Carbon silicon carbide composites prepared by chemical vapor infiltration combined with silicon melt infiltration

In order to reduce processing costs and improve the thermal stability of three-dimensional carbon fiber-reinforced silicon carbide composites, a chemical vapor infiltration combined with silicon melt infiltration method was developed for fabricating composites. According to the size of the pores in the preform, chemical vapor infiltration (CVI) and silicon melt infiltration (SMI) were mainly used to infiltrate small pores between fibers in a bundle and large pores between bundles, respectively. In the chemical vapor infiltration process, a pyrolytic carbon interfacial layer and a silicon carbide barrier layer were deposited on the surface of the carbon fiber. Then the pre-coated preform was infiltrated with pitch which was pyrolysed to form a porous carbon matrix in the pores. Finally, the preform was infiltrated with silicon melt to obtain composites. The influence of the interface thickness on the mechanical properties and the failure behavior of the composites were investigated, and the optimum thickness of the pyrolytic carbon layer was obtained. Experimental results also revealed that CVI+SMI composites exhibited good thermal stability of the mechanical properties and failure behaviors after the composites were annealed at high temperatures. (C) 1999 Elsevier Science Ltd. All rights reserved.