Cleaner and non-carbon reduction for preparing high content VN alloy by direct nitriding of V ₂ O ₃ in ammonia gas

Conventional carbothermal synthesis of vanadium nitride (VN) alloy typically requires high temperatures exceeding 1300°C and a large amount of carbon, resulting in considerable energy consumption and CO₂ emissions. This process is incompatible with the dual-carbon strategy aimed at carbon neutrality. In this study, a novel and environmentally friendly approach for synthesizing VN is proposed through direct nitridation of V₂O₃ in an ammonia atmosphere. The thermodynamic feasibility of the reaction was rigorously evaluated, and key process parameters, including roasting temperature, reaction duration, and ammonia flow rate, were systematically optimized to achieve high product quality. Thermodynamic analysis confirms that the direct nitridation of V₂O₃ by NH₃ becomes spontaneous above 710°C. Under optimal conditions (800°C, 70 mL min
-1
NH₃ flow rate, 4 h reaction time), the synthesized VN exhibited a nitrogen content of 16.29%, vanadium content of 71.64%, and oxygen content of 10.54%, performance metrics comparable to those obtained via conventional high-temperature carbothermal methods. Nitrogen content was further increased to 18.87% when the temperature was raised to 850°C. Subsequent briquetting yielded a dense alloy with a density of 3.97 g cm
-3
, significantly surpassing the Chinese national standard (GB/T 20567–2020) requirement of 3.0 g cm
-3
for VN16-grade material. Mechanistic investigations indicate that the reaction proceeds through a stepwise replacement of V–O–V and V=O bonds with V–N bonds, forming a V–O(N) intermediate structure. This work presents an innovative, low-temperature (approximately 800°C versus >1300°C), shortened, and carbon-free route for high-quality VN production, offering a viable solution to the energy and environmental challenges inherent in traditional manufacturing processes.