Zirconium hydride is susceptible to dehydrogenation at elevated temperatures. In this study, zirconium hydride was oxidized by in situ oxidation in a CO2 atmosphere at temperatures ranging from 550 to 700 °C for 10 h. The morphology, elemental distribution, phase structure, and hydrogen barrier performance of the resulting oxide films were systematically characterized using SEM, EDS, XRD, film adhesion and microhardness tests, and dehydrogenation experiments. At 550–600 °C, the formed oxide films are thin and non-uniform, containing numerous micropores and cracks, which results in limited hydrogen barrier performance. When the oxidation temperature is increased to 650 °C, a better balance between the oxidation reaction and diffusion processes is achieved. This leads to the formation of a dense, continuous, and uniform ZrO2 film with strong adhesion to the substrate. As a result, the initial dehydrogenation temperature increases to 660 °C, while both the dehydrogenation rate and cumulative hydrogen release are significantly reduced, indicating the best overall hydrogen resistance. However, further increasing the oxidation temperature to 700 °C causes an excessively high oxidation rate, which introduces large growth and thermal stresses. These stresses promote the formation of microcracks in the oxide film, weaken the interfacial bonding strength, and consequently reduce the hydrogen barrier performance. The results demonstrate that the hydrogen permeation resistance of the oxide film is mainly governed by film compactness, defect evolution, and interfacial integrity. Based on these findings, 650 °C is identified as the optimal processing temperature for producing a high-quality hydrogen-resistant ZrO2 film on zirconium hydride under a CO2 atmosphere.
Cui et al. (Tue,) studied this question.