Síntese e caracterizaçäo de compósitos Fe-Al2O3

Abstract

We have synthetized composites of the type Fex(Al2O3)100-x by arc melting, with nominal starting compositions with x =0.4, 1, 2, 3, 5, 10, 20, 40 and 60, and by mechanical alloying in a high energy ball miller with x=O.4, 2, 10,20 and 60, and milling times varying between 1h and 72h. The samples were characterized by x-ray diffractometry, magnetization and, mainly, by Mössbauer spectroscopy R. T. and 7 ºC. The results revealed the formation of hercynite (FeAl2O4) and the partial nanostructuration of the metallic iron for both preparation processes. An influence of the aluminurn oxide purity or cristallinity on the reacted samples was also observed. It was determined the phase fraction for the arc-melted composites and the preferential occupation of the A and B spinel sites as a function of X. An arc-melted sample was annealed at 1.200°C in a hydrogen atmosphere, revealing a phase separation of the metallic iron from the hercynite. The product of the high energy milling, or the fractions of the formed phases and the site occupation by the iron cations of the spinel sites showed that it depends, like the melted samples, on the initial iron content of the mixed powder (x), besides to the milling time.