Investigation of High Strain-Rate Deformation and Failure of FCC and BCC Nanostructures

非技术描述：纳米结构如纳米线和纳米管被设想在用于能源、电子设备和纳米机电系统的下一代先进材料中发挥关键作用。这种广泛的技术适用性引起了广泛的表征纳米结构的基本性质的需求，但以前的研究忽略了在高应变率条件下表征这些材料。该项目涉及使用透射电子显微镜表征金属纳米线在高应变率下的机械性能，并开发新的理论模型来理解纳米线结构与其机械性能之间的关系。这项基础研究提供了机会，开发新的教育模块的机械性能测试的主题，并刺激在设计和制造高性能的强大的纳米器件的新的创新。 此外，培养研究生和博士后也是本研究的重要内容。技术条件：本研究的目的是首次探索直径小于150 nm的金属纳米线在高应变率（高达10^5 /s）下的力学响应，阐明纳米结构在高应变率下的结构-性能关系。为此，纳米线的实验特征在于增强微机电系统（MEMS）的机械表征平台，具有原位透射电子显微镜（TEM）测试的能力。新设计的MEMS平台具有基于压电的驱动和减少的质量，旨在实现高达10^5/s的应变率。该测试与动态高速TEM（DTEM）相结合，以获得变形和失效过程的高速成像。这些最先进的实验技术产生了重要的见解，对金属纳米线的高应变率力学行为的理解，在有限的几何形状中的位错过程，以及基于分子动力学（MD）的金属建模的原子间势的验证。这种验证对原子建模非常有益，不仅适用于机械表征，而且适用于广泛的科学学科，其中MD模拟用于深入了解化学，电学和热学材料行为。

NON-TECHNICAL DESCRIPTION: Nanostructures such as nanowires and nanotubes are envisioned to play a critical role in the next generation of advanced materials for energy, electronic devices, and nano-electromechanical systems. This broad technological applicability has elicited a demand for extensive characterization of the fundamental properties of nanostructures, yet previous studies have neglected to characterize these materials under high strain-rate conditions. This project involves characterizing the mechanical properties of metallic nanowires at high strain rates using transmission electron microscopy and developing new theoretical models to understand the relationship between the structure of the nanowires and their mechanical properties. This fundamental research provides opportunities to develop new educational modules on the subject of mechanical properties testing and stimulates new innovations in the design and manufacture of high performing robust nanoscale devices. As well, training of a graduate student and post-doctoral associate is an inherent part of this research.TECHNICAL DETAILS: The goal of this research project is to explore for the first time the mechanical response of sub-150 nm-diameter metallic nanowires at high strain rates (up to 10^5 /s) to elucidate the structure-property relationships of nanostructures at high strain rates. To this end, nanowires are experimentally characterized by augmenting microelectromechanical systems (MEMS) mechanical characterization platforms with capabilities for in situ transmission electron microscopy (TEM) testing. The newly designed MEMS platforms with piezoelectric-based actuation and reduced mass are designed to attain strain rates up to 10^5/s. This testing is coupled to dynamic, high-speed TEM (DTEM) in order to obtain high speed imaging of the deformation and failure processes. These state-of the-art experimental techniques yield significant insights toward the understanding of high-strain rate mechanical behavior of metallic nanowires, dislocation processes in confined geometries, and validation of interatomic potentials for molecular dynamics (MD)-based modeling of metals. This validation is extremely beneficial to atomistic modeling, not only for mechanical characterization, but for a breadth of scientific disciplines where MD simulations are used to gain insights into chemical, electrical, and thermal material behavior.