Preparation and characterization of highly oriented ribbon shape pitch-based carbon fibers

Using a naphthalene derived mesophase pitch as starting material, high oriented ribbon-shaped carbon fibers with smooth and flat surface were prepared by melt-spinning, oxidation stabilization as well as further carbonization and graphitization processes. The composition, morphologies and microstructure of the ribbon-shaped carbon fibers treated at various conditions were characterized by elemental analyses, IR spectroscopy, XRD, Raman spectroscope, scanning electron microscope and polarized-light microscope. The results show that the carboxyl, carbonyl and ether functional groups formed during the oxidizing stabilization process are removed by subsequent carbonization treatment. The width and thickness of the ribbon-shaped fibers at the transverse section decrease from 1.6mm and 18 μm of pitch fiber to 1.2 mm and 9 μm of graphitized carbon fibers, respectively. The relative intensity of the diffraction peak at about 2θ=26° corresponding to (002) crystal plane of hexagonal graphite increases with the heat-treatment temperature increasing. This indicates that the crystal size of graphite in this carbon fibers also increases in this process. In comparison with the carbonized fibers, the carbon fibers after graphitization treatment display more perfect crystal orientation along the main surface of ribbon-shaped carbon fibers.