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International audience; We report here the successful design of 0–3 type nanocomposites where 30 nm ferromagnetic metallically conducting cores of manganite La0.66Sr0.34MnO3 (LSMO) are discretely distributed in an insulating silica matrix. Starting from LSMO@SiO2 core@shell nanoparticles, hydrothermal sintering process was used as a low temperature densification route (300 °C, 350 MPa, 90 min) in presence of 0.2 M aqueous sodium hydroxide solution. This process based on a pressure solution creep in the contact zones between nanoparticles allows the design of complex microstructures preventing the grain growth of the cores and the formation of interphases between the cores and the matrix.

International audience; Pure tysonite La0.95Ba0.05F2.95 is nanostructured by using the ball-milling technique. Size and pollution rate are minimized using the statistical method of Design of Experiment. The nanocrystalline powders are studied by X-ray and TEM analyses and by 19F solid state NMR and impedance spectroscopies. Specific surface area and F/OH substitution rate are estimated by BET measurements and thermal analysis (TGA-MS), respectively. Fluorine environments and mobilities are discussed on the basis of 19F solid state NMR data, both prior and after thermal treatment. The ionic conductivity, evaluated from sintered pellets, is compared at different thermal treatment temperatures. Thermal treatment tends to reduce microstrains up to 500 °C and to increase the grain size above this temperature. Optimal conductivity is obtained for a thermal treatment from 700 °C and no significant improvement of the conductivity by nanostructuration is observed.

International audience; Iron layers with variable thicknesses, deposited onto copper thin films, are oxidized by a plasma afterglow at atmospheric pressure. Such a bilayer arrangement enables the growth of caterpillar-like patterns covered by CuO and Fe2O3 nanostructures. Two main mechanisms are at stake: either copper comes up to the surface through cracks or boundaries between the columns of the coating, or it diffuses through parts of the Fe2O3 layer made permeable by tensile stress. Structures grown by the former mechanisms are characterized by a central channel, whereas those grown by the latter exhibit a plane interface above which stands an equiaxed grain heap. This result was used to localize the growth of nanowires in cracks formed priory to the afterglow-assisted treatment. By resorting to XPS microscopy experiments carried out with the scanning photoelectron microscope at the ESCAMicroscopy beamline of the Elettra synchrotron facility in Trieste, we could gain access to the surface composition of a single isolated pattern.

International audience; In this work, we produce bulk nanostructured Mg2Si0.4Sn0.6 thermoelectric materials made of nanograins with sizes below 200 nm and containing a fine distribution of Sn-rich nanoparticles. These materials are obtained by the mechanical alloying followed by spark plasma sintering. The microstructure and transport properties, and their evolutions upon aging, are investigated. A model is developed to capture the different contributions to the phonon scattering processes arising from the nano/microstructural parameters. The calculations show quantitative agreement with the temperature and the temporal dependence of the lattice thermal conductivity of the nanostructured Mg2Si0.4Sn0.6 alloy. This work provides a general analytic approach for identifying the individual contributions of the microstructural parameters on the thermal conductivity which is a very important property controlling the performance of thermoelectric materials.

The low vapor pressure of explosives makes the gaseous detection challenging and drives even the particle detection. There is a need to provide easy portable systems, highly spreadable. A bio-inspired concept was developed to detect explosive vapors with unprecedent sensitivities. Vertically aligned TiO2 nanotubes were grown on a cantilever. The sensors successfully detected trinitrotoluene (TNT) and pentaerythritol tetranitrate (PETN) with a minimum threshold concentration down to 0.8 ppt. This work describes also the investigations undertaken to develop the characterization of explosives by nanocalorimetry, which is able to identify explosives in form of single particles.

International audience; Poly[Styrene-b-Butadiene-b-(Methyl Methacrylate)], SBM triblock copolymers have been incorporated in different polyurethane, PU formulations in order to prepare nanostructured materials. Macrodiols used for PU synthesis were based on a central bis-phenol A, BPA unit with two hydroxyl-terminated oligo(oxypropylene), BPA-POx or oligo(oxyethylene), BPA-EO chains with varying lengths. The initial solubility of the three blocks and the rheological behavior of the solutions in macrodiols and also in two diisocyanates, isophorone diisocyanate, IPDI, and 1,3-xylylene diisocyanate, XDI have been first characterized. The PMMA block is the most soluble and its role during the reaction is to stabilize the initial nanostructure or to control the reaction-induced microphase separation. Block copolymers can be dissolved first in the macrodiol, or preferably in the diisocyanate. With BPA-POx and low SBM content (50 wt%), a twin screw extruder had to be used for the blending. Under well-defined conditions, transparent linear PUs and linear segmented polyurethane-ureas have been prepared. This study confirms that for designing a nanostructured material from a reactive mixture with a triblock additive, one block, called “the nanostructuring block” has to remain soluble up to the end of the reaction.