Deuterium plasma exposure of thin oxide films on tungsten - oxygen removal and deuterium uptake
Recently we have shown that thin (33 to 55 nm) oxide films on tungsten (W) prevent deuterium (D) uptake from a low-temperature plasma (5 eV/D; 370 K; 1.4 × 1024 D/m2) into metallic W. Here we continue this investigation with higher D fluence up to 2.3 × 1025 D/m2 and, additionally, with higher D ene...
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| Language: | English |
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Elsevier
2023-06-01
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| Series: | Nuclear Materials and Energy |
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| Online Access: | http://www.sciencedirect.com/science/article/pii/S2352179123000455 |
| _version_ | 1797801046080225280 |
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| author | Kristof Kremer Thomas Schwarz-Selinger Wolfgang Jacob |
| author_facet | Kristof Kremer Thomas Schwarz-Selinger Wolfgang Jacob |
| author_sort | Kristof Kremer |
| collection | DOAJ |
| description | Recently we have shown that thin (33 to 55 nm) oxide films on tungsten (W) prevent deuterium (D) uptake from a low-temperature plasma (5 eV/D; 370 K; 1.4 × 1024 D/m2) into metallic W. Here we continue this investigation with higher D fluence up to 2.3 × 1025 D/m2 and, additionally, with higher D energies up to 38 eV/D or a higher sample temperature of 500 K. We investigate the reduction mechanism of the oxide and determine under which conditions the permeation barrier effect for D breaks down. We show that during prolonged plasma exposure at 5 eV/D and 370 K, the W-enriched zone that forms at the surface of the oxide stops growing and continues to protect the oxide beneath it against further reduction. For a fluence of 1.6 × 1025 D/m2, an originally 55 nm thick oxide film reduces D uptake into the metal by 99 %. D enters the metal solely by small cracks in the oxide that form during reduction by the plasma. For higher temperature or D energies, the reduction becomes stronger and more inhomogeneous. D uptake into the metal increases proportional to the area of oxide/metal interface on which the oxide is reduced. The new experiments confirm our previous assumption that D uptake into W is blocked due to the difference in enthalpy of solution of D in W oxide and metallic W. D can only enter the metal once the oxide at the interface is sufficiently reduced. Based on the obtained oxide reduction rates, we made a first tentative estimate of the relevance of naturally occurring W oxide films for D uptake in the plasma-facing components of a fusion reactor. We found that the natural oxide will have none or only a very minor effect in this case. |
| first_indexed | 2024-03-13T04:44:27Z |
| format | Article |
| id | doaj.art-6ab13339902641728d1dcd3d7cdc8d61 |
| institution | Directory Open Access Journal |
| issn | 2352-1791 |
| language | English |
| last_indexed | 2024-03-13T04:44:27Z |
| publishDate | 2023-06-01 |
| publisher | Elsevier |
| record_format | Article |
| series | Nuclear Materials and Energy |
| spelling | doaj.art-6ab13339902641728d1dcd3d7cdc8d612023-06-19T04:28:24ZengElsevierNuclear Materials and Energy2352-17912023-06-0135101406Deuterium plasma exposure of thin oxide films on tungsten - oxygen removal and deuterium uptakeKristof Kremer0Thomas Schwarz-Selinger1Wolfgang Jacob2Max-Planck-Institut für Plasmaphysik, 85748 Garching, Germany; Physik-Department E28, Technische Universität München, 85747 Garching, Germany; Corresponding author.Max-Planck-Institut für Plasmaphysik, 85748 Garching, GermanyMax-Planck-Institut für Plasmaphysik, 85748 Garching, GermanyRecently we have shown that thin (33 to 55 nm) oxide films on tungsten (W) prevent deuterium (D) uptake from a low-temperature plasma (5 eV/D; 370 K; 1.4 × 1024 D/m2) into metallic W. Here we continue this investigation with higher D fluence up to 2.3 × 1025 D/m2 and, additionally, with higher D energies up to 38 eV/D or a higher sample temperature of 500 K. We investigate the reduction mechanism of the oxide and determine under which conditions the permeation barrier effect for D breaks down. We show that during prolonged plasma exposure at 5 eV/D and 370 K, the W-enriched zone that forms at the surface of the oxide stops growing and continues to protect the oxide beneath it against further reduction. For a fluence of 1.6 × 1025 D/m2, an originally 55 nm thick oxide film reduces D uptake into the metal by 99 %. D enters the metal solely by small cracks in the oxide that form during reduction by the plasma. For higher temperature or D energies, the reduction becomes stronger and more inhomogeneous. D uptake into the metal increases proportional to the area of oxide/metal interface on which the oxide is reduced. The new experiments confirm our previous assumption that D uptake into W is blocked due to the difference in enthalpy of solution of D in W oxide and metallic W. D can only enter the metal once the oxide at the interface is sufficiently reduced. Based on the obtained oxide reduction rates, we made a first tentative estimate of the relevance of naturally occurring W oxide films for D uptake in the plasma-facing components of a fusion reactor. We found that the natural oxide will have none or only a very minor effect in this case.http://www.sciencedirect.com/science/article/pii/S2352179123000455TungstenTungsten oxidePermeation barrierHydrogen uptakeHydrogen retentionPlasma irradiation |
| spellingShingle | Kristof Kremer Thomas Schwarz-Selinger Wolfgang Jacob Deuterium plasma exposure of thin oxide films on tungsten - oxygen removal and deuterium uptake Nuclear Materials and Energy Tungsten Tungsten oxide Permeation barrier Hydrogen uptake Hydrogen retention Plasma irradiation |
| title | Deuterium plasma exposure of thin oxide films on tungsten - oxygen removal and deuterium uptake |
| title_full | Deuterium plasma exposure of thin oxide films on tungsten - oxygen removal and deuterium uptake |
| title_fullStr | Deuterium plasma exposure of thin oxide films on tungsten - oxygen removal and deuterium uptake |
| title_full_unstemmed | Deuterium plasma exposure of thin oxide films on tungsten - oxygen removal and deuterium uptake |
| title_short | Deuterium plasma exposure of thin oxide films on tungsten - oxygen removal and deuterium uptake |
| title_sort | deuterium plasma exposure of thin oxide films on tungsten oxygen removal and deuterium uptake |
| topic | Tungsten Tungsten oxide Permeation barrier Hydrogen uptake Hydrogen retention Plasma irradiation |
| url | http://www.sciencedirect.com/science/article/pii/S2352179123000455 |
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