Uniformly coated Cu@Ag core-shell particles with low silver content: Hydroxy acid as a complexing agent with “double-sided adhesive” function

The Cu@Ag core-shell particles are the highly anticipated functional materials in electronic applications which are required to be high electrical conductivity, good thermal properties and low cost. However, it remains a challenge to obtain a completely and uniformly coated Ag shell in low silver content. During the coating process, it is essential to regulate the reduction of Ag+ on the surface of Cu to ensure uniformly silver shell. We developed a strategy to prepare uniformly coated Cu@Ag particles by employing hydroxy acids as complexing agents with "double-sided adhesive" function. Compared to conventional complexing agents, the employed hydroxy acids can not only coordinate with Ag+ but also complex with Cu due to the more carboxyl and hydroxyl groups which act like a "double-sided adhesive", that can pull Ag+ to the surface of Cu, and then accomplish the coating of Ag with replacement and reduction reaction. The impact of different types of hydroxy acids as complexing agents on the coating effect of silver-clad copper powder was investigated when the silver addition was 15 %. Results indicated that the obtained Cu@Ag particles with tannic acid as complexing agent show high coating quality layer with low surface sliver content (11.4 %). Moreover, the obtained Cu@Ag particles exhibit good dispersibility, promising thermal stability and low electrical resistivity (30 μΩ·cm).