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Structure and thermal behavior of nanocrystalline boehmite

Alphonse, Pierre and Courty, Matthieu Structure and thermal behavior of nanocrystalline boehmite. (2005) Thermochimica Acta, vol. 4 (n° 1-2). pp. 75-89. ISSN 0040-6031

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Official URL: http://dx.doi.org/10.1016/j.tca.2004.06.009

Abstract

First, the structural features of nanocrystalline boehmite synthesized by hydrolysis of aluminum sec-butoxide according to the Yoldas method are reported. The nanosized boehmite consists of rectangular platelets averaging 8 by 9 nm and 2–3 nm in thickness which contain a large excess of water. Dehydration by heating under vacuum induced an increase in the specific surface area, down to a minimum water content ( 0.2 H2O per Al2O3); values up to 470 m2/g can be reached. However this enlargement of specific surface area only results from water loss, the surface area remaining constant. The particle morphology, the excess of water, as well as the specific surface area, depend on the amount of acid used for the peptization during the synthesis. Second, a comprehensive investigation of the dehydration kinetics is presented. The simulations of the non-isothermal experiments at constant heating rates show that thermally stimulated transformation of nanocrystalline boehmite into alumina can be accurately modeled by a 4-reaction mechanism involving: (I) the loss of physisorbed water, (II) the loss of chemisorbed water, (III) the conversion of boehmite into transition alumina, (IV) the dehydration of transition alumina (loss of residual hydroxyl groups). The activation energy of each step is found to be very similar for experiments done in various conditions (heating rate, atmosphere, kind of sample,…).

Item Type:Article
Additional Information:Thanks to Elsevier editor. The definitive version is available at http://www.sciencedirect.com The original PDF of the article can be found at Thermochimica Acta website : http://www.sciencedirect.com/science/journal/00406031
Audience (journal):International peer-reviewed journal
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Institution: Université de Toulouse > Institut National Polytechnique de Toulouse - INPT
Université de Toulouse > Université Paul Sabatier-Toulouse III - UPS
French research institutions > Centre National de la Recherche Scientifique - CNRS
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Deposited By: Thomas Bonnecarere
Deposited On:13 Jun 2008 12:18

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