Preparation of silver-coated copper powder and its oxidation resistance research

Electroless silver coating on copper powder and its effects on oxidation resistance were investigated. In general, silver-coated copper powder is prepared by an electroless type of substitution plating making use of the substitution reaction between copper and silver. However, [Cu (NH3)4]2+ is produced during the electroless plating process and absorbed onto the surface of the copper particles, which prevent substitution reactions proceeding. In the new electroless plating process, RE-608 copper-specific extractant was used as chelating reagent to formed chelate compound with Cu2+ and the chelate compound was extracted to organic phase, which confirmed substitution reaction to be proceeding. As-coated copper particles were characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS). When the silver content reached 6.86 wt.%, silver was homogeneously distributed around the copper particles and few free silver particles were detected. The results indicated that the properties of oxidation resistance were improved with increasing the dosage of RE-608 copper-specific extractant and reaction time, and with decreasing AgNO3 concentration. It was also found that the optimum reaction temperature was 80 °C.