Influence of the microstructure on the life prediction of hydrothermal degraded 3Y-TZP bioceramics

Abstract

In this work, the effects of the microstructure on the hydrothermal degradation of yttria-stabilized tetragonal zirconia (Y-TZP) bioceramics and theoretical correlations of the zirconia grain size impact in simulations of body fluids were investigated. Samples of ZrO2 (3 mol.% Y2O3) powders were compacted and furtherly sintered for 4 h at different temperatures (1450, 1500, 1530 or 1600 °C), reaching nearly full density in microstructures with different grains sizes ranging from 0,35 ± 0,10 μm to 1,53 ± 0,34 µm. Tests of hydrothermal degradation were performed in autoclave (134 °C - 2 bar), varying the dwell time between 1 and 36 h. The growth of the ZrO2 grain size consistently affected the rate of degradation (represented by the transformed monoclinic m-ZrO2 content) of this ceramic: After 12 h of autoclaving, the monoclinic percentage quadrupled with an increase in the average grain size of 0.35 ± 0.1 μm to 1.53 ± 0.34μm. Using a theoretical correlation between the time of degradation in the autoclave and the respective time in the human body, it was possible to predict the content of the monoclinic phase present in the 3Y-TZP for up to 36 years of exposure in body fluids, and with that, mathematical equations that correlate grain size of ZrO2 with %monoclinic were proposed.

Keywords

• 3Y-TZP ceramics
• Hydrothermal degradation
• Grain growth
• t→mTransformation