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See detailTiO2 thin films (1 µm) with ordered porosity used as high performance photoelectrode in DSSC
Dewalque, Jennifer ULg; Cloots, Rudi ULg; Dubreuil, Olivier et al

Poster (2010, July 06)

Mesoporous anatase thin films are very promising materials to act as electrode in dye-sensitized solar cells. Randomly oriented nanocrystalline TiO2 particles are usually used to prepare photoelectrodes ... [more ▼]

Mesoporous anatase thin films are very promising materials to act as electrode in dye-sensitized solar cells. Randomly oriented nanocrystalline TiO2 particles are usually used to prepare photoelectrodes with a thickness of 10-15 µm. Templated-assisted dip-coating techniques are used to obtain thin films with ordered porosity. The use of different templates influences the film porosity in terms of long-range order, percentage of porosity, pore size and pores connectivity. The photovoltaic performances of the samples have been evaluated. Such mesostructured films are compared in terms of photovoltaic performance with TiO2 nanoparticles films, generally used in DSSC. [less ▲]

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See detailRepeated thermal treatments applied to ordered TiO2 mesoporous thin film: Effect on the film crystallization and surface area
Henrist, Catherine ULg; Dubreuil, Olivier; Krins, Natacha ULg et al

Conference (2010, July 06)

Ordered, mesoporous films are prepared by template-assisted sol-gel techniques such as dip-coating from a precursors solution. However, monolayer films are only a few hundred nanometers thick and present ... [more ▼]

Ordered, mesoporous films are prepared by template-assisted sol-gel techniques such as dip-coating from a precursors solution. However, monolayer films are only a few hundred nanometers thick and present a limited surface area of active material resulting in poor photovoltaic performances. Therefore it is needed to increase the film thickness. A multilayer deposition process for anatase mesoporous film has been reported in the literature in 2005 by Zukalova and all. Unfortunately, later researches have shown a surface area limitation despite the increase of film thickness due to the repeated thermal treatments applied to the layers. In this study, we have investigated the microstructural evolution of a single mesoporous TiO2 layer submitted to repeated thermal treatments. The modifications are discussed in terms of film thickness, surface area, anatase crystals size and global crystallinity. Besides, we propose an alternative thermal treatment designed in an attempt to overcome the limitations induced by repeated calcinations. We have followed and compared the properties of mesoporous films submitted to both thermal treatments by X-ray diffraction (XRD), transmission electron microscopy (TEM) and environmental poroellipsometry (EEP). Those results show the importance of the tuning of thermal treatment when multilayers films are envisaged for DSSC applications. Indeed, this study quantifies the maximum perturbation encountered by the first layer during the preparation of a multilayer (up to 12) coating, which is submitted to a multistep calcination. Finally, the photovoltaic performances of assembled cells have been evaluated. [less ▲]

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See detailSynthesis of hybrid lamellar silica by liquid crystal templating and silanation
Toussaint, Gilles; Henrist, Catherine ULg; Vertruyen, Bénédicte ULg et al

in Advances in Science and Technology (2010), 68

This paper is focused on the preparation and characterization of different lamellar silica prepared by liquid crystal templating and silanisation. The initial template can be removed and replaced in the ... [more ▼]

This paper is focused on the preparation and characterization of different lamellar silica prepared by liquid crystal templating and silanisation. The initial template can be removed and replaced in the interlamellar spaces by different types of silane, being covalently grafted to the solid by reaction with the surface silanols. The lamellar stacking periodicity remains after this modification. The surfactant extraction can lead in significant grafting of isopropanol if the solid is simply refluxed in isopropanol, which have the effect of preserving the periodicity of the lamellar stacking. The surfactant extraction in an Soxhlet equipment avoid this reaction, with the effect of platelets organization collapsing. The lamellar silica studied exhibit great specific surface and combination of meso and microporosity, making them interesting materials for nanocomposite or catalysis applications. [less ▲]

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See detailStructural and magnetic properties of nanosized barium hexaferrite powders obtained by microemulsion technique
Koutzarova, Tantyana; Kolev, Svetoslav; Ausloos, Marcel ULg et al

in Diffusion and Defect Data--Solid State Data, Pt. B: Solid State Phenomena (2010), 159

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See detailImprovement of the thermoelectric properties of [Bi1.68Ca2O4-delta](RS)[CoO2](1.69) cobaltite by chimie douce methods
Muguerra, Hervé; Rivas-Murias, Beatriz; Traianidis, Maria et al

in Journal of Solid State Chemistry (2010), 183(6), 1252-1257

[Bi1 68Ca2O4 delta](RS)[CoO2](1 69) has been obtained by different chimie douce methods and uniaxially or isostatically pressed The influence of these parameters on the thermoelectric properties has been ... [more ▼]

[Bi1 68Ca2O4 delta](RS)[CoO2](1 69) has been obtained by different chimie douce methods and uniaxially or isostatically pressed The influence of these parameters on the thermoelectric properties has been investigated. Contrary to the Seebeck coefficient, which remains unchanged, the electrical conductivity is greatly modified In particular, spray-drying synthesis followed by uniaxial pressing results in an electrical conductivity two times larger than in the case of conventional solid state synthesis. Our results suggest that a narrow particle size distribution is beneficial to the thermoelectric properties of the layered compounds. The spray-drying technique seems to be promising to Improve the electrical conductivity of layered materials. Moreover, this method presents other advantages (homogeneous samples and less energetic processing) which could be interesting to the future manufacturing of thermoelectric devices (C) 2010 Elsevier Inc. All rights reserved [less ▲]

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See detailEnhancement of the power factor of [Bi1.68Ca2O4](RS)[CoO2](1.69) - Ag composites prepared by the spray-drying method
Rivas-Murias, B.; Muguerra, Hervé ULg; Traianidis, M. et al

in Solid State Sciences (2010), 12(8), 1490-1495

[Bi1.68Ca2O4](RS)[CoO2](1.69) (BCCO) sample and Ag-BCCO composites (with 10, 20 or 30 wt% Ag) have been prepared by the spray-drying technique and uniaxially/isostatically packed. Scanning electron ... [more ▼]

[Bi1.68Ca2O4](RS)[CoO2](1.69) (BCCO) sample and Ag-BCCO composites (with 10, 20 or 30 wt% Ag) have been prepared by the spray-drying technique and uniaxially/isostatically packed. Scanning electron microscopy reveals that the Ag particles are well distributed in the BCCO cobaltite matrix at low Ag contents. The Ag particles have an important effect on densification and grain orientation of the samples, with a direct impact on their electrical conductivity. The electrical conductivity is higher for the uniaxial samples and increases with the Ag content up to 20% in weight, while the Seebeck coefficient is hardly affected. These features induce an improvement of the power factor, reaching a maximum value of 2.2 mu W K-2 cm(-1) at similar to 1050 K for the uniaxial sample with 20 wt% Ag. Our results suggest that the spray-drying technique is a promising method to obtain composites with a well-dispersed secondary phase. (C) 2010 Elsevier Masson SAS. All rights reserved. [less ▲]

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See detailAg-and SiO2-doped porous TiO2 with enhanced thermal stability
Braconnier, Benoît ULg; Páez Martínez, Carlos ULg; Lambert, Stéphanie ULg et al

in Microporous and Mesoporous Materials (2009), 122

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See detailControl of the porosity of anatase thin films prepared by EISA: Influence of thickness and heat treatment
Henrist, Catherine ULg; Dewalque, Jennifer ULg; Mathis, François ULg et al

in Microporous and Mesoporous Materials (2009), 117

Mesoporous anatase thin films were prepared by the evaporation-induced self-assembly process. This paper reports a study of the influence of several physical parameters on the long-range ordering of the ... [more ▼]

Mesoporous anatase thin films were prepared by the evaporation-induced self-assembly process. This paper reports a study of the influence of several physical parameters on the long-range ordering of the mesopores. A preliminary study was done to set the best humidity conditions during dip-coating and ageing of the films. The withdrawal speed, already known to modify the thickness of the deposited film, was shown to exert a strong influence on the percentage of porosity. This was studied by step profilometry combined with Rutherford backscattered spectrometry (RBS). In parallel, small angle X-ray scattering (SAXS), X-ray diffraction (XRD), transmission electron microscopy (TEM) and RBS were used to tune the precise thermal treatment applied to the so-obtained films, in order to preserve the porous mesostructure and promote the nanocrystallization of anatase TiO2. [less ▲]

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See detailHybrid lamellar silica: Combined template extraction and hydrophilic silanation
Toussaint, Gilles ULg; Brisbois, Magali ULg; Grandjean, Jean ULg et al

in Journal of Colloid & Interface Science (2009), 329(1), 120-126

The surface modification of lamellar silica prepared by liquid crystal templating has been investigated. Two hydrophilic surface modifier agents, 2-glycidoxypropyltrimethoxysilane and 2-[methoxy ... [more ▼]

The surface modification of lamellar silica prepared by liquid crystal templating has been investigated. Two hydrophilic surface modifier agents, 2-glycidoxypropyltrimethoxysilane and 2-[methoxy(polyethyleneoxy)propyl)] trimethoxysilane, have been tested. Characterizations of the modified silica include thermal analysis, C-13 and Si-29 solid state NMR, transmission electron microscopy (TEM) and X-ray diffraction (XRD). The different characterizations confirmed the preservation of the lamellar morphology and the Successful surface modification with both silanes along with the template elimination. The results also indicate that the structure and length of the silanes influence the final lamellar organization as well as the grafting yields and mechanisms. (C) 2008 Elsevier Inc. All rights reserved. [less ▲]

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See detailEffects of Rice Straw on the Color and Microstructure of Bizen, a Traditional Japanese Stoneware, as a Function of Oxygen Partial Pressure
Kusano, Y.; Doi, A.; Fukuhara, M. et al

in Journal of the American Ceramic Society (2009), 92(8), 1840-1844

The effects of oxygen partial pressure during thermal treatment on the color and microstructure of Bizen, a traditional Japanese stoneware, were studied through model experiments using clay pellets ... [more ▼]

The effects of oxygen partial pressure during thermal treatment on the color and microstructure of Bizen, a traditional Japanese stoneware, were studied through model experiments using clay pellets covered lightly with rice straw as a coloring assistant. When heated in flowing nitrogen, the model pellet turned blackish owing to the formation of alpha-Fe particles coated with graphite. However, schreibersite (Fe3P), which is also blackish, was formed specifically on the pellet surface in direct contact with the straw. The rice straw seems to have generated a strongly reducing atmosphere, strong enough for the metallization to alpha-Fe, and also to have provided phosphorus through contact. When oxygen content in the surrounding gas atmosphere was raised to N-2/O-2=99/1, the pellet surface turned yellowish brown because the main coloring material was Fe3+-containing mullite. At oxygen contents of N-2/O-2=98/2 or more, the formation of hematite (alpha-Fe2O3) pushed the color to deep red. [less ▲]

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See detailTiO2 mesoporous thin films acting as photoelectrode in dye-sensitized solar cells
Dewalque, Jennifer ULg; Cloots, Rudi ULg; Henrist, Catherine ULg

Conference (2008, December 03)

This study aims at developing thin films of nanocrystalline, mesostructured titanium dioxide in order to build low cost and efficient photovoltaic devices. The synthesis is based on the Evaporation ... [more ▼]

This study aims at developing thin films of nanocrystalline, mesostructured titanium dioxide in order to build low cost and efficient photovoltaic devices. The synthesis is based on the Evaporation Induced-Self Assembly method using titanium isopropoxide as inorganic source, block copolymers as structuring and porogeneous agents and ethanol as solvent. The films were obtained by dip-coating various substrates in the solution. The influence of different experimental parameters, such as dip-coating and ageing relative humidity, withdrawal speed, surfactant:Ti ratio, substrate, was studied. The post-deposition thermal treatment had to be accurately adjusted in order to maximise the crystallisation of the inorganic network while avoiding the collapse of the porous mesostructure. The final structure obtained is discussed in the light of the XRD results combined with TEM analysis. Moreover the cell performance is limited by the film thickness which is mainly responsible of the small amount of absorbed light. Therefore a multilayer deposition process was studied and the as-obtained mesostructure was characterized by TEM, RBS and environmental ellipsometry. [less ▲]

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See detailElaboration of Magnetic Nanodots by Nanosphere Lithography : a Computerized Method for Order Quantification
Colson, Pierre ULg; Cloots, Rudi ULg; Henrist, Catherine ULg

Conference (2008, December 01)

Nanosphere lithography (NSL) is an ideal inexpensive fabrication tool for producing regular, nearly homogenous arrays of nanoparticules with different sizes. There are many different methods for the ... [more ▼]

Nanosphere lithography (NSL) is an ideal inexpensive fabrication tool for producing regular, nearly homogenous arrays of nanoparticules with different sizes. There are many different methods for the fabrication of the latex monolayer based on electrophoresis, the controlled evaporation of a solvent from the suspension containing latex particles, spincoating etc… We focused our work on this last method. The main problem with formation of 2D latex monolayers is that there are always a high number of different structural defects such as: point defects (vacancies), line defects (dislocations) and also many disordered areas. The influence of the different spincoating parameters on the amount of defects was determined by image analysis of SEM micrographies from the different samples. FePt and Co films were deposited onto quartz substrates through the polystryrene monolayers by magnetron sputtering. The nanopsheres were removed by sonication in toluene. Post-deposition annealing treatment was performed under reductive atmosphere for the FePt nanodots in order to transform the as-deposited chemically disoredered face-centered cubic (fcc) structure into the chemically ordered face-centered tetragonal (fct) phase (L10-phase). DRX , SEM and MFM analysis were performed on the different samples. [less ▲]

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See detailMesoporous TiO2 thin films for photovoltaic applications
Dewalque, Jennifer ULg; Cloots, Rudi ULg; Mathis, François ULg et al

Poster (2008, September 08)

Thin films of nanocrystalline, mesostructured titanium dioxide are very promising materials to build low cost and efficient photovoltaic devices. TiO2 present a high chemical stability and electronic ... [more ▼]

Thin films of nanocrystalline, mesostructured titanium dioxide are very promising materials to build low cost and efficient photovoltaic devices. TiO2 present a high chemical stability and electronic properties such as photoinduced electronic transfer properties associated with the anatase phase. For many applications, highly porous nanostructured thin films with accessible pores are preferable to dense ones. Indeed, high accessible porosity leads to high surface area increasing the electron transfer area. [less ▲]

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See detailMesoporous TiO2 thin films for photovoltaic applications
Dewalque, Jennifer ULg; Mathieu, Xavier; Decroly, André et al

Poster (2008, August)

Thin films of nanocrystalline, mesostructured titanium dioxide are very promising materials to build low cost and efficient photovoltaic devices. TiO2 present a high chemical stability and electronic ... [more ▼]

Thin films of nanocrystalline, mesostructured titanium dioxide are very promising materials to build low cost and efficient photovoltaic devices. TiO2 present a high chemical stability and electronic properties such as photo-induced electronic transfer properties associated with the anatase phase. For many applications, highly porous nanostructured thin films with accessible pores are preferable to dense ones. Indeed, high accessible porosity leads to high surface area increasing the electron transfer surface. [less ▲]

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See detailTailor-made morphologies for Pd/SiO2 catalysts through sol-gel process with various silylated ligands
Lambert, Stéphanie ULg; Tran, Kim Yên; Arrachart, Guilhem et al

in Microporous and Mesoporous Materials (2008), 115

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See detailThe rocker bone: a new kind of mineralised tissue?
Parmentier, Eric ULg; Compère, Philippe ULg; Casadevall, Margarida et al

in Cell & Tissue Research (2008), 334

In some Ophidiiform fishes, the anterior part of the swimbladder is thickened into a hard structure called the “rocker bone”, which is thought to play a role in sound production. Although this structure ... [more ▼]

In some Ophidiiform fishes, the anterior part of the swimbladder is thickened into a hard structure called the “rocker bone”, which is thought to play a role in sound production. Although this structure has been described as cartilage or bone, its nature is still unknown. We have made a thorough analysis of the rocker bone in Ophidion barbatum and compared it with both classical bone and cartilage. The rocker bone appears to be a new example of mineralisation. It consists of (1) a ground substance mainly composed of proteoglycans (mucopolysaccharide acid) and fibres and (2) a matrix containing small mineralised spherules composed of a bioapatite and fibrils. These spherules are embedded in mineralised cement of a similar composition to the spherules themselves. The rocker bone grows via the apposition of new apatite spherules at its periphery. These spherules are first secreted by the innermost fibroblast layer of the capsule contained in the rocker bone and then grow extracellularly. Blood vessels, which represent the only means of transport for matrix and mineral material, are numerous. They enter the rocker bone via the hyle and ramify towards the capsule. We propose to call this new kind of mineralised tissue constituting the rocker bone “frigolite” (the Belgian name for styrofoam) in reference to the presence of spherules of different sizes and the peculiarity of the rocker bone in presenting a smooth surface when fractured. [less ▲]

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See detailOtolith crystals (in Carapidae): Growth and habit
Parmentier, Eric ULg; Cloots, Rudi ULg; Warin, R. et al

in Journal of Structural Biology (2007), 159(3), 462-473

The biomineralization of otoliths results mainly from the release of soluble Ca(2+), which is in turn precipitated as CaCO(3) crystals. In some Carapidae, sagittae sections have been shown to reveal a ... [more ▼]

The biomineralization of otoliths results mainly from the release of soluble Ca(2+), which is in turn precipitated as CaCO(3) crystals. In some Carapidae, sagittae sections have been shown to reveal a three-dimensional asymmetry with a nucleus close to the sulcal side, an unusual position. This study seeks to understand otolith formation in Carapus boraborensis. The unusual shape of the otolith is partly explained by the distribution of the epithelium cells, and particularly the sensory epithelium. Experimental evidence shows for the first time that aragonite growth takes place along the c-axis. These aragonite needles present two different habits. On the sulcal side is found the acicular form resulting from rapid growth during a short period of time. On the anti-sulcal side, the prismatic form seen there is due to a slower growth speed over longer periods. The otolith surface was observed each hour during a period of 24h in fishes reared in similar conditions. This allowed for the first time the direct observation on the otolith surface of the deposition of the two layers (L-zone and D-zone). In C. boraborensis, the organic-rich layer (D-zone) develops during the day, whereas the CaCO(3) layer (L-zone) seems to be deposited during the night. [less ▲]

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See detailSynthesis of La0.9Sr0.1Ga0.8Mg0.2O2.85 by successive freeze-drying and self-ignition of a hydroxypropylmethyl cellulose solution
Traina, Karl ULg; Steil, M. C.; Pirard, Jean-Paul ULg et al

in Journal of the European Ceramic Society (2007), 27(12), 3469-3474

The present paper reports the synthesis of La0.9Sr0.1Ga0.8Mg0.2O2.85 perovskite powders by a method combining freeze-drying and self-ignition of an aqueous solution of metallic nitrates containing ... [more ▼]

The present paper reports the synthesis of La0.9Sr0.1Ga0.8Mg0.2O2.85 perovskite powders by a method combining freeze-drying and self-ignition of an aqueous solution of metallic nitrates containing hydroxypropylmethyl cellulose. The precursor powder obtained after self-ignition was submitted to various thermal treatments and the resulting powders were characterized by X-ray diffraction, electron microscopy, nitrogen adsorption-desorption isotherm analysis, mercury porosimetry and laser granulometry. It turns out that this synthesis method yields single-phase powders with good homogeneity and sinterability properties. The precursor powder treated at 1200 degrees C presents a coral-like structure which collapses under application of low uniaxial pressure, resulting in a narrow grain size distribution suitable for sintering (98.8% relative density for a pellet sintered at 1400 degrees C during 1 h). The fact that no milling step is necessary is an additional advantage of this method, which shows promising prospects for the synthesis of other multicationic oxides. (c) 2007 Elsevier Ltd. All rights reserved. [less ▲]

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See detailSynthesis and characterization of inorganic, lamellar nanofillers with high aspect ratio
Henrist, Catherine ULg; Rulmont, André ULg; Cloots, Rudi ULg

in Journal of the European Ceramic Society (2007), 27(2-3), 1023-1027

Mesostructured silica phases with lamellar structure were prepared by the liquid crystal templating (LCT) technique, from double chain alkylammonium surfactant and sodium silicate or ... [more ▼]

Mesostructured silica phases with lamellar structure were prepared by the liquid crystal templating (LCT) technique, from double chain alkylammonium surfactant and sodium silicate or tetraethylorthosilicate (TEOS) silica precursors. The structural characterization of these phases is presented and compared. Surface modification of the silica layers, together with elimination of the organic template, is considered. Finally, a representative model of the microstructural organization is proposed. (c) 2006 Elsevier Ltd. All rights reserved. [less ▲]

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