Structure and Evolution of Embryos to Crystals in Supercooled Metallic Liquids

过冷金属液体中胚胎的结构和晶体演化

• 批准号: 2204632
• 负责人: Paul Voyles
• 金额: $ 78.04万
• 依托单位: University of Wisconsin-Madison
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2022
• 资助国家: 美国
• 起止时间: 2022-09-01 至 2027-08-31
• 项目状态: 未结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2204632&HistoricalAwards=false
• 关键词: Structure; Evolution; Embryos; Crystals; Supercooled

NON-TECHNICAL ABSTRACTOne of the most common ways metals and other materials are produced is to first create a liquid mixture of the desired elements, then cool the liquid until it freezes into a solid. Starting with a liquid is helpful because it makes elements easy to mix, and the solid can be made the right shape just by pouring the liquid into the right shape container. Understanding how atoms move around in liquids, how they snap together to form a solid, and why they form one kind of solid and not another is a significant problem in materials science and engineering. The very earliest stages of the process, when the solid involves only a few tens of atoms, is particularly hard to study.Recent research on non-metallic materials has shown that textbook models of the earliest stages of freezing can be improved. This project tests whether a similar update is needed for freezing of metals. It uses a nanometer-diameter beam of electrons to probe the arrangements of small groups of atoms and one of the world’s fastest electron cameras to track the atom’s motions as they freeze. Participants in this project are developing new ways to track atoms and are using artificial intelligence to analyze the terabyte-sized data sets produced by the project.This project seeks to advance the fundamental science of transforming metallic liquids into solids, which could benefit metals manufacturing in the US. It also trains students in state-of-the-art methods in materials science and introduces the general public to the excitement of science through live imaging of atoms using powerful electron microscopes.TECHNICAL ABSTRACTNon-classical nucleation is well-established for a variety of systems, including growth of minerals in aqueous solution, growth of protein crystals, and the growth of metal crystals from vapor precursors. This project studies possible non-classical behavior in the nucleation of metal crystals from metallic liquids of similar composition. The approach uses time-resolved coherent electron nanodiffraction with one of the world’s fastest electron cameras. The experiments characterize the structural evolution of crystal embryos through nucleation and growth, other competing liquid structures which do not nucleate crystals, and the influence of spatially heterogeneous dynamics in the liquid state on nucleation kinetics. Approaches from machine learning and computer vision are used to find structurally-relevant patterns in the large nanodiffraction data sets.This project seeks to enhance the understanding of non-classical nucleation from metallic melts, with potential impact on metals manufacturing including casting. Students involved in the project are trained in advanced methods in structural characterization by electron microscopy and in data science applied to materials characterization. The project also brings the excitement of seeing atoms, the basic building blocks of matter, to the general public via live demonstrations of atomic-resolution electron microscopy during public outreach events like the University of Wisconsin-Madison Engineering Expo.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.

生产金属和其他材料的最常见的方法之一是首先制造所需元素的液体混合物，然后冷却液体直到它冻结成固体。从液体开始是很有帮助的，因为它使元素很容易混合，只需将液体倒入正确形状的容器中，固体就可以得到正确的形状。了解原子如何在液体中移动，它们如何断裂形成固体，以及它们为什么形成一种固体而不是另一种固体，是材料科学和工程中的一个重大问题。当固体只涉及几十个原子时，这一过程的最早阶段特别难研究。最近对非金属材料的研究表明，教科书上关于冻结最早阶段的模型可以改进。该项目测试金属冻结是否需要类似的更新。它使用一束纳米直径的电子束来探测一小群原子的排列，并使用世界上最快的电子相机之一来跟踪原子冻结时的运动。该项目的参与者正在开发追踪原子的新方法，并使用人工智能来分析该项目产生的TB大小的数据集。该项目旨在推进将金属液体转化为固体的基础科学，这可能有利于美国的金属制造业。它还培训学生学习材料科学中最先进的方法，并通过使用强大的电子显微镜对原子进行实时成像向普通公众介绍科学的兴奋。技术抽象非经典成核适用于各种系统，包括矿物在水溶液中的生长、蛋白质晶体的生长以及从蒸汽前驱体生长金属晶体。这个项目研究了从类似成分的金属液体中成核金属晶体的可能的非经典行为。该方法使用世界上最快的电子相机之一的时间分辨相干电子纳米衍射。这些实验表征了晶体胚胎通过成核和生长的结构演变，其他不成核的竞争液体结构，以及液体状态下空间非均质动力学对成核动力学的影响。利用机器学习和计算机视觉的方法，在大量的纳米衍射数据集中发现与结构相关的图案。本项目旨在加强对金属熔体非经典形核的理解，并对包括铸造在内的金属制造产生潜在影响。参与该项目的学生接受了电子显微镜结构表征方面的先进方法培训，以及材料表征数据科学方面的培训。该项目还通过在威斯康星大学麦迪逊工程博览会等公共推广活动中现场演示原子分辨率电子显微镜，为公众带来了看到原子的兴奋，原子是物质的基本组成部分。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。