Preparation of hydroxyapatite/zirconia bioceramic nanocomposites for orthopaedic anddental prosthesis applications

Abstract

Homogeneous mixtures of hydroxyapatite (HAp) and yttria-stabilized zirconia (YSZ)nanoparticles were successfully synthesized using chemical co-precipitation and subsequentcalcination. For the synthesis of HAp/YSZ nanopowder, the Ca/P atomic ratio was1.73 to obtain high-content stoichiometric hydroxyapatite phase and to suppressβ-tricalciumphosphate (β-TCP) formation. The agglomerated crystalline powders were milled using YSZ ball mediato obtain well-separated nanoparticles. The final particle size of the HAp and YSZ was∼50–70and ∼15–30 nm, respectively. The crystallinity and morphological feature of the nanopowder wasanalysed using x-ray diffraction (XRD) and high-resolution transmission electronmicroscopy (HRTEM) analyses. The ball-milled nanopowder mixture was hot pressed at1100 °C for 1 h under 20 MPa in vacuum atmosphere. The sintered HAp/YSZ nanocomposites exhibitedapproximately 99% of the theoretical density, due not only to the fine nanoscale of theparticles, but also to the homogeneous distribution of the nanoparticle mixture. They alsoshowed fine grain structures of the HAp phase due to the suppressed grain growth by YSZparticles. The nanocomposites showed improved mechanical properties, flexural strength of∼155 MPa and fracturetoughness of ∼2.1 MP m1/2, due to the YSZ contribution to the HAp matrix.