Hydrodynamic problems related to the electrodeposition of AuCu/B4C composites

Hydrodynamic actions leading to the electrodeposition of AuCu/B4C composite s have been investigated experimentally and theoretically. Translation and rotation of cylindrical cathodes have been studied. Embedding of particles into disk electrodes rotating at various speeds has been analysed. The depe ndence of volume fraction of embedded particles on fluidisation conditions has been investigated. Higher volume fractions correlate with higher mass t ransport rate to the cathode and are found in points on which flow lines ar e closer to normal to the cathode surface (stagnation points), irrespective ly of the overall flow sign. Hydrodynamic classification of particles diame ters has also been observed: lower fluidisation velocities and tangential ( to cathode surface) fluid flow components correlate with larger particles w hilst higher fluidisation velocities and normal fluid flow components corre late with smaller particles. These effects have been modelled analytically on the basis of a hydrodynamic treatment of interactions among fluid flow, electrode surface and particles. Effects of the cathode roughness - and rel ated local flow conditions - on particle embedding have also been disclosed and explained with the above-mentioned hydrodynamic model. (C) 2000 Elsevi er Science Ltd. All rights reserved.