A submicrometer-sized silicon carbide powder was mixed with 0.2 mum alpha-alumina and 0.1 mum yttria powders at the volume ratio of SiC/Al2O3/Y2O3=1/0.3/0.3 or 1/0.020/0.016 in aqueous solutions at pH 3similar to10. The interaction of the SiC-Al2O3-Y2O3 system in the dilute suspensions of 0.02 vol% was examined by measuring their zeta potentials and particle size distributions. Positively-charged or weakly-charged Al2O3 and Y2O3 particles were adsorbed on the negatively-charged or neutral SiC particles in the wide pH range from 3 to 8. Co-dispersion of the negatively-charged particles in the SiC-Al2O3-Y2O3 system was measured at pH 10.0. The viscosity of the SiC/Al2O3/Y2O3 suspension with 30 vol% solids became higher than that of monolithic SiC suspensions at pH 5 and 8 because of the formation of the network structure of SiC particle clusters with Al2O3 and Y2O3. The addition of positively-charged or weakly-charged Al2O3 and Y2O3 particles to the SiC suspension decreased the green density of SiC compact.

Keywords: