CAREER: Harnessing Microfabrication for Chemical Control During High Pressure Synthesis of Non-Equilibrium Carbides

职业：在非平衡碳化物高压合成过程中利用微加工进行化学控制

• 批准号: 2237478
• 负责人: James Walsh
• 金额: $ 69.7万
• 依托单位: University of Massachusetts Amherst
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2023
• 资助国家: 美国
• 起止时间: 2023-03-01 至 2028-02-29
• 项目状态: 未结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2237478&HistoricalAwards=false
• 关键词: CAREER; Harnessing; Microfabrication; Chemical; Control

PART 1: NON-TECHNICAL SUMMARYTechnology often relies on the use of materials with specific properties. Since these properties arise from microscopic interactions between atoms, we depend on chemists to discover and optimize the recipes for making them. For example, the stainless steels used in surgical tools and medical implants rely on the presence of very specific amounts of chromium, which prevents oxygen from converting the iron and nickel into rust. Although many materials can be created using high temperatures, some of them—such as diamond—also require very high pressures to form. High pressure chemistry is much less explored than traditional chemistry, but it has already led to the discovery of many exciting new materials with properties such as lossless electrical conductivity, exceptional hardness, and exotic forms of magnetism. One major obstacle in the field is that the exceedingly small scales required to perform high-pressure reactions make it difficult for chemists to fine tune their recipes for preparing materials as easily as they can for reactions under normal pressure. This in turn makes it much more difficult to investigate and tune the new high-pressure materials being discovered. Through this award, funded by the Solid State and Materials Chemistry program and the Ceramics program in the Division of Materials Research at NSF, Prof. Walsh's research team develops a completely new approach to high-pressure synthesis that uses cutting-edge microfabrication methods to precisely tune elemental ratios to a much higher precision than is possible with current methods. This project supports the expert training of graduate students as they develop these next-generation methods, greatly strengthening our nation’s future scientific workforce. The award also enables the development of new educational kits that provide high school and undergraduate students with hands-on access to high-pressure science, promoting their exposure to forefront scientific disciplines.PART 2: TECHNICAL SUMMARYHigh-pressure synthesis is a rapidly growing field that is enabling the experimental exploration of uncharted phase space in search of novel materials. However, a longstanding issue in the field has been a poor control over elemental composition under the strict constraints required to access extreme pressures. This has precluded experiments that rely on an exact control of stoichiometry, such as site doping studies or high-yield syntheses, which in turn has limited the degree to which the bulk properties and stabilities of unrecoverable phases can be studied. With this CAREER project, Prof. Walsh implements and expands novel methods developed in his laboratory to experimentally examine longstanding predictions surrounding the superconducting properties of high valence electron count mid-row carbides that until now have remained untestable. Alongside these studies, his team also examines the effect that chemical site doping has on the stability fields of unquenchable high-pressure phases. The exquisite control of chemical composition required for these studies is enabled by a completely new approach to sample preparation that uses sputtering and microlithography to prepare micropellet precursors with precise chemical composition and spatial homogeneity. These precursors are readily integrated with the diamond anvil cell method, allowing for the collection of X-ray diffraction and spectroscopic data under extreme pressures. The discovery of new methods for optimizing the properties and recoverability of high-pressure phases would break new ground toward their integration with existing technology infrastructure, greatly enhancing their potential for societal impact.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.

第1部分：非技术概述技术往往依赖于使用具有特定性能的材料。由于这些性质来自原子之间的微观相互作用，我们依赖化学家来发现和优化制造它们的配方。例如，用于手术工具和医疗植入物的不锈钢依赖于非常特定量的铬的存在，这可以防止氧气将铁和镍转化为铁锈。虽然许多材料可以使用高温来制造，但其中一些材料（如金刚石）也需要非常高的压力才能形成。高压化学比传统化学少得多，但它已经导致了许多令人兴奋的新材料的发现，这些材料具有无损导电性，特殊的硬度和奇异的磁性形式。该领域的一个主要障碍是，进行高压反应所需的尺度非常小，这使得化学家很难像在常压下进行反应那样容易地微调他们制备材料的配方。这反过来又使得研究和调整新发现的高压材料变得更加困难。通过该奖项，由固体和材料化学计划和NSF材料研究部的陶瓷计划资助，沃尔什教授的研究团队开发了一种全新的高压合成方法，该方法使用尖端的微加工方法来精确地调整元素比例，其精度比现有方法高得多。该项目支持研究生的专家培训，因为他们开发这些下一代的方法，大大加强了我们国家未来的科学劳动力。该奖项还使开发新的教育工具包，为高中和本科生提供动手接触高压科学，促进他们接触前沿科学学科。第2部分：技术概述高压合成是一个快速发展的领域，它使实验探索未知的相空间，寻找新材料。然而，该领域的一个长期存在的问题是在获得极端压力所需的严格限制下对元素组成的控制不佳。这就排除了依赖于精确控制化学计量的实验，如现场掺杂研究或高产率合成，这反过来又限制了不可恢复相的本体性质和稳定性的研究程度。通过这个职业项目，沃尔什教授实施并扩展了在他的实验室开发的新方法，以实验研究围绕高价电子数中间排碳化物的超导性能的长期预测，直到现在仍然无法测试。除了这些研究，他的团队还研究了化学位点掺杂对不可抑制的高压相的稳定性场的影响。这些研究所需的化学成分的精细控制是通过一种全新的样品制备方法实现的，该方法使用溅射和微光刻来制备具有精确化学成分和空间均匀性的微丸前体。这些前体很容易与金刚石砧室方法集成，允许在极端压力下收集X射线衍射和光谱数据。该奖项反映了NSF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。