Production of electrolytic copper powders on rod electrodes with separating layers

Abstract

Finely divided copper deposits were obtained from a sulfate electrolyte containing 30 CuSO~ and 140 g/liter H2SO4. The cathodic current density i c per unit area of the starting smooth electrode surface was 2200 A/m 2. Electrolysis was performed at a temperature of 50  I~ and an electrolyte circulation rate of 70 ml/min. The ease of removal and the rate of buildup of the electrode as a function of the number of stripping operations n were assessed by the weight gain per unit area of the rod electrode surface Am/S. After electrolysis the fine copper deposits were carefully washed free from the electrolyte, stabilized with a 0.05% solution of household soap, and dried in a vacuum desiccator at a temperature of 120-130~ The processing properties of the copper powders were determined by GOST 4960--75 methods. Electrodeposition of finely divided copper on cathodes with separating layers was studied using an end face electrode of surface 2.7 mm 2. Potential vs time curves were recorded with a P-5848 potentiostat at constant predetermined values of current corresponding to coefficients of depletion K d equal to 2, 3, and 4. Here K d = ic/ilim, where ili m is the limiting current density. After the potential vs time curves were recorded, the particle shapes were examined and dendrite lengths measured using an MBS-I microscope at a magnification of 50 diameters. The technique of applying a separating layer from a selenious acid solution as simple and inexpensive, requiring little capital investment and floor space. In our work the copper rod electrodes were first cleaned free from surface contaminants and oxides by pickling them in nitric acid and washing in water, and were then immersed in a 0.5% selenious acid solution at room temperature for 1.5-2.0 min. During this time impervious, strongly adherent coatings of a dark-gray color appeared on the surfaces of the copper electrodes.