材料期刊网

Kinetics and Nanostructure Dependence of High Temperature-Low Stress Creep of Al and Al-0.3%Fe

M. Abo-Elsoud

材料科学技术（英文）

The novel nanostructure of Al and Al{Fe were prepared by ball milling alumina with elemental Fe. The kinetics and nanostructure dependence of high temperature low stress Newtonian creep of Al and Al-0.3%Fe have been investigated and compared with the predications of the Nabarro{Herring (N-H) theory of directional diffusion. A simple theory based on the climb controlled generation of dislocations from a fixed density of sources is developed to explain the observed behavior. The dislocation density increases and subgrains form during the creep. Also, the presence of precipitates of FeAl₃ reduces the creep rate of Al by absolute faster of 100 at the same stress and temperature, in spite of the fact that the grain size in the Al-0.3%Fe alloy is smaller by a factor of about 100 nm. The reduction of grain size to the nanometer scale improves their mechanical properties. Electron diffraction methods combined with transmission electron microscopy (TEM) and scanning electron microscopy (SEM) studies are a convenient and powerful technique for the characterization of the phases and grain structure of the resulting materials.

关键词: Ball milling

ABO₃型钛铁矿结构化合物的容差因子

刘向春 , 高峰 , 邓军平 , 田长生

无机材料学报 doi:10.3724/SP.J.1077.2008.00881

通过结构解析, 建立了ABO₃型钛铁矿的容差因子计算公式以评估结构的稳定性, 经过分析具有钛铁矿结构的MgTiO₃、NiTiO₃、CoTiO₃、ZnTiO₃以及(Zn_1-x, M_x )TiO₃(M为Mg、Ni、Co)复合钛铁矿的稳定性, 验证了容差因子公式的合理性; 通过对已发现的具ABO₃型钛铁矿结构的化合物的统计分析, 提出形成稳定钛铁矿结构的经验容差因子范围和经验电负性差值, 即: t>0.80, e>1.465.

关键词: 钛铁矿 , stability , tolerance factor , electronegativity difference , structure

ABO3型钛铁矿结构化合物的容差因子

刘向春 , 高峰 , 邓军平 , 田长生

无机材料学报 doi:10.3321/j.issn:1000-324X.2008.05.004

通过结构解析,建立了ABO3型钛铁矿的容差因子计算公式以评估结构的稳定性,经过分析具有钛铁矿结构的MgTiO3、NiTiO3、CoTiO3、ZnTiO3以及(Zn1-x,Mx)TiO3(M为Mg、Ni、Co)复合钛铁矿的稳定性,验证了容差因子公式的合理性;通过对已发现的具ABO3型钛铁矿结构的化合物的统计分析,提出形成稳定钛铁矿结构的经验容差因子范围和经验电负性差值,即:t>0.80,e>1.465.

关键词: 钛铁矿 , 稳定性 , 容差因子 , 电负性差 , 结构

ABO3型氧化物的结构与性能及其应用

向勇 , 谢道华

材料工程 doi:10.3969/j.issn.1001-4381.2000.09.004

总结了ABO3型氧化物可能具有的各种晶体结构类型,以及由此产生的宏观电、光、声学性能.讨论了ABO3型功能晶体和具有ABO3型结构主晶相的功能陶瓷材料在现代电子信息、航空航天、国防军事等领域的应用与前景.

关键词: ABO3型氧化物 , 钙钛矿结构 , 功能材料

Structures of Fe3+-V-0 defects in ABO(3) perovskite-type crystals

Applied Magnetic Resonance

The displacements of Fe3+ ions and hence the structures of Fe3+-V-O defects in ABO(3) oxide perovskites are studied by analyzing their electron paramagnetic resonance data from the high-order perturbation formula of zero-field splitting on the basis of the spin-orbit coupling mechanism. The results suggest that the Fell ions in the Fell-V, defect centers are displaced away from the oxygen vacancy V-O by about 0.035 nm. The reasonableness of the displacement is discussed.

关键词: superposition model;impurities;resonance;spectrum;centers;knbo3

Theoretical studies on the gyromagnetic factors for Nd3+ in Scheelites-type ABO(4) compounds

Zeitschrift Fur Naturforschung Section a-a Journal of Physical Sciences

The gyromagnetic factors for Nd3+ in scheelite-type ABO(4) compounds (A = Cd, Ca, Ph, Ba; B = Mo, W) are theoretically studied by the perturbation formulas of the anisotropic g factors g(parallel to) and g(perpendicular to) for a 43 ion in tetragonal symmetry. In these formulas, the contributions to the g factors due to the second-order perturbation terms and the admixtures of various energy levels are taken into account. The relevant crystal-field parameters are determined by the superposition model and the local geometrical relationship of the A(2+) sites occupied by the impurity Nd3+. The obtained g factors agree reasonably with the observed values. The discrepancies between theory and experiment are discussed.

关键词: EPR;crystal-fields and Spin Hamiltonian;Nd3+;Scheelite-type ABO(4);compounds (A = Cd, Ca, Pb, Ba;B = Mo, W);stimulated raman-scattering;crystal-field;superposition-model;tungstate crystals;optical-properties;liyf4 crystal;spectra;parameters;cawo4;luminescence

Temperature-dependent fatigue behaviors of ferroelectric ABO(3)-type and layered perovskite oxide thin films

Applied Physics Letters

The temperature-dependent dielectric and ferroelectric fatigue behaviors of ABO(3)-type perovskite thin films Pb(Zr0.52Ti0.48)O-3 (PZT) and Pb0.75La0.25TiO3 (PLT) and layered Aurivillius thin films SrBi2Ta2O9 (SBT) and Bi3.25La0.75Ti3O12 (BLT) with Pt electrodes are studied. The improved fatigue resistance of PZT and PLT at a low temperature can be explained by the defect-induced suppression of domain switch/nucleation near the film/electrode interface, which requires a long-range diffusion of defects and charges. It is argued that the fatigue effect of SBT and BLT is attributed to the competition between domain-wall pinning and depinning. The perovskitelike slabs and/or (Bi2O2)(2+) layers act as barriers for long-range diffusion of defects and charges, resulting in localization of the defects and charges. Thus, the fatigued SBT and BLT can be easily rejuvenated by a high electric field over a wide temperature range. (C) 2004 American Institute of Physics.

关键词: srbi2ta2o9;deposition;capacitors;thickness;mechanism;interface

ABO3型锰基氧化物热敏感特性研究进展

申星梅 , 宋路路 , 李辽沙 , 武杏荣 , 王平

材料导报 doi:10.11896/j.issn.1005-023X.2014.17.022

在结合可变发射率几种机制的基础上,介绍了具有温控可变发射率的典型ABO3型锰基氧化物的热敏感特性研究进展.分别从AgO3型锰基氧化物的结构,包括其晶体结构、电子结构和磁结构,以及红外振动模式的角度分析了其对该氧化物红外发射率的影响;同时,阐述了该氧化物热敏感特性的国内外研究进展,并提出了该氧化物热敏感特性研究目前存在的问题与发展方向.

关键词: 锰基氧化物 , 热敏感 , 红外发射率 , ABO3 , 结构

KGW晶体1.067μm激光特性研究

邱闽旺 , 涂朝阳 , 李坚富 , 黄奕川 , 汪爱栋 , 唐鼎元 , 王元康

量子电子学报 doi:10.3969/j.issn.1007-5461.2001.04.012

本文报道了我所生长的掺钕钨酸钾钆(KGW)晶体的脉冲激光特性.当用氙闪光灯泵浦时,尺寸为φ3.4 mm×24 mm的KGW激光棒,最大激光输出为每个脉冲358.4mJ,总效率为1.7%,斜率效率为3.3%,波长为1.067μm.实验证明,KGW是一种很有前途的小型激光器工作物质.

关键词: 掺钕钨酸钾钆(KGW)晶体 , 1.067 μm激光

M型锶铁氧体中空纤维的制备和表征

宋福展 , 刘金勇 , 孟献丰 , 沈湘黔 , 向军

无机材料学报 doi:10.3724/SP.J.1077.2009.00721

以柠檬酸和金属盐为原料，采用有机凝胶先驱体转化法制备了M型锶铁氧体（SrFe₁₂O₁₉）中空纤维. 通过FTIR、TG/DSC、XRD、SEM和VSM等技术对所得纤维进行了表征. 结果表明，凝胶的可纺性与其化学组成和pH值有关，当柠檬酸与金属离子的摩尔比为1.5∶1.0，pH=4.2左右时，凝胶的可纺性最好. 经1100℃焙烧后，制备的M型锶铁氧体中空纤维具有较大的长径比，直径可小于1μm，中空孔径约为纤维直径的一半，组成纤维的晶粒形貌为六角片状，晶粒尺寸为236nm，在室温下的饱和磁化强度为53.5A·m²/kg，矫顽力为386.96kA/m. 纤维显示出一定的形状各向异性，当定向排列的纤维平行和垂直磁场时，矫顽力分别为391.66和358.72kA/m.

关键词: 有机凝胶先驱体转化法 , M-Sr ferrite , hollow fibers , spinnability , magnetic properties