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Lyczko N.,French National Center for Scientific Research | Nzihou A.,French National Center for Scientific Research | Sharrock P.,SIMAD University | Germeau A.,PRAYON S.A.Siege de Engis | Toussaint C.,PRAYON S.A.Siege de Engis
Industrial and Engineering Chemistry Research | Year: 2012

LiFePO4/C was synthesized from a mixture of different precursors of Li, Fe, and C by solid-state reaction. The initial mixture obtained was heated in different calcination conditions under inert atmosphere. The precursor of LiFePO4 doped with carbon was studied using different techniques such as thermal analysis, chemical and physical characterizations, and Mösbauer spectroscopy. A calculation of the crystallinity of the final product with two different methods is also presented. The chemical analysis techniques used were IRTF, XRD, and SEM. This characterization confirmed that we obtained a well-crystallized LiFePO4/C in all the operating conditions tested. The SEM showed aggregation and sintering during the calcination process, which were confirmed by the particle-size distribution measurements and by the physical characterizations. Mösbauer spectroscopy was used to determine the quantity of Fe(II) and Fe(III) contained in the final product. Our calcination conditions did not significantly modify the quantity of the two oxidation states. © 2011 American Chemical Society.

Nzihou A.,French National Center for Scientific Research | Stanmore B.,University of Queensland | Sharrock P.,French National Center for Scientific Research | Sharrock P.,SIMAD University
Energy | Year: 2013

The best catalysts for promoting char gasification are Group I metals, particularly lithium and potassium, although other metals are active to a lesser extent. The most prevalent metal naturally in biomass char is potassium, which is not only inherently active, but volatilises to become finely distributed throughout the char mass. The formation of an active carbon/potassium complex is frequently proposed. Calcium is the other most common active metal found in biomass, but is far less effective and less volatile. In a gasification system the metals remain as carbonate due to the action of carbon dioxide. The alkali metals can react with silica to form silicates, which prevents catalytic action. Transition metals can also participate in catalysis of gasification; iron accelerates gasification and nickel prevents carbon deposition, which helps in conditioning biomass-derived syngas. Volatile iron pentacarbonyl has been identified as a promoter of the char gasification step, with catalytic activity related to the finely dispersed low-valency metal atoms generated during the thermo-decomposition of biomass. © 2013 Elsevier Ltd.

De La Jarrige E.L.,CNRS Laboratory for Analysis and Architecture of Systems | De La Jarrige E.L.,Toulouse 1 University Capitole | Escotte L.,CNRS Laboratory for Analysis and Architecture of Systems | Escotte L.,Toulouse 1 University Capitole | And 2 more authors.
International Journal of Microwave and Wireless Technologies | Year: 2012

The design of a high-stability radiometer is presented in this paper. It is used to characterize the stability of a microwave active cold load at L-band. The two-load radiometer takes advantage of a noise injection technique to improve its sensitivity. A temperature-stabilized enclosure is used to minimize gain and noise temperature fluctuations of the receiver. The radiometer sensitivity is 0.031 K and the gain fluctuations are less than 0.005 dB during 1 day. The total gain and the receiver noise temperature of the radiometer exhibit very small variations (<0.03 dB and 1 K, respectively) on the long term. © Copyright Cambridge University Press and the European Microwave Association 2011.

Gonneau E.,SIMAD University | Escotte L.,CNRS Laboratory of Analysis and Architectures of Systems | Escotte L.,University Of Toulouse Ups
IEEE Transactions on Microwave Theory and Techniques | Year: 2012

In this paper, the impact of low-frequency noise sources on the gain stability of microwave amplifiers is presented. The presence of a thermally activated relaxation process is experimentally demonstrated. To support the experiment, a mathematical model of this additional excess noise source is proposed in the Allan variance analysis. Different microwave amplifiers are also characterized and their stability is compared with the use of the Allan variance. © 1963-2012 IEEE.

Lyczko N.,French National Center for Scientific Research | Nzihou A.,French National Center for Scientific Research | Sharrok P.,French National Center for Scientific Research | Sharrok P.,SIMAD University
Procedia Engineering | Year: 2014

Heavy metal pollution in soils, wastewater or fly ashes is a persistent environmental problem. This pollution in water or wastewater is an ongoing environmental problem and the rules to control and decrease this pollution are increasingly strict. The extreme toxicity of heavy metals even at low concentration and their bio-accumulation cause a lot of environmental problems. Minerals such as the calcium phosphate of general formula M10(XO4)6 Y2 with M a divalent cation, (XO4)3- a trivalent anion and Y- a monovalent anion are well know for trapping metal ions. The retention of heavy metals by calcium phosphate has been already widely studied in aqueous solutions. In this study, a low cost calcium phosphate gel (Ca-HA) synthesized from a calcium carbonate industrial waste was used as a sorbent for wastewater treatment. We have characterized this sorbent before and after use. The physical characterization showed a decrease of the specific surface area and density. The granulometry measurements showed an increase of the particles diameter explained by the sorption of pollutants (organic molecules). The presence of these molecules was confirmed by total and organic carbon measurement and thermal analysis. The elemental measurements confirmed also the heavy metal sorption by the Ca-HA. A calcination of the contaminated Ca-HA was carried out at different temperatures. After calcination the solid contained less organic molecules and heavy metals were concentrated in the matrix. © 2014 Published by Elsevier Ltd.

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