EFFECT OF CARBONIZATION PRESSURE ON THE MORPHOLOGY OF PITCH DERIVED CARBON AND DENSIFICATION EFFICIENCY OF C/C COMPOSITES USED FOR AIRCRAFT BRAKES

Pitch cokes were prepared by carbonization of pitches from Wuhan Iron and Steel Plant and the Taiyuan Iron and Steel Plant under different pressures and heat treatments. Scanning electron microscopy (SEM) and polarized light microscopy were used to observe the morphology of the pitch derived carbon before and after graphitization. The results indicated that the pitch coke produced by low carbonization pressure was mainly of the flow domain anisotropy type with low bulk density, while the one resulting from high pressure was mainly coarse grained mosaic or fine grained mosaic with higher bulk density. X ray determination of the graphitization degree and microindentation hardness test showed that pitch derived carbon was comparable to rough laminar type CVD derived carbon to some extent and the pitch could be used as a precursor for the matrix of C/C composites. Results of densifying C/C composites under different pressure proved that densification efficiency was determined by carbon yield depending on the specimen, and relatively high pressure was needed to shorten the production time.