Study on influence factors of permeation reduction factor of Al2O3-hydrogen isotopes permeation barriers

Hydrogen isotopes permeation barriers (HIPB) play an important role in reducing hydrogen isotopes permeation and leakage in hydrogen energy and thermonuclear fusion energy. In this study, the Al2O3-HIPB were prepared on 316L stainless steel by RF magnetron sputtering. The impacts of coating thickness and annealing temperature of as-deposited coatings on deuterium permeation reduction factor (D-PRF) are studied in detail. With increasing thickness of coatings from 0.2 μm to 1.6 μm, the D-PRF did not rise significantly, which indicated that coating surface, for thin coatings, played more important role in impeding deuterium permeation than coating interior. As a result of further crystallization and grain growth, the 700 °C-annealed Al2O3 coatings had stronger ability to impede deuterium permeation than 600 °C-annealed Al2O3 coatings. This further proofs that grain boundaries may be a short-cut path for deuterium diffusion in Al2O3 coatings. The D-PRF drastically decreased when the annealing temperature reaches 800 °C, which might be ascribed to the new phases form and the coating cracks appearance after 800 °C annealing.