Joaquin Requena | Searcharxiv

arXiv2018

Percolative Mechanism of Aging in Zirconia-Containing Ceramics for Medical Applications

Recently, several episodes of fracture of zirconia ceramic femoral heads of total hip prostheses have alarmed the medical and scientific community regarding aging problems in zirconia prostheses. Such fractures cause immediate local tissue reactions, which require urgent medical intervention to prevent further complications. As a result, it has been promoted that yttria-stabilized zirconia (Y-TZP) hip prostheses be substituted by alumina and alumina/Y-TZP ceramics. In the present investigation, we have found an upper limit of Y-TZP concentration in alumina/Y-TZP composites (16 vol.%) to avoid future aging problems. This limit coincides with the percolation threshold measured by infrared (IR) reflectance in a series of alumina/Y-TZP composites.

physics.app-ph↗

arXiv2018

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

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.

cond-mat.mtrl-sci↗