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Plasticity, Phase Transformations, and their Interaction under High Pressure in Silicon

硅中的塑性、相变及其在高压下的相互作用

基本信息

批准号：
1943710
负责人：
Valery Levitas
金额：
$ 50万
依托单位：
Iowa State University
依托单位国家：
美国
项目类别：
Standard Grant
财政年份：
2020
资助国家：
美国
起止时间：
2020-05-01 至 2024-04-30
项目状态：
已结题

来源：
https://www.nsf.gov/awardsearch/showAward?AWD_ID=1943710&HistoricalAwards=false
关键词：
Plasticity Phase Transformations their Interaction

项目摘要

The interaction between crystalline phase transformations and permanent plastic deformation under high pressure in materials is broadly found in several technological applications; however, knowledge of this phenomenon is scarce because of the specialized equipment needed to observe it. This award fills the gap by supporting an integrated experimental, theoretical, and computational study of this interaction in silicon. Silicon is chosen as a representative material because it exhibits numerous types of phase transformations and is widely used in electronics and micro-electromechanical systems, as well as solar cells. The knowledge gained on the fundamental aspects of phase transformation-plasticity interaction under high pressure will also have broader implications on the quantitative modeling and optimization of surface processes, such as polishing, turning, and scratching, for brittle semiconductors and ceramics. As part of the project, there will be opportunities to educate and train graduate and undergraduate students through special courses and research, parts of which will be conducted at the Argonne National Laboratory, with an emphasis on underrepresented students.The objective of this research is to investigate the effect of plastic flow on phase transformation under high pressure in silicon. Coupled in situ high-throughput experiments and modeling will yield quantitative characterization and understanding of how plastic straining drastically reduces the transformation pressure, promotes the formation of novel phases, retains high-pressure phases at ambient pressure, and changes transformation paths between different phases. Silicon samples will be compressed and sheared in a rotational diamond anvil cell. Synchrotron X-ray diffraction and absorption, Raman spectroscopy, and displacement measurements will be used for in-situ diagnostics of the deformation and transformation processes. A microscale phase field approach for coupled phase transformations and localized shear bands (e.g., due to dislocation pileups) will be developed and used to study the interplay between multiple phase transformations and mechanisms of plasticity in single grains and polycrystalline aggregates. Phase transformation criteria, strain-controlled kinetic equations, and the pressure- and plastic strain-dependent yield strengths of all phases and phase mixtures will be obtained from the experiments and incorporated in a macroscale phenomenological model. This model will be used in the finite element simulations of deformation-transformation processes in diamond anvils. A search for new phases will also be performed as an application of the computational framework.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.

高压下材料的结晶相变和永久塑性变形之间的相互作用在许多技术应用中广泛存在；然而，由于需要专门的设备来观察这种现象，对这种现象的了解很少。该奖项通过支持硅中这种相互作用的综合实验、理论和计算研究来填补这一空白。之所以选择硅作为代表材料，是因为它具有多种类型的相变，广泛应用于电子和微机电系统以及太阳能电池中。在高压下相变-塑性相互作用的基本方面所获得的知识也将对表面过程的定量建模和优化具有更广泛的意义，例如抛光，车削和划痕，用于脆性半导体和陶瓷。作为该项目的一部分，将有机会通过特殊课程和研究来教育和培训研究生和本科生，其中部分课程和研究将在阿贡国家实验室进行，重点是代表性不足的学生。本研究的目的是探讨高压下塑性流动对硅中相变的影响。耦合的原位高通量实验和建模将产生定量表征和理解塑性应变如何急剧降低转变压力，促进新相的形成，在环境压力下保持高压相，以及改变不同相之间的转变路径。硅样品将在旋转金刚石砧细胞中被压缩和剪切。同步加速器x射线衍射和吸收、拉曼光谱和位移测量将用于变形和转变过程的原位诊断。耦合相变和局部剪切带（例如，由于位错堆积）的微尺度相场方法将被开发并用于研究单晶和多晶聚集体中多相转变和塑性机制之间的相互作用。相变准则，应变控制的动力学方程，以及所有相和相混合物的压力和塑性屈服强度将从实验中获得，并纳入宏观现象学模型。该模型将用于金刚石砧变形转化过程的有限元模拟。对新相位的搜索也将作为计算框架的一个应用来执行。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。