Thermodynamic aspects of co-formation of different condensed phases from CH4–WCl6 gas mixtures diluted in H2

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.