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1738595 
Journal Article 
Influences of pH value on the microstructure and phase transformation of aluminum hydroxide 
Du, X; Wang, Y; Su, X; Li, J 
2009 
1 
Powder Technology
ISSN: 0032-5910 
192 
1 
40-46 
WOS:000265179200008 
The effects of pH value on the composition, structure, morphology, and phase transformation of aluminum hydroxides prepared by chemical precipitation were studied. Aluminum hydroxide precipitated at the pH values of 5 and 6 is amorphous and transforms to alpha-Al(2)O(3) at 950 C via the amorphous aluminum hydroxide amorphous Al(2)O(3) -> alpha-Al(2)O(3) transformation path. Aluminum hydroxide precipitated at pH =7 is boehmite and transforms to alpha-Al(2)O(3) at 950 C via the gamma-AlOOH -> gamma-Al(2)O(3) -> alpha-Al(2)O(3) path. Aluminum hydroxide precipitated at pH values in the 8 to 11 range is bayerite and transforms to alpha-Al(2)O(3) at 1000 C via the alpha-Al(OH)(3) -> gamma-Al(2)O(3) -> epsilon-Al(2)O(3)+theta-Al(2)O(3) -> alpha-Al(2)O(3) path. Moreover, the pH value affects not only the morphology of aluminum hydroxide particles which changes from ultrafine floccules through 50 nm blowballs then to 150 nm irregular agglomerates with increasing pH value but also the microstructures of final decomposition products of aluminum hydroxides. (c) 2008 Elsevier B.V. All rights reserved. 
Aluminum hydroxide; Chemical precipitation; Microstructure; Phase transformation; alpha-Alumina formation