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UNIVERSITY OF BUCHAREST
FACULTY OF PHYSICS Guest
2024-11-22 1:44 |
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Conference: Bucharest University Faculty of Physics 2021 Meeting
Section: Optics, Spectroscopy, Plasma and Lasers
Title:
Control of tungsten surface roughness by thermal and plasma treatments
Authors:
Lavinia Gabriela CARPEN (1,2), Tomy ACSENTE (1), Bogdan BITA (1,2), Valentina MARASCU (1), Veronica SATULU (1), Alina ARDELEANU (2), Gheorghe DINESCU (1,2)
*
Affiliation:
1) INFLPR, Atomistilor 409 str, Bucharest- Magurele, Romania
2) University of Bucharest, Faculty of Physics, Atomiştilor 405 str, Magurele, Bucharest, 077125, Romania
E-mail
lavinia.carpen@inflpr.ro
Keywords:
Tungsten, Fusion technology, Oxidation, Reduction, Hydrogen plasma
Abstract:
Tungsten (W) surface behavior in extreme thermal conditions and after plasma interaction represents an issue truly relevant to Plasma Facing Components (PFC) in next-generation reactors like ITER [1]. The potential of oxidation, surface exfoliation and increase roughness can lead to core contamination, because the surface properties will be modified, which may lead to the adverse performance of a fusion device. Because the appearance of oxides on the surfaces of PFC is extremely undesirable, the reduction of tungsten oxides has increasingly become the subject of ITER research. In this work, we focus on the evaluation of tungsten surface behavior after a two-step process, characterized by a thermal oxidation followed by a reduction in H2 plasma [2]. Both processing steps were performed using a linear furnace allowing the heating of the samples simultaneous with plasma ignition. We used an ITER-like laboratory model flat, uniform, large W surface (30x30x3mm3) for these experiments. The oxidation of the samples was performed in air at a temperature of 800 OC for four hours. Further on, two types of reduction processes in H2 plasma were performed: at room temperature and by heating the sample at 800 OC. Each sample was characterized using profilometry (roughness), scanning electron microscopy SEM (morphology) and X-ray photoelectron spectroscopy XPS (chemical composition). After oxidation, the roughness increases from 100 nm to 13000 nm, remaining in this range after plasma reduction at room temperature; still, plasma reduction at 800 OC results in a final roughness of 2000 nm. The results show that after oxidation the surface chemistry is dominated by WO3 and this oxide is totally reduced to metallic W only at a higher temperature. Therefore, we highlight that this type of two-step approach can remove W oxide from surfaces and also can produce rough W surfaces starting from smooth surfaces.
References:
[1] S. Kajita, W. Sakaguchi, N. Ohno, N. Yoshida, T.Saeki- Nucl. Fusion 49 (2009)
[2] A. Vesel, M. Mozetic, M. Balat-Pichelin- Thin Solid Films 591 B (2015)
Acknowledgement:
We acknowledge the financial support in the frame of the projects: EUROfusion Consortium WPEDU-RO.
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