The physicochemical nature of the metastability of a nonequilibrium tetragonal ZrO2 phaseстатья
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Дата последнего поиска статьи во внешних источниках: 18 июля 2013 г.
Аннотация:The behavior of zirconia samples differing in chemical history, dispersity, and hydration was studied. The stabilization of the nonequilibrium t-ZrO2 polymorph is due to the dispersity of the system and to the water contained in the hydrophilic solid phase and conserved in it up to high temperatures (on the order of 800-1000degreesC) as a defect-structure solid solution of composition ZrO1+x(OH)(2-2x). The effect of physical and chemical actions on the character of t-ZrO2 --> m-ZrO2 phase transition in ZrO2 was studied. Sonic physical and chemical actions are significant: compressing t-ZrO2 powders at elevated temperatures (T less than or equal to 250degreesC) appreciably shifts the equilibrium to the right (enhances the formation of the equilibrium phase), whereas a "template" noticeably slows down the process (raises the stability of the metastable t-ZrO2). The physical and chemical actions that have no effect on the character of t-ZrO2 --> m-ZrO2 phase transition are established, among these, mechanochemical treatment or freezing at 77 K.