Tin(IV) Oxide Coating of Aluminum Borate Whiskers and Alumina Particles by Chemical Vapor Deposition

Aluminum borate whiskers of 0.5–1.0 μ diameter and alumina particles of 10–20 μ diameter were coated with SnO 2 by the reaction of SnCl 4 –H 2 O–N 2 gas mixtures in a rotary kiln reactor. Prior to coating, the whiskers were slightly etched to ensure adhesion between the SnO 2 layer and the whisker surface. The whiskers were coated at 100°C for 1 h, and then at 300°C for 2 h. This procedure was effective for covering the entire whisker surface with a uniform SnO 2 layer. Precoating was not necessary for the alumina particles. A compressed disk of the coated whiskers had an electrical conductivity of 30–40 S/m.