Electrochemical texturing of Al-doped ZnO thin films for photovoltaic applications

The processes during chemical and electrochemical etching of Al-doped ZnO are investigated utilizing a scanning flow cell setup with online detection of dissolved Zn ions. The rate of chemical dissolution was found to be a linear function of buffer and proton concentration in near neutral pH solutions according to a transport limited reaction. In contrast, electrochemical etching is limited by the kinetics of the reaction and increases linearly with the imposed current density. Due to this fundamental difference, the dissolution of Zn can be either uniform over the whole surface or highly localized at active sites like grain boundaries. A combined approach of chemical etching and the well-controllable galvanostatic dissolution thus allows a fine adjustment of the ZnO:Al surface texture for applications in silicon thin film photovoltaic cells in order to improve their overall energy conversion efficiency.     

Frequent hypercyclicity,chaos, and unconditional Schauder decompositions

We prove that if X is any complex separable infinite-dimensional Banach space with an unconditional Schauder decomposition, X supports an operator T which is chaotic and frequently hypercyclic. In contrast with the complex case, we observe that there are real Banach spaces with an unconditional basis which support no chaotic operator.     

An Exact Navier-Stokes Solution for Three-Dimensional,Spanwise-Homogeneous Boundary Layers

The plane stagnation flow onto (Hiemenz boundary layer, HBL) and the asymptotic suction boundary layer flow over a flat wall (ASBL) are two boundary layer flows for which the incompressible Navier-Stokes equations are amenable to exact similarity solutions. The Hiemenz solution has been extended to swept Hiemenz flows by superposition of a third, spanwise-homogeneous sweep velocity. This solution becomes singular as the chordwise, tangential base flow component vanishes. In this limit, the homogeneous ASBL solution is valid, which however cannot describe the swept Hiemenz flow, because it does not contain any chordwise velocity. This work presents a generalized three-dimensional similarity solution which describes three-dimensional spanwise homogeneously impinging boundary layers at arbitrary wall-normal suction velocities, using a rescaled similarity coordinate. The HBL and the ASBL are shown to be two limits of this solution. Further extensions consist of oblique impingement or different boundary suction directions, such as slip or stretching walls. (© 2012 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)     

Zur Bestimmung des Chroms im Chromeisenstein

Ohne Zusammenfassung     

Bemerkungen über österreichisch-ungarische Süssweine

Analytical and Bioanalytical Chemistry -     

The Common Intermediates of Oxygen Evolution and Dissolution Reactions during Water Electrolysis on Iridium

Understanding the pathways of catalyst degradation during the oxygen evolution reaction is a cornerstone in the development of efficient and stable electrolyzers, since even for the most promising Ir based anodes the harsh reaction conditions are detrimental. The dissolution mechanism is complex and the correlation to the oxygen evolution reaction itself is still poorly understood. Here, by coupling a scanning flow cell with inductively coupled plasma and online electrochemical mass spectrometers, we monitor the oxygen evolution and degradation products of Ir and Ir oxides in situ. It is shown that at high anodic potentials several dissolution routes become possible, including formation of gaseous IrO₃. On the basis of experimental data, possible pathways are proposed for the oxygen‐evolution‐triggered dissolution of Ir and the role of common intermediates for these reactions is discussed.     

Pyridazin-3-carbaldehyd: Synthese und Reaktivitätsstudien

by MnO₂-oxidation of 3-pyridazinemethanol is reported. Properties of2 and its reactions with NH-compounds and methyl-pyridazines (3, 5) are studied. Reaction of2 with3 yields mainly products of aldol addition (10, 12). In contrast to pyridazinyl-4-carbinols elimination of H₂O from10 leads to the alkene11. Isolation of the di-pyridazinyl-ethane6 as main product of reaction of2 with5 however shows, that thermally induced dismutation cannot be excluded also on pyridazinyl-3-carbinols.

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Herrn Prof. Dr.F. Vieböck mit den besten Wünschen zum 75. Geburtstag gewidmet.