X-RAY PHOTOELECTRON SPECTROSCOPIC STUDIES OF CARBON-FIBER SURFACES .11. DIFFERENCES IN THE SURFACE-CHEMISTRY AND BULK STRUCTURE OF DIFFERENT CARBON-FIBERS BASED ON POLY(ACRYLONITRILE) AND PITCH AND COMPARISON WITH VARIOUS GRAPHITE SAMPLES

X-ray photoelectron spectroscopy has been used to monitor the surface chemistry of untreated carbon fibers based on PAN and pitch, a pitch fiber anodically oxidized in 1 M HNO3, and three different graphite materials. Differences were found in the core and valence-band region indicating a highly graphitic and almost unoxidized nature for untreated pitch-based fibers. The graphite samples were found to have more reactive surfaces than the pitch fibers. X-ray powder diffraction was used to study the bulk structures of these materials, and the Du Pont E-120 pitch-based fiber was found to have the most graphitic structure of all the carbon fibers examined. The anodic oxidation of the pitch fiber changed both surface and bulk structure, producing mainly one type of oxygen-containing group on the surface. © 1990, American Chemical Society. All rights reserved.