Nanocomposites in the systems Fe_1-xO-Fe₃O₄ and MgO-MgFe₂O₄ produced by mechanical alloying

Wustite-magnetite and magnesia-magnesioferrite nanocrystalline ceramics have been prepared by mechanical milling and spark plasma sintering. As-milled powders have a nanocrystalline structure in both systems. Low energy milling gives rise to an increasingly higher volume fraction of wustite as a function of milling time in the Fe_1-xO-Fe₃O₄ system. Similar results are obtained in the MgO-MgFe₂O₄ system with increasingly larger amounts of MgFe₂O₄ produced by milling. Composites of magnetic particles (Fe₃O₄ or MgFe₂O₄) in a nonconductive matrix (FeO or MgO, respectively) are found in the sintered samples. Measurement of magnetic properties can be used to determine conclusively the nature of the developed phases and the effect of grain size.