Preparation and characterization of ultrafine alumina via sol-gel polymeric route

Ultrafine alumina powder was prepared through resin formation between urea and formaldehyde. Aluminium stearate soap was introduced during resin preparation. Ethylene glycol was used to terminate the thermosetting reaction. Calcination of the product was carried out at 700, 1000, 1100, 1300 and 1400 degrees C to obtain aluminium oxide. IR and Raman spectroscopic analysis indicated the occupation of Al3+ at different sites in the polymer network (C=O, -NH2, C-O, -NH, and -CH2OH). X-ray diffraction of powder calcined at 1000 degrees C revealed the presence of a mixture of alpha- and theta-alumina together, while a mixture of alpha- and beta-alumina phases were obtained on calcination at 1400 degrees C. Transmission electron microscope (TEM) examination of the powder fired at 700 degrees C showed uniform grains in the form of clusters with average size between 22.02 and 30.5 nm. Clusters are multi-particles as evident from the electron diffraction pattern. Crystallite size of alumina powder calcined at 1000 degrees C was found to be approximate to 25.67 nm, while that of powder calcined at 400 degrees C was approximate to 30.52 nm. The calculated specific surface area of alumina powder calcined at 1000 degrees C was 59.17 m(2) g(-1), while that calcined at 1400 degrees C was 49.77 m(2) g(-1). (C) 2008 Elsevier B.V. All rights reserved.