X-ray single phase LSGM at 1350 °C

Synthesis of X-ray-phase-pure (La1−xSrxGa1−yMgyO3−δ, LSGM, where x = 0.1, y = 0.15 and 0.17) powders were achieved at temperatures as low as 1350 °C via organic precursor method using tartaric acid as the carrier material. LSGM materials were characterized for their phase purity, crystallization and electrical properties. Pellets sintered at 1350 °C for 6 h were single phase and dense (>99%). Electron microscopy analysis of X-ray single-phase pellets revealed MgO precipitates with sizes ranging from 50–300 nm. Phase formation and distribution in this complicated multi-cation-oxide system as a function of temperature were reported and discussed. Amorphous LSGM first crystallizes at 625 °C. However, elimination of undesired phases require higher temperatures. Impedance measurements as a function of temperature up to 545 °C revealed that the X-ray phase pure pellets may have extrapolated ionic conductivity values as high as 0.14–0.16 S/cm at 800 °C. Possible implications of limited MgO solubility on the ionic conductivity are presented

Molecular adsorption studies at heterogeneous oxide/electrolyte interface

Das Ziel dieser Arbeit ist es, die Adsorption von selbstorganisierenden Monolagen (SAMs) und Makromolekülen auf oxidischen Oberflächen mittels Rasterkraftmikroskop (AFM) basierter Methoden zu studieren. Der erste Teil der Arbeit beschäftigt sich mit den Wechselwirkungen zwischen Aminogruppen und Montmorillonitpartikeln. In dem zweiten Teil wurde der Zusammenhang zwischen pH-Wert und Abziehkraft mittels chemischer Kraft-Abstands-Spektroskopie (CFM) und Einzelmolekül-Kraftspektroskopie (SMFS) in Kombination mit ex situ spektroskopischer Verfahren analysiert. Neben den Transporteigenschaften der Beschichtung für korrosive Substanzen ist ebenfalls eine gute Haftung auf dem Metall bzw. Metalloxid von entscheidender Bedeutung für die Leistungsfähigkeit und Langlebigkeit der Schutzschicht. Zu diesem Zweck wurde in dem letzten Teil der Arbeit die Selbstorganisation von Molekülen auf einkristallinen Al2O3 Oberflächen mittels AFM basiertem Nanoshaving und Nanografting untersucht

Corrosion Mechanism of Microporous Nickel-Chromium Coatings: Part II. SECM Study Monitoring Cu²⁺and Oxygen Reduction

The corrosion mechanism of microporous nickel-chromium multilayer coatings was studied at localised scale by Scanning Electrochemical Microscopy (SECM) after exposure to an aggressive electrolyte (chloride-based one at pH 3.1 containing cupric ions). The open circuit potential was initially monitored during 22 h, followed by a detailed characterisation using Glow Discharge-Optical Emission Spectroscopy and Field Emission Scanning Electron Microscope. Interestingly, Cu deposition occurs over the surface of the microporous nickel layer, and it is located on spots where micro-discontinuities (i.e., cracks and pores) of the outermost Cr layer are present. The application of different operation modes of the SECM (i.e., redox competition and surface generation/tip collection) not only reveals such copper deposits (which were identified after monitoring their catalytic capabilities for oxygen reduction reaction) but also confirms the stepwise reduction of Cu2+ to Cu (via intermediate species of Cu+) during the corrosion process. The impact of metallic copper particles in the local pH due to their catalytic activity could also explain why the microporous nickel layer is not corroded after exposure to such electrolyte.Green Open Access added to TU Delft Institutional Repository 'You share, we take care!' - Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.Team Yaiza Gonzalez Garci

Exploring the effect of the pH on the corrosion of multilayer nickel-chromium coatings

The impact of the pH on the corrosion of microporous nickel-chromium coatings has been explored at localised scale by Scanning Electrochemical Microscopy and validated by potentiodynamic polarisation measurements. Results not only reveal the correlation between both techniques but also enables to identify the different corrosion rate after increasing the electrolyte aggressiveness varying the pH. However, independently of the pH, a similar corrosion mechanism was determined: the cross-section micrographs (by Field Emission-Scanning Electron Microscope) have revealed an isotropic growth of the actives sites at early-stage corrosion as well as the attack of different nickel layers during the corrosion propagation.Green Open Access added to TU Delft Institutional Repository 'You share, we take care!' - Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.Team Yaiza Gonzalez Garci