Cobalt cementation in an ethanol-water system: Kinetics and morphology of metal aggregates

A cobalt cementation process in ethanol-water solvent at different temperatures is presented. A new model is proposed which takes into account the depletion of the less electropositive metal by a shrinking core technique. The model comprises a system of two ordinary differential equations whose dependent variables are the concentration of the cation undergoing cementation and the radius of the sacrificial metal particles. An analytic solution is obtained and a comparison between the present model and the traditional one is proposed. The model is validated by experimental data regression to investigate the cementation kinetics at different temperatures, and the relevant activation energy suggests the onset of a chemical control regime for all experimental runs. Finally, the cemented phase is morphologically and chemically characterized, and the size distribution of the relevant metal aggregates is determined by means of both dynamic light scattering in solution and atomic force microscopy after drop casting onto a solid substrate. © 2012 American Chemical Society.