Optimization of the Surface Characterization of Carbon Fiber by FT-IR Internal Reflection Spectroscopy

Abstract

Infrared spectra of surface-oxidized carbon fibers have been obtained with different angles of incidence, polarization states, and internal reflection elements (IREs) to find the optimal condition by internal reflection spectroscopy. It has been found that the maximum peak area of a surface functional group is obtained by using s-polarized light at a 30° angle of incidence for the multiple reflection technique. However, the highest signal-to-noise ratio is observed if unpolarized light is used. Spectral simulations have been performed to understand the observed spectra of the surface-oxidized carbon fibers according to exact optical theory. In the spectral simulations, Fresnel's three-layered system has been adopted to model the “IRE/oxidized layer/bulk of carbon fiber” system.