MICROSTRUCTURE AND ITS IMPACT ON THERMAL CONDUCTIVITY OF PITCH-FIBER BASED C/C COMPOSITES DUE TO HEAT TREATMENT

摘要

The influence of heat-treatment on microstructure, and thermal-conductivity of two-directionrnpitch-based-carbon-fiber with charred-resin-carbon matrix carbon-carbon composites wasrninvestigated. The heat-treatment was performed from 1800-to-2400C in inert environment. Thernmicrostructure changes were determined by polarized-light-microscopy, XRD, Ramanspectroscopy.rnPolarized-light-images exhibited an opening of structure with pitch-fiber shrinkingrnmore than charred-resin-matrix. A modest increase in crystallite size was found from XRDrnpatterns. However, Raman spectra showed a steady increase in the intensity of ‘Good’ band andrndecrease in ‘Defective’ band, indicating an overall increase in the crystallite size (La, Lc, dspacing)rnand subsequent an overall increase in the order of the structure. Raman profiling ofrnpolished surfaces showed an evolution of more ordered structure with increasing heat-treatmenttemperaturern(materials heat treated to 2400C). In-plane and out-of-plane thermal conductivity ofrnhighest heat treated C/C was higher than the rest of the samples. An apparent correlation existsrnbetween increasing heat treatment temperature, microstructure and thermal conductivity.