1991 Volume 99 Issue 1146 Pages 108-113
The electrophoretic deposition method was used to form an alumina layer with a thickness of about 1mm. Alpha alumina powders with average diameters of 0.2 and 0.6μm were dispersed in water at pH 2.5 to provide positive charge. Positively charged alumina particles in the aqueous suspension of 15vol% solid were deposited on a cylindrical carbon electrode by passing direct current of 5-200mA at 50-300V. The weight of the alumina layer was proportional to the deposition time and applied voltage. Electrolysis of the HCl solution occurred together with the electrophoretic deposition of alumina particles. The deposition efficiency calculated from the deposition rate of alumina particles was in the range of 0.13 to 0.15. The density and thickness of the formed alumina layer increased periodically with deposition time. The alumina layers with relative densities of 56-62%, formed from the 0.6μm-alumina powder, were sintered at 1100°-1500°C in air. The densification rate was reduced above 1400°C by large pores (200-500μm).