Calculation of Diamond Phase Diagrams in the CO/H2 System under Low Pressure

The phase diagrams of diamond synthesis in CO＋H2 mixture gases were obtAlNed accordingto non-equilibrium thermodynamic coupling model. Thesc phase diagrams have diamond stabilityregions, which arc different from tile phase diagrams predicted by classical equilibrium thermodynamic theory. The existence of diamond stability regions is attributed to the distinctive effectsof super-equilibrium atomic hydrogen and atomic oxygen on diamond and graphite. With thepressure decreasing, the diamond stability region moves toward low CO concentration end. Thediamond stability regions calculated in the present work are in agreement with the experimentalresults reported in literatures.