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Facile Preparation of Ultrafine Aluminum Hydroxide Particles with or without Mesoporous MCM-41 in Ambient Environments
Published on: May 11, 2017
Relationship between formation conditions, properties, and crystallite size of boehmite
Kiyoshi Okada1, Toru Nagashima, Yoshikazu Kameshima
1Department of Metallurgy and Ceramics Science, Tokyo Institute of Technology, O-okayama, Meguro, Tokyo 152-8552, Japan.
Abstract:
Boehmites (gamma-AlOOH) with a variety of crystallite sizes were prepared under various precipitation conditions from solutions of aluminum nitrate and sodium aluminate and also by hydrothermal treatment of a commercial boehmite powder. The relationships between the crystallite size and other properties of the boehmites were investigated. Crystalline boehmite was formed in the pH range 7 to 10 while gels precipitated below pH 7 and bayerite (Al(OH)3) formed at pH 11. The crystallite size of the boehmite increased at higher pH, higher temperature of the precursor solution, and longer aging time. As the crystallite size of the boehmite increased, the specific surface area, pore volume, and excess water decreased. Boehmites of small crystallite size, called pseudoboehmite, showed broadened X-ray peak widths and increased d-spacing of the 020 reflection. These changes are attributed to the small crystallite size (smaller numbers of stacking layers) and also to excess water in the interlayers of the boehmite structure.
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