Enthalpies of formation of Mo–Ru and Mo–Ru–Si compounds determined by high-temperature direct reaction synthesis calorimetry

Abstract

The enthalpies of formation of (Ru) hcp solid solution and Mo 5Ru 3 (σ phase) in the Mo–Ru system and ternary extension in the Mo–Ru–Si system at Mo 56Ru 37Si 7 composition, have been determined by high-temperature direct reaction synthesis calorimetry at 1760 K. The following values are reported: Δ f H 1760 K (Ru) = −10.6 ± 0.5 kJ/mol at.%; Δ f H 1760 K (Mo 5Ru 3) = −7.4 ± 0.4 kJ/mol at.%; Δ f H 1760 K (Mo 56Ru 37Si 7) = −13.1 ± 3.3 kJ/mol at.%. The results are compared with the previous values derived from e.m.f. measurements. They are also compared with the predicted values obtained by Calphad, by ab initio method combined to Calphad modelling, and derived from a thermodynamic database named “TM16.TDB”.