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A STUDy OF TEMPERATURE-DEPENDENT VALENCE BOND STRUCTURE OF TITANIUM

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Acta Metallurgica Sinica(English Letters) 2007年第1期20卷 27-34页

作者： X.B. Li y.Q. Xie y.z. nie H.J. Peng H.J. Tao F.X. yu College of Materials Science and Engineering Central South University Changsha 410083 China

On the basis of energy and shape method for the determination of the valence bond （ VB ） structures of crystal, the valence bond structure of titanium is redetermined at room temperature and calculated in the whole temperature range of 0-1943K. The outer shell electronic distribution of Ti is ec^29907. （sc^0.4980 ＋ dc^2.4927） ef^1.0098 in crystal. The temperature dependences of the VB structures of hcp and bcc phases are the same. The VB structures of hcp and bcc phases monotonically increase or decrease with the increase in temperature, but show discontinuous changes at the phase-transformation temperature 1155K.

关键词： valence bond structure temperature titanium

Surface modification of tungsten oxide by oxygen vacancies for hydrogen adsorption

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Journal of Materials Science & Technology 2022年第22期117卷 23-35页

作者： Q.zhang F.W.Tang z.zhao z.R.nie X.y.Song Faculty of Materials and Manufacturing Key Laboratory of Advanced Functional MaterialsMinistry of Education of ChinaBeijing University of TechnologyBeijing 100124China

A model for describing the adsorption process of hydrogen on surface of tungsten oxide was proposed based on the first-principle calculations. Multiple factors such as type of active surface, adsorption site and distribution of oxygen vacancies were considered to evaluate the hydrogen adsorption capability of tungsten oxide. The adsorption Gibbs free energies, electronic structures and bonding characteristics under various conditions were examined to reveal the influence of oxygen vacancies on the surface. It is found that the capability of hydrogen adsorption of tungsten oxide can be significantly enhanced by adjusting the oxygen vacancy on the outermost layer of certain active surfaces. The modeling predicts that the surface structure stability and gas adsorption ability of tungsten oxide can be simultaneously improved through the formation of W–H bonds. The proposed strategy for moderating surface provides a new approach to obtain excellent gas-sensitive metal oxide materials.

关键词： Metal oxide Gas-sensitive material Surface adsorption Oxygen vacancy First-principles calculation

Nanocrystalline Ti49.2Ni50.8 shape memory alloy as orthopaedic implant material with better performance

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Journal of Materials Science & Technology 2019年第10期35卷 2156-2162页

作者： H.F.Li F.L.nie y.F.zheng y.Cheng S.C.Wei R.z.Valiev Department of Materials Science and Engineering College of EngineeringPeking UniversityBeijing 700877China Center for Biomedical Materials and Tissue Engineering Academy for Advanced Interdisciplinary StudiesPeking UniversityBeijing 100871China Department of Oral and Maxillofacial Surgery School of StomatologyPeking UniversityBeijing 100081China Institute of Physics of Advanced Materials Ufa State Aviation Technical UniversityUfaRussia Saint Petersburg State University Universitetskiy prospekt 28PeterhofSt.Petersburg198504Russia

Ti Ni alloys, with their unique shape memory effects and super elastic properties, occupy an indispensable place in the family of metallic biomaterials. In the past years, surface treatment is the main technique to improve the bioinert nature of microcrystalline Ti Ni alloys and inhibit on the release of toxic nickel ions to obtain excellent osteogenesis and osseointegration function. In the present study, nanocrystalline Ti49.2Ni50.8 alloy has been fabricated via equal channel angular pressing(ECAP), and the in vitro and in vivo studies revealed that it had enhanced cell viability, adhesion, proliferation, ALP(Alkaline phosphatase)activity and mineralization, and increased periphery thickness of new bone, in comparison to the commercial coarse-grained counterpart. These findings indicate that the reduction of grain size is beneficial to increasing the biocompatibility of Ti49.2Ni50.8 shape memory alloy.

关键词： Nanocrystallines Shape memory alloys Metallic biomaterials Orthopaedic implants TiNi alloys

Effect of extrusion temperature on microstructure and mechanical properties of a low-alloying and ultra-high strength Mg-zn-Ca-Mn matrix composite containing trace TiC nanoparticles

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Journal of Magnesium and Alloys 2020年第3期8卷 676-691页

作者： K.B.nie z.H.zhu K.K.Deng J.G.Han College of Materials Science and Engineering Taiyuan University of TechnologyTaiyuan 030024PR China Sharvci key laboratory of advanced magnesium-based materials Taiyuan University of TechnologyTaiyuan 030024PR China

Mechanical properties of microalloying Mg-2.2zn-1.8Ca-0.5Mn(wt%)matrix composites reinforced by 0.5 wt%TiC nanoparticles before and after extrusion were investigated based on the detailed microstructural analysis.A uniform distribution of TiC nanoparticles was realized in the nanocomposite by the method of ultrasonic-assisted semisolid *** morphology of eutectic Ca2Mg6zn3 phases changed from plate-like in the free TiC nanoparticles region to lamellar in the dense TiC nanoparticles region for the as-cast *** the grain structure and precipitates were obviously refined as the extrusion temperature decreased from 350 to 270℃.The nanocomposite exhibited excellent tensile yield strength(352-428 MPa)which was governed by the extrusion *** grain refinement strengthening with the contribution ratio of^80%to this strength increment was much higher relative to thermal expansion effect,Orowan strengthening and dislocation *** recrystallized grain structure with a substantial of ne precipitates appeared in the nanocomposite extruded at 270℃.The refined grain structure was not only due to dynamic recrystallization,but also the synergistic pinning effect of nano-TiCp,precipitated Mgzn2 and α-Mn *** tensile toughness value of nanocomposite after extrusion improved with increasing the extrusion *** micro-cracks formed along the remnant coarse Ca2Mg6zn3 led to the structural failure during tension.

关键词： Magnesium matrix nanocomposite Microstructure Mechanical properties:Strengthening mechanism Extrusion

Blaschke Isoparametric Hypersurfaces in the Conformal Space Q_1^(n+1),Ⅰ

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Acta Mathematica Sinica,English Series 2015年第11期31卷 1751-1758页

作者： Chang Xiong nie Faculty of Mathematics and Statistics Hubei University

Let x ：M - Qn＋l be a regular hypersurface in the conformal space Qn＋I. We classify all the space-like Blaschke isoparametric hypersurfaces with two distinct Blaschke eigenvalues in the conformal space up to the con... 详细信息

关键词： Regular hypersurfaces conformal invariants Blaschke isoparametric Lorentzian spaceforms

Special Column on Shear Failure Test and Analysis of Concrete Structures

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Frontiers of Structural and Civil Engineering 2014年第4期8卷 323-324页

作者： y. L. MO J. G. nie V. SIGRIST z. SUN University of Houston USA Tsinghua University China Hamburg University of Technology (TUHH) Germany Research Fellow Tongji University China

Shear resistance capacity analysis is a traditional bottleneck problem for the analysis and design of reinforced concrete structures. Along with the use of high performance materials and the geometrical layout optimization of concrete, rebars and other additives, the performance of reinforced concrete components and structures are continuously improved. The testing, modelling and analyzing research works are continuously conducted for the accurate computation and conservative design of the improved concrete components and structures.

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Highly sensitive tuning of lattice thermal conductivity of graphenelike borophene by fluorination and chlorination

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Nano Research 2020年第4期13卷 1171-1177页

作者： Tingwei Li Ge nie Qiang Sun Department of Materials Science and Engineering Peking UniversityBeijing 100871China State Key Laboratory of Coal-based Low Carbon Energy ENN Science&Development Co.Ltd.Langfang 065001China Center for Applied Physics and Technology Peking UniversityBeijing 100871China

Boron-based 2D materials are of current ***,graphene-like geometry is unstable for B due to the electron deficiency,which can be stabilized by introducing H,F and ***,using density functional theory combined with phonon Boltzmann transport equation,we perform systematic studies on how the functionalization changes the lattice thermal conductivity(LTC).We find that when going from hydrogenation to fluorination and chlorination,the LTC along zigzag direction changes from 367.6 to 211.3 and 43.0 W/(rrvK),while the corresponding values in armchair direction are 279.6,198.9,and 41.6 W/(m·K),*** huge differences imply the sensitivity of LTC to functionalization,which can be attributed to the enhanced anharmonicity as revealed by analyzing group velocity,Gruneisen parameter,anharmonic scattering rates,and three-phonon scattering space.

关键词： graphene-like borophene lattice thermal conductivity fluorination chlorination calculation

The effect of pre-existing memory representations on repetitionrelated N250r and N400

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Science Bulletin 2016年第4期61卷 265-275页

作者： Aiqing nie Jingheng ye Minye Li Department of Psychology and Behavior Science Zhejiang University

Studies of repetition priming have found two face-sensitive event-related potential(ERP) components:the N250 r showing positive deflection at frontal region and negative deflection at temporal region, and the N400 showing positive deflection at frontal and centro-parietal regions, both of which depend in part upon the presence or absence of a pre-existing face representation. However, the N250 r is rarely reported for a repetition interval between immediate repetition and 3 min; in addition, whether different types of representations function in the same way is also of interest. The goal of the present experiment is to compare the ERP patterns for faces versus letter strings as a function of the pre-existing memory representation with a repetition interval of 1.5 min on average. We found reliable frontally positive N250 r and N400 for famous faces and words; marginally significant effects for pseudo-words;and only the centro-parietal N400 for unfamiliar ***, the N250 r persists in the present intermediate intervals, and both the frontal N250 r and the frontal N400 are domain-general, sensitive to the pre-existing memory representation.

关键词： Repetition priming - Pre-existingmemory representation - Face - Letter string - N250rN400

Flat-band ferromagnetism of SU(N) Hubbard model on Tasaki lattices

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Science Bulletin 2019年第20期64卷 1490-1495页

作者： Ruijin Liu Wenxing nie Wei zhang Department of Physics Renmin University of ChinaBeijing100872China Center for Theoretical Physics College of PhysicsSichuan UniversityChengdu610064China Beijing Key Laboratory of Opto-electronic Functional Materials and Micro-nano Devices Renmin University of ChinaBeijing100872China

We investigate the para-ferro magnetic transition of the repulsive SU(N) Hubbard model on a type of oneand two-dimensional decorated cubic lattices, referred as Tasaki lattices, which feature massive singleparticle ground state degeneracy. Under certain restrictions for constructing localized many-particle ground states of flat-band ferromagnetism, the quantum model of strongly correlated electrons is mapped to a classical statistical geometric site-percolation problem, where the nontrivial weights of different configurations must be considered. We prove rigorously the existence of para-ferro transition for the SU(N) Hubbard model on one-dimensional Tasaki lattice and determine the critical density by the transfer-matrix method. In two dimensions, we numerically investigate the phase transition of SU(3),SU(4) and SU(10) Hubbard models by Metropolis Monte Carlo simulation. We find that the critical density exceeds that of standard percolation, and increases with spin degrees of freedom, implying that the effective repulsive interaction becomes stronger for larger N. We further rigorously prove the existence of flat-band ferromagnetism of the SUeNT Hubbard model when the number of particles equals to the degeneracy of the lowest band in the single-particle energy spectrum.

关键词： SU(N) Flat-band ferromagnetism Percolation Para-ferro transition