Microwave assisted chemical vapor infiltration to prepare carbon/carbon composites

Microwave assisted chemical vapor infiltration (CVI) was carried out to prepare carbon/carbon composites in a homemade microwave furnace in the temperature range of 1075-1150℃, using carbon fiber felt as the substrate and and methane as the pyrolytic carbon precursor. The felts were heated by absorbing microwave energy. Because the selective heating of the carbon fiber surface by polarization of polar groups on the carbon fiber surface and the catalytic effect of homogeneous gasphase reactions by microwaves, the preform was densified from center to surface to a bulk density 1.70g/cm³ after CVI for 90h. The densification rate was increased to 0.0189g/(cm³ · h). The pyrolytic carbon has a smooth laminar structure along carbon fiber surface. The radial density distribution of carbon investigated by optical microscopy indicates that plugging of the surface pores is avoided in the carbon fiber felts and the microstructure of the materials is uniform, having a medium texture.