Bioactivity of zirconia nanotube arrays fabricated by electrochemical anodization

Zirconia nanotubes with a diameter of 50 nm and a length of 20 μm were fabricated by anodic oxidation of zirconium in (NH₄)₂SO₄ electrolyte containing NH₄F. The structure and phase composition of the zirconia nanotube layers were characterized by scanning electron microscopy (SEM), transmission electron microscope (TEM) and X-ray diffraction (XRD). The bioactivity was assessed by investigating the formation of apatite on the surface of zirconia nanotubes after soaking in simulated body fluids (SBF) for 20–30 days. The results indicate that bone-like apatite can be formed on the surface of the zirconia nanotube layers in our SBF immersion experiments. Microstructure of zirconia nanotubes with apatite layer was observed by SEM. Substance and phase compositions were characterized respectively by energy dispersive X-ray spectrometer (EDS) and XRD. Our results show that zirconia nanotube layers fabricated by electrochemical anodization exhibit favorable bioactivity.