Simulation studies on chemical vapor infiltration of carbon

Chemical vapor infiltration of carbon from methane is simulated using a reaction model which includes gas phase reactions by formation of C2, mono- and polycyclic aromatic hydrocarbon species as intermediates of carbon deposition. Porous structures are approximated by open-ended capillaries with diameters and depths ranging from 1 to 0.01 mm and 10 to 50 mm, respectively. Infiltration profiles are determined for a constant temperature of 1100 °C, methane pressures from 5 to 30 kPa and residence times of methane from 0 s (capillary model) to 2 s (reactor model). Infiltration profiles are shown to increase from the mouth to the depth of the capillary, provided that the residence time outside of the capillary is sufficiently short to minimize pyrolysis reactions of methane. Increasing pressure and capillary depth lead to increasing infiltration gradients. These results are in good agreement with very recent experimental results from the infiltration of aeroplane brake discs.