Study of the microstructure and the mechanical properties of high strength PAN-based carbon fibers

The microstructure of high strength PAN-based carbon fibers T800H and T1000G were studied by Elemental analysis,Scanning electron microscopy(SEM),X-ray diffraction(XRD) and Raman spectroscopy.The results showed that T1000G fibers had more carbon and less nitrogen than that of T800H fibers.The surface of T1000G was smooth,whereas the ridges and grooves were much more prominent in the T800H fibers,indicating the former was dry-jet wet spinning and the latter was wet spinning.Grain-like features were seen in the cross section surface of both fibers,but the grains were larger in T800H than in T1000G.Comparing with T800H fibers,T1000G fibers had larger apparent crystallite size(Lc,La),better preferred orientation,smaller apparent crystallite layers spacing(d002),less porosity rate(Vp) and better homogenization,all of which accounted for the higher tensile strength of T1000G fibers.