van der Waals cohesion in Non Smooth Contact Dynamics : application to powder mixtures

in Canadian Journal of Physics (2011)

Characterization of surface and porous properties of synthetic hybrid lamellar silica

in Journal of Non-Crystalline Solids (2011), 357

Synthetic lamellar silica and hybrid lamellar silicas have been prepared by liquid crystal templating, template extraction and silanization. The samples have been characterized by thermogravimetric ... [more ▼]

Synthetic lamellar silica and hybrid lamellar silicas have been prepared by liquid crystal templating, template extraction and silanization. The samples have been characterized by thermogravimetric analysis (TGA), carbon analysis, spectroscopy, X-ray diffraction (XRD) and nitrogen adsorption. The XRD analyses have shown that the lamellar periodic stacking is preserved for all samples. The quantity and type of organic molecules at the silica surface have been evaluated by carbon analysis, TGA and spectroscopy. The covalent grafting of the solvent used for extraction of the initial surfactant has been highlighted by these analyses. The nitrogen adsorption analyses have revealed three categories of pores and two types of samples. The initial lamellar silica exhibits a very low specific surface area and plate-like type of pores. The second type of samples is made up of the hybrid samples and the initial substrate from whom the surfactant has been extracted. These samples show a significantly higher specific surface area with interlamellar spaces corresponding to narrow-slit like mesopores around 4 nm. The nitrogen adsorption data analysis has highlighted the presence of micropores within the silica sheets. The difference of the specific surface is due to pore blocking by the surfactant impeding the access to nitrogen into interlamellar spaces and by the silanes covering the pores once the surface modified. The presence of micro and mesopores combined to a high BET specific surface of 612 m²/g makes these lamellar silicas interesting materials for catalysis applications. [less ▲]

Design and characterization of novel stealth Gd(II)-DOTA conjugates for magnetic resonance inaging (MRI)

Poster (2010, November 29)

Polymer micelles decorated by gadolinium complexes as MRI blood contrast agents: design, synthesis and properties

in Polymer Chemistry (2010), 1

New micellar macrocontrast agents with improved contrast at high frequencies were designed by grafting a gadolinium based contrast agent onto functional stealth micelles formed by poly(ethylene oxide)-b ... [more ▼]

New micellar macrocontrast agents with improved contrast at high frequencies were designed by grafting a gadolinium based contrast agent onto functional stealth micelles formed by poly(ethylene oxide)-b-poly(ε-caprolactone) (PEO-b-PCL) in water. As evidenced by relaxometry measurements and the hemolytic CH50 test, the new contrast agents are of interest as MRI blood pool agents. [less ▲]

Repeated thermal treatments applied to ordered TiO2 mesoporous thin film: Effect on the film crystallization and surface area

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 ▲]

Design and characterization of novel stealth Gd(III)-DOTA conjugates for magnetic resonance imaging (MRI)

Poster (2010, March 18)

Analysis of thin layers for photovoltaic application: Comparison between RBS and ellipsometry on the determination of roughness and porosity

Poster (2010)

Improvement of the thermoelectric properties of [Bi1.68Ca2O4-delta](RS)[CoO2](1.69) cobaltite by chimie douce methods

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 ▲]

Enhancement of the power factor of [Bi1.68Ca2O4](RS)[CoO2](1.69) - Ag composites prepared by the spray-drying method

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 ▲]

Vanadium oxide-based mesoporous films as positive electrode material in Li-ion batteries

Conference (2009)