CAREER: Room Temperature Electrochemical Synthesis of Ordered Intermetallic Nanomaterials

非技术概述：有序金属间化合物（oic）是由两种（或多种）金属元素组成的具有周期性原子排列的金属合金。这些oic在催化、电池和形状记忆合金等技术中发挥着重要作用。然而，它们的应用空间是有限的，因为这些材料只能在高温下制备，通常会破坏对重要材料参数的控制。要使oic的低温合成成为可能，需要对固体材料中原子的运动有精确的了解。该学院早期职业奖（Career）将支持约翰霍普金斯大学Anthony Shoji Hall博士实验室的研究，以研究允许在低温下控制原子运动的途径，从而能够在室温和常压下制备有序的金属间纳米材料。通过在低温下合成这些材料，这项工作将大大拓宽oic的应用空间，因为它现在允许对重要材料参数进行更精细的控制。霍尔博士的实验室将积极地与更广泛的社区分享他们的科学激情和发现，通过参与巴尔的摩市中心的高中和大学的外展活动。第一项活动将利用一个既定的项目，巴尔的摩小学的STEM成就（SABES），鼓励小学生攻读STEM学位。该项目还将创建一个新项目，鼓励乌拉尔大学的高中生攻读STEM学位，并提高乌拉尔大学（本科）研究生从事STEM职业的比例。技术总结：尽管经过数十年的深入研究，OIC纳米颗粒仍未能取代传统的纳米材料，原因有：(1)缺乏低温合成方法，无法克服缓慢的固态扩散速率，从而抑制原子有序；(2)无法调整成分和相以优化预期的应用；(3)缺乏对这些问题进展所需的基本理解。本CAREER提案的目的是通过去除不那么贵重的成分（例如，将PdBi2转化为Pd3Bi，或将CuZn4转化为Cu5Zn8），研究低熔点合金在环境温度和压力下向含有更贵重和更活跃金属的高熔点oic的相变。从这个项目中获得的基本见解将使OIC纳米结构的合理发展与技术相关的应用，并提高我们对电催化条件下材料稳定性的理解。为了了解电化学脱合金介导的相变过程的起源，PI将研究以下目标：(1)阐明熔融温度对体扩散和晶格重组的作用。(2)开发脱合金oic可控成分的合成方法。(3)通过原位光谱方法阐明合金化过程。通过这种电化学介导的相变过程制成的材料将被评估为锂金属电池的阳极，以证明合成方法的实用性。该提案的更广泛影响将鼓励代表性不足的少数民族（URM） K-12学生和（本科）研究生通过参与外展项目在STEM领域追求职业。由于代表性不足，URM的学生无法接触到STEM领域相关的榜样。为了解决这个问题，霍尔博士将参加非正式的“咖啡时间讨论”，作为巴尔的摩地区URM学生（高中生、本科生和研究生）的导师和榜样。霍尔小组还将通过参与巴尔的摩小学STEM成就（SABES）计划，与K-12岁的URM学生合作开展基于探究的科学项目。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。

Non-Technical Summary:Ordered intermetallic compounds (OICs) are metallic alloys with a periodic atomic arrangement of two (or more) metal elements. These OICs play an important role in technologies such as catalysis, batteries, and shape-memory alloys. Their application space is limited, however, because these materials can only be prepared at high temperatures, often eroding control over important material parameters. Making the low-temperature synthesis of OICs possible requires a precise understanding of how atoms move within solid materials. This Faculty Early Career Award (CAREER) will support research in the laboratory of Dr. Anthony Shoji Hall at the Johns Hopkins University to examine pathways that allow for the control of atom movement at low temperatures and thereby enable the preparation of ordered intermetallic nanomaterials at room temperature and atmospheric pressure. By enabling the synthesis of these materials at low temperatures, this work will substantially broaden the application space of OICs because it now allows for more fine control over important materials parameters. Dr. Hall’s laboratory will actively share their scientific passion and discoveries with the broader community by engaging in outreach at inner-city Baltimore high schools and universities. The first activity will leverage an established program, STEM achievement in Baltimore elementary schools (SABES), to encourage elementary students to pursue a degree in STEM. This project will also create a new program to encourage URM high school students to pursue degrees in STEM and to improve the retainment of URM (under)graduate students in STEM careers. Technical Summary:Despite decades of intense research, OIC nanoparticles have failed to replace conventional nanomaterials due to (1) lack of low-temperature synthetic methods that can overcome slow solid-state diffusion rates which inhibits atomic ordering, (2) inability to tune composition and phase to optimize the desired application, and (3) lack of fundamental understanding needed for progress on these issues. The purpose of this CAREER proposal is to examine the phase transformations of low melting point alloys to higher melting point OICs richer in the nobler and more active metal at ambient temperature and pressure by removal of the less noble component (e.g., transforming PdBi2 to Pd3Bi, or CuZn4 to Cu5Zn8) via a process known as dealloying. Fundamental insights from this project will enable the rational development of OIC nanostructures for applications of technological relevance and improve our understanding of material stability under electrocatalytic conditions. To understand the origin of the electrochemical dealloying-mediated phase conversion process, the PI will investigate the following objectives: (1) Elucidate the role of melting temperature on bulk diffusion and lattice reorganization. (2) Develop synthesis methods for controlled compositions of de-alloyed OICs. (3) Elucidate dealloying via in-situ spectroscopic methods. Materials made by this electrochemically mediated phase conversion process will be evaluated as anodes for Li-metal batteries to demonstrate the utility of the synthetic method. The broader impacts of this proposal will encourage underrepresented minority (URM) K-12 students and (under)graduate students to pursue careers in STEM through engagement in outreach programs. URM students lack access to relatable role models in STEM fields because of underrepresentation. To address this issue, Dr. Hall will make himself available for informal “coffee hour discussions” to serve as a mentor and role model for URM students (high school-aged, undergraduate, and graduate students) in the Baltimore area. The Hall group will also work with K-12 aged URM students on inquiry-based scientific projects by participating in the STEM Achievement in Baltimore Elementary Schools (SABES) 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.