材料期刊网

Calculation of the Magnetization and Magnetocaloric Effect in the MnFeP0.45As0.55 Compound

G.F. Wang , L. Song , Z.Q. Ou , Z.R. Zhao

金属学报(英文版)

A magnetic state equation of the MnFeP0.45As0.55 compound has been obtained by minimizing the Gibbs free energy with respect to the volume and the magnetization based on the Bean-Rodbell model. The isothermal magnetization of the compound has been calculated using this equation. The magnetic entropy change of the compound was determined from the surface area between the two adjacent isothermal magnetization curves divided by the average temperature. A comparison and an error analysis of the calculated magnetic entropy change and the one determined from the experimental data are given.

关键词: bean-rodbell model , null , null

G(f)/HA-CS复合材料的制备及性能研究

沈基显 , 黄剑锋 , 曹丽云 , 曾燮榕 , 熊信柏

稀有金属材料与工程

以羟基磷灰石-壳聚糖(HA-CS)为基体,玻璃纤维G(f)为增强相,采用原位杂化法制备短玻璃纤维增强HA-CS基生物复合材料.研究交联剂、羟基磷灰石含量和玻璃纤维含量对复合材料性能的影响.采用红外吸收光谱、扫描电子显微镜和万能材料试验机对材料的结构和性能进行表征.结果表明:原位杂化法能制备性能较好的复合材料;用戊二醛交联改性复合材料可以明显增加其韧性和弯曲强度,使复合材料抗弯曲强度提高16%;当CS/HA=10/1(质量比)和玻璃纤维含量为1.5%时复合材料抗折强度达到极大值84.47 MPa;随玻璃纤维含量的增加,复合材料的断裂面由平整向多层断裂变化,材料的韧性有所提高.

关键词: G(f)/HA-CS复合材料 , 玻璃纤维 , 交联剂 , 弯曲强度

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+

Two-step magnetization in a spin-chain system on the triangular lattice: Wang-Landau simulation

Physical Review B

The Wang-Landau algorithm is used to study the thermodynamic and magnetic properties of triangular spin-chain system based on two-dimensional Ising model in order to understand the magnetic-order dynamics in Ca(3)Co(2)O(6) compound. The calculated results demonstrate that the equilibrium state of the rigid spins produces the two-step magnetization curve at low temperature even when the random-exchange term is considered. This work indicates that the four-step magnetization behavior observed experimentally must be due to the nonequilibrium magnetization.

关键词: calcium compounds;exchange interactions (electron);Ising model;magnetisation;thermodynamics;one-dimensional ca3co2o6;density-of-states;compound ca3co2o6;phase-diagram;proteins;crystal

Investigations of EPR g Factors and Rhombic Distortion for the Rhombic Cu2+ Centers in K2Zn1-x Cu (x) F-4 Crystals at Low Temperature

Applied Magnetic Resonance

The electron paramagnetic resonance g factors g (i) (i = x, y, z) of two rhombic Cu2+ centers, Cu2+(II) and Cu2+(III), in K2Zn1-x Cu (x) F-4 crystals found at low temperature are calculated from the complete diagonalization (of energy matrix) method based on the cluster approach. The calculations show that the ground state wave function of the two rhombically compressed Cu2+ centers is with a small admixture of . The rhombic distortions for both Cu2+ centers are obtained from the calculations. The results are discussed.

关键词: electron-paramagnetic-resonance;atomic screening constants;hyperfine;parameters;gyromagnetic factor;spin resonance;scf functions;field;copper(ii);dependence;spectra

Investigations of the EPR g factors for Er3+ in CaMoO4

Zeitschrift Fur Naturforschung Section a-a Journal of Physical Sciences

The electron paramagnetic resonance (EPR) g factors g(parallel to) and g(perpendicular to) for Er3+ in CaMoO4 are theo retically investigated by using the perturbation formulas of the g factors for a 4f(11) ion in tetragonal symmetry. In these formulas, the contributions to the g factors arising from the second-order perturbation terms and the admixture of various states are considered. The crystal-field parameters for the tetragonally distorted tetrahedra are determined by using the superposition model and the structural data of the impurity Er3+ on the host Ca2+ site in CaMoO4. The calculated g factors agree with the. observed values. The validity of the results is discussed.

关键词: electron paramagnetic resonance (EPR);crystal- and spin Hamiltonians;Er3+;CaMoO4;electron-paramagnetic-resonance;superposition-model;molybdate;crystals;calcium molybdate;ion;spectroscopy;parameters;tungstate;liyf4

A Novel Topological Index F* and Its Correlation With Standard Formaton Enthalpies of ABn(g) Molecules

武汉理工大学学报-材料科学版(英文版)

关键词:

ANISOTROPY OF THE G-FACTOR FOR NI2+ AND NI3+ IONS IN THE TETRAGONAL PHASE OF SRTIO3

Physica B-Condensed Matter

In this paper, a simple and uniform expression for calculating the anisotropy of the g factor (characterized by DELTAg = g(perpendicular-to) - g(parallel-to)) for 3d(n) ions in the tetragonal phase of the perovskite structure from the spin-lattice coupling coefficients F11 and F12 in the cubic phase has been proposed by introducing a release factor k. From this expression, the values of DELTAg for Ni2+(3d8) and Ni3+ (3d7) ions in the tetragonal phase of a SrTiO3 Crystal are studied. It is found that for SrTiO3:Ni2+, the observed isotropy of the g factor (DELTAg = 0) is due to the too small value of (F11 - F12) and for SrTiO3: Ni3+, the contribution to DELTAg from the elongation of the octahedron around the Ni3+ ion is important in the case of T near the transition temperature T(c).

关键词: lattice coupling-coefficients;cubic symmetry;fij

Investigations of the local structure and the g factors for the tetragonal Er3+ center in KMgF3

Materials Letters

The local structure and the electron paramagnetic resonance (EPR) g factors for the tetragonal Er3+ center in KMgF3 are theoretically studied by using the perturbation formulas of the g factors for a 4f(11) ion in tetragonal symmetry. In these formulas, the contributions to the g factors from the second-order perturbation terms and the admixtures of various states are taken into account. Based on the studies, the impurity Er3+ is expected to occupy the octahedral Mg2+ site, associated with an oxygen ion substituting for one of the nearest F- (i.e., O-F) in the C-4 axis, due to charge compensation. Because of the electrostatic attraction of the compensator O-F, the Er3+ ion is found to take an axial displacement Delta Z (approximate to 0.07 angstrom) towards the compensator along the C-4 axis. The calculated g factors based on the above displacement Delta Z show reasonable agreement with the observed values. (C) 2005 Elsevier B.V. All rights reserved.

关键词: defects;electron paramagnetic resonance (EPR);crystal fields;Er3+;KMgF3;electron-paramagnetic-resonance;superposition-model analysis;ce3+;luminescent centers;crystal-field;perovskite kmgf3;parameters;conversion;fluorides;site;ion

离子色谱法测定电镀液中F-和Cl-

冶金分析

提出了离子色谱法检测电镀液中F-和Cl-的方法.根据高沸点酸置换低沸点酸,用硫酸作为蒸馏剂,在一定的温度下,将F-和Cl-一起蒸馏出进行分离和富集,消除了电镀液中大量共存离子的干扰和对色谱柱的污染.使用IonPacASl4A作为色谱柱,在合适的色谱条件下,F-和Cl-的色谱峰能很好地分离,其检出限分别为0.84 μg/L和0.37 μg/L,相对标准偏差F-小于7.3%,Cl-小于4.2%(n=10),加标回收率F-在91%～107%、Cl-在95%～105%之间(n=10),电镀液中共存离子对F-和Cl-的测定无干扰.方法用于电镀液中F-和Cl-的同时测定,具有很好的可行性和实用性.

关键词: F- , Cl- , 离子色谱 , 蒸馏法 , 电镀液