鳞片石墨掺杂对单向C/C复合材料结构和性能的影响

Unidirectional carbon/carbon composites were prepared by hot-pressing mesophase pitch-based carbon fibers as the conductive filler phase and mesophase pitch containing natural flake graphite as the binder/matrix at 500℃ followed by carbonization at 1000℃ for 1 h and graphitization at 2900℃ for 1 h. The morphology and microstructure of cross-sections of the samples were characterized by polarized-light microscopy and scanning electron microscopy. The effect of adding natural flake graphite to the mesophase pitch on the thermal conductivity of the composites was investigated. Results show that the graphite addition has little effect on the bulk densities of the composites, but has a significant impact on the thermal conductivities in different directions. With increasing the graphite content and particle size, the thermal diffusivity of the composites in the longitudinal direction of the fibers decreases while that in the perpendicular direction increases. With a graphite addition of 16 vol% and an average graphite particle size of 60 μm, the longitudinal thermal diffusivity of the composite decreases from 650.5 to 510.9 mm²/s while the perpendicular thermal diffusivity increases from 22.4 to 48.9 mm²/s. The flexural strength of the composites perpendicular to the fibers is also increased by 29% by adding graphite.