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    Entwicklung eines kratzfesten, transparenten Pulverlackes
    (Saarbrücken : Universität des Saarlandes, 2014) Jochum, Marlon
    Im Rahmen der Arbeit wurde versucht einen transparenten, kratzfesten Pulverlack herzustellen. Es wurden kommerziell erhältliche Böhmitnanopartikel auf ihre Eignung als Kompositbestandteil untersucht und mit einem zweikomponentigen Poly\-ur\-ethan\-ma\-trix\-sy\-stem als Pulverlackbinder kombiniert. Zur Herstellung eines Komposites wurden die Bestandteile in einem Heissextrusionsverfahren ineinander dispergiert. Es wurden sowohl modifizierte als auch unmodifizierte Böhmitpartikel zur Kompositherstellung verwendet. Eine Art Böhmitpartikel wurde mit einem Isocyanatosilan modifiziert und ebenfalls Komposite hergestellt. Die Böhmitpartikel wirkten sich positiv auf die Stabilität der Bindermatrix aus, allerdings ohne die Kratzfestigkeit merklich zu erhöhen. Aus den mit Isocyanatosilan modifizierten Böhmitpartikeln wurden Komposite mit wechselndem Komponentenverhältnis hergestellt. Dabei wurde festgestellt, daß die modifizierten Partikel mit der Matrix eine leichte Bindung eingehen und diese verfestigen.
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    Crystallization of nanoscaled colloids
    (Saarbrücken : Saarländische Universitäts- und Landesbibliothek, 2012) Born, Philip
    Colloidal crystals can exhibit novel properties arising from the combination of particle properties and collective phenomena of particle packings. Particular colloidal crystals composed of nanoparticles are interesting, because of the unique properties of nanoscale objects, and because of the formation of three-dimensional structures on scales that can be manufactured using established methods only with great technical effort. The aim of this work was to develop appropriate ways to produce the crystals. Two approaches were chosen. In the first approach, colloid particles were deposited on surfaces in a process similar to dip coating. Large-area crystalline particle films with low defect density were obtained by an optimized deposition geometry. In the second approach attractive interactions between particles were used. Reducing the thermal energy induced agglomeration of the particles. This approach allowed production of a variety of particle structures. Besides the expected result, formation of hexagonal particle packings, unexpected results were obtained. In the first approach a superposition of two crystallization mechanisms ensured a robust formation of hexagonal particle packings. In the second approach crystallization among the particles was suppressed in a pure thermally induced agglomeration.
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    Synthesis of biphasic Al/Al2O3 nanostructures under microgravity and laser structuring on Al/Al2O3 surfaces for selective cell guidance
    (Saarbrücken : Universität des Saarlandes, 2013) Lee, Juseok
    The first part of this thesis is dealing with gravity effect on the synthesis of biphasic core/shell Al/Al2O3 composites. By chemical vapor deposition of the precursor [tBuOAlH2]2 at 400°C, only spherical nanoparticles were observed on the substrate surface. The formation of nanowires was observed at 600°C. It is a good agreement with our previous results on earth condition and there is no gravity impact on the chemical reaction. At increased gravity levels, the nanoparticles formed large clusters and the nanowires showed bundle formation while the nanowires at microgravity have predominantly linear structures. It is proposed that the chaotic nature of nanowires and cluster formation of nanoparticles were caused by a dominance of gravity over the thermal creep. In the second part the use of Al/Al2O3 nanowire layers for bio applications is considered. Contact cell guidance and alignment were studied to understand how cells recognize and respond to certain surface patterns. Linear micro channels were created on Al/Al2O3 layer by direct laser writing and laser interference patterning. Although surface topography was altered, the surface chemistry was always identical (Al2O3) due to the unique core/shell nature of Al/Al2O3 nanowires. Human osteoblast, normal human dermal fibroblast and neuronal cells were cultured and investigated. The results indicate that different cell types show diverse responses to the topography independent from the surface chemistry of the material.