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Electronic and magnetic structures of chain structured ironselenide compounds

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Frontiers of physics 2014年第4期9卷 465-471页

作者： Wei Li Chandan Setty x. h. Chen Jiangping hu State Key Laboratory of Functional Materials for Informatics and Shanghai Center for Superconductivity Shanghai Institute of Microsystem and Information Technology Chinese Academy of Sciences Shanghai 200050 China Department of Physics and State Key Laboratory of Surface Physics Fudan University Shanghai 200433 China Department of Physics Purdue University West Lafayette IA 47907 USA hefei National Laboratory for Physical Science at Microscale and Department of Physics University of Science and Technology of China Hefei 230026 China Beijing National Laboratory for Condensed Matter Physics and Institute of Physics Chinese Academy of Sciences Beijing 100190 China

Electronic and magnetic structures of iron selenide compounds Ce2O2FeSe2 （2212＊） and BaFe2Se3 （123＊） are studied by the first-principles calculations. We find that while all these compounds are composed of one-dimensional （1D） Fe chain （or ladder） structures, their electronic structures are not close to be quasi-lD. The magnetic exchange couplings between two nearest-neighbor （NN） chains in 2212＊ and between two NN two-leg-ladders in 123＊ are both antiferromagnetic （AFM）, which is consistent with the presence of significant third NN AFM coupling, a common feature shared in other iron-chalcogenides, FeTe （11＊） and KyFe2-xSe2 （122＊）. In magnetic ground states, each Fe chain of 2212＊ is ferromagnetic and each two-leg ladder of 123＊ form a block-AFM structure. We suggest that all magnetic structures in iron-selenide compounds can be unified into an extended J1-J2-J3 model. Spin-wave excitations of the model are calculated and can be tested by future experiments on these two systems.

关键词： first-principles calculations magnetism spin-wave excitations

Size and Interface Effects on Tensile Strength of Polymers with Nano/Micro Particle Inclusions

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Acta Mechanica Solida Sinica 2024年第5期37卷 812-822页

作者： R.Yuan x.Ma L.h.Liang Y.Wei College of Mechanical and Electrical Engineering Beijing University of Chemical TechnologyBeijing100029China Beijing Key Lab of health Monitoring and Self-Recovery for high-End Mechanical Equipment Beijing100029China College of Engineering Peking UniversityBeijing100871China

Polymers with particle inclusions have wide applications,and the mechanical properties of polymer composites affect their reliability in *** strength of these composites is dependent on factors such as particle fraction,size,distribution,and interface interaction between the two phases,in addition to the properties of the polymers and *** size effect of particles and interface damage play an important role and thus draw considerable *** this paper,the size-and interface-dependent strength of polypropylene(PP)with nano/micro silica(SiO_(2))particles of different fractions is studied through a combination of tensile experiments on a series of samples and corresponding three-dimensional(3D)finite element *** results indicate that PP with 2%SiO_(2)nanoparticles of 50 nm exhibits relatively higher tensile strength,shedding light on the microstructure mechanism where smaller particle sizes lead to better interface ***,the particle size and interface coupling effect is analyzed based on the size-dependent elastic modulus model and the interface-cohesive *** simulation demonstrates the local interface damage evolution around a particle of the composites in *** findings are beneficial for designing polymer composites with nanoparticle inclusions.

关键词： Polymer-matrix composites Ceramic nanoparticles Mechanical properties Size effect Interface damage

Great strides of China's space programmes

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National Science Review 2017年第2期4卷 264-268页

作者： Jane qiu 机构不详

While China’s almost flawless space endeavours—such as its space lab Tiangong-2,launched last year,and the2012 mission that sent a rover to the surface of the Moon—have long impressed the world,space-science missio... 详细信息

关键词： Great strides of China’s space programmes very

Characterization and Photoluminescence Properties of Alumina Nanowires Elaborated by Arc-Plasma

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Journal of Materials Science & Technology 2006年第1期22卷 127-129页

作者： C.Arnoult x.Devaux h.Rinnert M.Vergnat Laboratoire de Physique des Materiaux UMR CNRS 7556Ecole des MinesCS14234F54042 Nancy cedexPrance

Ultrafine powders containing alumina nanowires are synthesized by DC arc plasma from pure aluminium metal. Nanowires grow only when reactive gases are composed of nitrogen and less than ten percent of oxygen. Nanowires have the diameters ranging from 20 to 80 nm and lengths ranging from hundreds nanometers to tens of micrometers. A first assumption of the mechanism process is proposed, in which nanowires grow starting directly from the aluminium. Photoluminescence measurements show that the powders have three emission peaks around 435, 530 and 750 nm resulting from different kinds of defects such as oxygen vacancies, aluminium interstitial ions and surface defects.

关键词： Nanowires Alumina Arc plasma Photoluminescence

Microstructure evolution and shape memory behaviors of Ni_(47)Ti_(44)Nb_(9)alloy subjected to multistep thermomechanical loading with different prestrain levels

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Journal of Materials Science & Technology 2024年第4期171卷 80-93页

作者： Y.h.Zhang h.Li Z.W.Yang x.Liu Q.F.Gu State Key Laboratory of Solidification Processing School of Materials Science and EngineeringNorthwestern Polytechnical UniversityXi’an 710072China Shaanxi Key Laboratory of high-Performance Precision Forming Technology and Equipment Northwestern Polytechnical UniversityXi’an 710072China

Ni_(47)Ti_(44)Nb_(9)shape memory alloy(SMA)is a promising material in the aerospace field due to its wide transformation *** application of shape memory effect depends on multistep thermomechan-ical loading,viz.,low-temperature deformation and subsequent heating to ***-temperature deformation prestrain plays a pivotal role in shape memory properties tailoring of SMA ***,microstructure evolution and deformation mechanisms of Ni_(47)Ti_(44)Nb_(9)SMA subjected to vari-ous prestrain levels are still *** this end,microstructure evolution and shape memory behaviors of Ni_(47)Ti_(44)Nb_(9)alloy subjected to multistep thermomechanical loading with prestrain levels of 8%-16%at-28℃(M_(s)+30℃)were *** results demonstrate that the stress-strain curve of the specimen exhibits four distinct stages at a maximal prestrain of 16%.Whereas stageⅡand stageⅢend at prestrains of∼8%and∼12%,*** stageⅡ,the stress-induced martensitic transformation is accompanied by the dislocation slip of the NiTi matrix andβ-Nb *** stageⅢ,in addition to the higher density of dislocations and further growth of stress-induced martensite variants(SIMVs),(001)compound twins are introduced as a result of the(001)deformation twinning in stress-induced ***{20-1}martensite twins are gradually introduced in stageⅣ.Correspondingly,after subsequent unloading and heating,a higher density of{114}austenite twins form in the specimen with a larger prestrain of 16%.With increasing prestrain from 8%to 16%,the recoverable strainε_(re)^(T)upon heating increases first and then ***ε_(re)^(T)obtains a maximum of 7.03%at 10%prestrain and de-creases to 6.17%at 16%*** increase ofε_(re)^(T)can be attributed to the formation of new SIMVs,the further growth of existing SIMVs,and the recoverable(001)compound *** the decrease ofε_(re)^(T)is mainly associated with the irrecoverable strain by{20−1}martensite *** effe

关键词： Ni_(47)Ti_(44)Nb_(9)shape memory alloy Wide transformation hysteresis Thermomechanical loading Microstructure evolution Shape memory behaviors Stress-induced martensitic transformation Deformation twinning

Multi-objective pigeon-inspired optimization for brushless direct current motor parameter design

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Science China(Technological Sciences) 2015年第11期58卷 1915-1923页

作者： qiu huaxin DUAN haiBin Bio-inspired Autonomous Flight Systems(BAFS) Research Group Science and Technology on Aircraft Control Laboratory School of Automation Science and Electrical Engineering Beihang University

Pigeon-inspired optimization(PIO) is a new swarm intelligence optimization algorithm, which is inspired by the behavior of homing pigeons. A variant of pigeon-inspired optimization named multi-objective pigeon-inspired optimization(MPIO) is proposed in this paper. It is also adopted to solve the multi-objective optimization problems in designing the parameters of brushless direct current motors, which has two objective variables, five design variables, and five constraint variables. Furthermore, comparative experimental results with the modified non-dominated sorting genetic algorithm are given to show the feasibility, validity and superiority of our proposed MIPO algorithm.

关键词： brushless direct current (BLDC) motor multi-objective pigeon-inspired optimization (MPIO) electromagnetics mul-ti-objective optimization

First-Principle Calculations of hardness and Melting Point of Mo_2C

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Journal of Materials Science & Technology 2009年第3期25卷 419-422页

作者： x.R. Wang M.F. Yan h.T. Chen School of Materials Science and Engineering Harbin Institute of Technology Harbin 150001 China

This paper has constructed two kinds of atomic and electronic models for hexagonal β-Mo2C and orthorhombic α-Mo2C. The optimized lattice parameters, elastic constant matrixes and overlap population for Mo2C crystal cells have been obtained to realize the characterization of the hardness and melting point of the two structures by the first-principles plane wave pseudo potential method based on the density functional theory. The results reveal that the calculated lattice parameters of the Mo2C crystal cells agree with the experimental and other calculated data. The calculated melting point/hardness are 2715 K/11.38 GPa for β-Mo2C and 2699 K/10.57-12.67 GPa for α-Mo2C, respectively. The calculated results from the density of states （DOS） demonstrate that the hybridization effect between Mo-3d and C-2p states in α-Mo2C crystal cell is much stronger than that in β-Mo2C one.

关键词： First-principle Mo2C hardness Melting point Density of states

Electrochemical conversion of organic compounds and inorganic small molecules

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Science China Chemistry 2024年第10期67卷 3223-3246页

作者： Weimei Zeng Youai qiu Department of Chemistry Nankai UniversityTianjin 300071China

Electrochemical synthesis presents a facile and sustainable strategy to produce valuable *** review summarizes the most recent advances in electrosynthesizing value-added compounds with inorganic small ***“small molecules”refers to a broad spectrum of chemicals,we mainly focus on the electrochemical conversion of CO_(2),h_(2)O/D_(2)O,Nh_(3)and SO_(2)until March *** review intends to compare the results and display general trends throughout the field,with an emphasis on the substrate scope and mechanical ***,we propose several techniques and protocols that can enable a more fundamental understanding of the electrochemical reaction involving inorganic small molecules and help drive this methodology toward commercialization.

关键词： electrochemical synthesis inorganic small molecule organic synthesis carbon dioxide water

Removal of Cd(Ⅱ)from dilute aqueous solutions by complexation–ultrafiltration using rotating disk membrane and the shear stability of PAA–Cd complex

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Chinese Journal of Chemical Engineering 2019年第3期27卷 519-527页

作者： Liang Chen Yunren qiu School of Chemistry and Chemical Engineering Central South University

Removal of cadmium(Ⅱ) ions from dilute aqueous solutions by complexation–ultrafiltration using rotating disk membrane was investigated. Polyacrylic acid sodium(PAAS) was used as complexation agent, as key factors of complexation, ph and the mass ratio of PAAS to Cd^(2+)(P/M) were studied, and the optimum complexation–ultrafiltration conditions were obtained. The effects of rotating speed(n) on the stability of PAA–Cd complex was studied with two kinds of rotating disk, disk Ⅰ(without vane) and disk Ⅱ(with six rectangular vanes) at a certain range of rotating speed. Both of the rejection could reach 99.7% when n was lower than 2370 r·min^(-1) and 1320 r·min^(-1), for disk I and disk Ⅱ, respectively. however, when rotating speed exceeds a certain value,the critical rotating speed(n_c), the rejection of Cd(Ⅱ) decreases greatly. The distribution of form of cadmium on the membrane was established by the membrane partition model, and the critical shear rate(γ_c), the smallest shear rate at which the PAA–Cd complex begins to dissociate, was calculated based on the membrane partition model and mass balance. The critical shear rates(γ_c) of PAA–Cd complex were 5.9 × 10~4 s^(-1), 1.01 × 10~5 s^(-1),and 1.31 × 10~5 s^(-1) at ph = 5.0, 5.5, and 6.0, respectively. In addition, the regeneration of PAAS was achieved by shear induced dissociation and ultrafiltration.

关键词： Complexation-ultrafiltration Membrane Regeneration Shear stability Critical shear rate Shear induced dissociation