材料期刊网

断裂方式对氧化铝基复合陶瓷耐磨性的影响

张福成 , 罗海辉 , Roberts Steve-G , Todd Richard-I

无机材料学报 doi:10.3321/j.issn:1000-324X.2007.03.024

通过磨粒磨损试验测定了氧化铝陶瓷、氧化铝/碳化硅复合陶瓷和氧化铝/莫来石复合陶瓷的耐磨性.利用透射电子显微镜(TEM)观察了样品的微观结构,采用扫描电子显微镜(SEM)分析了样品的断口形貌和磨损表面的剥落情况.研究了断裂方式对磨损表面剥落和耐磨性的影响.结果表明:氧化铝陶瓷的磨损主要由断裂磨损机制控制,氧化铝/碳化硅复合陶瓷的磨损主要由塑性磨损机制控制,氧化铝/莫来石复合陶瓷受这两种磨损机制共同作用.相对于氧化铝陶瓷,氧化铝/碳化硅复合陶瓷和氧化铝/莫来石复合陶瓷的耐磨性提高2～4倍,这主要是由于其断裂方式转变为以穿晶断裂为主,减少了磨损面的脆性剥落.

关键词: 氧化铝 , 复合陶瓷 , 耐磨性 , 断裂方式

Investigations of the g factors of Fe+ in MgO and CaO

Zeitschrift Fur Naturforschung Section a-a Journal of Physical Sciences

The g factors of Fe+ in MgO and CaO are theoretically investigated by the perturbation formula of the g factor of a V ion in cubic octahedral symmetry based on the cluster approach. By considering the partial quenching of the spin-orbit coupling interaction and the effective Lande factor due to the dynamic Jahn-Teller effect (DJTE), the experimental g factors of the studied systems are reasonably interpreted. It can be suggested that the small g factors of the Fe+ centers in MgO and CaO can be likely attributed to the DJTE, rather than the covalency effect within the scheme of the static crystal-field model.

关键词: electron paramagnetic resonance;crystal- and ligand-field theory;Fe+;MgO;CaO;atomic screening constants;electron spin resonance;paramagnetic-resonance;orbit interaction;scf functions;crystals;spectra;oxide;co2+

Investigations of the g factors for Co2+ in fluoroperovskites

Physica B-Condensed Matter

The perturbation formula of g factor for 3d(7) ion in cubic octahedral crystals has been obtained from a cluster approach. In the formula, the parameters related to the configuration interaction and the covalency reduction effect can be obtained from the optical spectra of the crystal under study and so no adjustable parameters are applied. From the formula, the g factors for Co2+ in fluoroperovskites LiBaF3, KMBF3, KZnF3 and CsCdF3 are calculated. The calculated results are in agreement with the observed values. The g factor following the order of LiBaF3 : Co2+ < KMgF3 : Co2+ < KZnF3: Co2+ < CsCdF3 : Co2+ is also explained. (C) 2000 Elsevier Science B.V. All rights reserved.

关键词: electron paramagnetic resonance;crystal- and ligand-field theory;Co2+;LiBaF3;KMgF3;KZnF3;CsCdF3;perovskite;transition;impurities;crystals

利用(G’/G)展开法求解广义变系数Burgers方程

庞晶 , 靳玲花 , 应孝梅

量子电子学报 doi:10.3969/j.issn.1007-5461.2011.06.005

近年来,变系数非线性发展方程受到越来越多的关注. 2008年王明亮等提出了一种新的方法,即(G’/G)展开法.将(G’/G)展开法首次尝试应用到变系数非线性发展方程中,并以广义变系数Burgers方程为例,成功得到了在系数满足一定条件时新的精确解；又尝试将该展开法进行新的扩展,再一次对广义变系数Burgers方程求解,又成功得到了一些新解.实践证明,该展开法不仅易于求解常系数非线性发展方程,而且对变系数非线性发展方程仍很高效、简洁、实用,并且具有广泛的应用前景.

关键词: 非线性发展方程 , 精确解 , (G’/G)展开法 , 广义变系数Burgers方程

应用改进的G/G'展开法求ZS方程的精确解

冯庆江 , 杨世玲

量子电子学报 doi:10.3969/j.issn.1007-5461.2013.06.007

应用改进的G/G'展开法构造出Zhiber-Shabat(ZS)方程的20组精确解,这些解的类型主要包含双曲函数通解、三角函数通解和有理函数通解三种形式.对解的性质进行了相应分析,当对双曲函数通解中的参数取特殊值时,可以得到孤立波解.当对三角函数通解中的参数取特殊值时,可以得到对应的周期波函数解.实践证明,应用改进的G/G'展开法能够得到方程一些新的精确解,扩大了解的范围.

关键词: 非线性方程 , 改进的G/G'展开法 , ZS方程 , 孤立波解 , 周期波解

应用改进的G'/G2展开法求Zakharov方程的精确解

冯庆江 , 肖绍菊

连铸 doi:10.3969/j.issn.1007-5461.2015.01.006

应用改进的G'/G2展开法构造出Zakharov方程的18组精确解,这些解主要包括双曲函数通解、三角函数通解和有理函数通解三种形式.当对双曲函数通解中的参数取特殊值时,可以得到孤立波解.对三角函数通解中的参数取特殊值时,可以得到对应的周期波函数解.实践证明,应用改进的G'/G2展开法能够得到Zakharov方程一些新的精确解,扩大了解的范围,这种方法对于研究非线性光学和量子光学具有非常广泛的应用意义.

关键词: 非线性方程 , 改进的G'/G2展开法 , Zakharov方程 , 孤立波解

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 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

CALCULATION OF THE SPIN-LATTICE COUPLING-COEFFICIENTS G11 AND G44 FOR GAP-FE(3+) CRYSTAL

Nuovo Cimento Della Societa Italiana Di Fisica D-Condensed Matter Atomic Molecular and Chemical Physics Fluids Plasmas Biophysics

A uniform und simple method suitable to all d(n) ions is established for the calculation of spin-lattice coupling coefficients G11 and G44 in T(d) symmetry. According to the method, the coefficients G11 and G44 for Fe3+ ion in GaP crystal have been obtained from the high-order perturbation formulae of zero-field splitting in tetragonal and trigonal fields based on the spin-orbit coupling mechanism. The calculated results show good agreement with the experimental findings.

关键词: level splitting and interaction;electron paramagnetic resonance and;relaxation;crystal and ligand fields;d-orbital theory;ions

g-C3N4及改性g-C3N4的光催化研究进展

冯西平 , 张宏 , 杭祖圣

功能材料与器件学报 doi:10.3969/j.issn.1007-4252.2012.03.007

聚合型半导体材料g-C3N4因其优异的物理性能和光电性能成为当今研究的热门材料.本文从结构分析和理论计算角度讨论了g-C3N4能够作为无金属催化剂的原因,综述了介孔g-C3N4、无机元素掺杂g-C3N4、金属负载g-C3N4、g-C3N4/金属氧化物复合物和有机改性g-C3N4等不同改性g-C3N4的制备和性质,着重分析了他们催化光解水析氢反应的机理、影响因素及研究进展,并阐述了今后的研究方向.

关键词: g-C3N4 , 改性g-C3N4 , 光催化