Low-temperature short-time nitriding of Va-group metals, V, Nb and Ta, in uncracked NH3 gas under heating with concentrated solar power (CSP)

Abstract

Over the last two decades, the authors have been using concentrated solar beam as the reaction heat source for synthesizing carbides and nitrides of d-group transition elements in view of usage of ecological renewable energy source in place of conventional heat sources using electricity or natural gas. In recent works, nitriding of VIa-group metals (Cr, Mo, W) and Fe in stream of NH₃ gas with suppressed extent of dissociation (uncracked NH₃) was attempted under heating with concentrated solar beam. It was demonstrated that mono-nitride δ-MoN of Mo and sub-nitride ɛ-Fe₂N of Fe that are known to be impossible to synthesize in N₂ gas environment even at elevated N₂ gas partial pressure p(N₂) up to 300 bar were successfully synthesized by the reactions of these metals in stream of NH₃ gas under heating with concentrated solar beam up to 800 °C.

In the present work, nitriding of Va-group metals (V, Nb and Ta) was attempted in stream of NH₃ gas under irradiation of concentrated solar beam. After 90 min heating in uncracked NH₃ under concentrated solar beam up to 800 °C, X-ray diffraction (XRD) characterization of the reaction products showed certain extent of nitriding progressed for all the specimens in spite of relatively low reaction temperature for short reaction duration.