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Aboufadil Y.,Laboratoire des science des Materiaux | Hajjaji M.,Cadi Ayyad University | Raghni A.E.I.,Laboratoire des science des Materiaux | Thalal A.,Laboratoire des science des Materiaux
Transactions of the Indian Ceramic Society | Year: 2013

Heating transformations of calcareous chloritic-illitic and carbonate-free kaolinitic-illitic raw clays, and their mixes were investigated in the range of 700°-1060°C using X-ray diffraction, thermal analyses and scanning electron microscopy. Moreover, changes of bending strength, shrinkage and water absorption versus temperature and clay content were followed. The results showed that plagioclase and sanidine together with spinel formed and persisted in fired calcareous and non-calcareous clays respectively. In fired clay mixtures only plagioclase occurred. Formation of the latter phase was discussed using CaO-SiO2-Al2O3 equilibrium diagram. The intensification of the neoformation processes due to the increase of temperature together with melt formation mainly in carbonate-free clay improved the ceramic properties to certain extent. Improvement of the mechanical strength was also observed for mixture of clays. The reported diagrams, involving grain size distribution and chemical composition, showed that both clays and their mixtures could be suitable for porous tiles or lightweight ceramic blocks manufacturing. © 2013 The Indian Ceramic Society.

Elosrouti R.,Université Ibn Tofail | Sallek B.,Université Ibn Tofail | Chaair H.,Laboratoire Of Genie Des Procedes | Digua K.,Laboratoire Of Genie Des Procedes | Oudadesse E.H.,Laboratoire des science des Materiaux
Phosphorus, Sulfur and Silicon and the Related Elements | Year: 2014

Le comportement sous atmosphère humide des mélanges initiaux de la calcite et du di-ammonium hydrogénophosphate à différents rapport atomique (Ca/P)initiala été étudié. Lanalyse par diffraction des rayons X (DRX) montre que les produits obtenus ont tous une structure apatitique. Il montre la présence à côté de celle de lapatite, des raies identifiables à la calcite pour des rapports atomiques initiaux supérieurs à 1.50. Par ailleurs, la spectroscopie dabsorption infrarouge (IR) révèle dans les différents cas, la présence autre que les bandes attribuables aux ions PO4 3-dans une apatite, des bandes à 875 cm-1caractéristique des groupements HPO4 2-dans une apatite déficiente en ion calcium. De même, le traitement thermique à 1000°C des poudres synthétisés a mis en évidence que les apatites formées sont non stœchiométriques. Les analyses chimiques montrent, par ailleurs, que lorsque le rapport atomique Ca/P du mélange initial est inférieur à 1.50, lapatite formée a un rapport atomique Ca/P égal à 1.58. Par contre, lorsque le rapport Ca/P initial est supérieur à 1.50, le produit formé est biphasique et a un rapport atomique Ca/P de 1.62. Ce rapport est dû essentiellement à la présence dun excès de CaCO3dans le mélange initial (DRX, IR). Mots clés Apatite; atmosphère humide; calcite; hydrothermal; synthèse Abstract The behavior, in a humid atmosphere, of the initial mixtures of calcite and diammonium hydrogenophosphate at different atomic ratio (Ca/P) was studied. The X-ray diffraction (XRD) analysis shows that all the products obtained have apatite structure. For initial atomic ratios greater than 1.50, the XRD analysis shows the presence of reflections different from those of apatite, which may be attributed to calcite. Analysis by infrared (IR) absorption spectroscopy allows to distinguish between the two cases: in addition to the presence of bands due to the PO4 3-ions in apatite further bands at 875 cm -1characteristic of HPO4 2-in apatite deficient with respect to calcium ions are observed. Similarly, the powders synthesized by heat treatment at 1000°C showed that nonstoichiometric apatites are formed. Chemical analyses show, that when the atomic ratio Ca/P of the initial mixture is less than 1.50, the apatite formed has an atomic Ca/P ratio of 1.58. When the initial Ca/P ratio is greater than 1.50, the product formed is biphasic and has an atomic ratio Ca/P of 1.62. This result is mainly due to the presence of an excess of CaCO3in the original mixture (XRD, IR). © 2014 Copyright Taylor and Francis Group, LLC.

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