Blisters formed by D plasma exposure in an electron-transparent tungsten sample. (December 2018)

• Record Type: Journal Article
• Authors: Manhard, Armin; Gao, Liang
• Is Part Of: Nuclear materials and energy. Volume 17(2018)
• Page Start: 248
• Page End: 252
• Publication Date: 2018-12
• Subjects: Tungsten -- Deuterium -- Plasma exposure -- Scanning transmission electron microscopy -- Blister nucleation conditions -- Defect creation; Nuclear energy -- Periodicals; Nuclear fuels -- Periodicals; Nuclear reactors -- Materials -- Periodicals; Radioactive substances -- Periodicals; 621.4833
• DOI: 10.1016/j.nme.2018.11.014
• Languages: English
• ISSNs: 2352-1791

Abstract

Highlights: A W sample for transmission electron microscopy was exposed to D plasma at 230 K. Blisters occurred even in the transparent region near the central perforation. A sample thickness threshold for blister formation of about 40–50 nm was found. The dislocation density was increased by two orders of magnitude due to blistering. Abstract: By irradiating a tungsten sample for transmission electron microscopy with deuterium plasma at 230 K, we created a high density of blisters below the plasma-exposed surface. Blisters were even found in the electron-transparent region close to the central perforation. We determined the abundance of blisters depending on the local sample thickness and found that no blisters were formed for thicknesses below about 45 nm for these specific plasma exposure conditions. After removing the approximately 10 nm thick, defect-rich layer at the plasma-exposed surface, which corresponds roughly to the ion implantation zone, by electrochemical polishing, we were able to clearly identify material distortions and dislocation network halos corresponding to blisters by scanning transmission electron microscopy. Compared with unirradiated tungsten of the same grade, we found that in the blister zone the average dislocation density is about 2 orders of magnitude higher, which may, in addition to gas enclosed in blister cavities, explain enhanced deuterium retention in blistered tungsten samples. The proof-of-principle experiments described in this article have the potential to provide constraints for theoretical models for blister nucleation. They also pave the way for direct investigations of the spatial correlation of deuterium-plasma-induced blisters and intrinsic defects. Graphical abstract: