The effect of calcination temperature on some of the adsorptive propertiesof fine alumina powders obtained by emulsion evaporation technique

The thermal decomposition of an alumina precursor, obtained by the emulsion evaporation technique, was investigated by thermogravimetry (TG) and diffe rential thermal analysis (DTA). The thermal decomposition was completed in four steps between 100 degreesC and 550 degreesC. For each step, the activa tion energy was determined from the TG data by the Coats-Redfern procedure and the decomposition was discussed. The X-ray diffraction (XRD) data revea led that diaspore (beta -AlOOH) was formed during the emulsion evaporation. The resulting pure but porous alpha -Al2O3 powders were then calcined for 2 h at various temperatures between 600 degreesC and 1600 degreesC. The ads orption and desorption of N-2 on the calcined specimens at approximately 77 K was investigated. The variation of the total micro and mesopore volumes, the micropore volumes, the surface area and heat of adsorption as calculat ed from experimental data were discussed as a function of the calcination t emperature. It was observed that the above mentioned properties reached a m aximum at 800 degreesC, and then decreased rapidly by increasing temperatur e. It was concluded that it was possible to prepare fine alpha -Al2O3 powde rs whose specific surface areas varied between 20 and 90 m(2) g(-1) by chan ging the calcination temperature between 600 degreesC and 1600 degreesC. (C ) 2001 Elsevier Science B.V. All rights reserved.