材料期刊网

SAPO-31分子筛的微波加热合成、表征及催化性能

杨杰 , 吴伟 , 周亚静 , 武光 , 赵爱娟 , 基赫佳宁O V , 托克塔列夫A V , 伊切夫斯基G V

催化学报 doi:10.3724/SP.J.1088.2011.10138

分别以异丙醇铝和磷酸为铝源和磷源,二正丁胺为模板剂,采用微波加热法成功制得AlPO4-31分子筛,并对其晶化条件进行了优化.在优化的条件下同时合成了不同含硅量的SAPO-31分子筛,采用X射线衍射、N2物理吸附、扫描电镜、固体29Si核磁共振、程序升温脱附以及吡啶吸附的红外光谱等手段对其结构和酸性进行了表征,并考察了Pd/SAPO-31双功能催化剂在正癸烷加氢异构化反应中的催化性能.结果表明,采用微波加热法在170℃晶化2h,即可合成出具有ATO结构的高结晶度的纯相AlPO4-31和SAPO-31分子筛.将Si引入到AlPO4-31骨架中所合成的SAPO-31分子筛的比表面积和微孔体积增大,通过改变初始凝胶中原料组成可调变SAPO-31分子筛骨架中硅物种的分布及酸性质.以酸性适宜的SAPO-31分子筛制备的Pd/SAPO-31双功能催化剂在正癸烷加氢异构化反应中表现出较高的活性和选择性.

关键词: 微波加热 , SAPO-31分子筛 , 二正丁胺 , 正癸烷 , 加氢异构化

A study of the temperature dependence of g factor for MgO:V2+ crystal

Physica B-Condensed Matter

The temperature dependence of EPR g factor for MgO:V2+ crystal has been studied theoretically by considering both the static contribution due to the thermal expansion of crystal and the vibrational contributions due to the electron-phonon interaction of the acoustic and optical branches. The static contribution is calculated from the high-order perturbation formula of g factor and the thermal expansion coefficients alpha(T) at various temperatures. The vibrational contribution of acoustic phonons is obtained by using a Debye model for the lattice vibrations and that of optical phonons is calculated by use of a single frequency model. The calculated results show that for the g factor at various temperatures, the static contribution is dominant, but for the temperature dependence of g factor, i.e., (dg/dT)(p) or Delta g(T) = g(T) - g(0), the vibrational contributions from the acoustic and optical phonons are comparable with the static contribution due to thermal expansion. It appears that a reasonable theoretical explanation for the temperature dependence of g factor should take all of these contributions into account.

关键词: impurities

Theoretical studies of the g factor of V3+ in III-V semiconductors

Semiconductor Science and Technology

A two spin-orbit coupling parameter model based on a cluster approach is presented in this paper for the calculations of the g factor for V3+ ions in the cation sites of GaP, InP and GaAs crystals. In this model, differing from the conventional one spin-orbit coupling parameter model, both the contributions from the spin-orbit coupling of the central 3d(2) ion and those of ligand ions are included. By using the parameters obtained from the optical spectra of the studied crystals, the calculated g shifts (g - 2.0023) are in good agreement with the observed values. Various contributions to the g shift are discussed.

关键词: electron-paramagnetic-resonance;transition-metal impurities;vanadium;gaas;crystal;epr;spectra;cr2+;gap;inp

一维伊辛模型的相变-Ⅱ

田树旬

低温物理学报

找到了一个能够用矩阵法计算的新序参量,此参量既能给出有限数量格点时一维伊辛模型中存在相变,又能给出无限数量格点时相变消失的结果.利用此序参量求出了一个计算相变点的简洁近似公式.

关键词: 一维伊辛模型 , 相变 , 矩阵法

Investigation of the zero-field splitting and g factors for V2+ in CsMgCl3

Physica B-Condensed Matter

In this paper, by using only one adjustable parameter V' (the trigonal-field parameter), the zero-held splitting D, the g factors g(parallel to) and Delta g (= g(parallel to) -g(perpendicular to)) for CsMgCl3:V2+ crystal have been calculated from the high-order perturbation formulas based on the two spin-orbit coupling parameter model. The calculated results show good agreement with the observed values. A comparison between the calculated results from various crystal field theories are also made. It is found that the difference between signs D and Delta g for CsMgCl3:V2+ crystal is caused by the contributions from the excited multiplets, particularly those arising from the free ionic term (2)G. (C) 1998 Elsevier Science B.V. All rights reserved.

关键词: crystal and ligand field theory;electron paramagnetic resonance;spin-orbit coupling;V2+ ion;CsMgCl3;crystal;spectra;ions

Studies of the zero-field splitting and g factors for V3+ in CuAlS2 crystal

Journal of Physics and Chemistry of Solids

The zero-field splitting D and g factors g(parallel to),g(perpendicular to) for V3+ ions substituting for Cu+-site and Al3+-site in CuAlS2 ternary semiconductor was calculated by using the high-order perturbation formulas based on the two spin-orbit coupling parameter model where the contributions to EPR parameters from both the spin-orbit coupling of the central 3d(2) ion and that of the ligands are considered. The calculated D, g(parallel to) and g(perpendicular to) for V3+ replacing Cu+-site are in good agreement with the observed values, whereas the calculated D value for V3+ replacing Al3+-site is not. These results show that V3+ substitutes for Cu+-site in CuAlS2 crystal. (C) 1999 Elsevier Science Ltd. All rights reserved.

关键词: semiconductors;crystal fields;defects;electronic paramagnetic;resonance (EPR);superposition model;semiconductors;resonance;spectra

Explanations of the optical spectra and g factor for V3+ ions in ZnX (X = S, Se, Te) crystals

Physica B-Condensed Matter

This paper presents a cluster approach for the calculations of the absorption band positions and the g factor of d(2) tetrahedral cluster. In the approach, the different modifications of e and t(2) orbitals of d electrons and the contribution from the spin-orbit coupling of ligands to the EPR g factor due to the mixing of d(2) ions with the ligands are considered. The calculated band positions and g factor for ZnX : V3+ (X = S, Se, Te) crystals show good agreement with the observed values by using only two adjustable parameters. The contribution from the spin-orbit coupling of ligands to the g factor is discussed. (C) 1998 Elsevier Science B.V. All rights reserved.

关键词: crystal- and ligand-field theory;optical spectra;electron paramagnetic;resonance;spin-orbit coupling;V3+ ZnX (X = S, Se, Te);vanadium centers;znte crystals

基于多尺度模型的复合材料厚板G13剪切失效分析

贾利勇 , 贾欲明 , 于龙 , 李苗 , 张旷怡 , 贺高

复合材料学报 doi:10.13801/j.cnki.fhclxb.20160630.001

针对复合材料厚板强度分析问题,通过对子层压板的刚度等效和应力/应变分解建立了一种多尺度分析模型,并引入了剪切非线性本构关系.实现了复合材料厚板结构在子层压板水平的有限元计算和铺层水平的失效判断.采用FORTRAN语言编写了适用于Abaqus/Explicit求解器的VUMAT子程序,用于模拟复合材料厚板剪切非线性响应以及面内失效,子层压板之间采用内聚力模型来模拟分层损伤.分别采用多尺度线性模型和非线性模型对厚层压板G13剪切试验进行了数值预测,并与试验结果进行了对比.分析结果表明:线性计算模型在预测结构承载能力方面有较高的精度,但在预测整体载荷-位移响应时与试验值偏差较大;由多尺度非线性计算模型得到的破坏模式以及载荷位移曲线均与试验结果吻合较好.

关键词: 复合材料 , 厚板 , 刚度等效 , 剪切非线性 , VUMAT

强迫剪切条件下Ti-6Al-4V合金的绝热剪切失效

张云鹏 , 周泽宇 , 闫妍

材料开发与应用

采用分离式Hopkinson压杆(SHPB)加载装置,分别用200 mm和150 mm打击杆以28 m/s速度对Ti-6Al-4V合金帽形试样进行强迫剪切实验,利用OM、SEM、TEM等手段分析了强迫剪切条件下Ti-6Al-4V合金的绝热剪切带演化特征和高应变率剪切变形条件下的失效模式.结果表明,在本文所述实验条件下,Ti-6Al-4V合金的绝热剪切带(ASB)表现为“白亮带”;ASB的宽度随加载时间的延长而增加;ASB边缘的裂纹是由于ASB的变形与基体的不协调而产生的,ASB中心部位的裂纹是由于非晶形成而后破碎导致的.

关键词: Ti-6Al-4V合金 , 绝热剪切带(ASB) , 强迫剪切

g factors and energy spectrum of MgO :;V2+ and their pressure-induced shifts

Communications in Theoretical Physics

The calculations of the whole energy spectrum and the g factors of the ground state and t(2)(3) E-2 excited state for MgO:V2+ at normal pressure as well as their pressure-induced shifts have been carried out on the basis of the theory of pressure-induced shifts and the diagonalization of the complete d(3) energy matrix in a regular octahedral field. The calculated results are in very good agreement with experimental data. It is found that in the range of 1 bar similar to 100 kbar, the g value of the ground state increases monotonously with pressure, but the g value of t(2)(3) E-2 excited state for MgO:V2+ decreases at first, and then increases. For the first time, the physical essentials of the pressure-induced shifts of g values for the ground state and t(2)(3) E-2 excited state have been thoroughly analyzed and revealed by taking into account the wavefunctions, energy spectra and orbital-angular-momentum reduction factors at various pressures.

关键词: high pressure effect;ligand field;optical spectra;line shift;electronic spin resonance;3d transition-metal ions;theoretical calculations;ruby;mgo-cr3+;cr3+;mgo