CAREER: Understanding the interplay of magnetism, structure and composition in high entropy alloys

该奖项全部或部分由2021年美国救援计划法案（公法117-2）资助。非技术概述：高熵合金（HEA）由五种或五种以上的元素组成，通常以等原子比例存在。HEA显示出令人着迷的新特性，包括高温强度、优异的延展性和高耐腐蚀性，目前正在研究其在飞机、汽车、潜艇和建筑物中的应用。它们的磁性行为也被考虑用于电动汽车和航空等应用，由于高速和工作温度要求，这些应用需要磁性和机械强度。然而，在HEA的磁行为的基本理解方面存在很大的知识差距，因为大多数实验研究都集中在无法访问纳米尺度的体磁化测量上。该项目的重点是理解HEA薄膜的磁性，并通过仔细调整HEA薄膜的成分将其与结构行为相关联。研究活动涉及HEA薄膜的合成和表征，包括基于同步加速器的X射线光谱和X射线成像技术，以表征纳米尺度下的磁行为和结构细节。该项目中开发的HEA系统的微观视图将使材料设计能够用于各种磁性应用，包括发电和输电、永磁体、航空和消费电子产品。教育活动包括向妇女和少数民族本科生介绍美国国家实验室的机会，并与加州戴维斯大学数学工程科学成就（梅萨）和AvenueE计划合作，让社区大学生参与科学，技术，工程和数学。每年的MSE夏令营，实习计划和桥梁倡议将在这个项目下建立。该项目为研究生和本科生提供材料科学，物理学和化学交叉领域的跨学科培训。技术概要：该项目的目标是以非破坏性和特定元素的方式阐明HEA的纳米级磁性和结构行为。基于同步加速器的X射线光谱学和成像技术将用于访问相关纳米尺度的材料响应。具体目标包括：（i）开发HEA薄膜的内聚合成方法和表征以探索多组分相空间，（ii）通过使用X射线光谱技术评估元素特定磁性行为和短程有序之间的关系，以及（iii）通过利用X射线成像技术检查纳米级效应对磁畴结构和微观结构的影响。在这个项目中建立的科学知识将导致HEA薄膜的磁性和结构行为的变革和统一的理解的发展，这将有助于HEA及其特殊性能的原子观的发展。磁性和结构性质之间的关系的全面知识将使理论预测调整HEA中的磁性行为，以实现所需的功能和材料响应。教育活动包括对本科生和研究生进行最先进的沉积和表征工具的培训，包括美国国家实验室的同步辐射表征技术，通过夏令营和桥梁项目的发展，使代表性不足的群体和妇女参与HEA研究和国家实验室。该奖项反映了NSF的法定使命，并通过评估被认为值得支持使用基金会的知识价值和更广泛的影响审查标准。

This award is funded in whole or in part under the American Rescue Plan Act of 2021 (Public Law 117-2).NON-TECHNICAL SUMMARY: High entropy alloys (HEA) are comprised of five or more elements usually in equiatomic proportions. HEA show fascinating novel properties including high temperature strength, exceptional ductility and high corrosion resistance which are currently being investigated for applications in aircrafts, cars, submarines, and buildings. Their magnetic behavior is also being considered for applications such as electric cars and aeronautics where both magnetism and mechanical strength are needed due to high speed and operating temperature requirements. However, there is a wide knowledge gap in fundamental understanding of magnetic behavior of HEA, as most of the experimental studies have concentrated on bulk magnetization measurements which cannot access nanometer lengthscales. This project focuses on understanding magnetic properties of HEA thin films and correlating it with structural behavior by carefully tuning the composition of HEA thin films. Research activities involve synthesis and characterization of HEA thin films including synchrotron based x-ray spectroscopy and x-ray imaging techniques to characterize magnetic behavior and structural details at nanometer lengthscales. The microscopic view of HEA system developed in this project will enable material design for a wide variety of magnetic applications including electrical power generation and transmission, permanent magnets, aeronautics and consumer electronics. Education activities includes introducing women and minority undergraduate students to opportunities at U.S. National Laboratories and collaborating with University of California Davis Mathematics Engineering Science Achievement (MESA) and AvenueE Programs to engage community college students in science, technology, engineering, and mathematics. Annual MSE summer camp, internship program and bridge initiative will be established under this project. This project provides graduate and undergraduate students training in interdisciplinary fields at the intersection of materials science, physics, and chemistry. TECHNICAL SUMMARY: The goal of this projects is to elucidate nanoscale magnetic and structural behavior of HEA in a non-destructive and element-specific manner. Synchrotron-based x-ray spectroscopy and imaging techniques will be utilized to access material response at relevant nanometer lengthscales. Specific objectives include, (i) developing a cohesive synthesis approach for HEA thin films and characterization to explore the multicomponent phase space, (ii) evaluating the relationship between element-specific magnetic behavior and short range ordering by using x-ray spectroscopy techniques, and (iii) examining the impact of nanoscale effects for both magnetic domain structure and microstructure by utilizing x-ray imaging techniques. The scientific knowledge established in this project will lead to development of transformative and unified understanding of magnetic and structural behavior of HEA films which will assist development of an atomistic view of HEA and their exceptional properties. Comprehensive knowledge of the relationship between magnetic and structural properties will enable theoretical prediction for tuning magnetic behavior in HEA to achieve desired functionalities and material response. Education activities include the training of undergraduate and graduate students in state-of-the art deposition and characterization tools, including synchrotron radiation based characterization techniques at U.S. National Laboratories, and engaging underrepresented groups and women in HEA research and National Labs through development of summer camps and bridge program.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.