Preparation and properties of improved Al2O3 based MOD coatings as tritium permeation barrier

Abstract

Four kinds of well-crystallized tritium permeation barrier coatings, including γ-Al2O3, α-Al2O3, γ-Al2O3/Cr2O3 and α-Al2O3/Cr2O3, were prepared by the metal organic decomposition (MOD) method using a dipping technique. In this study, we concentrated on the preparation and properties of α-Al2O3 and α-Al2O3/Cr2O3 double-layer coatings. The results showed that the α-Al2O3 coating exhibited a pure phase structure, which was entirely and directly transformed from the γ-Al2O3 at an annealing temperature of 1000 °C, and no obvious substrate oxides were formed. An unannealed Cr2O3 MOD layer with a thickness of 0.8 μm featured higher crystallization and was taken as a buffer layer. However, the template effect of Cr2O3 was not obvious because the formation temperature of the α-Al2O3 did not decrease. The corrosion resistance (1.068 × 10−7 A/cm2) and nanohardness (18.49 GPa) of the α-Al2O3/Cr2O3 double-layer coating improved compared to those of γ-Al2O3, α-Al2O3, and γ-Al2O3/Cr2O3 coatings. In contrast, the deuterium permeation test showed that the α-Al2O3 MOD coating had the lowest deuterium ion current at temperatures of 400 ˜ 600 °C of the films considered in this study, demonstrating better resistance to deuterium permeation. Relevant mechanisms and explanations are discussed in detail.