A mathematical model for depicting chemical vapor deposition process to fabricate SiC coating on carbon/carbon composites was developed. The concentration field of the reactive gases in reactor and the concentration distribution of reactive gases on the surface of sample were simulated with the finite element analysis. Combined with the experimental results

it is validated that along the flow direction of the reactive gases

the dimension of the as-deposited SiC crystal diminishes gradually with the concentration of the reactive gases decreasing

and the microstructure of the SiC crystal evolves from island to grain

and then to whisker.