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Chemistry for Sustainable Development

2006 year, number 4

Nature of a Mechanically Stimulated Phase Change in Zirconia

G. R. KARAGEDOV, S. S. SHATSKAYA and N. Z. LYAKHOV
Institute of Solid State Chemistry and Mechanochemistry, Siberian Branch of the Russian Academy of Sciences, Ul. Kutateladze 18, Novosibirsk 630128 (Russia)
E-mail: garik@soild.nsc.ru
Pages: 345-353

Abstract

Reasons for phase change in zirconia upon its intensive mechanical treatment in mills have been discussed. It has been demonstrated that when used steel balls and barrels, oxidation of wear products and their mechanochemical interaction with ZrO2 occurs along with a decrease in the size of particles and crystallites. It has been found that implantation of cations of an extrinsic metal in the crystal lattice is favourable to the stabilization of a more symmetric modification and to an increase in the critical size of crystallites, above which the monoclinic modification becomes stable. A conclusion has been made that an increase in the contribution of superficial energy to the Gibbs energy plays dominating part in the phase change on initial stages of mechanical treatment, while the thermodynamic stability in the further process is controlled preferentially by a stabilising impact of impurity cations. Under conditions that prevent from pollution of ZrO2 by metal, a dynamic equilibrium is established between the forward change to tetragonal modification and the reverse, to monoclinic.