Thermal decomposition of δ-MoN and ε-Fe2N synthesized under concentrated solar radiation in NH3 gas stream

Abstract

Decomposition temperatures of δ-MoN and ε-Fe2N synthesized with flowing NH3 gas under concentrated solar radiation heating were evaluated by Differential Scanning Calorimetry (DSC) in Argon (Ar) gas environment. The measured decomposition temperature of δ-MoN and ε-Fe2N were dependent on the solar synthesis conditions, particularly either NH3 or N2 gas flow rate at temperature. Sample containing δ-MoN showed two exothermic peaks around 680 and 900 °C, attributed to the reactions of δ-phase into γ-single-phase and (γ+β)-two-phase Mo2N, respectively, attributed to the dissociation reaction of δ-phase into γ-single phase and the dissociation reaction of γ-phase into metallic M saturated with N, respectively. Decomposition of ε-Fe2N took place into γ’-Fe4N in two steps occurring at 606 and 660 °C, respectively. When N2 instead of ammonia (NH3) gas was used, complete dissociation of γ’-Fe4N into Fe took place at around 610 °C. Full decomposition of γ’-Fe4N into metallic α-Fe(N) was corroborated by X-ray diffraction (XRD) analysis.