Influence of Electrolysis Conditions on the Grain Size of Deposited Copper Powder.

Copper powder was deposited electrolytically from acidified solutions of copper sulfate. The electrolyses were performed under potentiostatic conditions in a potential range corresponding to the limiting currents for cathodic reduction of Cu**2** plus ions in the solutions under consideration. A study was made of the influence of the cation deposition potential, the system geometry and the mixing rate, the temperature, the Cu**2** plus ion concentration, and the cathode material on the grain size of the copper powder. It was found that under conditions of natural convection the parameter which most affects the grain size is the deposition potential, whereas in a system with forced convection the effect of the mixing rate begins to predominate. The effect of the other electrolysis parameters, with the exception of the Cu**2** plus ion concentration, on the grain size of the electrolytic copper powder is less important. On the basis of these results, the requirements which must be fulfilled by an industrial electrolytic cell for the production of copper powder with a controlled grain size are formulated.