Unraveling the atomic structure evolution of titanium nitride upon oxidation

Abstract Oxidation-induced structural failure is a major issue in high-strength non-oxide ceramics, yet the atomic-level structural changes underlying phase transformation have remained elusive. Here, we present a study that employs state-of-the-art aberration-corrected environmental transmission electron microscopy to unravel the atomic-scale structural evolution of titanium nitride during dynamic oxidation. Our findings reveal two distinct reaction pathways, each characterized by the migration of titanium atoms through the formation of chains of titanium vacancies and staggered titanium vacancies. We demonstrate that these pathways are significantly influenced by both crystal orientation and surface curvature. Our rigorous First-principles calculations elucidate the underlying mechanism, revealing that titanium atoms have the highest kinetics for moving out along the {200} family, while their movement is modulated by surface strain involved in curvature changes. This insight is further substantiated by macroscopic oxidation experiments, affirming that the precision control of material orientation indeed enhances antioxidative performance. Our research holds immense scientific and technological significance, advancing our understanding of materials' antioxidation performance and ultimately bolstering durability and extending lifespan.