DAMBOURNET, Damien; DEMOURGUES, Alain; MARTINEAU, Charlotte; DURAND, Etienne; MAJIMEL, Jérôme; VIMONT, Alexandre; LECLERC, Hervé; LAVALLEY, Jean-Claude; DATURI, Marco; LEGEIN, Christophe; BUZARÉ, Jean-Yves; FAYON, Franck; TRESSAUD, Alain

doi:10.1039/b718856k

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DAMBOURNET, Damien
Institut de Chimie de la Matière Condensée de Bordeaux [ICMCB]

DEMOURGUES, Alain
Institut de Chimie de la Matière Condensée de Bordeaux [ICMCB]

MARTINEAU, Charlotte
Laboratoire des oxydes et fluorures [LdOF ]
Institut de recherche en ingénierie moléculaire et matériaux fonctionnels de l'université du Maine [IRIMMFUM]

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Journal of Materials Chemistry. 2008, vol. 18, n° 21, p. 2483-2492

Royal Society of Chemistry

Résumé en anglais

High surface area aluminium hydroxyfluoride exhibiting the pyrochlore-type structure has been synthesized using microwave hydrothermal process. The optimization of the crystallite size and surface area of the material has been performed by varying some synthesis parameters, i.e. the nature of the aluminium precursor, the choice of solvents and the addition of a small amount of ether. The as-prepared solid contains nanosized particles as calculated by XRD (average particle size: 12 nm) leading to a surface area around 140 m2 g-1. These results have been confirmed by TEM observations. The framework is built of AlF6-x(OH)x species which have been characterized and quantified by high field 27Al NMR. A random distribution of F atoms and OH groups is evidenced to occur on the 48f sites. Inside the channels, water molecules interact with the framework by hydrogen bonding either with fluoride ions or OH groups present in their vicinity. The use of probe molecules has shown that the pyrochlore exhibits a Lewis acidity lying between that of -Al2O3 and that of the strong Lewis acid -AlF3 adopting the hexagonal tungsten bronze form. Surface OH groups have been characterized by IR spectroscopy and exhibit weak Brønsted acidity.< Réduire

Mots clés en anglais

Hydroxyfluorides

Aluminium

Acidic properties

Pyrochlore

Microwave hydrothermal process

Surface

Crystal structure

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Structural investigations and acidic properties of high surface area pyrochlore aluminium hydroxyfluoride

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