MECHANOCHEMICAL PROCESSING OF ZRSIO4

The mechanochemical processing of the mineral zircon (ZrSiO4) is inves tigated with a view to exchanging the zirconium for other metals, lead ing to an easily extracted zirconia (ZrO2) phase. Room-temperature hal l milling of zircon with calcium and magnesium in dry conditions, and with calcium hydroxide and sodium hydroxide in wet conditions, is exam ined. X-ray powder diffraction, scanning electron microscopy and diffe rential thermal analysis were employed in analysis of as-milled and an nealed powders. The effects of milling time and subsequent heat treatm ent on structure and morphology are reported. The results indicate tha t mechanochemical processing significantly increases the reactivity of zircon towards reducing metals. No immediate exchange reaction was fo und for as-milled powders, but after annealing at 1000 degrees C all s amples showed partial or complete decomposition of ZrSiO4 resulting in multiphase systems. In these systems the major crystalline products w ere identified as ZrO2 or CaZrO3.