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Thème : Nanomatériaux fonctionnels
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Structuring of Self-Assembled Hybrid Silicas : Mechanistic Studies
Involved researchers : J-L. Bantignies, Ph. Dieudonné, C. Blanc, J-L. Sauvajol (Collaboration M. Wong Chi Man - ENSCM Montpellier, G. Creff - Synchrotron Soleil) This activity has been devoted to the understanding of the self-assembling mechanisms of organic-inorganic hybrid silicas obtained via sol-gel route. The molecular precursors consist of an inorganic substructure with triethoxysilyl groups associated to an organic substructure which provides the self-organization properties. The (...)
Phase transitions and pressure-induced amorphization of GeTe-Sb2Te3 compounds, which are used as phase-change optical memories (DVD)
Those materials are used as rewritable DVD due to their quick and reversible crystal/amorphous transition, under a laser pulse. We have demonstrated that pressure is an important A written bit (amorphous confined in a crystalline matrix within a rigid structure) of a DVD is submitted to a pressure of a few GPa. Pressure is an important parameter to take into account in the writing process in DVDs, in addition to temperature whose influence is usually accounted. Pressure-induced amorphization is (...)
Density fluctuations in glasses, investigation through small angle X-ray scattering
The amplitude of density fluctuations in a glass strongly depends on its thermal history, a glass frozen at high temperature is significantly more disordered than a glass with the same composition and frozen at a lower temperature. These measurements also allow determining the compressibility in the glassy state. Temperature scanning small-angle X-ray scattering can also be used as a tool to characterize the glass transition in vitreous silica or binary SiO2-Al2O3 glasses (this technique offers an (...)
Origin of hypersonic sound wave attenuation in silica and porous silica (vycor, xérogels)
Evidence of a relaxation peak at low temperature due to impurities ; evidence of a geometric scattering contribution by disorder at the nanometer scale. Competition between anharmonicity and relaxations for the origin of hypersonic sound wave attenuation in glasses. Publications : C. Levelut and J. Pelous ,J. Phys. Cond. Matt., 19 (2007) 416110 J. Pelous and C.Levelut Phys. Rev. B, 72, issue 22, 224202 (2006). C. Levelut, R. Le Parc, and J. Pelous, Phys. Rev. B 73 052202 (2006) - (...)
Pressure-induced amorphisation of negative thermal expansion (NTE) compounds : cyanides and zéolites
Involved researchers : C.Levelut, J-L. Bantignies, collaboration ICG Those nanoporous materials exhibit the pressure-induced amorphization (PIA) phenomenon. Both phenomena, NTE and PIA, seem to be related Those materials are interesting for fundamental reasons (simultaneous study of structure and vibrations in order to understand PIA and NTE phenomena), but also for industrial applications (material with no thermal expansion or whose thermal expansion fit that of a substrate for example). We (...)
Modeling of optimal sorbents for hydrogen, natural gas and green house gases
Practical implementation of hydrogen fuel in automotive applications is still impeded by the lack of efficient, economical, light and save storage medium. Even the best candidates, nanoporous activated carbons, hardly meet the targets based on the requirement of 500 km vehicle autonomy and operating pressure below 100 bar at ambient temperatures. Although the specific surface area accessible for hydrogen may be considerably increased by adequate engineering of nanospace, the low heat of hydrogen (...)
Towards simulations of biological systems
The quality of the results of computer simulations of any real system depends on the quality of force fields of the theoretical model. This becomes critically important when modeling large systems of flexible molecules, such as polymers and biomolecules (especially proteins or lipids). In such systems, correlations between internal and external degrees of freedom determine the local conformational stability of molecules (i.e. folding). Conversely, the same correlations affect intermolecular (...)
New Bio-inspired Membrane made of a Biological Ion Channel confined into the Cylindrical Nanopore of a Solid-State Polymer
Recent advances in membrane sciences allow us the use of membranes in many fields such as food and agriculture, potable water production, industrial water treatment and biotechnology. Among the newly developed technologies, nanofiltration for liquids is the most recent one. One of the scientific challenges is to develop nanofilters with both high permeability and selectivity, which are often considered as antagonist features. Today, the number of solid state membranes that are readily useable is (...)
Ions and Molecules in Micro and Mesoporous Materials
Involved researchers : Lydie Berardo, François Henn, Vincent Jourdain, Mohamed Kharroubi Many micro and mesoporous materials possess internal surface partly covered with ions that neutralize the electrical charge born by the framework. It is well acknowledged that these ions play a key role on the material properties regarding, in particular, adsorption of liquids or gas, surface reactivity and ionic conductivity. These materials are therefore used in many applications : gas capture, liquid or gas (...)
Materials for Rechargeable Battery
Participants L2C : Laurent Alvarez, Jean-Louis Bantignies, Laure Gourrier , François Henn, Patrick Hermet, Thierry Michel et Matthieu Paillet Contrats : ANR ANZAS (programme Stock-E) 2009-2011. Partenaires industriels : SCPS, SAFT & Helion-AREVA Our research activity is mainly focussed on nickel hydroxide ( ). This material has been raising a considerable interest for decades since it is the active mass of the positive electrode of many commercial rechargeable batteries, e.g. Ni/Cd, Ni/MH or (...)
