Fabrication And Characterization Of Silicon Carbide Green Body With Phenolic Resin As Carbon Source

The large-scale light-weight space mirror is the key element to improve spaceobservation and remote sensing techniques. Silicon carbide (SiC) has excellentperformance, such as high specific stiffness, low thermal expansion coefficient andgood thermal conductivity, so it played an irreplaceable role in the space mirrorfield.Reaction sintered SiC molding process, with the propterties of a low cost andnear-net-shape, is a preferred way to make excellent optical space mirror. Reactionbonded SiC (RB-SiC) product, however, is difficult to be machined. In order tosolve this issue, a preparation process of SiC green body, which could be machinedeasily, by gel-casting was reported in this paper. By combining Reaction BondedSiC with Reaction Formed SiC, and phenolic resin as carbon source, porous RB-SiCgreen body was prepared, in which the pore is formed through phase separationinduced by polymerization and gel-casting processes.This paper studied on the methods to prepare SiC slurry with high-solid contentand better rheology. The optimum process parameters of the gel-casting processwere obtained. The slurry viscosity and the mechanical properties of the SiC greenbody were tested, and the impact factors were analyzed. The SiC slurry wasprepared with75wt%SiC particles, and the rheology can meet the requirements ofthe gel-casting process. According to the effect factors, such as the solid content,velocity of temperature variation and pre-curing temperature, the principle of resincuring, the silicon carbide ceramic slurry green body with uniform pore distributionwas prepared.The SiC green bodies, made by gel-casting process, were tested and studied.The main influencing factors of the SiC green body are SiC content and graincomposition. The machining simulation results of SiC green bodies, prepared withoptimal formula， show that, the SiC green body meet the requirements of theabrasive machining.