Low Temperature Pressureless Sintering of SiC Using an Aluminum Borocarbide Additive

The densification of an Al3BC3-SiC system during pressureless sintering was investigated. Densification of SiC could be achieved after sintering at 1850 degrees C for 2 h by adding 10 wt% Al3BC3. The formation of partly crystallized grain boundaries and a core-rim structure within SiC grains indicated that liquid phase sintering was the major densification mechanism. The initial shrinkage at 1430 degrees C was caused by the formation of a liquid silicate phase. Sintering shrinkage accelerated above 1580 degrees C due to the rearrangement of SiC particles. The dissolution-reprecipitation of SiC and the final removal of pores occurred above 1780 degrees C. In contrast to Al2O3 additive which has low efficiency, Al3BC3 strongly promoted the pressureless sintering of SiC.