ISSN:
1573-4803
Source:
Springer Online Journal Archives 1860-2000
Topics:
Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
Notes:
Abstract Aluminum nitrate and tetraethyl orthoxysilane were used as starting materials. They were mixed at different ratios ranging from 1.8 to 4.8 (Al3+/Si4+) and dissolved in ethyl alcohol. The pH of the reaction solution was also varied by the addition of ammonium hydroxide at a range of 8.3 to 10.4. Experiments were carried out at 25 and 60°C. In each case the materials were hydrolysed to a colloidal solution which was then filtrated and the resulting colloids retained on the filter as a gel which after drying at 110°C became a xerogel. The xerogels then were characterized by BET, SEM/TEM, and XRD/XRF. Of all the factors studied the pH of the reaction mixture was found to have the greatest affect on the morphology of the crystalline phase in the xerogels. Fibrous pseudoboehmite was found at the lower pH values of 8.3 and bayerite was present at pH value greater than 9.5 and became the predominant species at pH values greater than 10.4. The Al3+/Si4+ ratios and the reaction temperature both affected the crystallinity of the xerogels but to a much lesser degree than did the pH.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF02385419
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