Atomistic Imaging of Competition between Surface Diffusion and Phase Transition During the Intermetallic Formation of Faceted Particles
46 Pages Posted: 15 Oct 2019 Publication Status: Review CompleteMore...
To explore the ordering mechanism of facet alloy nanocrystals with randomly distributed atoms, we investigated kinetic and thermodynamic behaviors of ordering phase transition from face-centered cubic (FCC) Pt3Co nanocrystals to L12-Pt3Co intermetallic nanocrystals. It was observed that the ordering occurs from surface and then gradually into the interior in a layer-by-layer mode, involving the competition between two kinds of phase transition modes: long range surface diffusion-induced phase transition (SDIPT) and short range reconstruction-induced body phase transition (RIBPT). The density functional theory (DFT) calculations demonstrated that surface status plays an important role in the thermodynamics and kinetics of the nanoscale ordering transition. With the control of heating process, both of SDIPT and RIBPT modes can be manipulated as well as the morphology of the final product. This work provides a rational design idea about preparing shape-controlled intermetallic nanostructures with excellent electrochemical performance by utilizing the thermal annealing method.
Keywords: In situ atomic STEM images, Nanometallurgy, Surface diffusion, Phase transition of intermetallics
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