Geometrical Effects on Sintering Dynamics of Cu-Ag Core-Shell Nanoparticles

Understanding of the nanoparticle (NP) sintering mechanism at the atomic scale is of significance for improving various NP applications, such as printable nanoinks, catalysts, and electrode materials in energy devices. In this research, sintering dynamics of Cu-Ag core-shell NPs with various geometries are investigated through molecular dynamics simulations under different temperatures. The evolutions of local crystalline structure, characterized by common neighbor analysis, and potential energy during the sintering are studied to identify the sintering mechanisms. Sintering of two equally sized NPs is divided into three stages according to the shrinkage evolution, and depending on the sintering stage and condition, NP undergoes reorientation for achieving epitaxial layering, plastic deformation, surface diffusion, wetting, and crystallization-amorphization-recrystallization. Although the Cu core is coalescent neither in solid phase nor in surface-premelting-induced sintering, it can enhance the mobility of Ag shell atoms. The size-dependent optimal core radius/shell thickness ratio is proposed to achieve maximum densification and thus maximum bonding strength at room temperature.