PREPARATION OF COILED CARBON-FIBERS BY CATALYTIC PYROLYSIS OF ACETYLENE, AND ITS MORPHOLOGY AND EXTENSION CHARACTERISTICS

Regularly coiled carbon fibers have been obtained by the catalytic pyrolysis of acetylene at 330 to 750-degrees-C using a Ni plate and powders as a catalyst. We have examined the morphology and extension characteristics of the obtained coiled fibers in some detail and discussed the growth mechanism. It has been observed that the coiled fibers were almost formed by the crossing or entwisting of two primaryd coils which grew in the same (coiling) direction simultaneously from a diamond-shaped nickel seed (combination coils). Other type of the coiled fibers, such as a single coils, double coils, and flat coils were also sometimes observed. The coiled fibers generally have a 0.1 to 0.3-mu-m thickness, 2 to 8-mu-m coil diameter, and 0.1 to 5 mm coil length. We have found that the coiled fibers could be extended elastically up to about three times versus the original coil length and semielastically up to about 4.5 times.