X-RAY PHOTOELECTRON SPECTROSCOPIC STUDIES OF CARBON-FIBERS .15. ELECTROCHEMICAL TREATMENT ON PITCH-BASED FIBERS BY POTENTIOSTATIC AND GALVANOSTATIC METHODS

DuPont E-120 high-modulus pitch-based carbon fibers were treated on both an electrochemical standard cell system and a pilot plant system under potentiostatic and galvanostatic operation modes. X-ray photoelectron spectroscopy (XPS) and x-ray diffraction (XRD) techniques were used to monitor the fiber surface chemistry and bulk structure changes brought about by the electrochemical treatments. On both the standard cell and pilot plant systems, galvanostatic treatments gave more reproducible changes to the surface and bulk chemistry of the carbon fibers than did potentiostatic treatments. The difference was more obvious when the fibers were treated for a short period of time (less than one minute). The pilot plant system allows the fibers to be treated continuously to obtain a large amount of surface-modified fibers, enabling composite samples to be prepared. The work shows that operating the pilot plant system under a galvanostatic mode allows us to obtain a much more evenly treated fiber surface along the length of the fiber tow.