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Photocatalysis: Homojunction of Oxygen and Titanium Vacancies and its Interfacial n–p Effect (Adv. Mater. 32/2018)

advanced Materials 2018年第32期30卷

作者： Si‐Ming Wu Xiao‐Long Liu Xi‐Liang Lian Ge Tian Christoph Janiak Yue‐Xing Zhang Yi Lu Hao‐Zheng Yu Jie Hu Hao Wei Heng Zhao Gang‐Gang Chang Gustaaf Van Tendeloo Li‐Ying Wang Xiao‐Yu Yang Bao‐Lian Su State Key Laboratory of Advanced Technology for Materials Synthesis and Processing Wuhan University of Technology 122 Luoshi Road Wuhan 430070 China State Key Laboratory of Magnetic Resonance and Atomic and Molecular Physics Wuhan Institute of Physics and Mathematics The Chinese Academy of Sciences Wuhan 430071 China Institut für Anorganische Chemie und Strukturchemie Heinrich‐Heine‐Universität Düsseldorf 40204 Düsseldorf Germany Hubei Collaborative Innovation Center for Advanced Organic Chemical Materials Ministry of Education Key Laboratory for the Synthesis and Application of Organic Functional Molecules College of Chemistry and Chemical Engineering Hubei University Wuhan 430062 China EMAT (Electron Microscopy for Materials Science) University of Antwerp Groenenborgerlaan 171 B‐2020 Antwerpen Belgium School of Engineering and Applied Sciences Harvard University Cambridge MA 02138 USA Laboratory of Inorganic Materials Chemistry (CMI) University of Namur 61 rue de Bruxelles B‐5000 Namur Belgium

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Influences of thermal molding process on the flexural properties of SiC/SiC composites with a new precursor polymer

Influences of thermal molding process on the flexural proper...

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Chinese Materials Congress, CMC 2014

作者： Luo, Zheng Zhou, Xin Gui Yu, Jin Shan Wang, Fei Science and Technology on Advanced Ceramic Fibers and Composites Laboratory National University of Defense Technolog Changsha410073 China

ISBN: (纸本)9783038353959

Silicon carbide (SiC) fiber reinforced SiC matrix composites (SiC/SiC) were fabricated by precursor impregnation and pyrolysis (PIP) process with a new precursor polymer, liquid polyvinylcarbosilane (LPVCS). The molding process was conducted during the cross-linking reactions of LPVCS for the first PIP cycle. The influences of molding pressure and molding time on the flexure properties of the SiC/SiC composites were studied. The results indicated that the optimal molding pressure and molding time were 3MPa and 5h respectively due to the fine interfacial bonding between fiber and matrix. The density of the SiC/SiC composites was 2.16g/cm3. The flexural strength and fracture toughness of the SiC/SiC composites were 637.5MPa and 29.8MPa·m1/2 respectively. © (2015) Trans Tech Publications, Switzerland.

关键词： Silicon carbide

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Possible structural origin of superconductivity in Sr-doped Bi2Se3

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Physical Review Materials 2018年第1期2卷 014201-014201页

作者： Zhuojun Li Meng Wang Dejiong Zhang Nan Feng Wenxiang Jiang Chaoqun Han Weijiong Chen Mao Ye Chunlei Gao Jinfeng Jia Jixue Li Shan Qiao Dong Qian Ben Xu He Tian Bo Gao CAS Center for Excellence in Superconducting Electronics (CENSE) Shanghai 200050 China State Key Laboratory of Functional Materials for Informatics Shanghai Institute of Microsystem and Information Technology Chinese Academy of Sciences 865 Changning Road Shanghai 200050 China University of Chinese Academy of Sciences Beijing 100049 China Center of Electron Microscopy and State Key Laboratory of Silicon Materials School of Materials Science and Engineering Zhejiang University Hangzhou 310027 China State Key Laboratory of New Ceramics and Fine Processing Department of Materials Science and Engineering Tsinghua University Beijing 100084 People's Republic of China Key Laboratory of Artificial Structures and Quantum Control (Ministry of Education) School of Physics and Astronomy Shanghai Jiao Tong University Shanghai 200240 China State Key Laboratory of Surface Physics and Department of Physics Fudan University Shanghai 200433 China Collaborative Innovation Center of Advanced Microstructures Nanjing 210093 China

Doping bismuth selenide (Bi2Se3) with elements such as copper and strontium (Sr) can induce superconductivity, making the doped materials interesting candidates to explore potential topological superconducting behaviors. It was thought that the superconductivity of doped Bi2Se3 was induced by dopant atoms intercalated in van der Waals gaps. However, several experiments have shown that the intercalation of dopant atoms may not necessarily make doped Bi2Se3 superconducting. Thus, the structural origin of superconductivity in doped Bi2Se3 remains an open question. Herein, we combined material synthesis and characterization, high-resolution transmission electron microscopy, and first-principles calculations to study the doping structure of Sr-doped Bi2Se3. We found that the emergence of superconductivity is strongly related with n-type dopant atoms. Atomic-level energy-dispersive x-ray mapping revealed various n-type Sr dopants that occupy intercalated and interstitial positions. First-principles calculations showed that the formation energy of a specific interstitial Sr doping position depends strongly on the Sr doping level. This site changes from a metastable position at low Sr doping level to a stable position at high Sr doping level. The calculation results explain why quenching is necessary to obtain superconducting samples when the Sr doping level is low and also why slow furnace cooling can yield superconducting samples when the Sr doping level is high. Our findings suggest that Sr atoms doped at interstitial locations, instead of those intercalated in van der Waals gaps, are most likely to be responsible for the emergence of superconductivity in Sr-doped Bi2Se3.

关键词： Dopants Impurities in superconductors

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Orbital selective neutron spin resonance in underdoped superconducting NaFe0.985Co0.015As

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Physical Review B 2017年第9期95卷 094519-094519页

作者： Weiyi Wang J. T. Park Rong Yu Yu Li Yu Song Zongyuan Zhang Alexandre Ivanov Jiri Kulda Pengcheng Dai Department of Physics and Astronomy Rice University Houston Texas 77005 USA Heinz Maier-Leibnitz Zentrum (MLZ) Technische Universität München D-85747 Garching Germany Department of Physics and Beijing Key Laboratory of Opto-electronic Functional Materials and Micro-nano Devices Renmin University of China Beijing 100872 China Department of Physics and Astronomy Shanghai Jiao Tong University Shanghai 200240 China and Collaborative Innovation Center for Advanced Microstructures Nanjing 210093 China School of Physics Huazhong University of Science and Technology Wuhan Hubei 430074 China Institut Laue-Langevin 71 Avenue des Martyrs F-038000 Grenoble France Center for Advanced Quantum Studies and Department of Physics Beijing Normal University Beijing 100875 China

We use neutron scattering to study the electron-doped superconducting NaFe0.985Co0.015As (Tc=14 K), which has coexisting static antiferromagnetic (AF) order (TN=31 K) and exhibits two neutron spin resonances (Er1≈3.5 meV and Er2≈6 meV) at the in-plane AF ordering wave vector QAF=Q1=(1,0) in reciprocal space. In the twinned state below the tetragonal-to-orthorhombic structural transition Ts, both resonance modes appear at Q1 but cannot be distinguished from Q2=(0,1). By detwinning the single crystal with uniaxial pressure along the orthorhombic b axis, we find that both resonances appear only at Q1 with vanishing intensity at Q2. Since electronic bands of the orbital dxz and dyz characters split below Ts with the dxz band sinking ∼10 meV below the Fermi surface, our results indicate that the neutron spin resonances in NaFe0.985Co0.015As arise mostly from quasiparticle excitations between the hole and electron Fermi surfaces with the dyz orbital character.

关键词： Antiferromagnetism Superconductivity Single crystal materials Neutron scattering

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Miscibility,Intramolecular Specific Interactions and Mechanical Properties of a DGEBA Based Epoxy Resin Toughened with a Sliding Graft Copolymer

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Chinese Journal of Polymer science 2015年第3期33卷 433-443页

作者： Xue Li Hai-lan Kang Jian-xiang Shen 张立群 Toshio Nishi Kohzo Ito State Key Laboratory for Organic-Inorganic Composites Beijing University of Chemical Technology Key Laboratory of Beijing City for Preparation and Processing of Novel Polymer Materials Beijing University of Chemical Technology Department of Applied Physics The University of Tokyo Department of Advanced Materials Science Graduate School of Frontier SciencesThe University of Tokyo

The ＂sliding graft copolymer＂（SGC）, in which many linear poly-ε-caprolactone （PCL） side chains are bound to cyclodextrin rings of a polyrotaxane （PR）, was prepared and employed to toughen diglycidyl ether of bisphenol A （DGEBA） based epoxy resin. The aim of the work is to understand the effect of SGC on the miscibility, morphology, thermal behavior, curing reaction and mechanical performance of the cured systems. From differential scanning calorimetry （DSC） analysis and dynamic mechanical thermal analysis （DMTA） of DGEBA/SGC thermosetting blends, it is found that DGEBA and SGC are miscible in the amorphous state. Fourier transform infrared spectroscopy （FTIR） suggested that the miscibility between SGC and DGEBA is due to the existence of intermolecular specific interactions （viz. hydrogen bonding）. The impact strength is improved by 4 times for DGEBA/SGC （80/20） blends compared with that of the unmodified system. The increase in toughness of SGC-modified thermosets can be explained by the effect of intermolecular specific interactions of SGC with DGEBA, which is beneficial to induce the plastic deformation of matrix. This is the first report on utilizing this novel supramolecular polymer to toughen rigid epoxy matrix.

关键词： Epoxy Sliding graft copolymer Toughen Miscibility Hydrogen bonding.

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Pure Dielectric Waveguides Enable Compact, Ultrabroadband Wave Plates

IEEE Photonics Journal

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IEEE Photonics Journal 2016年第5期8卷

作者： Guo, Jianjun Liang, Yao Huang, Xu Guang Guo, Banghong Li, Jun Guangdong Provincial Key Laboratory of Nanophotonic Functional Materials and Devices South China Normal University Guangzhou China Centre for Micro-Photonics Faculty of Science Engineering and Technology Swinburne University of Technology HawthornVIC Australia Guangzhou Key Laboratory for Special Fiber Photonic Devices and Applications Specially Functional Fiber Engineering Technology Research South China Normal University Guangzhou China Key Laboratory of Quantum Information University of Science and Technology of China Chinese Academy of Sciences Hefei China South China Academy of Advanced Optoelectronics South China Normal University Guangzhou China

The ability to manipulate polarization of light on a chip is of fundamental importance for many applications. Here, we demonstrate an ultrabroadband quarter-wave plate for silicon photonics based on pure dielectric waveguides. The concept of birefringence is used to introduce a phase lag of π/2 between two orthogonally polarized modes in nanophotonic waveguides, such that a quasi-linearly polarized mode is converted into a quasi-circularly polarized mode, which is accompanied with a longitudinal optical vortex component due to the spin-orbit interaction. Our device is ultracompact (2.3 μm) with low insertion losses (around 0.05 dB), and it allows for an ultrabroad operation bandwidth of 280 nm around 1.55 μm. We also propose a half-wave plate structure, which can either serve as a chiral converter for quasi-circularly polarized modes or a polarization rotator for quasi-linearly polarized modes. These results may find important applications in many fields, such as integrated quantum computing and polarization handling on a chip. © 2016 IEEE.

关键词： Circular polarization

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Photoemission study of the electronic structure of valence band convergent SnSe

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Physical Review B 2017年第16期96卷 165118-165118页

作者： C. W. Wang Y. Y. Y. Xia Z. Tian J. Jiang B. H. Li S. T. Cui H. F. Yang A. J. Liang X. Y. Zhan G. H. Hong S. Liu C. Chen M. X. Wang L. X. Yang Z. Liu Q. X. Mi G. Li J. M. Xue Z. K. Liu Y. L. Chen Center for Excellence in Superconducting Electronics State Key Laboratory of Functional Material for Informatics Shanghai Institute of Microsystem and Information Technology Chinese Academy of Sciences Shanghai 200050 China School of Physical Science and Technology ShanghaiTech University CAS-Shanghai Science Research Center Shanghai 200031 China University of Chinese Academy of Sciences Beijing 100049 China Shanghai Institute of Applied Physics Chinese Academy of Sciences Shanghai 201800 China Shanghai Institute of Optics and Fine Mechanics Chinese Academy of Sciences Shanghai 201800 China Advanced Light Source Lawrence Berkeley National Laboratory Berkeley California 94720 USA Pohang Accelerator Laboratory POSTECH Pohang 790-784 Korea Shanghai Institute of Ceramics Chinese Academy of Sciences Shanghai 200050 China Department of Physics University of Oxford Oxford OX1 3PU United Kingdom Collaborative Innovation Center of Quantum Matter Beijing China State Key Laboratory of Low Dimensional Quantum Physics Department of Physics and Collaborative Innovation Center of Quantum Matter Tsinghua University Beijing 100084 China

IV-VI semiconductor SnSe has been known as the material with record high thermoelectric performance. The multiple close-to-degenerate (or “convergent”) valence bands in the electronic band structure has been one of the key factors contributing to the high power factor and thus figure of merit in the SnSe single crystal. To date, there have been primarily theoretical calculations of this particular electronic band structure. In this paper, however, using angle-resolved photoemission spectroscopy, we perform a systematic investigation of the electronic structure of SnSe. We directly observe three predicted hole bands with small energy differences between their band tops and relatively small in-plane effective masses, in good agreement with the ab initio calculations and critical for the enhancement of the Seebeck coefficient while keeping high electrical conductivity. Our results reveal the complete band structure of SnSe and help to provide a deeper understanding of the electronic origin of the excellent thermoelectric performances in SnSe.

关键词： Electronic structure Seebeck effect Angle-resolved photoemission spectroscopy Density functional theory Hybrid functionals

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Coherence enhanced quantum metrology in a nonequilibrium optical molecule

arXiv

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arXiv 2017年

作者： Wang, Zhihai Wu, Wei Cui, Guodong Wang, Jin Center for Quantum Sciences School of Physics Northeast Normal University Changchun130024 China Center for Advanced Optoelectronic Functional Materials Research Key Laboratory for UV-Emitting Materials and Technology of Ministry of Education Northeast Normal University Changchun130024 China Beijing Computational Science Research Center Beijing100094 China State Key Laboratory of Electroanalytical Chemistry Changchun Institute of Applied Chemistry Chinese Academy of Sciences Changchun130022 China Department of Physics and Astronomy State University of New York at Stony Brook NY11794 United States Department of Chemistry State University of New York at Stony Brook NY11794 United States

We explore the quantum metrology in an optical molecular system coupled to two environments with different temperatures, using a quantum master equation beyond secular approximation. We discover that the steady-state coherence originating from and sustained by the nonequilibrium condition can enhance quantum metrology. We also study the quantitative measures of the nonequilibrium condition in terms of the curl flux, heat current and entropy production at the steady state. They are found to grow with temperature difference. However, an apparent paradox arises considering the contrary behaviors of the steady-state coherence and the nonequilibrium measures in relation to the inter-cavity coupling strength. This paradox is resolved by decomposing the heat current into a population part and a coherence part. Only the latter, coherence heat current, is tightly connected to the steady-state coherence and behaves similarly with respect to the inter-cavity coupling strength. Interestingly, the coherence heat current flows from the low-temperature reservoir to the high-temperature reservoir, opposite to the direction of the population heat current. Our work offers a viable way to enhance quantum metrology for open quantum systems through steady-state coherence sustained by the nonequilibrium condition, which can be controlled and manipulated to maximize its utility. The potential applications go beyond quantum metrology and extend to areas such as device designing, quantum computation and quantum technology in general. Copyright © 2017, The Authors. All rights reserved.

关键词： Temperature

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Influence of temperatures on the formation of SiBCN powders prepared by CVD using borazine and liquid polycarbosilane

Influence of temperatures on the formation of SiBCN powders ...

引用

Chinese Materials Congress, CMC 2014

作者： Sun, Xun Li, Jun Sheng Cheng, Hai Feng Science and Technology on Advanced Ceramic Fibers and Composites Laboratory National University of Defense Technology 109 Deya Road Changsha410073 China

ISBN: (纸本)9783038353959

SiBCN powders have been prepared by chemical vapor deposition using borazine and liquid polycarbosilane as source precursors in the deposition temperature range from 800 °C to 1100 °C, with the pressure of 10 kPa. The effect of the temperatures on the surface morphologies of the as-received powders was investigated by SEM. FTIR analysis of the powders was used to obtain the composition of the powders, and the XRD analysis was used to determine the crystalline state of the deposits. The results showed the powders were amorphous and composed of normally spherical grains. © (2015) Trans Tech Publications, Switzerland.

关键词： Powders

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Effect of curing methods on the mechanical property of SiC fiber prepared via hydrogenation

Effect of curing methods on the mechanical property of SiC f...

引用

Chinese Materials Congress, CMC 2014

作者： Wang, Yi Fei Xing, Zhong Fang Liu, Cheng Ming Science and Technology on Advanced Ceramic Fibers and Composites Laboratory National University of Defense Technology 109 Deya Road Changsha410073 China

ISBN: (纸本)9783038353959

Two different polycarbosilane (PCS) fibers were prepared by a new oxygen-free curing method and Chemical Vapor Curing (CVC), respectively. Nearly stoichiometric SiC fiber was prepared via hydrogenation in H2-N2 mixture and subsequent sintering in inert gases. The green PCS fiber and nearly stoichiometric SiC fiber were characterized by FT-IR, XRD, SEM etc. Meanwhile, the effect of hydrogenation on the thermal stability of SiC fibres cured by CVC method was studied. It was found that the oxygen-free curing method can effectively decrease the content of oxygen in the final SiC fiber, while the hydrogenation treatment can dramatically diminish the content of free carbon, so the nearly stoichiometric SiC fiber with C/Si atomic ratio being 1.06 can be obtained. After the heat-treated at 1600℃ in inert gases, the strength retaining ratio of the oxygen-free cured SiC achieved 68%, demonstrating that the nearly stoichiometric SiC fiber possesses excellent high-temperature stability and higher anti-oxidation property. © (2015) Trans Tech Publications, Switzerland.

关键词： Oxygen

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