材料期刊网

INFLUENCE OF NANOMETER GRAIN SIZE OF Bi-2212 PHASE ON SUPERCONDUCTIVITY

ZHANG Cheng , WANG Yongzhong , JIANG Ming , ZENG Dechang , TANG Hong , LI Zhongrun , QIAO Guiwen , CHUANG Yuzhi(Institute of Metal Research , Chinese Academy of Sciences , Shenyang , ChinaManuscript received on 20 April 1995)

金属学报(英文版)

Bi-2212 superconductive oxides with nanometer grains have been prepared by means of crystallization from amorphous materials.The structure and grain-size of samples were examined by.X-ray.diffraction,scanning electron microscopy.and high resolution electron microscopy.The temperature dependence of the resistivity.and a.c.susceptibility was measured by the standard four-probe method and the standard mutual-induction measurement,respectively.With the decrease of temperature,the resistivity of the Bi-2212 phase with grain size in nanometer was found to diminish to zero without sudden drop.No diamagnetic transition was detected from room temperature to 4.2 K.The formation of the nanocrystalline 2212 phase and the effect of grain size on the superconductivity were discussed.

关键词: :Bi-2212 , null , null , null

Jian ZHANG/Langhong Lou

材料科学技术（英文）

关键词:

Ion sputter erosion in metallic glass-A response to "Comment on: Homogeneity of Zr(64.13)Cu(15.75)Ni(10.12)Al(10) bulk metallic glass" by L-Y. Chen, Y-W. Zeng, Q-P. Cao, B-J. Park, Y-M. Chen, K. Hono, U. Vainio, Z-L. Zhang, U. Kaiser, X-D. Wang, and J-Z Jiang J. Mater. Res. 24, 3116 (2009)

Journal of Materials Research

The morphology of the dark and bright regions observed by transmission electron microscopy for the Zr(64.13)Cu(15.75)Ni(10.12)Al(10) bulk metallic glass strongly depends on the ion beam parameters used for ion milling. This indicates that the ion beam could introduce surface fluctuation to metallic glasses during ion milling.

关键词: room-temperature

纳米复合薄膜特异电容机制探讨

程开甲 , 程漱玉 , 林东升 , 肖刚

稀有金属材料与工程

TFDC(Thomas-Fermi-Dirac-Cheng)electron theory用于分析讨论了纳米复合薄膜二极层中电子的特性.根据TFDC电子理论研究和实验测试提出了纳米复合薄膜二极层特异电容产生的机制.

关键词: TFDC电子理论 , 二极层 , 大电容 , 薄膜

论位错的稳定存在

程开甲 , 程漱玉

稀有金属材料与工程

阐述了Thomas-Fermi-Dirac-Cheng电子理论的位错形成机制. 通过对系统总能量的分析提出了位错能够存在的判据, 计算给出多种单质材料位错存在的极限尺寸值.

关键词: 位错 , Thomas-Fermi-Dirac-Cheng , 极限尺寸

论薄膜的超导电性

程开甲 , 程漱玉

稀有金属材料与工程

应用Cheng-Born能带对称破缺理论和TFDC(Thomas-Fermi-Dirac-Cheng)电子理论研究了薄膜层内电子的特性.对金属铂上的TiO2膜层来说,TFDC理论指出电子(或空穴)将由金属与膜的间界面一侧迁移到另一侧.根据Cheng-Born对称破缺理论,当能带中只有很少的电子时,则只有极少的角区中存在电子,动量空间即产生对称破缺,从而导致超导电性,并由热力学估算出薄膜超导体的转变温度.结果显示薄膜超导体的转变温度至少比块材超导体的转变温度高一个量级.作者还设计了一个研究薄膜超导电性的实验.

关键词: 超导电性 , 薄膜 , 对称破缺 , TFDC

论共晶结构的机理

程开甲 , 程漱玉

稀有金属材料与工程

本文是Thomas-Fermi-Dirac-Cheng电子理论对共晶机理的阐述.提出了薄膜两组元之间的化学势差和电子密度差导致系统总能量改变的新思想,给出了研究稳定共晶态的最佳尺寸和能量的方法.

关键词: Thomas-Fermi-Dirac , 共晶 , 内应力 , 化学势 , 电子密度

Broer-Kaup-Kupershmidt方程的新精确解

杨立娟 , 杨琼芬 , 杜先云

量子电子学报 doi:10.3969/j.issn.1007-5461.2012.02.003

CK方法是求解非线性发展方程的一种有效的直接方法.利用推广的CK方法,求得(2+1)维Broer-Kaup-Kupershmidt方程的Backlund公式,从而获得方程的大量新的精确解,推广了Xu和Zhang的结果.

关键词: 非线性发展方程 , Broer-Kaup-Kupershmidt方程 , 精确解 , CK方法 , Backlund变换

泡沫混凝土导热系数模型及参数修正

李翔宇 , 赵霄龙 , 郭向勇 , 曹力强

材料导报

在Cheng-Vachon模型的基础上提出了一种针对由连续相和分散相组成的两相复合材料的新导热系数模型.通过引入一个新的参数,即分散相的修正体积含量来改进Cheng-Vachon模型不适用于分散相体积含量较大的缺点.使用新的导热系数模型预测泡沫混凝土的导热系数,与实验结果的对比表明,新的模型可以准确预测泡沫混凝土的导热系数.

关键词: 泡沫混凝土 , 复合材料 , 导热系数 , 无机材料

Three-dimensional (3D) Ising universality in magnets and critical indices at fluid-fluid phase transition

Phase Transitions

Experimental data for critical exponents in some magnetic materials are compared with recent theoretical results on the three-dimensional (3D) Ising model, as derived by one of us (ZDZ) based on two conjectures [Z.D. Zhang, Conjectures on the exact solution of three-dimensional (3D) simple orthorhombic Ising lattices, Phil. Mag. 87 (2007), pp. 5309-5419]. It is found that critical exponents in some bulk magnetic materials indeed form a 3D Ising universality. Our attention is then focused on the critical indices at fluid-fluid phase transition. We suggest to use Zhang's exponent = 3/8 to fit the experimental data over the wider asymptotic region near the critical point of a fluid-fluid phase transition. The 3D Ising universality should exist for critical indices in a certain class of magnets and at fluid-fluid phase transition.

关键词: magnetically ordered materials;fluid-fluid;phase transitions;order-disorder effects;ferromagnetic curie temperature;liquid critical phenomena;x-ray-scattering;critical exponents;critical-point;coexistence;curves;binary-solutions;ionic-solutions;behavior;equation