材料期刊网

Thermoelectric Characterization of (Na1-yMy)1.6Co2O4 (M=K, Ca, Sr)

Ying LI

材料科学技术（英）

Oxide materials NaCo2O4 and (Na1-yMy)1.6Co2O4 (M=K, 0.05≤y≤0.35; M=Ca, Sr, 0.10≤y≤0.40) were prepared by a sol-gel method. Experimental results indicated that the Seebeck coefficient and the Power-factor of Na Co2O4 were improved by doping Ca and Sr but not by K. The Power-factor of NaCo2O4 is in its maximum, 1.68×10-4 W•m-1•K-2 and 11% bigger than that of the original one when the dopant fraction of Ca was 0.1. Doping Sr makes NaCo2O4 have the biggest Power-factor, 1.68×10-4 W•m-1•K-2 that is 50% bigger than the non-doping oxide. The experimental results indicate that suitable dopants and addition amounts could improve the thermoelectric properties of NaCo2O4 greatly.

关键词: Thermoelectric materials , materials , Electric , proper

Exact solutions of nonlinear dispersive K(m, n) model with variable coefficients

Applied Mathematics and Computation

The variable-coefficient Korteweg-de Vries (KdV) equation with additional terms contributed from the inhomogeneity in the axial direction and the strong transverse confinement of the condense was presented to describe the dynamics of nonlinear excitations in trapped quasi-one-dimensional Bose-Einstein condensates with repulsive atom-atom interactions. To understand the role of nonlinear dispersion in this variable-coefficient model, we introduce and study a new variable-coefficient KdV with nonlinear dispersion (called vc-K(m, n) equation). With the aid of symbolic computation, we obtain its compacton-like solutions and solitary pattern-like solutions. Moreover, we also present some conservation laws for both vc-K(+)(n, n) equation and vc-K (n, n) equation. (C) 2011 Elsevier Inc. All rights reserved.

关键词: Vc-K(m, n) equation;Nnonlinear dispersion;Symbolic analysis;Compacton-like solutions;Solitary pattern-like solutions;Conservation;laws;compacton solutions;solitary patterns;equations;solitons

Zn-5%Al合金超塑性的m-C-δ(或m-k-δ)关系

刘勤 , 夏锄 , 刘晓东

金属学报

在170,190,210,230,250℃的温度下,采用3.7×10~2,7.4×10~2和1.1×10~(-1)min(-1)的应变速率(平均)对Zn-5%Al共晶合金的m-C-δ(或m-k-δ)关系曲线(简称m-δ关系曲线)进行了测定.所有的曲线均随应变的δ增加而快速上升.俟达到某一定的应变量(极限应变量δ1)后。开始缓慢下降并保持平稳直至断裂.Zn-5%A1共晶合金的m-δ关系曲线不存在k_(?)=k_I(k_(I 1),k_(I 2),k_(I 3),……)=k_F(或C_0=C_I(C_(I 1),C_(I 2),C_(I 3),……)=C_F=1)的简单情况.可应用m-δ方程式[4,5]对曲线上各点C值(包括所有的C_I和C_F值)进行计算.C值随δ值的增加成近似的直线上升.直线的斜率在极限应变(δ1)处突然减小.

关键词:

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

Secondary M6C precipitation in K40S cobalt-base alloy

Materials Letters

Secondary M,C precipitation was investigated in K40S cobalt-base alloy after 100 h aging at 950 degreesC. The results showed that it was closely related to the tungsten-rich zones inherited from the as-cast condition and the degeneration of the primary M7C3 carbide. A direct element reaction, 6M + C --> M6C, in which C comes from the decomposition of the M7C3 carbides, is suggested as the mechanism of secondary M6C precipitation in K40S alloy. (C) 2001 Elsevier Science B.V. All rights reserved.

关键词: M6C precipitation;aging;M7C3 carbide;superalloy

HIGH-FIELD MAGNETIZATION OF YBA2CU3-XMXO7 (M=PB, SN) AT 4.2 K

Journal of Alloys and Compounds

Magnetization measurements on lead- or tin-doped YBa2Cu3O7 have been performed at 4.2 K in magnetic fields up to 29 T. The critical current densities are deduced from the irreversible magnetization and the pinning forces are evaluated. The effect of both lead and tin doping on the critical current density is quite appreciable. In particular, the critical current density of the sample doped with lead is more than twice that of the undoped sample. This effect is thought to be associated with the enhancement of the intergranular coupling of grains through the formation of BaPbO3 phase at the interface of the 123 superconducting phase. The relationship between the critical current density and a micrograph of the tin-doped sample is also discussed.

关键词: transport critical current;y1ba2cu3ox

Investigations of the electron paramagnetic resonance g factors Er3+-V-K for the trigonal ErK centers in KMF3 (M = Mg and Zn)

Journal of Magnetism and Magnetic Materials

The electron paramagnetic resonance g factors g(parallel to) and g(perpendicular to) for the trigonal Er3+-V-K centers (where V-K denotes K+ vacancy) in KMF3 (M = Mg and Zn) are theoretically investigated from the perturbation formulas of the g factors for a 4f(11) ion in trigonal symmetry. In these formulas, the contributions to the g factors from the second-order perturbation terms and the admixture of various energy levels are taken into account. In the above trigonal centers, the impurity Er3+ resides in the octahedral M2+ site of both crystals, associated with one V-K in the C-3-axis due to charge compensation. By analyzing their g factors, we find that the impurity Er3+ in both centers would move towards the V-K by an amount DeltaZ along the C-3-axis due to electrostatic attraction. The calculated g factors for the Er3+ centers based on the above displacements DeltaZ show good agreement with the observed values. The validity of the results is discussed. (C) 2004 Elsevier B.V. All rights reserved.

关键词: electron paramagnetic resonance (EPR);defects and impurities;crystal-field and spin hamiltonians;Er3+;KMF3;(M = Mg and Zn);crystal-field;superposition-model;perovskite kmgf3;conversion;parameters;fluorides;kznf3

Local structural parameters of the tetragonal V2+-V-M centers in MCl : V2+ (M = Na, K, Rb) crystals estimated from EPR data

Physica Status Solidi B-Basic Research

The high-order perturbation formulas of zero-field splitting D and gyromagnetic factors g(parallel to) and g(perpendicular to) for 3d(3) ions in tetragonal symmetry are established by using a two-spin-orbit(SO)-parameter model where the contributions to these EPR parameters from both the SO coupling of the central 3d(3) ions and that of the ligands are considered. From these formulas, the local structural parameters for the tetragonal V2+-V-M centers in MCl:V2+ (M = Na, K, Rb) crystals are estimated from the EPR data. The results are compared with those obtained from the conventional one-SO-parameter model where only the contribution of the SO coupling of central 3d(3) ions is included. The reasonableness of the results based on the two-SO-parameter model is discussed.

关键词: 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

A novel electrodeposited Cu-Zn-Bi film with increased corrosion resistance in a 0.05 M K(2)SO(4) solution

Applied Surface Science

A single phase Cu-Zn-Bi film is fabricated on the steel wire by electrodeposition. Bi addition (similar to 1 wt.%) greatly increases the corrosion resistance of brass (Cu-36 wt.% Zn) film in a 0.05 M K(2)SO(4) solution as shown by potentiodynamic polarization and electrochemical impendence spectroscopy (EIS) experiments. It is proposed that the main reason for the improvement in the corrosion resistance by the Bi addition is that it greatly increased the crack resistance, which thus prevents crack-induced galvanic corrosion occurring between the brass film and the steel substrate. (C) 2011 Elsevier B. V. All rights reserved.

关键词: Bi;Brass;Electrodeposition;Crack;Corrosion;copper-zinc alloys;coating deterioration;computer-simulations;unleaded brasses;stacking-faults;electrolytes;temperature;bismuth;eis