COLLOIDAL PROCESSING OF SILICON-CARBIDE

Rheological properties of silicon carbide aqueous suspensions and sintering behavior of consolidated powder compacts were studied on two kinds of submicrometer-sized powders (powder A: median size 0.1 mum, 0.38 wt% SiO2, powder B: median size 0.7 mum, 1.75 Wt% SiO2). Highly concentrated fluid suspensions (> 50 vol%) and high-density green compacts (> 65% TD (theoretical density)) were prepared from electrostatically stabilized powder B in the solutions at pH = 10. Addition of fine gamma-alumina particles (almost-equal-to 20 nm) as a sintering additive (0-5 wt%) lowered both the green densities of powders A and B to about 50% TD. The density of SiC with alumina hot-pressed at 2100-2150-degrees-C was higher for powder B than for powder A.