Production and Characterization of Copper-Niobium Composite Electrocoatings

Copper-niobium composite electrocoatings were obtained by co-electrodeposition in acidic copper sulfate bath containing suspended niobium particles. The amount of incorporated particles was evaluated using a Central Composite Design (CCD) with three factors of control (cathodic current density, stirring rate and particle concentration in the bath) at three levels each. A great influence of particle concentration was observed. The stirring rate also had influence but to a lower extent and the cathodic current density was the least significant factor. The combination, both cathodic current density and particle concentration at the highest levels and stirring rate at the lowest level, led to the highest amount of incorporated particles. The behavior was not linear between the high and low levels for all factors. The roughness of the composites was higher than the pure copper coatings and increased with increasing current density. The microhardness of the composite layers was higher than that of pure copper deposits obtained under the same conditions due to copper matrix grain refinement and increased with the increase of both current density and incorporated particle volume fraction.