Search results for "Material chemistry"
showing 10 items of 413 documents
Design, assembly and characterization of silicide-based thermoelectric modules
2016
ID: 1143 In: Energy conversion and management, 13-21. Summary: Highlights•Novel silicide-based thermoelectric modules were experimentally investigated.•The modules produced high power of 1.04 W at 405 °C and 3.24 W at 735 °C.•An estimated module efficiency of 5.3% represent the highest reported for silicide systems.AbstractSilicides have attracted considerable attention for use in thermoelectric generators due mainly to low cost, low toxicity and light weight, in contrast to conventional materials such as bismuth and lead telluride. Most reported work has focused on optimizing the materials properties while little has been done on module testing. In this work we have designed and tested mod…
Continuous hydrothermal synthesis of inorganic nanopowders in supercritical water: towards a better control of the process
2009
International audience; A hydrothermal synthesis process working in supercritical conditions (T > 374 °C, P > 22 MPa) and in a continuous mode has been developed for inorganic nanopowder synthesis. This paper presents a review of the past 5 years of research conducted on this process. Numerous materials (oxides: ZrO2, TiO2, Fe2O3..., ferrites: Fe2CoO4..., or BaZrO3) were obtained with specific features. Some technical issues have been solved, that are presented here. Heat transfer was studied, leading to a more efficient design of the reactor. Future developments have been examined through process engineering, in which our group is engaged, especially through CFD modelling.
Mechanical properties and microstructural study of homogeneous and heterogeneous laser welds in α, β,and α + β titanium alloys
2018
International audience; Heterogeneous welding has been investigated for three different couples of titanium alloys: α/α + β, α/β,andα + β/β. Plates of 100 × 60 mm and 1.6 or 1.8 mm thick were welded with a Yb:YAG laser. Tensile tests show that the resistance of the heterogeneous welded specimens was generally controlled by those of the weakest material except for the α + β/β where the ultimate tensile strength was approximately equal to the average value of both materials. In every case, the elongation of the welded sample was found to be smaller than that of the base metals. The rupture generally took place outside the weld metal and was found to be most of the time located in the alloy ha…
Structure and composition heterogeneity of a FeAl alloy prepared by one-step synthesis and consolidation processing and their influence on grain size…
2006
Abstract This paper aims to characterize a bulk dense FeAl (47 at.%) alloy synthesized and consolidated by one-step current-activated pressure-assisted processing of nanocrystalline elemental powders. The end-product was analyzed using a combination of scanning (SEM) and transmission electron microscopies (TEM), electron back-scattering diffraction (EBSD) as well as electron probe microanalysis (EPMA). Special attention was paid to verify the grain size (32–89 nm) previously determined by X-ray diffraction peak profile analysis. It has been found that this material displays equiaxed grains (0.8–4 μm in size) and contains limited structural defects like subgrains and dislocations. The EPMA r…
Influence of three types of superplasticizers on tricalciumaluminate hydration in presence of gypsum.
2006
International audience; Different types of superplasticizers have been widely used over the past few decades in order to produce a more fluid or very high strength and durable concrete. These chemical admixtures interfere with the various physico-chemical processes occurring in early cement paste. In this paper we present results from a study on the influence of superplasticizers on pure tricalciumaluminate hydration in presence of gypsum. The suspensions hydration has been investigated by conductimetry, isothermal calorimetry and total organic carbon analysis of the liquid phase. The time taken for ettringite formation has been determined without superplasticizer and in presence of three d…
Study of the reactive dynamics of nanometric metallic multilayers using Molecular Dynamics: the Al−Ni system
2012
A molecular dynamics study of a layered Ni-Al-Ni system is developed using an embedded atom method potential. The specific geometry is designed to model a Ni-Al nanometric metallic multilayer. The system is initially thermalized at the fixed temperature of 600 K. We first observe the interdiffusion of Ni and Al at the interfaces, which is followed by the spontaneous phase formation of B2-NiAl in the Al layer. The solid-state reaction is associated with a rapid system's heating which further enhances the diffusion processes. NiAl phase is organized in small regions separated by grain boundaries. This study confirms the hypothesis of a layer-by-layer development of the new phase. For longer t…
Metal-organic magnets with large coercivity and ordering temperatures up to 242°C.
2020
International audience; Magnets derived from inorganic materials (e.g., oxides, rare-earth–based, and intermetallic compounds) are key components of modern technological applications. Despite considerable success in a broad range of applications, these inorganic magnets suffer several drawbacks, including energetically expensive fabrication, limited availability of certain constituent elements, high density, and poor scope for chemical tunability. A promising design strategy for next-generation magnets relies on the versatile coordination chemistry of abundant metal ions and inexpensive organic ligands. Following this approach, we report the general, simple, and efficient synthesis of light…
Ferroelectric-based nanocomposites : towards multifunctional materials
2007
Nanoparticle technologies open the routes for nanostructured materials which combine individual physical properties or generate new functions. In the field of ferroelectric materials the development of dense nanocomposites requires breakthroughs in the elaboration step. Here, we propose a flexible process to obtain ferroelectric−magnetic nanostructured materials using the assembly of superparamagnetic nanoparticles around ferroelectric cores. The appropriate shaping and sintering of these nanocomposites called nanoraspberries enables a tuning of the physical properties of the resulting dense composite: coexistence between ferroelectricity, piezoelectricity, and superparamagnetism is clearl…
Génération de supercontinuum infrarouge et enjeux de vieillissement au sein de fibres optiques à coeur suspendu hautement non linéaires en verre de c…
2014
The work reported in this thesis deals with the fabrication of suspended core chalcogenide microstructured optical fibers (MOFs) for supercontinuum generation (SCG) beyond 6 μm. In this context, As2S3-based suspended-core MOFs were fabricated under vacuum, and loss threshold of 1-2 dB/m at 2.9µm were systematically registered. In addition, MOFs were designed with core diameter ranging from 1.5 to 3.5µm, allowing therefore to control the MOF's dispersive properties and to shift corresponding zero dispersion wavelength to 2.0-2.5 µm range. SCG experiments were performed by pumping the fabricated MOFs in their anomalous dispersion regime by means of tunable femtosecond laser source. Simultaneo…
Shape transitions of giant liposomes induced by an anisotropic spontaneous curvature
2000
International audience; We explore how a magnetic field breaks the symmetry of an initially spherical giant liposome filled with a magnetic colloid. The condition of rotational symmetry along the field axis leads either to a prolate or to an oblate ellipsoid. We demonstrate that an electrostatic interaction between the nanoparticles and the membrane triggers the shape transition. PACS numbers: 75.