文摘
Time-of-flight secondary ion mass spectrometry (ToF SIMS) has beenapplied in conjunctionwith isotope enrichment to investigate the chemical composition of thesurface species ofpoly(acrylonitrile)-based carbon fibers, which wereelectrolytically oxidized in dilutehydrochloric acid solution in water with17O/18O enrichment. The technique providesa toolwith greater specificity and sensitivity to elemental species thanX-ray photoelectronspectroscopy (XPS), in which the effects of the presence of the heavierisotopes on themodification to surface chemistry cannot be detected. Peaksassociated with oxygen-containing functionalities, for example,m/z = 16 (O-), 17(17O-, OH-), 18(18O-,17OH-),and19 (18OH-) were identified in negativeToF SIMS spectra of carbon fibers treated in isotopeenriched solution. Only m/z = 16(O-), 17 (17O-,OH-) were identified on carbon fibersurfacestreated in normal water. The concentrations of these surfacespecies all showed an increasingtrend with the level of treatment. The use of HCl solution as theelectrolyte introduced Cl-onto the fiber surfaces, and its concentration was determined usingboth XPS and SIMS,with SIMS showing a much improved sensitivity when the surfaceconcentration is lowerthan 0.5 atom %.