Topic
Uranium oxide
About: Uranium oxide is a research topic. Over the lifetime, 1582 publications have been published within this topic receiving 16903 citations.
Papers published on a yearly basis
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Papers
TL;DR: Results clearly indicate that U(VI) (as soluble uranyl ion) is readily reduced by green rust to U(IV) in the form of relatively insoluble UO2 nanoparticles, suggesting that the presence of green rusts in the subsurface may have significant effects on the mobility of uranium, particularly under iron-reducing conditions.
Abstract: Green rusts, which are mixed ferrous/ferric hydroxides, are found in many suboxic environments and are believed to play a central role in the biogeochemistry of Fe. Analysis by U LIII-edge X-ray absorption near edge spectroscopy of aqueous green rust suspensions spiked with uranyl (UVI) showed that UVI was readily reduced to UIV by green rust. The extended X-ray absorption fine structure (EXAFS) data for uranium reduced by green rust indicate the formation of a UO2 phase. A theoretical model based on the crystal structure of UO2 was generated by using FEFF7 and fitted to the data for the UO2 standard and the uranium in the green rust samples. The model fits indicate that the number of nearest-neighbor uranium atoms decreases from 12 for the UO2 structure to 5.4 for the uranium-green rust sample. With an assumed four near-neighbor uranium atoms per uranium atom on the surface of UO2, the best-fit value for the average number of uranium atoms indicates UO2 particles with an average diameter of 1.7 ± 0.6 nm....
467 citations
TL;DR: In this article, a thermodynamic assessment of the uranium-oxygen system is presented, and a consistent set of experimental data is selected among the numerous data in the literature on the phase diagram and oxygen chemical potential.
191 citations
TL;DR: A review of surface reactions of the complex uranium oxide systems with relevance to catalysis and the environment is given in this article, where the focus of the review is on surface science studies of defined structures of uranium oxides which are entirely on UO2 because of the lack of available model on other uranium oxide oxide systems.
186 citations
TL;DR: The major uranium phases were identified using analytical electron microscopy (AEM) combined with electron diffraction as uranyl phosphate (meta-autunite), uranium oxide (uraninite), and uranium metaphosphate [U(PO3)4].
Abstract: Electron beam techniques were used to characterize uranium-contaminated soils at the Fernald site in Ohio. Uranium particulates had been deposited on the soil through chemical spills and from the operation of an incinerator plant on the site. The major uranium phases were identified using analytical electron microscopy (AEM) combined with electron diffraction as uranyl phosphate (meta-autunite), uranium oxide (uraninite), and uranium metaphosphate [U(PO3)4]. The U(PO3)4 was found predominantly at an incinerator site at Fernald. Carbonate leaching in an oxygen environment has removed some of the U(IV) phases; however, U(PO3)4 has not been removed by any of the chemical remediation technologies tried to date. These observations suggest that an additional physical extraction procedure is needed to remove this phase. Some evidence suggests that the uranium has undergone weathering, resulting in its redistribution within the soil.
173 citations
TL;DR: The kinetics of the oxidation process are discussed on the basis of the results of the structural analysis, which involves a complex modification of the oxygen sublattice and the onset of complex superstructures for U(4)O(9) and U(3) O(7), associated with regular stacks of complex defects known as cuboctahedra, which consist of 13 oxygen atoms.
Abstract: This paper discusses uranium oxide crystal structure modifications that are observed during the low-temperature oxidation which transforms UO2 into U3O8. The symmetries and the structural parameters of UO2, β-U4O9, β-U3O7, and U3O8 were determined by refining neutron diffraction patterns on pure single-phase samples. Neutron diffraction patterns were also collected during the in situ oxidation of powder samples at 483 K. The lattice parameters and relative ratios of the four pure phases were measured during the progression of the isothermal oxidation. The transformation of UO2 into U3O8 involves a complex modification of the oxygen sublattice and the onset of complex superstructures for U4O9 and U3O7, associated with regular stacks of complex defects known as cuboctahedra, which consist of 13 oxygen atoms. The kinetics of the oxidation process are discussed on the basis of the results of the structural analysis.
166 citations
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Performance Metrics
| Year | Papers |
|---|---|
| 2025 | 16 |
| 2024 | 14 |
| 2023 | 25 |
| 2022 | 36 |
| 2021 | 25 |
| 2020 | 44 |