EFFECT OF POLYCARBOSILANE ADDITION ON MECHANICAL-PROPERTIES OF HOT-PRESSED SILICON-CARBIDE

Abstract

Silicon carbide ceramics containing 20 wt % polycarbosilane was fabricated by hot-pressing with various additives (B, Al, AlN). The addition of polycarbosilane resulted in a considerable increase in flexural strength up to 1050 MPa for the 1 wt % AlN and 0.5 wt % B-doped specimens and fracture toughness up to 4.0 M Pa m1/2 for the 1 wt % Al-doped specimen. The improved fracture strength was a result of liquid-phase sintering and the improved toughness was a result of crack deflection along the grain boundaries. Crack branching was also observed in 1 wt% AlN and 0.5 wt% B-doped specimens.