Improvement of densification uniformity of carbon/silicon carbide composites during chemical vapour infiltration

We have investigated the influence of the process parameters on the density and distribution of 2.5D carbon preforms during chemical vapour infiltration (CVI) of silicon carbide. The lower the pressure and the substrate temperature, the higher the density and its uniformity. The temperature of the lower part of the disc-shaped specimen was as low as 1000°C to suppress the surface reaction that caused the closure of the open porosity. The specimen of 1000°C under 10 torr resulted in the density of 72.2% and the standard deviation of 13.9%., while that of 1000°C under 50 torr showed the density of 69.1% and the standard deviation of 18.6%. The low density of the specimen was mainly attributed to the large voids between the carbon bundles.