Detailed gas phase chemistry in CVD of carbon from unsaturated light hydrocarbons

An in-pore CVD of carbon, i.e., chemical vapor infiltration (CVI) is widely used to produce C/C composites. For the optimization of the process, it is important to understand the CVD of carbon at the level of elementary reactions. In this study, a model was developed to simulate complex gas phase reactions proceeding in CVD of carbon from unsaturated light hydrocarbons (C ₂H₄, C₂H₂, and C₃H ₆) by using a software package for computing time-dependent homogenous reaction systems. CVD experiments were performed with a vertical up-flow reactor at a temperature of 900°C, pressure ranging from 2 to 15 kPa, residence times up to 2 s, and a substrate surface area/volume ratio of 3.2 mm^-1. Gas phase components were analyzed by both on-line and ex-situ GC with good material balances of more than 90 %. The model which involves 230 species and 757 reactions can predict the profiles of 30 gas phase components from hydrogen to coronene (C₂₄H₁₂) with an acceptable level of accuracy.