LEAPS-MPS: Interrogating Negative Thermal Expansion in Earth-Abundant Oxide Materials

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。热膨胀，即材料在加热或冷却时改变形状的方式，是一种需要理解和控制的重要特性。人们每天依赖的许多物体（如建筑材料、航空部件等）如果热膨胀不匹配，就会更容易磨损或失效，从而在世界上造成更多的浪费和更高的成本。虽然许多材料在加热时会膨胀，但有些材料在加热时会收缩，这对研究很重要。因此，了解如何控制这些特性以便设计新型材料是很重要的。在这个leap - mps项目中，富勒顿加州州立大学的Joya Cooley教授将专注于理解为什么某些由地球上丰富的元素组成的材料在加热时收缩而不是膨胀。该研究主要在一所本科院校进行，本科生将接受各种合成和表征技术的培训。具体来说，来自历史上缺乏教育背景的学生将被招募参与这个项目，并将通过当地的外展向公众传播研究结果，让参与的学生成为未来来自历史上缺乏教育背景的科学家的榜样。此外，这种地方推广将有助于提高公民科学、公众科学素养和公众对材料化学的整体兴趣。该leap - mps奖项旨在了解导致材料技术相关负热膨胀（NTE）的结构和化学驱动力。这项工作将考察材料结晶为金属焦磷酸盐和焦钒酸盐（A2B2O7）的局部和远程结构，这些材料使用廉价和容易获得的元素（例如，A = Mg, Mn, Co, Ni, Cu; B = P， V）。目标是实现以下目标：(1)研究A位和B位元素的作用及其对母体晶体结构的影响；(2)了解A、B位点元件的作用及其对NTE调节温度和范围的作用。通过创建固溶体来改变焦磷酸盐（A2P2O7）和焦钒酸盐（A2V2O7）材料中的金属(A)和非金属(B)特性的能力为揭示NTE的结构驱动因素提供了丰富的探索可能性。通过创建具有极端性质的端元之间的固溶体，这项工作将试图阐明对O运动至关重要的结构和化学变量，从而实现NTE的系统控制。该项目将利用(a)高分辨率结构技术，如同步加速器衍射；(a)对O等轻元素敏感的技术，如中子衍射；(c)以及对原子运动提供局部理解的技术，如温度依赖显微镜。本科学生将接受固态化学技术方面的培训，包括在国家实验室进行远程或动手实验的机会。历史上服务不足的学生将被招募为该项目的一部分，并将参与当地的外展活动，以提高公众的科学兴趣和素养。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 SummaryThermal expansion, the way materials change shape when you heat or cool them, is an important property to be able to understand and control. Many objects that people rely on every day (i.e. building materials, aerospace parts, etc.) can wear out or fail more easily if their thermal expansion is not matched well, thus creating more waste and higher costs in the world. While many materials expand as you heat them, some materials shrink as you heat them and are important to study. Therefore, it is important to understand how to control these properties so that new types of materials can be engineered. With this LEAPS-MPS project, Professor Joya Cooley at California State University, Fullerton, will focus on understanding why certain classes of materials which consist of earth-abundant elements shrink instead of expanding upon heating. The research is conducted at a primarily undergraduate institution where undergraduate students will be trained in a variety of synthetic and characterization techniques. Specifically, students from historically underserved backgrounds will be recruited to work on this project and will disseminate findings to the public through local outreach, allowing participating students to serve as role models for future scientists from historically underserved backgrounds. Furthermore, this local outreach will work to increase the amount of citizen science, public scientific literacy, and overall public interest in materials chemistry.Technical SummaryThis LEAPS-MPS award is aimed at understanding structural and chemical driving forces that lead to technologically relevant negative thermal expansion (NTE) in materials. This work will interrogate local and long-range structure in materials crystallizing as metal pyrophosphates and pyrovanadates (A2B2O7) using inexpensive and readily accessible elements (e.g., A = Mg, Mn, Co, Ni, Cu; B = P, V). The goal is to achieve the following: (1) investigate the role of A and B site elements and their influence on parent crystal structure; (2) understand the role of A and B site elements and their role in tuning temperature and range of NTE. The ability to vary metal (A) and nonmetal (B) identities in pyrophosphate (A2P2O7) and pyrovanadate (A2V2O7) materials by creating solid solutions provides a wealth of exploration possibilities for uncovering the structural drivers for NTE. By creating solid solutions between end members with properties at the extremes, this work will seek to elucidate the structural and chemical variables important to O motion that results in systematic control of NTE. This project will make use of (a) high resolution structural techniques, such as synchrotron diffraction; (a) techniques sensitive to light elements like O, such as neutron diffraction; (c) and techniques that provide a local understanding of atom motion, such as temperature dependent microscopy. Undergraduate students will be trained in solid-state chemistry techniques, including the opportunities to work with national laboratories for remote or hands-on experiments. Historically underserved students will be recruited to be part of this project and will engage in local outreach to increase public scientific interest and literacy.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.