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Electroless Ag-coating of cenosphere particles is demonstrated in the present investigation. The electroless Ag-coating process is modified by replacing the conventional pretreatment and sensitization steps by only using a surface hydroxylation step with NaOH hydroxylating agent to simplify the steps and reduce the overall cost of the coating process. Furthermore, the activation and electroless plating steps are merged into one step. The cenosphere particles are characterized by scanning electron microscope (SEM), energy dispersive x-ray spectroscopy (EDX), X-ray diffraction analysis (XRD), and fourier transform infrared (FT-IR) before and after the coating process. The relatively uniform and continuous coating is obtained under the given coating conditions. The possible mechanism of electroless Ag-coating of cenosphere particles utilizing surface hydroxylation of cenospheres is suggested.

Electroless silver coating on copper powder and its effects on oxidation resistance were investigated by varying the fabrication parameters. Using acetylacetone (C5H8O2) as chelating reagent, silver-coated copper powder was fabricated by displacement reaction method. In the process, acetylacetone forms chelating compound with Cu 2+, which prevent the formation of [Cu (NH3)4]2+. Therefore, Ag + can be reduced continully and deposited on the surface of copper particles. As-coated copper particles were characterized using x-ray diffraction (XRD), scanning electron microscopy (SEM) and x-ray energy dispersive spectroscopy (EDS). The oxidation resistance of silver coated copper powder was investigated by gravimetric method. It was found that a fairly continuous silver layer was formed on the surface of copper powder by the electroless type of substitution plating. When the silver content reached 10 wt. %, silver was homogeneously distributed around the copper particles and few free silver particles were detected. The results showed that the silver coated copper powder with the best oxidation resistance was prepared at 40°C and the C5H8O2/AgNO3 molar ratio was 1:1.