Growth of electrolytic copper dendrites. III: Influence of the presence of copper sulphate

The growth of electrolytic copper dendrites between two coplanar copper discs, 250 μm in diameter, was investigated in oxalic acid medium containing copper sulphate by a technique based on the coupling of electrochemical measurements and microvideo optical in situ observations. The influence of the oxalic acid concentration, the potential difference applied between the two microelectrodes, and a laminar flow perpendicular or parallel to the electric field was investigated on the growth rate of the dendrites and on the short circuit time. Contrarily to solutions of oxalic acid alone, the activation current was diffusion-limited. The growth rate of the dendrites was proportional to the electric field. At the end, the technique was used to study the dendrite growth on a tantalum cathode where a morphology transition was evidenced.