Carbon nanofibers from polyacrylonitrile and mesophase pitch

摘要

Carbon nanofibers were produced from both polyacrylonitrile and mesophase pitch. Stabilization and carbonization processes were used to convert as-spun nanofibers to carbon fibers. The nanofibers are arbitrarily long, althugh a way to make nanofibers less than a millimeter long, with high aspect ratios, was found. The diameters of typical carbon nanofibers are in the range from 100 nanometer to a few microns. A log normal distribution provides a good representation of the measured distribution of diameters. The carbon nanofibers were observed by polarized optical microscopy, scanning electron microscopy, transmission electron microscopy, and wide angle x-ray diffraction. As-spun mesophase pitch fibers are transparent, red or orange in transmitted light, and birefringent. Electron diffraction patterns were obtaiend from individual carbon nanofibers. The interplane spacing of (002) planes of mesophase pitch based carbon nanofibers was measured using wide angle x-ray diffraction. Nanofibers provide a higher ratio of surface area to mass than carbon fibers ordinarily used in composites. Carbon nanofibers can be useful in filters, as a support for catalysts in high temperature reactions, in composites to improve mechanical properties, or for therml management in semiconductor devices. Nanopores in carbon fibers were produced using nitrogen gas saturated with water vapor.