Abstract

A study of combustion synthesis of diamond films has been carried out using low-pressure, fuel-rich hydrocarbon/oxygen flames. Diamond growth results are reported for acetylene/oxygen, propylene/oxygen, and propane/oxygen flames. The best results are achieved with acetylene/oxygen flames, in which we have grown uniform, 5-cm-diameter polycrystalline films at up to 2.3 μm/h. The deposition rate in propane/oxygen is much lower (0.15 μm/h), and the diamond film quality is also lower. The experimental results are compared to the predictions of a numerical model that includes both detailed flame chemistry and simplified diamond surface chemistry. The comparison of the experimental conditions with the simulation results shows that diamond growth occurs for stoichiometries where a small amount of hydrocarbon ( The model correctly predicts the variation of film growth rate with changes in pressure, substrate temperature, and fuel type. For all flames, the absolute predicted growth rate is somewhat higher than measured, but the agreement is reasonable considering the modeling uncertainties associated with the high peak flame temperatures and incompletely understood diamond surface kinetics.

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