Solidification de déchets ultimes et comportement à la lixiviation. Apport des techniques X

Les techniques X (diffraction et fluorescence) sont indispensables dans le domaine des déchets ultimes et de leur traitement. En effet ces déchets 'toxiques' doivent être stabilisés et solidifiés avant d'être mis en décharge. Les techniques X nous ont donc permis de caractériser les déchets bruts (REFIOM : résidus d'épuration des fumées d'incinération d'ordures ménagères) et de déterminer un mode de traitement adapté. Ce procédé a pu être validé par la caractérisation des déchets traités, c'est à dire qu'on a pu mettre en évidence la formation de phases (ettringite, monochloroaluminate de calcium hydraté) moins solubles qui fixent certains polluants (chlorures et sulfates principalement) et qui favorisent la solidification. De plus, ces techniques ont été très utiles afin d'appréhender les comportements des déchets traités à la lixiviation. La caractérisation chimique par fluorescence X de chaque 'tranche' obtenue par un découpage radial du monolithe lixivié a permis de suivre l'évolution des profils de concentration dans le monolithe pendant la lixiviation. L'étude de ces gradients de concentration associée à des analyses par diffraction X nous a permis de préciser les scénarios de transfert des chlorures ; ces scénarios de transfert étant fortement conditionnés par l'évolution du pH.The X-ray analysis (diffraction and fluorescence) are useful for the characterization of the ultimate wastes and they are an important assessment for the evaluation of the wastes treatment. In fact toxic wastes must be stabilized and solidified before their disposal in special landfill. So the X-ray analysis allow to characterize the wastes (MSWIR : municipal solid wastes incinerator residues) and to determine an adapted treatment. The process was validated by the characterization of the stabilized wastes i.e. formation of mineralogical phases less soluble which fix pollutants (mainly chlorides and sulfates) and which improve the solidification. Moreover, the X-ray analysis allow to explain the leaching behavior of the stabilized wastes. The leached monoliths were cut up and the chemical characterizations by X fluorescence allow to follow the concentration profiles in the leached monoliths. The study of these concentration profiles and the analysis by XRD lead to propose transfer scenarios of chlorides ; these scenarios are dependent on the pH values

Physical parameters of components in close binary systems - VII

We present results of the modelling of multicolour light curves of 10 contact binary systems: V376 And, V523 Cas, CC Com, BX Dra, FG Hya, UZ Leo, XY Leo, AM Leo, EX Leo and RT LMi. The solutions resulted in a contact configuration for all systems. We found only FG Hya and UZ Leo to be in deep contact, the latter almost filling the outer critical lobe. The absolute parameters of the components have been determined with an accuracy of about a few per cent based on combined photometric and radial velocity curves, enlarging the sample of systems to 58 for which the physical parameters have been obtained in a uniform way. All but three systems (BX Dra, AM Leo and RT LMi) show asymmetries and peculiarities in the observed light curves, interpreted as resulting from their magnetic activity. © 2010 The Authors. Journal compilation © 2010 RAS

Étude d'un granulat alcali-réactif par diffraction des rayons X

La réaction alcali-granulat (RAG) est un processus physico-chimique de dégradation interne des bétons. Les bétons atteints par cette réaction sont constitués de granulats dits alcali-réactifs. Ces granulats comportent des phases de type quartz présentant des défauts internes appelés silanols. Le développement de la RAG au sein du granulat s'accompagne d'un accroissement du nombre de silanols internes. Pour étudier cette transformation structurale, nous avons suivi l'évolution des pics de diffraction des rayons X de la phase quartz en fonction de l'avancement de la réaction. Le granulat silex étudié présente des largeurs de raies à mi-hauteur importantes traduisant la présence de silanols internes. Au fur et à mesure que la réaction progresse nous observons une réduction de la largeur de raie à mi-hauteur et de la surface des pics de diffraction. Nous interprétons ce résultat comme une amorphisation de zones riches en défauts internes, les zones les mieux cristallisées, situées vraisemblablement au centre de ces domaines imparfaits se trouvant progressivement dégagées au cours de l'attaque.The Alkali-Aggregate Reaction (AAR) is a physico-chemical process of internal damage of concrete. The concretes damaged by this reaction are constituted of alkali-reactive aggregates. These aggregates have quartz phases with internal flaws called silanols. AAR development within aggregate involve an increase of internal silanols number. To study this structural transformation, we have followed the evolution of X-ray diffraction peaks of quartz phase as a function to reaction degree. The flint aggregate shows high ray width at half medium which traduces the presence of internal silanols. As the reaction progress we observe a decrease of ray width at half medium and surface of diffraction peaks. We interpret this result like the transition of zones with internal flaws in amorphous zones. The best crystallized zones are progressively revealed by the attack

The W UMa-type stars program: First results, current status and perspectives

We present the results of a statistical investigation of the period-color and period-bolometric magnitude relations using a carefully selected sample of 120 contact systems with known physical parameters. © Springer Science+Business Media B.V. 2006

Physical parameters of close binary systems: VIII

This paper presents the results of a combined spectroscopic and photometric study of 20 contact binary systems: HV Aqr, OO Aql, FI Boo, TX Cnc, OT Cnc, EE Cet, RW Com, KR Com, V401 Cyg, V345 Gem, AK Her, V502 Oph, V566 Oph, V2612 Oph, V1363 Ori, V351 Peg, V357 Peg, Y Sex, V1123 Tau, and W UMa, which was conducted in the frame of the W UMa Project. Together with 51 already covered by the project and an additional 67 in the existing literature, these systems bring the total number of contact binaries with known combined spectroscopic and photometric solutions to 138. It was found that mass, radius, and luminosity of the components follow certain relations along the MS and new empirical power relations are extracted. We found that 30 per cent of the systems in the current sample show extreme values in their parameters, expressed in their mass ratio or fill-out factor. This study shows that, among the contact binary systems studied, some have an extremely low mass ratio (q < 0.1) or an ultrashort orbital period (Porb < 0.25 d), which are expected to show evidence of mass transfer progress. The evolutionary status of these components is discussed with the aid of correlation diagrams and their physical and orbital parameters compared to those in the entire sample of known contact binaries. The existence of very short orbital periods confirms the very slow nature of the merging process, which seems to explain why their components still exist as MS stars in contact configurations even after several Gyr of evolution. © 2021 The Author(s) Published by Oxford University Press on behalf of Royal Astronomical Society