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Electronic structures and strengthening mechanisms of superhard high-entropy diborides

稀有金属：英文版 2023年第2期42卷 614-628页

作者： Gang Yao William-Yi Wang Pei-Xuan Li Ke Ren Jia-Qi Lu Xing-Yu Gao De-Ye Lin Jun Wang Yi-Guang Wang Hai-Feng Song Zi-Kui Liu Jin-Shan Li State Key Laboratory of Solidification Processing Northwestern Polytechnical UniversityXi’an710072China Innovation Center NPU ChongqingChongqing401135China Laboratory of Computational Physics Institute of Applied Physics and Computational MathematicsBeijing100088China Institute of Advanced Structure Technology Beijing Institute of TechnologyBeijing100081China Department of Materials science and Engineering The Pennsylvania State UniversityUniversity ParkPA16802USA

High-entropy diborides(HEBs)have attracted extensive research due to their potential ultra-high *** the present work,the effects of transition metals(TM)on lattice parameters,electron work function(EWF),bonding charge density,and hardness of HEBs are comprehensively investigated by the first-principles calculations,including(TiZrHfNbTa)B_(2),(TiZrHfNbMo)B_(2),(TiZrHfTaMo)B_(2),(TiZrNbTaMo)B_(2),and(TiHfNbTaMo)B_(2).It is revealed that the disordered TM atoms result in a severe local lattice distortion and the formation of weak *** view of bonding charge density,it is understood that the degree of electron contribution of TM atoms directly affects the bonding strength of the metallic layer,contributing to the optimized hardness of ***,the proposed power-law-scaled relationship integrating the EWF and the grain size yields an excellent agreement between our predicted results and those reported experimental *** is found that the HEBs exhibit relatively high hardness which is higher than those of single transition metal *** particular,the hardness of(TiZrNbTaMo)B_(2)and(TiHfNbTaMo)B_(2)can be as high as29.15 and 28.02 GPa,*** work provides a rapid strategy to discover/design advanced HEBs efficiently,supported by the coupling hardening mechanisms of solid solution and grain refinement based on the atomic and electronic interactions.

关键词： High-entropy diborides(HEBs) Hardness Electronic structure Lattice distortion Power-law

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Numerical Study on the Thermal Stress and its Formation Mechanism of a Thermoelectric Device

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Journal of Thermal science 2018年第3期27卷 249-258页

作者： PAN Tao GONG Tingrui YANG Wei WU Yongjia Product Engineering Department Wuhan Branch of SAIC-GM ltd Wuhan 430200 China Microsystem and Terahertz Research Center China Academy of Engineering Physics Chengdu 610200 China Institute of Electronic Engineering China Academy of Engineering Physics Mianyang 621999 China Hubei Institute of Aerospace Chemical Technology Xiangyang 441000 China School of Mechanical Engineering Virginia Polytechnic Institute and State University Blacksburg 24060 USA

The strong thermo-mechanical stress is one of the most critical failure mechanisms that affect the durability of thermoelectric devices. In this study, numerical simulations on the formation mechanism of the maximum thermal stress inside the thermoelectric device have been performed by using finite element method. The influences of the material properties and the thermal radiation on the thermal stress have been examined. The results indicate that the maximum thermal stress was located at the contact position between the two materials and occurred due to differential thermal expansions and displacement constraints of the materials. The difference in the calculated thermal stress value between the constant and the variable material properties was between 3% and 4%. At a heat flux of 1 W·cm^(-2) and an emissivity of 0.5, the influence of the radiation heat transfer on the thermal stress was only about 5%; however, when the heat flux was 20 W·cm^(-2) and the emissivity was 0.7, the influence of the radiation heat transfer was more than 30%.

关键词： Solar Thermoelectric Power Generator Thermal Stress Thermal Radiation Numerical Simulation

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Synergistic Effects of Gamma Irradiation,Tensile Stress and Moisture on the Radiolysis of Silicone Foam

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Chinese Journal of Polymer science 2023年第12期41卷 1969-1978,I0011页

作者： Pu-Cheng Wang Qiang Liu Bo Liu Wei Huang You An Jian-Yong Liu Hong-Bing Chen Institute of Nuclear Physics and Chemistry China Academy of Engineering PhysicsMianyang 621000China

The present work involves the investigation of the synergistic effects of gamma irradiation,tensile stress and absorbed moisture on the radiolysis behaviors of silicone foams by experiments and theoretical *** both the pristine and dehydrated samples,the permanent tensile set increases with the initial tensile *** analysis uncovers that the dehydrated samples exhibit greater permanent tensile sets,lower further elongation and higher Young’s modulus than the counterparts of the pristine samples with the same initial tensile strain and gamma dose,verifying the vital synergistic effects on crosslinking network and aggregation structures caused by moisture and gamma *** synergistic effects unveiled by reactive molecular dynamics at the atomic scale are due to the moisture-induced neutralization and stabilization of the macromolecular *** steric hindrance of moisture located at the interface of silica and polymer chains also conduces to the observed synergistic effects due to the inhibited crosslinking reactions.

关键词： Silicone foam Synergistic effect Gamma irradiation Tensile stress Moisture

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Effect of rotationally accelerated shot peening on the microstructure and mechanical behavior of a metastableβtitanium alloy

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Journal of Materials science & Technology 2021年第16期75卷 27-38页

作者： Xinkai Ma Zhuo Chen Dongling Zhong SNLuo Lei Xiao Wenjie Lu Shanglin Zhang Key Laboratory of Advanced Technologies of Materials(Ministry of Education) School of Materials Science and EngineeringSouthwest Jiaotong UniversityChengdu 610031China State Key Laboratory of Solidification Processing School of Materials Science and EngineeringNorthwestern Polytechnical UniversityXi'an 710072China National Key Laboratory of Reactor System Design Technology Nuclear Power Institute of ChinaChengdu 610041China

Microstructural evolution and deformation mechanism of a metastableβalloy(Ti-10 V-2 Fe-3 Al)processed by rotationally accelerated shot peening(RASP)were systematically investigated with optical microscopy,X-ray diffraction,electron backscatter diffraction and transmission electron *** gradient hierarchical microstructures(gradients inα″martensite andβphase,and hierarchical twins range from the nanoscale to microscale)can be fabricated by RASP via changing the shot peening *** hardening behavior and tensile mechanical properties of gradient hierarchical microstructure were systematically *** deformation twinning systems of{112}α″and{130}α″in the kinkedα″martensite were revealed during the tensile *** was found that stress-induced martensitic transformation,twinnedα″martensite and the related dynamic grain refinement contribute to hardness and work hardening *** improvement of strength and ductility of the metastableα″titanium alloy can be achieved by introducing a gradient hierarchical microstructure.

关键词： Titanium alloys Gradient hierarchical microstructure α″martensite Rotationally accelerated shot peening Mechanical behavior

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Epoxy-POSS/silicone rubber nanocomposites with excellent thermal stability and radiation resistance

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Chinese Chemical Letters 2022年第7期33卷 3534-3538页

作者： Mengni Shi Yinyong Ao Lei Yu Lang Sheng Shuangxiao Li Jing Peng Hongbing Chen Wei Huang Jiuqiang Li Maolin Zhai Beijing National Laboratory for Molecular sciences Radio Chemistry and Radiation Chemistry Key Laboratory of Fundamental ScienceThe Key Laboratory of Polymer Chemistry and Physics of the Ministry of EducationCollege of Chemistry and Molecular EngineeringPeking UniversityBeijing 100871China Institute of Nuclear Physics and Chemistry China Academy of Engineering PhysicsMianyang 621900China

Due to the rigid Si-O-Si backbone,silicone rubber(SR)have a widespread application in extreme environment such as high temperature and high-level ***,the radiation stability of SR still does not meet the practical needs in special radiation *** we prepared epoxy POSS(e POSS)/SR nanocomposites with excellent thermal stability and radiation *** a physical crosslinking point in the SR,addition of small amount of ePOSS not only enhanced the mechanical properties of the matrix,but also improved its thermal stability greatly due to their good compatibility.e POSS/SR had higher radiation stability in air than SR owing to the inhibition of radiation oxidation by ePOSS,and the yield of main gaseous radiolysis products(CH_(4),H_(2),CO and CO_(2))of SR and ePOSS/SR nanocomposites was *** analyzing the changes of chemical structure,thermal properties and mechanical properties of the ePOSS/SR nanocomposite,combined with the characteristics of gas products afterγ-irradiation,the radiation induced crosslinking and degradation mechanism of the nanocomposites was proposed comprehensively.

关键词： POSS Silicone rubber Thermal stability Radiation resistance Radiation crosslinking and degradation mechanism

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Experimental investigation and thermodynamic modeling of the U-Nb system

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Journal of Materials science & Technology 2021年第22期81卷 229-235页

作者： Chuan Mo Wenlin Mo Peng Zhou BaiXue Bian Yong Du Tao Fa Pengguo Zhang Ruiwen Li Yanzhi Zhang Changsheng Zhang Yuanhua Xia Xiaolin Wang Institute of Materials China Academy of Engineering PhysicsJiangyou 621907China Hunan Provincial Key Defense Laboratory of High Temperature Wear-Resisting Materials and Preparation Technology Hunan University of Science and TechnologyXiangtan 411201China State Key Laboratory of Powder Metallurgy Central South UniversityChangsha 410083China Key Laboratory for Neutron Physics of Chinese Academy of Engineering Physics Institute of Nuclear Physics and ChemistryMianyang 621999China China Academy of Engineering Physics Mianyang 621900China

The phase equilibria and thermodynamic properties of the U-Nb system were investigated through experiments and thermodynamic *** the experiments,a series of samples with different content of Nb were prepared by arc *** Nb content covers the entire composition range of the U-Nb binary *** solidification,the samples were annealed and then analyzed by X-ray diffraction,scanning electron microscopy,energy dispersive X-ray spectroscopy,differential scanning calorimeter and neutron *** equilibrium phases,including γ1(U-rich bcc),αU,and γ2(U-depleted bcc),were determined in detail from the experimental *** occurrence of the invariant reaction γ1→αU+γ2 was confirmed,and the reaction temperature and composition were accurately ***,the experimental findings clarify the dispute between the Dwight and Terekhov theories regarding the phase region(i.e.,whether the phase region is αU+γ1 or βU+γ2).Furthermore,the U-Nb phase diagram was reassessed by incorporating the present experimental data and previously published reliable experimental data from the literature.A set of self-consistent thermodynamic parameters were developed using CALPHAD(Calculation of phase diagrams),and the calculations reasonably agree with the experimental observations.

关键词： U-Nb alloy Monotectoid reaction Phase diagram Thermodynamic Modeling

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Recent Progresses in Experimental and Theoretical Studies of Actinide Clusters

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Chinese Journal of Structural Chemistry 2020年第7期39卷 1201-1212页

作者： HU Han-Shi XU Xiao-Cheng XU Cong-Qiao LI Jun Department of Chemistry and Key Laboratory of Organic Optoelectronics&Molecular Engineering of Ministry of Education Tsinghua UniversityBeijing 100084China Department of Chemistry Southern University of Science and TechnologyShenzhen 518055China

Actinide-containing cluster compounds are highly important in radio-and nuclear *** three decades ago,little attention had been paid to these heavy-element clusters because of difficulties in their syntheses and characterization as well as handling of these radioactive and chemotoxic *** this overview article we have selectively summarized the recent progresses in experimental and theoretical studies on actinide clusters,including actinide(An=Th,Pa,U,Np and Pu)oxide clusters as well as uranyl(UO22+)peroxide clusters and so *** shows that An(Ⅳ)(An=Th,U,Np and Pu)is able to form highly symmetric AnⅣ6O8 core clusters and further merge into larger clusters up to An38O56 clusters(An=U,Np and Pu)with the same ***,An with higher oxidation states such as U(Ⅵ)in uranyl is capable to form fullerene-like peroxide cage clusters of U20,U60 with the same topology as C20 and *** quantum chemistry investigations on the geometric structures,electronic structures and chemical bonding patterns have also been briefly summarized herein to provide an understanding on the structural chemistry of these peculiar *** advances in electronic structure studies of actinide clusters help to develop robust theoretical and computational techniques for the future development of actinide cluster *** experimental and computational studies of actinide clusters are needed and helpful to accelerate the development of radio-and nuclear chemistry.

关键词： actinide clusters uranyl compounds f-elements bonding of actinide compounds

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Anisotropy of nickel-based superalloy K418 fabricated by selective laser melting

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Progress in Natural science:Materials International 2018年第4期28卷 496-504页

作者： Zhen Chen Shenggui Chen Zhengying Wei Lijuan Zhang Pei Wei Bingheng Lu Shuzhe Zhang Yu Xiang State Key Laboratory of Manufacturing System Engineering Xi'an Jiaotong University Xi'an National Institute of Additive Manufacturing Co. Ltd. School of Mechanical Engineering Dongguan University of Technology School of Materials science and Engineering South China University of Technology

Selective laser melting(SLM) is a promising additive manufacturing(AM) technology for fabricating the near net-shaped parts by selectively melting and solidifying a thin powder layer with a high-intensity laser beam according to the CAD data for arbitrary components. In this work, Ni-based superalloy K418 samples were fabricated by selective laser melting(SLM). To evaluate the anisotropic mechanical behavior of the SLM processed K418 samples with layer-by-layer melting, the samples were manufactured parallel(transverse specimens) and vertical(longitudinal specimens) to the building direction on the substrate. The microstructural anisotropy analysis was performed by optical microscopy(OM) and scanning electron microscopy(SEM).Electron backscatter diffraction(EBSD) analysis was used to identify their crystallographic preferred orientation(texture) and to correlate the anisotropy of the mechanical strength with the texture of the material. The results showed that the transverse specimens had slightly higher yield strength, but much significantly higher ductility than that of the transverse specimens with the elongated columnar grains along the building direction.

关键词： Selective laser melting Ni-based Superalloy K418 Anisotropy Microstructure Mechanical behavior

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Design of near-α Ti alloys via a cluster formula approach and their high-temperature oxidation resistance

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Journal of Materials science & Technology 2019年第6期35卷 1008-1016页

作者： Beibei Jiang Donghui Wen Qing Wang Jinda Che Chuang Dong Peter K. Liaw Fen Xu Lixian Sun Key Laboratory of Materials Modification by Laser Ion and Electron Beams (Ministry of Education) School of Materials Science and Engineering Dalian University of Technology Dalian 116024 China Department of Materials science and Engineering The University of Tennessee Knoxville Tennessee 37996 USA Guangxi Key Laboratory of Information Materials Guangxi Collaborative Innovation Center of Structure and Property for New Energy and MaterialsSchool of Material Science and Engineering Guilin University of Electronic Technology Guilin 541004 China

The multi-component composition characteristics of high-temperature near-α Ti alloys were investigated in the present work by means of a cluster formula approach. The uniform cluster formula [CN12 cluster](glue atom)3 for the hexagonal close-packed α solid solution was first obtained based on the Friedel oscillation theory, with a total atom number in the formula of Z = 16. Then it was analyzed that the Z values in the cluster composition formulas of typical near-α Ti alloys are within the range of Z = 16.0016.30, being perfectly consistent with the ideal Z = 16. Based on it, a series of new alloys with Z = 16 and with Nb/Ta substitution for Mo in Ti1100 alloy were designed, suction-cast into φ 6 mm rods, and then heat-treated with solid solution and aging. It was found that the alloy with co-addition of Mo, Ta and Nb has a high strength and good ductility at both room and high temperatures. More importantly, the additions of Nb and Ta can contribute to the formation of continuous and compact Al2O3 scales, resulting in an obvious improvement of oxidation resistances at both 923 K and 1073 K. The effects of Mo, Ta and Nb on the oxidation behaviors of the designed alloys at 1073 K were further discussed.

关键词： Near-α Ti alloys Composition design Cluster formula approach Oxidation resistance Mechanical property

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Investigation into the improved axial compressibility of a spinning non-ideal gas

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Frontiers of physics 2020年第4期15卷 25-31页

作者： Yi-Wen Zhang Shi-Long Su Shu-Bin Xie Wei-Min Zhou Hao Liu Department of Applied Physics School of Physics and ElectronicsHunan UniversityChangsha 410082China science and Technology on Plasma Physics Laboratory Laser Fusion Research CenterChina Academy of Engineering PhysicsMianyang 621900China HEDPS Center for Applied Physics and TechnologyPeking UniversityBeijing 100086China

Using theoretical analysis and mumerical calculation method,the axial adiabatic compression of a spinning non-ideal gas in a cylinder with a smooth surface is *** show that the axial pressure of a spinning gas will gradually become lower than that of a stationary gas during continuous compression,even though the initial axial pressure of the spining gas is larger than that of the stationary gas at the same initial temperature and average *** phenomenon indicates that the axial compressibility of gas is improved in a rotating *** addition,the effect of different forms of virial coefficient B(T)on pressure and temperature changes in spinning and stationary gases are *** on the axial compressibility of spinning non ideal gas can provide useful references for fields that require high compression of gases,such as laser fusion,laboratory astrophysics,and Z-pinch experiments.

关键词： compressibility spinning system non ideal gas virial EOS

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