VISCOSITY EFFECTS IN THIN LAYER ELECTRODEPOSITION

GONZÁLEZ GRACIELA, MARSHALL GUILLERMO, MOLINA FERNANDO, DENGRA SILVINA, MICHEL ROSSO

JOURNAL OF THE ELECTROCHEMICAL SOCIETY

THE ELECTROCHEMICAL SOCIETY (ECS)

Año: 2001 vol. 148 p. 479 - 487

0013-4651

RESUMEN:We present experimental results and a theoretical macroscopic model on the effects of viscosity in thin-layer electrochemical growth. The viscosity was changed through glycerol additions; simultaneous use was made of optical and schlieren techniques for tracking concentration and convective fronts, while pH indicators were used for migratory fronts. The theoretical model describes diffusive, migratory and convective ion transport in a fluid subject to an electric field. The equations are written in terms of dimensionless quantities, in particular, the Migration, Peclet, Poisson, Reynolds and electrical Grashof numbers, which are found to depend on viscosity. Experiments reveal that with increasing viscosity, convection decreases, concentration profiles are less pronounced, while electric resistance and voltage increase. Concentration and convective fronts slow down with viscosity, but their time scaling follows the same law as for solutions without glycerol, only differing by a constant. Moreover, under constant electrical current, an increase in viscosity yields slower deposit front velocities, a more uniform deposit with smaller separation between branches, ie., a change in morphology from more separated compact trees to a more dense fractal-like structure.