Characterization of carbon/carbon composites prepared by different processing routes including liquid pitch densification process

Carbon/carbon composites with an apparent density higher than 1.80 g/cm3 were prepared using a multi-step densification process. This consists of a pre-densification step followed by pitch impregnation/pyrolysis (I/P) cycles carried out under moderate pressure. Three pre-densification methods were investigated to significantly increase the apparent density of a raw preform to about 1.4 g/cm3. These were: (i) impregnation by carbonaceous powder slurry, (ii) film boiling chemical vapor infiltration, (iii) impregnation with a combination of synthetic pitch I/P and carbonaceous powder slurry. Composites were prepared from each of these three pre-densified materials, using a liquid pitch processing route with four I/P cycles with M50 petroleum pitch, under moderate pressures (10 MPa). As a reference a carbon/carbon composite was prepared using four I/P cycles with pitch.All four composites had different microstructural characteristics and different thermal properties. The influence of processing on thermal properties is discussed in relation to the microstructural characteristics.