Kinetics of electroplating process of nano-sized ceramic particle/Ni composite

Ultra-fine Al2O3, ZrO2 and SiC powders were co-deposited with Ni by electroplating from a nickel sulfamate bath. An electroplating additive Na3Co(NO2)(6) can promote the co-deposition of the SiC particles, but the Al2O3 and ZrO2 particles can form composite layers without the assistance of the additive. It suggests that the complex ion Co(NO2)(6)(3-) acts as a catalyst during the composite plating. The Guglielmi adsorption mechanism is applied to the electroplating of the ultra-fine SiC with Ni. The ultra-fine SiC particles are more difficult to co-deposit than the coarse SiC, and the rate determination step is controlled by the transferal process of loose adsorption to strong adsorption. The embedded SiC concentration can be increased either by increasing electrical current density or by raising the pH of the suspension to 5. The existence of second ceramic phases in the co-deposited layer changes the grain shape of Ni from columnar to equiaxial, and reduces the average grain size of Ni-matrix to 50 nm. (C) 2002 Elsevier Science B.V. All rights reserved.