Investigation of the conditions required for the formation of V(C,N) during carburization of vanadium or carbothermal reduction of V₂O₅ under nitrogen

Phase stability diagrams of V–C–N and V–O–C–N systems were constructed as a function of carbon activity, nitrogen partial pressure, oxygen partial pressure, and solution formation characteristics to determine the conditions for the formation of V(C,N) via the carburization of vanadium or carbothermal reduction of V₂O₅ under nitrogen. The diagram showed that only V, V₂C, and V(C,N) phases would be stable in the V–C–N system. From the diagram, it was also observed that only V(C,N) exists after the carburization of vanadium under nitrogen atmosphere more than 10⁻⁵ atm. The diagram of V–O–C–N system suggests that V₂O₅ can be reduced to V(C,N) without forming VO, owing to the high stability of the V(C,N) phase. Using these stability diagrams, the conditions for preparing V(C,N) from vanadium or V₂O₅ were deduced and the validity of the diagrams was verified using the experimental results.