Preparation and microstructure of hollow mesophase pitch-based carbon fibers

Hollow mesophase pitch fibers with rather thin diameter were successfully p repared by spinning through a C-shaped capillary. Die-swell was found to be the main factor affecting the formation of hollow fiber, and this was cont rolled by varying the spinning temperature. After carbonization at 1000 deg rees C, the hollow fibers possess a relatively small outer diameter of 21 m u m and an inner diameter of 6 mu m, and show better mechanical properties than solid fibers with similar outer diameter. The higher mechanical proper ties are attributed to the orientation of mesophase molecules which is rela ted to the shape and dimension of the spinneret. The transverse microstruct ure of hollow carbon fibers is illustrated by scanning electron microscopy (SEM) observations on fracture sections. (C) 1998 Elsevier Science Ltd. All rights reserved.