MODELING AND ANALYSIS OF THE CEMENTATION PROCESS ON A ROTATING-DISK

By introducing the concept of ''surface activation'', the kinetic model of cementation on the metallic rotating disk limited by either mass transfer or surface reaction was formulated. This work is an extension of the two-step model and detailed discussion is presented. Furthermore the model was verified with the experimental data of the cementation of copper ions on aluminum disks made from pure aluminum foils. Before and after cementations, aluminum disks were also characterized thoroughly by SEM and X-ray diffraction. The results show that high-purity copper is extracted from the solution. The change in the morphology of the resultant copper deposits agrees with the change in the kinetic results. The copper dendrites protrude into the diffusion boundary layer and increase the mass transfer rates. The finer dendrites may have a better agitating effect which increases the rate of mass transfer. Since the induction time decreases with the increase of the specific rate constant, the induction time is dominated by the time needed for the ''critical deposit mass'' to be completely grown.