DIAMOND GROWTH BY METHANE INJECTION INTO HYDROGEN OXYGEN FLAMES

Diamond growth has been observed in rich hydrogen-oxygen flames with post-flame injection of methane near the substrate. The deposit size and growth rate have been measured for various gas injection geometries, flame conditions and substrate temperatures. The mixing between the injected methane and the surrounding flame has been examined by measuring the radial profiles of several species at the substrate. The CH4, H-2 and CO profiles have been acquired using sampling mass spectrometry, and the CH3 profiles have been obtained using resonance-enhanced multiphoton ionization. The chemical environment has also been simulated numerically. The comparison between the observed diamond deposits, the measured species profiles and the numerical simulations suggests that oxidation may limit the deposit size with the present injection geometry. Several refinements to this method are possible to enhance mixing and to reduce or eliminate oxidation problems.