检索结果-内蒙古大学图书馆

arXiv 2019年

作者： Gupta, Tushar Ghosha, Debjit Yoshimura, Anthony Basu, Swastik Chow, Philippe K. Lakhnot, Aniruddha S. Pandey, Juhi Warrender, Jeffrey M. Efstathiadis, Harry Soni, Ajay Osei-Agyemang, Eric Balasubramanian, Ganesh Zhang, Shengbai Shi, Su-Fei Lu, Toh-Ming Meunier, Vincent Koratkar, Nikhil Department of Mechanical Rensselaer Polytechnic Institute Aerospace and Nuclear Engineering TroyNY12180 United States Department of Chemical and Biological Engineering Rensselaer Polytechnic Institute TroyNY12180 United States Department of Physics Rensselaer Polytechnic Institute Applied Physics and Astronomy TroyNY12180 United States U.S. Army Combat Capabilities Development Command-Armament Center-Benet Laboratories WatervlietNY12189 United States Indian Institute of Technology Mandi School of Basic Sciences Mandi175005 HP India State University of New York Polytechnic Institute Colleges of Nanoscale Science and Engineering AlbanyNY12203 United States Department of Mechanical Engineering and Mechanics Lehigh University BethlehemPA18015 United States Department of Materials Science and Engineering Rensselaer Polytechnic Institute TroyNY12180 United States

Organic-inorganic halide perovskites are intrinsically unstable when exposed to moisture and/or light. Additionally, the presence of lead in many perovskites raises toxicity concerns. Herein is reported a thin film of BaZrS3, a lead-free chalcogenide perovskite. Photoluminescence and X-ray diffraction measurements show that BaZrS3 is far more stable than methylammonium lead iodide (MAPbI3) in moist environments. Moisture-A nd light-induced degradations in BaZrS3 and MAPbI3 are compared by using simulations and calculations based on density functional theory. The simulations reveal drastically slower degradation in BaZrS3 due to two factors-weak interaction with water, and very low rates of ion migration. BaZrS3 photo-detecting devices with photo-responsivity of 46.5 mA W-1 are also reported. The devices retain 60% of their initial photo-response after 4 weeks in ambient conditions. Similar MAPbI3 devices degrade rapidly and show 95% decrease in photo-responsivity in just 4 days. The findings establish the superior stability of BaZrS3 and strengthen the case for its use in optoelectronics. New possibilities for thermoelectric energy conversion using these materials are also demonstrated. Copyright © 2019, The Authors. All rights reserved.

关键词： Moisture

来源：评论

学校读者我要写书评

暂无评论

Polycrystalline ZrTe5 Parametrized as a Narrow-Band-Gap Semiconductor for Thermoelectric Performance

引用

Physical Review applied 2018年第1期9卷 014025-014025页

作者： Samuel A. Miller Ian Witting Umut Aydemir Lintao Peng Alexander J. E. Rettie Prashun Gorai Duck Young Chung Mercouri G. Kanatzidis Matthew Grayson Vladan Stevanović Eric S. Toberer G. Jeffrey Snyder Department of Materials Science and Engineering Northwestern University Evanston Illinois 60208 USA Department of Chemistry Koç University Sariyer Istanbul 34450 Turkey Applied Physics Graduate Program Northwestern University Evanston Illinois 60208 USA Materials Science Division Argonne National Laboratory Argonne Illinois 60439 USA National Renewable Energy Laboratory Golden Colorado 80401 USA Department of Metallurgical and Materials Engineering Colorado School of Mines Golden Colorado 80401 USA Department of Chemistry Northwestern University Evanston Illinois 60208 USA Department of Electrical Engineering and Computer Science Northwestern University Evanston Illinois 60208 USA Department of Physics Colorado School of Mines Golden Colorado 80401 USA

The transition-metal pentatellurides HfTe5 and ZrTe5 have been studied for their exotic transport properties with much debate over the transport mechanism, band gap, and cause of the resistivity behavior, including a large low-temperature resistivity peak. Single crystals grown by the chemical-vapor-transport method have shown an n−p transition of the Seebeck coefficient at the same temperature as a peak in the resistivity. We show that behavior similar to that of single crystals can be observed in iodine-doped polycrystalline samples but that undoped polycrystalline samples exhibit drastically different properties: they are p type over the entire temperature range. Additionally, the thermal conductivity for polycrystalline samples is much lower, 1.5 Wm−1 K−1, than previously reported for single crystals. It is found that the polycrystalline ZrTe5 system can be modeled as a simple semiconductor with conduction and valence bands both contributing to transport, separated by a band gap of 20 meV. This model demonstrates to first order that a simple two-band model can explain the transition from n- to p-type behavior and the cause of the anomalous resistivity peak. Combined with the experimental data, the two-band model shows that carrier concentration variation is responsible for differences in behavior between samples. Using the two-band model, the thermoelectric performance at different doping levels is predicted, finding zT=0.2 and 0.1 for p and n type, respectively, at 300 K, and zT=0.23 and 0.32 for p and n type at 600 K. Given the reasonably high zT that is comparable in magnitude for both n and p type, a thermoelectric device with a single compound used for both legs is feasible.

关键词： Band gap Charge density waves Hall effect Semimetals Spin-orbit coupling Thermoelectric effects Chalcogenides Semiconductor compounds

来源：评论

学校读者我要写书评

暂无评论

Valley-selective optical Stark effect probed by Kerr rotation

引用

Physical Review B 2018年第4期97卷 045307-045307页

作者： Trevor LaMountain Hadallia Bergeron Itamar Balla Teodor K. Stanev Mark C. Hersam Nathaniel P. Stern Applied Physics Program Northwestern University Evanston Illinois 60208 USA Department of Materials Science and Engineering Northwestern University Evanston Illinois 60208 USA Department of Physics and Astronomy Northwestern University Evanston Illinois 60208 USA Department of Chemistry Northwestern University Evanston Illinois 60208 USA Department of Electrical Engineering and Computer Science Northwestern University Evanston Illinois 60208 USA

The ability to monitor and control distinct states is at the heart of emerging quantum technologies. The valley pseudospin in transition metal dichalcogenide (TMDC) monolayers is a promising degree of freedom for such control, with the optical Stark effect allowing for valley-selective manipulation of energy levels in WS2 and WSe2 using ultrafast optical pulses. Despite these advances, understanding of valley-sensitive optical Stark shifts in TMDCs has been limited by reflectance-based detection methods where the signal is small and prone to background effects. More sensitive polarization-based spectroscopy is required to better probe ultrafast Stark shifts for all-optical manipulation of valley energy levels. Here, we show time-resolved Kerr rotation to be a more sensitive probe of the valley-selective optical Stark effect in monolayer TMDCs. Compared to the established time-resolved reflectance methods, Kerr rotation is less sensitive to background effects. Kerr rotation provides a fivefold improvement in the signal-to-noise ratio of the Stark effect optical signal and a more precise estimate of the energy shift. This increased sensitivity allows for observation of an optical Stark shift in monolayer MoS2 that exhibits both valley and energy selectivity, demonstrating the promise of this method for investigating this effect in other layered materials and heterostructures.

关键词： Dielectric properties Excitons Semiconductors Transition metal dichalcogenides Kerr effect Reflectivity

来源：评论

学校读者我要写书评

暂无评论

Anomalous Diffusion along Metal/Ceramic Interfaces

arXiv

引用

arXiv 2018年

作者： Kumar, Aakash Barda, Hagit Klinger, Leonid Finnis, Michael W. Lordi, Vincenzo Rabkin, Eugen Srolovitz, David J. Department of Materials Science and Engineering University of Pennsylvania PhiladelphiaPA19104 United States Department of Materials Science and Engineering Technion-Israel Institute of Technology Haifa3200003 Israel Department of Materials and Department of Physics Imperial College LondonSW7 2AZ United Kingdom Thomas Young Center LondonSW7 2AZ Materials Science Division Lawrence Livermore National Laboratory LivermoreCA94550 United States Department of Mechanical Engineering and Applied Mechanics University of Pennsylvania PhiladelphiaPA19104 United States

Hole formation in a polycrystalline Ni film on an-Al2O3 substrate coupled with a continuum diffusion analysis demonstrates that Ni diffusion along the Ni/-Al2O3 interface is surprisingly fast. Ab initio calculations demonstrate that both Ni vacancy formation and migration energies at the coherent Ni/-Al2O3 interface are much smaller than in bulk Ni, suggesting that the activation energy for diffusion along coherent Ni/-Al2O3 interfaces is comparable to that along (incoherent/high angle) grain boundaries. Based on these results, we develop a simple model for diffusion along metal/ceramic interfaces, apply it to a wide range of metal/ceramic systems and validate it with several ab initio calculations. These results suggest that fast metal diffusion along metal/ceramic interfaces should be common, but is not universal. Copyright © 2018, The Authors. All rights reserved.

关键词： Diffusion

来源：评论

学校读者我要写书评

暂无评论

Microstructural materials Design via Deep Adversarial Learning Methodology

arXiv

引用

arXiv 2018年

作者： Yang, Zijiang Li, Xiaolin Brinson, L. Catherine Choudhary, Alok N. Chenc, Wei Agrawal, Ankit Department of Electrical Engineering and Computer Science Northwestern University EvanstonIL60208 United States Theoretical and Applied Mechanics Northwestern University EvanstonIL60208 United States Department of Mechanical Engineering Northwestern University EvanstonIL60208 United States Department of Mechanical Engineering and Materials Science Duke University DurhamNC27708 United States

Identifying the key microstructure representations is crucial for Computational materials Design (CMD). However, existing microstructure characterization and reconstruction (MCR) techniques have limitations to be applied for microstructural materials design. Some MCR approaches are not applicable for microstructural materials design because no parameters are available to serve as design variables, while others introduce significant information loss in either microstructure representation and/or dimensionality reduction. In this work, we present a deep adversarial learning methodology that overcomes the limitations of existing MCR techniques. In the proposed methodology, generative adversarial networks (GAN) are trained to learn the mapping between latent variables and microstructures1. Thereafter, the low-dimensional latent variables serve as design variables, and a Bayesian optimization framework is applied to obtain microstructures with desired material property. Due to the special design of the network architecture, the proposed methodology is able to identify the latent (design) variables with desired dimensionality, as well as capturing complex ma- Copyright © 2018, The Authors. All rights reserved.

关键词： Microstructure

来源：评论

学校读者我要写书评

暂无评论

Dynamics of topological solitons, knotted streamlines, and transport of cargo in liquid crystals

引用

Physical Review E 2018年第5期97卷 052701-052701页

作者： Hayley R. O. Sohn Paul J. Ackerman Timothy J. Boyle Ghadah H. Sheetah Bengt Fornberg Ivan I. Smalyukh Soft Materials Research Center and Materials Science and Engineering Program University of Colorado Boulder Colorado 80309 USA Department of Physics and Department of Electrical Computer and Energy Engineering University of Colorado Boulder Colorado 80309 USA Department of Applied Mathematics University of Colorado Boulder Colorado 80309 USA Renewable and Sustainable Energy Institute National Renewable Energy Laboratory and University of Colorado Boulder Colorado 80309 USA

Active colloids and liquid crystals are capable of locally converting the macroscopically supplied energy into directional motion and promise a host of new applications, ranging from drug delivery to cargo transport at the mesoscale. Here we uncover how topological solitons in liquid crystals can locally transform electric energy to translational motion and allow for the transport of cargo along directions dependent on frequency of the applied electric field. By combining polarized optical video microscopy and numerical modeling that reproduces both the equilibrium structures of solitons and their temporal evolution in applied fields, we uncover the physical underpinnings behind this reconfigurable motion and study how it depends on the structure and topology of solitons. We show that, unexpectedly, the directional motion of solitons with and without the cargo arises mainly from the asymmetry in rotational dynamics of molecular ordering in liquid crystal rather than from the asymmetry of fluid flows, as in conventional active soft matter systems.

关键词： Chirality Topological defects Active nematics Cholesteric liquid crystals Nanoparticles Nematic liquid crystals Soft colloids Solitons

来源：评论

学校读者我要写书评

暂无评论

Solid-state dewetting on curved substrates

arXiv

引用

arXiv 2018年

作者： Jiang, Wei Wang, Yan Srolovitz, David J. Bao, Weizhu School of Mathematics and Statistics Wuhan University Wuhan430072 China Beijing Computational Science Research Center Beijing100193 China Departments of Materials Science and Engineering and Mechanical Engineering and Applied Mechanics University of Pennsylvania PhiladelphiaPA19104 United States Department of Mathematics National University of Singapore 119076 Singapore

Based on the thermodynamic variation to the free energy functional, we propose a sharp-interface model for simulating solid-state dewetting of thin films on rigid curved substrates in two dimensions. This model describes the interface evolution which occurs through surface diffusion-controlled mass transport and contact point migration along the curved substrate. Furthermore, the surface energy anisotropy is easily included into the model, and the contact point migration is explicitly described by the relaxed contact angle boundary condition. We implement the mathematical model by a semiimplicit parametric finite element method to study several interesting phenomena, such as "small" particle migration on curved substrates and templated solid-state dewetting on a pre-patterned substrate. Based on ample numerical simulations, we demonstrate that, the migration velocity of a "small" solid particle is proportional to the substrate curvature gradient ′ and inversely proportional to the square root of the area of the particle pA, and it decreases when the isotropic Young angle i increases. In addition, we also observe four periodic categories of dewetting on a pre-patterned sinusoidal substrate. Our approach can provide a convenient and powerful tool to exploring how to produce well-organized nanoparticles by making use of template-assisted solid-state dewetting. Copyright © 2018, The Authors. All rights reserved.

关键词： Free energy

来源：评论

学校读者我要写书评

暂无评论

Stretchable Electronics: Biaxially Stretchable Ultrathin Si Enabled by Serpentine Structures on Prestrained Elastomers (Adv. Mater. Technol. 1/2019)

引用

Advanced materials Technologies 2019年第1期4卷

作者： Kyoseung Sim Yuhang Li Jizhou Song Cunjiang Yu Materials Science and Engineering Program University of Houston Houston TX 77204 USA Institute of Solid Mechanics Beihang University Beijing 100191 China Department of Engineering Mechanics Soft Matter Research Center and Key Laboratory of Soft Machines and Smart Devices of Zhejiang Province Zhejiang University Hangzhou Zhejiang 310027 China Department of Mechanical Engineering Department of Electrical and Computer Engineering Department of Biomedical Engineering Materials Science and Engineering Program Texas Center for Superconductivity at the University of Houston University of Houston Houston TX 77204 USA

来源：评论

学校读者我要写书评

暂无评论

Bandgap closing at the screw dislocations of WS2 spirals

arXiv

引用

arXiv 2019年

作者： Zhang, Xin Hu, Kaige Li, Yifei Wei, Guohua Stern, Nathaniel P. Pan, Min Li, Xiao Luo, Hong Liu, Lei Department of Physics University at Buffalo State University of New York BuffaloNY14260 United States School of Physics and Optoelectronic Engineering Guangdong University of Technology Guangzhou510006 China Department of Materials Science and Engineering College of Engineering Peking University Beijing100871 China Applied Physics Program Northwestern University 2145 Sheridan Road EvanstonIL60208 United States Department of Physics and Astronomy Northwestern University 2145 Sheridan Road EvanstonIL60208 United States Superconductivity and New Energy R&D Center Southwest JiaoTong University Chengdu Sichuan610031 China Center for Quantum Transport and Thermal Energy Science School of Physics and Technology Nanjing Normal University Nanjing210023 China

Van der Waals (vdW) layered transition metal dichalcogenides (TMDCs) materials are emerging as one class of quantum materials holding novel optical and electronic properties. In particular, the bandgap tunability attractive for nanoelectronics technology have been observed up to 1.1 eV when applying dielectric screening or grain boundary engineering. Here we present the experimental observation of bandgap closing at the center of the screw dislocation-driven WS2 spiral pyramid by means of scanning tunneling spectroscopy, which is validated by first-principle calculations. The observed giant bandgap modulation is attributed to the presence of dangling bonds induced by the W-S broken and the enhanced localized stress in the core of the dislocation. Achieving this metallic state and the consequent vertical conducting channel presents a pathway to 3D-interconnected vdW heterostructure devices based on emergent semiconducting TMDCs. Copyright © 2019, The Authors. All rights reserved.

关键词： Van der Waals forces

来源：评论

学校读者我要写书评

暂无评论

Time and flow stress dependences of internal stress during stress relaxation

引用

Procedia Manufacturing 2018年 15卷 1746-1753页

作者： Yoshinori Kusuda Kodai Murasawa Yurina Suzuki Shinsuke Suzuki Masato Takamura Tomoyuki Hakoyama Yoshimasa Ikeda Yoshie Otake Takayuki Hama Department of Applied Mechanics and Aerospace Engineering Faculty of Fundamental Science and Engineering Waseda University 3-4-1 Okubo Shinjuku Tokyo 169-8555 Japan Kagami Memorial Research Institute for Materials Science and Technology Waseda University 2-8-26 Nishiwaseda Shinjuku Tokyo 169-0051 Japan RIKEN Center for Advanced Photonics 2-1 Hirosawa Wako Saitama 351-0198 Japan Department of Energy Science and Technology Kyoto University Yoshida-honmachi Sakyo Kyoto 606-8501 Japan

Stress relaxation is a potential cause of formability improvement. To describe stress relaxation, the measurement of internal stress is essential. We investigated the time and flow stress dependences of the internal stress by conducting a strain-rate-change test and stress-dip test. The comparison between the two tests revealed that the internal stress decreases as the stress relaxation progresses over time. Moreover, the internal stress decreases as the flow stress decreases. We propose that the time dependence of the internal stress could have been caused by the flow stress dependence of the internal stress because the flow stress-internal stress and the initial stress-internal stress relationships are approximately identical.

关键词： Stress relaxation High tensile strength steel Thermal activated processs Strain-rate-change test Stress-dip test Strain rate dependence of flow stress Internal stress Dynamic recovery Work hardening

来源：评论

学校读者我要写书评

暂无评论

建议与咨询留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

时间限定

文献类型

馆藏选择

核心期刊

语言

文献类型

帮助

文字说明：

检索规则说明：

检索范例：

分类表

所选分类

限定检索结果

文献类型

馆藏范围

日期分布

学科分类号

主题

机构

作者

语言

请选择保存的检索档案：

请选择收藏分类：

通借通还

建议与咨询 留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

时间限定

文献类型

馆藏选择

核心期刊

语言

文献类型

帮助

文字说明：

检索规则说明：

检索范例：

分类表

所选分类

限定检索结果

文献类型

馆藏范围

日期分布

学科分类号

主题

机构

作者

语言

请选择保存的检索档案： 新增检索档案 确定 取消

请选择收藏分类： 新增自定义分类 确定 取消

通借通还

建议与咨询留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

请选择保存的检索档案：

请选择收藏分类：