1007/s00603-021-02732-4
  • 2022 • 57 Evolution of an industrial-grade Zr-based bulk metallic glass during multiple laser beam melting
    Yang, Z. and Wang, H. and Krauß, S. and Huber, F. and Merle, B. and Schmidt, M. and Markl, M. and Körner, C.
    Journal of Non-Crystalline Solids 589 (2022)
    Selective laser melting (SLM), taking advantage of its inherent rapid cooling rates and near-net-shape forming ability, has been employed to fabricate bulk metallic glasses (BMGs). However, crystallization is frequently triggered during the SLM process, which results in the loss of advantageous properties of BMGs, such as extremely high hardness and near-theoretical yield strength. Although many studies have been conducted to investigate SLM of BMGs, there is still a lack of knowledge about the microstructural and compositional evolution during the laser beam processing, particularly the micromechanical property response upon crystallization. In the present work, a systematic investigation is performed to gain a much better understanding about the evolution of microstructure and composition as well as the corresponding micromechanical property change during multiple laser beam melting. The material used in this study is an industrial-grade Zr-based BMG Zr59.3Cu28.8Al10.4Nb1.5 (AMZ4) with two different oxygen levels. AMZ4 demonstrates its good thermal stability by the fact that observable crystalline structure appears around the melt pool only after more than once laser beam treatment. The compositional stability of AMZ4 is manifested by the homogeneous elemental distribution on the melt pool area after even twenty-five laser beam remelting. The laser-metal interaction, melting and subsequent solidification are not effectively influenced by the emerging and expanding of crystallization zone (or heat affected zone, HAZ). Higher oxygen content results in not only a larger HAZ but also more quenched-in nuclei at the melt pool bottom. The HAZ does not exhibit a fully crystallized structure, but rather has a mixture of amorphous and crystalline phases. Crystallization of AMZ4 leads to an increase in hardness and Young's modulus of the material. © 2022 Elsevier B.V.
    view abstractdoi: 10.1016/j.jnoncrysol.2022.121649
  • 2022 • 56 8.7-W average power, in-band pumped femtosecond Ho:CALGO laser at 2.1 µm
    Yao, W. and Wang, Y. and Tomilov, S. and Hoffmann, M. and Ahmed, S. and Liebald, C. and Rytz, D. and Peltz, M. and Wesemann, V. and Saraceno, C.J.
    Optics Express 30 41075-41083 (2022)
    doi: 10.1364/OE.471341
  • 2022 • 55 Stochastic behavior of an interface-based memristive device
    Yarragolla, S. and Hemke, T. and Trieschmann, J. and Zahari, F. and Kohlstedt, H. and Mussenbrock, T.
    Journal of Applied Physics 131 (2022)
    A large number of simulation models have been proposed over the years to mimic the electrical behavior of memristive devices. The models are based either on sophisticated mathematical formulations that do not account for physical and chemical processes responsible for the actual switching dynamics or on multi-physical spatially resolved approaches that include the inherent stochastic behavior of real-world memristive devices but are computationally very expensive. In contrast to the available models, we present a computationally inexpensive and robust spatially 1D model for simulating interface-type memristive devices. The model efficiently incorporates the stochastic behavior observed in experiments and can be easily transferred to circuit simulation frameworks. The ion transport, responsible for the resistive switching behavior, is modeled using the kinetic cloud-in-a-cell scheme. The calculated current-voltage characteristics obtained using the proposed model show excellent agreement with the experimental findings. © 2022 Author(s).
    view abstractdoi: 10.1063/5.0084085
  • 2022 • 54 Physics inspired compact modelling of BiFeO 3 based memristors
    Yarragolla, S. and Du, N. and Hemke, T. and Zhao, X. and Chen, Z. and Polian, I. and Mussenbrock, T.
    Scientific Reports 12 (2022)
    doi: 10.1038/s41598-022-24439-4
  • 2022 • 53 Pseudoelastic cycling of ultra-fine-grained NiTi shape-memory wires
    Yawny, A. and Sade, M. and Eggeler, G.
    International Journal of Materials Research 96 608-618 (2022)
    In the present study, we investigate pseudoelastic pull-pull cycling of ultra-fine-grained (40 nm) Ni-rich (50.9 at.% Ni) NiTi shape-memory wires at temperatures ranging from 301 to 323 K. Strain-controlled experiments were performed using incremental strain steps and different constant maximum strains. Pull-pull cycling results in decreasing/increasing plateau stresses characterizing the forward/reverse transformations and an accumulation of non-recoverable strain. Saturation is reached after 30 cycles. We interpret our results in terms of a microstructural scenario where dislocations, which are introduced during the martensitic transformation (lattice invariant shear) and during pull-pull cycling (dislocation plasticity), interact with the stress-induced formation of martensite. We show that the slopes of stress-strain curves naturally depend on the total strain imposed in strain-controlled testing. We also provide a dislocation-based explanation for the evolving stress levels of the loading and unloading plateaus during pseudoelastic cycling. And most importantly, we show how dislocations act as microstructural markers which allow the material to remember its previous stress-strain history. © 2005 Carl Hanser Verlag, München.
    view abstractdoi: 10.3139/ijmr-2005-0108
  • 2022 • 52 Creating a Ferromagnetic Ground State with Tc Above Room Temperature in a Paramagnetic Alloy through Non-Equilibrium Nanostructuring
    Ye, X. and Fortunato, N. and Sarkar, A. and Geßwein, H. and Wang, D. and Chen, X. and Eggert, B. and Wende, H. and Brand, R.A. and Zhang, H. and Hahn, H. and Kruk, R.
    Advanced Materials (2022)
    Materials with strong magnetostructural coupling have complex energy landscapes featuring multiple local ground states, thus making it possible to switch among distinct magnetic-electronic properties. However, these energy minima are rarely accessible by a mere application of an external stimuli to the system in equilibrium state. A ferromagnetic ground state, with Tc above room temperature, can be created in an initially paramagnetic alloy by nonequilibrium nanostructuring. By a dealloying process, bulk chemically disordered FeRh alloys are transformed into a nanoporous structure with the topology of a few nanometer-sized ligaments and nodes. Magnetometry and Mössbauer spectroscopy reveal the coexistence of two magnetic ground states, a conventional low-temperature spin-glass and a hitherto-unknown robust ferromagnetic phase. The emergence of the ferromagnetic phase is validated by density functional theory calculations showing that local tetragonal distortion induced by surface stress favors ferromagnetic ordering. The study provides a means for reaching conventionally inaccessible magnetic states, resulting in a complete on/off ferromagnetic–paramagnetic switching over a broad temperature range. © 2022 The Authors. Advanced Materials published by Wiley-VCH GmbH.
    view abstractdoi: 10.1002/adma.202108793
  • 2022 • 51 Origins of the hydrogen signal in atom probe tomography: Case studies of alkali and noble metals
    Yoo, S.-H. and Kim, S.-H. and Woods, E. and Gault, B. and Todorova, M. and Neugebauer, J.
    New Journal of Physics 24 (2022)
    Atom probe tomography (APT) analysis is being actively used to provide near-atomic-scale information on the composition of complex materials in three-dimensions. In recent years, there has been a surge of interest in the technique to investigate the distribution of hydrogen in metals. However, the presence of hydrogen in the analysis of almost all specimens from nearly all material systems has caused numerous debates as to its origins and impact on the quantitativeness of the measurement. It is often perceived that most H arises from residual gas ionization, therefore affecting primarily materials with a relatively low evaporation field. In this work, we perform systematic investigations to identify the origin of H residuals in APT experiments by combining density-functional theory (DFT) calculations and APT measurements on an alkali and a noble metal, namely Na and Pt, respectively. We report that no H residual is found in Na metal samples, but in Pt, which has a higher evaporation field, a relatively high signal of H is detected. These results contradict the hypothesis of the H signal being due to direct ionization of residual H2 without much interaction with the specimen's surface. Based on DFT, we demonstrate that alkali metals are thermodynamically less likely to be subject to H contamination under APT-operating conditions compared to transition or noble metals. These insights indicate that the detected H-signal is not only from ionization of residual gaseous H2 alone, but is strongly influenced by material-specific physical properties. The origin of H residuals is elucidated by considering different conditions encountered during APT experiments, specifically, specimen-preparation, transportation, and APT-operating conditions by taking thermodynamic and kinetic aspects into account. © 2022 The Author(s). Published by IOP Publishing Ltd on behalf of the Institute of Physics and Deutsche Physikalische Gesellschaft.
    view abstractdoi: 10.1088/1367-2630/ac40cd
  • 2022 • 50 The impact of the physical state and the reaction phase in the direct mechanocatalytic Suzuki-Miyaura coupling reaction
    Yoo, K. and Fabig, S. and Grätz, S. and Borchardt, L.
    Faraday Discussions (2022)
    doi: 10.1039/d2fd00100d
  • 2022 • 49 Dynamic intralaminar fracture toughness characterisation of unidirectional carbon fibre-reinforced polymer composites using a high-speed servo-hydraulic test set-up
    Yoo, S. and Dalli, D. and Catalanotti, G. and Toso, N. and Kessel, F. and Voggenreiter, H.
    Composite Structures 295 (2022)
    doi: 10.1016/j.compstruct.2022.115838
  • 2022 • 48 Passive flow control of vortex-induced vibrations of a low mass ratio circular cylinder oscillating in two degrees-of-freedom
    Youssef, M. and el Moctar, O. and el Sheshtawy, H. and Tödter, S. and Schellin, T.E.
    Ocean Engineering 254 (2022)
    doi: 10.1016/j.oceaneng.2022.111366
  • 2022 • 47 Pedestrian Counting Based on Piezoelectric Vibration Sensor
    Yu, Y. and Qin, X. and Hussain, S. and Hou, W. and Weis, T.
    Applied Sciences (Switzerland) 12 (2022)
    Pedestrian counting has attracted much interest of the academic and industry communities for its widespread application in many real-world scenarios. While many recent studies have focused on computer vision-based solutions for the problem, the deployment of cameras brings up concerns about privacy invasion. This paper proposes a novel indoor pedestrian counting approach, based on footstep-induced structural vibration signals with piezoelectric sensors. The approach is privacy-protecting because no audio or video data is acquired. Our approach analyzes the space-differential features from the vibration signals caused by pedestrian footsteps and outputs the number of pedestrians. The proposed approach supports multiple pedestrians walking together with signal mixture. Moreover, it makes no requirement about the number of groups of walking people in the detection area. The experimental results show that the averaged F1-score of our approach is over 0.98, which is better than the vibration signal-based state-of-the-art methods. © 2022 by the authors. Licensee MDPI, Basel, Switzerland.
    view abstractdoi: 10.3390/app12041920
  • 2022 • 46 Surface Boron Modulation on Cobalt Oxide Nanocrystals for Electrochemical Oxygen Evolution Reaction
    Yu, M. and Weidenthaler, C. and Wang, Y. and Budiyanto, E. and Onur Sahin, E. and Chen, M. and DeBeer, S. and Rüdiger, O. and Tüysüz, H.
    Angewandte Chemie - International Edition 61 (2022)
    Herein, we show that coupling boron with cobalt oxide tunes its structure and significantly boost its electrocatalytic performance for the oxygen evolution reaction (OER). Through a simple precipitation and thermal treatment process, a series of Co−B oxides with tunable morphologies and textural parameters were prepared. Detailed structural analysis supported first the formation of an disordered and partially amorphous material with nanosized Co3BO5 and/or Co2B2O6 being present on the local atomic scale. The boron modulation resulted in a superior OER reactivity by delivering a large current and an overpotential of 338 mV to reach a current density of 10 mA cm−2 in 1 M KOH electrolyte. Identical location transmission electron microscopy and in situ electrochemical Raman spectroscopy studies revealed alteration and surface re-construction of materials, and formation of CoO2 and (oxy)hydroxide intermediate, which were found to be highly dependent on crystallinity of the samples. © 2022 The Authors. Angewandte Chemie International Edition published by Wiley-VCH GmbH.
    view abstractdoi: 10.1002/anie.202211543
  • 2022 • 45 A Privacy-Protecting Step-Level Walking Direction Detection Algorithm based on Floor Vibration
    Yu, Y. and Carl, O. and Hussain, S. and Hou, W. and Weis, T.
    IEEE Sensors Journal 1-1 (2022)
    doi: 10.1109/JSEN.2022.3209909
  • 2022 • 44 Wax/PTFE Substrate Lens for Front-side Illumination of TeraFET Detectors
    Yuan, H. and Lisaukas, A. and Zhang, M. and Erni, D. and Roskos, H.G.
    International Conference on Infrared, Millimeter, and Terahertz Waves, IRMMW-THz 2022-August (2022)
    doi: 10.1109/IRMMW-THz50927.2022.9895696
  • 2022 • 43 Fourier Imaging Based on Sub-harmonic Detection at 600 GHz
    Yuan, H. and Lisauska, A. and Zhang, M. and Islam, Q.U. and Erni, D. and Roskos, H.G.
    2022 5th International Workshop on Mobile Terahertz Systems, IWMTS 2022 (2022)
    doi: 10.1109/IWMTS54901.2022.9832459
  • 2022 • 42 Quantifying Efficiency Limitations in All-Inorganic Halide Perovskite Solar Cells
    Yuan, Y. and Yan, G. and Hong, R. and Liang, Z. and Kirchartz, T.
    Advanced Materials 34 (2022)
    While halide perovskites have excellent optoelectronic properties, their poor stability is a major obstacle toward commercialization. There is a strong interest to move away from organic A-site cations such as methylammonium and formamidinium toward Cs with the aim of improving thermal stability of the perovskite layers. While the optoelectronic properties and the device performance of Cs-based all-inorganic lead-halide perovskites are very good, they are still trailing behind those of perovskites that use organic cations. Here, the state-of-the-art of all-inorganic perovskites for photovoltaic applications is reviewed by performing detailed meta-analyses of key performance parameters on the cell and material level. Key material properties such as carrier mobilities, external photoluminescence quantum efficiency, and photoluminescence lifetime are discussed and what is known about defect tolerance in all-inorganic is compared relative to hybrid (organic–inorganic) perovskites. Subsequently, a unified approach is adopted for analyzing performance losses in perovskite solar cells based on breaking down the losses into several figures of merit representing recombination losses, resistive losses, and optical losses. Based on this detailed loss analysis, guidelines are eventually developed for future performance improvement of all-inorganic perovskite solar cells. © 2022 The Authors. Advanced Materials published by Wiley-VCH GmbH.
    view abstractdoi: 10.1002/adma.202108132
  • 2022 • 41 Unveiling Ruthenium(II) Diazadienyls for Gas Phase Deposition Processes: Low Resistivity Ru Thin Films and Their Performance in the Acidic Oxygen Evolution Reaction
    Zanders, D. and Obenlüneschloß, J. and Wree, J.-L. and Jagosz, J. and Kaur, P. and Boysen, N. and Rogalla, D. and Kostka, A. and Bock, C. and Öhl, D. and Gock, M. and Schuhmann, W. and Devi, A.
    Advanced Materials Interfaces (2022)
    doi: 10.1002/admi.202201709
  • 2022 • 40 An Unusual Tri-coordinate Co(II) Silylamide with Potential for Chemical Vapor Deposition Processes
    Zanders, D. and Masuda, J.D. and Lowe, B. and Curtis, S. and Devi, A. and Barry, S.T.
    Zeitschrift fur Anorganische und Allgemeine Chemie (2022)
    doi: 10.1002/zaac.202200249
  • 2022 • 39 A Digital-Twin Based Architecture for Software Longevity in Smart Homes
    Zdankin, P. and Picone, M. and Mamei, M. and Weis, T.
    Proceedings - International Conference on Distributed Computing Systems 2022-July 669-679 (2022)
    Smart homes usually consist of smart objects (SOs) with limited resources and capabilities, and therefore constrain the complexity of applications that can be performed on them. In particular, updating smart objects within a smart home is a challenging undertaking, as seemingly insignificant updates affect the longevity of the deployment if they cause previously established dependencies to break. In this paper, we propose an architecture that we call Longevity Digital Twins (LDTs) as a strategic counterpart of SOs, aimed at running at the edge, as local to the smart home as possible. With this architecture, the capabilities of a SO can be virtually enhanced to support the software update process in the smart home. In this context, foresighted software management requires both a local capability to describe involved functionalities together with awareness about existing dependencies in this distributed system. Using a simulated smart home environment, we first measure the impact of conventional update strategies and then present the noticeable improvement that LDTs offer to this problem. Going further, we present the analysis of a real-world use case that showcases the potential of LDTs on how it could not only prevent the installation of breaking updates but also extend a SOs capabilities and its overall longevity. © 2022 IEEE.
    view abstractdoi: 10.1109/ICDCS54860.2022.00070
  • 2022 • 38 Tool type and macrostructure for magnetic abrasive finishing of flat surfaces on CNC machine tools
    Zelinko, A. and Welzel, F. and Biermann, D. and Maiboroda, V.
    Production Engineering (2022)
    Magnetic abrasive finishing (MAF) can be used on CNC machine tools as a final machining step to finish workpieces after the milling process. This paper presents a new tool system for the magnetic abrasive finishing of flat surfaces on traditional CNC machine tools using permanent magnets and a paramagnetic adapter without magnetizing the spindle. Five MAF-tool types with variated dimensions, quantity and arrangement of the permanent magnets were developed and tested for machining ferromagnetic materials at different feed rate and equivalent cutting speed. The magnetic flux density was measured for all MAF-tool types with a Hall sensor and the distribution is presented graphically. The benefits of a novel top cover structure for MAF-tools are presented and 20 types of structures were tested as well as divided into three groups. Optimal top cover structures lead to a significant increase in the process capability and a surface roughness reduction for MAF of flat surfaces of ferromagnetic workpieces. Furthermore, the significant influence of the top cover material on the process capability was discovered and a total of seven metal and plastic materials were tested, which were milled from solid material or additively manufactured. © 2022, The Author(s) under exclusive licence to German Academic Society for Production Engineering (WGP).
    view abstractdoi: 10.1007/s11740-021-01097-5
  • 2022 • 37 Elucidating ion transport mechanism in polyelectrolyte-complex membranes
    Zelner, M. and Stolov, M. and Tendler, T. and Jahn, P. and Ulbricht, M. and Freger, V.
    Journal of Membrane Science 658 (2022)
    Polyelectrolyte-complex (PEC) nanofiltration (NF) membranes attract much attention, however, the mechanisms governing ion separation in PEC films is not well understood. Here, we elucidate the ion transport in PECs using a recently reported Nafion-polyvinylamine (PVAm) membrane prepared via double-coating approach tuned to “rejection neutrality”, i.e., similar rejection of MgCl2 and Na2SO4 as single salts. New insights are gained by examining ion rejection for single- and mixed-salt solutions of NaCl, MgCl2 and Na2SO4 of varying concentrations and pH. The single salt permeability was found to vary with concentration, obeying a power law with an exponent around 0.4, matching neither the Donnan-dielectric nor a proposed PEC dissociation model. This is explained by progressive dissociation of the complex, which raises membrane swelling and dissociation constants, and weakenis dielectric exclusion, when salt concentration increases. Nevertheless, the membrane remains highly stable in all conditions, which is ascribed to the insolubility of Nafion in water. The results also indicate that “rejection-neutral” PEC still possesses a net negative charge, affecting ion selectivity at low salinities. The insights and physical picture proposed here may help understand and tune separation performance of PEC NF membranes and facilitate their implementation in applications such as purification and reuse of contaminated waters, resource recovery, and ion separations. © 2022 Elsevier B.V.
    view abstractdoi: 10.1016/j.memsci.2022.120757
  • 2022 • 36 Experimental and numerical investigation of shallow water effects on resistance and propulsion of coupled pusher-barge convoys
    Zentari, L. and el Moctar, O. and Lassen, J. and Hallmann, R. and Schellin, T.E.
    Applied Ocean Research 121 (2022)
    doi: 10.1016/j.apor.2022.103048
  • 2022 • 35 Gradually Fe-Doped Co3O4Nanoparticles in 2-Propanol and Water Oxidation Catalysis with Single Laser Pulse Resolution
    Zerebecki, S. and Schott, K. and Salamon, S. and Landers, J. and Wende, H. and Budiyanto, E. and Tüysüz, H. and Barcikowski, S. and Reichenberger, S.
    Journal of Physical Chemistry C 126 15144-15155 (2022)
    doi: 10.1021/acs.jpcc.2c01753
  • 2022 • 34 Engineering of Cation Occupancy of CoFe2O4 Oxidation Catalysts by Nanosecond, Single-Pulse Laser Excitation in Water
    Zerebecki, S. and Salamon, S. and Landers, J. and Yang, Y. and Tong, Y. and Budiyanto, E. and Waffel, D. and Dreyer, M. and Saddeler, S. and Kox, T. and Kenmoe, S. and Spohr, E. and Schulz, S. and Behrens, M. and Muhler, M. and T...
    ChemCatChem 14 (2022)
    doi: 10.1002/cctc.202101785
  • 2022 • 33 Quantum interference of identical photons from remote GaAs quantum dots
    Zhai, L. and Nguyen, G.N. and Spinnler, C. and Ritzmann, J. and Löbl, M.C. and Wieck, A.D. and Ludwig, Ar. and Javadi, A. and Warburton, R.J.
    Nature Nanotechnology 17 829-833 (2022)
    Photonic quantum technology provides a viable route to quantum communication1,2, quantum simulation3 and quantum information processing4. Recent progress has seen the realization of boson sampling using 20 single photons3 and quantum key distribution over hundreds of kilometres2. Scaling the complexity requires architectures containing multiple photon sources, photon counters and a large number of indistinguishable single photons. Semiconductor quantum dots are bright and fast sources of coherent single photons5–9. For applications, a roadblock is the poor quantum coherence on interfering single photons created by independent quantum dots10,11. Here we demonstrate two-photon interference with near-unity visibility (93.0 ± 0.8)% using photons from two completely separate GaAs quantum dots. The experiment retains all the emission into the zero phonon line—only the weak phonon sideband is rejected; temporal post-selection is not employed. By exploiting quantum interference, we demonstrate a photonic controlled-not circuit and an entanglement with fidelity of (85.0 ± 1.0)% between photons of different origins. The two-photon interference visibility is high enough that the entanglement fidelity is well above the classical threshold. The high mutual coherence of the photons stems from high-quality materials, diode structure and relatively large quantum dot size. Our results establish a platform—GaAs quantum dots—for creating coherent single photons in a scalable way. © 2022, The Author(s), under exclusive licence to Springer Nature Limited.
    view abstractdoi: 10.1038/s41565-022-01131-2
  • 2022 • 32 Dimethyl ether (DME) and dimethoxymethane (DMM) as reaction enhancers for methane: Combining flame experiments with model-assisted exploration of a polygeneration process
    Zhang, H. and Kaczmarek, D. and Rudolph, C. and Schmitt, S. and Gaiser, N. and Oßwald, P. and Bierkandt, T. and Kasper, T. and Atakan, B. and Kohse-Höinghaus, K.
    Combustion and Flame 237 (2022)
    The potential of dimethyl ether (DME) and dimethoxymethane (DMM), representatives of the attractive oxymethylene ether (OME) alternative fuel family, are explored here as reactivity enhancers for methane-fueled polygeneration processes. Typically, such processes that can flexibly generate power, heat, or chemicals, operate under fuel-rich conditions in gas turbines or internal combustion engines. To provide a consistent basis for the underlying reaction mechanisms, it is recognized that speciation data for the DME/CH4 fuel combination are available for such conditions while such information for the DMM/CH4 system is largely lacking. In addition, it should be noted that a detailed speciation study in flames, i.e., combustion systems involving chemistry and transport processes over a large temperature range, is still missing in spite of the potential of such systems to provide extended species information. In a systematic approach using speciation with electron ionization molecular-beam mass spectrometry (EI-MBMS), we thus report, as a first step, investigation of six fuel-rich premixed flames of DME and DMM and their blends with methane with special attention on interesting chemicals. Secondly, a comprehensive but compact DME/DMM/CH4 model (PolyMech2.1) is developed based on these data. This model is then examined against available experimental data under conditions from various facilities, focusing preferentially on elevated pressure and fuel-rich conditions. Comparison with existing literature models is also included in this evaluation. Thirdly, an analysis is given on this basis, via the extensively tested PolyMech2.1 model, for assumed polygeneration conditions in a homogeneous charge compression ignition (HCCI) engine environment. The main interest of this model-assisted exploration is to evaluate whether addition of DME or DMM in a polygeneration process can lead to potentially useful conditions for the production of syngas or other chemicals, along with work and heat. The flame results show that high syngas yields, i.e., up to ∼78% for CO and ∼35% for H2, can be obtained in their burnt gases. From the large number of intermediates detected, predominantly acetylene, ethylene, ethane, and formaldehyde show yields of 2.1−4.4% (C2 hydrocarbons) and 3.4−8.7% (CH2O), respectively. Also, methanol and methyl formate show comparably high yields of up to 0.6−6.7% in the flames with DMM, which is 1–2 orders of magnitude higher than in those with DME as the additive. In the modeling-assisted exploration of the engine process, the PolyMech2.1 model is seen to perform at significantly reduced computational costs compared to a recently validated model without sacrificing the prediction performance. Promising conditions for the assumed polygeneration process using fuel combinations in the DME/DMM/CH4 system are identified with attractive syngas yields of up to 77% together with work and heat output at exergetic efficiencies of up to 89% with DME. © 2021
    view abstractdoi: 10.1016/j.combustflame.2021.111863
  • 2022 • 31 In Situ Carbon Corrosion and Cu Leaching as a Strategy for Boosting Oxygen Evolution Reaction in Multimetal Electrocatalysts
    Zhang, J. and Quast, T. and He, W. and Dieckhöfer, S. and Junqueira, J.R.C. and Öhl, D. and Wilde, P. and Jambrec, D. and Chen, Y.-T. and Schuhmann, W.
    Advanced Materials (2022)
    The number of active sites and their intrinsic activity are key factors in designing high-performance catalysts for the oxygen evolution reaction (OER). The synthesis, properties, and in-depth characterization of a homogeneous CoNiFeCu catalyst are reported, demonstrating that multimetal synergistic effects improve the OER kinetics and the intrinsic activity. In situ carbon corrosion and Cu leaching during the OER lead to an enhanced electrochemically active surface area, providing favorable conditions for improved electronic interaction between the constituent metals. After activation, the catalyst exhibits excellent activity with a low overpotential of 291.5 ± 0.5 mV at 10 mA cm−2 and a Tafel slope of 43.9 mV dec−1. It shows superior stability compared to RuO2 in 1 m KOH, which is even preserved for 120 h at 500 mA cm−2 in 7 m KOH at 50 °C. Single particles of this CoNiFeCu after their placement on nanoelectrodes combined with identical location transmission electron microscopy before and after applying cyclic voltammetry are investigated. The improved catalytic performance is due to surface carbon corrosion and Cu leaching. The proposed catalyst design strategy combined with the unique single-nanoparticle technique contributes to the development and characterization of high-performance catalysts for electrochemical energy conversion. © 2022 The Authors. Advanced Materials published by Wiley-VCH GmbH
    view abstractdoi: 10.1002/adma.202109108
  • 2022 • 30 Graphene as a Transparent Conductive Electrode in GaN-Based LEDs
    Zhang, H. and Mischke, J. and Mertin, W. and Bacher, G.
    Materials 15 (2022)
    doi: 10.3390/ma15062203
  • 2022 • 29 Proposal for A Large Scale 1-D Subharmonic Coherent Detector Array in the 600 GHz Band
    Zhang, M. and Wang, P.-Y. and Yuan, H. and Roskos, H.G. and Rennings, A. and Erni, D.
    2022 5th International Workshop on Mobile Terahertz Systems, IWMTS 2022 (2022)
    doi: 10.1109/IWMTS54901.2022.9832440
  • 2022 • 28 Modeling of the Effect of Carrier Gas Injection on the Laminarity of the Plasma Jet Generated by a Cascaded Spray Gun
    Zhang, H. and Mauer, G. and Liu, S. and Liu, M. and Jia, Y. and Li, C. and Li, C. and Vaßen, R.
    Coatings 12 (2022)
    In this work, the plasma generated by the cascaded SinplexProTM plasma spray gun was studied by means of numerical simulation. Special attention is given to the laminarity of the plasma flow. The simulation part is divided into two parts: arcing simulation inside the spray gun and plasma jet simulation outside the spray gun. A laminar as well as a turbulent model is used in each case. The results show that, under the investigated conditions, the internal flow of the plasma torch can be considered as laminar with low turbulence and can, hence, be regarded as quasi-laminar flow. If carrier gas is injected into the plasma jet, the ideal laminar plasma jet is often greatly affected. However, the turbulent plasma jet with low turbulence intensity generated by the cascaded SinplexProTM plasma spray gun is less affected and can remain stable, which is beneficial to the plasma-spraying process. © 2022 by the authors.
    view abstractdoi: 10.3390/coatings12101416
  • 2022 • 27 Chemical Affinity of Ag-Exchanged Zeolites for Efficient Hydrogen Isotope Separation
    Zhang, L. and Wulf, T. and Baum, F. and Schmidt, W. and Heine, T. and Hirscher, M.
    Inorganic Chemistry 61 9413-9420 (2022)
    We report an ion-exchanged zeolite as an excellent candidate for large-scale application in hydrogen isotope separation. Ag(I)-exchanged zeolite Y has been synthesized through a standard ion-exchange procedure. The D2/H2 separation performance has been systematically investigated via thermal desorption spectroscopy (TDS). Undercoordinated Ag+ in zeolite AgY acts as a strong adsorption site and adorbs preferentially the heavier isotopologue even above liquid nitrogen temperature. The highest D2/H2 selectivity of 10 is found at an exposure temperature of 90 K. Furthermore, the high Al content of the zeolite structure leads to a high density of Ag sites, resulting in a high gas uptake. In the framework, approximately one-third of the total physisorbed hydrogen isotopes are adsorbed on the Ag sites, corresponding to 3 mmol/g. A density functional theory (DFT) calculation reveals that the isotopologue-selective adsorption of hydrogen at Ag sites contributes to the outstanding hydrogen isotope separation, which has been directly observed through cryogenic thermal desorption spectroscopy. The overall performance of zeolite AgY, showing good selectivity combined with high gas uptake, is very promising for future technical applications. © 2022 The Authors.
    view abstractdoi: 10.1021/acs.inorgchem.2c00028
  • 2022 • 26 Defect-characterized phase transition kinetics
    Zhang, X. and Zhang, J. and Wang, H. and Rogal, J. and Li, H.-Y. and Wei, S.-H. and Hickel, T.
    Applied Physics Reviews 9 (2022)
    doi: 10.1063/5.0117234
  • 2022 • 25 Hydrogen trapping and embrittlement in high-strength Al alloys
    Zhao, H. and Chakraborty, P. and Ponge, D. and Hickel, T. and Sun, B. and Wu, C.-H. and Gault, B. and Raabe, D.
    Nature 602 437-441 (2022)
    Ever more stringent regulations on greenhouse gas emissions from transportation motivate efforts to revisit materials used for vehicles1. High-strength aluminium alloys often used in aircrafts could help reduce the weight of automobiles, but are susceptible to environmental degradation2,3. Hydrogen ‘embrittlement’ is often indicated as the main culprit4; however, the exact mechanisms underpinning failure are not precisely known: atomic-scale analysis of H inside an alloy remains a challenge, and this prevents deploying alloy design strategies to enhance the durability of the materials. Here we performed near-atomic-scale analysis of H trapped in second-phase particles and at grain boundaries in a high-strength 7xxx Al alloy. We used these observations to guide atomistic ab initio calculations, which show that the co-segregation of alloying elements and H favours grain boundary decohesion, and the strong partitioning of H into the second-phase particles removes solute H from the matrix, hence preventing H embrittlement. Our insights further advance the mechanistic understanding of H-assisted embrittlement in Al alloys, emphasizing the role of H traps in minimizing cracking and guiding new alloy design. © 2022, The Author(s).
    view abstractdoi: 10.1038/s41586-021-04343-z
  • 2022 • 24 A 3-D printed Platform for a Photonic Terahertz Spectrometer to Measure a Photonic Crystal Waveguide
    Zhao, Y. and Kubiczek, T. and Liu, X. and Sakaki, M. and Benson, N. and Balzer, J.C.
    International Conference on Infrared, Millimeter, and Terahertz Waves, IRMMW-THz 2022-August (2022)
    doi: 10.1109/IRMMW-THz50927.2022.9896115
  • 2022 • 23 Thermal softening-suppressed inter-granular embrittlement of polycrystalline 3C-SiC under diamond cutting
    Zhao, L. and Zhang, J. and Fu, Y. and Zhang, J. and Hartmaier, A. and Sun, T.
    Materials and Design 223 (2022)
    doi: 10.1016/j.matdes.2022.111250
  • 2022 • 22 Formation of high density stacking faults in polycrystalline 3C-SiC by vibration-assisted diamond cutting
    Zhao, L. and Zhang, J. and Zhang, J. and Hartmaier, A. and Sun, T.
    Journal of the European Ceramic Society 42 5448-5457 (2022)
    doi: 10.1016/j.jeurceramsoc.2022.06.002
  • 2022 • 21 On the Mediated Electron Transfer of Immobilized Galactose Oxidase for Biotechnological Applications
    Zhao, F. and Brix, A.C. and Lielpetere, A. and Schuhmann, W. and Conzuelo, F.
    Chemistry - A European Journal 28 (2022)
    The use of enzymes as catalysts in chemical synthesis offers advantages in terms of clean and highly selective transformations. Galactose oxidase (GalOx) is a remarkable enzyme with several applications in industrial conversions as it catalyzes the oxidation of primary alcohols. We have investigated the wiring of GalOx with a redox polymer; this enables mediated electron transfer with the electrode surface for its potential application in biotechnological conversions. As a result of electrochemical regeneration of the catalytic center, the formation of harmful H2O2 is minimized during enzymatic catalysis. The introduced bioelectrode was applied to the conversion of bio-renewable platform materials, with glycerol as model substrate. The biocatalytic transformations of glycerol and 5-hydroxymethylfurfural (HMF) were investigated in a circular flow-through setup to assess the possibility of substrate over-oxidation, which is observed for glycerol oxidation but not during HMF conversion. © 2022 The Authors. Chemistry - A European Journal published by Wiley-VCH GmbH.
    view abstractdoi: 10.1002/chem.202200868
  • 2022 • 20 Oxidation behavior of double-ceramic-layer thermal barrier coatings deposited by atmospheric plasma spraying and suspension plasma spraying
    Zhao, Y. and Ge, Y. and Jin, X. and Koch, D. and Vaßen, R. and Chen, Y. and Fan, X.
    Ceramics International 48 23938-23945 (2022)
    This paper focuses on the oxidation behavior of novel double-ceramic-layer thermal barrier coatings (DCL TBCs) deposited by atmospheric plasma spraying (APS) and suspension plasma spraying (SPS). Four kinds of APS-SPS DCL TBCs with dense/porous columnar structured or vertically cracked microstructures were prepared. The oxidation behavior of the APS-SPS DCL TBCs were tested and the underlying mechanisms were further discussed. Results showed that the developed APS-SPS DCL TBCs have a better oxidation resistance than the single layer SPS TBC that was tested for comparison. In the long-term oxidation, the thermally grown oxide (TGO) can be divided into two layers, the outer mixed oxide and inner Al2O3 layer, in which the growth rate of mixed oxide in TGO changed during oxidation. In terms of the oxidation rate and oxidation lifetime, segmented APS-SPS TBCs has a slightly better performance than the columnar APS-SPS TBCs. Among the four different APS-SPS TBCs, the segmented dense APS-SPS TBCs with low vertical crack density appears to have more potential to be used for industrial application. © 2022
    view abstractdoi: 10.1016/j.ceramint.2022.05.068
  • 2022 • 19 Polarimetry for 3He Ion Beams from Laser–Plasma Interactions
    Zheng, C. and Fedorets, P. and Engels, R. and Kannis, C. and Engin, I. and Möller, S. and Swaczyna, R. and Feilbach, H. and Glückler, H. and Lennartz, M. and Pfeifer, H. and Pfennings, J. and Schneider, C.M. and Schnitzler, N. a...
    Instruments 6 (2022)
    doi: 10.3390/instruments6040061
  • 2022 • 18 Revealing in-plane grain boundary composition features through machine learning from atom probe tomography data
    Zhou, X. and Wei, Y. and Kühbach, M. and Zhao, H. and Vogel, F. and Darvishi Kamachali, R. and Thompson, G.B. and Raabe, D. and Gault, B.
    Acta Materialia 226 (2022)
    Grain boundaries (GBs) are planar lattice defects that govern the properties of many types of polycrystalline materials. Hence, their structures have been investigated in great detail. However, much less is known about their chemical features, owing to the experimental difficulties to probe these features at the atomic length scale inside bulk material specimens. Atom probe tomography (APT) is a tool capable of accomplishing this task, with an ability to quantify chemical characteristics at near-atomic scale. Using APT data sets, we present here a machine-learning-based approach for the automated quantification of chemical features of GBs. We trained a convolutional neural network (CNN) using twenty thousand synthesized images of grain interiors, GBs, or triple junctions. Such a trained CNN automatically detects the locations of GBs from APT data. Those GBs are then subjected to compositional mapping and analysis, including revealing their in-plane chemical decoration patterns. We applied this approach to experimentally obtained APT data sets pertaining to three case studies, namely, Ni-P, Pt-Au, and Al-Zn-Mg-Cu alloys. In the first case, we extracted GB specific segregation features as a function of misorientation and coincidence site lattice character. Secondly, we revealed interfacial excesses and in-plane chemical features that could not have been found by standard compositional analyses. Lastly, we tracked the temporal evolution of chemical decoration from early-stage solute GB segregation in the dilute limit to interfacial phase separation, characterized by the evolution of complex composition patterns. This machine-learning-based approach provides quantitative, unbiased, and automated access to GB chemical analyses, serving as an enabling tool for new discoveries related to interface thermodynamics, kinetics, and the associated chemistry-structure-property relations. © 2022 The Authors
    view abstractdoi: 10.1016/j.actamat.2022.117633
  • 2022 • 17 The role of momentum conservation on the tunneling between a two-dimensional electron gas and self-assembled quantum dots
    Zhou, D. and Kerski, J. and Beckel, A. and Geller, M. and Lorke, A. and Ludwig, A. and Wieck, A.D. and Chen, X. and Lu, W.
    Journal of Applied Physics 132 (2022)
    doi: 10.1063/5.0098561
  • 2022 • 16 Stacking faults in a mechanically strong Al(Mg)–Al3Mg2 composite
    Zhou, D. and Zhang, X. and Tehranchi, A. and Hou, J. and Lu, W. and Hickel, T. and Ponge, D. and Raabe, D. and Zhang, D.
    Composites Part B: Engineering 245 (2022)
    doi: 10.1016/j.compositesb.2022.110211
  • 2022 • 15 CeRES Process-Separation of Cerium from Lanthanum by Redox Extraction and Stripping
    Zhou, Y. and Schulz, S. and Haberstroh, J. and Wenzel, M. and Du, H. and Weigand, J.J.
    ACS Sustainable Chemistry and Engineering 10 16290-16298 (2022)
    doi: 10.1021/acssuschemeng.2c05048
  • 2022 • 14 Highly sensitive and stable MEMS acetone sensors based on well-designed α-Fe2O3/C mesoporous nanorods
    Zhu, L.-Y. and Yuan, K. and Li, Z.-C. and Miao, X.-Y. and Wang, J.-C. and Sun, S. and Devi, A. and Lu, H.-L.
    Journal of Colloid and Interface Science 622 156-168 (2022)
    doi: 10.1016/j.jcis.2022.04.081
  • 2022 • 13 Heterostructured α-Fe2O3@ZnO@ZIF-8 Core–Shell Nanowires for a Highly Selective MEMS-Based ppb-Level H2S Gas Sensor System
    Zhu, L.-Y. and Miao, X.-Y. and Ou, L.-X. and Mao, L.-W. and Yuan, K. and Sun, S. and Devi, A. and Lu, H.-L.
    Small (2022)
    doi: 10.1002/smll.202204828
  • 2022 • 12 Special Issue on Artificial Intelligence in Advanced Manufacturing Processes (AiAMP)
    Zhu, K. and Zhang, Y.J. and Gao, R. and Bambach, M. and Tekkaya, E.
    Journal of Materials Processing Technology 306 (2022)
    doi: 10.1016/j.jmatprotec.2022.117592
  • 2022 • 11 Ultrafast cold-brewing of coffee by picosecond-pulsed laser extraction
    Ziefuß, A.R. and Hupfeld, T. and Meckelmann, S.W. and Meyer, M. and Schmitz, O.J. and Kaziur-Cegla, W. and Tintrop, L.K. and Schmidt, T.C. and Gökce, B. and Barcikowski, S.
    npj Science of Food 6 (2022)
    doi: 10.1038/s41538-022-00134-6
  • 2022 • 10 Advances in pulsed laser synthesis of nanoparticles in liquids
    Ziefuss, A. and Barcikowski, S. and Zhigilei, L.V.
    Science China: Physics, Mechanics and Astronomy 65 (2022)
    doi: 10.1007/s11433-022-1909-6
  • 2022 • 9 Influence of Pt Alloying on the Fluorescence of Fully Inorganic, Colloidal Gold Nanoclusters
    Ziefuss, A.R. and Willeke, M. and Miertz, M. and Heinemann, A. and Rehbock, C. and Barcikowski, S.
    ChemPhysChem 23 (2022)
    doi: 10.1002/cphc.202200033
  • 2022 • 8 Processing of a Martensitic Tool Steel by Wire-Arc Additive Manufacturing
    Ziesing, U. and Lentz, J. and Röttger, A. and Theisen, W. and Weber, S.
    Materials 15 (2022)
    doi: 10.3390/ma15217408
  • 2022 • 7 Simulation of Powder Flow Behavior in an Artificial Feed Frame Using an Euler-Euler Model
    Zimmermann, M. and Raffel, C. and Bartsch, J. and Thommes, M.
    Chemical Engineering and Technology (2022)
    The Eulerian approach is an alternative numerical method to the traditionally used discreet particle techniques for modeling powder flow, avoiding limitations on particle number and diameter. The feasibility of an Euler-Euler simulation in a pharmaceutical application was investigated. In two- and three-dimensional flow simulations, computational fluid dynamics models and parameters were determined and verified based on comparison with experiments. Residence time distributions were calculated to show the applicability of the Eulerian model with two granular phases under the constraint of a continuous setup. Finally, this model was implemented to improve the process understanding of the powder flow in an artificial feed frame of a rotary tablet press. © 2022 The Authors. Chemical Engineering & Technology published by Wiley-VCH GmbH
    view abstractdoi: 10.1002/ceat.202100580
  • 2022 • 6 A novel approach of external lubrication in a rotary tablet press using electrostatics
    Zimmermann, M. and Michel, F. and Bartsch, J. and Thommes, M.
    Drug Development and Industrial Pharmacy 48 737-744 (2022)
    doi: 10.1080/03639045.2023.2165662
  • 2022 • 5 On the diversity of fossil and alternative gasoline combustion chemistry: A comparative flow reactor study
    Zinsmeister, J. and Gaiser, N. and Melder, J. and Bierkandt, T. and Hemberger, P. and Kasper, T. and Aigner, M. and Köhler, M. and Oßwald, P.
    Combustion and Flame 243 (2022)
    Recent progress in molecular combustion chemistry allows for detailed investigation of the intermediate species pool even for complex chemical fuel compositions, as occur for technical fuels. This study provides detailed investigation of a comprehensive set of complex alternative gasoline fuels obtained from laminar flow reactors equipped with molecular-beam sampling techniques for observation of the combustion intermediate species pool in homogeneous gas phase reactions. The combination of ionization techniques including double-imaging photoelectron photoion coincidence (i2PEPICO) spectroscopy enables deeper mechanistic insights into the underlying reaction network relevant to technical fuels. The selected fuels focus on contemporary automotive engine application as drop-in fuels compliant to European EN 228 specification for gasoline. Therefore, potential alternative gasoline blends containing oxygenated hydrocarbons as octane improvers obtainable from bio-technological production routes, e.g., ethanol, iso-butanol, methyl tert‑butyl ether (MTBE), and ethyl tert‑butyl ether (ETBE), as well as a Fischer-Tropsch surrogate were investigated. The fuel set is completed by two synthetic naphtha fractions obtained from Fischer-Tropsch and methanol-to-gasoline processes alongside with a fossil reference gasoline. In total, speciation data for 11 technical fuels from two atmospheric flow reactor setups are presented. Detailed main and intermediate species profiles are provided for slightly rich (ϕ = 1.2) and lean (ϕ = 0.8) conditions for intermediate to high temperatures. Complementary, the isomer distribution on different mass channels, like m/z = 78 u fulvene/benzene, of four gasolines was investigated. Experimental findings are analyzed in terms of the detailed fuel composition and literature findings for molecular combustion chemistry. Influences of oxygenated fuel components as well as composition of the hydrocarbon fractions are examined with a particular focus on the soot precursor chemistry. This dataset is available for validation of chemical kinetic mechanisms for realistic gasolines containing oxygenated hydrocarbons. © 2021
    view abstractdoi: 10.1016/j.combustflame.2021.111961
  • 2022 • 4 Upconversion photoluminescence excitation reveals exciton–trion and exciton–biexciton coupling in hBN/WS 2 /hBN van der Waals heterostructures
    Żuberek, E. and Majak, M. and Lubczyński, J. and Debus, J. and Watanabe, K. and Taniguchi, T. and Ho, C.-H. and Bryja, L. and Jadczak, J.
    Scientific Reports 12 (2022)
    doi: 10.1038/s41598-022-18104-z
  • 2022 • 3 A thermodynamic framework for unified continuum models for the healing of damaged soft biological tissue
    Zuo, D. and He, Y. and Avril, S. and Yang, H. and Hackl, K.
    Journal of the Mechanics and Physics of Solids 158 (2022)
    When they are damaged or injured, soft biological tissues are able to self-repair and heal. Mechanics is critical during the healing process, as the damaged extracellular matrix (ECM) tends to be replaced with a new undamaged ECM supporting homeostatic stresses. Computational modeling has been commonly used to simulate the healing process. However, there is a pressing need to have a unified thermodynamics theory for healing. From the viewpoint of continuum damage mechanics, some key parameters related to healing processes, for instance, the volume fraction of newly grown soft tissue and the growth deformation, can be regarded as internal variables and have related evolution equations. This paper is aiming to establish this unified framework inspired by thermodynamics for continuum damage models for healing of soft biological tissues, in which we introduce for the first time the coupled description of damage/healing and growth/remodeling based on thermodynamic considerations. Therefore, this new model is more concise and offers a universal approach to simulate the healing process. Three numerical examples are provided to demonstrate the effectiveness of the proposed model, which are in good agreement with the existing works, including an application for balloon angioplasty in an arteriosclerotic artery with a fiber cap. © 2021
    view abstractdoi: 10.1016/j.jmps.2021.104662
  • 2022 • 2 Enhancement of Proton Therapy Efficiency by Noble Metal Nanoparticles Is Driven by the Number and Chemical Activity of Surface Atoms
    Zwiehoff, S. and Johny, J. and Behrends, C. and Landmann, A. and Mentzel, F. and Bäumer, C. and Kröninger, K. and Rehbock, C. and Timmermann, B. and Barcikowski, S.
    Small 18 (2022)
    Proton-based radiotherapy is a modern technique for the treatment of solid tumors with significantly reduced side effects to adjacent tissues. Biocompatible nanoparticles (NPs) with high atomic numbers are known to serve as sensitizers and to enhance treatment efficacy, which is commonly believed to be attributed to the generation of reactive oxygen species (ROS). However, little systematic knowledge is available on how either physical effects due to secondary electron generation or the particle surface chemistry affect ROS production. Thereto, ligand-free colloidal platinum (Pt) and gold (Au) NPs with well-controlled particle size distributions and defined total surface area are proton-irradiated. A fluorescence-based assay is developed to monitor the formation of ROS using terephthalic acid as a cross-effect-free dye. The findings indicate that proton irradiation (PI)-induced ROS formation sensitized by noble metal NPs is driven by the total available particle surface area rather than particle size or mass. Furthermore, a distinctive material effect with Pt being more active than Au is observed which clearly indicates that the chemical reactivity of the NP surface is a main contributor to ROS generation upon PI. These results pave the way towards an in-depth understanding of the NP-induced sensitizing effects upon PI and hence a well-controlled enhanced therapy. © 2021 The Authors. Small published by Wiley-VCH GmbH
    view abstractdoi: 10.1002/smll.202106383
  • 2022 • 1 Effect of thermal and densification processes on reaction and conventional sinterings of a hydrolyzed calcium phosphate phase
    Zyman, Z. and Epple, M. and Goncharenko, A. and Tkachenko, M. and Rokhmistrov, D. and Sofronov, D.
    Ceramics International 48 6716-6721 (2022)
    Thermal processes resulting in the densification of compacts of an uncalcined powder (UPC) and of the powder calcined at 700 °C for 1 h (CPC), obtained from a hydrolyzed powder with a primary molar ratio of Ca/P = 1:1 obtained by the nitrate synthesis were studied during heating under reaction and conventional sintering modes up to 1100 °C. Due to desorption, decomposition, crystallization and phase transformation processes, the density of the UPC increased stepwise and finally reached 95% of the theoretical density of the formed biphasic HA/β-TCP product with a 52/48 ratio compared to 67% and a 0.55/0.45 ratio in the CPC. Because the annealing time at 1100 °C was negligible (about 1 min), a proper completing sintering to produce high quality ceramics from such UPC phases seems very promising. © 2021 Elsevier Ltd and Techna Group S.r.l.
    view abstractdoi: 10.1016/j.ceramint.2021.11.222