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Title: Nanoscale oxygen defect gradients in UO 2+x surfaces

Abstract

Oxygen defects govern the behavior of a range of materials spanning catalysis, quantum computing, and nuclear energy. Understanding and controlling these defects is particularly important for the safe use, storage, and disposal of actinide oxides in the nuclear fuel cycle, since their oxidation state influences fuel lifetimes, stability, and the contamination of groundwater. However, poorly understood nanoscale fluctuations in these systems can lead to significant deviations from bulk oxidation behavior. Here we describe the use of aberration-corrected scanning transmission electron microscopy and electron energy loss spectroscopy to resolve changes in the local oxygen defect environment in U O 2 + x surfaces. We observe large image contrast and spectral changes that reflect the presence of sizable gradients in interstitial oxygen content at the nanoscale, which we quantify through first-principles calculations and image simulations. These findings reveal an unprecedented level of excess oxygen incorporated in a complex near-surface spatial distribution, offering additional insight into defect formation pathways and kinetics during U O 2 surface oxidation.

Authors:
ORCiD logo [1];  [1];  [2]; ORCiD logo [3];  [1]; ORCiD logo [1]
  1. Pacific Northwest National Lab. (PNNL), Richland, WA (United States)
  2. Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
  3. The Univ. of Chicago, Chicago, IL (United States)
Publication Date:
Research Org.:
Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
Sponsoring Org.:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
OSTI Identifier:
1564069
Grant/Contract Number:  
AC02-05CH11231
Resource Type:
Accepted Manuscript
Journal Name:
Proceedings of the National Academy of Sciences of the United States of America
Additional Journal Information:
Journal Volume: 116; Journal Issue: 35; Journal ID: ISSN 0027-8424
Publisher:
National Academy of Sciences, Washington, DC (United States)
Country of Publication:
United States
Language:
English
Subject:
38 RADIATION CHEMISTRY, RADIOCHEMISTRY, AND NUCLEAR CHEMISTRY; actinide oxides; uraninite; surface oxidation; scanning transmission electron; microscopy; electron energy loss spectroscopy

Citation Formats

Spurgeon, Steven R., Sassi, Michel, Ophus, Colin, Stubbs, Joanne E., Ilton, Eugene S., and Buck, Edgar C. Nanoscale oxygen defect gradients in UO2+x surfaces. United States: N. p., 2019. Web. doi:10.1073/pnas.1905056116.
Spurgeon, Steven R., Sassi, Michel, Ophus, Colin, Stubbs, Joanne E., Ilton, Eugene S., & Buck, Edgar C. Nanoscale oxygen defect gradients in UO2+x surfaces. United States. doi:10.1073/pnas.1905056116.
Spurgeon, Steven R., Sassi, Michel, Ophus, Colin, Stubbs, Joanne E., Ilton, Eugene S., and Buck, Edgar C. Fri . "Nanoscale oxygen defect gradients in UO2+x surfaces". United States. doi:10.1073/pnas.1905056116. https://www.osti.gov/servlets/purl/1564069.
@article{osti_1564069,
title = {Nanoscale oxygen defect gradients in UO2+x surfaces},
author = {Spurgeon, Steven R. and Sassi, Michel and Ophus, Colin and Stubbs, Joanne E. and Ilton, Eugene S. and Buck, Edgar C.},
abstractNote = {Oxygen defects govern the behavior of a range of materials spanning catalysis, quantum computing, and nuclear energy. Understanding and controlling these defects is particularly important for the safe use, storage, and disposal of actinide oxides in the nuclear fuel cycle, since their oxidation state influences fuel lifetimes, stability, and the contamination of groundwater. However, poorly understood nanoscale fluctuations in these systems can lead to significant deviations from bulk oxidation behavior. Here we describe the use of aberration-corrected scanning transmission electron microscopy and electron energy loss spectroscopy to resolve changes in the local oxygen defect environment in UO2+x surfaces. We observe large image contrast and spectral changes that reflect the presence of sizable gradients in interstitial oxygen content at the nanoscale, which we quantify through first-principles calculations and image simulations. These findings reveal an unprecedented level of excess oxygen incorporated in a complex near-surface spatial distribution, offering additional insight into defect formation pathways and kinetics during UO2 surface oxidation.},
doi = {10.1073/pnas.1905056116},
journal = {Proceedings of the National Academy of Sciences of the United States of America},
number = 35,
volume = 116,
place = {United States},
year = {2019},
month = {8}
}

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Works referenced in this record:

Revised effective ionic radii and systematic studies of interatomic distances in halides and chalcogenides
journal, September 1976


Fuel corrosion processes under waste disposal conditions
journal, November 2000