Grain-boundary engineering is pivotal to fully utilize the mechanical, electrical, and thermal-transport properties of various materials. However, current methods in metallurgy rely almost exclusively on top-down approaches, making precise grain-boundary engineering, especially at nanoscale, difficult to achieve. In this talk, I will discuss about our recent studies about pressure processing of different types of nanocrystals. Importantly, I will focus on the discovery of a novel method to produce tailored grain-boundary conditions with nanoscale precision from colloidal metal nanocrystals through surface treatment followed by a pressure-sintering process. The resulting bulk grain-boundary materials (which we call ‘‘nanocrystal coins’’) possess a metal-like appearance and conductivity while inheriting the original domain features of the nanocrystal building blocks. Nanoindentation measurements confirmed the superior mechanical hardness of the obtained materials. Further, we use this method to fabricate, for the first time, a single-component bulk metallic glass from amorphous palladium nanoparticles. Our discovery may spur the development of new materials (through pressure-treatments) with functionality crucially depends on the domain configuration at nanometer scale, such as superhard materials, thermoelectric generators, and functional electrodes.

Bulk grain-boundary materials through pressure-processing of nanocrystal

ACS Spring 2022

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