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Copper-Rich Thermoelectric Sulfides: Size-Mismatch Effect and Chemical Disorder in the [TS4]Cu6 Complexes of Cu26T2Ge6S32 (T=Cr, Mo, W) Colusites

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Advanced materials 2019年第43期58卷 15601-15609页

作者： Kumar, Ventrapati Pavan Guélou, Gabin Lemoine, Pierric Raveau, Bernard Supka, Andrew R. Orabi, Rabih Al Rahal Al Fornari, Marco Suekuni, Koichiro Guilmeau, Emmanuel CRISMAT CNRS Normandie Univ ENSICAEN UNICAEN Caen14000 France Univ Rennes CNRS ISCR – UMR 6226 Rennes35000 France Department of Physics and Science of Advanced Materials Program Central Michigan University Mt. PleasantMI48859 United States Department of Applied Science for Electronics and Materials Interdisciplinary Graduate School of Engineering Sciences Kyushu University Kasuga Fukuoka816-8580 Japan Solvay Design and Development of Functional Materials Department Axel’One 87 avenue des Frères Perret Saint Fons Cedex69192 France

Herein, we investigate the Mo andWsubstitution for Cr in synthetic colusite, Cu26Cr2Ge6S32. Primarily, we elucidate the origin of extremely low electrical resistivity which does not compromise the Seebeck coefficient and leads to outstanding power factors of 1.94 mWm−1K−2 at 700 K in Cu26Cr2Ge6S32. We demonstrate that the abnormally long iono-covalent T–S bonds competing with short metallic Cu–T interactions govern the electronic transport properties of the conductive „Cu26S32" framework. We address the key role of the cationic size-mismatch at the core of the mixed tetrahedral–octahedral complex over the transport properties. Two essential effects are identified: 1) only the tetrahedra that are directly bonded to the [TS4]Cu6 complex are significantly distorted upon substitution and 2) the major contribution to the disorder is localized at the central position of the mixed tetrahedral–octahedral complex, and is maximized for x=1, i.e. for the highest cationic sizevariance, σ2. © 2020 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

关键词： Copper compounds

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Jammed packings of 3D superellipsoids with tunable packing fraction, contact number, and ordering

arXiv

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arXiv 2019年

作者： Yuan, Ye VanderWerf, Kyle Shattuck, Mark D. O’Hern, Corey S. Department of Mechanics and Engineering Science College of Engineering Peking University Beijing100871 China Department of Mechanical Engineering and Materials Science Yale University New HavenCT06520 United States Department of Physics Yale University New HavenCT06520 United States Benjamin Levich Institute and Physics Department City College of New York New YorkNY10031 United States Department of Applied Physics Yale University New HavenCT06520 United States Graduate Program in Computational Biology and Bioinformatics Yale University New HavenCT06520 United States

We carry out numerical studies of static packings of frictionless superellipsoidal particles in three spatial dimensions. We consider more than 200 different particle shapes by varying the three shape parameters that define superellipsoids. We characterize the structural and mechanical properties of both disordered and ordered packings using two packing-generation protocols. We perform athermal quasi-static compression simulations starting from either random, dilute configurations (Protocol 1) or thermalized, dense configurations (protocol 2), which allows us to tune the orientational order of the packings. In general, we find that the contact numbers at jamming onset for superellipsoid packings are hypostatic, with zJ f and df = 5 or 6 depending on whether the particles are axi-symmetric or not. Over the full range of orientational order, we find that the number of quartic modes of the dynamical matrix for the packings always matches the number of missing contacts relative to the isostatic value. This result suggests that there are no mechanically redundant contacts for ordered, yet hypostatic packings of superellipsoidal particles. Additionally, we find that the packing fraction at jamming onset for diordered packings of superellipsoidal particles can be collapsed using two particle shape parameters, e.g. the asphericity A and reduced aspect ratio β of the particles. Copyright © 2019, The Authors. All rights reserved.

关键词： Jamming

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Nanoscale deformation mechanics reveal resilience in nacre of Pinna nobilis shell

arXiv

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arXiv 2019年

作者： Gim, Jiseok Schnitzer, Noah Otter, Laura M. Cui, Yuchi Motreuil, Sébastien Marin, Frédéric Wolf, Stephan E. Jacob, Dorrit E. Misra, Amit Hovden, Robert Department of Materials Science & Engineering University of Michigan Ann ArborMI United States Department of Earth and Planetary Sciences Macquarie University SydneyNSW Australia Dijon France Erlangen Germany Erlangen Germany Applied Physics Program University of Michigan Ann ArborMI United States

The combination of soft nanoscale organic components with inorganic nanograins hierarchically designed by natural organisms results in highly ductile structural materials that can withstand mechanical impact and exhibit high resilience on the macro- and nano-scale. Our investigation of nacre deformation reveals the underlying nanomechanics that govern the structural resilience and absorption of mechanical energy. Using high-resolution scanning/ transmission electron microscopy (S/TEM) combined with in situ indentation, we observe nanoscale recovery of heavily deformed nacre that restores its mechanical strength on external stimuli up to 80% of its yield strength. Under compression, nacre undergoes deformation of nanograins and non-destructive locking across organic interfaces such that adjacent inorganic tablets structurally join. The locked tablets respond to strain as a continuous material, yet the organic boundaries between them still restrict crack propagation. Remarkably, the completely locked interface recovers its original morphology without any noticeable deformation after compressive contact stresses as large as 1.2 GPa. Copyright © 2019, The Authors. All rights reserved.

关键词： Deformation

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Micromechanical simulation on strength and ductility of two kinds of Al-based nanostructural materials

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Acta Mechanica Solida Sinica 2017年第4期30卷 404-415页

作者： Xu He Linli Zhu Jinling Liu Linan An State Key Laboratory of Traction Power Southwest Jiaotong University Applied Mechanics and Structure Safety Key Laboratory of Sichuan Province School of Mechanics and EngineeringSouthwest Jiaotong University Department of Engineering Mechanics and Key laboratory of Soft Machines and Smart Devices of Zhejiang Province Zhejiang University Department of Materials Science and Engineering and Advanced Materials Processing and Analysis Center University of Central Florida

The nanostructured Al-based composites possess the combination of high yield strength and good ductility. In this paper, a micromechanical model is presented to simulate the mechanical response of bimodal nanostructured A1 and the particle-reinforced aluminum matrix composite （PAMC）. The constitutive relations for different phases are addressed in the model, as well as the contribution of microcracks. Numerical results show that the model can successfully describe the enhanced strength and ductility of the bimodal nanostructured AI, and the predictions of the PAMC are in good agreement with the experimental data. It is worth noting that the strength and ductility are sensitive to the volume fraction of constituents and the distribution of rnicrocracks in both bimodal nanostructured A1 and PAMG. Therefore, the present theoretical results can be used to optimize the microstructure for improving the mechanical properties of nanostructured Al-based composites.

关键词： Nanocomposite Mechanism Microcrack Strength Ductility

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Macrophage Polarization: Remote Switching of Elastic Movement of Decorated Ligand Nanostructures Controls the Adhesion-Regulated Polarization of Host Macrophages (Adv. Funct. Mater. 21/2021)

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Advanced Functional materials 2021年第21期31卷

作者： Ramar Thangam Myeong Soo Kim Gunhyu Bae Yuri Kim Nayeon Kang Sungkyu Lee Hee Joon Jung Jinhyeok Jang Hyojun Choi Na Li Minjin Kim Sangwoo Park Seong Yeol Kim Thomas Myeongseok Koo Hong En Fu Yoo Sang Jeon Andreja Ambriović-Ristov Jae-Jun Song Soo Young Kim Steve Park Qiang Wei Changhyun Ko Ki-Bum Lee Ramasamy Paulmurugan Young Keun Kim Heemin Kang Department of Materials Science and Engineering Korea University Seoul 02841 Republic of Korea Institute for High Technology Materials and Devices Korea University Seoul 02841 Republic of Korea Department of Materials Science and Engineering Northwestern University Evanston IL 60208 USA International Institute for Nanotechnology Evanston IL 60208 USA NUANCE Center Northwestern University Evanston IL 60208 USA Department of Otorhinolaryngology-Head and Neck Surgery Korea University College of Medicine Seoul 08308 Republic of Korea Institute of Green Manufacturing Technology Korea University Seoul 02841 Republic of Korea Laboratory for Cell Biology and Signalling Division of Molecular Biology Ruđer Bošković Institute Zagreb 10000 Croatia Department of Materials Science and Engineering Korea Advanced Institute of Science and Technology (KAIST) Daejeon 34141 Republic of Korea College of Polymer Science and Engineering State Key Laboratory of Polymer Materials and Engineering Sichuan University Chengdu 610065 China Department of Applied Physics College of Engineering Sookmyung Women's University Seoul 04310 Republic of Korea Department of Chemistry and Chemical Biology Rutgers University Piscataway NJ 08854 USA Department of Radiology Molecular Imaging Program at Stanford Stanford University School of Medicine Stanford University Palo Alto CA 94304 USA Department of Radiology Canary Center at Stanford for Cancer Early Detection Stanford University School of Medicine Stanford University Palo Alto CA 94304 USA Department of Biomicrosystem Technology Korea University Seoul 02841 Republic of Korea

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Stacking, Strain, &Stiffness of 2D Transition Metal Dichalcogenides Quantified through Reciprocal Space

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Microscopy and Microanalysis 2018年第S1期24卷 1586-1587页

作者： Noah Schnitzer Suk Hyun Sung Robert Hovden Department of Materials Science and Engineering University of Michigan Ann Arbor MI Applied Physics Program University of Michigan Ann Arbor MI

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Multi-Objective Genetic Algorithm Based Optimization of Age Hardening for AA6063 Alloy

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IOP Conference Series: materials science and engineering 2020年第5期912卷

作者： Aluru Praveen Sekhar Supriya Nandy Swati Dey Subhabrata Datta Debdulal Das Department of Metallurgy and Materials Engineering Indian Institute of Engineering Science and Technology Howrah 711103 India Department of Microstructural Physics and Alloy Design Max-Planck-Institut für Eisenforschung GmbH Max-Planck-Straβe Düsseldorf 40237 Germany Department of Aerospace and Applied Mechanics Indian Institute of Engineering Science and Technology Shibpur Howrah 711103 India Department of Mechanical Engineering SRM Institute of Science and Technology Kattankulathur 603203 Tamilnadu India

The present article attempts to optimize the process parameters of artificial ageing for an AA6063 Al-Mg-Si alloy using multi-objective genetic algorithm (MOGA) to simultaneously achieve the maximum ultimate tensile strength (UTS) and percentage of elongation (%El). For this, a feed-forward multi-layered perceptron artificial neural network (ANN) has been developed which is trained by the scale conjugate gradient back propagation algorithm. The dataset required for the model has been compiled from the experimental results of this study, as well as, from the open literature. The network consists of solutionizing time and temperature, storage time/pre-ageing, rate of quenching, ageing time and temperature as input variables and UTS, %El as their outputs. The developed ANN model establishes the interrelationships between the input and output variables which can serve as objective functions for the optimization, following the theory of Pareto-optimality. The Pareto solution generated from MOGA between UTS and %El assists to conclude that the desired combination of high strength and ductility has been achieved through slow cooling after solutionizing, high pre-ageing time and high temperature of ageing. Furthermore, the designed heat treatment schedule through MOGA has been applied to the selected alloy on an experimental basis which shows satisfactory results.

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Fermi level pinning by defects can explain the large reported carbon 1s binding energy variations in diamond

arXiv

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arXiv 2019年

作者： Walter, Michael Mangolini, Filippo McClimon, J. Brandon Carpick, Robert W. Moseler, Michael Fraunhofer IWM MikroTribologie Centrum μTC Wöhlerstrasse 11 FreiburgD-79108 Germany FIT Freiburg Centre for Interactive Materials and Bioinspired Technologies University of Freiburg Georges-Köhler-Allee 105 Freiburg79110 Germany Institute of Physics University of Freiburg Herrmann-Herder-Straße 3 FreiburgD-79104 Germany Materials Science and Engineering Program Department of Mechanical Engineering University of Texas at Austin AustinTX78712 United States Department of Materials Science and Engineering University of Pennsylvania Philadelphia19104 United States Department of Mechanical Engineering and Applied Mechanics University of Pennsylvania PhiladelphiaPA19104 United States Freiburger Materialforschungszentrum Universität Freiburg Stefan-Meier-Straße 21 FreiburgD-79104 Germany

The quantitative evaluation of the carbon hybridization state by X-ray photoelectron spectroscopy (XPS) has been a surface-analysis problem for the last three decades due to the challenges associated with the unambiguous identification of the characteristic binding energy values for sp2and sp3- bonded carbon. While the sp2binding energy is well established, there is disagreement for the sp3value in the literature. Here, we compute the binding energy values for model structures of pure and doped-diamond using density functional theory. The simulation results indicate that the large bandgap of diamond allows defects to pin the Fermi level, which results in large variations of the C(1s) core electron energies for sp3-bonded carbon, in agreement with the broad range of experimental C(1s) binding energy values for sp3. carbon reported in the literature. Fermi level pinning by boron is demonstrated by experimental C(1s) binding energies of highly B-doped ultrananocrystalline diamond that are in good agreement to simulations. Copyright © 2019, The Authors. All rights reserved.

关键词： Binding energy

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Domain morphology and mechanics of the H/T′ transition metal dichalcogenide monolayers

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Physical Review materials 2018年第11期2卷 114002-114002页

作者： Joel Berry Songsong Zhou Jian Han David J. Srolovitz Mikko P. Haataja Department of Materials Science and Engineering University of Pennsylvania Philadelphia Pennsylvania 19104 USA Department of Mechanical and Aerospace Engineering Princeton University Princeton New Jersey 08544 USA Department of Mechanical Engineering and Applied Mechanics University of Pennsylvania Philadelphia Pennsylvania 19104 USA Department of Materials Science and Engineering City University of Hong Kong Hong Kong SAR People's Republic of China Princeton Institute for the Science and Technology of Materials (PRISM) Princeton University Princeton New Jersey 08544 USA Program in Applied and Computational Mathematics (PACM) Princeton University Princeton New Jersey 08544 USA

The properties of two-dimensional (2D) transition metal dichalcogenide (TMD) monolayers can be dynamically controlled via strain-induced displacive structural transformations between semiconducting (H) and metallic or semimetallic (T′) crystal structures. The shapes, symmetries, and kinetics of crystalline domains generated during these transformations and the mechanical response of transforming monolayers are of fundamental and applied interest in, e.g., phase change memory devices and the study of topologically protected edge states in quantum spin Hall insulating T′ crystals. We quantitatively characterize T′ domain morphologies during H→T′ transformations in both flat and bendable TMD monolayers using a combination of first principles and continuum calculations. Wulff constructions for MoTe2 and MoS2 show that T′ domains within much larger T′ domains are either rhombi of fixed proportions (if nonmisfitting) or rectangles whose aspect ratio AR increases with domain size L0 (if misfitting). Isolated T′ domains within much larger H domains undergo a morphological crossover from compact to elongated shapes at L0≈100–200 nm if the sheet is constrained to be flat or L0≳2μm if the sheet is free to bend. This crossover is driven by a competition between anisotropic interfacial energy and elastic misfit energy, and its position can be tuned via the monolayer-substrate interaction strength. It is shown that the aspect ratio AR obeys a scaling law AR∼L02/3. Stress-strain response characterized as a function of strain orientation reveals extreme anisotropy in the effective elastic modulus through H/T′ coexistence. Ferroelastic multidomain T′−WTe2 monolayers are found to exhibit two to three regimes of reversible mechanical response, and localized buckling in freely suspended T′ monolayers is shown to qualitatively alter T′ domain symmetries.

关键词： Bending Domain walls Mechanical deformation Microstructure Structural phase transition 2-dimensional systems Transition metal dichalcogenides Density functional theory Phase-field modeling

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Void distributions reveal structural link between jammed packings and protein cores

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Physical Review E 2019年第2期99卷 022416-022416页

作者： John D. Treado Zhe Mei Lynne Regan Corey S. O'Hern Department of Mechanical Engineering & Materials Science Yale University New Haven Connecticut 06520 USA Integrated Graduate Program in Physical & Engineering Biology Yale University New Haven Connecticut 06520 USA Department of Chemistry Yale University New Haven Connecticut 06520 USA Department of Molecular Biophysics & Biochemistry Yale University New Haven Connecticut 06520 USA Department of Physics Yale University New Haven Connecticut 06520 USA Department of Applied Physics Yale University New Haven Connecticut 06520 USA Program in Computational Biology and Bioinformatics Yale University New Haven Connecticut 06520 USA

Dense packing of hydrophobic residues in the cores of globular proteins determines their stability. Recently, we have shown that protein cores possess packing fraction ϕ≈0.56, which is the same as dense, random packing of amino-acid-shaped particles. In this article, we compare the structural properties of protein cores and jammed packings of amino-acid-shaped particles in much greater depth by measuring their local and connected void regions. We find that the distributions of surface Voronoi cell volumes and local porosities obey similar statistics in both systems. We also measure the probability that accessible, connected void regions percolate as a function of the size of a spherical probe particle and show that both systems possess the same critical probe size. We measure the critical exponent τ that characterizes the size distribution of connected void clusters at the onset of percolation. We find that the cluster size statistics are similar for void percolation in packings of amino-acid-shaped particles and randomly placed spheres, but different from that for void percolation in jammed sphere packings. We propose that the connected void regions are a defining structural feature of proteins and can be used to differentiate experimentally observed proteins from decoy structures that are generated using computational protein design software. This work emphasizes that jammed packings of amino-acid-shaped particles can serve as structural and mechanical analogs of protein cores, and could therefore be useful in modeling the response of protein cores to cavity-expanding and -reducing mutations.

关键词： Jamming Protein structure Packing & jamming problems Proteins Crystal structures Finite-size scaling Molecular dynamics Percolation theory

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