Structure and Dynamics of Metallic Glass Alloys

非技术概要：玻璃是一种无处不在的材料，包括窗玻璃和大多数塑料。由金属元素制成的玻璃具有极高的强度，在植入人体时具有良好的相容性，并且在催化和微型机器中的移动部件方面具有潜在的用途。然而，玻璃中的原子是无序的，就像一堆沙子中的颗粒一样杂乱，而不是像钢等传统金属合金中的原子那样有序排列。这种无序使得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。本项目在先进的扫描透射电子显微镜下，利用纳米直径的高能电子束研究金属玻璃合金的原子排列和原子运动。电子如何在室温下从固态样品原子中散射出来，揭示了原子是如何排列的。当样品在显微镜中熔化时，电子散射随时间的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优异的性能，并有助于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，建立了对金属进行高级电子显微镜研究的能力，并支持本科生和公众参与到看到原子（物质的基本组成部分）在电子显微镜下的兴奋中。技术概述：本项目支持使用相干电子纳米衍射技术（以波动电子显微镜和电子相关显微镜的形式）研究金属玻璃的结构和原子动力学。利用波动显微镜和混合反向蒙特卡罗模型对金属玻璃合金的静态结构进行研究，建立了纳米尺度有序的一般结构模型。利用电子相关显微镜对过冷液态的动力学研究是基于空间非均质动力学的玻璃化液体脆性模型的测试，并可能为金属合金的玻璃化转变提供基本的见解。从玻璃电子纳米衍射中细微的角相关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，以及向公众介绍最先进的电子显微镜的外联活动，支持研究能力建设。

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.