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 (La, Lc) and the degree of preferred orientation (g) increase, while the crystallite interlayer spacing (d002) decreases. The values of both Rs and Rc decrease, while Rs 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.