<> "The repository administrator has not yet configured an RDF license."^^ . <> . . "Sintering properties of platinum nanoparticles on different oxide-based substrates"^^ . "Metal nanoparticles play a significant role in exhaust combustion. They oxidize harmful products\r\nlike carbon monoxide and hydrocarbons in order to prevent major environmental and health\r\nissues. In a converter, platinum nanoparticles (Pt NPs) are impregnated in a thin coating of a\r\nporous ceramic oxide. Due to their high surface-to-volume ratio, Pt NPs can provide high catalytic\r\nactivities; however, elevated temperatures in the exhaust gas flow lead to thermal deactivation of\r\nthe catalyst via sintering, thereby resulting in large losses in efficiency over the catalyst’s lifetime.\r\nIn this thesis, the sintering behavior of 5-6 nm sized Pt NPs synthesized via block copolymer\r\nmicellar nanolithography on various planar oxide-based substrates is investigated. First, their\r\ncoarsening on both crystalline and amorphous silica (SiO2) and alumina (Al2O3) is evaluated in\r\nregard to the mechanisms of Ostwald ripening and particle migration and coalescence. Sinter\r\nstudies at 750°C in air reveal an enhanced thermal stability on the amorphous alumina-support\r\nAl2O3(a). Second, key influencing parameters on the sinter resistivity of the Pt NPs are identified.\r\nAn increased NP adhesion on the amorphous substrates, a higher roughness and surface potential,\r\nas well as a larger contact angle of water on Al2O3(a) are all found to significantly contribute to\r\nenhanced sinter stability.\r\nFurthermore, the thermal behavior of Pt NPs on dual-structured surfaces is examined at the interface\r\nbetween Al2O3(a) and SiO2 to study the impact of compositional surface heterogeneities.\r\nThe particles favor the high metal interaction Al2O3(a)-side over the low metal interaction SiO2-\r\nside as shown by their diffusion away from the silica. Additionally, structural heterogeneities\r\non sapphire wafers with varying tilt angles, and thus step edges of different height and size,\r\ncontribute to a smaller increase in Pt NP diameter over time on the more tilted substrates when\r\nexposed to 1200°C under vacuum compared to NPs on less tilted substrates. Hereby, larger\r\nsintered particles are observed to preferably align along the step edges. This is due to a locally\r\nincreased surface potential at the edges and because these edges function as Ehrlich-Schwoebel\r\nbarriers. Thereby they hinder the diffusion of particles on the substrate. Lastly, the sinter stability\r\nof Pt NPs is successfully enhanced via the deposition of an isolating silica or alumina layer by solgel\r\ntechniques. These films are shown not to cover the Pt NPs and also prevent the migration of\r\nplatinum clusters toward each other during sinter studies at 750°C under atmospheric conditions.\r\nTaken together, this data contributes to a better understanding of the thermal stability of Pt NPs\r\ncatalysts with respect to the underlying support. The information gained from these sinter studies\r\ncan be harnessed in the design of more thermally stable Pt NP catalysts, which can ultimately\r\ncontribute to more environmentally sustainable technologies."^^ . "2020" . . . . . . . "Susanne Veronika"^^ . "Ott"^^ . "Susanne Veronika Ott"^^ . . . . . . "Sintering properties of platinum nanoparticles on different oxide-based substrates (PDF)"^^ . . . "Doktorarbeit_Ott Susanne_neu.pdf"^^ . . . "Sintering properties of platinum nanoparticles on different oxide-based substrates (Other)"^^ . . . . . . "indexcodes.txt"^^ . . . "Sintering properties of platinum nanoparticles on different oxide-based substrates (Other)"^^ . . . . . . "lightbox.jpg"^^ . . . "Sintering properties of platinum nanoparticles on different oxide-based substrates (Other)"^^ . . . . . . "preview.jpg"^^ . . . "Sintering properties of platinum nanoparticles on different oxide-based substrates (Other)"^^ . . . . . . "medium.jpg"^^ . . . "Sintering properties of platinum nanoparticles on different oxide-based substrates (Other)"^^ . . . . . . "small.jpg"^^ . . "HTML Summary of #26096 \n\nSintering properties of platinum nanoparticles on different oxide-based substrates\n\n" . "text/html" . . . "540 Chemie"@de . "540 Chemistry and allied sciences"@en . .