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arXiv 2019年

作者： Hashemi, Amirreza Guo, Ruiqiang Esfarjani, Keivan Lee, Sangyeop Computational Modeling and Simulation Program University of Pittsburgh PittsburghPA15261 United States Department of Mechanical Engineering and Materials Science University of Pittsburgh PittsburghPA15261 United States Department of Mechanical and Aerospace Engineering University of Virginia CharlottesvilleVA22904 United States Department of Materials Science and Engineering University of Virginia CharlottesvilleVA22904 United States Department of Physics University of Virginia CharlottesvilleVA22904 United States Department of Physics and Astronomy University of Pittsburgh PittsburghPA15261 United States

Establishing the structure-property relationship for grain boundaries (GBs) is critical for developing next generation functional materials, but has been severely hampered due to its extremely large configurational space. Atomistic simulations with low computational cost and high predictive power are strongly desirable, but the conventional simulations using empirical interatomic potentials and density functional theory suffer from the lack of predictive power and high computational cost, respectively. A machine learning interatomic potential (MLIP) recently emerged but often requires an extensive size of the training dataset, making it a less feasible approach. Here we demonstrate that an MLIP trained with a rationally designed small training dataset can predict thermal transport across GBs in graphene with ab initio accuracy at an affordable computational cost. In particular, we employed a rational approach based on the structural unit model to find a small set of GBs that can represent the entire configurational space and thus can serve as a cost-effective training dataset for the MLIP. Only 5 GBs were found to be enough to represent the entire configurational space of graphene GBs. Using the atomistic Green's function approach and the MLIP, we revealed that the structure-thermal resistance relation in graphene does not follow the common understanding that large dislocation density causes larger thermal resistance. In fact, thermal resistance is nearly independent of dislocation density at room temperature and is higher when the dislocation density is small at sub-room temperature. We explain this intriguing behavior with the buckling near a GB causing a strong scattering of flexural phonon modes. Our work shows that a machine learning technique combined with conventional wisdom (e.g., structural unit model) can extend the recent success of ab initio thermal transport simulation, which has been mostly limited to single crystals, to complex yet practically importa

关键词： Grain boundaries

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Correction: The structural, vibrational, and mechanical properties of jammed packings of deformable particles in three dimensions

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Soft matter 2022年第19期18卷 3815页

作者： Dong Wang John D Treado Arman Boromand Blake Norwick Michael P Murrell Mark D Shattuck Corey S O'Hern Department of Mechanical Engineering & Materials Science Yale University New Haven Connecticut 06520 USA. corey.ohern@yale.edu. Integrated Graduate Program in Physical and Engineering Biology Yale University New Haven Connecticut 06520 USA. Department of Physics Yale University New Haven Connecticut 06520 USA. Department of Biomedical Engineering Yale University New Haven Connecticut 06520 USA. Systems Biology Institute Yale University West Haven Connecticut 06516 USA. Benjamin Levich Institute and Physics Department The City College of New York New York New York 10031 USA. Department of Applied Physics Yale University New Haven Connecticut 06520 USA.

Correction for 'The structural, vibrational, and mechanical properties of jammed packings of deformable particles in three dimensions' by Dong Wang , , 2021, , 9901-9915, DOI: 10.1039/D1SM01228B.

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Colloquium: Phononic thermal properties of two-dimensional materials

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Reviews of Modern Physics 2018年第4期90卷 041002-041002页

作者： Xiaokun Gu Yujie Wei Xiaobo Yin Baowen Li Ronggui Yang Department of Mechanical Engineering University of Colorado Boulder Colorado 80309 USA and Materials Science and Engineering Program University of Colorado Boulder Colorado 80309 USA

Following the emergence of many novel two-dimensional (2D) materials beyond graphene, interest has grown in exploring implications for fundamental physics and practical applications ranging from electronics, photonics, and phononics to thermal management and energy storage. In this Colloquium, a summary and comparison are given of the phonon properties, such as phonon dispersion and relaxation time, of pristine 2D materials with single-layer graphene to understand the role of crystal structure and dimension on thermal conductivity. A comparison is made of the phonon properties, contrasting idealized 2D crystals, realistic 2D crystals, and 3D crystals, and synthesizing this to develop a physical picture of how the sample size of 2D materials affects their thermal conductivity. The effects of geometry such as the number of layers and the nanoribbon width, together with the presence of defects, mechanical strain, and substrate interactions on the thermal properties of 2D materials are discussed. Intercalation affects both the group velocities and phonon relaxation times of layered crystals and thus tunes the thermal conductivity along both the through-plane and basal-plane directions. This Colloquium concludes with a discussion of the challenges in theoretical and experimental studies of thermal transport in 2D materials. The rich and special phonon physics in 2D materials make them promising candidates for exploring novel phenomena such as topological phonon effects and applications such as phononic quantum devices.

关键词： Phonons Two-dimensional electron system Thermal & statistical models

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Image processing based on compound flat optics

arXiv

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arXiv 2019年

作者： Zhou, You Zheng, Hanyu Kravchenko, Ivan I. Valentine, Jason Interdisciplinary Materials Science Program Vanderbilt University NashvilleTN37212 United States Department of Electric Engineering and Computer Science Vanderbilt University NashvilleTN37212 United States Center for Nanophase Materials Sciences Oak Ridge National Laboratory Oak RidgeTN37831 United States Department of Mechanical Engineering Vanderbilt University NashvilleTN37212 United States

Image processing has become a critical technology in a variety of science and engineering disciplines. While most image processing is performed digitally, optical analog processing has the advantages of being low-power and high-speed though it requires a large volume. Here, we demonstrate optical analog imaging processing using a flat optic for direct image differentiation allowing one to significantly shrink the required optical system size. We first demonstrate how the image differentiator can be combined with traditional imaging systems such as a commercial optical microscope and camera sensor for edge detection. Second, we demonstrate how the entire analog processing system can be realized as a monolithic compound flat optic by integrating the differentiator with a metalens. The compound nanophotonic system manifests the advantage of thin form factor optics as well as the ability to implement complex transfer functions and could open new opportunities in applications such as biological imaging and machine vision. Copyright © 2019, The Authors. All rights reserved.

关键词： Edge detection

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Lessons learned from a collaborative NSF RET program involving three regional universities 125

Lessons learned from a collaborative NSF RET program involvi...

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125th ASEE Annual Conference and Exposition

作者： Mian, Ahsan Pinnell, Margaret Franco, M. Suzanne Petry, Leanne Doudican, Brett Srinivasan, Raghavan United States Faculty and Staff Development School of Engineering Department of Mechanical and Aerospace Engineering University of Dayton United States Education and Organizations Department College of Education and Human Services United States College of Science and Engineering Central State University United States University of Dayton NSF RET Program United States Mechanical and Materials Engineering Department Wright State University United States

A collaborative National science Foundation Research Experience for Teacher program involving three regional universities in the Midwest recently hosted its final cohort of teachers, preservice teachers and engineering students. This collaborative RET site placed the participant teams at one of the three regional universities to work on engineering research projects that connect with regional strengths in advanced manufacturing and materials. This paper will discuss the lessons learned from managing and facilitating a collaborative program. It will also discuss how this program was able to leverage regional assets to provide a deep and meaningful experiential learning opportunity for the participants. Finally, it will discuss how the participants were guided through a process to develop curriculum that connected their experiences and employed research based best practices for encouraging underrepresented populations to pursue engineering. © American Society for engineering Education, 2018.

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Lithium-Ion Batteries: Operando Magnetometry Probing the Charge Storage Mechanism of CoO Lithium-Ion Batteries (Adv. Mater. 12/2021)

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Advanced materials 2021年第12期33卷

作者： Hongsen Li Zhengqiang Hu Qingtao Xia Hao Zhang Zhaohui Li Huaizhi Wang Xiangkun Li Fengkai Zuo Fengling Zhang Xiaoxiong Wang Wanneng Ye Qinghao Li Yunze Long Qiang Li Shishen Yan Xiaosong Liu Xiaogang Zhang Guihua Yu Guo-Xing Miao College of Physics Center for Marine Observation and Communications Qingdao University Qingdao 266071 China School of Physics State Key Laboratory of Crystal Materials Shandong University Jinan 250100 China State Key Laboratory of Functional Materials for Informatics Shanghai Institute of Microsystem and Information Technology (SIMIT) Chinese Academy of Sciences Shanghai 200050 China College of Material Science and Engineering Nanjing University of Aeronautics and Astronautics Nanjing 210016 China Materials Science and Engineering Program and Department of Mechanical Engineering The University of Texas at Austin Austin TX 78712 USA Department of Electrical and Computer Engineering & Institute for Quantum Computing University of Waterloo Waterloo ON N2L 3G1 Canada

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Spatiotemporal Control of Morphogen Delivery to Pattern Stem Cell Differentiation in Three-Dimensional Hydrogels

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Current Protocols in Stem Cell Biology 2019年第1期51卷 e97页

作者： Balikov, Daniel A. Lippmann, Ethan S. Bellan, Leon M. Department of Mechanical Engineering Vanderbilt University Nashville TN United States Interdisciplinary Materials Science Program Vanderbilt University Nashville TN United States Department of Biomedical Engineering Vanderbilt University Nashville TN United States Department of Chemical and Biomolecular Engineering Vanderbilt University Nashville TN United States

Morphogens are biological molecules that alter cellular identity and behavior across both space and time. During embryonic development, morphogen spatial localization can be confined to small volumes in a single tissue or permeate throughout an entire organism, and the temporal effects of morphogens can range from fractions of a second to several days. In most cases, morphogens are presented as a gradient to adjacent cells within tissues to pattern cell fate. As such, to appropriately model development and build representative multicellular architectures in vitro, it is vital to recapitulate these gradients during stem cell differentiation. However, the ability to control morphogen presentation within in vitro systems remains challenging. Here, we describe an innovative platform using channels patterned within thick, three-dimensional hydrogels that deliver multiple morphogens to embedded cells, thereby demonstrating exquisite control over both spatial and temporal variations in morphogen presentation. This generalizable approach should have broad utility for researchers interested in patterning in vitro tissue structures. © 2019 by John Wiley & Sons, Inc. © 2019 John Wiley & Sons, Inc.

关键词： differentiation gradient hydrogel morphogen stem cell tissue engineering

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Accumulation-Driven Surfactant-Free Synthesis of Architectured Immiscible Metallic Nanoalloys with Enhanced Catalysis

SSRN

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SSRN 2019年

作者： Rajeeva, Bharath Bangalore Kunal, Pranaw Kollipara, Pavana Siddhartha Acharya, Palash V. Joe, Minwoong Ide, Matthew S. Jarvis, Karalee Liu, Yuanyue Bahadur, Vaibhav Humphrey, Simon M. Zheng, Yuebing Materials Science and Engineering Program Texas Materials Institute University of Texas at Austin AustinTX78712 United States Department of Chemistry University of Texas at Austin AustinTX78712 United States Walker Department of Mechanical Engineering University of Texas at Austin AustinTX78712 United States School of Mechanical Engineering Sungkyunkwan University Gyeonggi-do Suwon16419 Korea Republic of ExxonMobil Research and Engineering Company AnnandaleNJ08801 United States Texas Materials Institute University of Texas at Austin AustinTX78712 United States

Accumulation-mediated chemical reactions are a ubiquitous phenomenon in nature. Herein, we explore microbubble-induced accumulation of precursor ions to achieve surfactant-free synthesis of immiscible metallic nanoalloys and to simultaneously pattern the nanoalloys into targeted architectures for their enhanced catalytic applications. We name our approach as a unified spatiotemporal synthesis and structuring (US3) strategy, wherein millisecond-scale accumulation of the precursor ions in a highly confined laser-mediated microbubble trap (MBT) drives ultra-fast alloy synthesis in sync with the structuring process. As a case-in-point, we employ US3 strategy for the in-situ surfactant-free synthesis and patterning of traditionally immiscible rhodium-gold (RhAu) nanoalloys. Stochastic random walk simulations justify the millisecond-scale accumulation process, leading to a 3-order reduction in synthesis time. The catalytic activity and structure-property relationship of the structured nanoalloys were evaluated using the reduction of p-nitrophenol with NaBH4. Our in-situ synthesis and structuring strategy can be translated for high-throughput production and screening of multi-metallic systems with tailored catalytic, opto-electronic, and magnetic functions. © 2019, The Authors. All rights reserved.

关键词： Gold alloys

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Challenges with vitrification of Hanford High-Level Waste (HLW) to borosilicate glass – An overview

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Journal of Non-Crystalline Solids: X 2019年 4卷

作者： Goel, Ashutosh McCloy, John S. Pokorny, Richard Kruger, Albert A. Department of Materials Science and Engineering Rutgers The State University of New Jersey PiscatawayNJ United States School of Mechanical & Materials Engineering and Materials Science & Engineering Program Washington State University PullmanWA United States Laboratory of Inorganic Materials Joint Workplace of the University of Chemistry and Technology Prague Technická 5 166 28 Prague 6 Czechia The Institute of Rock Structure and Mechanics of the ASCR v.v.i V Holešovičkách 41 Prague 8182 09 Czech Republic U.S. Department of Energy Office of River Protection RichlandWA United States

The Hanford site in Washington State houses ~56 million gallons of radioactive wastes stored in 177 underground tanks. The waste must be immobilized and permanently stored, and the plan is to separate the tank wastes into low activity waste (LAW) and high-level waste (HLW) streams. The U.S. department of Energy is building a Waste Treatment and Immobilization Plant at Hanford site to separately vitrify these two waste streams in borosilicate glass using Joule-heated ceramic melters (JHCM). Although the process of nuclear waste vitrification seems to be well established, in practicality, it is faced with complex problems starting from the design of glass compositions, to processing in melters and long-term performance of the final vitrified waste forms. The article presents an overview of our current understanding of critical challenges related to the development and performance of HLW glasses. © 2019

关键词： Radioactive wastes

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A high-entropy silicide: (Mo0.2Nb0.2Ta0.2Ti0.2W0.2)Si2

arXiv

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arXiv 2019年

作者： Gild, Joshua Braun, Jeffrey Kaufmann, Kevin Marin, Eduardo Harrington, Tyler Hopkins, Patrick Vecchio, Kenneth Luo, Jian Program of Materials Science and Engineering University of California San Diego La JollaCA92093-0418 United States Department of NanoEngineering University of California San Diego La JollaCA92093-0448 United States Department of Mechanical and Aerospace Engineering University of Virginia CharlottesvilleVA22904 United States

A high-entropy metal disilicide, (Mo0.2Nb0.2Ta0.2Ti0.2W0.2)Si2, has been successfully synthesized. X-ray diffraction (XRD), energy dispersive X-ray spectroscopy (EDX), and electron backscatter diffraction (EBSD) collectively show the formation of a single high-entropy silicide phase. This high-entropy (Mo0.2Nb0.2Ta0.2Ti0.2W0.2)Si2 possesses a hexagonal C40 crystal structure with ABC stacking sequence and a point group of P6222. This discovery expands the known families of high-entropy materials from metals, oxides, borides, carbides, and nitrides to a silicide, for the first time to our knowledge, as well as demonstrating that a new, non-cubic, crystal structure (with lower symmetry) can be made into high-entropy. This (Mo0.2Nb0.2Ta0.2Ti0.2W0.2)Si2 exhibits high nanohardness of 16.7 ± 1.9 GPa and Vickers hardness of 11.6 ± 0.5 GPa. Moreover, it has a low thermal conductivity of 6.9 ± 1.1 W m-1 K-1, which is approximately one order of magnitude lower than that of the widely-used tetragonal MoSi2 and ~1/3 of those reported values for the hexagonal NbSi2 and TaSi2 with the same crystal structure. Copyright © 2019, The Authors. All rights reserved.

关键词： Entropy

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