PHASE-DIAGRAM FOR DIAMOND GROWTH IN ATMOSPHERIC OXYACETYLENE FLAMES

The temperature vs. gas composition phase diagram of solid carbon depo sition in atmospheric oxyacetylene flame is calculated. The phase diag ram, which is composed of a diamond growth region, a gas phase region, and a non-diamond carbon growth region, is identical with the reporte d experimental data. So the suitable ranges of substrate temperature a nd O-2/C2H2 ratio for diamond synthesis in oxy acetylene flames can be theoretically predicted. When the substrate temperature is between 10 00 K and 1250 K, the corresponding O-2/C2H2 ratio range is about betwe en 0.8 and 1.1. The suitable range of substrate temperature is widest for O-2/C2H2 ratio close to unity and is narrowed rapidly when the flo w ratio deviates from unity.