Fabrication and properties of dense silicon carbide ceramic via gel-casting and gas silicon infiltration

The dense Silicon Carbide (SiC) ceramics are fabricated by means of gel-casting and gas silicon infiltration (GSI) using carbon black and α-SiC as raw materials. We have successfully introduced a new initiator AIBA which is very suitable to aqueous gel-casting system containing carbon black, overcoming the problems posed by the conventionally used initiator. We have investigated the influences of the monomer acrylamide (AM) content, the ratio of the monomer to crosslinking agent AM/MBAM content, the particle size distribution and the solid content on the mechanical and structural properties of samples. The result show that, the linear shrinkage of the green body can be reduced to 1.0% and its bending strength can reach 59.2 MPa at the optimized gel-casting process that has an AM content of 25 wt%, an AM to MBAM ratio of 12, a SiC particle distribution of 3/2 and a solid content of 60 vol%. After the GSI process, the bending strength and elastic modulus of the final products from such green bodies can reach 245 MPa and 220 GPa respectively. The study highlights that the combined application of the gel-casting and the GSI processes can produce high-quality silicon carbide ceramics that are suitable in the space optical applications.