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Modelling nano-oxide materials with technological and environmental relevance : silica, titania and titanosilicates

Abstract : In this thesis we focus on modelling of titania, silica and titanosilicate based nano materials because of their technological importance as they are employed in heterogeneous (photo-)catalysis, in electronics gas-sensing etc. to cite a few. For such systems, we firstly performed global optimization studies in gas-phase and water containing environments in order to identify the structures of nanoparticles. Secondly, we studied structural, energetic and electronic size-dependent properties of such nanoparticles as well as their reducibility, extrapolating up to the bulk macroscopic level in some cases. For such characterization we use accurate quantum mechanical methods based on the Density Functional Theory (DFT). Our results point to a series of important predictions such us: i) the crystallinity of titania nanoparticles, which is the key property for the photoactivity, is predicted to emerge when nanoparticles become larger than 2.0-2.5 nm; ii) the mixing of titania and silica to form titanosilicates is found be thermodynamically favorable at the nanoscale, contrary to the bulk; iii) the hydration of silica and titania nanoclusters, which plays an important role in the aggregation and nucleation process during the synthesis of larger nanoparticles, is controlled by environmental factors such as temperature and water vapor pressure as predicted from calculated phase diagrams.
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  • HAL Id : tel-02865355, version 2

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Andi Cuko. Modelling nano-oxide materials with technological and environmental relevance : silica, titania and titanosilicates. Theoretical and/or physical chemistry. Sorbonne Université; Universitat de Barcelona, 2018. English. ⟨NNT : 2018SORUS368⟩. ⟨tel-02865355v2⟩

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