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Title: A new oxidation based technique for artifact free TEM specimen preparation of nuclear graphite

Graphite is a key component in designs of current and future nuclear reactors whose in-service lifetimes are dependent upon the mechanical performance of the graphite. Irradiation damage from fast neutrons creates lattice defects which have a dynamic effect on the microstructure and mechanical properties of graphite. Transmission electron microscopy (TEM) can offer real-time monitoring of the dynamic atomic-level response of graphite subjected to irradiation; however, conventional TEM specimen-preparation techniques, such as argon ion milling itself, damage the graphite specimen and introduce lattice defects. It is impossible to distinguish these defects from the ones created by electron or neutron irradiation. Thus,to ensure that TEM specimens are artifact-free, a new oxidation-based technique has been developed. Bulk nuclear grades of graphite (IG-110 and NBG-18) and highly oriented pyrolytic graphite (HOPG) were initially mechanically thinned to ~60μm. Discs 3mm in diameter were then oxidized at temperatures between 575°C and 625°C in oxidizing gasses using a new jet-polisher-like set-up in order to achieve optimal oxidation conditions to create self-supporting electron-transparent TEM specimens. The quality of these oxidized specimens were established using optical and electron microscopy. Samples oxidized at 575°C exhibited large areas of electron transparency and the corresponding lattice imaging showed no apparent damage tomore » the graphite lattice.« less
Authors:
 [1] ;  [1] ; ORCiD logo [2] ; ORCiD logo [2] ;  [1] ; ORCiD logo [1]
  1. Boise State Univ., ID (United States). Micron School of Materials Science and Engineering
  2. Idaho National Lab. (INL), Idaho Falls, ID (United States)
Publication Date:
Report Number(s):
DOE-Boise State-0016427
Journal ID: ISSN 0022-3115; PII: S0022311518301223
Grant/Contract Number:
SC0016427
Type:
Accepted Manuscript
Journal Name:
Journal of Nuclear Materials
Additional Journal Information:
Journal Volume: 505; Journal Issue: C; Journal ID: ISSN 0022-3115
Publisher:
Elsevier
Research Org:
Boise State Univ., ID (United States)
Sponsoring Org:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22); Idaho National Lab. (INL), Idaho Falls, ID (United States)
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; 22 GENERAL STUDIES OF NUCLEAR REACTORS; Graphite; Tranmission electron microscopy; oxidation
OSTI Identifier:
1432367