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See detailSol-gel preparation of pure and doped TiO2 films for the photocatalytic oxidation of ethanol in air
Cimieri, Iolanda; Poelman, Hilde; Avci, Nursen et al

in Journal of Sol-Gel Science and Technology (2012), 63

Stable sols of TiO2 were synthesized by a non-aqueous sol-gel process using titanium (IV) isopropoxide (TTIP) as precursor. The microstructure, optical and morphological properties of the films obtained ... [more ▼]

Stable sols of TiO2 were synthesized by a non-aqueous sol-gel process using titanium (IV) isopropoxide (TTIP) as precursor. The microstructure, optical and morphological properties of the films obtained by spin-coating from the sol, and annealed at different temperatures, were investigated using SEM, TEM, diffuse reflectance spectroscopy (DRS) and ellipsometry. The crystalline structure of the films was characterized by X-ray diffraction and their photocatalytic activity was evaluated for the oxidation of ethanol in air. The influence of the calcination temperature, pre-heat treatment and the number of layers was studied. Simultaneous thermo-gravimetric and differential thermal analysis (TG/DTA) measurements were carried out to ascertain the thermal decomposition behavior of the precursors. In order to obtain a higher photoresponse in the visible region, a series of vanadium-, niobium- and tantalum-doped TiO2 catalysts was synthesized by the same sol-gel method. For V doping two different precursors, a vanadium alkoxide and V2O5, were used. The effect on the crystallization and photocatalytic activity of the doped TiO2 films was investigated. Furthermore, to identify the effective composition of the samples, they were characterized by X-ray photoelectron spectroscopy (XPS) and the surface area of the powders was measured by N2 adsorption. The 10wt.% doped catalysts exhibit high photocatalytic activity under visible light and among them the best performance was obtained for the sample containing Ta as dopant. The crystallite sizes are closely related to the photocatalytic activity. [less ▲]

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See detailThe microstructure of hybrid silica gels and its modification by evaporative and supercritical dryings
Gommes, Cédric ULg; Blacher, Silvia ULg; Pirard, Jean-Paul ULg et al

in Journal of Sol-Gel Science and Technology (2007), 44(3), 211-218

The effect of evaporative drying on the pore size of two series of hybrid silica gels is investigated by combining beam bending on the gels and mercury porosimetry on the aerogels and xerogels with ... [more ▼]

The effect of evaporative drying on the pore size of two series of hybrid silica gels is investigated by combining beam bending on the gels and mercury porosimetry on the aerogels and xerogels with transmission electron microscopy on the xerogels. It is shown that the shrinkage of the pores during drying is different in the two series: in one series the pores shrink proportionally to their volume, in the other the pores collapse until they all reach the same size. The experimental data enable us to discuss the relation between these two different behaviours and the different morphology of the two series of gels. [less ▲]

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See detailNucleation phenomenon in silica xerogels and Pd/SiO2, Ag/SiO2, Cu/SiO2 cogelled catalysts
Alié, Christelle ULg; Lambert, Stéphanie ULg; Heinrichs, Benoît ULg et al

in Journal of Sol-Gel Science and Technology (2003), 26(1-3), 827-830

Pd/SiO2, Ag/SiO2 and Cu/SiO2 xerogel catalysts have been synthesized by cogelation of tetraethoxysilane (TEOS) and chelates of Pd, Ag and Cu with 3-(2-aminoethylamino) propyltrimethoxysilane (EDAS). It ... [more ▼]

Pd/SiO2, Ag/SiO2 and Cu/SiO2 xerogel catalysts have been synthesized by cogelation of tetraethoxysilane (TEOS) and chelates of Pd, Ag and Cu with 3-(2-aminoethylamino) propyltrimethoxysilane (EDAS). It appears that, in cogelled samples, the metal complex acts as a nucleation agent in the formation of silica particles. The resulting catalysts are then composed of completely accessible metallic crystallites with a diameter of about 3 nm located inside silica porous particles with a monodisperse microporous distribution. Xerogels without metal synthesized with EDAS and TEOS (C. Alie, R. Pirard, A. J. Lecloux, and J.-P. Pirard, J. Non-Cryst. Solids 289, 88 (2001)) verify this hypothesis of nucleation by EDAS. [less ▲]

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See detailPorous silica obtained from biodegradable and biocompatible inorganic-organic hybrid materials
Tian, Dong; Blacher, Silvia ULg; Dubois, Philippe ULg et al

in Journal of Sol-Gel Science and Technology (1998), 13(1-3), 415-419

Porous silicas have been successfully prepared from poly(ε -caprolactone) (PCL)-silica hybrid materials based on the template approach. The final texture of the porous silica can be tailored by the PCL ... [more ▼]

Porous silicas have been successfully prepared from poly(ε -caprolactone) (PCL)-silica hybrid materials based on the template approach. The final texture of the porous silica can be tailored by the PCL template, i.e., molecular weight and molecular weight distribution, content, type and number of reactive end-groups per chain. Porosity has been investigated by nitrogen adsorption-desorption technique and small angle X-ray scattering (SAXS). [less ▲]

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See detailMercury porosimetry applied to low density xerogels; relation between structure and mechanical properties
Pirard, René ULg; Heinrichs, Benoît ULg; Van Cantfort, Olivier et al

in Journal of Sol-Gel Science and Technology (1998), 13(1-3), 335-339

Samples of low density xerogels were submitted to mercury porosimetry at pressures up to 200 MPa. These samples show an unusual behavior: they are first crushed by the isostatic mercury pressure without ... [more ▼]

Samples of low density xerogels were submitted to mercury porosimetry at pressures up to 200 MPa. These samples show an unusual behavior: they are first crushed by the isostatic mercury pressure without mercury intrusion and are then intruded by the mercury above a certain pressure. This transition allows the easy determination of the one constant found in the buckling model that is used to interpret the crushing part of the mercury porosimetry experiment. The relation between this constant and the structure of the xerogels determined by TEM and nitrogen adsorption is discussed. [less ▲]

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See detailRheological characterization of BaTiO3 sol-gel transition
Brasseur, Alain; Michaux, Bernard; Pirard, René ULg et al

in Journal of Sol-Gel Science and Technology (1997), 9(1), 5-15

BaTiO3 gels were prepared by hydrolysis and polycondensation reactions between titanium isopropoxide and barium hydroxide in presence of methoxyethanol, methanol and water. The rheology of the sol-gel ... [more ▼]

BaTiO3 gels were prepared by hydrolysis and polycondensation reactions between titanium isopropoxide and barium hydroxide in presence of methoxyethanol, methanol and water. The rheology of the sol-gel transition was studied with a rheometer allowing low amplitude sinusoidal oscillations. Experimental data show a continuous increase in the complex viscosity along with time, showing the progressive character of the transition. The influence of synthesis operating variables was studied. The gelation time, which definition is based on viscoelastic measurements, increases exponentially when the water content is increased, when the dilution due to the methoxyethanol is reduced or when the temperature is lowered. Different growth models were used for the characterization of the particles in the solution. These models suggest that the polymerisation first produces spherical particles (mass fractals) and that these spherical particles then agglomerate to form a linear network. [less ▲]

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See detailSynthesis and characterization of porous silica-alumina xerogels
VanCantfort, Olivier; Abid, A.; Michaux, Bernard et al

in Journal of Sol-Gel Science and Technology (1997), 8

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See detailSynthesis and characterization of monodisperse spherical zirconia particles
Van Cantfort, Olivier; Michaux, Bernard; Pirard, René ULg et al

in Journal of Sol-Gel Science and Technology (1997), 8

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See detailTextural properties and thermal stability of silica-zirconia aerogels
Pirard, René ULg; Bonhomme, Damien; Kolibos, Sofia et al

in Journal of Sol-Gel Science and Technology (1997), 8

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See detailSYNTHESIS OF SIO2-TIO2 XEROGELS BY SOL-GEL PROCESS
Pirson, Anne-Marie ULg; MOHSINE, Abdel; Marchot, Pierre ULg et al

in Journal of Sol-Gel Science and Technology (1995), 4(3), 179-185

A new method to synthesize SiO2-TiO2 gels by sol-gel process has been developed. This technique uses tetraisopropylorthotitanate [Ti(O'Pr)(4)] and tetraethylorthosilicate [TEOS]: they are mixed in the ... [more ▼]

A new method to synthesize SiO2-TiO2 gels by sol-gel process has been developed. This technique uses tetraisopropylorthotitanate [Ti(O'Pr)(4)] and tetraethylorthosilicate [TEOS]: they are mixed in the same solvent and then directly hydrolysed. This one-step reaction is possible because of the use of 2-methoxyethanol, a protic polar solvent. This alcohol plays two different specific roles: it acts as a solvent as well as a stabilizer of titanium alkoxide towards the hydrolysis-precipitation reaction. So, by an accurate adjustment of the quantity of methoxyethanol in the mixture, we can control the reactivity of the titanium precursor. Monolithic and transparent xerogels were obtained whatever the composition. Three monolithic SiO2-TiO2 gels containing 20, 50 and 75 mol% of TiO2 were prepared and studied in details. By using the TG-DSC analysis, we can follow the evolution of the loss of water and organic residues. The structural evolution of gels during calcination is characterized by IR spectroscopy and X-Ray diffraction. [less ▲]

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