Effect of microstructure on the mechanical properties of PAN-based carbon fibers during high-temperature graphitization

The change of microstructure of PAN-based carbon fibers has been studied as a function of heat-treatment temperature (1,800-2,800 C, stretching 0%) by Raman spectroscopy and X-ray diffraction. With increasing heat-treatment temperature, both the crystallite size (L (a), L (c)) and the degree of preferred orientation (g) increase, while the crystallite interlayer spacing (d (002)) decreases. The values of both R (s) and R (c) decrease, while R (s) decreases more quickly. It implies that the degrees of skin-core of the carbon fibers increase. The relationship between mechanical properties and microstructure of the variants is also explored in detail.