Abstract
A fine α-alumina powder was coated by SiO2 ultra fine particles with a diameter of nano-meters. SiO2 by hydrolysis of ethyl silicate with water adsorbed on the powder was precipitated onto the powder in the hydrophobic liquid which contained 90vol.% ligroin, 10vol.% ethyl silicate and 0.015mol/l stearic acid. The thickness of the coated layer was controllable by changing the amount of the adsorbed water up to 10wt.% of the powder.
