Synthesis of Non-Cubic Nitride Phases of Va-Group Metals (V, Nb, and Ta) from Metal Powders in Stream of NH3 Gas under Concentrated Solar Radiation

• Published in: ChemEngineering 2021-04, Vol.5 (2), p.19
• Main Authors: Shohoji, Nobumitsu, Oliveira, Fernando Almeida Costa, Galindo, José, Rodríguez, José, Cañadas, Inmaculada, Fernandes, Jorge Cruz, Rosa, Luís Guerra
• Format: Article
• Language: English
• Subjects: Ammonia; Chemical engineering; concentrated solar radiation; Crystal lattices; Crystal structure; Cubic lattice; Degree of crystallinity; Electric furnaces; Gamma phase; Gas absorption; Gas flow; Gases; Metal powders; Niobium; nitride; Nitrides; Radiation; Reaction products; Solar furnaces; Solar radiation; Tantalum; Temperature; Transition metals; uncracked NH3 gas; vanadium
• ISSN: 2305-7084; 2305-7084
• DOI: 10.3390/chemengineering5020019

Using a high-flux solar furnace, loosely compacted powders of Va-group transition metal (V, Nb, and Ta) were reacted with stream of NH3 gas (uncracked NH3 gas) being heated by concentrated solar beam to a temperature (T) range between 600 and 1000 °C. From V, sub-nitride V2N (γ phase) and hypo-stoichiometric mono-nitride VN possessing fcc (face-centered cubic) crystal lattice structure (δ phase) were synthesized. On the other hand, in the reaction product from Nb and Ta, hexagonal mono-nitride phase with N/M atom ratio close to 1 (ε phase) was detected. The reaction duration was normalized to be 60 min. In a conventional industrial or laboratory electric furnace, the synthesis of mono-nitride phase with high degree of crystallinity that yield sharp XRD peaks for Va-group metal might take a quite long duration even at T exceeding 1000 °C. In contrast, mono–nitride phase MN of Va-group metal was synthesized for a relatively short duration of 60 min at T lower than 1000 °C being co-existed with lower nitride phases.