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| 2. |
- Butorin, Sergei M., et al.
(författare)
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Chemical Reduction of Actinides Probed by Resonant Inelastic X-ray Scattering
- 2013
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Ingår i: Analytical Chemistry. - : American Chemical Society (ACS). - 0003-2700 .- 1520-6882. ; 85:23, s. 11196-11200
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Tidskriftsartikel (refereegranskat)abstract
- The study addresses the possibilities of immobilizing the mobile species of actinides in the geosphere using metallic iron. Sorption on corroding iron is well-known, but there have been uncertainties with regard to the possibilities of reducing the actinyl species to sparingly soluble oxides and, thereby, permanently immobilizing them. Resonant inelastic X-ray scattering (RIXS) measurements at the actinide 5d edges on Fe foils exposed to uranium(VI) and neptunium(V) solutions in groundwater unambigiously indicate reduction of actinides to, respectively, uranium(IV) and neptunium(IV) on iron surfaces. The reduction manifests itself in an appearance of distinct specific signatures of uranium(IV) and neptunium(IV) in the RIXS profile of 5f-5f excitations. Such signatures and RIXS intensity/cross-section behavior with varying energy of incident photons can be reproduced by model atomic-multiplet calculations of the RIXS spectra. By normalizing the RIXS signal of corresponding 5f-5f excitations to core-to-core 6p-to-5d characteristic fluorescence transitions of actinides, their reduction rates on Fe samples with different exposure to actinide solutions can be estimated. Observed reduction implies similar processes in the nuclear waste canister thus suggesting reduced probability of nuclear waste release with ground waters from the canister.
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| 3. |
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| 4. |
- Hollmark, Håkan, et al.
(författare)
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Exposure of Oxidized Copper Surfaces to Aqueous Na2S Solution Studied with Soft X-Ray Spectroscopy
- 2011
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Ingår i: Journal of the Electrochemical Society. - : The Electrochemical Society. - 0013-4651 .- 1945-7111. ; 158:1, s. C1-C5
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Tidskriftsartikel (refereegranskat)abstract
- We present results from X-ray absorption spectroscopy (XAS) and resonant inelastic X-ray scattering (RIXS) of oxidized polycrystalline copper surfaces [Cu(I) and Cu(II), respectively] exposed to a 1.0 mM aqueous solution of Na2S (sodium sulfide) for several hours. Scanning electron microscopy reveals that the Cu oxide surfaces attain a much rougher texture upon sodium sulfide exposure, and that the exposed Cu(II) oxide sample exhibits areas with crystallites. The XAS spectra show that sodium sulfide effectively reduces Cu(II) oxide to Cu(I) compounds. The RIXS spectra of the exposed surfaces closely resemble those of the Cu2O reference sample with the notable exception of their Cu LIII,II-RIXS spectra. We conclude that copper evidently forms a Cu(I) compound with oxygen but with a Cu 3d-band of much reduced width, pointing to the possibility of a more complex compound containing both oxygen and sulfur.
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| 5. |
- Hollmark, Håkan, et al.
(författare)
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X-ray absorption spectroscopy on electrochemically oxidized Cu exposed to Na2S
- 2011
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Ingår i: Corrosion Science. - Amsterdam : Elsevier. - 0010-938X .- 1879-0496. ; 54, s. 85-89
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Tidskriftsartikel (refereegranskat)abstract
- Copper surfaces have been investigated by X-ray absorption spectroscopy after electrochemical oxidation and subsequent exposure to sulfide solution. Oxide surface layers on bulk copper surfaces were electrochemically grown in anaqueous NaOH solution at two different potentials and the resulting chemical composition was investigated using X-ray absorption spectroscopy. At both potentials the resulting surfaces consisted largely of Cu2O. At the more strongly oxidizing potential, an admixture of Cu2+-containing phases – mostly Cu(OH)2 – was detected. Sulfide exposure of both surfaces was found to completely reduce the surface from Cu2+ to Cu1+ and resulted in the formation of Cu2S with an admixture of Cu2O.
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| 6. |
- Kvashnina, Kristina, et al.
(författare)
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Changes in electronic structure of copper films in aqueous solutions
- 2007
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Ingår i: Journal of Physics. - : IOP Publishing. - 0953-8984 .- 1361-648X. ; 19:22, s. 226002-
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Tidskriftsartikel (refereegranskat)abstract
- The possibilities for using x-ray absorption spectroscopy (XAS) and resonant inelastic x-ray scattering (RIXS) to probe the Cu oxidation state and changes in the electronic structure during interaction between copper and ground-water solutions were examined. Surface modifications induced by chemical reactions of oxidized 100 Å Cu films with Cl−, SO42− and HCO3− ions in aqueous solutions with various concentrations were studied in situ using liquid cells. Copper corrosion processes in ground water were monitored for up to nine days. By comparing Cu 2p–3d, 4s transitions for a number of reference substances previously measured, changes in electronic structure of the Cu films were analysed. The XAS and RIXS spectral shape at the Cu edge, the chemical shift of the main line for Cu2+, and the energy positions of the observed satellites served as a tool for monitoring the changes during the reaction. It was found that the pH value and the Cl− concentration in solutions strongly affect the speed of the corrosion reaction.
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| 7. |
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| 8. |
- Kvashnina, Kristina O., et al.
(författare)
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In situ X-ray absorption study of copper films in ground water solutions
- 2007
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Ingår i: Chemical Physics Letters. - : Elsevier BV. - 0009-2614 .- 1873-4448. ; 447:1-3, s. 54-57
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Tidskriftsartikel (refereegranskat)abstract
- This study illustrates how the damage from copper corrosion can be reduced by modifying the chemistry of the copper surface environment. The surface modification of oxidized copper films induced by chemical reaction with Cl− and in aqueous solutions was monitored by in situ X-ray absorption spectroscopy. The results show that corrosion of copper can be significantly reduced by adding even a small amount of sodium bicarbonate. The studied copper films corroded quickly in chloride solutions, whereas the same solution containing 1.1 mM prevented or slowed down the corrosion processes.
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| 9. |
- Kvashnina, Kristina, et al.
(författare)
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Resonant inelastic x-ray scattering of curium oxide
- 2007
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Ingår i: Physical Review B. Condensed Matter and Materials Physics. - 1098-0121 .- 1550-235X. ; 75:11, s. 115107-
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Tidskriftsartikel (refereegranskat)abstract
- The measurements on radioactive actinide isotopes (curium-248) were performed using very small sample quantities (micrograms) to minimize the sample activity. Resonant inelastic x-ray scattering (RIXS) spectra of curium oxide at the Cm 5d edge were measured for the first time. RIXS data are compared with theoretical calculations using atomic multiplet theory. The results indicate that isotope curium -248 in the curium oxide sample has oxidation state III due to the best agreement with RIXS calculations for Cm (III) instead of those for Cm (IV).
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