STUDY OF CARBON-FIBER SURFACES BY SCANNING-TUNNELING-MICROSCOPY .3. CARBON-FIBERS AFTER SURFACE TREATMENTS

The effect of surface treatments on carbon fibers has been studied by scanning tunneling microscopy (STM). The results show that over a wide range of oxidation degrees the anodic or electrochemical oxidation do es not change the surface aspects, neither at microscopic scale nor at nanometric scale, while the air plasma oxidation under the experiment al conditions gives rise to surface roughness and surface degradation. The results at atomic resolution have also revealed that the electroc hemical treatment yields a modest oxidation on the surface of carbon f iber and that the oxidation attack takes place preferentially at edge sites of graphitic crystallites. The microstructure of the fibers afte r anodic oxidation resembles very much that of low-temperature carboni zed fibers observed by STM. The structural imperfection has been tenta tively interpreted in terms of the formation of intercalated graphite compounds that render the graphite layer stacking imperfect.