DIAMOND GROWTH IN TURBULENT OXYGEN-ACETYLENE FLAMES

Turbulent premixed oxygen-acetylene flames have been used to synthesiz e polycrystalline diamond films on molybdenum substrates at temperatur es ranging from 500 to 1300-degrees-C and facetted single crystals on mm-sized natural diamond substrates at temperatures of 1200-1300-degre es-C. Turbulence was achieved by increasing the torch's orifice diamet er and/or the flow velocity; the presence of turbulence was confirmed by observations of changes in the flame shape, measurements of the fla me's noise spectrum, and calculations of the Reynolds number. The opti cal emission spectra of several diamond-growing turbulent flames were also compared to the spectra of laminar flames. The variation in diamo nd quality with temperature and oxygen acetylene flow ratio was studie d with one or more of the following techniques: Raman spectroscopy, sc anning and transmission electron microscopy, infrared spectroscopy, an d photoluminescence spectroscopy. Crystals grown on molybdenum at temp eratures of 600-1100-degrees-C were observed to be transparent, and un der the proper conditions the quality of diamond grown epitaxially in a turbulent flame equals that of natural type-IIa diamond. Although th is enhanced quality has only been observed for fairly lean flames, the growth rate for type-IIa quality diamonds can still exceed 35 mum/h.