Low-temperature ageing of zirconia-toughened alumina ceramics and its implication in biomedical implants

TL;DR

This study investigates low-temperature ageing effects on zirconia-toughened alumina ceramics, revealing that alumina matrix presence slows ageing, with composites containing over 25 wt.% zirconia showing limited degradation, relevant for biomedical implant durability.

Contribution

The paper compares ageing behavior of different zirconia-alumina composites processed via classical and colloidal routes, highlighting the influence of composition and processing on ageing resistance.

Findings

Ageing is slower in alumina-yttria stabilized zirconia composites than in Y-TZP.

Composites with over 25 wt.% zirconia exhibit limited ageing.

Al2O3+2.5 wt.% ZrO2 composites show no ageing degradation.

Abstract

Changes in crystalline phases resulting from low-temperature ageing of different yttria doped and non-doped zirconia-toughened alumina composites and nanocomposites were investigated under controlled humidity and temperature conditions in autoclave. A classical powder mixing processing route and a new modified colloidal processing route were used to process the composites. Different compositions ranging from 2.5 wt.% zirconia in a matrix of alumina to pure zirconia (3Y-TZP) were studied. It was observed that Al2O3+yttria stabilised ZrO2 composites exhibited significant ageing. However, ageing was much slower than traditionally observed for Y-TZP ceramics, due to the presence of the alumina matrix. Ageing was clearly limited for zirconia content beyond 25 wt.%. On the other side of the spectrum, Al2O3+2.5 wt.% ZrO2 initially presented a monoclinic fraction but did not show any ageing degradation. These composites seem to represent the best choice between slow crack growth and ageing resistance.