Directional pyrolytic growth of microscale carbon fibers on electrochemically pretreated polyacrylonitrile-based carbon microfibers

Vapor-grown carbon microfibers were synthesized pyrolytically on electrochemically pretreated polyacrylonitrile-based carbon microfibers (PAN-CFs) without introducing any catalyst. Cyclohexane was used as the carbon source for the growth of fibers in a thermal chemical vapor deposition process (CVD). Scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS) were used for the characterization of the fibers. Microscale carbon fibers with about 1 to 2 mu m in diameter were formed at 1123 K, while carbon microfibers of about 0.3 mu m in diameter were synthesized at 1048 K. A pretreatment at negative potential or sequentially at both positive and negative potentials was found to be a prerequisite for the growth of carbon microfibers in the CVD process. Without electrochemical pretreatment or when only a positive potential was applied, the growth of microscale carbon fibers did not occur.