Structure and Dynamics of Metallic Glass Alloys

非技术摘要：玻璃是无处不在的材料，包括窗户玻璃和大多数塑料。由金属元素组成的玻璃具有极高的强度，作为人体植入物具有良好的兼容性，并可能用于催化和微型机器中的活动部件。然而，玻璃中的原子是无序的--就像一堆沙子里的颗粒一样杂乱无章--而不是像钢铁等传统金属合金中的原子那样，以规则的有序阵列排列。这种无序使人们很难理解原子是如何排列的，以及它们是如何相互移动的。本项目在一台先进的扫描电子显微镜上利用纳米直径的高能电子束研究了金属玻璃合金的原子排列和原子运动。在室温下，电子如何在固体状态下从样品原子上散射出来，揭示了原子是如何排列的。当样品在显微镜内熔化时，电子散射如何随时间变化，揭示了原子是如何运动的。了解原子的排列和运动有助于材料科学家理解为什么金属玻璃具有如此特殊的性质，并帮助他们为新的应用设计新的金属玻璃材料。该项目还通过创建和分发支持新实验的软件来建设对金属的高级电子显微镜研究的能力，并支持本科生和普通公众对看到活在电子显微镜中的原子-物质的基本构件-的兴奋参与。技术摘要：该项目支持使用波动电子显微镜和电子相关显微镜形式的相干电子纳米衍射来研究金属玻璃的结构和原子动力学。利用涨落显微镜和混合反蒙特卡罗模拟对静态结构的研究正在朝着金属玻璃合金纳米量级的一般结构模型发展。用电子相关显微镜研究过冷液态的动力学是基于空间非均质动力学的玻璃形成液体脆性的检验模型，可能为深入了解金属合金中的玻璃转变提供基础。从玻璃的电子纳米衍射的微妙角度关联中提取结构信息的其他技术正在开发中。该项目还通过传播波动显微镜和电子相关显微镜的数据采集和分析软件，支持研究能力建设，并开展外联活动，为公众带来最先进的电子显微镜的兴奋。

NON-TECHNICAL SUMMARY:Glasses are ubiquitous materials, including window glass and most plastics. Glasses made up of metallic elements have exceptionally high strength, good compatibility as implants into the human body, and are potentially useful for catalysis and as moving parts in microscale machines. However, atoms in glasses are disordered - jumbled up like the grains in a pile of sand - instead of sitting in a regular ordered array like the atoms in conventional metal alloys like steel. This disorder makes it challenging to understand how the atoms are arranged and how they move with respect to one another. This project investigates the atomic arrangements and atomic motions of metallic glass alloys using a nanometer-diameter beam of high energy electrons in an advanced scanning transmission electron microscope. How the electrons scatter off the sample atoms in the solid state at room temperature reveals how the atoms are arranged. How the electron scattering changes with time when the sample is melted inside the microscope reveals how the atoms move. Understanding atomic arrangements and movements helps materials scientists understand why metallic glasses have such exceptional properties and helps them design new metallic glass materials for new applications. This project also builds capacity for advanced electron microscopy research on metals by creating and distributing software that supports new experiments, and it supports engagement of undergraduate students and the general public with the excitement of seeing atoms - the fundamental building blocks of matter - live in the electron microscope.TECHNICAL SUMMARY:This project supports research into the structure and atomic dynamics of metallic glasses using coherent electron nanodiffraction in the form of fluctuation electron microscopy and electron correlation microscopy. Studies of static structure using fluctuation microscopy and hybrid reverse Monte Carlo modeling are building toward a general structural model of nanometer-scale order in metallic glass alloys. Studies of dynamics in the supercooled liquid state using electron correlation microscopy are testing models of the glass-forming liquid fragility based on spatially heterogeneous dynamics and may provide fundamental insight into the glass transition in metallic alloys. Additional techniques to extract structural information from subtle angular correlations in electron nanodiffraction from glasses are being developed. The project also supports research capacity building by dissemination of software for data acquisition and analysis for fluctuation microscopy and electron correlation microscopy, and outreach activities bringing the excitement of state-of-the-art electron microscopy to the general public.