COMPUTATIONAL SIMULATION OF DIAMOND CHEMICAL VAPOR-DEPOSITION IN PREMIXED C2H2/O-2/H-2 AND CH4/O-2-STRAINED FLAMES

We have modeled combustion synthesis of CVD diamond in a stagnation-flow reactor under atmospheric conditions. In this configuration a premixed flat flame flows over a flat deposition substrate that lies perpendicular to the flow and parallel to the burner face. Optimal growth conditions occur when the flame is lifted from the burner surface and stabilized at the deposition surface. A similarity transformation for the stagnation flow field reduces the governing equations to a one-dimensional boundary value problem, significantly simplifying the computational task. The simulations include elementary gas-phase and surface chemistry as well as multicomponent molecular transport in the flame gas. Our model shows good qualitative agreement with observed growth parameters for the experimental conditions of Murayama et al. [1], who employed a premixed C2H2/H2/O2 gas mixture. Modeling CH4/O2 flame synthesis demonstrates that methane is less effective for diamond growth due to the decreased flame temperature and stability compared with C2H2 combustion.