Effect of free carbon contained in SiC raw powders on slip casting and sintering processes

摘要

The SiC powders were pre-heated to evaluate the effect of the amount of free carbon and the oxygen content on the surface of the SiC particles on the fluidity of the SiC slurries and the sintered density. The amount of free carbon decreased and the oxygen content on the surface of the SiC particles increased by heating at > 300℃ and using these pre-heated powders, the fluidity of the SiC slurries was enhanced. On the other hand, the fluidity of the carbon slurries was effectively enhanced by the addition of aqueous ammonium 2-naphthalene sulfonate formaldehyde condensate (DEMOL-AS) solution. The green bodies were obtained through slip casting from the SiC slurries with carbon and B_4C and fired in Ar atmosphere at 2150℃. The sintered bodies with the SiC powders pre-heated at 300 and 400℃ exhibited the higher densities of about 98% Th. D. by the addition of 1 and 2.5wt% of carbon, respectively. The SiC body of the higher sintered density was possible to fabricate by controlling the addition of carbon, taking into account the oxygen content on the surface of the SiC particles and the amount of free carbon.