A model is developed for deposition during the electrophoretic deposition (EPD) process. It suggests that ions that move with the charged particles in suspension are depleted at the depositing electrode, locally changing the pH toward the isoelectric point (pHiep) to give coagulation. The variation of zeta (zeta) potential is modeled via chemical‐equilibrium and surface‐adsorption isotherms. The model successfully fits the experimental data for Al2O3 particles in ethanol when the Freundlich surface‐adsorption isotherm is assumed. Calculations predict the co‐ion concentration gradient as a function of location within the suspension, and the deposition time and its role in the coagulatoin process during EPD.

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The process of submonolayer formation during the electrophoretic deposition (EPD) of colloidal films of micrometersized (diameter Ϸ 0.5 m) silica particles on a silicon wafer has been observed as a function of deposition time. The process of nucleation and growth of the silica monolayer is compared with that of atomic film growth (10000 times smaller scale) via molecular-beam epitaxy (MBE), and for the first time, a striking similarity between the two growth processes is observed. Likewise in the atomic growth process via MBE, the entire nucleation, growth, and aggregation process during EPD of silica particles can be broadly classified into two regions. At low surface coverage when silica particles are deposited outside of clusters, diffuse randomly, and stick to a cluster on touching them, the mechanism of growth in this region follows diffusion-limited aggregation (DLA) and the fractal dimension of the two-dimensional clusters is found to be close to 1.65. Later on, as the clusters grow in size, deposition of particles inside the clusters become important and clusters become more and more compact, resulting in a dense, close-packed, and homogeneous monolayer. This region is termed a consolidation region, and a change in fractal dimension from 1.65 toward 2 with increasing surface coverage has been observed.