Inhibition of carbon fiber growth from naphthalene with halogens

The influence of HCl, Cl₂, Br₂ and I₂ on the vapor phase growth of carbon fibers from naphthalene was examined at 1100°C with the expectation of a promotive effect similar to H₂S. However, these halogen additives were found not to catalyse but to inhibit the growth. Employment of 1-chloronaphthalene as the source material also resulted in the remarkable suppression of fiber formation. The fibers obtained in the presence of the halogens exhibited highly pockmarked surfaces, due to deposition of soot-like carbon. In addition, the deposition was preferential at the growing end of the fiber, so that the diameter became thick progressively from root to tip. From these observations, the inhibition of the fiber growth with halogens was attributed to the accelerated decomposition of naphthalene into soot-like carbon.