CeOx/Al2O3 thin films on stainless steel substrate - Dynamical X-ray photoelectron spectroscopy investigations

Cataloged from PDF version of article.The CeOx/Al2O3 thin films on stainless steel with different ceria loading were subjected to a. c. ( square wave) pulses at various frequencies in the range 10(-3) to 100 kHz while recording X-ray photoelectron spectra. The resulting binding energy differences were derived from the frequency dependence of the corresponding Al2p, Ce3d and O1s peaks. At low ceria loadings the main constituent on the surface is CeAlO3 phase, while for high ceria loading the film is constructed from CeO2 and CeAlO3 phases spread over the Al2O3. Accordingly, it was observed that the ceria loading determines the conductivities of the investigated thin oxide films. (C) 2013 Elsevier B.V. All rights reserved

CeOx/Al2O3 thin films on stainless steel substrate - Dynamical X-ray photoelectron spectroscopy investigations

The CeOx/Al2O3 thin films on stainless steel with different ceria loading were subjected to a.c. (square wave) pulses at various frequencies in the range 10- 3 to 100 kHz while recording X-ray photoelectron spectra. The resulting binding energy differences were derived from the frequency dependence of the corresponding Al2p, Ce3d and O1s peaks. At low ceria loadings the main constituent on the surface is CeAlO 3 phase, while for high ceria loading the film is constructed from CeO2 and CeAlO3 phases spread over the Al 2O3. Accordingly, it was observed that the ceria loading determines the conductivities of the investigated thin oxide films. © 2013 Elsevier B.V. All Rights Reserved

Corrosion stability of stainless steel, modified electrochemically with Ce 2 O 3 -CeO 2 films, in 3.5% NaCl media

This work is focused on the study of corrosion-protection ability of the thin ceria film, formed electrochemically on OC404 stainless steel (SS) in non-aqueous electrolytes. The influence of changes in the surface concentration of Ce 2 O 3 -CeO 2 on the corrosion behaviour of OC404 stainless steel in 3.5% NaCl was investigated prior to the thermal treatment as well as after it. A shift of corrosion potential in positive direction was found via polarization curve recording, as well as via decrease in the corrosion current, respectively decrease in the corrosion rate (enhancement of the corrosion protection) in the presence of ceria oxide films. The data, acquired by AFM and XPS, are in a good agreement with these results. On the basis of the obtained results we can conclude that the presence of Ce 2 O 3 -CeO 2 film results in passivation and re-passivation of the steel surface and a slowdown in the pitting corrosion in an aggressive media. These conclusions are explained by the strong polarization influence of the Ce 2 O 3 -CeO 2 layers on the conjugated depolarization cathodic reaction of reduction of the dissolved oxygen

Investigation of the Stationary and Transient A1·− Radical in Trp → Phe Mutants of Photosystem I

Photosystem I (PS I) contains two symmetric branches of electron transfer cofactors. In both the A- and B-branches, the phylloquinone in the A1 site is π-stacked with a tryptophan residue and is H-bonded to the backbone nitrogen of a leucine residue. In this work, we use optical and electron paramagnetic resonance (EPR) spectroscopies to investigate cyanobacterial PS I complexes, where these tryptophan residues are changed to phenylalanine. The time-resolved optical data show that backward electron transfer from the terminal electron acceptors to P700·+ is affected in the A- and B-branch mutants, both at ambient and cryogenic temperatures. These results suggest that the quinones in both branches take part in electron transport at all temperatures. The electron-nuclear double resonance (ENDOR) spectra of the spin-correlated radical pair P700·+A1·− and the photoaccumulated radical anion A1·−, recorded at cryogenic temperature, allowed the identification of characteristic resonances belonging to protons of the methyl group, some of the ring protons and the proton hydrogen-bonded to phylloquinone in the wild type and both mutants. Significant changes in PS I isolated from the A-branch mutant are detected, while PS I isolated from the B-branch mutant shows the spectral characteristics of wild-type PS I. A possible short-lived B-branch radical pair cannot be detected by EPR due to the available time resolution; therefore, only the A-branch quinone is observed under conditions typically employed for EPR and ENDOR spectroscopies