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- Delheusy, M., et al.
(författare)
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X-ray investigation of subsurface interstitial oxygen at Nb/oxide interfaces
- 2008
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Ingår i: Applied Physics Letters. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 92:10
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Tidskriftsartikel (refereegranskat)abstract
- We have investigated the dissolution of a natural oxide layer on a Nb(110) surface upon heating, combining x-ray reflectivity, grazing incidence diffuse scattering, and core-level spectroscopy. The natural oxide reduces after heating to 145 degrees C partially from Nb2O5 to NbO2, and an enrichment in subsurface interstitial oxygen by similar to 70% in a depth of 100 A is observed. After heating to 300 degrees C, the oxide reduces to NbO and the surplus subsurface oxygen gets dissolved into the bulk. Our approach can be applied for further investigation of the effect of subsurface interstitial oxygen on the performance of niobium rf cavities. (C) 2008 American Institute of Physics. (C) 2008 American Institute of Physics.
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- Långberg, Marie, et al.
(författare)
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Characterization of Native Oxide and Passive Film on Austenite/Ferrite Phases of Duplex Stainless Steel Using Synchrotron HAXPEEM
- 2019
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Ingår i: Journal of the Electrochemical Society. - : Electrochemical Society. - 0013-4651 .- 1945-7111. ; 166:11, s. C3336-C3340
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Tidskriftsartikel (refereegranskat)abstract
- A new measurement protocol was used for microscopic chemical analysis of surface oxide films with lateral resolution of 1 mu m. The native air-formed oxide and an anodic passive film on austenite and ferrite phases of a 25Cr-7Ni super duplex stainless steel were investigated using synchrotron hard X-ray photoemission electron microscopy (HAXPEEM). Pre-deposited Pt-markers, in combination with electron backscattering diffraction mapping (EBSD), allowed analysis of the native oxide on individual grains of the two phases and the passive film formed on the same area after electrochemical polarization of the sample. The results showed a certain difference in the composition of the surface films between the two phases. For the grains with (001) crystallographic face // sample surface, the native oxide film on the ferrite contained more Cr oxide than the austenite. Anodic polarization up to 1000 mV/(Ag/AgCl) in 1M NaCl solution at room temperature resulted in a growth of the Cr- and Fe-oxides, diminish of Cr-hydroxide, and an increased proportion of Fe3+ species. by ECS. This is an open access article distributed under the terms of the Creative Commons Attribution 4.0 License (CC BY, http://creativecommons.org/licenses/by/4.0/), which permits unrestricted reuse of the work in any medium, provided the original work is properly cited.
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- Långberg, Marie, 1988-, et al.
(författare)
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Lateral variation of the native passive film on super duplex stainless steel resolved by synchrotron hard X-ray photoelectron emission microscopy
- 2020
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Ingår i: Corrosion Science. - Stockholm, : Elsevier BV. - 0010-938X .- 1879-0496. ; 174
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Tidskriftsartikel (refereegranskat)abstract
- A native passive film on 25Cr-7Ni super duplex stainless steel was analyzed using synchrotron hard X-ray photoemission electron microscopy, focusing on variations between individual grains of ferrite and austenite phases. The film consists of an oxide inner layer and an oxyhydroxide outer layer, in total 2.3 nm thick. The Cr content is higher in the outer than the inner layer, ca. 80 % on average. The Cr content is higher on ferrite than austenite, whereas the thickness is rather uniform. The grain orientation has a small but detectable influence, ferrite (111) grains have a lower Cr content than other ferrite grains.
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- Schmid, M, et al.
(författare)
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Structure of Ag(111)-p(4x4)-O: No silver oxide
- 2006
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Ingår i: Physical Review Letters. - 1079-7114. ; 96:14
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Tidskriftsartikel (refereegranskat)abstract
- The structure of the oxygen-induced p(4x4) reconstruction of Ag(111) is determined by a combination of scanning tunneling microscopy, surface x-ray diffraction, core level spectroscopy, and density functional theory. We demonstrate that all previous models of this surface structure are incorrect and propose a new model which is able to explain all our experimental findings but has no resemblance to bulk silver oxide. We also shed some light on the limitations of current density functional theories and the potential role of van der Waals interactions in the stabilization of oxygen-induced surface reconstructions of noble metals.
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- Stierle, A., et al.
(författare)
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Real time observation of ultrathin epitaxial oxide growth during alloy oxidation
- 2007
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Ingår i: New Journal of Physics. - : IOP Publishing. - 1367-2630. ; 9, s. 331-331
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Tidskriftsartikel (refereegranskat)abstract
- We have studied the thermal oxidation of the intermetallic alloy CoGa in situ, in real time on the atomic scale, during the growth of an ultrathin, epitaxial Ga oxide layer. On the basis of an extended set of surface x-ray diffraction data, density functional theory calculations and core level spectroscopy data, we find that the oxide film consists of an oxygen ion double layer, which contains the basic building block of bulk beta- Ga2O3. The oxide formation takes place via the nucleation of two- dimensional, anisotropic oxide islands which laterally grow and coalesce. A dramatic increase of the oxide island size is observed for low O-2 pressures in the 10(-8) mbar regime, which we interpret as the onset of a step flow like growth mode. This allows us to conclude that thermal oxidation can be considered as a hetero- epitaxial growth process, that follows similar atomistic growth principles to molecular beam epitaxy. As a consequence, the structural perfection of the oxide layer can be tailored by the appropriate choice of oxygen pressure and temperature.
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- Gleißner, Robert, et al.
(författare)
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Role of Oxidation–Reduction Dynamics in the Application of Cu/ZnO-Based Catalysts
- 2023
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Ingår i: ACS Applied Nano Materials. - 2574-0970. ; 6:9, s. 8004-8016
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Tidskriftsartikel (refereegranskat)abstract
- We investigated Cu nanoparticles (NPs) on vicinal and basal ZnO supports to obtain an atomistic picture of the catalyst’s structure under in situ oxidizing and reducing conditions. The Cu/ZnO model catalysts were investigated at elevated gas pressures by high energy grazing incidence X-ray diffraction and ambient pressure X-ray photoelectron spectroscopy (AP-XPS). We find that the Cu nanoparticles are fully oxidized to Cu2O under atmospheric conditions at room temperature. As the nanoparticles swell during oxidation, they maintain their epitaxy on basal ZnO (000 ± 1) surfaces, whereas on the vicinal ZnO (101̅4) surface, the nanoparticles undergo a coherent tilt. We find that the oxidation process is fully reversible under H2 flow at 500 K, resulting in predominantly well-aligned nanoparticles on the basal surfaces, whereas the orientation of Cu NPs on vicinal ZnO was only partially restored. The analysis of the substrate crystal truncation rods evidences the stability of basal ZnO surfaces under all gas conditions. No Cu–Zn bulk alloy formation is observed. Under CO2 flow, no diffraction signal from the nanoparticles is detected, pointing to their completely disordered state. The AP-XPS results are in line with the formation of CuO. Scanning electron microscopy images show that massive mass transport has set in, leading to the formation of larger agglomerates.
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