Flame Structure and Diamond Growth Mechanism of Acetylene Torch

Abstract

To understand the diamond growth mechanism in C₂H₂/O₂ flame, we carried out gas analyses for various mixture ratios (R=C₂H₂/O₂) with laser-induced fluorescence and mass spectrometric techniques. These measurements show that CO and H₂ are the dominant gases in the feather, and that C₂H₂ and C-containing radicals (e.g., C₂H, CR, Cn, n=1-3) are minor species. Their concentrations are found to be consistent with the equilibrium values estimated by the adiabatic calculation. The feather is formed by the inter-diffusion and reactions between these C-radicals and O-radicals (e.g., O and OH), which are produced in the intermediate zone by the oxidation with O₂ supplied through the secondary flame. It is also found that R-dependences of the diamond growth rate is in good agreement with those of CH and C₂ concentrations in the feather.