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）通常由五种或五种以上的元素以等原子比例组成。HEA具有令人着迷的新特性，包括高温强度、卓越的延展性和高耐腐蚀性，目前正在研究在飞机、汽车、潜艇和建筑中的应用。它们的磁性行为也被考虑用于电动汽车和航空等应用，这些应用由于高速和工作温度要求而需要磁性和机械强度。然而，由于大多数实验研究都集中在体磁化测量上，无法达到纳米尺度，因此对HEA的磁性行为的基本理解存在很大的知识缺口。本项目重点了解HEA薄膜的磁性，并通过仔细调整HEA薄膜的组成将其与结构行为联系起来。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射线光谱学和x射线成像技术，以表征纳米长度尺度上的磁性行为和结构细节。该项目开发的HEA系统的微观视图将使材料设计适用于各种磁性应用，包括发电和传输、永磁体、航空和消费电子产品。教育活动包括向女性和少数族裔本科生介绍美国国家实验室的机会，并与加州大学戴维斯分校数学工程科学成就（MESA）和AvenueE项目合作，让社区大学生参与科学、技术、工程和数学。每年的MSE夏令营、实习计划和桥梁计划将在该项目下建立。该项目为研究生和本科生提供材料科学、物理和化学交叉领域的培训。技术概述：本项目的目标是以非破坏性和元素特异性的方式阐明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获取相关纳米长度尺度的材料响应。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）利用x射线光谱技术评估元素特定磁性行为与短程有序之间的关系；（iii）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对HEA薄膜的磁性和结构行为的变革和统一理解的发展，这将有助于HEA及其特殊性质的原子观的发展。对磁性和结构性质之间关系的全面了解，将有助于对HEA中磁性行为的调整进行理论预测，以实现所需的功能和材料响应。教育活动包括培训本科生和研究生使用最先进的沉积和表征工具，包括美国国家实验室基于同步辐射的表征技术，并通过开发夏令营和桥梁项目吸引HEA研究和国家实验室中代表性不足的群体和妇女。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

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.