Toward modelling of frictional ignition

International audienceThis work is part of a European sponsored project named MECHEX (GRD2-2000-30035) which aims at providing a new insight and data about the ignition hazard induced by mechanical contacts classically termed as "grinding", "friction" and "impact" so that some sort of classification of mechanical equipments against this specific hazard could be issued. "Friction" and "grinding" might be understood as continuous mechanical solicitation whereas "impact" would be referred to as an instantaneous action such as that of a flying object striking freely on a fixed target. Within that scope, we undertook a detailed physical analysis of possible ignition mechanisms on the basis of precise measurements of hot spots, temperatures and fragments and tried to link them to the thermomechanical properties of the contacting bodies

Prévision de l'adsorption sur charbon actif de micropolluants en solution dans une eau naturelle

LIMOGES-BU Sciences (870852109) / SudocSudocFranceF

In2 03 :Ge, a promising n-type thermoelectric oxide composite

International audienceWe have studied the chemical, structural and transport properties of a series of In2O3 based samples with germanium doping (from 0 to 15 atom%). X-ray diffraction and scanning electron microscopy studies show that the solubility limit of Ge in In2O3 is very small and that additions of more than about 0.5 atom% Ge lead to the presence of In2Ge2O7 inclusions. The electrical conductivity is strongly enhanced by Ge doping with best values exceeding 1200 S cm−1 at room temperature. On the other hand, the thermopower decreases with Ge addition, but the thermoelectric power factor remains higher than that of undoped In2O3 and is close to 1 mW m−1 K−2 at 1100 K in In1.985Ge0.015O3. The thermal conductivity is strongly reduced by Ge additions. The dimensionless figure of merit ZT reaches 0.1 at 1273 K in In2O3 and exceeds 0.45 at 1273 K in composite compounds with nominal composition In1.8Ge0.2O3

Enhancement of the thermoelectric performances of In2O3 by the coupled substitution of M2+/Sn4+ for In3+

International audienceThe thermoelectric properties of air-prepared cosubstituted indium oxide based compounds belonging to the series In2−2xMxSnxO3 (M=Zn, Cu, or Ni) have been studied. X-ray diffraction studies show that the solubility limit xmax increases from xmax=0.35 for M=Cu to xmax=0.45 for M=Zn and xmax=0.55 for M=Ni. The lattice parameters, following the Vegard law with increasing substitution rates are in good agreement with the divalent oxidation state for the M cations. Compared to the undoped In2O3 prepared in air, the electrical resistivity of the cosubstituted phases (M=Zn,Cu) is strongly decreased and exhibits a metallic behavior. A more complex behavior is observed for the Ni/Sn cosubstituted samples whose resistivity first decreases and then increases with x. The lowest resistivity values do not exceed 0.5 mΩ cm at room temperature. Despite the lower values of the thermopower in cosubstituted samples, the thermoelectric power factor is significantly higher than that of the undoped In2O3, leading to values exceeding 5.10−4 W m−1 K−2. Furthermore, as the lattice thermal conductivity is strongly reduced by the cosubstitution due to mass fluctuation scattering of the phonons, promising thermoelectric figure of merit ZT is observed, close to 0.3 at 1273 K in In1.6Zn0.2Sn0.2O3. Thus, this study emphasizes the important role of cosubstitution to improve the thermoelectric properties of these n-type oxides

Enhancement of the thermoelectric performances of In2O3 by the coupled substitution of M2+/Sn4+ for In3+

International audienceThe thermoelectric properties of air-prepared cosubstituted indium oxide based compounds belonging to the series In2−2xMxSnxO3 (M=Zn, Cu, or Ni) have been studied. X-ray diffraction studies show that the solubility limit xmax increases from xmax=0.35 for M=Cu to xmax=0.45 for M=Zn and xmax=0.55 for M=Ni. The lattice parameters, following the Vegard law with increasing substitution rates are in good agreement with the divalent oxidation state for the M cations. Compared to the undoped In2O3 prepared in air, the electrical resistivity of the cosubstituted phases (M=Zn,Cu) is strongly decreased and exhibits a metallic behavior. A more complex behavior is observed for the Ni/Sn cosubstituted samples whose resistivity first decreases and then increases with x. The lowest resistivity values do not exceed 0.5 mΩ cm at room temperature. Despite the lower values of the thermopower in cosubstituted samples, the thermoelectric power factor is significantly higher than that of the undoped In2O3, leading to values exceeding 5.10−4 W m−1 K−2. Furthermore, as the lattice thermal conductivity is strongly reduced by the cosubstitution due to mass fluctuation scattering of the phonons, promising thermoelectric figure of merit ZT is observed, close to 0.3 at 1273 K in In1.6Zn0.2Sn0.2O3. Thus, this study emphasizes the important role of cosubstitution to improve the thermoelectric properties of these n-type oxides

In2 03 :Ge, a promising n-type thermoelectric oxide composite

International audienceWe have studied the chemical, structural and transport properties of a series of In2O3 based samples with germanium doping (from 0 to 15 atom%). X-ray diffraction and scanning electron microscopy studies show that the solubility limit of Ge in In2O3 is very small and that additions of more than about 0.5 atom% Ge lead to the presence of In2Ge2O7 inclusions. The electrical conductivity is strongly enhanced by Ge doping with best values exceeding 1200 S cm−1 at room temperature. On the other hand, the thermopower decreases with Ge addition, but the thermoelectric power factor remains higher than that of undoped In2O3 and is close to 1 mW m−1 K−2 at 1100 K in In1.985Ge0.015O3. The thermal conductivity is strongly reduced by Ge additions. The dimensionless figure of merit ZT reaches 0.1 at 1273 K in In2O3 and exceeds 0.45 at 1273 K in composite compounds with nominal composition In1.8Ge0.2O3

CREUATS/CRUZADOS, NUEVOS TERRITORIOS DE VANGUARDIA

Architetto Invitato (spazio Actar Arquitectura) alla Esposizione Colettiva CREUATS/CRUZADOS, NUEVOS TERRITORIOS DE VANGUARDIA (Palau de la Virreina, Barcelona 2004.) Spazio dedicato al lavoro di ricerca de Manuel Gausa e del Laboratorio Actar Arquitectura presentato alla mostra e esposizione internazionale (curatori Oscar Guayabero, David Lorente, Amadeu Santacana) intorno a lavori di creazione e ricerca avanzzati

Ignition of dust clouds and dust deposits by friction sparks and hotspots

Evaluating the effectiveness of mechanical ignition sources in igniting dust clouds and deposits is a major problem when assessing the risks in powder handling plants. This paper describes the results obtained in the recent European collaborative project, MECHEX, with explosible dusts. These involved both friction and impact ignition tests with different dusts including coal, maize starch, calcium stearate, suphur and sawdust as well as hotspot tests. using both large hotspots in dust deposits and small laser heated hot particles in dust clouds. The experimental work was carried with the aim of providing guidance for inclusion in European Standards on mechanical equipment for use in potentially explosive atmospheres. Although still inconclusive, the results obtained provide further information for understanding the complex problem of frictional ignition