Effusion-mass spectrometric study of thermodynamic properties of vanadium and vanadium nitride

Abstract

Effusion-mass spectrometric studies were performed on the vapour species in equilibrium above VN(c) in the temperature range 1900 to 2412 K. From an analysis of the reactions involved, ΔH_f298 values of 122.4 ± 5 kcal/mol (second law) and 120.4 ± 2 kcal/mol (third law) were obtained for VN(g), yielding a dissociation energy, D^° ₂₉₈, for gaseous VN of 114.1 kcal/mol. An appearance potential of 8 ± 1 eV was recorded for VN(g). The thermodynamic analysis of the vapour species over the solid state yielded a second law ΔH_f of –52 ± 1.5 kcal/mol for VN(c). Studies made in this temperature range resulted in a third law heat of fusion of 4.30 ± 0.45 kcal/mol for vanadium. The second and third law mass spectrometric ΔH_f298 values of 122.8 ± 1.5 and 123.0 ± 0.2 kcal/mol, respectively, for V(g) were in good agreement with Knudsen third law weight loss experiments at 2092 and 2122 K, which yielded ΔH_f298 values of 123.3 and 122.9 kcal/mol.