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Analysis for twinning and slip in face-centered cubic crystals under axisymmetric co-deformation

science china(Technological sciences) 2006年第5期49卷 521-536页

作者： CHEN Zhiyong1,2. CAI Hongnian1, ZHANG Xinming2. WANG Fuchi1 & TAN Chengwen1,3.1. school of {3. {2. and engineering, Beijing Institute of Technology, Beijing 100081, china 2. school of material science and engineering, central south University, changsha 4.0083. china 3. school of {3. {2. and engineering, Beijing University of Aeronautics and Astronautics, Beijing 100083. china 1. school of material {2. and {3. Beijing Institute of Technology Beijing 100081 China 2. school of material science and engineering Central South University Changsha 410083 China 3. school of material {2. and {3. Beijing University of Aeronautics and Astronautics Beijing 100083 China

The maximum work principle of Bishop-Hill was developed to analyze the axisymmetric co-deformation in face-centered cubic crystals (f.c.c.) for twinning on {111} 112.and slip on {111} 110 systems. The influence of ξ , the ratio of critical re- solved shear stress for twinning to slip, on the yield stress states and corresponding active slip or/and twinning systems for orientations in the standard stereographic triangle of cubic crystal was investigated systematically. The Taylor factors and the anisotropy of yield strength for three important orientations [100], [110] and [111] in orientation space were analyzed. It is found that the yield strength asymmetry for the case of axisymmetric de- formation of tension and compression can be explained based on the microscopic theory of crystal plasticity. The concept of orientation factor for twinning ability was proposed and the deformation mechanism map in the orientation space was established for the case of axisymmetric deformation. The deformation texture formation and development of f.c.c. crystals with low stacking fault energy for axisymmetric tension can be explained qualita- tively on the basis of analyzed results.

关键词： twinning slip face-centered cubic crystals axisymmetric co-deformation Bishop-Hill maximum work principle yield strength anisotropy

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Characteristic atom arranging crystallogphy of alloy phases for Au-Cu system

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science china(Technological sciences) 2011年第6期54卷 1560-1567页

作者： XIE YouQing1,2.3.LIU XinBi1,2.3.PENG HongJian4,NIE YaoZhuang5,LI XiaoBo6 & LI YanFen1,2.3.1 {3. of materials {2. and engineering,central south University,changsha 4.0083.china 2.Powder Metallurgy Research Institute,central south University,changsha 4.0083.china 3.State Key Laboratory of Powder Metallurgy,central south University,changsha 4.0083.china 4 {3. of Chemistry and Chemical engineering,central south University,changsha 4.0083.china 5 {3. of Physical {2. and Technique,central south University,changsha,4.0083.china 6 College of Mechanical engineering,Xiangtan University,Xiangtan 411105,china 1. school of materials {2. and {3. Central South University Changsha 410083 China2. Powder Metallurgy Research Institute Central South University Changsha 410083 China3. State Key Laboratory of Powder Metallurgy Central South University Changsha 410083 China4. School of Chemistry and Chemical Engineering Central South University Changsha 410083 China5. School of Physical Science and Technique Central South University Changsha 410083 China6. College of Mechanical Engineering Xiangtan University Xiangtan 411105 China

In this paper,it is pointed out that the descriptions of alloy phase structures are dependent on structural unit *** the systematic science of alloys(SSA),the alloy phase structures are described by means of the symmetry element sequence combining with characteristic atom *** is named the characteristic atom arranging structure,which can display the characteristic atoms at the lattice sites and the micro-inhomogeneity,besides the *** characteristic atom has its own characters:neighboring configuration,potential energy,volume and electronic *** micro-inhomogeneity of alloy phases can be described by concentrations and short-range ordered parameters of characteristic *** differences between the electronic structures of alloy phases and electronic structures of characteristic atoms in the alloy phases are also discussed.

关键词： systematic science of alloys Au-Cu system alloy phase structure micro-inhomogeneity

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Electrochemical Characterization of Surface-modified LiMn_2._4 Cathode materials for Li-ion Batteries

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Journal of Wuhan University of Technology(materials science) 2006年第4期21卷 56-59页

作者：禹筱元 College of science South China Agricultural University Guangzhou 510642ChinaSchool of Physics & Engineering Sun Yat-sen University Guangzhou 510275China

To improve the performance, the surface of 12.n2.4 was coated with very fine MgO , Al2.3.and ZnO by solgel method, respectively. The structure and morphology of the coated {3.s were investigated by X-ray diffraction （ XRD ）, X-ray photoelectron spectroscopy （ XPS ） and scanning electron microscopy （SEM）. The charge and discharge performance of uncoated and surfnce modified 12.n2.4 spinel at 2.℃ and 55 ℃ were tested, using a voltage window of 3.0-4.3. V and a current deasity of 0. 1 C rate. There is a slight decrease in the initial discharge capacity relative to that of uncoated UMn2.O4, bat the cycle ability of 12.12.n2.4 coated by metal-oxide has remarkably been improved. The EIS measuremeuts of uncoated and Al2.3.-coated 12.n2.4 were carried out by a model 2.3.A potentiostatl galvanistat controUed by a computer using M2.0 software, and using a freqnency response analyzer （ Zsimpwin ） combined with a potentiostate （ PAR 2.3.. Coaseqnently, the reason for the improved cycle properties is that the surface modification reduces the dissolution of Mn , which results from the suppression of the electrolyte decomposition, and suppresses the formation of passivation film that acts as an electronic insulating layer. In conclusion, the use of surface modification is an effective way to improve the electrochemical performance of 12.n2.4 cathode {3. for lithium batteries.

关键词： lithium-ion batteries surface modification metal-oxide coating: 12.n2.4 cathode

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Relaxed resource advance reservation policy in grid computing

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The Journal of china Universities of Posts and Telecommunications 2009年第2期16卷 108-113页

作者： XIAO Peng HU Zhi-gang school of Information science and {2.,{3. south University,changsha 4.0083.china [a]school of Information science and {2. central south University changsha 4.0083 china

The advance reservation technique has been widely applied in many grid systems to provide end-to-end quality of service （QoS）. However, it will result in low resource utilization rate and high rejection rate when the reservation rate is high. To mitigate these negative effects brought about by advance reservation, a relaxed advance reservation policy is proposed, which allows accepting new reservation requests that overlap the existing reservations under certain conditions. Both the benefits and the risks of the proposed policy are presented theoretically. The experimental results show that the policy can achieve a higher resource utilization rate and lower rejection rate compared to the conventional reservation policy and backfilling technique. In addition, the policy shows better adaptation when the grid systems are in the presence of a high reservation rate.

关键词： grid computing advance reservation reservation violation computing economy

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Finite Element Analysis of Die Geometry and Process Conditions Effects on Equal Channel Angular Extrusion for β-Titanium Alloy

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Journal of Iron and Steel Research International 2012年第10期19卷 54-58页

作者： SI Jia-yong1,2. GAO Fan3. ZHANG Ji3.(1. State Key Laboratory of Powder Metallurgy, central south University, {2. 4.0083. Hunan, china 2. College of Mechanical and Electrical engineering, central south University of Forestry and Technology, {2. 410004, Hunan, china 3. High Temperature material Research Division, central Iron and Steel Research Institute, Beijing 100081, china) [a] State Key Laboratory of Powder Metallurgy Central South University Changsha 410083 Hunan China [b] College of Mechanical and Electrical engineering Central South University of Forestry and Technology Changsha 410004 Hunan China [c] High Temperature material Research Division Central Iron and Steel Research Institute Beijing 100081 China

The finite element analysis was applied to evaluate the respective influences of die geometry and process conditions on plastic strain distribution for β-titanium (Ti-13.11Cr3.l) alloy during the equal channel angular extrusion (ECAE). It was found that optimum equal channel angular extrusion die geometry is strongly material dependent. Optimal strain homogeneity in the Ti-13.11Cr3.l alloy may be achieved at r (inner radius)=5 mm, R (outer radius)=3.mm. The equivalent plastic strain increases with increasing friction coefficient. And the better homogeneity of the equivalent plastic strain distribution can be achieved when friction coefficient value is lower. The faster the ram speed is, the lower the homogeneity of the equivalent plastic strain distribution is and the influence is slight. The back-pressure does not help to improve the plastic strain homogeneity, and the increasing temperature has a slightly favourable effect on the plastic strain homogeneity between 400 and 600 ℃.

关键词： equal channel angular extrusion finite element analysis die geometry β-titanium

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Effect of aluminum-containing additives on the reactivity in air and CO_2.of carbon anode for aluminum electrolysis

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Rare Metals 2004年第2期23卷 109-114页

作者： LAI Yanqing LI Jie LI Qingyu DING Fengqi school of Metalling science and {2., {3. south University, changsha 4.0083. china school of Metallurgy science and {2. Central South University Changsha 410083 China

Airburn reaction and carboxy reaction result in the excess consumption ofcarbon anode in aluminum electrolysis. To reduce the excess carbon consumption, carbon anode wasdoped with aluminum-containing additives, such as Al, Al_4C_3. AlF_3.and Al_2._3. Their reactivityin air and CO_2.was determined with an isothermal-gravimetric method to study the effect ofaluminum-containing additives on the reactivity in air and CO_2.of carbon anode. Results shown thatthe airburn reactivity at 450℃ and carboxy reactivity at 970℃ of carbon anode both decreased withAl-containing additives adding, while shown a minimum with the amount of Al_4C_3. AlF_3.and Al_2._3.ncreasing. However, all Al-containing additives increase the airburn reactivity at 550℃ of carbonanodes. Coke yield measurement and XRD examination with aluminum containing additives doped pitchcokes revealed that the effect of Al-containing additives on the airburn reactivity and carboxyreactivity of carbon anode would result from chemical factors and structural factors.

关键词： aluminum electrolysis aluminum-containing additives reactivity carbonanode

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Boron rings containing planar octa- and enneacoordinate cobalt, iron and nickel metal elements

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science china Chemistry 2008年第7期51卷 607-613页

作者： LUO Qiong school of Chemistry and Chemical engineering, {2. {3. University, changsha 4.0083. china school of Chemistry and Chemical engineering Central South UniversityChangsha 410083China

For a series of boron rings with planar hyper-coordinate 8th group transition metal atoms, singlet 1FeB8-2. multiplet kFeB9n (n = -1, k = 1; n = 0, k = 2., singlet 1CoB8n(n = -1, +1, +3., multiplet kCoB9n (n = +1, k = 2. n = 0, k = 1) and singlet 1NiB9+, the geometry structures have been optimized to be local minima on corresponding potential hyper-surfaces. The electron structures are discussed by orbital analysis and the aromaticity is predicted by nucleus-independent chemical shifts calculation at both the B3.YP/6-3.1+G* and BP86/6-3.1+G* levels of theory, respectively. The results suggest that all these structures with high symmetry planar geometries are stable and have aromatic properties with six π valence electrons.

关键词： planar hyper-coordinate transition metal DFT

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Effect of Nd_2.e_(14)B/α-Fe Nanocomposite Permanent Magnets with a Combined Co and Nb Additions

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Journal of Wuhan University of Technology(materials science) 2009年第5期24卷 725-727页

作者：马瑞 school of materials {2. and Metallurgy {3. Guizhou University

Influence of Co＋Nb on the Nd8Fe82.o3.b1B6 nanocomposite magnets was investigated by adding Co element combined with Nb element. Results show that the high temperature stability of two phases is increased. Adding Co＋Nb could improve the glass forming ability of the alloy, reduce the size of grains, increase the exchange coupling ability of two phases, and obviously increase the magnetic properties of the alloy. The optimal magnetic properties are Br=1.14 T, Hcj=3.0} kA/m, （BH）max=109.3.kJ/m^3

关键词： nanocomposite permanent magnets glass forming ability exchange coupling ability magnetic properties

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Controllable synthesis of Ni-catalyzed tetragonal tungsten nanowires via chemical vapor deposition

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Progress in Natural science:materials International 2012年第5期22卷 514-519页

作者： Chao Wang a,Yuehui He a,Chaoqun Peng b,Shiliang Wang a,c,Xinli Liu a a State Key Laboratory of Powder Metallurgy,central south University,{2. {3.china b school of material science and engineering,central south University,{2. {3.china c school of Physics science and Technology,central south University,{2. {3.china [a] State Key Laboratory of Powder Metallurgy Central South University Changsha 410083 China [b] school of material {2. and {3. Central South University Changsha 410083 China [c] school of Physics science and Technology Central South University Changsha 410083 China

Tetragonal single-crystal tungsten nanowires were successfully synthesized by chemical vapor deposition(CVD) catalyzed by Ni *** influences of the catalysts,temperature and growth time on the formation of the nanowires were *** was found that the tetragonal tungsten nanowires(WNWs) arrays were obtained by deterministic growth from the ordered Ni catalyst particles with one-to-one relation in size and position between the catalysts and *** large-scale tungsten nanowire arrays were synthesized at the low temperature of 950℃.Samples were characterized by X-ray diffraction(XRD),field-emission scanning electron microscopy(FE-SEM),transmission electron microscopy(TEM) and high-resolution transmission electron microscopy(HRTEM).Increasing growth time at 950℃,the tip of the WNWs changed from four(2.1) planes to four(110) *** controls of the orientation and structure of WNWs arrays were important for adjusting their properties to satisfy different requirements of potential nanodevices.

关键词： Tungsten nanowires Ni catalysts Chemical vapor deposition Nanostructures

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Mass Concentration of Particles (PM10) in Urban Environment of changsha,china

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湖南大学学报（自然科学版） 2009年第S1期36卷 5-9页

作者： TANG Meng,DENG Qi-hong,WANG Qi(school of Energy science & {2.,{3. south University,changsha,Hunan 4.0083.china) school of Energy science and {2. Central South University Changsha 410083 China

Continuous measurement of ambient PM10 was performed by TEOM at a university campus for about one year from 2. November 2.07 to 2. October 2.08 in changsha city of Hunan *** PM10 and PM2.5 concentration were measured by DustTrak simultaneously in order to describe the difference in concentration level and daily variations of particle mass concentration between different seasons,and to survey the influence of ambient particle on indoor air *** the survey period,the annual average PM10 concentration was found to be 117.63.μg/m3.with a mean value 12..88 μg/m3.in winter and 111.50 μg/m3.in *** temporal trend changed quickly from time to time,and the peak values were found in rush hours and in the *** PM10 showed a good correlation with indoor PM10 and outdoor PM2.5 but not with indoor *** results showed that PM10 was influenced by local source(such as traffic or fuel burning)and regional *** correlation analysis has shown that ambient PM10 contributes substantial fraction to indoor PM10 but not to indoor PM2.5,which indicates other source may exist in the indoor environment.

关键词： particle mass concentration human activity relationship

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