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Home  >  Journal list  >  Journal of the Ceramic Society of Japan  >  Vol.115  No.1348 (December) (2007)  >  pp.894-897

Journal of the Ceramic Society of Japan
<<Previous article Vol.115  No.1348 (December) (2007)   pp.894 - 897 Next article>>

Hydrothermal Synthesis of Boehmite Plate Crystals

Kazumichi YANAGISAWA1), Daisuke GUSHI1), Ayumu ONDA1) and Koji KAJIYOSHI1)
1) Research Laboratory of Hydrothermal Chemistry, Faculty of Science, Kochi University

  Large plate crystals of boehmite up to 4 μm were prepared from Al(NO3)3 solutions with the addition of NaOH under hydrothermal conditions at 250°C for 6 h. The conditions to obtain monodispersed boehmite large plate crystals were determined to be in the range of OH/Al molar ratio from 3.5 to 3.8 and Al concentration from 1.3 to 2.0 mol/kg. Bayerite formed by mixing the starting materials changed to gibbsite at 200°C, and at the same time boehmite started to crystallize from gibbsite. Even after complete phase change from gibbsite, small boehmite crystals grew larger by dissolution and precipitation mechanism. The key to obtain boemite large plate crystals is the preparation of homogenous fine boehmite crystals by quickly heating fine gibbsite crystals to the boehmite stable region, as well as the selection of OH/Al molar ratio and Al concentration.



Keyword:
Boehmite, Large plate crystals, Hydrothermal reaction, Aluminum nitrate, Crystal growth

Received: August 27, 2007
Accepted: September 20, 2007 , Published online: December 01, 2007
Copyright (c) 2007 The Ceramic Society of Japan

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