Stability and Dynamics of Mesoscale Microstructure

对相变和材料加工过程中介观组织的稳定性和动态演化进行理论研究。主要目标是建立一个统一的模型，不仅可以有效地用于研究单晶中具有竞争的短距离和远距离相互作用的多畴结构，还可以用于研究技术感兴趣的陶瓷材料中的多晶和多相微观结构。采用连续场方法，研究了三个具体问题：铁电氧化物中静电能、弹性能和畴壁能相互竞争导致的畴形成和动力学；弛豫铁电体中纳米有序畴的形成在界面总能降低的驱动下，研究了多晶材料的微观结构演化动力学。这项资助研究材料研究中具有关键技术意义的重要基础问题。也就是说，将使用解析和数值方法来研究和理解材料在经历相变时微观结构的演变。这是一个极其困难的基本问题，直接影响到材料的加工。要研究的特殊系统是陶瓷材料，其微观结构的控制直接影响材料的性能。在这项研究中特别感兴趣的将是应用于传感器和光学元件的铁电材料。＊＊＊

9633719 Chen Theoretical studies will be made of the stability and dynamic evolution of mesoscopic microstructures during phase transformations and materials processing. The main objective is to develop a unified model which can efficiently be employed to study not only the multi-domain structures with competing short- and long-range interactions in a single crystal, but also the multi-grain and multi- phase microstructures in ceramic materials of technological interest. A continuum field approach is used and three specific problems will be investigated: domain formation and dynamics in ferroelectric oxides as a result of competing electrostatic energy, elastic energy and domain wall energy; the formation of nanoscale ordered domains in relaxor ferroelectrics; and, the kinetics of microstructural evolution in multi-grain materials driven by the reduction in the total interfacial energy. %%% This grant studies an important fundamental problem in materials research which has critical technological implications. Namely, analytical and numerical methods will be used to study and understand the evolution of microstructure in materials as they go through changes in phase. This is an extremely difficult fundamental problem which directly impacts materials processing. The particular systems to be studied are ceramic materials in which control of the microstructure has direct bearing on material proerties. Of special interest in this research will be ferroelectric materials which have applications as sensors and optical components. ***