胶体体系中结晶过程的研究

发布时间：2018-03-03 11:52

本文选题：晶体　切入点：结晶　出处：《苏州大学》2016年硕士论文　论文类型：学位论文

【摘要】：晶体材料被广泛应用于日常生活和生产中。一般而言,晶体材料的制备是通过结晶来完成的。全面了解结晶的物理规律和控制结晶过程是得到高品质晶体材料的前提。然而,我们对结晶的理解,目前依然不全面,主要是由于原子太小、运动太快,都无法直接观察和追踪。相比之下,胶体颗粒足够大、运动慢,普通光学显微镜就可以直接观察其运动过程。尤为重要的是,溶液中的胶体颗粒可以像原子一样形成固态、液态、气态,并且各平衡态之间可以相互转化。近几十年来,利用胶体研究相变给结晶机制的研究提供了很多启示。我们研究了二维胶体体系在交变电场控制下的结晶过程。在实验中,结晶成核路径随着过饱和度的改变而变化。观察发现:体系在强驱动力下,选择经典理论描述的成核路径;体系在弱驱动力下,选择多步成核路径。在晶体生长过程中,缺陷是很难避免的。缺陷的存在对晶体的性质有着严重的影响。位错是一种常见的缺陷。已有研究发现吸引力体系和排斥力体系中的位错,在结构和扩散行为上都有着显著的差异。我们在二维胶体体系中对位错间的相互作用做了系统的研究。发现位错间的相互作用结果与位错间的夹角有密切关系。我们发现:成120°角的位错会融合成一个位错;在同一滑移线上的夹角为180°的位错会湮灭。
[Abstract]:Crystal materials are widely used in daily life and production. Generally speaking, the preparation of crystal materials is accomplished by crystallization. Comprehensive understanding of the physical laws of crystallization and controlling the crystallization process are the prerequisites for obtaining high-quality crystal materials. Our understanding of crystallization is still incomplete, mainly because atoms are too small and moving too fast to be directly observed and tracked. In contrast, colloidal particles are large enough to move slowly. Most importantly, colloidal particles in a solution can form solid, liquid, gaseous, and equilibrium states like atoms. Using colloid to study phase transition provides a lot of enlightenment for the study of crystallization mechanism. We have studied the crystallization process of two-dimensional colloidal system under the control of alternating electric field. The crystallization nucleation path changes with the change of supersaturation. It is found that the system chooses the nucleation path described by classical theory under the strong driving force, and the system chooses the multi-step nucleation path under the weak driving force. Defects are very difficult to avoid. The existence of defects has a serious impact on the properties of crystals. Dislocation is a common defect. There are significant differences in structure and diffusion behavior. We have made a systematic study of the interaction between dislocations in two-dimensional colloidal systems. It is found that the results of the interactions between dislocations are closely related to the angle between dislocations. We find that the dislocation at 120 掳angle will merge into one dislocation. The dislocation with an angle of 180 掳on the same slip line will be annihilated.
【学位授予单位】：苏州大学
【学位级别】：硕士
【学位授予年份】：2016
【分类号】：O648.1

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