Synthèse et caractérisation de titanates mésoporeux organisés

Abstract : In this work we will study in detail the properties of the mesoporous TiO2 materials, for which the preparation was developed previously via a method combining Liquid Crystal Templating (LCT) and EISA mechanisms, using P123 as template. We have tested, in the first time, extraction and thermal methods efficiency to eliminate surfactant in order to optimize the P123 elimination step. Removal of P123 using water followed by washing with acetone is effective, easy and promotes the formation of the anatase phase of TiO2. Otherwise, the photocatalytic properties of the obtained TiO2 are not important and can be improved after calcination. Combining extraction using water and calcination give rise to mesoporous TiO2 with better photocatalytic activity than that of commercial anatase. The incorporation of zinc and tungsten in the mesoporous well-ordered TiO2 has been investigated in the third time, in order to improve their photocatalytic activity. The introduction of small amounts of zinc (<10 mol%) increases the surface area; beyond this amount the mesostructure is lost. The incorporation of tungsten in the mesoporous TiO2 does not affect the mesopores organization, and orthorhombic WO3 aggregates are formed beside the mesoporous network of anatase TiO2. Although, the presence of zinc or tungsten oxides in the matrix decreases the bandgap of mesoporous TiO2, the photocatalytic activity is not improved. In the third time, the synthesis of bimodal porosity materials, using a mixed surfactant systems hydrogenated/fluorinated, CTABr/RF8(EO)9 and P123/RF8(EO)9, was explored. Based on the phase diagrams of these two systems in water, micellar solutions and liquid crystals have been investigated to prepare mesoporous silicas using two mechanisms CTM and LCT. When CTABr is present, pores of one size in the mesoporous range are observed, however, it is possible that bimodal type micro-mesopores exist. The use of the hexagonal liquid crystal phase of P123/RF8(EO)9 provides two separate pore sizes materials in the mesoporous range.
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Carine Assaker. Synthèse et caractérisation de titanates mésoporeux organisés. Autre. Université de Lorraine, 2014. Français. ⟨NNT : 2014LORR0094⟩. ⟨tel-01750834⟩

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