Nanoscale oxygen defect gradients in UO2+x surfaces.
Steven R SpurgeonMichel SassiColin OphusJoanne E StubbsEugene S IltonEdgar C BuckPublished in: Proceedings of the National Academy of Sciences of the United States of America (2019)
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 [Formula: see text] 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 [Formula: see text] surface oxidation.
Keyphrases
- electron microscopy
- molecular dynamics
- hydrogen peroxide
- atomic force microscopy
- deep learning
- high resolution
- drinking water
- magnetic resonance
- health risk
- risk assessment
- gene expression
- escherichia coli
- human milk
- molecular dynamics simulations
- staphylococcus aureus
- heavy metals
- density functional theory
- nitric oxide
- optical coherence tomography
- mass spectrometry
- dna methylation
- climate change
- cystic fibrosis
- low birth weight
- quantum dots