Studies concerning the growth of cadmium dendrites. I. Morphology in alkaline media

The morphology of cadmium dendrites formed during potentiostatic electrodeposition onto nickel and cadmium substrates from cadmate solutions in alkaline supporting electrolyte has been investigated. The morphology is potential dependent for deposition under convective diffusion conditions to a nickel substrate. For 1.05×10^?4 mol dm^?3 Cd(OH) ₄ ^2? /30% KOH solutions, 2D- fern dendrites are observed at an overpotential of ?150mV, needle dendrites at ?200 mV, and large ‘filled-in’ fern dendrites at ?300 mV. Similar results were found at the higher concentration, 2.4×10^?4 mol dm^?3 Cd(OH) ₄ ^2? /50% KOH, but the time taken to grow an equivalent morphology and length were reduced in proportion. Crystalline aggregate dendrites were observed on a cadmium substrate in 1.05×10^?4 mol dm^?3 Cd(OH) ₄ ^2? /30% KOH, becoming more crystalline and well defined with increase in overpotential. A significant induction time of the order 8 h was observed for all deposition onto stationary nickel and cadmium wires. Under the well-defined diffusion conditions at a rotating nickel disc electrode only one morphology, namely small ferns, was observed over a wide range of overpotentials. The current-time behaviour is presented, and the current is shown to have a (time)² dependence, indicative of progressive nucleation of dendrites. The induction time, indicated approximately by the current minima, had decreased significantly.