THERMODYNAMIC ANALYSIS FOR VAPOR-GROWN DIAMOND

A non-equilibrium thermodynamic coupling model is applied to diamond g rowth in CH4/H-2 gas mixtures and oxyacetylene flames, and the phase d iagrams of diamond synthesis in these two systems are calculated. Thes e phase diagrams are different from those predicted by classical equil ibrium thermodynamics, because a diamond growth region, where diamond is a stable phase, exists in each calculated phase diagram. The appear ance of the diamond growth region is attributed to the super-equilibri um atomic hydrogen and/or oxygen during the growth processes. Accordin g to the calculated phase diagrams stable growth of diamond in CH4/H-2 and C2H2/O-2 mixtures can be well understood.