Mechanochemical Reactions in Fe2O3-M (M: Al, Ti), Present and Future of mechanosynthesis

DAMONTE, CRISTINA; CUADRADO LABORDE, CHRISTIAN; MENDOZA ZELIS, LUIS

Caracas, Venezuela

Workshop; Seventh Latin American Conference on Applications of the Mössbauer Effect (LACAME); 2000

Univesidad Central de Venezuela

The production of metal–ceramic nanodispersion by mechanical milling of powders through the displacement reaction Fe2O3+M→Fe+M-oxide (with M: Al, Ti) was studied. Stoichiometric quantities of commercially obtained Fe2O3 (99.99%), Ti(-15 mesh, 99.9 %) and Al (-325 mesh, 99.5 %) powders were encapsulated under argon atmosphere in a cylindrical chamber (8 cm3) with one steel ball of 12 mm. An extra 10 at% metal was added in order to avoid superficial oxidation, being the final ball to powder weight ratio of 14:1 and 7:1 for Ti and Al, respectively. Mechanical alloying was performed in a shaker ball mill (Restch MM2000) at a frequency of 29 Hz. The reaction progress with milling time was followed by recording the temperature and pressure during the process. The samples were characterized by X-ray diffraction and Mössbauer spectroscopy at the intermediate and final stages. In both cases self-sustained reactions were observed with different activation times. For M=Ti, the reduction reaction takes place involving various intermediate phases. The Mössbauer spectra showed a complicated shape due to the presence of different mixed oxides, some of them with a spinel structure and where cation disorder cannot be discarded. For M=Al the process was simpler. These preliminary results confirm that mechanical work at room temperature yields the reduction of hematite by Ti and Al. The dependence of the intermediate and final stages on the milling conditions and the starting composition will be discussed.