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- 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.
- ItemWork 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, MichaelTitanium 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.
- 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.
- ItemOne-dimensional oxide nanostructures: growth, applications and devices(Saarbrücke : Leibniz-Institut für Neue Materialien, 2008) Barth, Sven; Mathur, Sanjay; Hernandez-Ramireza, Francisco; Romano-Rodrigueza, AlbertOne dimensional (1D) inorganic materials are gaining high attention due to their structural stability and unique structural fatures. Among them, oxides are widely studied due to their well established application potential and mechanical as well as chemical stability. We have developed a generic approach for size-selective and site-specific growth of oxide nanowires by combination of a catalyst assisted growth mechanism and a molecular precursor approach, which is a viable alternative to other gas phase and solution procedures and produces well-defined (morphology and composition) materials.
- 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.
- ItemMorphology controlled preparation of monodisperse TiO2 nanorods and nanoparticles for optical nanocomposites(Saarbrücke : Leibniz-Institut für Neue Materialien, 2011) Bentz, Dirk; Becker-Willinger, Carsten; Schmitz-Stöwe, Sabine; Veith, MichaelAnatase nanoparticles and nanorods were obtained through a modified sol-gel route from titanium(IV) bis(acetylacetonate) diisopropoxide. For particle synthesis a mixture of oleic acid and oleyl amine has been used which offers not only control on particle morphology but also provides organically capped surface modified particles, which can be readily mixed with acrylic monomers yielding completely transparent dispersions. UV- and thermal curing of the monomer / particle mixture lead to clear coatings without any nanoparticle agglomeration.
- 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]
- 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.
- ItemKinetic investigations on TiO2 nanoparticles as photo initiators for UV-polymerization in acrylic matrices(Saarbrücke : Leibniz-Institut für Neue Materialien, 2010) Schmitz-Stöwe, Sabine; Becker-Willinger, Carsten; Bentz, Dirk; Abt, Britta; Veith, MichaelTiO2 nanoparticles of anatase, useful as photosensitive initiators to induce free radical polymerization in acrylic monomers have been prepared by chemical synthesis. Appropriate surface modification of TiO2 has been achieved in order to compatibilize the particles with the acrylic monomers to obtain an almost homogeneous distribution down to the primary particle size. The surface modification has been additionally fine tuned in such a way, that an efficient transfer of the electrons generated on TiO2 during UV-exposure could be achieved towards the monomer mixture in order to start the polymerization reaction. The formation of the anatase modification could be confirmed by XRD. Particle sizes were determined by UPA, which showed a distribution between 1-10 nm depending on the preparation method used. Transmission electron microscopy carried out with the UV-polymerized coating layers proved the homogeneous distribution of the anatase nanoparticles. Kinetic investigations on the photo-polymerization behavior have been accomplished by photo-DSC and Raman spectroscopy. Curing time was determined in dependence of the materials composition.
- 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]