Synthesis of Cu-Ag core-shell particles: Study on cover silver homogeneity

Cu-Ag particles with homogeneous cover-silver layer were synthesized by electroless plating of copper particles with silver sulfate using eco-friendly sodium citrate (SC) as reducing agent, dispersant and chelating agent in an aqueous system. The influences of sodium citrate/Cu and sodium citrate/Ag ratios on Ag coatings of Cu powders were investigated. Ag formed a dense coating on the surface of Cu powders at a molar ratio of SC/Cu=0.25/1 and SC /Ag=8/1. SEM (scanning electron microscopy) showed a uniformity of Ag coatings on Cu powders. SEM images and EDS (The energy dispersed spectrometry) analyses also revealed that Cu cores were covered by Ag shells on the whole. The measurement of oxidation resistance of Cu-Ag particles shows closer resistivity (6.25×10-4Ω‧cm) than pure Ag (9.25×10-5Ω‧cm) without CuO (-1 1 1) and Cu2O (1 1 1) and peaks were detected after heat-treatment at 350°C for 4 h.   Key words: Cu-Ag particles, electroless plating, oxidation resistance.