MECHANICAL ALLOYING OF OXIDES

Mechanical alloying is a synthesis method using high energy ball milli ng which allows to prepare a large number of materials, often in a met astable form, with a nanometric grain size. Moreover, high energy ball -milling modifies the chemical reactivity of solids and induces chemic al reactions and solid state phase transformations : amorphization, al lotropic transformations, order-disorder transitions. This paper repor ts results concerning the ball-milling effects applied to oxides. Vari ous examples illustrating the preparation of oxide compounds and solid solutions are reported. Some of these products are non-equilibrium ph ases and can be prepared by other methods only at high pressure or/and high temperature. The chemical reactions and phase transformations ca n be influenced by the milling environment (steel or zirconia), more e specially when reduction reactions occur between oxide particles and m illing tools.