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Superelasticity and shape memory effect in zirconia nanoparticles

mohsenzaeem's picture

In this work, superelastic and shape memory properties of single crystalline and polycrystalline yttria stabilized tetragonal zirconia (YSTZ) nanoparticles are studied by atomistic simulations. N. Zhang and M. Asle Zaeem. Superelasticity and shape memory effect in zirconia nanoparticles. Extreme Mechanics Letters 46 (2021) 101301 (8 pages).

Superelasticity and shape memory effect are two key properties of zirconia-based ceramics which are mediated by the reversible tetragonal to monoclinic phase transformation. Although experimental studies discovered that the shape memory behavior of ceramics can be improved by reducing the grain boundary density, degradation in shape memory response still happens after a few cycles of loading–unloading–heating–cooling. In this work, superelastic and shape memory properties of single crystalline and polycrystalline yttria stabilized tetragonal zirconia (YSTZ) nanoparticles are studied by atomistic simulations. Fully recoverable superelastic strain (8.3%) is observed in a single crystalline nanoparticle by merely removing the compressive load. However, the shape memory behavior degrades with the increase of loading–unloading–heating–cooling cycles. In other words, a higher temperature is required for an additional strain recovery, but certain residual displacement may still remain after few cyclic loadings. Amorphous phase formation and its accumulation around the applied load contact area, as well as an increase in surface roughness are responsible for the observed degradation of shape memory response. In a polycrystalline YSTZ nanoparticle, besides the regular reverse transformation at the end of cyclic loading, most amorphous phase transfers back to the original tetragonal structure. However, a small amount of monoclinic phase is restrained by the permanent amorphous phase and grain boundaries at the end of cyclic loading, causing degradation of shape memory behavior.

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https://authors.elsevier.com/c/1dChg8MuOh8Cuo

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