Surface modification of PAN based carbon fibers by high fluence N+ and C+ ion irradiation

Surface structure modification of PAN based carbon fibers under 30 keV C+, N+, N-2(+) and Ar (+) ions irradiation have been experimentally studied. It has been found that the corrugation effect of the fiber surface, which is typical for high-fluence irradiation with noble gases and nitrogen ions, does not manifest itself under irradiation with carbon ions. The dependences of the formation of surface patterns on depth distributions nu(x) of the number of displacements per atom (dpa) are considered. It has been shown that during corrugation the nu decreases monotonically with a maximum at the surface. The cause of corrugation is twinning of fiber-shell crystallites, which is caused by depth-dependent radiation-induced dimensional changes and relaxation of resulting mechanical stresses. The reason for the absence of surface corrugation under C+ irradiation can be the formation of a textureless modified layer.