Thermodynamic aspects of co-formation of different condensed phases from CH < inf > 4 < /inf > –WCl < inf > 6 < /inf > gas mixtures diluted in H < inf > 2 < /inf >

Abstract

Gibbs free energy minimization approach was used to identify the temperature, pressure and composition ranges under which the co-formation of different condensed phases (namely graphite, diamond, WC, etc.) takes places from CH4–WCl6 gas mixtures diluted in H2. Binary and ternary-phase diagrams are constructed to show the formation of different equilibrium solid phases at different initial conditions. The optimum conditions for co-formation of hard phases namely diamond and WC phases at equilibrium are: temperature in the range 973–2073 K, pressure in the range 10–50 Torr, H2/CH4 molar ratio of 10 or less and WCl6/CH4 molar ratio in the range 0.1–0.9. This work paves a way to plan chemical vapor deposition experiments that may result in composite films consisting of hard phases such as diamond and WC.