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, search for a specific author or term via the free text search, or use the interactive keyword cloud 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 • 1149 [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 • 1148 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 • 1147 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 • 1146 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 • 1145 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 • 1144 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 • 1143 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 • 1142 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 • 1141 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 • 1140 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 • 1139 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 • 1138 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 • 1137 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 • 1136 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 • 1135 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 • 1134 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 • 1133 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 • 1132 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 • 1131 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 • 1130 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 • 1129 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 • 1128 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 • 1127 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 • 1126 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 • 1125 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 • 1124 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 • 1123 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 • 1122 A federated infrastructure for European data spaces
    Otto, B.
    Communications of the ACM 65 44-45 (2022)
    doi: 10.1145/3512341
  • 2022 • 1121 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 • 1120 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 • 1119 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 • 1118 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 • 1117 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 • 1116 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 • 1115 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 • 1114 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 • 1113 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 • 1112 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 • 1111 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 • 1110 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 • 1109 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 • 1108 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 • 1107 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 • 1106 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 • 1105 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 • 1104 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 • 1103 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 • 1102 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 • 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, >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 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 • 1099 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 • 1098 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 • 1097 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 • 1096 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 • 1095 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 • 1094 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 • 1093 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 • 1092 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 • 1091 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 • 1090 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 • 1089 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 • 1088 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 • 1087 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 • 1086 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 • 1085 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 • 1084 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 • 1083 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 • 1082 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 • 1081 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 • 1080 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 • 1079 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 • 1078 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 • 1077 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 • 1076 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 • 1075 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 • 1074 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 • 1073 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 • 1072 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 • 1071 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 • 1070 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 • 1069 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 • 1068 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 • 1067 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 • 1066 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 • 1065 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 • 1064 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 • 1063 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 • 1062 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 • 1061 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 • 1060 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 • 1059 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 • 1058 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 • 1057 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 • 1056 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 • 1055 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 • 1054 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 • 1053 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 • 1052 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 • 1051 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 • 1050 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 • 1049 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 • 1048 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 • 1047 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 > 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 • 1046 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 • 1045 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 • 1044 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 • 1043 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 • 1042 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 • 1041 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 • 1040 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 • 1039 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 • 1038 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 • 1037 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 • 1036 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 • 1035 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 • 1034 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 • 1033 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 • 1032 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 < x < 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 • 1031 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 • 1030 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 • 1029 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 • 1028 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 • 1027 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 • 1026 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 • 1025 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 • 1024 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 • 1023 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 • 1022 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 • 1021 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 • 1020 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 • 1019 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 • 1018 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 • 1017 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 • 1016 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 • 1015 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 • 1014 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 • 1013 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 • 1012 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 • 1011 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 • 1010 Automatic welding robot offline programming with adaptive automation level
    Bickendorf, J.
    54th International Symposium on Robotics, ISR Europe 2022 34-41 (2022)
  • 2022 • 1009 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 • 1008 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 • 1007 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 • 1006 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 • 1005 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 • 1004 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 • 1003 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 • 1002 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 • 1001 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 • 1000 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 • 999 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 • 998 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 • 997 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 • 996 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 • 995 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 • 994 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 • 993 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 • 992 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 • 991 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 • 990 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 • 989 Blickpunkt Nachwuchs: Theoretische Elektrokatalyse
    Exner, K.S.
    Nachrichten aus der Chemie 70 82-84 (2022)
    doi: 10.1002/nadc.20224125416
  • 2022 • 988 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 • 987 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 • 986 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 • 985 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 • 984 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 • 983 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 • 982 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 • 981 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 • 980 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 • 979 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 • 978 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 • 977 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 • 976 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 • 975 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 • 974 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 • 973 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 • 972 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 • 971 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 • 970 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 • 969 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 • 968 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 • 967 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 • 966 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 • 965 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 • 964 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 • 963 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 • 962 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 • 961 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 • 960 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 • 959 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 • 958 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 • 957 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 • 956 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 • 955 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 • 954 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 • 953 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 • 952 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 • 951 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 • 950 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 • 949 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 • 948 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 • 947 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 • 946 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 • 945 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 • 944 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 • 943 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 • 942 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 • 941 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 • 940 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 • 939 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 • 938 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 • 937 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 • 936 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 • 935 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 • 934 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 • 933 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 • 932 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 • 931 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 • 930 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 • 929 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 • 928 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 • 927 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 • 926 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 • 925 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 • 924 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 • 923 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 • 922 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 • 921 Correction to: Editorial (Archive of Applied Mechanics, (2022), 92, 2, (431-432), 10.1007/s00419-021-02073-2)
    Ricken, T. and Ateshian, G.A.
    Archive of Applied Mechanics 92 433 (2022)
    doi: 10.1007/s00419-022-02131-3
  • 2022 • 920 Correction to: Strain path dependency in incremental sheet-bulk metal forming (International Journal of Material Forming, (2021), 14, 4, (547-561), 10.1007/s12289-020-01537-0)
    Wernicke, S. and Hahn, M. and Gerstein, G. and Nürnberger, F. and Tekkaya, A.E.
    International Journal of Material Forming 15 (2022)
    The article Strain path dependency in incremental sheetbulk metal forming, written by S. Wernicke, M. Hahn, G. Gerstein, F. Nürnberger, A. E. Tekkaya, was originally published Online First without Open Access. After publication in volume 14, issue 4, page 547–561 the author decided to opt for Open Choice and to make the article an Open Access publication. Therefore, the copyright of the article has been changed to ©The Author(s) 2022 and the article is forthwith distributed under the terms of the Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if changes were made. The images or other third party material in this article are included in the article’s Creative Commons licence, unless indicated otherwise in a credit line to the material. If material is not included in the article’s Creative Commons licence and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. Open Access funding enabled and organized by Projekt DEAL. ©The Author(s) 2022.
    view abstractdoi: 10.1007/s12289-022-01704-5
  • 2022 • 919 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 • 918 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 • 917 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 • 916 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 • 915 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 • 914 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 • 913 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 • 912 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 • 911 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 • 910 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 • 909 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 • 908 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 • 907 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 • 906 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 • 905 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 • 904 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 • 903 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 • 902 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 • 901 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 • 900 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 • 899 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 • 898 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 • 897 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 • 896 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 • 895 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 • 894 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 • 893 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 • 892 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 • 891 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 • 890 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 • 889 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 • 888 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 • 887 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 • 886 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 • 885 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 • 884 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 • 883 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 • 882 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 • 881 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 • 880 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 • 879 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 • 878 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 • 877 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 • 876 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 • 875 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 • 874 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 • 873 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 • 872 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 • 871 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 • 870 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 • 869 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 • 868 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 • 867 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 • 866 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 • 865 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 • 864 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 • 863 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 • 862 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 • 861 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 • 860 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 • 859 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 • 858 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 • 857 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 • 856 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 • 855 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 • 854 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 • 853 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 • 852 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 • 851 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 • 850 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 • 849 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 • 848 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 • 847 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 • 846 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 • 845 Editorial
    Ricken, T. and Ateshian, G.A.
    Archive of Applied Mechanics 92 431-432 (2022)
    doi: 10.1007/s00419-021-02073-2
  • 2022 • 844 Editorial for ADAC issue 4 of volume 16 (2022)
    Vichi, M. and Ceroli, A. and Kestler, H.A. and Okada, A. and Weihs, C.
    Advances in Data Analysis and Classification 16 817-821 (2022)
    doi: 10.1007/s11634-022-00525-3
  • 2022 • 843 Editorial: Computational Modeling for Liver Surgery and Interventions
    Christ, B. and Dahmen, U. and Radde, N. and Ricken, T.
    Frontiers in Physiology 13 (2022)
    doi: 10.3389/fphys.2022.859522
  • 2022 • 842 Editorial: Nematicity in iron-based superconductors
    Wang, Q. and Fanfarillo, L. and Böhmer, A.E.
    Frontiers in Physics 10 (2022)
    doi: 10.3389/fphy.2022.1038127
  • 2022 • 841 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 • 840 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 • 839 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 • 838 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 • 837 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 • 836 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 • 835 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 • 834 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 • 833 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 • 832 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 • 831 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
  • 2022 • 830 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 • 829 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 • 828 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 • 827 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 • 826 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 • 825 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 • 824 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 • 823 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 • 822 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 • 821 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 • 820 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 • 819 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 • 818 Efficient parametrization of the atomic cluster expansion
    Bochkarev, A. and Lysogorskiy, Y. and Menon, S. and Qamar, M. and Mrovec, M. and Drautz, R.
    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 • 817 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 • 816 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 • 815 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 • 814 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 • 813 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 • 812 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 • 811 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 • 810 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 • 809 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 • 808 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 • 807 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 • 806 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 • 805 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 • 804 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 • 803 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 • 802 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 • 801 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 • 800 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 • 799 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 • 798 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 • 797 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 • 796 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 • 795 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 • 794 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 • 793 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 • 792 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 • 791 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 • 790 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 • 789 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 • 788 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 • 787 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 • 786 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 • 785 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 • 784 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 • 783 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 • 782 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 • 781 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 • 780 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 • 779 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 • 778 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 • 777 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 • 776 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 • 775 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 • 774 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 • 773 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 • 772 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 • 771 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 • 770 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 • 769 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 • 768 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 • 767 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 • 766 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 • 765 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 • 764 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 • 763 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 • 762 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 • 761 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 • 760 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 • 759 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 • 758 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 • 757 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 • 756 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 • 755 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 • 754 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 • 753 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 • 752 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 • 751 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 • 750 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 • 749 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 • 748 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 • 747 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 • 746 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 • 745 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 • 744 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 • 743 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 • 742 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 • 741 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 • 740 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 • 739 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 • 738 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 • 737 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 • 736 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 • 735 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 • 734 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 • 733 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 • 732 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 • 731 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 • 730 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 • 729 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 • 728 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 • 727 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 • 726 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 • 725 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 • 724 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 • 723 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 • 722 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 • 721 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 • 720 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 • 719 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 • 718 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 • 717 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 • 716 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 • 715 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 • 714 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 • 713 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 • 712 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 • 711 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 • 710 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 • 709 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 • 708 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 • 707 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 • 706 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 • 705 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 • 704 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 • 703 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 • 702 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 • 701 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 • 700 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 • 699 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 • 698 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 • 697 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 • 696 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 • 695 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 • 694 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 • 693 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 • 692 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 • 691 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 • 690 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 • 689 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 • 688 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 • 687 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 • 686 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 • 685 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 • 684 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 • 683 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 • 682 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 • 681 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 • 680 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 • 679 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 • 678 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 • 677 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 • 676 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 • 675 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 • 674 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 • 673 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 • 672 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 • 671 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 • 670 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 • 669 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 • 668 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 • 667 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 • 666 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 • 665 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 • 664 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 • 663 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 • 662 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 • 661 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 • 660 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 • 659 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 • 658 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 • 657 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 • 656 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 • 655 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 • 654 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 • 653 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 • 652 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 • 651 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 • 650 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 • 649 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 • 648 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 • 647 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 • 646 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 • 645 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 • 644 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 • 643 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 • 642 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 • 641 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 • 640 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 • 639 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 • 638 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 • 637 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 • 636 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 • 635 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 • 634 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 • 633 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 • 632 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 • 631 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 • 630 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 • 629 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 • 628 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 • 627 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 • 626 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 • 625 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 • 624 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 • 623 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 • 622 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 • 621 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 • 620 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 • 619 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 • 618 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 • 617 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 &gt; 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 • 616 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 • 615 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 • 614 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 • 613 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 • 612 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 • 611 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 • 610 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 • 609 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 • 608 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 • 607 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 • 606 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 • 605 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 • 604 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 • 603 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 • 602 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 • 601 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 • 600 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 • 599 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 • 598 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 • 597 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 • 596 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 • 595 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 • 594 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 • 593 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 • 592 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 • 591 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 • 590 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 • 589 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 • 588 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 • 587 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 • 586 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 • 585 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 • 584 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 • 583 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 • 582 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 • 581 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 • 580 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 • 579 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 • 578 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 • 577 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 • 576 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 • 575 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 • 574 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 • 573 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 • 572 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 • 571 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 • 570 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 • 569 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 • 568 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 • 567 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 • 566 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 • 565 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 • 564 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 • 563 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 • 562 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 • 561 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 • 560 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 • 559 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 • 558 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 • 557 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 • 556 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 • 555 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 • 554 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 • 553 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 • 552 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 • 551 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 • 550 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 • 549 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 • 548 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 • 547 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 • 546 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 • 545 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 • 544 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 • 543 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 • 542 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 • 541 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 • 540 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 • 539 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 • 538 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 • 537 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 • 536 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 • 535 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 • 534 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 • 533 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 • 532 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 Kietzman