Structure of silicon-modified mesophase pitch-based graphite fibers

Silicon-modified mesophase pitch-based graphite fibers (SGF) were prepared from mixtures of mesophase pitch and silicon (Si) nanoparticles, followed by fiber spinning, thermo-oxidative stabilization, carbonization and graphitization. The morphology and microstructure as well as physical properties of the obtained graphite fibers were characterized. Compared with the unmodified graphite fibers (GF), SGF possessed the characteristic of the circular cross section, and no cracks along the fiber axis were observed. Based on the XRD and Raman analysis, Si nanoparticles added in the fiber resulted in the dissimilar orientation of graphitic pleats and changed the crystallite of the SGF. The angle of orientation and the ratio of the intensity of D-Raman peak and G-Raman peak for SGF were increased to 10.59° and 0.25, respectively, which were higher than that of the GF. The small-angle X-ray scattering experiment indicated that Si introduced in the fiber had no effect on the micropore size and pore size distribution compared with that of the GF. The tensile strength and modulus of the Si-modified carbon fibers was 2.42 and 138.8 GPa, respectively.