Laboratoire des materiaux

Tunisia

Laboratoire des materiaux

Tunisia

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Muller O.,French German Research Institute of Saint Louis | Lutz Y.,French German Research Institute of Saint Louis | Teissier A.,French German Research Institute of Saint Louis | Teissier A.,Laboratoire des Materiaux | And 2 more authors.
Applied Optics | Year: 2010

The optical limiting behavior of multiwalled carbon nanotube (MWCNT) powder in chloroform solution under CO2 infrared laser irradiations is reported for, to our knowledge, the first time. Here we demonstrate the pure thermal origin of the optical limiting effect in the 160 ns time scale studied. The Z-scan technique appears to be an excellent tool for xperimental evaluation of the nonlinear refractive index. An experimental model for the optical limiting behavior of MWCNT suspensions in chloroform is presented. The occurrence of a laser-induced thermal lens through the absorption of energy by the MWCNTs and subsequent heat transfer to the solvent, followed by solvent vapur bubble growth, is the main factor governing the observed drop in transmittance. Pump-probe experiments have been performed to obtain some quantitative estimation of both the rise and decay times of the thermal lensing phenomenon. It was found that the early probe signal decay, t1 τ 149 ns, was of the same order of magnitude as the rise time of the thermal lens, τ 121 ns. When the nonlinear scattering was considered, a total decay time of τ 1:8 μs was obtained. A recovery time for the thermal lens of several tens of milliseconds has been experimentally determined, which is in good accordance with the theoretical value. © 2010 Optical Society of America.


Allouch A.,Laboratoire des Materiaux | Allouch A.,University of Strasbourg | Guglielmino M.,Laboratoire des Materiaux | Bernhardt P.,Laboratoire des Materiaux | And 2 more authors.
Sensors and Actuators, B: Chemical | Year: 2013

Formaldehyde is a colorless gas emitted into the indoor environment by furniture and many other sources. In 2006, International Agency for Research on Cancer (IARC) classified formaldehyde as carcinogen to humans even at low concentrations. The World Health Organization (WHO) determined a guideline value of 82 ppb (parts per billion). Standard analysis based on sampling and then gas chromatography (GC) or high-performance liquid chromatography (HPLC) methods are off-line methods and are considered to be time-consuming and cumbersome, in addition to their large sizes, weights, high cost in terms of both equipment and consumables. This review reports the developments made over the last decade toward the realization of portable, high sensitive and real-time formaldehyde analyzers. © 2013 Elsevier B.V.


Di Felice L.,Laboratoire des Materiaux | Di Felice L.,University of L'Aquila | Courson C.,Laboratoire des Materiaux | Foscolo P.U.,University of L'Aquila | Kiennemann A.,Laboratoire des Materiaux
International Journal of Hydrogen Energy | Year: 2011

The tar reforming catalytic activity of iron and nickel based catalysts supported on alkaline-earth oxides CaO, MgO and calcined dolomite [a (CaMg)O solid solution] has been investigated in a fixed bed reactor operating at temperatures ranging from 650 to 850 °C; toluene and 1-methyl naphthalene were used as model compounds for tar generated during biomass gasification. The CO2 absorption capacities of Fe/(CaMg)O and Ni/(CaMg)O were also investigated at the lower temperature condition (650 °C) at which the sorption process is thermodynamically favoured. It was found that iron and nickel may be optimised in the substrate particles to enhance both the catalytic activity and the carbon deposition resistance during catalytic tests, at the same time reducing critical limitations on CO2 capture capacity. © 2011, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.


Ayadi S.,Laboratoire des materiaux | Sliti S.,Laboratoire des materiaux | Abderrabba M.,Laboratoire des materiaux
Journal of Materials and Environmental Science | Year: 2014

In this work, we theoretically study the hydrogenation reaction of disubstituted cyclopentene 1a-d by the (Z)-1,2-diazene 2 and by (E)-1,2-diazene 2'. DFT/B3LYP calculations with 6-311G** standard basis set, explain the possibility and the stereoselectivity of these reactions. The transition states of the reaction between (Z)-1,2-diazene 2 and disubstituted cyclopentene 1a-d have been calculated and discussed.


Wust Zibetti A.,Federal University of Santa Catarina | Aydi A.,Laboratoire des Materiaux | Arauco Livia M.,Federal University of Santa Catarina | Bolzan A.,Federal University of Santa Catarina | Barth D.,CNRS Reactions and Process Engineering Laboratory
Journal of Supercritical Fluids | Year: 2013

Industry is increasingly interested in natural food preservatives, antimicrobial, and antioxidants due to their beneficial effects. The use of plant waste also presented itself to be a great opportunity in recovered bioactive compounds remaining in the residue. In this work, bioactive compounds were obtained from Rosmarinus officinalis in two different ways: firstly the supercritical fractionated rosemary extract with different composition was obtained from the plant material, and secondly a potent antioxidant-rosmarinic acid (RA) - was successfully extracted from the plant waste. A purification process scale-up of RA was proposed using GRAS solvent, and an economic evaluation was made for the overall process. A complete process to obtain bioactive compounds, antimicrobial (supercritical fluid extraction and fractionation extraction) and antioxidant (solvent extraction) was developed. © 2013 Elsevier B.V. All rights reserved.


Maia A.J.,Federal University of Rio de Janeiro | Louis B.,Laboratoire des Materiaux | Lam Y.L.,Petrobras | Pereira M.M.,Federal University of Rio de Janeiro
Journal of Catalysis | Year: 2010

Nickel was introduced in ZSM-5 zeolite by two different methods: dry impregnation and ionic exchange. Different loadings of metal, ranging from 0.4 to 6 wt% were explored. These materials were thoroughly characterized by EXAFS, TPR, acidity measurements by H/D isotope exchange and ethane hydrogenolysis. Regardless of the metal introduction method, at 0.4 wt% Ni, the Ni-ZSM-5 catalysts present only nickel located inside the zeolite channels as compensation cations. In contrast, an increase to 1 wt% nickel (via impregnation) led to its presence both inside and outside the channels. The catalytic activity of these Ni-ZSM-5 zeolites was tested in n-hexane cracking. Depending on the way the metal was introduced, it was possible to modify the n-hexane cracking activity and the selectivity toward light alkenes. Hence, a proper design of metal and acid sites could be achieved. © 2009 Elsevier Inc. All rights reserved.


Zaghouane-Boudiaf H.,Ferhat Abbas University Setif | Boutahala M.,Ferhat Abbas University Setif | Tiar C.,Ferhat Abbas University Setif | Arab L.,Ferhat Abbas University Setif | Garin F.,Laboratoire des Materiaux
Chemical Engineering Journal | Year: 2011

Clay-based adsorbents were synthesized by incorporating anionic surfactants sodium dodecylbenzenesulfonate (SDBS), into calcined magnesium aluminum layered double hydroxide (MgAl-C) via ion exchange. The sample has been characterized by powder X-ray diffraction, FT-IR spectroscopy and B.E.T measurement. The result shows that SDBS adsorption on the calcined phase is enhanced by reconstruction of a matrix hydrotalcite intercalated by the dodecylbenzenesulfonate with basal spacing of 30Å, which is larger than that of MgAl-CO3. The product which is an organophilic layered double hydroxide or organo-LDH (MgAl-SDBS) was examined for their ability to adsorb organic pollutant. The adsorption of 2,4,5-trichlorophenol (TCP) from aqueous solutions by MgAl-SDBS hydrotalcite was investigated in a batch mode. The influence of solution pH, initial TCP concentration and temperature has been tested in kinetic runs. The results showed that the kinetic adsorption could be described by a pseudo-second order model very well. The equilibrium isotherm for TCP uptake was fitted to the Langmuir model with correlation coefficient R2 of 0.998 at low concentrations and 0.992 for all concentrations. Its maximum adsorption amount is 240.5mg/g from this model, while the real amount is 160mg/g at 298K and pH 4. The negative value of ΔG° and the positive value of ΔH° indicate the spontaneous and endothermic nature of the process. © 2011 Elsevier B.V.


Petitjean M.,Laboratoire des Materiaux | Darvas M.,University of Franche Comte | Darvas M.,Eötvös Loránd University | Picaud S.,University of Franche Comte | And 3 more authors.
ChemPhysChem | Year: 2010

The adsorption of hydroxyacetone molecules at the surface of ice is investigated by means of flow-tube reactor measurements in the temperature range: 213-253 K. The number of molecules adsorbed per surface unit is conventionally plotted as a function of the absolute gas concentration of hydroxyacetone and is compared to that previously obtained for acetone and ethanol. The enthalpy of adsorption and the monolayer capacity at the ice surface are determined. In addition, molecular dynamics simulations are performed to support the experimental results. However, it is shown that the available interaction potential between hydroxyacetone and ice is not accurate enough to allow a robust detailed analysis of the adsorption process. Finally, a rapid estimation of the hydroxyacetone partitioning between the gas phase and ice shows that in the densest ice clouds, up to 29 % of hydroxyacetone could be adsorbed on pure ice surfaces at 203 K. © 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.


Ivanova S.,CSIC - Institute of Materials Science | Nitsch X.,Laboratoire des Materiaux | Romero-Sarria F.,CSIC - Institute of Materials Science | Louis B.,Laboratoire des Materiaux | And 3 more authors.
Catalysis Today | Year: 2011

We report herein the synthesis of an organic-inorganic hybrid composed by the ionic liquid protected Keggin structure, as a precursor for acid catalyst and its subsequent application in the methanol dehydration reaction. Special attention was paid to the thermal stability of the resulted hybrids as a function of the Keggin anion. The catalytic behaviour of these new materials are also studied and compared to the metal salt Cs2HPW 12O40. The prepared hybrids are less thermally stable than the metal salt, but their partial decomposition results in very active and selective catalysts for the dehydration of methanol to dimethyl ether. © 2011 Elsevier B.V. All rights reserved.


Moldovan M.S.,CNRS Institute of Genetics and of Molecular and Cellular Biology | Bulou H.,CNRS Institute of Genetics and of Molecular and Cellular Biology | Dappe Y.J.,French Atomic Energy Commission | Dappe Y.J.,CEA Saclay Nuclear Research Center | And 4 more authors.
Journal of Physical Chemistry C | Year: 2012

Controlling the size, dispersion, and shape of nanoparticles (NPs) in the high-temperature range is a key topic for the development of new technologies with applications in the particular fields of catalysis and energy storage. In this article, we present an approach combining in situ transmission electron microscopy (TEM), electron tomography (ET), and molecular dynamics (MD) calculations for assessing the evolution of Pt NPs deposited onto few-layer graphene supports. Spherical Pt NPs with average sizes of 2 nm located preferentially at the support topographical defects (e.g., steps and edges) diffuse and coalesce along these defects, such that, after annealing to 700 °C, the nanoparticles were located exclusively here. Their dispersion remained significant; only the particle size distribution changed from mono- to bimodal. This statistical variation is discussed herein by reviewing fundamental issues such as the NP-support interaction and NP faceting, diffusion, and subsequent sintering in the high-temperature range. Fundamental MD simulations are reported here as reinforcements of the experimental findings and as a means to provide deeper insight into the phenomenological issues behind the behavior of the system investigated. © 2012 American Chemical Society.

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