Synthesize And Preparation Of Reaction Bonded Silicon Carbide And Its Composites

Based on the traditional Reaction Bonded Silicon Carbide, a new type RBSC thatis called Pure Carbon Reaction Bonded Silicon Carbide was developed. And now thepreparation of PCRBSC by Pressure Forming and Slip Casting was alreadysuccessfully realized. In this paper, a green body moulding technology with highproperties-gelcasting was explored on the processing and properties of PCRBSC. Toimprove the inherent brittleness of RBSC ceramic, SiC whisker is incorporated inthe raw material of reaction bonded silicon carbide (RBSC) to prepare SiCw/SiCcomposites.Gel-casting is an effective way to get green body with high properties, and carbonblack slurry with low viscosity and high solid loading was the key of the moulding.However due to the small particle size of the carbon black and the large surface area,the carbon black particles are difficult to be uniformly dispersed. Meanwhile the highsolid loading may lead to the high intensity of the carbon green body, which results inthe problem of difficulty to sinter. To solve these problems, the second carbon blackparticles with low intensity were prepared by the addition of pore-forming agent,followed by the mold through the method of gel-casting. It was demonstrated fromthe research that slurry with high solid loading and low viscosity can be obtained viathe preparation of the second carbon black particles and adoption of appropriatedispersant, as well as suitable matching processe. The carbon green black has theproper intensity. The ultimate PCRBSC material with the intensity 3.08g/cm³ andthree point flexure strength at room temperature 432MPa was obtained by reactionsintering.The usage the SiC ceramic was constrained because of the intrinsic brittleness.The key point of preparation of SiC_W/SiC via reaction sintering is to fabricate SiCbased compound with high intensity through reinforced with whiskers, But the vitaladvantage of this method with seeping Si is that SiC_W can be easily separated outfrom the melting Si after dissolve in that. So the measure of protection on SiC_Wshould be taken. In this paper, the protection layer of Al₂O₃ was prepared outside ofSiC_W by sol-gel. After being sintered at the high temperature 1650℃, the SiC_W was remained in the compound and the rupture toughness had been improved, whichshowed that the protection layer was effective. The morphologic of the cross sectionshowed that the whiskers。The research preliminarily enables the preparation of thismaterial.