Dense-film preparation of zirconium oxide by self-oxidation in air

Highlights: • Dense oxide film was formed on the surface of metallic zirconium. • Analyzed microstructure, composition, and crystal structure of the prepared film. • The prepared oxide film exhibited a layered structure. • Outermost layer of the oxide film is monoclinic ZrO2. • Growth rate of the oxide film followed the parabolic rate law. For the formation of a dense oxide film for use as an anticorrosion film with self-diagnosis and self-healing functions on the surface of structural materials, liquid blankets, and liquid divertors of thermonuclear fusion reactors, we investigated the self-oxidation of zirconium (Zr) at 500°C in air. The microstructure, composition (O/Zr ratio), crystal structure, and formation mechanism of the film were clarified through scanning electron microscopy, energy dispersive X-ray analysis, and X-ray diffraction analysis. It was demonstrated that the dense oxide film could be prepared, and its film exhibited a continuous and layered structure that consists of multiple phases. The outermost surface was unstrained monoclinic ZrO₂. The growth of the oxide film adheres to a parabolic rate law.