Hot-pressing and mechanical properties of SiC ceramics with polytitanocarbosilane

An SiC power of median size 0.8 mum was mixed with an Al2O3 powder of median size 0.2 mum in a 0.3 M-Y(NO3)(3) solution at pH 5 to distribute homogeneously the sintering additives (Al2O3+Y3+ ions) around the SiC particles. In a 30 vol% SiC suspension, the network structure of SiC particles was formed by the heterocoagulation through the adsorbed Al2O3 and Y3+ ions. The aqueous suspension of the SiC-Al2O3 (1.17 vol%)-Y3+ ions (0.94 vol% Y2O3) system was consolidated by filtration through a gypsum mold and formed green compacts of 52-55% of theoretical density. Polytitanocarbosilane (PTC) of 0.04-5.2 vol% was infiltrated into the calcined SiC compact. The SiC compacts with and without PTC were hot-pressed under a pressure of 39 MPa at 1950degreesC in an Ar atmosphere. Addition of PTC to the SiC compact increased the sinterability, flexural strength and fracture toughness of SiC and suppressed the grain growth during the hot-pressing. The measured mechanical values of SiC with 1.3 vol% FITC were as follows: average four-point flexural strength 711 MPa, fracture toughness 5.9 MPa(.)m(1/2), Vickers hardness 19-21 GPa, and Weibull modulus 12.5.