Surface structural evolvement in the conversion of polyacrylonitrile precursors to carbon fibers

Surface structural evolvement in the conversion of polyacrylonitrile (PAN) precursors to carbon fibers was investigated through scanning electron microscopy ( SEM), atomic force microscopy (AFM) and X-ray photoelectron spectroscopy (XPS). SEM results showed that the characteristic striated topography of PAN precursors resulted from the wet spinning process could pass down to carbon fibers. The fiber diameter gradually decreased from 11.3 mu m to 5.5 mu m and the corresponding density increased from 1.18 g/cm(3) to 1.80 g/cm(3) in the conversion of PAN precursors to carbon fibers. The ridges and grooves monitored by AFM became much more well-defined after the thermo-oxidation. However, the original longitudinal grooves were destroyed and both the depth and the width of longitudinal grooves decreased after the carbonization. XPS results revealed that carbon, nitrogen, oxygen and silicon were the governing elements on the fiber surface. The -C-C functional groups was the dominant groups and the relative contents of -C=O and -COO groups gradually increased in the process of thermo-oxidation and carbonization. (C) 2014 Elsevier B.V. All rights reserved.