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

第1部分：非技术摘要技术通常依赖于具有特定性能的材料的使用。由于这些特性是由原子之间的微观相互作用产生的，我们依靠化学家来发现和优化制造它们的配方。例如，用于外科手术工具和医疗植入物的不锈钢依赖于非常特定数量的铬的存在，以防止氧气将铁和镍转化为铁锈。虽然许多材料可以在高温下制造出来，但其中一些——比如钻石——也需要非常高的压力才能形成。与传统化学相比，高压化学的探索要少得多，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、非凡的硬度和奇特的磁性等特性。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，这使得化学家很难调整他们的配方，以便像在常压下反应一样容易地制备材料。这反过来又使研究和调整新发现的高压材料变得更加困难。通过该奖项，由美国国家科学基金会材料研究部固态和材料化学项目和陶瓷项目资助，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调整元素比，使其达到比现有方法更高的精度。该项目支持研究生的专家培训，因为他们开发这些新一代的方法，大大加强了我国未来的科学劳动力。该奖项还支持开发新的教育工具包，为高中生和本科生提供动手接触高压科学的机会，促进他们接触前沿科学学科。高压合成是一个快速发展的领域，它使得在寻找新材料的过程中对未知相空间进行实验探索成为可能。然而，该领域长期存在的一个问题是，在获得极端压力所需的严格限制下，对元素组成的控制很差。这就排除了依赖于精确控制化学计量学的实验，如位点掺杂研究或高产量合成，这反过来又限制了不可恢复相的体积性质和稳定性的研究程度。通过这个CAREER项目，Walsh教授实现并扩展了他在实验室开发的新方法，通过实验来检验长期以来关于高价电子数中排碳化物超导特性的预测，这些预测到目前为止仍然无法测试。除了这些研究，他的团队还研究了化学位点掺杂对不可淬灭高压相稳定场的影响。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技术来制备具有精确化学成分和空间均匀性的微球前体。这些前驱体很容易与金刚石砧细胞方法集成，允许在极端压力下收集x射线衍射和光谱数据。优化高压相性质和可采性的新方法的发现，将为高压相与现有技术基础设施的整合开辟新的领域，极大地增强其潜在的社会影响。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。

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.