Nano-mechanical Properties of Grain Boundaries

美国国家科学基金会（NSF）提议0625650：晶界的纳米力学性能[ei: Md A Haque，宾夕法尼亚州立大学，宾州大学帕克分校]摘要：50多年来，对晶界的研究已经确定了晶界对材料整体强度的影响，但对其屈服强度或杨氏模量的实验研究在文献中很少。这是因为晶界是随机的界面网络，只有几纳米宽，不能被传统的拉伸、弯曲、压痕工具隔离和表征。该项目旨在通过使用微机电（MEMS）力和位移传感器以及原位透射电子显微镜（TEM）开发实验装置来解决这一挑战。由于TEM使微观结构可见，实验装置将允许同时表征晶体取向，裂纹扩展和原子分辨率的塑性变形机制。将建立基于界面断裂力学的模型，从实验数据中提取晶界特性。对材料界面的基本认识将影响晶界工程，这是优化材料设计的一个不断发展的研究方向。该项目将整合研究生、本科生和K-12阶段的力学、显微镜和微/纳米技术的研究和教育，同时促进多样性。研究成果将通过会议和期刊文章传播。一名女性/少数族裔本科生将通过与宾夕法尼亚州立大学少数族裔工程项目的合作参与其中。将开设一门名为纳米材料力学的研究生课程。在补充资金的支持下，将执行两个外展项目：(1)“K-12显微镜”，当地小学、初中和高中学生将操作电子显微镜；(2)为K-12教师举办为期两周的暑期讲习班。

NSF Proposal 0625650: Nano-mechanical Properties of Grain BoundariesPI: Md A Haque, the Pennsylvania State University, University Park, PA Abstract: More than 50 years of research on grain boundaries has established their impact on the overall strength of materials, yet experimental studies on their yield strength or Young's modulus are rare in the literature. This is because grain boundaries are random networks of interfaces that are only a few nanometers wide and cannot be isolated and characterized by conventional tensile, bending, indentation tools. This project aims to address this challenge by developing an experimental setup using micro-electro-mechanical (MEMS) force and displacement sensors and in-situ transmission electron microscopy (TEM). Since TEM renders the microstructures visible, the experimental setup will allow simultaneous characterization of crystallographic orientations, crack propagation and plastic deformation mechanisms with atomic resolution. Models based on interfacial fracture mechanics will be developed to extract the grain boundary properties from the experimental data. The fundamental understanding on the interfaces in materials will impact grain boundary engineering, an evolving research direction towards optimized materials design. The project will integrate research and education on mechanics, microscopy and micro/nanotechnology at graduate, undergraduate and K-12 levels while promoting diversity. The research outcomes will be disseminated through conferences and journal articles. One female/minority undergraduate student will be involved through collaboration with the Penn State Minority in Engineering Program. A graduate course titled Mechanics of Nano Materials will be developed and offered. With supplemental funding, two outreach programs will be executed: (1) 'Microscopy for K-12' where local elementary, middle and high school students will operate an electron microscope and (2) Two-week long summer workshop for K-12 teachers.