Ultra-Fast Heating Process of Cu-Pd Bimetallic Nanoparticles Unraveled by Molecular Dynamics Simulation

This paper investigates the ultra-fast heating process of Cu-Pd bimetallic nanoparticles from an atomic-scale perspective, which is essential for laser manufacturing processes, such as laser cladding and selective laser melting. The behavior of high surface ratio nanoparticles during these processes is strongly influenced by their properties and the heating process, which is governed by atomic dynamics. Previous studies have mainly focused on the combination process in pure metallic nanoparticles under slow or isothermal heating, but this work demonstrates that the ultra-fast atomic dynamic process between bimetallic nanoparticles differs significantly. Specifically, in Cu-Pd nanoparticles, the combination process is primarily dependent on the surface atomic motion of the lower melting point particles rather than plastic deformation in the grain boundary between particles. Moreover, the ultra-fast heating process is size-dependent. For small nanoparticles, the atomic kinetics exhibit two different mechanisms depending on temperature: Low-temperature jointing is controlled by localized atomic rearrangement, while high-temperature coalition is governed by the atomic flow of surface atomic melting in the low-temperature melting particle. The combination mechanism is the same for large particles as it is for small particles at high temperatures. The findings of this study provide important insights into the behavior of bimetallic nanoparticles during ultra-fast heating and can inform the development of coat and lubricant.