SCANNING TUNNELING MICROSCOPE STUDY OF POLYACRYLONITRILE-BASED CARBON-FIBERS

Scanning tunneling microscopy (STM) was used to characterize the surfa ce topography of polyacrylonitrile (PAN)-based carbon fibers before an d after electrochemical treatment, stretch resistance test, and high-t emperature treatment. A new kind of spiral structures was found, which was not only on the surface but also in the inner layer. The spiral s tructure of the fibers was caused by the spinning process. The fiber s tructure contained the shape of the precursor. There were some large c racks in the carbon fibers after the stretching resistance test. The l arge cracks can result in carbon fiber breaking under certain stress c onditions. The difference in the structures of the carbon fibers befor e and after the high-temperature treatment was determined.