Structure and bioactivity of micro-arc oxidized zirconia films

Zirconia films have been prepared by micro-arc oxidation (MAO) of zirconium in an aqueous solution using a pulse power supply. Surface morphology, element composition, phase components, bond strength and bioactivity of the films are investigated as a function of the applied voltage in the range of 350-500 V. The obtained results show that the MAO-formed films are porous, and composed of CaO partially stabilized zirconia (e.g. Ca-PSZ with a composition of Ca_0.15Zr_0.85O_1.85) and a small amount of monoclinic ZrO₂. The Ca-PSZ content and pore sizes of the films tend to increase with the increase of the applied voltage. The bond strengths, evaluated by adhesion-tension tests, are 41.9 ± 1.6 MPa for the film formed at 500 V and more than 57.4 ± 2.1 MPa for the films formed at 350-450 V. After immersion in the modified SBF solution for 3 days, the zirconia films are fully covered by apatite layers, exhibiting good bioactivity.