EFFECT OF WEIGHT-LOSS ON LIQUID-PHASE-SINTERED SILICON-CARBIDE

The evaporation of silicon carbide (SiC) ceramics during sintering has been studied by thermogravimetry in a graphite furnace filled with ar gon. The SiC powder compacts contained 7.5 wt% eutectic composition of Y2O3-Al2O3 to promote liquid-phase sintering. A weight loss of 1-11 w t% was observed during sintering, depending on the sintering temperatu re and sintering time. The weight Boss severely influenced the final d ensity and the microstructure of the SiC ceramics. Particularly, the o xide sintering aids, which were homogeneously distributed in the green ceramics, were observed to segregate and form particular patterns tha t were dependent on the temperature, sintering time, and the total wei ght loss. Possible heterogeneous reactions evolving volatile species h ave been discussed in relation to the experimental observations.