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Title: Morphologies of tungsten nanotendrils grown under helium exposure

Nanotendril “fuzz” will grow under He bombardment under tokamak-relevant conditions on tungsten plasma-facing materials in a magnetic fusion energy device. We have grown tungsten nanotendrils at low (50 eV) and high (12 keV) He bombardment energy, in the range 900–1000 °C, and characterized them using electron microscopy. Low energy tendrils are finer (~22 nm diameter) than high-energy tendrils (~176 nm diameter), and low-energy tendrils have a smoother surface than high-energy tendrils. Cavities were omnipresent and typically ~5–10 nm in size. Oxygen was present at tendril surfaces, but tendrils were all BCC tungsten metal. Electron diffraction measured tendril growth axes and grain boundary angle/axis pairs; no preferential growth axes or angle/axis pairs were observed, and low-energy fuzz grain boundaries tended to be high angle; high energy tendril grain boundaries were not observed. We speculate that the strong tendency to high-angle grain boundaries in the low-energy tendrils implies that as the tendrils twist or bend, strain must accumulate until nucleation of a grain boundary is favorable compared to further lattice rotation. Finally, the high-energy tendrils consisted of very large (>100 nm) grains compared to the tendril size, so the nature of the high energy irradiation must enable faster growth with less latticemore » rotation.« less
Authors:
 [1] ;  [2] ;  [2] ;  [1] ;  [1] ;  [3] ;  [3] ;  [1]
  1. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
  2. Univ. of California-San Diego, La Jolla, CA (United States)
  3. AppFive, Tempe, AZ (United States)
Publication Date:
Grant/Contract Number:
AC05-00OR22725
Type:
Accepted Manuscript
Journal Name:
Scientific Reports
Additional Journal Information:
Journal Volume: 7; Journal Issue: 1; Journal ID: ISSN 2045-2322
Publisher:
Nature Publishing Group
Research Org:
Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
Sponsoring Org:
USDOE Office of Science (SC)
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; 70 PLASMA PHYSICS AND FUSION TECHNOLOGY
OSTI Identifier:
1344265

Wang, Kun, Doerner, R. P., Baldwin, Matthew J., Meyer, Fred W., Bannister, Mark E., Darbal, Amith, Stroud, Robert, and Parish, Chad M.. Morphologies of tungsten nanotendrils grown under helium exposure. United States: N. p., Web. doi:10.1038/srep42315.
Wang, Kun, Doerner, R. P., Baldwin, Matthew J., Meyer, Fred W., Bannister, Mark E., Darbal, Amith, Stroud, Robert, & Parish, Chad M.. Morphologies of tungsten nanotendrils grown under helium exposure. United States. doi:10.1038/srep42315.
Wang, Kun, Doerner, R. P., Baldwin, Matthew J., Meyer, Fred W., Bannister, Mark E., Darbal, Amith, Stroud, Robert, and Parish, Chad M.. 2017. "Morphologies of tungsten nanotendrils grown under helium exposure". United States. doi:10.1038/srep42315. https://www.osti.gov/servlets/purl/1344265.
@article{osti_1344265,
title = {Morphologies of tungsten nanotendrils grown under helium exposure},
author = {Wang, Kun and Doerner, R. P. and Baldwin, Matthew J. and Meyer, Fred W. and Bannister, Mark E. and Darbal, Amith and Stroud, Robert and Parish, Chad M.},
abstractNote = {Nanotendril “fuzz” will grow under He bombardment under tokamak-relevant conditions on tungsten plasma-facing materials in a magnetic fusion energy device. We have grown tungsten nanotendrils at low (50 eV) and high (12 keV) He bombardment energy, in the range 900–1000 °C, and characterized them using electron microscopy. Low energy tendrils are finer (~22 nm diameter) than high-energy tendrils (~176 nm diameter), and low-energy tendrils have a smoother surface than high-energy tendrils. Cavities were omnipresent and typically ~5–10 nm in size. Oxygen was present at tendril surfaces, but tendrils were all BCC tungsten metal. Electron diffraction measured tendril growth axes and grain boundary angle/axis pairs; no preferential growth axes or angle/axis pairs were observed, and low-energy fuzz grain boundaries tended to be high angle; high energy tendril grain boundaries were not observed. We speculate that the strong tendency to high-angle grain boundaries in the low-energy tendrils implies that as the tendrils twist or bend, strain must accumulate until nucleation of a grain boundary is favorable compared to further lattice rotation. Finally, the high-energy tendrils consisted of very large (>100 nm) grains compared to the tendril size, so the nature of the high energy irradiation must enable faster growth with less lattice rotation.},
doi = {10.1038/srep42315},
journal = {Scientific Reports},
number = 1,
volume = 7,
place = {United States},
year = {2017},
month = {2}
}