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Vegelius, Johan
Publications (3 of 3) Show all publications
Butorin, S. M. M., Modin, A., Vegelius, J., Kvashnina, K. O. & Shuh, D. K. (2016). Probing Chemical Bonding in Uranium Dioxide by Means of High- Resolution X-ray Absorption Spectroscopy. The Journal of Physical Chemistry C, 120(51), 29397-29404
Open this publication in new window or tab >>Probing Chemical Bonding in Uranium Dioxide by Means of High- Resolution X-ray Absorption Spectroscopy
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2016 (English)In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 120, no 51, p. 29397-29404Article in journal (Refereed) Published
Abstract [en]

A systematic X-ray absorption study at the U 3d, 4d, and 4f edges of UO2 was performed, and the data were analyzed within framework of the Anderson impurity model. By applying the high-energy-resolution fluorescence-detection (HERFD) mode of X-ray absorption spectroscopy (XAS) at the U 3d(3/2) edge and conducting the XAS measurements at the shallower U 4f levels, fine details of the XAS spectra were resolved resulting from reduced core-hole lifetime broadening. This multiedge study enabled a far more effective analysis of the electronic structure at the U sites and characterization of the chemical bonding and degree of the 5f localization in UO2. The results support the covalent character of UO2 and do not agree with the suggestions of rather ionic bonding in this compound as expressed in some publications.

National Category
Atom and Molecular Physics and Optics
Identifiers
urn:nbn:se:uu:diva-315073 (URN)10.1021/acs.jpcc.6b09335 (DOI)000391160400052 ()
Available from: 2017-02-10 Created: 2017-02-10 Last updated: 2017-11-29Bibliographically approved
Hollmark, H., Keech, P., Vegelius, J., Werme, L. & Duda, L. (2011). X-ray absorption spectroscopy on electrochemically oxidized Cu exposed to Na2S. Corrosion Science, 54, 85-89
Open this publication in new window or tab >>X-ray absorption spectroscopy on electrochemically oxidized Cu exposed to Na2S
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2011 (English)In: Corrosion Science, ISSN 0010-938X, E-ISSN 1879-0496, Vol. 54, p. 85-89Article in journal (Refereed) Published
Abstract [en]

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.

Place, publisher, year, edition, pages
Amsterdam: Elsevier, 2011
Keywords
Copper, AFS (EXAFS & XANES), Sulphidation
National Category
Atom and Molecular Physics and Optics
Research subject
Physics with spec. in Atomic, Molecular and Condensed Matter Physics
Identifiers
urn:nbn:se:uu:diva-149328 (URN)10.1016/j.corsci.2011.09.001 (DOI)000297894000012 ()
Available from: 2011-03-17 Created: 2011-03-17 Last updated: 2017-12-11Bibliographically approved
Vegelius, J. (2011). X-ray Spectroscopic Studies of Materials for Nuclear Technology. (Doctoral dissertation). Uppsala: Acta Universitatis Upsaliensis
Open this publication in new window or tab >>X-ray Spectroscopic Studies of Materials for Nuclear Technology
2011 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

X-ray spectroscopic experiments, including X-ray absorption spectroscopy (XAS), X-ray emission spectroscopy (XES) and resonant inelastic X-ray scattering (RIXS), were performed in a large energy range (60-9000 eV) on a variety of systems, probing different elements and orbitals. The systems can preferably be divided into three groups: Actinides, copper systems and amorphous materials. We studied oxidation states of Pu in PuO2 using a closed-source experimental setup, developed by us, to lower the safety restrictions associated with such experiments. The presence of Pu with higher oxidation state than Pu(IV) was found in polycrystalline PuO2. This is an important finding since Pu with higher oxidation states has higher solubility affecting the safety of a proposed undeground repository of spent nuclear fuel which can eventually be infiltrated by groundwater. In the proposed underground repository the molecular oxygen will vanish at some point due to microbial activity and mineral oxidation. At this stage sulfur is the most important candidate for causing copper corrosion. We studied Cu films and foils exposed to sulfide solutions at both Cu L2,3, Cu K and S L2,3 edges and found for example that S L2,3 XES is useful for distinguishing between different copper sulfides and Cu Kβ XES can be used to identify monovalent Cu compounds. Amorphous, zirconium containing alloys are potentially useful materials for future nuclear reactors. The electronic structure of such materials was also investigated.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2011. p. 56
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 874
Keywords
XAS, XES, RIXS, amorphous, DOS, spectroscopy, actinides, copper, uranium, plutonium
National Category
Atom and Molecular Physics and Optics
Identifiers
urn:nbn:se:uu:diva-160362 (URN)978-91-554-8205-3 (ISBN)
Public defence
2011-12-09, Polhemsalen, Ångströmlaboratoriet, Lägerhyddsvägen 1, Uppsala, 10:15 (English)
Opponent
Supervisors
Available from: 2011-11-17 Created: 2011-10-21 Last updated: 2011-11-17Bibliographically approved
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