Axial nano-scale microstructures in graphitized fibers inherited from liquid crystal mesophase pitch

Nano-scale structures of a mesophase pitch based carbon fiber were characterized using a high-resolution scanning electron microscope (HR-SEM) and a scanning tunneling microscope (STM). Fibril was found to be sectioned by a number of pleat units, being aligned parallel along the fiber axis. The periodical size, thickness and height of pleat unit was estimated as 30–60 nm, 20–30 nm and around 7 nm, respectively. In a pleat, graphitic units of 30–60 nm long and 2–4 nm wide run principally perpendicular to the axis. The basal plane of graphite was observed at the largest magnification. Such a series of nano-structures should be related intimately to the performance of the fibers. The formation mechanism of such series of nano-structural units is discussed in relation to the nano-structure of the liquid crystal mesophase pitch and its deformation during the spinning.