TRANSITION FROM GRAVITO- TO ELECTROCONVECTIVE REGIMES IN THIN LAYER ELECTRODEPOSITION

: GONZÁLEZ GRACIELA, MARSHALL GUILLERMO, MOLINA FERNANDO, DENGRA SILVINA

PHYSICAL REVIEW E - STATISTICAL PHYSICS, PLASMAS, FLUIDS AND RELATED INTERDISCIPLINARY TOPICS

THE AMERICAN PHYSICAL SOCIETY (APS)

Año: 2002 vol. 65 p. 1 - 8

1063-651X

RESUMEN: The transition from gravity to electroconvective prevailing regimes in thin-layer electrochemical deposition is analyzed through variations of electrolyte viscosity at constant cell thickness. The distribution of velocity directions at the deposit front is a measure of the relative weight of electroconvection versus gravitoconvection, thus signaling that transition. The experiments are carried out under galvanostatic conditions in convection prevailing regimes. Optical techniques and particle image velocimetry using micron sized particles, allow the tracking of  convective fronts and fluid velocity measurements. These measurements reveal that at low viscosities, buoyancy driven convection prevails; as viscosity increases, electrically driven convection becomes more important, eventually prevailing.  Theoretical and computational modeling presented are based on a macroscopic model describing the coupling of ion transport, electrostatic potential and fluid flow. Theory and simulations predicts that increasing viscosity the Poisson and Reynolds numbers decrease whereas the Peclet and electric Grashof numbers increase, thus making the electroconvective motion relatively more important. This behavior is observed in experiments.