Study of carbon-fiber surfaces using Auger and secondary electron emission spectroscopy

Abstract

Structure at 3.0, 4.0, 7.5, 8.5, 10.0, 12.0, 14.5, and 17.5 eV in the secondary electron energy distribution of low-energy electrons back-scattered from carbon-fiber surfaces is shown to be similar to that observed from single-crystal graphite, which is due to emission from the high density of conduction-band states located 5 to 20 eV above the Fermi level. The intensity of secondary emission from these states is related to the degree of graphitic order in high- and low-modulus specimens of polyacrylonitrile (PAN-) and pitch-based carbon fibers. The results are discussed in terms of the effect of thermal treatment in high vacuum on the size and orientation relative to the fiber axis of regions of graphitic order in a surface layer of the order of 100 Å and a comparison is made with known models of carbon-fiber micromorphology. Auger electron spectroscopic analysis revealed the nature and degree of surface contamination on the different fiber types.