SÍNTESE DE PÓS DE ALUMINA DOPADOS COM MgO OBTIDOS PELO MÉTODO DE EMULSIFICAÇÃO COM ÁCIDO OLÉICO.

Abstract

The alumina has a series of crystalline phases until it reached its most stable structure, the a-Al2O3. The challenge has been to get the a-Al2O3 without excessive grain growth with the high temperature calcination. This study aimed to verify the synthesis of alumina powders pure and doped MgO, by the method of emulsification with oleic acid and verify the sinterability of these powders. The calcination temperature for obtaining α-Al2O3 powder was varied between 900° and 1200°C to verify the transformation phase, until complete conversion to α-Al2O3. Were made thermal analyzes and thermogravimetric (DTA / TG) from the powders pre calcined at 600°C, to determine the temperature of decompositio n of organic compounds and phase transformations. The calcination of the powder was also performed in an atmosphere of flow O2, to assist in the decomposition of organic compounds. The powders obtained after calcination at different temperatures and atmospheres were characterized by X-ray diffraction, infrared spectroscopy and scanning electron microscopy. The calcined powders that showed the phase a-Al2O3 as a major phase were pressed and sintered at 1600°C for 2 hours. It was observed that the sequence of processing for synthesis method studied made g-Al2O3, d-Al2O3, q-Al2O3 and a-Al2O3 and that MgO used as dopant for delayed processing steady a-Al2O3. The atmosphere of O2 did not significantly influence the process of transformation of alumina, but altered the morphology of the powders.