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.