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Title: Damage tolerance of nuclear graphite at elevated temperatures

Nuclear-grade graphite is a critically important high-temperature structural material for current and potentially next generation of fission reactors worldwide. It is imperative to understand its damage-tolerant behaviour and to discern the mechanisms of damage evolution under in-service conditions. Here we perform in situ mechanical testing with synchrotron X-ray computed micro-tomography at temperatures between ambient and 1,000 °C on a nuclear-grade Gilsocarbon graphite. We find that both the strength and fracture toughness of this graphite are improved at elevated temperature. Whereas this behaviour is consistent with observations of the closure of microcracks formed parallel to the covalent-sp 2-bonded graphene layers at higher temperatures, which accommodate the more than tenfold larger thermal expansion perpendicular to these layers, we attribute the elevation in strength and toughness primarily to changes in the residual stress state at 800–1,000 °C, specifically to the reduction in significant levels of residual tensile stresses in the graphite that are ‘frozen-in’ following processing.
Authors:
 [1] ; ORCiD logo [2] ;  [3] ;  [4] ;  [5]
  1. Univ. of Oxford (United Kingdom). Dept. of Materials
  2. Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States). Materials Sciences Division
  3. Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States). Advanced Light Source
  4. Univ. of Bristol (United Kingdom). Center for Device Thermography and Reliability. H.H. Wills Physics Lab.
  5. Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States). Materials Sciences Division; Univ. of California, Berkeley, CA (United States). Dept. of Materials Science and Engineering
Publication Date:
Grant/Contract Number:
AC02-05CH11231; EP/N004493/1; EP/K024345/1
Type:
Accepted Manuscript
Journal Name:
Nature Communications
Additional Journal Information:
Journal Volume: 8; Journal ID: ISSN 2041-1723
Publisher:
Nature Publishing Group
Research Org:
Univ. of Oxford (United Kingdom); Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
Sponsoring Org:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22); Engineering and Physical Sciences Research Council (EPSRC)
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; 73 NUCLEAR PHYSICS AND RADIATION PHYSICS; materials for energy and catalysis; nuclear energy
OSTI Identifier:
1408441

Liu, Dong, Gludovatz, Bernd, Barnard, Harold S., Kuball, Martin, and Ritchie, Robert O.. Damage tolerance of nuclear graphite at elevated temperatures. United States: N. p., Web. doi:10.1038/ncomms15942.
Liu, Dong, Gludovatz, Bernd, Barnard, Harold S., Kuball, Martin, & Ritchie, Robert O.. Damage tolerance of nuclear graphite at elevated temperatures. United States. doi:10.1038/ncomms15942.
Liu, Dong, Gludovatz, Bernd, Barnard, Harold S., Kuball, Martin, and Ritchie, Robert O.. 2017. "Damage tolerance of nuclear graphite at elevated temperatures". United States. doi:10.1038/ncomms15942. https://www.osti.gov/servlets/purl/1408441.
@article{osti_1408441,
title = {Damage tolerance of nuclear graphite at elevated temperatures},
author = {Liu, Dong and Gludovatz, Bernd and Barnard, Harold S. and Kuball, Martin and Ritchie, Robert O.},
abstractNote = {Nuclear-grade graphite is a critically important high-temperature structural material for current and potentially next generation of fission reactors worldwide. It is imperative to understand its damage-tolerant behaviour and to discern the mechanisms of damage evolution under in-service conditions. Here we perform in situ mechanical testing with synchrotron X-ray computed micro-tomography at temperatures between ambient and 1,000 °C on a nuclear-grade Gilsocarbon graphite. We find that both the strength and fracture toughness of this graphite are improved at elevated temperature. Whereas this behaviour is consistent with observations of the closure of microcracks formed parallel to the covalent-sp2-bonded graphene layers at higher temperatures, which accommodate the more than tenfold larger thermal expansion perpendicular to these layers, we attribute the elevation in strength and toughness primarily to changes in the residual stress state at 800–1,000 °C, specifically to the reduction in significant levels of residual tensile stresses in the graphite that are ‘frozen-in’ following processing.},
doi = {10.1038/ncomms15942},
journal = {Nature Communications},
number = ,
volume = 8,
place = {United States},
year = {2017},
month = {6}
}