Phase, microstructure evolution, and periodic density functional theory study of reduction and nitridation of V2O3 with clean ammonia gas

Abstract

Vanadium nitride (VN) has a wide range of application because of its excellent properties, which include high hardness, outstanding wear resistance, and good electrical conductivity. This study investigated the mechanism for the reduction and nitridation of V2O3 with clean ammonia gas, using both experimental and density functional theory (DFT) studies. The experimental results indicated that V2O3 could easily be converted to VN in an ammonia atmosphere at 500–800 °C. The reaction pathway to form VN was V2O3 → VNxO1–x → VN. Increasing the reaction temperature was conducive to an increase in the N content of VNxO1–x. A DFT study systematically revealed the adsorption of NHx and H on the V2O3 (0001) surface. The results showed that with the dissociation of NH3, its adsorption energy on the surface of vanadium oxide became higher. The whole reaction process could be divided into NH3 decomposition on the surface and the formation of H2O(g). Both of these were endothermic reactions, and the reaction step of generating H2O(g) needed a higher temperature. The bonding of V3c–N facilitated the desorption of O3c atoms to form H2O(g), which explained why VN can be prepared by the reaction of NH3 and V2O3.