Microwave pyrolysis chemical vapour infiltration of carbon: experimental results

Abstract

Carbon/carbon composites were fabricated by Microwave pyrolysis chemical vapour infiltration. The carbon fibre felts (the bulk density ∼0·2 g cm–3) were infiltrated from methane at temperatures of 1075, 1100, 1125 and 1150°C, methane partial pressure ranging from 5 to 15 kPa, and various flowrates of the gas corresponding to residence times of 0·05, 0·1, 0·15 and 0·2 s, and the deposition gradients from the surface layer to the centre fibre regions of samples prepared by corresponding to process parameters were studied. The results show that the density gradients are improved by increasing residence time, decreasing deposition temperature and increasing methane pressure. The pore choking in the surface layer of preforms can be avoided, and the preforms can be densified from the inside out. After optimisation of densification process, the highest density of carbon/carbon composites prepared by microwave pyrolysis reaches 1·84 g cm–3 after infiltration time of 30 h.