Rapid Densification of Carbon/Carbon Composites Plate by Pressure-Gradient Chemical Vapor Infiltration

Carbon/carbon (C/C) composites plate is prepared in the temperature range 1 223-1 373 K by improved pressure-gradient chemical vapor infiltration (CVI). The bulk densities and pore distributions of C/C composites after different infiltration period are measured and the densification kinetics is investigated. The results show that C/C composites plate with 300 x 300 x 15 mm is able to be densified to 1.52 g cm(-3) within 60 h by pressure-gradient CVI. The porosity of pores with a size larger than 60 mu m reduces markedly and the large pores are able to be filled more effectively by pressure-gradient CVI. The densification kinetics depends on the temperature and competition between reaction and convection mass transport. The activation energy is about 366 kJ mol(-1) at 1 223-1 313 K and 43.2 kJ mol(-1) above 1 313 K.