材料期刊网

Investigation of Instability of Lattice of Bi_2Sr_2CaCu_2O_x

Han ZHANG and Qingrong FENG (Dept. of Physics , Peking University , Beijing 100871 , China)Y.Zhao(School of Materials Science and Engineering , University of New South Wales , Sydney 2052 , NSW , Australia)F.Ritter and W.Assmus (Physikalisches Institut , J.W.Goet

材料科学技术（英文）

Bi2Sr2CaCu2Ox superconductor was studied by differential scanning calorimetry (DSC) and thermogravimetry (TG) in different atmospheres. It is discovered that there is a thermal anomaly in the DSC curve, associated with a weight loss in the TG curve before the melting of the sample. Careful thermal analysis and high temperature X-ray diffraction reveal that the thermal anomaly and the weight loss show an instability of the crystalline Iattice. By annealing the sample in oxygen and argon, respectively and then by TC measurement and thermal analysis, the coincidence of transition temperature with the instability is found. The coincidence is further confirmed by Y-doped 2212 phase.

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含有Stone-Wales缺陷的碳纳米管的热导率模拟

彭佳 , 冯妍卉 , 李威 , 张欣欣

工程热物理学报

本文以Stone-Wales(SW)缺陷对碳纳米管热导率的影响为研究内容,采用非平衡态分子动力方法,模拟计算存在一个或多个SW缺陷的碳纳米管的轴向温度分布和热导率,并与无缺陷完整碳纳米管进行比较,开展缺陷效应分析,考察了缺陷浓度、碳管长度、碳管手性以及环境温度等因素的影响.模拟结果表明,由于缺陷存在,碳管轴向温度分布在缺陷处产生非线性的间断性跳跃,局部热阻增大.相对完整无缺陷碳管,含有SW缺陷的碳管热导率显著下降;随着缺陷数目的增加,碳管热导率下降的幅度增大.无论是否存在缺陷,锯齿型碳管的热导率通常小于扶手椅型的碳管,而长碳管的热导率通常大于短碳管;相对于锯齿型/长碳管,扶手椅型碳管/短碳管对SW缺陷更为敏感.

关键词: 碳纳米管 , 热导率 , Stone-Wales缺陷 , 分子动力学 , 缺陷效应

A NEW MOLYBDENUM OXIDE PHASE

FANG Zheng ZHANG Pingmin CHEN Xinmin Central-South University of Technology , Changsha , China FANG Zheng , Associate Professor , Dept.of Chemistry , Central South University of Technology , Changsha 410083 , China

金属学报(英文版)

A new molybdenum oxide phase which exists in bomb combustion products of Mo was found. It has been determined that this phase is a transformed MoO_3 of triclinic system.One set of its lattice parameters was also determined from the X-ray diffraction data as α=0.4049± 0.0001 nm,b=0.5079±0.0003 nm,c=1.4339±0.0009 nm,α=115.16±0.08°,β=90.69± 0.14°,γ=105.58±0.05° and unit cell volume=0.2544 nm~3.

关键词: Mo oxide , null , null

A NEW MORPHOLOGY OF MARTENSITE

ZHONG Jiaxiang QI Yan Beijing Institute of Technology , Beijing , ChinaZHANG Xiumu GUO Yunyi Institute of Metal Research , Academia Sinica , Shenyang , China Beijing Institute of Technology , Beijing 100081 , China

金属学报(英文版)

A new “mid-relief” plate martensite was observed together with lenticular plate and thin plate martensites in Fe-29.37Ni-0.34C alloy after twice stepped cooling:-100/-120℃, -120/-140℃,-155/-165℃ and -165/-196℃,by means of colour metallography and TEM.The morphology of martensites changes with decreasing M_s temperature.The “mid-relief” plate martensite is characterized by the intensive mid-relie and the substructures of symmetric double twins or half twins and half dislocations,the formation of this martensite can be interpreted by a stress-induced co-generated mechanism.

关键词: martensite , null , null

A NEW KOSSEL ORIENTATION METHOD OF CRYSTAL

HUANG Rong WANG Guanying Shanghai Institute of Metallurgy , Academia Sinica , Shanghai , China HUANG Rong Shanghai Institute of Metallurgy , Academia Sinica , Shanghai , China

金属学报(英文版)

A new Kossel orientation method of crystal is developed.Only the distances among three in- tersections of the Kossel lines on the indexed Kossel patterns observed are necessary.for de- termining the orientation.Thus,the error may be eliminated and the orientation precision may be improved to be within 0.3°.

关键词: Kossel orientation method

University of Science and Technology Beijing

JIA Shizhen University of Science and Technology Beijing , China.

材料科学技术（英文）

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A NEW METHOD FOR SYNTHESIZING NANOCRYSTALLINE ALLOYS

Journal of Applied Physics

A new method to prepare nanocrystalline alloys was developed by means of crystallization from amorphous alloys. By using this method, a Ni-P alloy with 9 nm crystallites was synthesized. The structure and grain sizes of the alloy were examined by means of x-ray diffraction, transmission electron microscopy, and high resolution electron microscopy. Specific heat capacity and thermal expansion coefficient of the nanocrystalline Ni-P alloy prepared by this method were found to be greater than those of the coarse-grained crystalline alloy by 12.3% and 56.2%, respectively. A new micromechanism for nanometer-sized crystallites formation is discussed.

关键词: sized crystalline materials

A NEW EVALUATION PROCEDURE FOR CRACK CLOSURE

International Journal of Fatigue

Bending fatigue tests can be used as a simple method for the determination of load-displacement curves near threshold for specimens containing surface cracks. The test method involves a strain gauge technique that yields highly reproducible results for cyclic loading from positive to negative stress ratios. Applying a new evaluation procedure one obtains DELTA-K(th,eff) values that are considered to be more realistic compared with those determined by conventional methods.

关键词: crack closure;bending tests;load-displacement curves;strain gauges;displacement gauge;fatigue;propagation

A new probe for the investigation of soil corrosivity

Corrosion

A new type of soil corrosivity probe was developed that could be used to measure not only corrosion current density (i(corr)) and corrosion potential (E-corr) of metals in soil, but also parameters of soil such as resistivity (rho), redox potential (Eh(7)), and temperature in a field corrosion test. The stable i(corr) of low-carbon steel (LCS) measured by the probe was in satisfactory agreement with the weight loss in practice. Results showed that the probe could provide a valuable tool for measuring soil corrosivity.

关键词: low-carbon steel;corrosivity;electrochemical impedance spectroscopy;electrochemical probe;soils

Mechanical properties of a new electrorheological fluid

Solid State Communications

We have extended the Rayleigh identity based on a multipole expansion theory to analyze the mechanical properties of a new type of electrorheological (ER) system that consists of a novel doubly coated particle in silicone oil. The function of the inner conducting layer of the particle has been investigated. From the shear strain (theta) dependence of effective dielectric constant, the dependence of static yield stress (tau(s)) and shear modulus (G) on the applied electric field are presented. Implications for the design of ER fluids are discussed briefly. (C) 2000 Elsevier Science Ltd. All rights reserved.

关键词: electrorheological fluids;effective dielectric constant;static yield;stress;shear modulus;conductivity;spheres;forces