Development and characterization of Al₂O₃-based biocomposites reinforced with 3Y-TZP nanoparticles

Abstract

Alumina ceramics were reinforced with different amounts of stabilized-tetragonal zirconia nanoparticles, 3Y-TZP, and their properties were evaluated aiming for future applications in orthopedic medicine. Different amounts of 3Y-TZP (3 to 15 wt%) were mixed with Al₂O₃ powder, using high-energy milling (400 rpm-24 h). Samples were uniaxially compacted and sintered at 1600 °C-2 h. The samples were characterized by their relative density, microstructure, and crystalline phases. Furthermore, Vickers hardness, fracture toughness, and bending strength were determined. After the high-energy milling process, a considerable amount of monoclinic (m) ZrO₂ was detected in the powder mixtures, besides the α-Al₂O₃ and tetragonal (t) ZrO₂ phases. After sintering the samples presented relative densities greater than 98.5%, regardless of the amount of the Y-TZP additions used. Furthermore, the monoclinic phase was reconverted into the tetragonal phase during sintering. The Vickers hardness varied between 1750 and 1690 HV, depending on the amount of Y-TZP added. Bending strength and fracture toughness were also sensitive to the addition of Y-TZP, with values increasing from 351.5 to 701.7 MPa and K_IC from 3.5 to 5.6 MPa.m^1/2, indicating that the t-ZrO₂ grains enable the activation of the transformation toughening mechanisms such as t→m phase transformation and residual stress. The biological responses of the composites, evaluated by their cytotoxicity and chemical solubility, accredit the materials developed for future in vitro and in vivo studies aimed at application as biomaterials.

Keywords:
bioceramics; Al₂O₃/Y-TZP composite; orthopedic medicine; mechanical properties