References of "Léonard, Alexandre"
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See detailFunctionalization of carbon xerogels for the preparation of palladium supported catalysts applied in sugar transformations
Mager, Nathalie; Meyer, Nathalie; Léonard, Alexandre ULg et al

in Applied Catalysis B : Environmental (2014), 148-149

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See detailResorcinol-Formaldehyde Carbon Xerogels as Anode Material for Lithium-Ion Battery: Synthesis, Grinding and Coating on Current Collector
Piedboeuf, Marie-Laure ULg; Léonard, Alexandre ULg; Pirard, Jean-Paul ULg et al

Poster (2013, September 24)

Rechargeable lithium-ion batteries show great advantages over traditional batteries and are extensively used for consumer electronic devices due to their high energy density and long cycle life. However ... [more ▼]

Rechargeable lithium-ion batteries show great advantages over traditional batteries and are extensively used for consumer electronic devices due to their high energy density and long cycle life. However, the improvement of performance of current lithium-ion batteries requires the optimization of the materials used (electrolyte and electrodes). Therefore, tremendous efforts have been dedicated to exploring new materials with high capacity, excellent cycling performance, low cost and high safety features [1-3]. As an example, carbon xerogels are promising candidates in the development of new high performance C-based anode materials for Li-ion batteries, since such carbonaceous materials show very small changes of volume during the charge/discharge process, providing a long cycle life. Nevertheless, hard carbons also exhibit quite high irreversible capacity losses due to their intrinsic high microporosity [4]. To overcome these disadvantages, the structural and textural characteristics need to be carefully controlled. Also, due to the different morphology of these materials compared to graphite, the deposition of carbon xerogels on current collectors needs to be studied in detail. In this work, porous carbon xerogels have been synthesized from Resorcinol-Formaldehyde mixtures by adjusting the pH of the solution in order to obtain different mesopore sizes. Monoliths of carbon xerogels are obtained after drying of the polymer gel and pyrolysis [5]. These monoliths have been ground by two different methods and particle size distributions were measured by granulometry. Mercury intrusion porosimetry and nitrogen adsorption techniques (BET) have been used to characterize the pore texture of the monolithic and the powder materials. Different conditions have been used for the mixing of carbon xerogels with a binder and a solvent to form slurries. The latter have been cast on a copper foil using bar coating with different openings. After evaporation of the solvent, the resulting coatings were analyzed using scanning electron microscopy (SEM) for the morphology and their thickness was monitored by profilometry. First results indicate that the method of grinding has no influence on the final particle size distribution of the powder. The structural features of the carbon xerogels is well preserved for particles down to one micrometer. Nevertheless, a study of grinding duration shows that additional particles with sizes close to that of the porosity of the carbon appear. As a consequence, the grinding conditions were chosen so as to obtain a compromise between particles small enough to realize a coating on a current collector and particles large enough to maintain the carbon gel structural characteristics. References 1) Goodenough J.B., Kim Y. J. Power Sources 2011; 196(16): 6688-6694. 2) Bruce P.G. Solid State Ionics 2008; 179: 752-760. 3) Cairns A. J., Albertus P. Ann. Rev. Chem. Biomol. Eng. 2010; 1: 299-320. 4) Tran T., Yebka B., Song X., Nazri G., Kinoshita K., Curtis D. J. Power Sources 2000; 85: 269-278. 5) Job N., Théry A., Pirard R., Marien J., Kocon L., Rouzaud J., Béguin F., Pirard J. Carbon 2005; 43: 2481-2494. [less ▲]

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See detailMacroporous poly(ionic liquid)s and poly(acrylamide)s monoliths from CO2-in-water emulsion templates stabilized by sugar-based surfactants
Boyère, Cédric ULg; Favrelle, Audrey; Léonard, Alexandre ULg et al

in Journal of Materials Chemistry A (2013), 1(29), 8479-8487

Highly interconnected poly(acrylamide) (PAM) and poly(vinylimidazolium) (PVIm) porous monoliths were templated by carbon 10 dioxide-in-water (CO2/W) high internal phase emulsions (HIPEs), a toxic-solvent ... [more ▼]

Highly interconnected poly(acrylamide) (PAM) and poly(vinylimidazolium) (PVIm) porous monoliths were templated by carbon 10 dioxide-in-water (CO2/W) high internal phase emulsions (HIPEs), a toxic-solvent free process. A range of sugar-based fluorinated surfactants prepared by chemoenzymatic synthesis were used as emulsifiers. Both the concentration and the structure of the surfactants, especially the length of their CO2-philic part and of their spacer between the sugar head and the tail, were found to strongly affect the cellular structure and morphology of the PAM polyHIPEs, i.e. the size of pores and cells. A mannose derivative bearing a chain ranging from 6 to 10 perfluorinated carbons and a long spacer emerged as the best stabilizer, leading to a porous monolith with average pores and 15 cells sizes (about 2.6 1m and 5-10 1m, respectively) among the lowest reported for polyHIPEs produced from CO2/W emulsions. The same template then served for the preparation of the first macroporous poly(ionic liquid)s (PILs) polyHIPE by using 1-vinyl-3- ethylimidazolium bromide as monomer. Shrinkage of the final material was prevented by adjusting the divinylimidazolium crosslinker content. The resulting low density polyHIPE exhibits small spherical cells (~5 1m) connected by numerous small pores (~2 1m), confirming that the CO2/W HIPE templating methodology based on fluorinated glycosurfactants is a technique of choice for the 20 preparation of macroporous PILs. [less ▲]

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See detailXérogels de carbone à base de résorcinol-formaldéhyde en tant que matériaux d’anode pour batterie Li-ion; Synthèse et broyage avec contrôle de la granulométrie
Piedboeuf, Marie-Laure ULg; Léonard, Alexandre ULg; Pirard, Jean-Paul ULg et al

Conference (2013, May)

Xérogels de carbone à base de résorcinol-formaldéhyde en tant que matériaux d’anode pour batteries Li-ion : synthèse et broyage avec contrôle de la granulométrie Les xérogels de carbone sont des candidats ... [more ▼]

Xérogels de carbone à base de résorcinol-formaldéhyde en tant que matériaux d’anode pour batteries Li-ion : synthèse et broyage avec contrôle de la granulométrie Les xérogels de carbone sont des candidats prometteurs en tant que matériaux d’anodes de batterie Li-ion étant donné que leur faible variation de volume lors des cycles de charge-décharge devrait conduire à une durée de vie plus élevée. Néanmoins, du fait de leur morphologie fort différente de celle du graphite, tout un travail de mise au point du dépôt sur collecteur de courant se doit d’être effectué. Une partie de cette étude consiste à contrôler la granulométrie des particules issues du processus de broyage préalable à la préparation d’une encre. Dans ce travail, quatre xérogels de carbone de textures différentes ont été synthétisés et deux méthodes de broyage ont été utilisées pour réduire la taille des monolithes obtenus après synthèse. Les premiers résultats indiquent que la méthode de broyage n’a pas d’influence sur la distribution de la taille des particules et la structure des matériaux est bien conservée pour des particules de taille allant jusqu’au micromètre. [less ▲]

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See detailSynthesis of microsphere-loaded porous polymers by combining emulsion and dispersion polymerisations in supercritical carbon dioxide
Boyère, Cédric ULg; Léonard, Alexandre ULg; Grignard, Bruno ULg et al

in Chemical Communications (2012), 48(67), 8356-8358

Highly porous materials were produced by acrylamide polymerisation templated by supercritical CO2-in-water emulsions using new fluorinated glycosurfactants. Properties of the resulting polymer scaffolds ... [more ▼]

Highly porous materials were produced by acrylamide polymerisation templated by supercritical CO2-in-water emulsions using new fluorinated glycosurfactants. Properties of the resulting polymer scaffolds were tuned by performing dispersion polymerisations within their cavities filled with supercritical CO2. [less ▲]

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See detailResorcinol-formaldehyde carbon xerogels as lithium-ion battery anode materials: influence of porosity on capacity and cycling behaviour
Piedboeuf, Marie-Laure ULg; Léonard, Alexandre ULg; Khomenko, Volodymyr et al

Poster (2012, July 05)

Carbon xerogels are promising candidates in the development of new high performance C-based anode materials for Li-ion batteries. Indeed, their specific capacities widely exceed that of conventional ... [more ▼]

Carbon xerogels are promising candidates in the development of new high performance C-based anode materials for Li-ion batteries. Indeed, their specific capacities widely exceed that of conventional graphitic structures, and they can be intercalated/deintercalated in a low-cost electrolyte based on propylene carbonate (PC), which has an excellent conductivity at low temperatures. In addition, such carbonaceous materials show very small changes of volume during the charge/discharge, providing a long cycle life of such an anode. Nevertheless, hard carbons also exhibit quite high irreversible capacity losses due to their intrinsic high microporosity and, compared to graphite, a poor rate performance related to slow diffusion of Li in the internal structure[1]. To reduce these disadvantages, the structural and textural characteristics need to be carefully controlled. Porous carbon xerogels can easily be prepared from resorcinol-formaldehyde aqueous mixtures, which are polymerized, dried and pyrolysed. The porosity of these xerogels is mainly governed by the pH of the precursor solution as well as by the drying procedure. Globally, these materials are composed of microporous nodules delimiting meso- or macroporous voids, the size of which is adjusted via the synthesis pH. Too a high microporosity can induce considerable irreversible capacity losses and too small mesopores may hinder the proper chemical diffusion of lithium ions within a bulk electrode material. The latter is often a rate-limiting step and optimized transport pathways could be provided by creating large mesopores or even macropores within the microporous carbon [3]. Here we report on the preliminary electrochemical characterization of porous carbon xerogels prepared by vacuum drying procedure. By adjusting the pH of the precursor solution, the materials obtained develop low to high values of specific surface areas and exhibit homogeneous pore sizes that range from several microns to several nanometers. The electrochemical performance of these materials as electrode compounds was tested by galvanostatic charge-discharge of 16-mm disc electrodes assembled in CR2016 coin cells or of 13-mm disc electrodes in home-made Swagelok-type cells. The first results show that all the samples show quite a high irreversible capacity during the first cycle; this irreversible capacity is proportional to the specific surface area. Its value nevertheless remains quite low for the low-surface area macroporous sample. The latter also shows the best reversible capacity after the second cycle, with values approaching that of commonly used graphite. For example, when cycled at a rate of C/20 for 10 cycles, this sample showed a capacity of 320 mAh/g; the value was kept at 200 mAh/g when increasing the rate up to C/5. The long-term cycling performance was investigated by cycling the anodes at C/20 and C/5. Again, the macroporous sample behaves best, with superior capacity retention and invariable discharge capacity of ~175 mAh/g after more than 100 cycles. The electrochemical properties of carbon xerogels was evaluated in the conditions which are used typically for graphite (cycles in the potentials range from 0.003 to 1.5 V vs. Li+/Li). A higher reversible capacity of 400 mAh/g could be obtained for the macroporous sample using a discharge with plating of Li as described in [4], but this method could not be accepted in the case of Lithium-ion batteries. These first results show that carbon xerogels are very promising candidates as anode materials for Li batteries, providing the textural characteristics are carefully controlled. The ongoing work is dealing with the establishment of possible relationships between textural features and electrochemical performance in order to shed light on the requirements that will dictate the best synthesis procedures. References: [1] T. Tran, B. Yebka, X. Song, G. Nazri, K. Kinoshita and D. Curtis, J. Power Sources, 85, 269, 2000. [2] N. Job, A. Théry, R. Pirard, J. Marien, L. Kocon, J.-N. Rouzaud, F. Béguin and J.-P. Pirard, Carbon 43, 2481, 2005. [3] F. Cheng, Z. Tao, J. Liang, and J. Chen, Chem. Mater., 20, 667, 2008. [4] W. Xing, J. S. Xue, J.R. Dahn, J. Electrochem. Soc, 143, 3046, 1996. [less ▲]

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See detailSynthesis and characterization of porous carbon xerogels and ordered mesoporous carbons for anode materials in Li-based batteries
Léonard, Alexandre ULg; Pirard, Jean-Paul ULg; Job, Nathalie ULg

in Fagadar-Cosma, Eugenia (Ed.) Insights into novel solid materials, their recyclability and integration into Li polymer batteries for EVs. Future research directions in this field.:Book of abstracts (2012, July 04)

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See detailResorcinol-formaldehyde carbon xerogels as lithium-ion battery anode materials: influence of porosity on capacity and cycling behaviour
Léonard, Alexandre ULg; Piedboeuf, Marie-Laure ULg; Khomenko, Volodymyr et al

in Fagadar-Cosma, Eugenia (Ed.) Insights into novel solid materials, their recyclability and integration into Li polymer batteries for EVs. Future research directions in this field.:Book of abstracts (2012, July)

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See detailLife cycle assessment of carbon xerogels
Melon, Raphaëlle ULg; Renzoni, Roberto ULg; Léonard, Alexandre ULg et al

in Fagadar-Cosma, Eugenia (Ed.) Book of abstracts - Advanced Workshop - Insights into novel solid materials, their recyclability and integration into Li polymer batteries for EVs (2012, July)

In the framework of the SOMABAT European project, a life cycle assessment applied to the production of 1 kg of carbon xerogels was carried out by comparing three drying technologies (vacuum, microwave and ... [more ▼]

In the framework of the SOMABAT European project, a life cycle assessment applied to the production of 1 kg of carbon xerogels was carried out by comparing three drying technologies (vacuum, microwave and convective drying). These carbon materials with controlled texture are thought to be used as active material at the anode side of Li-polymer battery. [less ▲]

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See detailUse of glycosurfactants for the synthesis of polyHIPES in supercritical carbon dioxide
Boyère, Cédric ULg; Favrelle, Audrey; Léonard, Alexandre ULg et al

Poster (2012, June 04)

The abstract is available as a pdf file.

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See detailResorcinol-formaldehyde carbon xerogels as lithium-ion battery anode materials: influence of porosity on capacity and cycling behaviour
Léonard, Alexandre ULg; Piedboeuf, Marie-Laure ULg; Khomenko, Volodymyr et al

in Proceedings of the International Carbon Conference 2012 (2012)

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See detailPréparation, caractérisation et réactivité de l'acide 1-vanado-11-molybdo-phosphorique supporté sur des matériaux silicatés mésoporeux dans l'oxydation du propène
Benadji, S.; Eloy, P.; Léonard, Alexandre ULg et al

in Comptes Rendus Chimie (2012), 15(8), 658-668

The H 4PMo 11VO 40 heteropolyacid (HPA) was supported at 30 wt.% by the dry impregnation method on HMS, CMI-1 and SBA-15 mesoporous materials. The state of the HPA and those of the supports were examined ... [more ▼]

The H 4PMo 11VO 40 heteropolyacid (HPA) was supported at 30 wt.% by the dry impregnation method on HMS, CMI-1 and SBA-15 mesoporous materials. The state of the HPA and those of the supports were examined by nitrogen physisorption, X-ray diffraction, (DR) FT-IR and X-ray photoelectron spectroscopies, thermal analysis (TG-ATD) and scanning electron microscopy (SEM). The effect of support on the catalytic behavior of H 4PMo 11VO 40 was studied in the propene oxidation at 350 °C. It was shown that the presence of H 4PMo 11VO 40, modifies the textural properties of mesoporous materials (decrease of surface area) without destroying their structure. The interaction support-heteropolyacid leads to the formation of (SiOH 2+)(H 3PMo 11VO 40 -) surface species more stable than H 4PMo 11VO 40 species and that appear to be the active sites in the propene oxidation. © 2012 Published by Elsevier Masson SAS on behalf of Academie des sciences. [less ▲]

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See detailCharacterization of H3+xPMo12 xVxO40 heteropolyacids supported on HMS mesoporous molecular sieve and their catalytic performance in propene oxidation
Benadji, Siham; Eloy, Pierre; Léonard, Alexandre ULg et al

in Microporous & Mesoporous Materials (2012), 154

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See detailLife cycle assessment of carbon xerogels
Melon, Raphaëlle ULg; Renzoni, Roberto ULg; Léonard, Alexandre ULg et al

Poster (2011, November 03)

Detailed reference viewed: 18 (6 ULg)