High-energy ball-milled (alpha-Fe_2O_3)(alpha-Al_2O_3) system: A study on the milling time effects

摘要

The system (a-Fe_2O_3).,(a-Al_2O_3)_(1-x) was subjected to high-energy ball-milling, with the milling time varying between 3 and 72h. The precursor powders, alumina and hematite, were pre-mixed in nominal concentrations x = 0.10, 0.25 and milled in a planetary ball-mill, under specific milling conditions. The milled samples were characterized through scanning electron microscopy, X-ray diffraction and Mossbauer spectroscopy. As a result of the above analyses, the formation of two isostructural solid solutions, a-(FeDELTA_yAl_(1-DELTA_y)_2O_3 and alpha-(FeDELTA_yAl_(1-DELTA_y)_2O_3, which evolve peculiarly with the milling time, was observed. For samples with x = 0.10, a-Fe and the FeAl_2O_4 compound were identified, in addition to the solid solutions. The presence of the spinel and metallic iron phases is attributed to the abrasion of the vial and balls. For x - 0.25 samples, the iron content tends, for increasing milling times, to be equally shared between both solid solutions, verifying the driving force of the process to homogenize the system under milling.