Carbon fiber made from acrylic fiber and process for production thereof

摘要

Disclosed is a carbon fiber made from an acrylic fiber, the carbon crystal of which has a crystal size Lc of 15 to 65 ANGSTROM as determined by the wide angle X-ray diffractometry. This carbon fiber has regions with a lower crystallinity in the surface layer portion thereof than that of the central portion thereof, and the compressive strength sigma cf (GPa) of the single filament thereof determined by the loop method satisfies formula (I): sigma cf >/=10.78-0.1176xLc(I). The carbon fiber is produced by ionizing in vacuo an atom or molecule which is solid or gaseous at normal temperature, accelerating the ionized atom or molecule by an electric field, and implanting the accelerated ionized atom or molecule in a bundle of carbon fibers.