Microwave-enabled Manufacturing of Single-phase, Multi-principal Element Alloy Nanoparticles

这笔赠款支持在单相、多主元素合金(MPEA)纳米颗粒的加工过程中贡献新知识的研究。多主元素合金，如高熵合金，因其特殊的性能而在技术上具有重要意义。将不同的主要元素均匀混合，可产生纯元素纳米颗粒所不具备的新特性。大多数主要元素在环境温度下是不相容的，这导致在使用通常缓慢的传统加热和冷却方法制造纳米粒子时，不同元素在纳米粒子中分离。该奖项支持开发微波闪光或快速加热和冷却方法的基础研究，以制造多主元素合金纳米颗粒。闪光加热可使不同元素在高温下均匀混合。闪速冷却使均匀混合的元素迅速冻结，形成单相多主元素合金纳米颗粒。多主元素合金纳米粒子的成功制造为探索这些纳米粒子在高性能催化、结构工程和添加剂制造中的新特性和应用开辟了全新的机会。因此，这项研究的结果有利于美国的经济和社会。这项研究涉及使用国家实验室的大型设施，培训学生成为先进材料制造和表征方面的专家。更广泛地说，开展这项研究使学生，特别是那些来自代表人数不足的群体的学生，掌握多学科知识，并为包括先进制造业在内的广泛行业培养一支经过技术培训的劳动力队伍。利用微波对纳米合金进行快速加热和冷却，可以克服传统加热和冷却方法的局限性。然而，要实现不同组成的单相多主元素(MPEA)纳米颗粒的制备，还需要克服围绕纳米合金产生高温度梯度的科学和技术障碍。该技术涉及将反应系统暴露在高功率微波脉冲下，该脉冲选择性地加热限制在胶束小泡(金属盐)中的金属合金纳米颗粒，以在分散在微波透明溶剂中的胶束小泡的薄壁上产生极高的温度梯度。随后的快速熔化和凝固导致了单相过饱和纳米颗粒。利用高能同步小角X射线散射(SAXS)和广角X射线散射(WAXS)原位研究了微波脉冲辐射下MPEA纳米粒子的复杂微结构演化动力学。该研究团队制造了催化和难熔金属的MPEA纳米颗粒，并探索了它们在催化中的应用，例如，二氧化碳选择性电化学还原为乙醇和氨合成，以及添加剂制造，重点是难熔金属纳米颗粒的3D打印。这一奖项反映了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。

This grant supports research that contributes new knowledge in the processing of single-phase, multi-principal element alloy (MPEA) nanoparticles. Multi-principal element alloys such as high entropy alloys are technologically important because of their extraordinary properties. Mixing different principal elements uniformly results in new properties that do not exist in nanoparticles made of pure elements. Most principal elements are immiscible at ambient temperatures, which results in the segregation of different elements in the nanoparticles when they are manufactured using conventional heating and cooling methods that are usually slow. This award supports fundamental research to develop a microwave-enabled flash or rapid heating and cooling method for the manufacture of multi-principal element alloy nanoparticles. Flash heating enables uniform mixing of the different elements at high temperatures. Flash cooling rapidly freezes the uniformly mixed elements to form single-phase multi-principal element alloy nanoparticles. Successfully manufacturing multi-principal element alloy nanoparticles opens an entirely new opportunity to explore novel properties and applications of these nanoparticles for high-performance catalysis, structural engineering, and additive manufacturing. Therefore, the results of this research benefits the U.S. economy and society. This research involves the use of large-scale facilities at national laboratories that train students to become specialists in advanced materials manufacturing and characterization. More broadly, performing this research educates students, especially, those from underrepresented groups, with multidisciplinary knowledge and prepares a technically trained workforce for a wide-range industries including advanced manufacturing. The microwave-enabled flash heating and cooling of nanometer-sized alloys can overcome the limitations of conventional heating and cooling methods. However, scientific and technical barriers of creating high temperature gradients around nanometer-sized alloys are yet to be overcome to realize the manufacturing of single-phase multi-principal element (MPEA) nanoparticles of different compositions. The technique involves exposing a reaction system to a high-power microwave pulse that selectively heats metal alloy nanoparticles confined in micelle vesicles (metal salts) to generate an extremely high temperature gradient across the thin walls of the micelle vesicles dispersed in a microwave transparent solvent. The ensuing rapid melting and solidification results in single-phase super-saturated nanoparticles. In situ, high-energy synchrotron small-angle x-ray scattering (SAXS) and wide-angle x-ray scattering (WAXS) are used to study the complex microstructure evolution kinetics in the MPEA nanoparticles under the radiation of a microwave pulse. The research team fabricates MPEA nanoparticles of catalytic and refractory metals, and explores their applications in catalysis, e.g., selective electrochemical reduction of CO2 to ethanol and ammonia synthesis, and additive manufacturing, focusing on 3D printing of refractory metal nanoparticles.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.