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(或更多)金属元素组成的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，它们的应用空间有限，因为这些材料只能在高温下制备，往往会侵蚀对重要材料参数的控制。要使OIC的低温合成成为可能，需要精确了解原子在固体材料中的运动方式。该学院早期职业奖将支持约翰·霍普金斯大学Anthony Shoji Hall博士实验室的研究，以检查允许控制低温下原子运动的途径，从而能够在室温和大气压下制备有序的金属间纳米材料。通过能够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的材料参数进行更精细的控制。霍尔博士的实验室将积极与更广泛的社区分享他们的科学热情和发现，参与巴尔的摩市中心的高中和大学的推广活动。第一项活动将利用巴尔的摩小学(SABES)已建立的STEM成就计划，鼓励小学生攻读STEM学位。该项目还将创建一个新的计划，以鼓励URM高中生攻读STEM学位，并改善URM(本科)研究生在STEM职业生涯中的留住。技术综述：尽管经过几十年的密集研究，但OIC纳米颗粒未能取代传统的纳米材料，原因是：(1)缺乏能够克服阻碍原子有序化的缓慢固态扩散速率的低温合成方法；(2)无法调整成分和相以优化所需的应用；以及(3)缺乏在这些问题上取得进展所需的基本了解。这份职业建议书的目的是研究低熔点合金在常温常压下通过去合金化过程去除不太贵重的成分(例如，将PdBi2转变为Pd3Bi，或将CuZn4转变为Cu5Zn8)，从而将较高熔点的OIC转变为更高熔点的OIC。这个项目的基本见解将使OIC纳米结构的合理开发应用于技术相关，并提高我们对材料在电催化条件下的稳定性的理解。为了了解电化学脱合金过程的起源，PI将研究以下目标：(1)阐明熔化温度对体扩散和晶格重组的作用。(2)开发非合金OIC受控成分的合成方法。(3)用原位光谱分析方法阐明脱合金化。通过电化学介电相变过程制备的材料将作为锂金属电池的负极进行评估，以演示合成方法的实用性。这项提案的更广泛影响将鼓励未被充分代表的少数族裔(URM)K-12学生和(以下)研究生通过参与外联计划在STEM追求职业生涯。由于代表性不足，URM学生在STEM领域无法接触到相关的榜样。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加巴尔的摩小学(SABES)的STEM成就计划，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。

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.