X-Ray photoelectron spectroscopy of some uranium oxide phases

Allen, G. C.; Crofts, J.A.; Curtis, Michael T.; Tucker, Philip M.; Chadwick, David; Hampson, Peter

doi:10.1039/dt9740001296

Cited by 139 publications

(63 citation statements)

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“…Then, one can conclude that the U4f 7/2 BE for U(VI) oxides is close to 382.0 eV, whereas it ranges from 380.2 to 380.8 eV for U(IV) compounds. These values are in agreement with those already reported in the literature for UO 2 [3,35,36] and for UO 3 . [3,35 -37] Concerning U 3 O 8 , the published data [3,38] report the presence of a single uranium contribution around 381.0 eV corresponding to an average value of the contributions we have measured for this solid.…”

Section: X-ray Photoelectron Spectroscopysupporting

confidence: 93%

X‐ray photoreduction of U(VI)‐bearing compounds

Mercier‐Bion

Drot

Ehrhardt

et al. 2011

Surface & Interface Analysis

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During XPS analysis, the soft X-ray-induced reduction of metals such as Cr(VI) and Ce(IV) in oxides has been reported in the literature and some mechanisms have been proposed to explain this phenomenon. The reduction of U(VI) by the beam during X-ray Photoelectron Spectroscopy has been already reported in the literature but only for U(VI) sorbed or precipitated onto solids with reducing properties (as micas or pyrites) for whose Fe(II) can also induce the reduction of U(VI), or onto TiO2 whose the photocatalytic properties are well known. The objective of this paper is to investigate the effects of X-ray beam on U(VI) bulk compounds (UO3, UO2(OH)2, (UO2)2SiO4, UO2(CH3COO)2 and UO2C2O4). Successive U4f, U5f, C1s XPS spectra were recorded and compared as a function of the irradiation time. The XPS photoreduction of U(VI) into U(IV) is only observed for uranyl compounds containing organic matter (uranyl acetate and uranyl oxalate). Considering the evolution of the C1s signal during the X-ray irradiation, a significant decrease of the C O component simultaneously to the U(VI) reduction is observed, which suggests a desorption of CO or other volatile organic products from the solid surface. All these results on U(VI) bulk compounds indicate the important role of organic carbon species in the photoreduction process and to explain these observations, a photoreduction mechanism has been suggested

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Section: X-ray Photoelectron Spectroscopysupporting

confidence: 93%

X‐ray photoreduction of U(VI)‐bearing compounds

Mercier‐Bion

Drot

Ehrhardt

et al. 2011

Surface & Interface Analysis

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show abstract

“…As far as these two observations are concerned, there is no objection against classifying the MUO 3 as monovalent compounds. However, the XPS spectra of these uranates clearly show doublet structures for the U4f peaks, indicating a mixed valence (for NaUO 3 (29) and similar results were observed by the authors on KUO 3 and RbUO 3 ). The observed discrepancy bears much resemblance to the situation encountered for BaBiO 3 : Formally, Bi has a valence of +4, but it was shown on various occasions that a disproportionation in Bi 3þ and Bi 5þ occurs, also on the basis of neutron diffraction data refinement (30,31) and bond length-bond valence considerations (32), XPS data (33) and EXAFS measurements (34).…”

Section: Mixed Valence Uranatesupporting

confidence: 81%

“…They can be assigned valences of 5.33 by BVS calculation. In XPS, the compound is identified as a multivalent compound with U IV and U VI valences (29). It is unclear if the mixed valence character of this oxide as seen with XPS is a consequence of final-state effects or is rather due to actual mixed or intermediate valence on the crystallographic level or the electronic level.…”

Section: Mixed Valence Uranatementioning

confidence: 99%

The Local Uranium Environment in Cesium Uranates: A Combined XPS, XAS, XRD, and Neutron Diffraction Analysis

Berghe

Verwerft²,

Laval³

et al. 2002

Journal of Solid State Chemistry

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“…[7] In addition, we also observe two shake-up satellite peaks presented, which positions are at 387.3 and 397.6 eV, respectively. The difference between the main oxide peaks and their respective satellites is 7.1 and 6.6 eV, that is in agreement with the reported value by Colmenares [8] and Allen et al, [9] and indicates that the uranium oxide formed on the outermost surface is a stoichiometric UO 2 . The data collected from Nb 3d revealed that the core-level photoelectron peaks for Nb 3d 5/2 and Nb 3/2 are at 207.2 and 210.0 eV, respectively.…”

Section: Analysis Of As-received Surfacesupporting

confidence: 81%

Investigation of oxidation of a U‐2.5 wt% Nb alloy in air at low temperatures: kinetic study and oxide characterization

Yang

Wang

Luo

et al. 2008

Surface & Interface Analysis

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Alloying uranium with niobium can greatly enhance the corrosion resistance of metallic uranium. In the present article, the oxidation behavior of a U-2.5 wt% Nb alloy in air over the temperature range 333 to 573 K was investigated. XPS technique was employed to characterize the oxide products. The results of oxidation-rate curves show that at temperatures below 353 K the oxidation of U-2.5 wt% Nb alloy follows a parabolic-rate law, and in the temperature range of 373-423 K paralinear rate laws seem to apply, however, above 473 K linear laws are observed. The oxidation-rate dependence of temperature is obtained, and the activation energies for different oxidation stages are determined. The XPS analysis indicates that under experimental conditions the predominant oxide formed on the outer surface is stoichiometric UO 2.0 intermixed with Nb 2 O 5 , and below the outmost thin layer, an inner oxide layer consisting of UO 2 , NbO is presented.

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X-Ray photoelectron spectroscopy of some uranium oxide phases

Cited by 139 publications

References 0 publications

X‐ray photoreduction of U(VI)‐bearing compounds

X‐ray photoreduction of U(VI)‐bearing compounds

The Local Uranium Environment in Cesium Uranates: A Combined XPS, XAS, XRD, and Neutron Diffraction Analysis

Investigation of oxidation of a U‐2.5 wt% Nb alloy in air at low temperatures: kinetic study and oxide characterization

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