Effect of Ion Concentration on Viscosity of Doped Alumina Suspensions for Electrophoretic Deposition

Electrophoretic Deposition (EPD) weight is highly affected by electrophoretic mobility of powders in suspension. In theoretical aspect, electrophoretic mobility is influenced by suspension viscosity in opposite direction, and increasing in viscosity can decrease electrophoretic mobility and consequently can decrease EPD weight. In non-aqueous suspension, viscosity is determined by ion strengths of suspension. In this study, viscosity, electrical conductivity and deposit weight were determined for electrophoretic deposition (EPD) of alumina suspended in ethanolic solvent of Y-, Mg-, Ce- and La- salts, prepared in dispersant level between 350 to 1350 ppm. The concentration of XCly, (X: Mg, Y, Ce and La), is also found to be a critical factor to control the viscosity. It is shown that the deposit weight is influenced by precursor concentration, and on the other hand, electrical conductivity, viscosity or the pH of the suspension cannot change the yield. All concentrations interactions, except Mg × Ce concentration are significant in ANOVA model. The viscosity of suspension reached 2.5 mPa.s with Mg-, Y-, La- and Ce- decreased to 100, 100, 100 and 0 ppm in low iodine concentration (400 ppm). The reason is that heavier cations can be adsorbed to alumina surface with iodine adsorption, but lighter Mg- cations can be adsorbed under the influence of OH groups excited on alumina surface.