Surface characterization of carbon fibers using angle-resolved XPS and ISS

Angle-resolved X-ray photoelectron spectroscopy (ARXPS) and ion-scattering spectroscopy (ISS) are utilized to investigate the surface composition of BASF type II carbon fibers as a function of progressive exposures to aqueous nitric acid. To the authors' knowledge this is the first such study of carbon fibers to incorporate both of these surface analytical techniques. Overall, the ARXPS and ISS spectra are shown to be highly synergistic and quite consistent with one another. The data indicate that the surface composition of the as-received fibers is heterogeneous and undergoes significant changes upon nitric acid exposure. The net effect of the nitric acid surface treatments appears to be the systematic and preferential formation of carbonyl and carboxyl groups, and the establishment of a more uniform surface composition as a function of depth. It is expected that these data will contribute toward a better understanding of the interphase in carbon fiber composites.