Study on the preparation of high-quality VN-19 and the mechanism of its isothermal kinetics

Abstract

In this study, high-quality VN (VN-19 level) was synthesized, and the reaction kinetics of its synthesis were explored through isothermal kinetic analysis. After a series of optimization experiments, the mild atmospheric-pressure conditions for synthesizing VN were determined as follows: a nitrogen flow rate of 160 mL min⁻¹, holding temperature of 1450 °C and holding time of 0.5 h, requiring no high-pressure equipment and shortening reaction time. Under these conditions, the nitrogen content of the product was 18.69 wt%, reaching the highest quality VN-19 level (18–20 wt%) defined in GB/T 20567-2020. The first-reported isothermal kinetic analysis revealed three distinct reaction stages with characteristic activation energies: (1) interface chemical reaction rate control stage, (2) mixing rate control stage, and (3) diffusion rate control stage; the activation energies (E_a) of the three stages were 79.8570, 62.9511 and 72.5923 kJ mol⁻¹, respectively. The reaction rate constant initially showed a sharp increase and then gradually levelled off. This work provides a fundamental kinetic insight that can advance the understanding of transition metal nitride formation mechanisms.