Document Type : Research Paper
Faculty of Materials & Metallurgical Engineering, Semnan University, Semnan, Iran.
In the present study, the gamma alumina (γ-Al2O3) nano powders have been prepared with addition of 1%mol Co using an aqueous sol-gel method at lower temperature than the pure gamma alumina. The synthesis process accomplished by partial hydrolysis of the aqueous solution of metallic ions Al3+ and Co2+, with ammonia. The Al(NO3)3.9H2O and Co(NO3)2.6H2O salts were used as cations sources. The obtained gel at 40 ˚C dried at 120°C and calcined at different temperatures. X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and BET method of surface analysis were applied for powders characterization. The results indicated that the well crystallization of the gamma phase occurred at about 700°C for the Co doped samples while it was 900 °C for the pure sample. The specific surface area and particle sizes of the powders varied from 186 to 140 m2/g and 8 to 11 nm for pure and cobalt added γ-Al2O3, respectively. Both powders have the meso-porous structure according to the hysteresis loop of the adsorption/desorption curves of BET analysis. In addition, the TEM diffraction pattern of the gamma alumina at the presence of Co contains some bright diffracted points due to its higher degree of crystallinity in comparison with the pure powder.