A diffusion-deposition competition mechanism to tailor silver deposition on aluminum microsphere surfaces

Abstract

Silver-coated aluminum powder (Al/Ag) are anticipated to replace Ag powder in industrial production. However, the high activity of Al powder and insufficient understanding of the Ag deposition mechanism pose challenges in effectively controlling the Ag deposition process and morphology, thereby restricting which its applications. In this article, a diffusion-deposition competition mechanism is proposed to explain the growth path of Ag atoms on Al surfaces. This mechanism posits that the growth pathway of Ag atom is governed by the ratio between the surface diffusion rate and the deposition rate (Vdiffusion/Vdeposition). Specifically, when surface diffusion dominates (Vdiffusion/Vdeposition≫1), Ag atoms form a conformal layer, whereas the deposition-controlled (Vdiffusion/Vdeposition < 1 or Vdiffusion/Vdeposition≪1), Ag atoms tend to form chains or clusters. Surface diffusion must be considered in regulation crystal growth process. By understanding this mechanism, Ag/Al particles with excellent electromagnetic wave (EMW) absorption properties (RLmin = −37.8 dB, EABmax = 4.4 GHz) can be prepared simply by controlling only the experimental conditions that affect the surface diffusion and deposition rates. The insights gained from the proposed mechanism offer new ideas for the preparation of other noble metals or inorganic materials.