CHEMICAL-STATE ANALYSIS OF HEAT-TREATED POLYACRYLONITRILE FIBER USINGSOFT-X-RAY SPECTROMICROSCOPY

Chemical state analyses of heat-treated polyacrylonitrile (PAN) fibers with a spatial resolution of 200 nm have been performed using scannin g transmission X-ray microscopy (STXM) at a third generation synchrotr on radiation facility. Near-edge X-ray absorption fine structure (NEXA FS) spectra and chemical state images have been obtained on the cross- sectioned fiber specimens. A clear 'core-rim' structure has been obser ved in the heat-treated fibers. The spectral characteristics show that the fiber has less nitrile group in the core region, suggesting that, contrary to the model widely believed, the conversion of the nitrile to other chemical species proceeds faster in the core of the fibers. ( C) 1998 Elsevier Science B.V. All rights reserved.