蓝宝石晶体的生长方向研究

本实验采用提拉法,在中频感应加热单晶炉内,进行了不同生长方向蓝宝石晶体的生长工作,分别取[11-20]和[0001]生长的晶体c面(0001)的晶片.通过应力仪、显微观测和X射线衍射等方式对晶片的位错密度等微观缺陷以及晶体结构进行了检测.实验表明:不同的生长方向生长得到的蓝宝石晶体的质量存在一定的差别,一般情况下,[11-20]方向生长的蓝宝石晶体质量优于[0001]方向生长的晶体.     

等径角挤压Al-4.25;Cu多晶材料的裂纹产生与扩展

本文使用内角为90°、外角为30°的模具对2A12铝合金进行了等径角挤压实验,并采用HitachiS-800透射电镜(TEM)研究了材料内部裂纹的产生和扩展.结果表明:挤压两次后的试样内部没有产生微裂纹,挤压三次后的试样中观察到了微裂纹的出现,而位错塞积是裂纹产生和扩展的主要因素.所以,2A12铝合金等径角挤压过程中,应该在两次挤压后进行退火处理,保证后续挤压的顺利进行.     

中子辐照铝的微观结构变化

研究了中子辐照后铝的微观结构和力学性能的变化。发现中子辐照使铝的硬度有了一定的提高,同时在铝的内部产生了大量细小的位错环。The change of microstructure and mechanical property in neutron irradiated aluminum was studied. It is found that neutron irradiation increased the hardness of the aluminum and caused the formation of many small dislocation loops in the aluminum.     

立方准晶材料中的运动螺型位错

发展了立方准晶的位错弹性理论．通过引入位移势函数,使得立方准晶的反平面弹性动力学问题归结为求解两个波动方程,得到了运动螺型位错的位移场、应力场与能量的解析表达式及运动位错的速度极限．这些为研究此固体材料的塑性变形的物理机理提供了重要的信息．     

Defect Structures of Magnetic Nanoparticles in Smectic A Liquid Crystals

Topological defects in anisotropic fluids like liquid crystals serve as a playground for the research of various effects. In this study, we concentrated on a hybrid system of chiral rod-like molecules doped by magnetic nanoparticles. In textures of the smectic A phase, we observed linear defects and found that clusters of nanoparticles promote nucleation of smectic layer defects just at the phase transition from the isotropic to the smectic A (SmA) phase. In different geometries, we studied and analysed creation of defects which can be explained by attractive elastic forces between nanoparticles in the SmA phase. On cooling the studied hybrid system, clusters grow up to the critical dimension, and the smectic texture is stabilised. The presented effects are theoretically described and explained if we consider the elastic interaction of two point defects and stabilisation of prismatic dislocation loops due to the presence of nanoparticles.     

多个共面任意分布表面裂纹的应力强度因子

采用线弹簧模型求解多个共面任意分布表面裂纹的应力强度因子。基于Ｒｅｉｓｓｎｅｒ板理论和连续分布位错思想,通过积分变换方法,将含有多个共面任意分布表面裂纹的无限平板问题归结为一组Ｃａｕｃｈｙ型奇异积分方程。利用Ｇａｕｓｓ－Ｇｈｅｂｙｓｈｅｖ笔法获得了奇异积分方程的数值解。为验证本文法的正确性,文中最后给出了有关应力强度因子或Ｐ－Ｖ曲线的数值结果并与现有的理论结果或实验结果进行了对比。结果表明了连续位     

准晶数学弹性力学和缺陷力学

对准晶数学弹性理论的基本概念和基本框架作了介绍,在此基础上分别针对目前已经发现的几类一维准晶、二维准晶和三维准晶讨论了其数学弹性的理论体系．为了求解准晶弹性的边值问题或初值一边值问题,还必须发展相应的方法论．物理工作者在研究准晶位错弹性问题中发展了Ｇｒｅｅｎ函数方法．针对一维与二维准晶弹性中几类问题提出了分解与叠加程序,这一程序的使用,使极其复杂的准晶弹性问题得到简化,进而引进位移函数或应力函数,把数目。庞大的准晶弹性基本方程化成一个或少数几个高阶偏微分方程,进一步使求解步骤大为简化．对三维立方准晶弹性也采用了类似步骤使求解过程大为简化．在以上化简的基础上,发展了准晶弹性的边值问题或初值一边值问题的复交函数方法和 Ｆｏｕｒｉｅｒ分析方法,求得了一系列准晶位错问题和裂纹问题的分析解（古典解）．在研究准晶弹性的边值问题古典解的同时,也讨论了同这些边值问题相对应的变分问题和广义解（弱解）以及这种弱解的数值方法──有限元法．在物理学家工作基础上开展的这些工作可以看作对经典数学弹性理论和方法、经典Ｖｏｌｔｅｒｒａ位错理论、普通结构材料断裂力学和经典有限元的某些发展．此外,还把一维六方准晶弹性动力学的结果与统计物理的某些      

准晶数学弹性力学和缺陷力学

对准晶数学弹性理论的基本概念和基本框架作了介绍,在此基础上分别针对目前已经发现的几类一维准晶、二维准晶和三维准晶讨论了其数学弹性的理论体系．为了求解准晶弹性的边值问题或初值一边值问题,还必须发展相应的方法论．物理工作者在研究准晶位错弹性问题中发展了Ｇｒｅｅｎ函数方法．针对一维与二维准晶弹性中几类问题提出了分解与叠加程序,这一程序的使用,使极其复杂的准晶弹性问题得到简化,进而引进位移函数或应力函数,把数目。庞大的准晶弹性基本方程化成一个或少数几个高阶偏微分方程,进一步使求解步骤大为简化．对三维立方准晶弹性也采用了类似步骤使求解过程大为简化．在以上化简的基础上,发展了准晶弹性的边值问题或初值一边值问题的复交函数方法和 Ｆｏｕｒｉｅｒ分析方法,求得了一系列准晶位错问题和裂纹问题的分析解（古典解）．在研究准晶弹性的边值问题古典解的同时,也讨论了同这些边值问题相对应的变分问题和广义解（弱解）以及这种弱解的数值方法──有限元法．在物理学家工作基础上开展的这些工作可以看作对经典数学弹性理论和方法、经典Ｖｏｌｔｅｒｒａ位错理论、普通结构材料断裂力学和经典有限元的某些发展．此外,还把一维六方准晶弹性动力学的结果与统计物理的某些     

The interaction between a screw dislocation and a wedge-shaped crack in one-dimensional hexagonal piezoelectric quasicrystals

Based on the fundamental equations of piezoelasticity of quasicrystal material,we investigated the interaction between a screw dislocation and a wedge-shaped crack in the piezoelectricity of one-dimensional hexagonal quasicrystals.Explicit analytical solutions are obtained for stress and electric displacement intensity factors of the crack,as well as the force on dislocation.The derivation is based on the conformal mapping method and the perturbation technique.The influences of the wedge angle and dislocation location on the image force are also discussed.The results obtained in this paper can be fully reduced to some special cases already available or deriving new ones.     

Dislocation distributions and tilts in Al(Ga)InAs reverse-graded layers grown on misorientated GaAs substrates

Compositionally undulating step-graded Al(Ga)In_xAs(x = 0.05–0.52) buffers with the following In P layer were grown by metal–organic chemical vapor deposition(MOCVD) on(001) GaAs with a 15°miscut. The dislocation distribution and tilts of the epilayers were examined using x-ray rocking curve and(004) reciprocal space maps(RSM) along two orthogonal 《110》 directions. The results suggested that such reverse-graded layers have different effects on α and βdislocations. A higher dislocation density was observed along the [110] direction and an epilayer tilt of-1.43°was attained in the [1-10] direction when a reverse-graded layer strategy was employed. However, for conventional step-graded samples,the dislocation density is normally higher along the [1-10] direction.