| The curvature-driven coarsening behavior of single-phase particles on a substrate, or second-phase particles in a matrix, has been studied extensively, both theoretically and experimentally. In contrast, no such body of knowledge exists regarding the particle size evolution of two different phases on a substrate, or in a matrix, e.g., binary metallic mixtures. The purpose of this study is to look at the particle size dynamics of nanocrystal mixtures of Au and Ag on heating.; Nanocrystals of pure Au and pure Ag were sequentially deposited on to amorphous carbon films by thermal evaporation into an inert atmosphere. The as-deposited nanocrystals ranged in size from 0.5 nm to 31.0 nm. The nanocrystals were then heated and the evolution of size and composition were determined using a transmission electron microscope (TEM).; This study showed it is possible to create mixtures of Au and Ag nanocrystals by thermal evaporation with a minimal amount of alloying during the exaporation process. The particle size distribution resulting from thermal evaporation into an inert atmosphere can be described and analyzed with a Lognormal distribution. The mixtures of nanocrystals grow at a lower rate than populations with a single element. The rate of composition change for individual particles in nanocrystal mixtures is proportional to the deviation from the sample average composition. Chemical mixing plays a major role in determining the growth behavior of nanocrystal mixtures with time. It is possible to have large particles of Ag shrink on heating, when small Au particles are present. Gold particles act as a template for the final particle size distribution in Au-Ag mixtures. |
