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- ItemCorrosion 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, MichaelDue 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.
- ItemResearch on the synthesis and applicability of surface modified nanoscaled metal oxide particles as curing catalyseres for UV-print-colours and lacquers(Saarbrücke : Leibniz-Institut für Neue Materialien, 2009) Becker-Willinger, Carsten; Schmitz-Stöwe, Sabine; Bentz, DirkIn the BMBF joint research project - NANOCURE - New Curing Methods for Print-Colours, Glues and Lacquers (prom. ref. : 13N9115) - a new class of nanoscaled photo initiators for radical polymerization processes in the printing industry is to be investigated. A possible mechanism for the reaction of TiO2 with acrylates, which is already described in literature is presented. Different methods of manufacturing TiO2 nanoparticles in the lower nanometric size range and their subsequent processing are described, the method is of special interest as it may lead to a possible integrated production process of UV-printing inks. The TEM analysis shows the homogeneous arrangement of TiO2 nanoparticles in an acrylic matrix, which is a necessary requirement for successful polymerization process. IR-spectroscopy is used to show the effect of TiO2-nanoparticles as UV photocatalytic polymerization initiators.
- ItemPlasma-assisted modulation of morphology and composition in Tin oxide nanostructures for sensing applications(Saarbrücke : Leibniz-Institut für Neue Materialien, 2007) Mathur, Sanjay; Ganesan, Rajesh; Ruegamer, Thomas; Shen, Hao; Barth, Sven[no abstract available]
- ItemNuevo sistema integrado cromatografía líquida de alta resolución / nebulizador hidráulico de alta presión y temperatura (HPLC/HT-HHPN) para la separación automática de la matriz en la determinación de metales en salmueras con espectrometría de absorción atómica (FAAS)(Sao Paulo : Scielo, 2000) Yáñez, J.; Berndt, H.An integrated HPF-system using HPLC and HT-HHP-nebulizer is used for matrix separation by the determination of heavy metals in highly concentrated solutions with FAAS. The separation of the matrix (NaCl) is achieved in a HPLC RP-C18 column after heavy metal complexing with trans-1,2-diaminciclohexane-N,N,N ,N -tetraacetic acid (CDTA). Matrix separation and the metal determination can be realized in less than one minute, without any interference from the matrix. The detection limits of Cd(II), Co(II), Cr(VI), Cu(II), Mn(II) and Zn(II) by FAAS were improved in one order of magnitude in compare with the direct determination by pneumatic nebulization nebulizer.
- ItemMechanisms 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, MichaelZirconia 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.
- ItemMicrostructure 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]
- ItemPreparation 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, MichaelPZT 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.
- ItemInvestigation on thermal and chemical stability of polymer based easy-to-clean nanocomposite systems(Saarbrücke : Leibniz-Institut für Neue Materialien, 2007) Gerdes, Ralf; Kalmes, Pamela; Becker-Willinger, CarstenAnti-adhesive coatings are of significant importance for many industrial processes such as pigment and paint production as well as also food processing industry, because they can help to significantly reduce the cleaning effort. For this reason, the amount of cleaning chemicals and waste water can be reduced, which should have a remarkable effect on the process costs. In this investigation abrasion resistant low surface free energy coatings based on fluoroalkyl group and SiC particles containing polyimides have been synthesised which show surface properties comparable to PTFE and can be coated like a paint on surfaces. Expecially in food production processes a high chemical stability is required for coating materials to withstand the cleaning procedures which are used in order to maintain the hygienic situation in the production facilities. The investigations revealed a high abrasion resistance (weight loss approx. 12 mg after 1000 cycles taber abrader test) and a moderate chemical stability of the coating systems. A chemical attack by sodium hydroxide solution as well as by oxidising substances such as nitric acid (HNO3) at elevated temperatures (90°C) led to a fast destruction of the coating performance caused by damage of the organic matrix. Also the exposure with carrot juice and mik at 90°C showed some influence. The contact angles against water decreased by about 20-30% whereas the oleophobic properties remained almost unchanged. On the other hand the polyimide nanocomposites showed a low surface roughness (Ra <= 0.2µm) and adjustable antistatic properties, what enables to use them in dry food processing (e.g. in flour mills). By using a nanocomposite system filled with 10 wt.-% carbon black FW 200 a resistivity of 1.5x103 Ω and a charge decay time of 0 s were obtained.
- ItemA contribution to climate protection - Electrochromic windows fabricated with the sol-gel technology(Saarbrücke : Leibniz-Institut für Neue Materialien, 2007) Heusing, Sabine[no abstract available]
- ItemFunctional surfaces for controlled adhesion(Saarbrücke : Leibniz-Institut für Neue Materialien, 2009) Arzt, Eduard; Del Campo, AranzazuAdhesive joining with molecular (van der Waals) interactions without chemical glue is presently receiving much attention because of many potential applications. Research on how insects, spiders and geckos stick to surfaces has inspired a new paradigm: fibrillar surfaces with appropriate design can show much higher adhesion performance than flat surfaces. The insight gained in studying biological systems can be transferred to the development of optimized artificial attachment devices. By systematic variations of fiber diameter, aspect ratio and contact shape, we have produced, on a laboratory scale, artificial structures with adhesion strengths similar to the gecko. Further advances with switchable adhesion ("smart adhesives") have been demonstrated and may lead to interesting applications in medical products, sports equipment, construction materials and microfabrication.