29th Symposium on Fusion Technology (SOFT 2016)

P3.188 Deuterium permeation and retention behaviors in erbium oxide-iron multilayer coatings

7 Sep 2016, 11:00

1h 20m

Foyer 2A (2nd floor), 3A (3rd floor) (Prague Congress Centre)

Board: 188

Poster I. Materials Technology P3 Poster session

Speaker

Seira Horikoshi (Graduate School of Integrated Science and Technology)

Description

To establish liquid lithium-lead blanket concepts, the development of a functional coating as a tritium permeation barrier with corrosion resistance is required. In our previous study, erbium oxide (erbia)-iron two-layer coatings showed a better compatibility than erbia single-layer coatings with keeping a high permeation reduction factor (PRF). In this study, hydrogen isotope migration behaviors in ceramics-metal multilayer coatings have been elucidated for a further improvement of fueling system and radiological safety. First, erbia coatings (thickness: 1‒3 μm) were fabricated by filtered vacuum arc deposition (VAD) on reduced activation ferritic/martensitic steel F82H substrates. Second, iron layer was fabricated by radio-frequency magnetron sputtering (1 μm) or covered with an iron foil (10 μm) on the erbia coating. An erbia-iron-erbia three-layer coating was also fabricated by the VAD on the erbia-iron coating. Subsequently, deuterium permeation experiments were carried out in the temperature range of 773‒973 K. After the permeation tests, deuterium was introduced into the samples at 873 K with 80 kPa deuterium. Depth profiles of deuterium concentration in the coatings were evaluated by the D(³3He, p)⁴4He nuclear reaction. The erbia-iron coated samples with different iron layer thickness showed no significant difference in deuterium permeability, indicating that deuterium permeation in the erbia-iron was controlled by diffusion in the erbia layer. The erbia-iron-erbia coating showed a PRF of up to 10⁴4 due to a contribution of two diffusion barriers of inner and outer erbia layers. However, the PRF was less than that of the erbia sample coated on both sides of the substrate, possibly derived from a different recombination process on the back surface. Moreover, the erbia-iron-erbia coating had three times higher D concentration than the erbia-Fe coating (1.9 × 10¹⁵15 atom cm^‒2‒2), which suggests tritium inventory in the multi-layer coatings should be taken into account.