Effect of pH localization on microstructure evolution of deposits during aqueous electrophoretic deposition (EPD)

We studied pH localization phenomenon at electrodes under the influence of constant DC voltage during water electrolysis with a view to understand the mechanism of particles consolidation and ordering during aqueous electrophoretic deposition. The pH localization phenomenon was found to depend on applied voltage and initial pH. A pronounced pH localization occurred at higher voltages but the localization was negligible at lower voltages, possibly due to the insufficient water electrolysis. The phenomenon was insignificant when the starting bulk pH was highly acidic or alkaline, but was significant at intermediate pH ranges. During aqueous electrophoretic deposition of monodisperse polystyrene latex spheres, deposition pattern followed a cyclic sequence of aggregation and dispersion of particles at the initial period of time. But after extended period of time, formation of agglomerated particles, multilayers and large clusters was observed. This effect was explained in the light of pH localization.