材料期刊网

Nd-RICH PHASE PARTICLES IN AS-FORGED Ti-5Al-4Sn-2Zr-1Mo-0.25Si-1Nd ALLOY

G.P.Li , D.Li , Y.Y.Liu , S.X. Guan and Q.J.Wang (Department of Titanium Alloys , Institute of Metal Research , The Chinese Academy of Sciences , Shenyang 110015 , China)

金属学报(英文版)

TEM examination proves that the second phase particle within the as-forged Ti-55alloy consists of either bright or dark "matrix" (nano-Nd3Sn) and some small dark blocks (SnO) dispersed in the "matrix". The HREM observation shows that the nanoNd3Sn phase is roughly spherical and about 3-15nm in diameter, and the grain boundaries with atout 1nm width are "gas-like" structure.

关键词: Ti alloy , null , null

大爆炸核合成相关的8Li(d, p)9Li反应截面测量

李志宏 , 柳卫平 , 白希祥 , 郭冰 , 连钢 , 颜胜权 , 王宝祥 , 陆昀 , 曾晟 , 苏俊

原子核物理评论 doi:10.3969/j.issn.1007-4627.2005.01.006

利用8Li次级束测量了质心系能量7.8 MeV 2H(8Li, 9Li)1H反应的角分布, 导出了8Li(d, p)9Li反应的天体物理S因子及9Li→8Li+n虚衰变的渐近归一化系数.

关键词: 8Li(d,p)9Li反应 , 角分布 , 天体物理S因子 , 渐近归一化系数

Corrosion resistance of Mg-8.8Li alloy compared with AZ91

Corrosion Engineering Science and Technology

The superlight Mg-Li alloys exhibit good formability but poor corrosion resistance due to the alloying of lithium. In this paper, the corrosion behaviour of Mg-8.8Li alloy was investigated by electrochemical measurements, corrosion morphology observations and weight loss determination. The results indicate that Mg-8.8Li alloy displays worse corrosion resistance than AZ91D alloy in the early stages of corrosion. However, the corrosion resistance of AZ91D alloy declines and becomes worse than Mg-8.8Li alloy with increasing exposure time. In addition, it is found that a 250 degrees C annealing treatment has a detrimental effect on the corrosion resistance of Mg-8.8Li alloy.

关键词: Corrosion;Magnesium alloy;Mg-Li;AZ91D;Annealing treatment;mg-3nd-0.2zn-0.4zr wt.percent alloy;magnesium alloy;mechanical-properties;behavior;microstructures

Studies of EPR parameters for Mn5+-doped Li3PO4 and Li3VO4 crystals

Spectrochimica Acta Part a-Molecular and Biomolecular Spectroscopy

The EPR parameters (zero-field splitting D and g factors g(vertical bar vertical bar), g(perpendicular to)) of Mn5+-doped Li3PO4 and Li3VO4 crystals are calculated from the complete high-order perturbation formulas based on a molecular orbital scheme for a 3d(2) ion in tetragonal MX4 clusters. These formulas include not only the contribution coming from crystal-field excitations, but also that arising from charge-transfer excitations (which is discarded in crystal field theory). The calculated results are in reasonable agreement with the observed values. The contributions to EPR parameters coming from the charge-transfer excitations are comparable with those arising from the crystal-field excitations. It appears that for a high valence state 3d(n) ion in crystals, the reasonable explanations of EPR parameters should take the contributions due to both crystal-field and charge-transfer excitations into account. (c) 2006 Elsevier B.V. All rights reserved.

关键词: electron paramagnetic resonance (EPR);crystal;and ligand-field theory;charge transfer mechanism;Mn5+;Li3PO4;Li3VO4;atomic screening constants;oxo coordination;phase-transition;scf;functions;laser action;complexes;pressure;forsterite;covalency;ions

HIGH-RESOLUTION ELECTRON-MICROSCOPY STUDY OF DEFECTS IN AN FCC PHASE FORMED BY INGOT CASTING IN AL-LI-CU-MG ALLOYS

Materials Science and Engineering a-Structural Materials Properties Microstructure and Processing

An fc.c. phase designated Y has been studied by means of high resolution electron microscopy (HREM) and transmission electron microscopy in Al-Li-Cu-Mg alloys. HREM observation and electron diffraction patterns show the intergrowth of another Franker-Kasper domain (designated D) with the Y phase. The D domain can grow on both the (001) and the (111) planes of the Y phase. The orientation relationships between the D domain and the Y phase are [110]Y//[100]D, (111BAR)Y//(001)D and [110]Y//[100]D, (001)Y//(010)D.

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Energy levels of the d*(8) electron and d*(2) hole system

Physical Review B

In the investigation of the optical and magnetic properties of the semiconductors containing transition-metal ions, the one-electron orbital cannot be treated with a pure d orbital because of a strong covalence. This paper presents the energy matrix of the d*(8) and d*(2) (d* means a modified d function) system, in which the covalence is described by two covalent factors. The differences between the matrix diagonal elements of the t(2)(m)e(n) term of the d*(8) system and the t(2)(6-m)e(4-n) term of the d*(2) system vary with m and n. The d(N) electron system can be explained with the d(10-N) hole system because the difference between the energy matrix of the d(N) and d(10-N) systems has a fixed value. However, this kind of simple relation does not exist for the d*(N) and d*(10-N) systems when the covalence is considered. A numerical calculation shows that the variation of the energy levels with the covalence for Ni2+ in the d*(8) electron system is larger than that in the d*(2) hole system. The calculated energy levels obtained from the d*(8) matrix are in good agreement with the experimental data of the Ni2+ ion for ZnS:Ni and ZnSe:Ni. This suggests that the d*(8) electron system instead of the d*(2) hole system should be used in the investigation of optical and magnetic properties of semiconductor containing Ni2+ ions.

关键词: zns-ni;absorption;vanadium;impurities;spectra;ions

Investigation of the local structure of the tetragonal Ni2+-V-Li center in LiCl:Ni2+ crystal from epr parameters

Radiation Effects and Defects in Solids

The zero-field splitting D and the g factor g(parallel to), Delta g (= g(parallel to) - g(perpendicular to)) of the tetragonal Ni2+-V-Li center in LiCl:Ni2+ crystal have been studied from the high-order perturbation formulas of these EPR parameters for d(8) ions in tetragonal symmetry. On the basis of this, the local structure of this tetragonal center is determined and the negative sign of the zero-field splitting D of the crystal is obtained.

关键词: electron paramagnetic resonance;local structure;crystal-field theory;Ni2+;LiCl;spin-hamiltonian parameters;superposition-model;ni(ii) compounds;ground-state;ions;symmetry;halides;cr3+

ON SPINODAL BOUNDARIES OF Al-Li ALLOYS

WEI Yinghui , WANG Xiaotian (School of Materials Scince and Engineering , Xi'an Jiaotong University , Xi'an 710049 , China Manuscript received 10 Mareh , 1994)

金属学报(英文版)

The spinodal decomposition can occur in Al-Li alloys containing 5.8-14.2 at.% Li at room temperature. The modutated structure wavelength is approximately 3.1 nm for com mercial Al-LI alloys. The limit composition of the miscibility gap is 3.66 -16.06 at.%Li at 298 K. The highest temperature of the miscibility gap is 377 K.

关键词: : Al-Li alloy , null , null

Li改性铌钽酸钾钠无铅压电陶瓷的研究

江向平 , 胡晓萍 , 江福兰 , 刘晓冬 , 殷庆瑞

无机材料学报 doi:10.3724/SP.J.1077.2007.00465

利用固相反应法制备了(Na _0.52 K _0.48-x Li _x)(Nb _0.86 Ta _0.10 Sb _0.04)O ₃系无铅压电陶瓷, 研究了不同Li含量(x分别为0、0.02、0.04、0.06、0.08)样品的显微结构、物相组成及电性能. 结果表明, Li含量的改变对其物相组成、压电性能、铁电性能、介电性能都有显著影响. 当Li含量x从0增大到0.04时, 其压电性能相应提高, 当Li含量x超过0.04时, 压电性能明显下降; 在x=0.04时综合性能最好, 其压电常数d₃₃高达260pC/N, 介电损耗tanδ为0.027, 平面机电耦合系数k_p值达到50%, 剩余极化强度P_r为22μC·cm^-2, 矫顽电场E_c为0.95kV·mm^-1, 居里温度为316℃. 另外, 随着Li含量增加, 该系统的矫顽电场明显增强, 居里温度有所提高.

关键词: 铌钽酸钾钠 , lead-free piezoelectric ceramics , piezoelectric properties , ferroelectric properties , dielectric properties

CRYSTAL STRUCTURE OF γ-Li_xFe_2O_3 WITH ELECTROCHEMICAL INSERTION OF Li

HUANG Jianshun CHEN Junming Shanghai Institute of Metallurgy , Academia Sinica , Shanghai , China Research Associate , Shanghai Institute of Metallurgy , Academia Sinica , Shanghai 200050 , China

金属学报(英文版)

Crystal structure of γ-Li_xFe_2O_3,inserted Li electrochemically,was studied by Moss- bauer spectroscopy together with X-ray diffraction,XPS and electrochemical method,On the insertion of Li at low current density,the crystal structure is keeping original spinel; while at higher current density or by thermal activation,owing to violent movement of Li~+ ions,part of crystal structure transforms into rock type similar to face-centered cubic structure of ferrous oxide.The transition channels during insertion of Li~+ ions and limitation of Li~+ ions inserted were discussed.

关键词: null , null , null