INTERFACE MODIFICATION AND CHARACTERIZATION OF SILICON-CARBIDE PLATELETS COATED WITH ALUMINA PARTICLES

A colloidal-chemistry-based technique was developed for interface modi fication of silicon carbide platelets (SiCp) by coating with alumina p articles. The coating process utilizes electrostatic and/or electroste ric interactions between the particles to promote heterocoagulation. S ince an understanding of the chemical interface between the SiCp and a lumina is important for improving the coating process, the powders wer e characterized by the measurement of the electrokinetic sonic amplitu de (ESA). The major factors studied were particle size, type of alumin a, presence of polyacrylate surfactant, and concentration of alumina i n the coating slip. The surface coverage and morphology of the alumina coating on SiCp was determined quantitatively by scanning electron mi croscopy (SEM). The results indicate that around pH 5.8, the surface c harge difference between SiCp and alumina was the largest and the coat ing of alumina on SiCp was feasible. The SEM data showed that surface coverage was uniform, and the highest surface coverage on SiCp was 66% when the surface area ratio of alumina to SiCp was 250% in the suspen sion. No significant improvement of the coating rate was observed by t he addition of a polyacrylate for dispersion of SiCp. The concentratio n of alumina in the slip exhibited a strong influence on the amount of surface coverage on SiCp.