Carbon/carbon composites were fabricated by low-pressure chemical vapour infiltration (LP-CVI) method using a propane gas.
The effects of deposition temperature (900, 1100 ℃), propane concentration (5, 100 %), gas flow rate (10, 100 SCCM) and pressure (5, 50 torr) on the densification of phenol-based carbon/carbon preform were studied utilizing experimental design method. The bulk density of carbon/carbon composites increased in the range from 1 % to 9 % and their apparent porosities decreased in the range from 20 % to 50 %.
According to the result of the analysis of variance (ANOVA) of experimental data an optimum processing condition for densification under given conditions were found to be 1100℃ (temperature), 100 % (concentration of propane), 100 SCCM (flow rate), and 5 torr (pressure).
On the basis of result of experimental design, the effect of deposition temperature on the densification was also studied in the range of temperature between 900 ℃ and 1200 ℃ at an interval of 100℃ with 100% propane, 100 SCCM, 5 torr. The maximum bulk density of 10.5 % was achieved for the sample deposited at 1000 ℃.
In the case of the sample deposited at 900 ℃, the bulk density was lower than that of the sample deposited at 1000 ℃ due to lower rate of deposition. In the case of the sample deposited at 1100 ℃ the bulk density was lower than that of the sample deposited at 1000 ℃due to blocking of pores on the surface which arises from higher rate of surface deposition.
