| Popis: |
Scanning tunneling microscopy (STM) has been used as the primary tool to examine mesophase pitch-based carbon fibers ranging in modulus from 280–750 GPa. STM revealed a sheet-like structure for the carbon basal planes. These sheets were found to be composed of smaller elongated “pillows” that were aligned along the fiber axis. These pillows were found to become longer and more oriented as fiber modulus increased. STM images on the atomic scale revealed an increasingly graphitic structure with fiber modulus. These STM results correlate well to wide-angle X-ray diffraction (WAXD), small-angle X-ray scattering (SAXS) results and scanning electron microscopy (SEM). WAXD and SAXS also indicated a development of a highly oriented, more graphitic structure with increasing fiber modulus, while SEM revealed a cross-section composed of radial sheets. From these results, a proposed structure for a theoretical ultimate fiber is extrapolated. |
