Cu@Ag bimetallic powders with a layered Ag shell via ascorbic acid-mediated interfacial regulation

Driven by the demand for cost reduction and enhanced performance in electronic applications, Cu@Ag bimetallic powders have attracted considerable attention as functional materials, requiring high electrical conductivity, excellent stability and environmental durability. This study uses ascorbic acid as the reducing agent and aqueous ammonia as the pH adjuster to prepare Cu@Ag bimetallic conductive powders under various ascorbic acid concentrations, pH values and temperature conditions. The results show that the powders form a protective silver shell through a layered growth mode. Crystal structure analysis reveals that the silver shell consists of hexagonal {111} planes and square {100} planes. These results suggest that the formation of this morphology may be associated with the synergistic effects of reduction kinetics and surface adsorption of ascorbic acid. Under alkaline conditions, a sufficient amount of ascorbic acid provides a strong reduction driving force and high nucleus supersaturation. In particular, its synergistic interaction with ammonia regulates Ag-species complexation, nucleation, and surface growth, thereby favoring the formation of layered structures. Non-equilibrium kinetic analysis and weatherability tests demonstrate that the as-prepared powders exhibited excellent oxidation resistance, short-term hygrothermal stability and acid resistance under the tested conditions. The conductive film exhibits a low resistivity of 70 μΩ·cm, 60% lower than that of the pure Cu film. This work mitigates the limitations in weatherability and conductivity caused by non-uniform and incomplete coatings through compositional and structural regulation. Meanwhile, the strategy improved Ag utilization efficiency and achieved enhanced performance at reduced Ag loading, providing a viable route for the controllable fabrication of low-cost, high-performance Cu@Ag conductive powders.