Synthesis of ultrafine VN particles by vanadium trioxide reduction–nitridation in a CH4–N2 atmosphere: Mechanistic and experimental study

Owing to its high hardness, favourable stability, and good electrical performance, vanadium nitride (VN) is extensively used as an alloy additive, electrode material, ceramic material, and catalyst. However, the traditional synthesis methods for VN require high temperatures and long soaking times. Herein, ultrafine VN particles were prepared at a lower temperature and shorter soaking time from V2O3 powder in the presence of a CH4–N2 gas mixture. Thermodynamic analyses, ab initio molecular dynamics (AIMD) simulations, and experimental investigations were performed to investigate the mechanisms of this process. Thermodynamic analysis showed that V2O3 reacts with the CH4–N2 gas mixture under atmospheric pressure at a lower temperature to produce VN. The interactions between CH4, V2O3, and N2 at the atomic level were systematically clarified, and the important role of N2 molecules was determined using AIMD simulations. N2 not only reacts with V2O3 to form V–N bonds but also acts as a medium for adsorbed CH4 molecules to decompose and act as a further reducing agent. The experimental results showed that ultrafine VN particles were obtained at a heating temperature of 1173 K, soaking time of 1.5 h, CH4:N2 molar ratio of 1:2, and gas flow rate of 0.9 L/min. The final product was characterised by X-ray diffraction, field-emission scanning electron microscopy, transmission electron microscopy, and energy dispersive X-ray spectroscopy. The O and N content measured by an O/N analyser is 0.34% and 16.2%, respectively, and the C content by a C/S analyser is 4.87%.