Abstract
The present study outlines the importance of carbon active sites in controlling the kinetics of pyrolytic C deposition on a graphitized pitch fiber at 1025 deg C. Blockage of active sites with chemisorbed hydrogen retards deposition rates substantially. Removal of the chemisorbed H from the occupied sites raises deposition rates to the normal values noted on a fresh "clean" surface. The effect of surface activation prior to deposition is discussed. Activating the surface generates additional active sites and enhances the rates. However, not all the newly developed sites contribute to the kinetics. After the deposition of the first C layer, a fraction of those newly developed sites is instantaneously blocked and does not further contribute to subsequent deposition. The remaining fraction, along with the original sites available before activation, keeps replicating during the remaining course of deposition. That is, the disappearance of one active site after C deposition is associated with the generation of a new site. This trend continues up to the deposition of 60 C layers.