HETEROCOAGULATION AS AN INCLUSION COATING TECHNIQUE FOR CERAMIC COMPOSITE PROCESSING

Colloidal heterocoagulation in aqueous media was used to form coatings of alumina or polystyrene latex particles on alumina spheres and of alumina or latex particles on silicon carbide whiskers. The polyelectrolyte dispersants poly-(ammonium methacrylate) and poly(ethylenimine) were used to alter the inherent surface potentials of the materials to increase the applicability of this technique. In most cases, the coatings formed were partial monolayers, although thicker coatings of alumina were formed on the SiC due to aggregation of the alumina. The oxide coatings were relatively well adhered while the latex coatings were easily removed in aqueous media. The adherence of the latex coatings was improved by adding low alcohols to the heterocoagulating suspension.