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

Temple University, Philadelphia PA

Investigators

Abstract

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.