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Baddour-Hadjean R.,CNRS East Paris Institute of Chemistry and Materials Science | Pereira-Ramos J.-P.,CNRS East Paris Institute of Chemistry and Materials Science | Pereira-Ramos J.-P.,CNRS Institute of Chemistry
Chemical Reviews | Year: 2010

Raman spectroscopy can be used for better understanding of the relationship between the structure and electrochemistry of electrode materials for lithium batteries. Most of the electrode materials, including carbonaceous compounds, transition metal oxides, and phospho-olivines, are Raman active compounds. Raman spectroscopy constitutes a very pertinent local tool to enrich the knowledge of the structure of Li intercalation compounds at the scale of interatomic bonds by providing information regarding local disorder, changes in bond lengths, bond angles, coordination, Li dynamics, metal oxidation state, and cation ordering. New and pertinent data allowing the identification of the local processes that contribute to the mechanism of Li- battery degradation on cycling or aging have been obtained from the great possibilities offered by the confocal Raman imaging technique. The ultimate step for a significantly improved and wider application of Raman microspectrometry will consist in systematically combining a rigorous experimental approach with appropriate lattice dynamics simulations.

Huot J.,University of Quebec at Trois - Rivieres | Ravnsbaek D.B.,University of Aarhus | Zhang J.,CNRS East Paris Institute of Chemistry and Materials Science | Cuevas F.,CNRS East Paris Institute of Chemistry and Materials Science | And 2 more authors.
Progress in Materials Science | Year: 2013

New synthesis methods are of utmost importance for most materials science research fields. The present review focuses on mechanochemical synthesis methods for solid hydrogen storage. We anticipate that the general methods and techniques are valuable with a range of other research fields, e.g. the rapidly expanding fields of 'energy materials science' and 'green chemistry' including solvent free synthesis. This review starts with a short historical reminder on mechanochemistry, followed by a general description of the experimental methods. The use of milling tools for tuning the microstructure of metals to modify their hydrogenation properties is discussed. A section is devoted to the direct synthesis of hydrogen storage materials by solid/gas reactions, i.e. by reactive ball milling of metallic constituents in hydrogen, diborane or ammonia atmosphere. Then, solid/solid mechano-chemical synthesis of hydrogen storage materials with a particular attention to alanates and borohydrides is surveyed. Finally, more specialised techniques such as solid/liquid based methods are mentioned along with the common characteristics of mechanochemistry as a way of synthesizing hydrogen storage materials. © 2012 Elsevier Ltd. All rights reserved.

Goncalves A.P.,University of Lisbon | Godart C.,CNRS East Paris Institute of Chemistry and Materials Science
European Physical Journal B | Year: 2014

The need of alternative "green" energy sources has recently renewed the interest in thermoelectric (TE) materials, which can directly convert heat to electricity or, conversely, electric current to cooling. The thermoelectric performance of a material can be estimated by the so-called figure of merit, zT = σ α 2 T/λ (α the Seebeck coefficient, σ α 2 the power factor, σ and λ the electrical and thermal conductivity, respectively), that depends only on the material. In the middle 1990s the "phonon glass and electron crystal" concept was developed, which, together with a better understanding of the parameters that affect zT and the use of new synthesis methods and characterization techniques, has led to the discovery of improved bulk thermoelectric materials that start being implemented in applications. During last decades, special focus has been made on skutterudites, clathrates, half-Heusler alloys, Si1-x Ge x-, Bi2Te 3- and PbTe-based materials. However, many other materials, in particular based on intermetallics, pnictides, chalcogenides, oxides, etc. are now emerging as potential advanced bulk thermoelectrics. Herein we discuss the current understanding in this field, with special emphasis on the strategies to reduce the lattice part of the thermal conductivity and maximize the power factor, and review those new potential thermoelectric bulk materials, in particular based on intermetallics, pnictides and chalcogenides. A final chapter, discussing different shaping techniques leading to bulk materials (eventually from nanostructured TE materials), is also included. © 2014 EDP Sciences, SIF, Springer-Verlag Berlin Heidelberg.

Wildman E.J.,University of Aberdeen | Skakle J.M.S.,University of Aberdeen | Emery N.,CNRS East Paris Institute of Chemistry and Materials Science | McLaughlin A.C.,University of Aberdeen
Journal of the American Chemical Society | Year: 2012

Colossal magnetoresistance is a rare phenomenon in which the electronic resistivity of a material can be decreased by orders of magnitude upon application of a magnetic field. Such an effect could be the basis of the next generation of memory devices. Here we report CMR in the antiferromagnetic oxypnictide NdMnAsO 1-xF x as a result of competition between an antiferromagnetic insulating phase and a paramagnetic semiconductor upon application of a magnetic field. Mn 2+ oxypnictides are relatively unexplored, and tailored synthesis of novel compounds could result in an array of materials for further investigation and optimization. © 2012 American Chemical Society.

Zlotea C.,CNRS East Paris Institute of Chemistry and Materials Science | Latroche M.,CNRS East Paris Institute of Chemistry and Materials Science
Colloids and Surfaces A: Physicochemical and Engineering Aspects | Year: 2013

This review highlights a new emerging route towards improving the properties of solid-state hydrogen storage materials, the nanoconfinement of metallic particles into scaffolds. The nanostructure design enables tailoring the hydrogen sorption properties, both kinetics and thermodynamics. Among several nanostructure design approaches, the nanoconfinement of metal particles into scaffolds has the advantage of preventing coalescence and easy handling of nanoparticles. Hydrogen sorption properties of hybrids containing metallic nanoparticles and nanoalloys embedded into different scaffolds will be discussed here. Two classes of metallic nanoparticles will be addressed: noble metal-based nanoparticles and Mg-based nanospecies. © 2012 Elsevier B.V.

Cuevas F.,CNRS East Paris Institute of Chemistry and Materials Science | Korablov D.,CNRS East Paris Institute of Chemistry and Materials Science | Latroche M.,CNRS East Paris Institute of Chemistry and Materials Science
Physical Chemistry Chemical Physics | Year: 2012

MgH2-TiH2 nanocomposites have been obtained by reactive ball milling of elemental powders under 8 MPa of hydrogen pressure. The composites consist of a mixture of β-rutile MgH2, γ-orthorhombic high pressure MgH2 and ε-tetragonal TiH2 phases with nanosized crystallites ranging from 4 to 12 nm. In situ hydrogen absorption curves on milling reveal that nanocomposite formation occurs in less than 50 min through the consecutive synthesis of the TiH 2 and MgH2 phases. The abrasive and catalytic properties of TiH2 speed up the formation of the MgH2 phase. Thermodynamic, kinetic and cycling hydrogenation properties have been determined for the 0.7MgH2-0.3TiH2 composite and compared to nanometric MgH2. Only the MgH2 phase desorbs hydrogen reversibly at moderate temperature (523 to 598 K) and pressure (10-3 to 1 MPa). The presence of TiH2 does not modify the thermodynamic properties of the Mg/MgH2 system. However, the MgH 2-TiH2 nanocomposite exhibits outstanding kinetic properties and cycling stability. At 573 K, H-sorption takes place in less than 100 s. This is 20 times faster than for a pure nanometric MgH2 powder. We demonstrate that the TiH2 phase inhibits grain coarsening of Mg, which allows extended nucleation of the MgH2 phase in Mg nanoparticles before a continuous and blocking MgH2 hydride layer is formed. The low crystallinity of the TiH2 phase and its hydrogenation properties are also compatible with a gateway mechanism for hydrogen transfer from the gas phase to Mg. Mg-rich MgH2-TiH2 nanocomposites are an excellent media for hydrogen storage at moderate temperatures. This journal is © the Owner Societies.

Joubert J.-M.,CNRS East Paris Institute of Chemistry and Materials Science
International Journal of Hydrogen Energy | Year: 2010

A new equation of state for hydrogen gas (0 ≤ P ≤ 1011 Pa, 298 ≤ T ≤ 1000 K) has been derived and is given in an analytical form. It is compatible with the Calphad approach (i.e. it is an analytical equation of the Gibbs energy as a function of pressure). This equation has been applied to the Calphad assessment of the H-Rh system, an example of system forming a metal hydride only at a very high pressure. A set of self-consistent thermodynamic parameters describing the Gibbs energy of each phase has been obtained. The scarce experimental data available for this system, particularly the high formation pressure of the hydride, have been well reproduced which otherwise would have been impossible without considering the non-ideal behaviour of the gas phase. © 2010 Professor T. Nejat Veziroglu.

Joubert J.-M.,CNRS East Paris Institute of Chemistry and Materials Science
JOM | Year: 2012

A review of the metal-hydrogen systems modeled or investigated with the CALPHAD method is presented. The specific features of metal-hydrogen systems in relation with the CALPHAD modeling are detailed, and the problems and needs related to the description of such systems are highlighted. © 2012 TMS.

Bensemhoun J.,CNRS East Paris Institute of Chemistry and Materials Science | Condon S.,CNRS East Paris Institute of Chemistry and Materials Science
Green Chemistry | Year: 2012

Conjugate addition reactions are efficiently performed by a very simple electrochemical method using nickel complexes as catalysts. In this paper, we reported a new method for the valorization of glycerol 1,2-carbonate. Firstly, we prepared the activated glycerol 1,2-carbonate derivatives (halogen or pseudo-halide derivatives), and secondly applied these halogen derivatives in coupling reactions by electrochemical methods with organic compounds and environment-friendly solvent (propylene carbonate). To our knowledge, this is the first report of creation of carbon-carbon bonds on the glycerol 1,2-carbonate and of the synthesis of these compounds. © 2012 The Royal Society of Chemistry.

Champion Y.,CNRS East Paris Institute of Chemistry and Materials Science
Materials Science and Engineering A | Year: 2013

Low temperature (77K, 243K and 255K) mechanical tests were carried out at strain rates between 7.10 -4s -1 and 5.10 -2s -1 on pure ultrafine grained (UFG) copper (grain size 100nm) to mimick room temperature high strain rates. Variation of the activation volume measured as a function of the stress is consistent with the analytical model proposed in [C. Duhamel, Y. Bréchet, Y. Champion Int. J. Plast. 26 (2010) 747-757] to explain the rheology of UFG metals. This model is based on dislocations interactions at grain boundaries and grain boundaries sliding. The experiments confirm that the strain rate sensitivity (which should be a criterion for plasticity in absence of macroscopic work hardening) increases with the strain rate (or stress) at high strain rate, as also observed for nanotwinned copper. From the model, a strain rate sensitivity criterion is derived, function of a characteristic UFG strength parameter and grain boundary properties. The analytical description of deformation of UFG including microstructural properties should help for a quantitative control of the macroscopic properties of UFG. © 2012 Elsevier B.V.

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