Abstract:
The aim of this study was to produce nanosized alumina powders from two different aluminum salts (AlCl3 and AlNO3.9H(2)O) by precipitation method and to investigate transformation kinetics of alpha-Al2O3 crystallization obtained from quantitative DTA curves via Kissinger-Akahira-Sunose (KAS) method. Precipitates are dried at 80 A degrees C for 24 h and then calcinated at 1200 and 1300 A degrees C for 1 h. Dried powders have bayerite [Al(OH)(3)] and calcinated powders have theta- (theta) and alpha (alpha)-alumina phases which confirmed by XRD analysis, and the crystallite size of powders determined by Scherrer equation is about 30 nm for dried powders and ranged from approximately 15-35 nm for calcinated powders. Scanning electron microscopy studies revealed that the morphology and size of powders precipitated from two different salts are similar to each other, and powders contain mainly sub-micrometer-sized particles and close to spherical form. Activation energy values determined by KAS equation range from 717 to 411 kJ mol(-1) for powders produced from aluminum nitrate salt and from 844 to 476 kJ mol(-1) for powders produced from aluminum chloride salt depending on the transformation rate.
