Home – Home – Jornals – Chemistry for Sustainable Development 2004 number 2

The effect of mechanical activation of well crystallized zirconium oxide of monoclinic modification in a centrifugal planetary activator mill and in vibratory mill on the characteristics of fine crystalline structure and phase transformation depending on the treatment environment and mechanical loading is investigated. It is established that the mechanical action in the centrifugal planetary mill stimulates dispersion processes, accumulation of microdeformations, and phase transition of the oxide into the tetragonal form. The rate of processes depends on the environment of treatment: for mechanical activation of the dry powder, the phase transition occurs within 15 min, the rate of the process decreases in the presence of water as additive. Treatment in vibratory mill causes mainly crushing of the particles and accumulation of microdeformations. After 2 h, the size of crystallites decreases to 38 nm and remains unchanged during further treatment; gradual accumulation of microdeformations and amorphization of structure occur. After 15 h, the fraction of the crystalline phase was 15 %; no formation of other crystalline phases was observed. The formation of a metastable tetragonal form of ZrO₂ in the activator apparatus can be due to the pulsed character of powerful mechanical action, which causes intense crushing of the crystallites (20 nm) and can create local conditions favourable thermodynamically and kinetically for the phase transition in separate regions of the solid.