LI Zhaojun, LIU Liangguang, LI Jianlin

(School of Materials Science and Engineering, Hainan University, Haikou 570228, Hainan, China)

Abstract:  Carbon fiber (CF) samples sintered at different pressures were prepared by using spark plasma sintering (SPS) at 1750 ℃, with the Toray T300-1K plain woven carbon cloth as raw materials. Scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FT-IR), Raman spectroscopy (Raman) and X-ray diffraction (XRD) were used to characterize morphology and microstructure of the samples, while the roundness of the fiber section was analyzed by using image processing. It was found that the pressure applied perpendicularly to the fiber axis at high temperatures would change the morphology and structure of the CF. With increasing pressure, the circular cross section of the CF tends to be flattened, the roundness of cross section was decreased from 0.91 to 0.65, the FWHM of (002) diffraction peak was decreased gradually, the crystal plane spacing was decreases from 0.3544 nm to 0.3488 nm, and a the microcrystalline size of CF long the direction of the fiber graphite mesh grew from 3.483 nm to 10.682 nm. The intensity ratio of D peak to G peak in the Raman spectrum was decreased gradually and the degree of graphitization of the fiber was increased. At 1750 ℃, with increasing pressure, the internal microstructure of the CF was developed from two-dimensional disordered graphite structure to ordered three-dimensional layered structure.

Key words:  carbon fibers; pressure; micro morphology; structure