Microstructure evolution and mechanism during nitridation of carbon-containing internal gelation-derived zirconia

Zirconium nitride is an increasingly attractive material, owning to its wide range of applications. Nitridation with carbon as a reductant is a commonly used process for the preparation of transition metal nitrides. In this study, the nitridation of carbon-containing zirconia gels was studied as a method to synthesize zirconium nitride. The behavior of the gel upon heat treatment was investigated online. The evolution of the microstructure during nitridation was investigated using high-resolution transmission electron microscopy (HRTEM). The relationships between the gaseous species, crystalline phases, microstructure, and chemical elements of the resulting materials were established. The results showed that NH 3 , CH 2 O, CO 2 , CO, H 2 O, and HCN were the gaseous products in the nitridation process. Nucleation of the nanograins started with zirconium oxynitride . Transformation from oxynitride to nitride led to the occurrence of open-mouth-like defects on the particles. The enrichment of N atoms was accompanied by a core-shell structure. Finally, a systematic nitridation mechanism involving five stages was proposed. This study is important for understanding the nitridation process and controlling the structure and properties of transition metal nitrides.