Characterization of silver-coated copper particles synthesized by mechanical activation and electroless plating

The effects of mechanical activation on the characteristics of copper and synthesized silver-coated copper powders were investigated. The characterization was carried out using particle size analysis, XRD, BET, SEM, AAS, EDS-map analyses, and electrical resistivity measurements. The obtained results showed that d80 of copper powder changes from 60 to 200 mu m as the milling time increases from 0 to 1 h. Meanwhile, by expanding the milling time to more than 2 h, the d80 of the powders decreased to about 50 mu m. The specific surface area of copper powder increased from 0.04 to 0.21 m2/g for milling duration of 0.5-1 h. The specific surface area reached to a maximum value of 0.3 m2/g for the milling duration of 16 h. Morphological examination of the core-shell particles produced from 4 to 16 h ball-milled copper powder revealed that surface of the copper particles is completely covered with silver. Studies showed that the apparent density of the samples prepared from Cu-Ag core-shell powder and copper powder decreased from 7.2 to 5.8 g/cm3 and from 6.2 to 5.8 g/cm3, respectively, by increasing the ball milling time from 0 to 16 h. The electrical resistivity of the core-shell bulk samples is always constant (0.25 Omega-cm), but the resistivity of copper bulk samples increased (1-5 Omega-cm) with longer milling time (0-16 h).