Y.D.Xiao
,
W.X.Li
,
D.Jacovkis
,
M.T.Clavaguera-Mora
,
J.Rodriguez-Viejo
,
N.Clavaguera
金属学报(英文版)
Rapidly solidified Al87Ni7Cu3Nd3 metallic glasses, prepared by using melt spinning, were treated under both isothermal and non-isothermal regime. The amorphous rib-bon and the annealed samples were closely examined by means of differential scan-ning calorimetric, conventional X-ray diffraction and high resolution transmission electron microscopy with selected-area electron diffraction, with special interest in pri-mary crystallization into α-Al nanocrystalline particles, in order to understand struc-tural characteristics of Al-based amorphous/nanocrystalline alloys, and nucleation and grain growth mechanism on the nanometer scale during primary crystallization. The results show that, the as-prepared ribbons are fully amorphous and homogeneous in the micron scale, but contain high density of quenched-in clusters or crystallite embryos. Primary crystallization mainly leads to formation of two-phase mixture of α-Al crystal and residual amorphous phase. The annealed ribbons exposed isother-mally at 110℃ for 5, 130 minutes and heated continuously up to less than 310℃ at 40℃/min consist of large amount of α-Al fec crystal nanoparticles dispersed uni-formly in an amorphous matrix. However, a very little amount of finer orthorhombic Al3Ni intermetalics particles exist in the annealed ribbons heated up to 310℃. During primary crystallization, the leading kinetic mechanics to impede growth of the α-Al crustal is soft impinaement, instead of geometric impinqement.
关键词:
rapid solidification
,
null
,
null
Physics Letters A
The magnetic properties of the mixed ferro-ferrimagnetic compounds with (A(a)B(b)C(c))(y)D, in which A, B, C and D are four different magnetic ions and form four different sublattices, are studied by using the Ising model. And the Ising model was dealt with standard mean-field approximation. The regions of concentration in which two compensation points or one compensation point exit are given in c-a, b-c and a-b planes. The phase diagrams of the transition temperature T-c and compensation temperature T-comp are obtained. The temperature dependences of the magnetization are also investigated. Some of the result can be used to explain the experimental work of the molecule-based ferro-ferrimagnet ((NiaMnbFecII)-Mn-II-Fe-II)(1.5) [Cr-III (CN)6] - zH(2)O. (C) 2003 Elsevier B.V. All rights reserved.
关键词:
mixed ferro-ferrimagnet;Ising model;four sublattices;phase diagram;transition temperature;compensation temperature;magnetic-properties;prussian blue;alloy
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
齐伟光
,
赵宝荣
,
许小忠
,
刘常明
兵器材料科学与工程
doi:10.3969/j.issn.1004-244X.2007.02.014
研究在通氩气下Y精炼剂对AZ91D镁合金组织和性能的影响.试验结果表明,AZ91D镁合金加入Y后,显微组织主要由α-Mg基体相、β相(Mg17Al12)、Al2Y相和Al6Mn6Y相组成.经复合净化处理后的AZ91D镁合金力学性能明显改善,平均抗拉强度由101.88 MPa提高到141.91 MPa,但延伸率提高不明显.
关键词:
AZ91D镁合金
,
钇
,
显微组织
,
力学性能
郭锋
,
李鹏飞
,
高霞
,
许娟
中国稀土学报
在AZ91D镁合金中添加稀土元素Ce和Y,研究了Ce,Y元素在铸态AZ91D镁合金中的存在形式以及对合金组织和性能的影响.结果表明,铸态AZ91D镁合金中加入的Ce,Y大部分形成Al4Ce和Al2Y化合物,少量剩余的Ce,Y部分取代Mg元素的位置,以代位固溶的形式固溶在α-Mg固溶体和β-Mg17Al12金属间化合物中;Ce,Y能够细化镁合金铸态组织的晶粒,使Mg17Al12相发生"断网"并减少其在组织中的相对比例;适量添加Ce,Y能够提高AZ91D镁合金铸态机械性能,其主要原因是Ce,Y的细晶作用、固溶强化作用、Al-RE相的第二相强化作用以及对Mg17Al12相强化作用的改善.
关键词:
稀土铈和钇
,
AZ91D镁合金
,
存在形式
,
组织性能
Journal of Applied Physics
The four optical spectrum bands (or d-d transitions) and six spin Hamiltonian parameters (g factors g(x), g(y), g(z) and hyperfine structure constants A(x), A(y), A(z)) of the rhombic Zr3+ (4d(1)) center in Y3Al5O12 crystal are calculated from the complete diagonalization (of energy matrix) method and the perturbation theory method. The calculated results from both methods are not only close to each other but also in good agreement with the experimental values. It appears that the two microscopic theory methods (which are very close to those used in a 3d(1) system) are effective in the explanations of the optical and electron paramagnetic resonance spectra for a 4d(1) system. From the calculations, the optical spectrum bands are reassigned and the defect structure of the rhombic Zr3+ center in Y3Al5O12 crystal is estimated. (c) 2007 American Institute of Physics.
关键词:
electron-paramagnetic-res;crystal fields;epr;ions;linewidth
齐伟光
,
王进华
,
邢志媛
,
吕绯
,
刘环恩
,
李冬梅
兵器材料科学与工程
doi:10.3969/j.issn.1004-244X.2009.04.022
为改善镁合金的耐腐蚀性能,进一步拓宽镁合金的应用范围,研究通氩气下加入稀土Y对AZ91D镁合金组织和性能的影响.结果表明:AZ91D镁合金加入Y后,显微组织主要由α-Mg基体相、β相(Mg_(17)Al_(12))、Al_2Y相和Al_6Mn_6Y相组成.加入1%Y能显著降低合金的腐蚀速度,提高合金的平衡电位和腐蚀电位,降低腐蚀电流.
关键词:
镁合金
,
显微组织
,
腐蚀性能
张兴
,
郑成武
,
李宁
,
周兴丹
,
李正强
,
华瑞茂
液晶与显示
doi:10.3788/YJYXS20122704.0448
介绍了3D显示的基本原理,重点介绍了目前3D显示的主流技术类型,包含了眼镜式3D技术以及裸眼式3D技术,其中眼镜式3D技术包含色差式3D技术、偏光式3D技术和主动快门式3D技术;裸眼式3D技术包含视差屏障式3D技术、柱状透镜式3D技术、指向光源式3D技术和多层显示式3D技术.阐述了各种3D显示技术的基本实现原理和应用领域、并对涉及液晶显示的几种3D技术的优缺点进行了对比.结合液晶材料的特点与3D液晶显示的实际要求,阐述了3D液晶面板对液晶材料快速响应方面的要求,以及液晶透镜对液晶材料光学各向异性参数的要求.
关键词:
3D显示
,
眼镜式3D显示
,
裸眼式3D显示
,
液晶材料
Journal of Luminescence
Two theoretical methods, the perturbation theory method (PTM) and the complete diagonalization (of energy matrix) method (CDM), are applied to calculate the spin-Hamiltonian parameters (g-factors g(parallel to), g(perpendicular to) and hyperfine structure constants A(parallel to), A(perpendicular to), obtained from electron paramagnetic resonance (EPR) spectra) and d-d transitions (obtained from optical spectra) for two tetragonal Cu(2+) centers in Ba(2)ZnF(6):Cu(2+) crystals. The Cu(2+)(I) ion replaces the Zn(2+) ion at tetragonally compressed octahedral coordination and has the ground state (2)A(1)(vertical bar d(z2) >),whereas the Cu(2+)(II) ion is at an interstitial site with a square-planar F-coordination and has the ground state (2)B(2)(vertical bar d(x2-y2>)). The calculated spin-Hamiltonian parameters and d-d transitions from the PTM and CDM coincide and are in reasonable agreement with the experimental values. This suggests that both methods are effective for the theoretical studies of EPR and optical spectral data for 3d(9) ions in tetragonal symmetry with different ground states. The defect structures of the two Cu(2+) centers in Ba(2)ZnF(6):Cu(2+) are also estimated. (c) 2009 Elsevier B.V. All rights reserved.
关键词:
Electron paramagnetic resonance (EPR);d-d transition;Crystal-field;theory;Defect structure;Cu(2+);Ba(2)ZnF(6);paramagnetic-res spectrum;hyperfine parameters;optical-spectrum;3d(n);ions;epr;field;distortions;resonance;ligand
