Microstructure and electrical resistivity of carbon/carbon composites prepared by thermal gradient chemical vapor infiltration

Carbon/carbon composites were prepared by thermal gradient chemical vapor infiltration with kerosene as precursor. The microstructure and electrical resistivity were examined by polarized light microscopy and low-resistance instrument, respectively. The effects of processing parameters on microstructure as well as the influences of sample density, processing parameters, and needle punch on electrical resistivity of carbon/carbon composites were analyzed. The results show that besides rough laminar, smooth laminar and isotropic pyrocarbon occur at temperatures of 1000°C and 1200°C, respectively. The graphitization degree of composites increases from 16.28% to 63.95% as the heat treatment temperature increases from 2100°C to 2500°C. The electrical resistivity of carbon/carbon composites decreases with increasing heat treatment temperature and sample density but increases as the texture of pyrocarbon varies from rough laminar to smooth laminar. The main mechanism for influencing the electrical resistivity of carbon/carbon composites can be changing carrier concentration, altering grain scattering, or both actions.