Surface studies on Lyocell-based carbon fibers by scanning tunneling microscopy

The surfaces of Lyocellbased carbon fiber (LCF) and rayon-based carbon fiber (RCF) were characterized by SEM and STM. SEM results show that the surface of LCF is much smoother while the surface of RCF is rougher with obvious cracks and grooves. This is responsible for the low tensile strength of RCF. By STM, it is found that, for a 500?nm×500?nm area, the surfaces of LCF are characterized by a bulky structure with an area of about 150?nm2, which, when further imaged at 50?nm×50?nm, consists of smaller sluglike microstructures having a width of about 25?nm and length of 150?nm aligned at an angle of 45° to fiber axis. The distance between two adjacent carbon atoms of LCF is estimated to be 0.331?nm, which reveals that hexagonal carbon rings are not formed on the surface of LCF.