Structural Improvement of Carbon Fibers Prepared from Benzene

Carbon fibers have been prepared by thermal decomposition of benzene at temperatures 1050–1080°C. Structural change with stepwise heat treatments up to 3000°C has been studied by X-ray and selected-area electron diffraction. The as-prepared fiber as well as the 1400°C-treated is basically of turbostratic structure, but has a preferred orientation of aromatic carbon planes more or less parallel to the fiber axis. By heat treatment around 2000°C, the preferred orientation is improved enormously; the carbon planes become almost completely parallel to the fiber axis, while the stacking order is still turbostratic. A three dimensional graphite structure is developed by heat treatment above 2400°C, which has qualitatively a similar behavior to that of graphitizing carbon. The fiber heat-treated at 3000°C consists of graphite layers concentrically surrounding the fiber axis.