R. Denoyel

Aix-Marseille Université, Marsiglia, Provence-Alpes-Côte d'Azur, France

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Publications (79)176.67 Total impact

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    ABSTRACT: Nanostructured block copolymer electrolytes (BCE) are currently attracting widespread interest for applications in rechargeable lithium batteries. In order to investigate the influence of the composition, and therefore that of confinement, on the conductivity, a series of triblock PS! PEO!PS copolymers, with three linear PEO blocks of molecular weights 9, 10, or 35 kg mol!1 and with PEO weight fractions varying from 36% to 75%, were synthesized and doped with LiTFSI. Measurements by impedance spectroscopy of the conductivity show that it increases with PEO molecular weight, which is quite counterintuitive. To explain this phenomenon, the conductivity of the BCE has been modeled using three factors: (1) the conductivity of bulk PEO, (2) the topology of the PEO percolating network, described by the tortuosity parameter, and (3) the influence on the tortuosity of the effective volume fraction of the PEO phase useful for the conduction, taking into account a “dead zone” excluded from ionic transport, at the PS/PEO interface. In this approach, by analogy with porous materials and in contrast with previous work, the tortuosity is not kept constant but depends on the PEO volume fraction effectively useful for charge transport. The thickness of the dead zone, 4!5 EO units (#1.6 nm), is the same as that of the exclusion zone for crystallization previously reported. This value does not depend either on the PEO molecular weight (from 9 to 35 kg mol!1) or on the EO/Li ratio (from 20 to 30). The absence of both conduction and crystallization in the excluded region could be due to the low mobility of the PEO chains in this zone. Consequently, the conductivity of BCE increases with PEO molecular weight because the proportion of the excluded zone becomes smaller as the PEO molecular weight increases. This model therefore provides a fairly precise description of the ionic conductivity of BCE used in lithium battery applications.
    Macromolecules 01/2014; 47. · 5.93 Impact Factor
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    ABSTRACT: High-energy ball-milling is proven to be an effective technique for manufacturing reactive aluminum nanopowders. The procedure of milling presented in this work allows the elaboration of aluminum powders with specific surface areas around 20 m2 /g. The particles have platelet morphology and are constituted by a nanocrystalline aluminum core surrounded by a thick amorphous alumina layer of 4.57 +-0.5 nm. The reactivity of the powders is enhanced as compared to nanopowders elaborated with techniques involving vapor phase condensation. The morphology, the microstructure and the initial thickness of the alumina layer are shown to be important parameters that influence the reactivity. The method could be extended to any other ductile metal, provided a hard surface layer is continuously formed during milling. & 2013 Elsevier B.V. All rights reserved.
    Materials Letters 11/2013; 110:108-110. · 2.27 Impact Factor
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    ABSTRACT: Interaction of CO2 with mineral surfaces is of increasing importance to the activities related to CO2 sequestration and enhanced oil recovery. Adsorption/interaction of CO2 with mineral powder surfaces is addressed using microcalorimetric method coupled with gas chromatograph as a detector. Calcite powder surface is modified with stearic acid (SA) and asphaltene, while the silicate mineral powder surfaces (quartz and kaolinite) are modified with N,N-dimethyldodecylamine (NN-DMDA) and asphaltene. Unmodified calcite in presence of humidity has shown to have the highest capacity for CO2 adsorption among the tested minerals, where a reaction may occur at the calcite surface. The adsorption capacity of calcite is reduced upon modification with SA and asphaltene. Similar observation is also shown with the modified silicate minerals with asphaltene. In contrast, for the modified silicate with NN-DMDA, the adsorption capacity of CO2 increased, which may be explained by the interaction of CO2 with the amine group of NN-DMDA.
    Petroleum Science and Technology 08/2013; 31(15). · 0.30 Impact Factor
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    ABSTRACT: The adsorption efficacy of 16 pharmaceuticals on six different activated carbons is correlated to the thermodynamic work of adhesion, which was derived following the surface tension component approach. Immersion calorimetry was used to determine the surface tension components of activated carbon, while contact angle measurements on compressed plates were used to determine these for solutes. We found that the acid–base surface tension components of activated carbon correlated to the activated carbon oxygen content. Solute-water interaction correlated well to their solubility, although four solutes deviated from the trend. In the interaction between solute and activated carbon, van der Waals interactions were dominant and explained 65–94% of the total interaction energy, depending on the hydrophobicity of the activated carbon and solute. A reasonable relationship (r2 > 70) was found between the calculated work of adhesion and the experimentally determined activated carbon loading.
    Carbon 03/2013; · 6.16 Impact Factor
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    ABSTRACT: The removal of uremic toxins by zeolites is investigated in the context of the exploration of alternative methods to blood purification by dialysis. The case of a partially protein bound molecule, p-cresol, is studied here. High silica MFI type zeolites show a selective adsorption for p-cresol without major ion exchange with the cations present under equilibrium conditions in solution. Adsorption isotherms in different media were performed: pure water, artificial blood serum containing bovine serum albumin and human serum (HS obtained from a pool of 50 dialysis patients). p-Cresol elimination levels of 80-85% were obtained under in vitro conditions. However, in HS, p-cresol affinities for the zeolites are generally reduced as compared with pure water due to a partial obstruction of the pore system by adsorption of proteins on the external surface of zeolites particles. These results show that zeolites can be successfully employed as specific adsorbents for uremic toxins but without direct contact with serum albumin, which means only in the ultra-filtrate. (C) 2011 Elsevier Inc. All rights reserved.
    Microporous and Mesoporous Materials 05/2012; 153:288-293. · 3.37 Impact Factor
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    ABSTRACT: Electromigration of ions through porous silica particles dispersed in an electrolyte is studied by conductivity measurements. By determining the suspension conductivity at infinite dilution of particles where the Maxwell equation is applicable, the conductivity of the particles is determined. At high ionic strength, this allows calculation of the tortuosity of the particles. The tortuosity is then used to extract the pore conductivity from the particle conductivity under low ionic strength conditions where the surface conductivity is not negligible. Evolution of pore conductivity, which appears to be related to pore size, is not monotonous when ionic strength increases, showing first a decrease at very low ionic strengths, i.e., in conditions of double layers overlap in the pores, followed by an increase to trend toward the bulk conductivity at high ionic strength. This unexpected behavior can be explained by the fact that the initial surface conductivity in pores is mainly due to the protons, provided by spontaneous dissociation of surface silanol sites in water, which are subsequently exchanged by sodium.
    The Journal of Physical Chemistry C 01/2012; 116:5090-5096. · 4.84 Impact Factor
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    ABSTRACT: The effects of SO42- and Mg2+ on the adsorption/displacement of stearic acid (SA), N,N-dimethyldodecylamine (NN-DMDA) and asphaltene, as oil soluble additives, onto or from calcite, quartz, and clay minerals are addressed in this paper. Thermal gravimetric analysis, isothermal water vapor adsorption, and contact angle methods are used to determine the extent of surface modification and evaluate the hydrophilicity/hydrophobicity of the modified powders and minerals, respectively. The experimental results of the modified mineral surfaces are analyzed using a suggested wettability index based on water vapor adsorption isotherm and contact angle. It is interesting to observe that SO42- and Mg2+ ions enhance hydrophilicity characteristic of the modified calcite surface while SO42- ions have insignificant effect on adsorption of the tested polar components on the silicate minerals. Mg2+ ions enhance the hydrophilicity of quartz and kaolinite surfaces modified by N,N-dimethyldodecylamine. On the other hand Mg2+ ions increase the hydrophobicity of silicate minerals when asphaltene is the surface modifying component. This may be due to bridging of the hydrated Mg2+ ions with asphaltene. The suggested bridging mechanism is also consistent in the case of alteration of calcite surface with asphaltene, however to lesser extent due to the more affinity toward calcite surfaces.
    Energy & Fuels 03/2011; 25(4). · 2.85 Impact Factor
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    ABSTRACT: The paper addresses wettability alteration of calcite, quartz and kaolinite powders, with stearic acid (SA), N,N-dimethyldodecylamine (NN-DMDA) and asphaltene as oil soluble additives. It is a challenge to convert silicate based mineral surfaces from strongly water-wet to more oil-wet. Thermogravimetric analysis (TGA) of the modified powders is used to quantify the monolayer adsorption and is suggesting the possible molecular orientation on the mineral surfaces. Characterization of the mineral surface hydrophilicity/hydrophobicity due to modification is determined by the enthalpy of the water vapor adsorption isotherm. From the quantity and the affinity to water vapor adsorption, a new wettability index is suggested. The enthalpy of water adsorption relative to liquefaction enthalpy shows that stearic acid and asphaltene deeply modify the calcite toward more oil-wet for treated humidified surfaces. It is interesting to observe that although the presence of a water film on quartz and kaolinite surfaces, enhance the adsorption of N,N-dimethyldodecylamine (NN-DMDA), does not eliminate but reduces the asphaltene adsorption.Graphical abstractMicrocalorimetry set up used for water vapor adsorption enthalpy to determine hydrophilicity/hydrophobicity of modified mineral surfaces.Highlights► Investigation of wettability alteration of different minerals, with SA, NN-DMDA and asphaltene. ► Investigation of the effect of water film on adsorption of SA, NN-DMDA and asphaltene over minerals. ► Developed an approach to determine the wettability index by water vapor adsorption isotherm. ► Estimation of possible molecular orientations of organic adsorbates on the mineral surfaces, interpreted from TGA data.
    Colloids and Surfaces A Physicochemical and Engineering Aspects 01/2011; 384:98-108. · 2.11 Impact Factor
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    ABSTRACT: Structural and chemical properties of aluminium powders with size distribution in the micrometer and nanometer range are studied. The particles can be described by an aluminium core surrounded with an alumina layer which, depending on the passivation method, can be amorphous or constituted with small crystallites of γ-alumina. Using calorimetric measurements and in situ neutron diffraction experiments, the crystallization of the amorphous shell is evidenced and a tetragonal structure for the crystallized γ-alumina is proposed. The thermal expansion of the aluminium core is obtained by following the variation of the cell parameter with temperature. It is shown that, whatever is the size of particles, the thermal expansion of the metallic core is not affected by an alumina shell with a 3 ± 2 nm thickness. In contrast, when the thickness of the crystalline alumina shell exceeds 20 nm, strong strain effects are evidenced.
    Acta Materialia. 01/2010; 58(12):4224-4232.
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    ABSTRACT: We have studied the chemical composition, the surface chemistry and the pore structure of holm-oak chars and eucalyptus chars prepared at final heating temperature in the range of 250–1000 °C from two commercial wood charcoals. Our study also includes adsorption–desorption of water vapour at 25 °C on the resulting chars. The samples were characterised by chemical analyses, Fourier transform infrared spectroscopy, adsorption (carbon dioxide, 273 K), mercury porosimetry and scanning electron microscopy. The Dubinin–Serpinsky equation (DS-2) and the Dubinin–Astakhov (DA) equation were applied to analyse the water adsorption data. The final heating temperature affects the chemical composition, the surface chemistry and the pore structure of each char series differently; the differences are of less significance at the highest temperature. The adsorption–desorption of water vapour at 25 °C reflects well the changes produced in the chars; the adsorption occurs in the micropores, and in the non-micropore structure at relative pressures higher than 0.95. The shape of the adsorption isotherms is largely dependent on the microporosity; it changes gradually from type II to type V for the chars with poorly developed microporosity (holm-oak chars), and it is more of type V for the chars with highly developed microporosity (eucalyptus chars). The DS-2 equation fails if type V is less defined, while the DA equation is always applicable and provides micropore volumes close to those determined at p/p0 = 0.95. Hysteresis is always observed; chemisorption occurs: the desorption line begins at saturation pressure and in general tends to meet near zero relative pressures.
    Journal of Analytical and Applied Pyrolysis 01/2010; 88(2):124-133. · 2.56 Impact Factor
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    ABSTRACT: A set of chromatographic materials for bioseparation were characterised by various methods. Both commercial materials and new supports presenting various levels of rigidity were analysed. The methods included size-exclusion and capillary phenomena based techniques. Both batch exclusion and inverse size-exclusion chromatography were used. Gas adsorption, mercury porosimetry and thermoporometry were applied as well as a new method based on water desorption starting from the saturated state. When the rigidity of adsorbents is high enough, the agreement is reasonable between the values of the structural parameters that were determined (surface area, porosity, and pore size) by various methods. Nevertheless, a part of macroporosity may not be evidenced by inverse size-exclusion chromatography whereas it is visible by batch exclusion and the other methods. When the rigidity decreases, for example with soft swelling gels, where standard nitrogen adsorption or mercury porosimetry are no more reliable, two main situations are encountered: either the methods based on capillary phenomena (thermoporometry or water desorption) overestimate the pore size with an amplitude that depends on the method, or in some cases it is possible to distinguish water involved in the swelling of pore walls from that involved in pore filling by capillary condensation.
    Journal of Chromatography A 09/2009; 1216(41):6906-16. · 4.61 Impact Factor
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    ABSTRACT: The quantitative characterization of pore structure of Sartobind Q, a strongly basic membrane anion exchanger that is formed by cross-linked cellulose support and a hydrogel layer on its pore surface, was made combining the results obtained by several experimental techniques: liquid impregnation, batch size-exclusion, inverse size-exclusion chromatography, and permeability. Mercury intrusion and nitrogen sorption porosimetry were carried out for a dry cellulose support membrane in order to get additional information for building a model of the bimodal pore structure. The model incorporated the distribution of the total pore volume between transport and gel-layer pores and the partitioning of solutes of different molecular weights was expressed through the cylindrical pore model for the transport pores and random plane model for the gel layer. The effect of composition of liquid phase on the pore structure was investigated in redistilled water, phosphate and Tris–HCl buffers containing up to 1 M NaCl. Evident differences in the bimodal pore structure were observed here when both the specific volume and size of the hydrogel layer pores significantly decreased with the ionic strength of liquid phase.
    Journal of Chromatography A 01/2009; · 4.61 Impact Factor
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    ABSTRACT: Nitrogen and carbon dioxide adsorption experiments have been used to investigate the porosity of carbon deposits formed in the Tore Supra tokamak as a consequence of the erosion of the plasma-facing components. We compare BET, αs-, and Dubinin–Raduskevich methods to distinguish between micropore volume (∼0.04 cm3 g−1) and external surface (∼90 m2 g−1). Consistent results have been obtained for nitrogen and carbon dioxide, and the smallest pores are shown to be reversibly closed and opened under air exposure and outgassing at 600 °C, respectively, probably due to blocking of pore entrances by surface oxides. Pore size distribution is calculated using the non-local density functional theory: a novel and straightforward method is used to fit the experimental isotherms by Lorentzian distributions of pores centered in some relevant pore size regions. We thus show that the tokamak sample micropores are mainly ultra-micropores (∼75%) whose widths are centered at 0.6 nm. This latter result is in good qualitative agreement with the outgassing effect and in good quantitative agreement with what is deduced from αs-plot.
    Carbon 01/2009; 47(1):109-116. · 6.16 Impact Factor
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    ABSTRACT: This work aims both to use and to improve our understanding of Nâ and Ar adsorption on a charcoal during its activation. For this purpose, a number of comparisons are carried out, which involve (i) four charcoals at various extents of activation, (ii) two adsorptives (Nâ and Ar), (iii) two methods for analyzing the adsorption isotherms (α{sub s} and Dubinin-Radushkevich), (iv) two adsorption techniques (volumetry and microcalorimetry), and (v) two liquids for immersion microcalorimetry (water and methanol). The question of the reference adsorbent needed for the application of the α{sub s} method is attentively examined. Concerning the microporous volumes involved, the results of the α{sub s} method are consistent with those derived from adsorption microcalorimetry.
    Langmuir 01/2009; 5(5):1205-1210. · 4.38 Impact Factor
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    ABSTRACT: Impregnation of a drug model (α-tocopheryl acetate) into mesoporous host matrices has been carried out using supercritical carbon dioxide (SC CO2) as impregnation solvent at 15MPa and 313K with a flow rate of 500gh−1. The operating conditions were defined following the solute concentration in the fluid phase as a function of pressure and carbon dioxide flow rate. Solubility measurements of α-tocopheryl acetate were first performed at 313K for pressures ranging 10–20MPa. High values of solubility in SC CO2 were measured: 6wt% at 10MPa and 14wt% at 20MPa. Measurements of the concentration of the solute in SC CO2 in the experimental conditions of impregnation in dynamic mode showed than it was ten times lower than the solubility. The variations of this concentration have been studied at 313K, for a pressure varying from 8 to 15MPa, and for a carbon dioxide flow rate varying from 120 to 600gh−1. Two different host matrices were used: a commercial chromatographic silica support and a MCM-41-type mesoporous organized silica synthetized at the laboratory. This latter showed the best drug loading of 1.14g per gram of adsorbent. The drug loadings obtained in supercritical media were similar to the ones obtained in liquid media using hexane as impregnation solvent. Nevertheless, the maximum loading was obtained after 1h of impregnation in SC media while 4h were needed in liquid media.
    Journal of Supercritical Fluids - J SUPERCRIT FLUID. 01/2009; 51(2):278-286.
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    ABSTRACT: Mechanical properties (elastic modulus, ultimate strength, and elongation at rupture), water sorption isotherms, and chemical diffusion coefficients of water are reported for composite polymers made from a majority polymer (93 wt %), sulfonated (DS = 0.9) poly-ether-ether-ketone (S-PEEK), and a minority polymer (7 wt %), sulfonated (DS = 2) and/or silylated poly-phenyl-sulfone (PPSU). S-PEEK is responsible for proton conductivity of the membranes, whereas the minority component is added to maintain the mechanical and morphological stability. It is shown that the addition of sulfonated PPSU reduces the mechanical strength and leads to important membrane swelling. In contrast, addition of silylated PPSU highly improves the membrane strength and reduces considerably membrane swelling, indicating a suitable strategy to improve polymer electrolytes for PEM fuel cells. The calculated water uptake coefficients and diffusion coefficients are consistent with those of other members of the S-PEEK polymer family.
    Chemistry of Materials - CHEM MATER. 06/2008; 20(13).
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    ABSTRACT: We have analyzed the mechanism of melting of molecular layers adsorbed in porous materials with cylindrical pores and rough pore walls. The working example studied here is a monolayer of methane molecules adsorbed in MCM-41 pore of diameter 2R=4 nm. Both experimental (neutron scattering) and simulation (Monte Carlo) results demonstrate the strong influence of the wall roughness on the melting mechanism. In particular, the transformation between solidlike and liquidlike monolayer phases adsorbed on a rough surface is observed over a broad temperature range, and solidlike properties persist even above the bulk methane melting temperature.
    The Journal of Chemical Physics 06/2008; 128(18):184703. · 3.12 Impact Factor
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    ABSTRACT: Thermoporometry, a calorimetric technique, has been applied on solid montmorillonite samples at variable relative humidity (RH) and brings novel information on the swelling mechanism of Na-montmorillonite. Some mesopores are already filled with water in conditions where the interlamellar space is only occupied by one layer of water molecules. It was also shown that inter-particles osmotic swelling in the mesoporous range begins at a lower RH than in the interlamellar space (54% and 80%, respectively) and present a large range of expansion (from 2.25 nm to 4.00 nm in the investigated RH domain). This inter-particles swelling plays therefore a dominant role in the overall swelling process in a broad range of RH values. Combining thermoporometry with XRD results, the results were integrated in a complete hydration sequence for Na-montmorillonite.
    Applied Clay Science 05/2008; 39:186-201. · 2.34 Impact Factor
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    ABSTRACT: Adsorption properties of zeolites were investigated for the removal of p-cresol from aqueous solutions at 37 °C within the context of studying alternative methods to dialysis for removing uremic toxin from blood. MFI-framework type zeolites with different degrees of hydrophobicity and charge compensating cations were prepared: one pure silica MFI and four alumino-silicate MFIs (Si/Al = 30), with H+, Na+, K+ and Mg2+ as charge compensating cations. Adsorption isotherms and microcalorimetric measurements show a high affinity of p-cresol for all MFI type zeolites. The best capacity is obtained for the pure silica MFI, whereas the alumino-silicate samples show a higher affinity in the low concentration range. In the case of pure silica sample, the microscopic adsorption mechanism including the role of confined water is elucidated with the help of NMR, X-ray analysis (including Rietveld refinement) and Monte Carlo simulations. For all samples the high affinity is preserved in physiological serum solution, even in the presence of other toxin molecules such as urea. It is also shown that the compensating cation state of the samples is imposed by the physiological medium.
    Adsorption 01/2008; 14(2):377-387. · 1.55 Impact Factor
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    M Barrande, R Bouchet, R Denoyel
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    ABSTRACT: Tortuosity is often used as an adjustable parameter in models of transfer properties through porous media. This parameter, not reducible to classical measured microstructural parameters like specific surface area, porosity, or pore size distribution, reflects the efficiency of percolation paths, which is linked to the topology of the material. The measurement of the effective conductivity of a bed of particles saturated with an electrolyte is a simple way to evaluate tortuosity. Nevertheless, it received only little attention because of the real difficulties in both getting reliable results and interpreting data. Notably, the discrimination between the contribution of interparticle and intraparticle porosities to the tortuosity is not resolved. To our knowledge, there is no model able to fit the experimental data of the tortuosity of a suspension, and a fortiori of a particle bed, in the whole porosity range. Only empirical expressions have been proposed, but they do not allow deriving intratortuosity of a porous particle. For a dilute system, Maxwell's equation predicts the effective conductivity of suspensions of spherical particles as a function of the bulk electrolyte conductivity and of particle conductivity. The intraparticle tortuosity can be derived from the particle conductivity obtained from the Maxwell equation applied to data at infinite dilution of particles. Then, by assuming that the Maxwell equation is a first-order approximation of the conductivity as a function of porosity, we propose an explicit relation of the tortuosity tau of a suspension of porous particles, obtained by conductivity measurement, as tau = tau(epsilon, epsilon(p), tau(p)), where epsilon is the total porosity of the suspension, tau(p) is the intraparticle tortuosity, and epsilon(p) is the particle porosity. This relationship fits the experimental data in the whole porosity range and can be used to determine tau(p) from an experiment at only one porosity. Finally, the obtained values of tau(p) for a set of porous particles used in chromatography are discussed and compared to the data available in the literature.
    Analytical Chemistry 01/2008; 79(23):9115-21. · 5.82 Impact Factor

Publication Stats

448 Citations
176.67 Total Impact Points

Institutions

  • 2009–2012
    • Aix-Marseille Université
      • Faculté de Pharmacie
      Marsiglia, Provence-Alpes-Côte d'Azur, France
  • 2007
    • Université Paul Cézanne
      Aix, Provence-Alpes-Côte d'Azur, France
  • 2004
    • Université de Montpellier 1
      Montpelhièr, Languedoc-Roussillon, France
  • 2002
    • Spanish National Research Council
      Madrid, Madrid, Spain
  • 1999–2000
    • French National Centre for Scientific Research
      Lutetia Parisorum, Île-de-France, France