STUDY OF CARBON-FIBER SURFACES BY SCANNING TUNNELING MICROSCOPY .2. PAN-BASED HIGH-STRENGTH CARBON-FIBERS

Two commercially available ex-PAN carbon fibers, T-300 and Courtaulds-XAU have been studied by scanning tunneling microscopy. The results at large scales have shown that the surface aspects of carbon fibers are mainly determined by the spinning procedure of precursor, rather than the precursor materials. As the scale is down to atomic resolution. both fibers present very similar surface micro-texture and micro-structure. The results have also revealed that the surface micro-textures of present fibers are essentially the same as for high modulus M40 carbon fibers. They are featured by the steplike and graphene textures which cover a greater part of the surface. However, their micro-structures are very different in both crystallite size and crystallite order. The imperfection of crystalline structure of present fibers is confirmed by diverse corrugation patterns appearing on STM images. Furthermore, some structural parameters of surface crystallites are estimated. The experimental results are presented and discussed.