Surface characteristics of hydroxyapatite coatings on nanotubular Ti-25Ta-xZr alloys prepared by electrochemical deposition

The surface characteristics of hydroxyapatite coatings on nanotubular Ti-25Ta-xZr alloys prepared by electrochemical deposition for dental implants have been investigated using various methods. The Ti-25Ta-xZr alloys were prepared by an arc melting furnace, homogenized for 12 h at 1000 °C in an argon atmosphere, and then water-quenched. Nanotubular structures were formed by an electrochemical method in 1 M H3PO4 electrolytes containing 0.8 wt.% NaF. Electrochemical deposition was carried out using a cyclic voltammetry method over a potential range of − 1.5 V to 0 V at 80 °C in a 5 mM Ca(NO3)2 + 3 mM NH4H2PO4 solution. Surface characteristics were observed by optical microscopy, X-ray diffraction, field-emission scanning electron microscopy, energy-dispersive X-ray spectroscopy, contact angle goniometer, and image analyzer software. Microstructures of the Ti-25Ta-xZr alloys changed from α″ phase to β phase, and the phases changed in morphology from a needle-like to an equiaxed structure with increasing Zr content. The arrangement of nanotubes changed from an irregular distribution to a high level of ordering surrounded by smaller tubes, and the occupied percentage of pore wall surface decreased from 28% to 23%, as the Zr content increased. HA precipitates also changed in morphology from a plate or leaf-like shape to a needle or flower-like shape as the Zr content increased.