Nanostructure analysis in pan-based carbon fibers focused on amorphous carbon

The nanostructure of PAN-based carbon fibers was comprehensively investigated, with an emphasis on amorphous carbon. In-situ measurement of the crystallite deformation and micromechanical analysis revealed that the amount of amorphous carbon in PAN-based carbon fibers was approximately 50%. In addition, the mechanical properties of the amorphous carbon could be obtained through the analysis, which helped to identify the structure. The weight fraction of sp2 carbon layers calculated from an analytical model based on the rule-of-mixtures using Raman spectroscopy data and the crystallinity calculated by the micromechanical model indicated the differences in intermediate modulus and high modulus carbon fibers, which were affected by the measuring method. Radial distribution analysis using neutron scattering allows one to obtain a detailed structural analysis of the amorphous carbon in PAN-based carbon fibers. The analysis results suggest that the number of lattice defects in intermediate modulus carbon fibers is 20% larger than in the high modulus type and these lattice defects are present in the amorphous component. These new findings, based on extensive analysis, suggest that controlling the ratio of amorphous to crystalline carbon is one of the key factors determining the mechanical properties of PAN-based carbon fibers.