Preparation and properties of improved Al_2O_3 based MOD coatings as tritium permeation barrier

摘要

Four kinds of well-crystallized tritium permeation barrier coatings, including gamma-Al2O3, alpha-Al2O3, gamma-Al2O3/Cr2O3 and alpha-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 alpha-Al2O3 and alpha-Al2O3 /Cr2O3 double-layer coatings. The results showed that the alpha-Al2O3 coating exhibited a pure phase structure, which was entirely and directly transformed from the gamma-Al2O3 at an annealing temperature of 1000 degrees C, and no obvious substrate oxides were formed. An unannealed Cr2O3 MOD layer with a thickness of 0.8 mu m 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 alpha-Al2O3 did not decrease. The corrosion resistance (1.068 x 10(-7) A/cm(2)) and nanohardness (18.49 GPa) of the alpha-Al2O3/Cr2O3 double-layer coating improved compared to those of gamma-Al2O3, alpha-Al2O3, and gamma-Al2O3/Cr2O3 coatings. In contrast, the deuterium permeation test showed that the alpha-Al2O3 MOD coating had the lowest deuterium ion current at temperatures of 400(similar to) 600 degrees C of the films considered in this study, demonstrating better resistance to deuterium permeation. Relevant mechanisms and explanations are discussed in detail.