材料期刊网

COMPARISON OF FATIGUE AND CREEP BEHAVIOR BETWEEN 2D AND 3D-C／SiC COMPOSITES

D.Han , S.R.Qiao , M.Li , J.T.Hou , X.J.Wu

金属学报(英文版)

The differences of tension-tension fatigue and tensile creep characters of 2D-C/SiC and 3D-C/SiC composites have been scrutinized to meet the engineering needs. Experiments of tension-tension fatigue and tensile creep are carried out under vacuum high temperature condition. All of the high temperature fatigue curves are flat; the fatigue curves of the 2D-C/SiC are flatter and even parallel to the horizontal axis. While the tension-tension fatigue limit of the 3D-C/SiC is higher than that of the 2D-C/SiC, the fiber pullout length of the fatigue fracture surface of the 3D-C/SiC is longer than that of the 2D-C/SiC, and fracture morphology of the 3D-C/SiC is rougher, and pullout length of the fiber tows is longer. At the same time the 3D-C/SiC has higher tensile creep resistance. The tensile curve and the tensile creep curve of both materials consist of a series of flat step. These phenomena can be explained by the non-continuity of the damage.

关键词: 2D-C/SiC , null , null

V-M(M=Li,Na,K,Sc,Ag)二元系的相图热力学研究

胡标 , 尹明 , 王庆平 , 闵凡飞 , 杜勇

兵器材料科学与工程

基于文献报道的实验数据,采用相图计算(CALPHAD:CALculation of PHAse Diagrams)方法对V-M(M=Li,Na,K,Sc,Ag)5个二元系进行相图热力学研究.通过热力学优化计算获得了一套描述液相、(V)、(Li)、(Na)、(K)、(αSc)、(βSc)和(Ag)相的热力学参数.V-Li、V-Na和V-K体系中的气相视为由组元V、Li、Li2、Na、Na2、K和K2混合的理想气体.与实验相图数据对比表明,获得的热力学参数能够准确地描述实验相平衡数据.

关键词: V-M(M=Li,Na,K,Sc,Ag) , CALPHAD方法 , 相图 , 热力学模型

Li1+xV3-yMyO8(M=Mo,P)高温阴极放电性能的研究

曹笃盟 , 李志友 , 周科朝

稀有金属材料与工程

采用固相反应法制备了Li1+xV3-yMyO8(M=Mo,P;0≤y≤0.4),研究了不同Mo和P含量对Li1+xV3O8相的影响,并首次对其进行了高温阴极放电性能的研究.结果表明:Mo和P掺杂量分别为y≤0.2和y＜0.2时可获得纯Li1+xV3O8相;Mo掺杂使Li1+xV3O8峰值电压提高0.3 V,比容量提高25%,嵌入的Li+量最高可达x=3.8;P掺杂(y≤0.20)对Li1+xV3O8的峰值电压和比容量影响较小.化学嵌锂实验也证实掺杂后的材料具有更快的Li+嵌入速度.

关键词: Li1+xV3O8 , 热电池 , 掺杂 , 比容量

Local structures of the tetragonal Gd3+-V-M and Gd3+-Li+ centers in perovskite fluorides

Radiation Effects and Defects in Solids

The zero-field splittings b(2)(o) of the tetragonal Gd3+-V-M and Gd3+-Li+ centers for Gd3+ ions in fluoroperovskite crystals have been studied on the basis of the superposition model in which the value of t(2) (b) over bar(2) is Obtained from the stress-dependence of EPR spectra for RbCaF3:Gd3+ crystal. From the studies, the local structures of both tetragonal centers in fluoroperovskite crystals are obtained and the results are discussed.

关键词: electron paramagnetic resonance;local crystalline structure;superposition model;Gd3+;fluoroperovskite;electron-paramagnetic-res;crystals;cr-3+-li+;spectra;epr

Studies of the local structural parameters of rhombic V2+-V-M centers in MCl : V2+ (M = Li, Na) crystals from EPR data

Journal of Physics and Chemistry of Solids

In this paper, the high-order perturbation formulae of zero-field splitting D, E and g factors g(x), g(y), and g(z) for d(3) ions in rhombic symmetry are established by using a two spin-orbit (S.O.) parameter model in which the contributions due to both the S.O. coupling of the central d(3) ions and that of the ligands are considered. Based on these formulae, the local structural parameters of the rhombic defect centers V2+-V-M (i.e, the V2+ ion and a host metal ion vacancy V-M) in MCl:V2+ (M = Li, Na) crystals are estimated by calculating their EPR parameters. The results are discussed. (C) 1998 Elsevier Science Ltd. All rights reserved.

关键词: inorganic compounds;crystal fields;defects;electron paramagnetic;resonance (EPR);ions

Explanations of the EPR parameters for the rhombic Cr3+-V-M and Cr3+-Li+ centers in A(2)MF(4) (A = K, Rb, Cs; M = Mg, Zn, Cd) crystals

Radiation Effects and Defects in Solids

In this paper, we establish the high-order perturbation formulas of EPR zero-field splittings D, E and g factors, g(x), g(y) and g(z) for 3d(3) ions in a sort of rhombic symmetry where the symmetry axes and hence the crystal-field axes lie along the [001], [010] and [100] axes. From these formulas, the EPR parameters D, E, g(x), g(y) and g(z) for the rhombic Cr3+-V-M and Cr3+-Li+ defect centers in the tetragonal A(2)MF(4) (A = K, Rb, Cs; M = Mg, Zn, Cd) fluorides are calculated by considering the suitable defect-induced lattice distortions. The results are in reasonable agreement with the observed values.

关键词: electron paramagnetic resonance;crystal-field theory;superposition;model;lattice distortions;Cr3+;A(2)MF(4) (A = K, Rb, Cs;M = Mg, Zn,;Cd;spin-orbit coupling;electron-paramagnetic-res;superposition model;cr-3+ centers;ions;rb2znf4;spectra;k2mgf4;k2znf4

β-MxV2O5(M=Li,Na,K)的溶胶凝胶法合成及其高温阴极放电性能

李志友 , 黄伯云 , 汤春峰 , 刘志坚 , 曲选辉

功能材料

用柠檬酸盐溶胶-凝胶工艺制取了三种β-MxV2O5氧化物Li0.3V2O5、Na0.33 V2O5和K0.25V2O5;TG和DTA试验显示干凝胶焙烧过程中出现两个吸热峰,中间有一个放热峰;XRD分析表明高温处理时Li0.3 V2O5可氧化成LiV3O8和V2O5,而Na0.33V2O5和K0.25有较好的化学稳定性;模拟Li-B合金/LiCl-KCl/β-MxV2O5(或α-V2O5)热电池500℃放电试验表明β相阴极放电较α相平稳,但初始电压峰值略有降低,β-Li0.3V2O5相因具有较α-V2O5相更通畅的Li+快速扩散通道,且通道内没有Na+或K+大离子对Li+扩散的阻碍,放电最为平稳,有效比容量最高.

关键词: 溶胶-凝胶工艺 , β相钒青石 , 热电池 , 阴极

MZnPO4 ∶RE(M=Li,Na,K; RE=Eu3+,La3+,Ce3+)的高温固相合成及其发光性质

黄增尉 , 梁慧 , 马少妹 , 袁爱群 , 宋宝玲 , 廖森

稀有金属 doi:10.13373/j.cnki.cjrm.2014.06.018

采用高温固相反应合成MZnPO4∶RE(M=Li,Na,K; RE=Eu3+,La3+,Ce3+),用X射线衍射(XRD)、扫描电镜(SEM)和能谱分析(EDS)等方法对产物进行了表征,并对产物的发光性能进行研究.结果表明:掺杂三价稀土离子Eu3+,La3+,Ce3+没有改变MZnPO4(M=Li,Na,K)的晶体结构和颗粒形貌;在紫外光(260 nm)激发下,Eu3+掺杂的MZnPO4∶Eu3+ (M =Li,Na,K)改变了MZnPO4(M=Li,Na,K)原有的发光波长,发射橙红色光,主峰位于595 nm附近,为Eu3+的5 D0→7F1跃迁发射;La3+,Ce3+掺杂的MZnPO4∶RE(M=Li,Na,K,RE=La3+,Ce3+)则发射蓝色光,最高峰对应波长为400 ～ 500 nm,没有改变MZnPO4(M=Li,Na,K)的发光波长,但提高了强度,La3+掺杂的强度大于Ce3+掺杂;除了基质本身对发光的贡献外,Ce3+有很弱的5d1 →4f1的跃迁发射,而非荧光稀土离子La3+作为添加剂可提高基质材料的荧光性能.

关键词: 发光材料 , 磷酸锌钾 , 磷酸锌钠 , 磷酸锌锂

Theoretical studies of g factors and defect structures for cubic, tetragonal, and orthorhombic Fe+ Centers in alkali halides MX (M = Li, Na; X = F, Cl)

Communications in Theoretical Physics

The EPR g factors for cubic, tetragonal and orthorhombic Fe+ centers in alkali halides MX (M = Li, Na; X = F, Cl) are calculated from second-order perturbation formulas of g factors based on cluster approach for 3d(7) ions in three symmetries. From calculations, the g factors of these Fe+ centers in MX crystals are reasonably explained and the defect structural data for the tetragonal and orthorhombic Fe+ centers are estimated. The results are discussed.

关键词: crystal;and ligand-field theory;electron paramagnetic resonance;defect structure;atomic screening constants;spin-orbit interaction;superposition model;resonance-spectra;epr parameters;crystal-field;scf functions;ions;co2+

Li_(0.5)MAl_(0.5)SiO_4:Eu,Bi的合成和发光特性(M=Mg,Ca,Sr,Ba)

李彬 , 田一光 , 孟继武

材料研究学报

首次用高温固相反应合成了Li_(0.5)MAl_(0.5)SiO_4:Eu,Bi(M=Mg,Ca,Sr,Ba)发光体,研究了基质中不同碱土金属离子对Eu~(3+)和Bi~(3+)的发光特性以及Bi~(3+)敏化Eu~(3+)发光性能和能量传递特点,得到了良好的基质组成和一些规律性结果。用395nm 紫外线激发,M=Mg 时的发光强度比Y(V,P)O_4:Eu强约60%。Bi~(3+)发光的Stokes 位移与M(Ⅱ)的离子半径呈线性关系。

关键词: 无机材料 , photoluminescence , silicate