EXPERIMENTAL-EVIDENCE FOR HOMOCLINIC CHAOS IN AN ELECTROCHEMICAL GROWTH-PROCESS

Experimental investigations of galvanostatic electrochemical growth processes in steady thin layer electrolytes are reported. For some control parameter values, the measurement of the cell potential versus time provides periodic and aperiodic oscillations. The deterministic character of these potential signals is demonstrated using standard dynamical systems theory tools such as time-delay phase portrait reconstructions, Poincare maps and one-dimensional maps. A transient period-doubling transition is described. The homoclinic nature of the chaotic behavior is emphasized. The origin of the spatio-temporal behavior is discussed in terms of the competition between the electrochemical process (reduction of metallic ions) and the transport processes (migration, diffusion and convection). Analysis of video images shows that the oscillations in growth rate are in phase across the entire cell width (up to 40 mm) and are in phase with the oscillations in the cell potential.