کد مقاله | کد نشریه | سال انتشار | مقاله انگلیسی | نسخه تمام متن |
---|---|---|---|---|
9694270 | 1459644 | 2005 | 15 صفحه PDF | دانلود رایگان |
عنوان انگلیسی مقاله ISI
Structure and thermal behavior of nanocrystalline boehmite
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کلمات کلیدی
موضوعات مرتبط
مهندسی و علوم پایه
مهندسی شیمی
جریان سیال و فرایندهای انتقال
پیش نمایش صفحه اول مقاله
چکیده انگلیسی
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 (â¼0.2 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,â¦).
ناشر
Database: Elsevier - ScienceDirect (ساینس دایرکت)
Journal: Thermochimica Acta - Volume 425, Issues 1â2, 20 January 2005, Pages 75-89
Journal: Thermochimica Acta - Volume 425, Issues 1â2, 20 January 2005, Pages 75-89
نویسندگان
Pierre Alphonse, Matthieu Courty,