Regulation of anti-oxidation behavior in silver-coated copper powders via cobalt modification†

Abstract

The anti-oxidation of silver-coated copper (Cu@Ag) powders is expected to improve as a thick silver (Ag) shell forms. A novel approach involving cobalt modification was disclosed with the goal of improving Ag deposits, and the impact of cobalt modification on the anti-oxidation of Cu@Ag (cobalt-modified, CM) powders was mainly revealed. Cu@Ag (CM) powders were found to have an Ag shell thickness of approximately 635 nm, which was significantly thicker than that of Cu@Ag (non-cobalt-modified, NCM) powders (∼545 nm). The deposition of Ag and the core–shell structure of Cu@Ag (NCM; CM) powders were confirmed by field emission scanning electron microscopy (FESEM), energy dispersive spectroscopy (EDS), and X-ray diffraction (XRD). The effects of cobalt modification on the morphology and anti-oxidation of Cu@Ag powders were investigated using scanning electron microscopy (SEM), high-temperature tube furnace testing, and thermogravimetric-differential scanning calorimetry (TG-DSC). According to the results, the Cu@Ag (NCM) powders were spherical, while the Cu@Ag (CM) powders exhibited an irregularly flocculent morphology. Due to the protection provided by the Ag shells, the initial oxidation temperature of both Cu@Ag (NCM) and Cu@Ag (CM) powders increased to 244 °C. Cu@Ag (CM) powders exhibited a lower oxidation weight gain at high temperatures compared to Cu@Ag (NCM) powders. The element content in the plating solution was determined using inductively coupled plasma optical emission spectrometry (ICP-OES), and the results indicated that cobalt modification could facilitate Ag deposition in electroless Ag plating. The proposed cobalt modification method not only improves the resistance of Cu@Ag powders to oxidation but also decreases the amount of Ag(I) waste in the solution.