PREPARATION, MORPHOLOGY, AND MICROSTRUCTURE OF DIAMETER-CONTROLLABLE VAPOR-GROWN CARBON NANOFIBERS

Pure vapor-grown carbon nanofibers (VGCNF's) with controllable diamete rs of 10-200 nm were prepared by an improved floating catalyst method. Through transmission electron microscopy (TEM) observation, it was fo und that VGCNF's have a duplex structure, a hollow and high-crystallin ity graphite filament called primary carbon fiber surrounded by a pyro carbon layer with low graphite crystallinity. It was observed using hi gh-resolution TEM that VGCNF's have excellent graphitic crystallinity with graphite layers stacked neatly parallel to fiber axis. Moreover, x-ray diffraction results showed that the graphitic crystallinity of c arbon fibers became higher with decreasing diameter of carbon fibers.