Stability and Dynamics of Mesoscale Microstructure

9633719将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。主要目的是开发一个统一的模型，不仅可以有效地研究单晶中具有竞争的短程和长程相互作用的多域结构，而且还可以研究技术感兴趣的陶瓷材料中的多晶和多相微结构。采用连续体场方法，研究了三个具体问题：铁电氧化物中由于静电能、弹性能和磁化壁能的竞争而产生的磁畴形成和动力学；弛豫铁电体中纳米有序磁畴的形成；以及由总界面能降低驱动的多颗粒材料微结构演化的动力学。%该基金研究材料研究中的一个重要的基本问题，该问题具有关键的技术影响。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。要研究的特殊体系是陶瓷材料，其中微观结构的控制直接关系到材料的性能。在这项研究中特别感兴趣的是铁电材料，它可以用作传感器和光学元件。***

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. ***