Infrared spectroscopy studies of the petroleum pitch carbon fiber—II. The distribution of the oxidation products between the surface and the bulk

Abstract

Fourier transform infrared photoacoustic spectroscopy (FT-IR/PAS) was used to study the distribution of the oxidation products between the surface and the bulk of the precursor carbon fiber during the stabilization process, and to evaluate the degree of oxidation in the near surface of the stabilized fiber. The distribution of the oxidation products is homogeneous during the first 70 min of the stabilization process. In the last 10 min of the process, however, the near surface of the carbon fiber is completely oxidized, whereas the bulk has a lower degree of oxidation. It was also found that incomplete oxidation in the near surface of a precursor carbon fiber may cause inferior mechanical properties of the fiber. An increase in the rate of temperature increase in the programmed stabilization process reduces the degree of oxidation in both the near surface and the bulk of the precursor carbon fiber. In this research, FT-IR/PAS has demonstrated the ability to differentiate the near surface of a carbon fiber from its bulk. It is a useful technique for the analysis of carbon fibers.