Production of the SiC/C Functionary-Gradient Material by the Chemical Vapor Infiltration Method and its Process Modeling

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The objective of this work is to shorten the production time of the SiC/C functionary-gradient material (FGM) and to prevent the surface peeling by producing the FGM by the chemical vapor infiltration (CVI) method.The fiber-reinforced FGM was produced using the specially designed reactor. 1,1,2-Trichloroethane and dimethyldichlorosilane were used to form carbon and silicon carbide, respectively. Distribution of silicon atom in the obtained FGM was measured by the X-ray micro-analyzer. The mathematical models were proposed to numerically simulate the FGM production by the CVI method. Simulations were carried out using the reaction rate equations of carbon and silicon carbide deposition that were determined in the independent experiments. Comparison between the experimental and calculated results indicated that the growth rate was greatly reduced when carbon and silicon carbide were co-deposited, and that the composition of silicon carbide in the FGM was lower than that estimated by the numerical simulation. Hence, kinetic analysis of the co-deposition of carbon and silicon carbide is carried out by use of the narrow-tube thermal CVD reactor. It was found that the growth of silicon carbide was hindered when carbon was deposited simultaneously.When the heaters were installed inside the reaction chamber, carbon was deposited on the heaters, which reduced heating efficiency and did not allow stable operation. Hence, a new reactor which has the heater unit outside the vacuum chamber was designed and constructed. Using the new reactor, we continue to carry out the FGM production experiments.