The Effects of pH on the Preparation of Alumina by Sol-Gel Process

ABSTRACT This article describes the effects of pH on the preparation and properties of aluminas (A l 2 O 3) produced by the sol-gel colloidal method. The precursor, hexahydrated aluminum chloride, was subjected to peptization reactions giving rise to a viscous gel with amorphous characteristics. Calcination at temperatures about 1000°C caused this gel to transform into alumina products with different morphologies, such as powders, fibers, or porous ceramic bodies, depending on the process parameters adopted, such as the pH and the drying conditions. These products were characterized according to their particle size distribution, thermogravimetry and differential thermal analysis (TG/DTA), and X-ray diffraction (XRD), and their morphologies were analyzed by scanning electron microscopy (SEM).