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Author: Veith, Michael × End date: 2009 × Start date: 2000 × DDC: 540 × Type: article ×

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    Corrosion inhibiting cerium compounds for chromium-free corrosion protective coatings on AA 2024
    (Saarbrücke : Leibniz-Institut für Neue Materialien, 2007) Schem, Michael; Schmidt, Thomas; Caparrotti, Hinka; Wittmar, Matthias; Veith, Michael
    Due to the upcoming ban of chromium-containing corrosion protection coatings in the near future, there is a worldwide effort to find a replacement for chromium as a corrosion inhibitor that also exhibits self-healing properties in scratches but without the negative efects like health and environmental hazards. In the present study promising results to achieve this goal are shown by using cerium compounds incorporated into an organic-inorganic hybrid material produced by the sol-gel process. Cerium compounds like cerium nitrate, cerium nitrate plus acetylacetonate, cerium acetylacetonate, and cerium sulphate were incorporated in sol-gel coating systems. The corrosion protection properties of these coatings were determined by means of Electrochemical Impedance Spectroscopy (EIS) and in a conventional salt spray test. Furthermore, the leaching behaviour of the coatings was examined via Optical Emission Spectrometry (OES). Significant hints for self healing properties were obtained with a hybrid system doped with cerium nitrate in combination with acetylacetone.
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    Mechanisms of bonding effected by nanoparticles in zirconia coatings applied by spraying of suspensions
    (Saarbrücke : Leibniz-Institut für Neue Materialien, 2008) Adam, Jens; Aslan, Mesut; Drumm, Robert; Veith, Michael
    Zirconia coatings consisting of a mixture of coarse and fine grained zirconia powders prepared by spraying of suspensions and subsequent thermal treatment at limited temperatures (up to 500°C) are poor in adherence and in intrinsic mechanical strength. We have shown elsewhere that mechanical properties of these coatings can be improved clearly by adding a small amount of nanoscaled zirconia. Here, the structural and the chemical development of this coating material and of the nanoparticles is examined to gain information about the underlying bonding mechanisms. The applied temperature is relatively low in comparison to the usual onset temperature of accelerated sintering. Nevertheless, the results show that diffusion controlled material transport mechanisms play their role in bonding. The condensation of surface OH groups may participate in bonding, too. These first results confirm the potential of nanoparticles to act as inorganic binder. Additional research effort to clarify the underlying mechanisms in detail is of interest. For the practical side, it can be concluded that the resulting effect of mechanical consolidation of ceramic structures at relatively low temperatures enables new ceramic applications, for example a new type of ceramic coatings on metallic substrates.
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    Microstructure investigation of reflective coatings interference multilayers produced by sol-gel method
    (Saarbrücke : Leibniz-Institut für Neue Materialien, 2007) Jilavi, Mohammad H.; Sam, Ebru D.; Werner, Ulf; Oliveira, Peter W. de; Veith, Michael
    [no abstract available]
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    Preparation of acoustic lenses by mechano-chemical synthesis and electrophoretic deposition of lead zirconium titanate (PZT) films
    (Saarbrücke : Leibniz-Institut für Neue Materialien, 2008) Bender, Michael; Drumm, Robert; Adam, Jens; Jakob, Annette; Lemor, Robert; Veith, Michael
    PZT powders has been synthesized via reactive dry milling using PbZrO3 and PbTiO3 as starting materials. Stabel suspensions of the PZT particles in ethanol (d50(Vol) = 115 nm) were obtained by a chemomechanical dispersion step. Teh electrophoretic deposition has been optimized varying the cell voltage and the PZT solid content in the suspension. PZT films have been deposited on platinum coated saphire. After drying, the films are densely packed and free of cracks. By using lithium acetate and lead acetate as a sinter aid it was possible to reduce the sintering temperature to 1050°C. A good electrode has been sputtered onto the piezoelectric films which then have been poled by the corona method. The circular PZT dots (...) with a thickness of 1 µm show the expected oscillation resonance at about 2 GHz and can be used in acoustic lenses, for example in acoustic microscopes.
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    Work on non photocatalytically active titania particles
    (Saarbrücke : Leibniz-Institut für Neue Materialien, 2009) Müller, Thomas S.; Faller-Schneider, Christine; Moh, Karsten; Shanmugasundaram, Sakthivel; Oliveira, Peter W. de; Veith, Michael
    Titanium dioxide has photocatalytic properties, i.e. under UV irradiation it develops an oxidative potential. In photocatalysis this is very desirable, but not when nano particulate titania is embedded into organic polymer matrices in order to increase the refractive index. UV irradiation would in this case destroy the material in the long run. For deactivation in general the titania is coated by e.g. silica or alumina which leads to other undesired effects like growth of the particle size and enhanced light scattering. The current work focuses on the application of techniques for doping during synthesis of crystallization of nano particulate TiO2. The photocatalysis activity was determined by degradation experiments of 4-chlorophenol using dip coated glass plates under artificial sunlight, where decreases of the photocatalytic effect of up to 90 % were found.