Uranium oxides investigated by X-ray absorption and emission spectroscopies

Abstract

X-ray absorption and resonant X-ray emission measurements at the O 1s edge of the uranium oxides UO 2 , U 3 O 8 and UO 3 are presented. The spectral shapes of the O Kα X-ray emission spectra of UO 3 exhibit significant excitation energy dependence, from an asymmetric to a symmetric form, which differs from those of UO 2 and U 3 O 8 . This energy dependence is attributed to a significant difference in the oxygen-uranium hybridization between two different sites in the crystal structure of UO 3 . The spectral shapes of UO 2 and U 3 O 8 are also found to be different but without significant energy dependence. The experimental spectra of the valence and conduction bands of the uranium oxides are compared to the results of electronic structure calculations available in the literature.

Controlled Synthesis of Thorium and Uranium Oxide Nanocrystals

“…Among them, UO 2 , U 4 O 9 , U 3 O 8 and UO 3 are the most commonly encountered phases. UO 2 can easily be distinguished from U 3 O 8 and UO 3 because of their different crystal structures 15. Because of the ability of uranium to stabilise multi‐oxidation states (III, IV, V and VI) and because the intercalation of interstitial oxygen into the fluorite lattice of UO 2 is a spontaneous process,16 hyperstoichiometric UO 2+ x (0< x <0.25) is easily produced.…”

Mechanism of uranium (VI) removal by two anaerobic bacterial communities

“…The presence of U (IV) was also consistent with the black colour of the precipitate formed. Typically, U (VI) has an orange/yellow colour, while the precipitate of UO 2 shows a black/brown colour [27,28]. The presence of U (IV) in the precipitate, together with the fact that uranium (VI) was only removed from solution in the presence of live cells, suggests a mechanism of enzymatic reduction, where U (VI) is converted to insoluble U (IV).…”

A Macrocyclic Chelator That Selectively Binds Ln4+ over Ln3+ by a Factor of 1029

“…STXM methodology was similar to that discussed previously. [133][134][135][136] Single-energy images and Ce M5,4-edge XANES spectra were acquired using both the STXM instruments at the Canadian Light Source (CLS) spectromicroscopy beamline 10ID-1 and at the Advanced Light Source-Molecular Environmental Science (ALS-MES) beamline 11.0.2. The CLS operated in decay mode (250 to 150 mA) while the ALS operated in topoff mode (500 mA).…”