Fast coalescence of metallic glass nanoparticles

Yuan Tian,Mingwei Chen,Pan Liu,Zhen Lu,Shuangxi Song,Wei Jiao,Akihiko Hirata

doi:10.1038/s41467-019-13054-z

Abstract

The coarsening of crystalline nanoparticles, driven by reduction of surface energy, is the main factor behind the degeneration of their physical and chemical properties. The kinetic phenomenon has been well described by various models, such as Ostwald ripening and coalescence. However, the coarsening mechanisms of metallic glass nanoparticles (MGNs) remains largely unknown. Here we report atomic-scale observations on the coarsening kinetics of MGNs at high temperatures by in situ heating high-resolution transmission electron microscopy. The coarsening of the amorphous nanoparticles takes place by fast coalescence which is dominated by facet-free surface diffusion at a lower onset temperature. Atomic-scale observations and kinetic Monte Carlo simulations suggest that the high surface mobility and the structural isotropy of MGNs, originating from the disordered structure and unique supercooled liquid state, promote the fast coalescence of the amorphous nanoparticles at relatively lower temperatures.

Highlights

The coarsening of crystalline nanoparticles, driven by reduction of surface energy, is the main factor behind the degeneration of their physical and chemical properties
Our experiments reveal that the high-temperature coalescence of metallic glass nanoparticles (MGNs), dominated by facetfree surface diffusion, is much faster than that of crystalline particles, benefiting from the isotropic disordered structure of glasses and unique supercooled liquid state
The structures of the as-deposited nanoparticles were investigated by high-resolution scanning transmission electron microscopy (TEM) (STEM) with a high-angle annular dark field (HAADF) detector (Fig. 1c)

Summary

Introduction

The coarsening of crystalline nanoparticles, driven by reduction of surface energy, is the main factor behind the degeneration of their physical and chemical properties. Atomic-scale observations and kinetic Monte Carlo simulations suggest that the high surface mobility and the structural isotropy of MGNs, originating from the disordered structure and unique supercooled liquid state, promote the fast coalescence of the amorphous nanoparticles at relatively lower temperatures. Metallic glass nanoparticles (MGNs) with a small size and high surface-volume ratio are relatively easy to be synthesized by traditional powder metallurgy and sputtering and have attracted increasing attention for applications in additive manufacturing, composite reinforcement, catalysis, and biomedicine[7,8,9,10,11,12] In these applications, nanoparticle coarsening is essential in the sintering kinetics and structural and functional retention. The atomic observations and kinetic Monte Carlo (KMC) simulations demonstrate that the atomic structure of nanoparticles plays an important role in particle coalescence, in addition to the conventional wisdom of particle size and morphology

Methods

Results

Conclusion