Consideration of reaction mechanisms leading to pyrolytic carbon of different textures

Abstract

A distinction between a growth and a nucleation mechanism is not sufficient to draw direct conclusions in relation to the texture of pyrolytic carbon. This is determined by the carbon formation mechanisms, which are analogous or at least similar to the mechanisms of aromatic growth. The latter mechanisms are reviewed in the first part of the paper with special consideration of structural chemical aspects. The relevance of the individual mechanisms is analyzed in the second part based on experimentally determined reaction products. Most important mechanisms are aryl–aryl combination, intramolecular dehydrocyclization and ethine addition reactions. The influence of mechanisms concerning an inhibition of the formation of five-membered rings and a transformation of five- into six-membered rings is difficult to estimate. The results indicate that a high textured carbon is formed from a gas phase exhibiting an optimum ratio of aromatic to small linear hydrocarbons (ethine). This model is called the particle-filler model (aromatic hydrocarbons: molecular particles; ethine: molecular filler).