M.E Li
,
G.C. Yang
,
null
,
null
金属学报(英文版)
Two new classes of growth morphologies, called doublons and seaweed, were simulated using a phase-field method. The evolution of doublon and seaweed morphologies was obtained in directional solidification. The influence of orientation and velocity on the growth morphology was investigated. It was indicated that doublons preferred growing with its crystallographic axis aligned with the heat flow direction. Seaweed, on the other hand, could be obtained by tilting the crystalline axis to 45°. Stable doublons could only exist in a range of velocity regime. Beyond this regime the patterns formed would be unstable. The simulation results agreed with the reported experimental results qualitatively.
关键词:
growth morphologies
,
null
,
null
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
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
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
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
陆景彬
,
刘运祚
,
孙亮
,
杨东
,
梁国栋
,
王守宇
,
马英君
,
赵广义
,
李险峰
,
崔兴柱
,
李明非
,
霍俊德
,
曾国模
,
竺礼华
,
吴晓光
原子核物理评论
doi:10.3969/j.issn.1007-4627.2005.02.003
在稀土区奇奇核πh11/2(×)νi13/2转动带中, 系统地观测到随转动频率或角动量增加, B(M1)/B(E2)曲线表现出所谓parabola-like形状, 即在增加到某一转动频率或自旋后, B(M1)/B(E2)比值快速增强. 基于推转模型和粒子转子模型关于奇奇核二准粒子转动带磁偶极约化跃迁几率的描述, 对稀土区双奇核的这一行为进行了讨论. 指出该现象的发生与νi13/2准中子转动顺排特性密切相关. B(M1)/B(E2)比值在接近第二带交叉(即BC准中子对顺排)的较高频率处的增强效果, 可以理解为主要来源于带交叉引起的波函数中混合四准粒子成分的结果. 通过对B(M1)/B(E2)比值的增强效果发生在较低频率处的分析, 对稀土区奇奇核πh11/2(×)νi13/2带角动量耦合图像有了进一步认识.
关键词:
高自旋态
,
奇奇核
,
电磁跃迁特性
,
顺排
Molecular Physics
The spin-Hamiltonian parameters (g factors g//, g perpendicular to and hyperfine structure constants A//, A perpendicular to) of the approximately-tetragonal Cr5+ centers in MVO3 (M = Li, Na, K, Rb) crystals are calculated from the complete high-order perturbation formulas for d1 ions in tetragonal symmetry with the ground state [image omitted]. These formulas are based on a two-mechanism model, in which not only the contribution to spin-Hamiltonian parameters from the crystal-field (CF) mechanism concerning CF excitations, but also that from the charge-transfer (CT) mechanism concerning CT excitations (which is neglected in the widely-used CF theory) are included. The calculated results are in reasonable agreement with the experimental values and the signs of hyperfine structure constants are suggested. The calculations show that for a high valence state dn ion (e.g. Cr5+) in crystals, the exact calculation of spin-Hamiltonian parameters should take the contributions due to both CF and CT mechanisms into account.
关键词:
electron paramagnetic resonance;charge-transfer mechanism;crystal-field theory;Cr5+;MVO3 (M = Li;Na;K;Rb);atomic screening constants;electron-paramagnetic-res;single-crystals;scf functions;epr;vo2+;ion;transition;spectra;livo3
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
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
