Microstructure analyses of mesophase pitch-based carbon fibers with high thermal conductivity

Mesophase pitch-based carbon fibers are most attractive candidates for thermally conductive materials and heat dissipation materials due to their low electrical resistivity and high thermal conductivity, but there are few research reports on their microstructrues and properties in our country. The microstructure and morphology of high conductive mesophase pith-based carbon fibers prepared by foreign country were analyzed in contrast with those of mesophase pitch-based carbon fibers with different transverse shapes fabricated in our laboratory. The results show that the high thermal conductivity of mesophase pitch-based carbon fibers is owing to their three-dimensional structure of graphite layers with oriented stacking and prefect graphite crystals. The higher heat-treated temperature, the more perfect growth of graphite crystals, and the more orientation of structure. In comparison to round-shaped mesophase pitch-based carbon fibers with radial structure in transverse section, the ribbon-shaped carbon fibers efficiently resolve the problem of splitting crack, which possess a interlayer spacing of 0.337 nm, a crystallite thickness of 26.77 nm, and a high thermal conductivity of 800 W/(m·K) along axial direction at room temperature.