Gas-driven hydrogen permeation through tungsten-coated graphite

• Published in: Journal of nuclear materials 2011-08, Vol.415 (1), p.S688-S691
• Main Authors: Golubeva, A.V., Spitsyn, A.V., Mayer, M., Cherkez, D.I., Schwarz-Selinger, T., Koch, F., Lindig, S., Skovoroda, A.A.
• Format: Article
• Language: English
• Subjects: Coatings; Deposition; Graphite; Hydrogen storage; Penetration; Permeation; Porosity; Tungsten
• ISSN: 0022-3115; 1873-4820
• DOI: 10.1016/j.jnucmat.2011.01.106

Hydrogen gas-driven permeation through graphite coated with different types of tungsten coatings with thicknesses up to 200μm has been investigated. The substrate material was fine-grain graphite R5710 and R6710, which properties with respect to hydrogen transport are well known [1]. Magnetron-sputtered W coatings of thicknesses 1 and 3μm and two coatings of ASDEX Upgrade were investigated: A 3μm thick layer of tungsten deposited by physical vapor deposition (PVD-W) and 200μm thick layers of tungsten deposited by plasma-spaying in vacuum (VPS-W). The gas-driven permeation was investigated at a pressure gradient of 10−2–150Pa. The gas-driven permeation occurs through the carbon base-materials by hydrogen molecular gas flow through the internal porosity network rather than hydrogen atom diffusion through the graphite lattice. It was found that W coatings with thicknesses up to 3μm are transparent for hydrogen gas penetration and do not influence the permeability of coated fine-grain graphite, because the open porosity system of graphite remains open. Even a 200μm thick layer of VPS-W has an open system of connected pores, which connects the front and rear surfaces of the deposited layer.