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first principle calculation of NbC Precipitation Competition between TiC Particle and Ferrite Matrix

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Journal of Wuhan University of Technology(Materials Science) 2018年第5期33卷 1076-1081页

作者：熊辉辉 ZHANG Henghua ZHANG Huining Gan Lei State Key Laboratory of Advanced Special Steel Shanghai Key Laboratory of Advanced Ferrometallurgy School of Materials Science and EngineeringShanghai UniversityShanghai 200072China School of Metallurgy and Chemical Engineering Jiangxi University of Science and TechnologyGanzhou 341000China

The electronic structure, cohesive energy and interfacial energy of ferrite（100）/NbC（100） and TiC（100）/NbC（100） interfaces have been investigated by the first-principles calculation. Moreover, the heterogeneous nuclei mechanism of NbC particle was also analyzed. The results showed that the stacking sequences have a great influence on the cohesive energy and equilibrium interfacial separation of the abovementioned interfaces. Compared with C-terminated interfaces, the cohesive energy of Nb-terminated ones is lower while the equilibrium interface distance is larger. Among the two C-terminated interface structures, the interfacial energy between the NbC and ferrite is 4.54 J/m^2, which is larger than that of NbC/TiC interface（1.80 J/m^2）. Therefore, NbC particles prefer heterogeneous nucleation on TiC particles surface rather than the ferrite matrix, which agrees well with the experimental result.

关键词： first-principle calculation interface energy cohesive energy precipitation

first-principle calculation Assisted Thermodynamic Assessment of the Au-Co-Sn Ternary System

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First-Principle Calculation Assisted Thermodynamic Assessmen...

Thermodynamic and thermoelectric properties of titanium oxycarbide with metal vacancy

第十四届全国相图会议暨国际相图与材料设计研讨会

作者： H.Q.Dong~1 X.M.Tao~1 L.G.Zhang~1 J.S.Wang~1 H.S.Liu~(1,2*) Z.P.Jin~(1,2) 1.School of Materials Science and Engineering,Central South University,ChangSha,HuNan Province,410083,P.R.China 2.Education Ministry Key lab of Materials Science and Engineering,Central South Univeristy,ChangSha,HuNan Province,410083,P.R.China

Phase diagram and thermodynamic information of Au-Co-Sn system are essential to predict the reactions between Au-Sn solder and Co (as the UBM material).In present work phase relationship in the Au-Co-Sn ternary system was thermodynamically optimized by CALPHAD method with the help of first-principle calculation.firstly,formation enthalpies of the intermetallic compounds including NiAs-type AuSn and CoSn,AuSn and AuSn were obtained through first-principle calculation. Secondly,the former thermodynamic descriptions of the Au-Sn and Co-Sn binary systems were slightly modified.Thirdly,the Au-Co binary system was reassessed and the solution phases including Liquid, Fcc and Hcp were modeled as substitutional solutions of which the excess Gibbs energies were formulated with a Redlich-Kister polynomial function.Finally,by taking into account of the ternary solubility in the related compounds and the ternary phase,a thermodynamic description of the Au-Co-Sn ternary system was carried out to reproduce the reported phase equilibria.Isothermal sections at 380℃(653K) and 396℃(669K),the CoSn-Au vertical sections along with liquidus projection of the ternary system were further calculated,which may be useful to the further study about the phase relations.

关键词： Au-Co-Sn system CALPHAD Thermodynamic Assessment first-principle calculation

来源： cnki会议评论

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International Journal of Minerals,Metallurgy and Materials 2022年第4期29卷 787-795页

作者： Bao Zhang Jiusan Xiao Shuqiang Jiao Hongmin Zhu State Key Laboratory of Advanced Metallurgy University of Science and Technology BeijingBeijing 100083China School of Materials Science and Engineering Beijing Institute of TechnologyBeijing 100081China Innovation Group of Marine Engineering Materials and Corrosion Control Southern Marine Science and Engineering Guangdong LaboratoryZhuhai 519080China Tohoku University Sendai 980-8579Japan

Normal titanium oxycarbide exhibits an excellent electrical conductivity and a high carrier concentration of approximately 10^(21) cm^(-3);however,the low Seebeck coefficient limits the thermoelectric application.In this study,first-principle calculations demonstrate that the metal vacancy of titanium oxycarbide weakens the density of state passing through the valence band at the Fermi level,impairing the carrier concentration and enhancing carrier mobility.Thermodynamic analysis justifies the formation of titanium oxycarbide with metal vacancy through solid-state reaction.Transmission electron microscopic images demonstrate the segregation of metal vacancy based on the observation of the defect-rich and single-crystal face-centered cubic regions.Metal vacancy triggers the formation of vacancy-rich and single-crystal face-centered cubic regions.The aggregation of metal vacancy leads to the formation of the vacancy-rich region and other regions with a semi-coherent interface,suppressing the carrier concentration from 1.71×10^(21) to 4.5×10^(20) cm^(-3) and resulting in the Seebeck coefficient from -11μV/K of TiC_(0.5)O_(0.5) to -64μV/K at 1073 K.Meanwhile,vacancies accelerate electron migration from 1.65 to 4.22 cm^(-2)·V^(-1)·s^(-1),maintaining high conductivity.The figure of merit(ZT)increases more than five orders of magnitude via the introduction of metal vacancy,with the maximum figure of 2.11×10^(-2) at 1073 K.These results indicate the potential thermoelectric application of metal-oxycarbide materials through vacancy engineering.

关键词： titanium oxycarbide metal vacancy thermoelectric first-principle calculation thermodynamics

Microstructure,mechanical properties and first-principle analysis of vacuum die-cast Mg-7Al alloy with Sn addition

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Rare Metals 2022年第6期41卷 1961-1967页

作者： Feng Wang Shi-Jie Sun Zhi Wang BoYu Ping-Li Mao Zheng Liu School of Materials Science and Engineering Shenyang University of TechnologyShenyang 110870China

The influences of Sn element and heat treat-ment on the microstructure and mechanical properties of Mg-7Al alloy prepared by vacuum die cast(VDC)were studied.The results indicate thatα-Mg dendrite and Mg_(17)Al_(12) are refined and new Mg_(2)Sn phase is formed in Mg-7Al alloy with 2 wt%Sn addition.The ultimate tensile strength(σ_(b))of Mg-7Al alloy increases from 205 to 258 MPa(i.e.,a 25%increase).The mechanical properties of Mg-7Al-2Sn(AT72)alloy are further improved through heat treatment because of the dense microstructures processed by VDC.In particular,the mechanical properties of AT72 alloy are greatly improved after solution treatment at 400℃for 20 h due to solution strengthening of Al and Sn elements and precipitation strengthening of Mg_(2)Sn phases.The precipitation strengthening effect of particle Mg_(2)Sn phases is more apparent due to the decomposition of Mg_(17)Al_(12) phases.In addition,from the view of microscopic theory,the effect of Sn on mechanical properties of Mg-7Al alloy was discussed by first-principle calculation.

关键词： Magnesium alloy Vacuum die castingi Heat treatment first-principle calculation

Greatly Enhanced Methanol Oxidation Reaction of CoPt Truncated Octahedral Nanoparticles by External Magnetic Fields

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Energy & Environmental Materials 2023年第5期6卷 201-210页

作者： Mengyuan Zhu Yi Wang Yanfei Wu Jialong Liu Jingyan Zhang He Huang Xinqi Zheng Jianxin Shen Ruijie Zhao Wenda Zhou Shouguo Wang Beijing Advanced Innovation Center for Materials Genome Engineering School of Materials Science and EngineeringUniversity of Science and Technology BeijingBeijing 100083China Department of Physics and Electronics School of Mathematics and PhysicsBeijing University of Chemical TechnologyBeijing 100029China

Tunable behavior in electrocatalysis by external multifields,such as magnetic field,thermal field,and electric field,is the most promising strategy to expand the theory,design,and synthesis of state-of-the-art catalysts and the cell in the near future.Here,a systematic investigation for the effect of external magnetic field and thermal field on methanol oxidation reactions(MOR)in magnetic nanoparticles is reported.For Co_(42)Pt_(58)truncated octahedral nanoparticles(TONPs),the catalytic performance in MOR is greatly increased to the maximum of 14.1%by applying a magnetic field up to 3000 Oe,and it shows a monotonical increase with increasing working temperature.The magnetic enhanced effect is closely related to the Co content of Co_(x)Pt_(100-x)TONPs.Furthermore,the enhancement effect under a magnetic field is more obvious for Co_(42)Pt_(58)TONPs annealed at 650℃.first-principle calculation points out that the magnetic fields can facilitate the dehydrogenation of both methanol and water by suppression of entropy of the electron spin and lowering of the activation barrier,where OH_(ad)intermediates on Co sites play a more important role.The application of magnetic fields together with thermal fields in MOR provides a new prospect to manipulate the performance of direct methanol fuel cells,which will accelerate their potential applications.

关键词： external magnetic fields first-principle calculation methanol oxidation reaction Pt-based magnetic nanomaterials

Microstructure,properties and first principles calculation of titanium alloy/steel by Nd: YAG laser self-fluxing welding

维普期刊数据库评论

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China Welding 2018年第3期27卷 1-10页

作者：张义福张华朱政强潘际銮 Key Laboratory for Robot & Welding Automation of Jiangxi Province School of Mechanical & Electrical EngineeringNanchang University School of Mechanics & Materials Engineering Jiujiang University

The experiment of Nd： YAG pulsed laser self-fluxing welding for 304 stainless steel/Ti6Al4V titanium alloy dissimilar metal was carried out. The microstructure properties of welded joint were analyzed by SEM, EDS and XRD. The equilibrium lattice constants, enthalpies of formation, cohesive energies, mechanical properties, Debye temperatures and valence electron structures of Ti-Fe intermetallic compounds （IMCs） were calculated by the first principle pseudopotential plane wave method based on density functional theory （DFT）. According to the thermodynamic data of Ti-Fe-Cr compounds, the Gibbs free energy per mole of compound at different temperatures was calculated and their thermal stability was compared. The results show that there are no macroscopic cracks in the welded joints, and the IMCs distributed evenly along the welding interface exhibits 3 distinct layers of microstructure with different colors. The welds interface generates IMCs of TiFe, TiFe 2 and a small amount of Ti 5Cr 7Fe 17 IMCs. Ti-Fe IMCs with high thermodynamic stability and easy alloying formation. The results of Gibbs free energies show that the sequence of precipitates in the interface is Ti 5Cr 7Fe 17 , TiFe 2 and TiFe in high temperature during the metallurgical reaction. The G/B values of Ti-Fe IMCs are greater than the critical value of 0.5, indicating that it is an intrinsic brittleness.

关键词： Nd：YAG pulsed laser self-fluxing welding titanium alloy stainless steel first-principle calculation

Pressure-induced stable structures and physical properties of Sr–Ge system

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Chinese Physics B 2023年第1期32卷 398-405页

作者：韩帅段帅刘云仙王超陈欣孙海瑞刘晓兵 Laboratory of High Pressure Physics and Material Science School of Physics and Physical EngineeringQufu Normal UniversityQufu 273165China Advanced Research Institute of Multidisciplinary Sciences Qufu Normal UniversityQufu 273165China

We have systematically investigated the structures of Sr-Ge system under pressures up to 200 GPa and found six stable stoichiometric structures,they being Sr_(3)Ge,Sr_(2)Ge,SrGe,SrGe_(2),SrGe_(3),and SrGe_(4).We demonstrate the interesting structure evolution behaviors in Sr-Ge system with the increase of germanium content,Ge atoms arranging into isolated anions in Sr_(3)Ge,chains in Sr_(2) Ge,square units in SrGe,trigonal units and hexahedrons in SrGe_(2),cages in SrGe_(3),hexagons and Geg rings in SrGe_(4).The structural diversity produces various manifestations of electronic structures,which is of benefit to electrical transportation.Among them,these novel phases with metallic structures show superconductivity(maximum T_(c)~8.94 K for Pmmn Sr_(3)Ge).Notably,the n-type semiconducting Pnma SrGe_(2) structure exhibits high Seebeck coefficient and excellent electrical conductivity along the y direction,leading to a high ZT value up to 1.55 at 500 K,which can be potential candidates as high-performance thermoelectrics.Our results will enable the development of fundamental science in condensed matter physics and potential applications in novel electronics or thermoelectric materials.

关键词： high pressure first-principle calculation germanium–strontium compounds superconductivity thermoelectric property

Electric field manipulation of multiple nonequivalent Dirac cones in the electronic structures of hexagonal CrB_4 sheet

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Chinese Physics B 2018年第9期27卷 518-523页

作者：王锦坤柯亚娇谢晴兴李艳丽王嘉赋 Department of Physics and Institute of Applied Condensed Matter Physics School of Science Wuhan University of Technology Hubei Engineering Research Center of RF-Microwave Technology and Application Wuhan University of Technology

Two-dimensional materials with Dirac cones have significant applications in photoelectric technology. The origin and manipulation of multiple Dirac cones need to be better understood. By first-principle calculations, we study the influence of external fields on the electronic structure of the hexagonal CrB4 sheet with double nonequivalent Dirac cones. Our results show that the two cones are not sensitive to tensile strain and out-of-plane electric field, but present obviously different behaviors under the in-plane external electric field（along the B-B direction）, i.e., one cone holds while the other vanishes with a gap opening. More interestingly, a new nonequivalent cone emerges under a proper in-plane electric field. We also discuss the origin of the cones in CrB4 sheet. Our study provides a new method on how to obtain Dirac cones by the external field manipulation, which may motivate potential applications in nanoelectronics.

关键词： borophene multiple Dirac cones electric field manipulation first-principle calculation

Fabrication of low-resistance LaNi_xO_(3+δ) thin films for ferroelectric device electrodes

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Journal of Rare Earths 2018年第8期36卷 838-843页

作者： Mi Xiao Zebin Zhang Weikang Zhang Ping Zhang Kuibo Lan School of Electrical and Information Engineering & Key Laboratory of Advanced Ceramics and Machining Technology of Ministry of Education Tianjin University

LaNiO3 thin films with different La/Ni ratios were deposited on Si substrates by sol-gel process. The electrical resistivities of LaNixO3＋δfilms with different La/Ni ratios were measured by four-probe method.LaNi（0.95）O3＋δthin film has the lowest resistivity. first-principle calculations show that LaNi（0.95）O3＋δhas the largest Ni-O-Ni bond angle and the shortest Ni-O bond length, which means LaNi（0.95）O3＋δhas the strongest metallic property, hence, the electrical resistivity is the lowest. Au/PZT（PbZr（0.52）Ti（0.48）O3）/LaNixO3＋δand Au/PZT/Pt ferroelectric capacitors were fabricated to evaluate LaNixO3＋δas a bottom electrode. It is shown that fatigue properties of PZT films can be significantly improved by using LaNixO3＋δinstead of Pt as the bottom electrode. The Ⅰ-Ⅴ test results of PZT films show that LaNi（0.95）O3＋δas bottom electrode can reduce the threshold voltages of PZT films, suggesting that La/Ni ratio in LaNixO3＋δas a large influence on the film properties.

关键词： LaNiO3 Thin film Sol-gel Electrical property first-principle calculation Rare earths