Influence of applied voltage on the structure of micro-plasma oxidized titania-based coatings formed in an electrolyte containing nano-HA and calcium salts and phosphate

In this work, porous titania-based coatings containing Ca and P ions were prepared on titanium alloy by micro-plasma oxidation (MPO) in an electrolyte containing nano-HA, calcium salts and phosphate under various applied voltages (200-450 V). The results showed that the MPO coatings formed at 250-450 V were composed of anatase and amorphous phase. With increasing applied voltage, the micropore size and thickness of the MPO coatings increase, while the micropore number decreases. Furthermore, the Ca and P concentrations, as well as atomic ratio of Ca/P are highly dependent on the applied voltage. In addition, the cross-sectional view results showed good adhesion between the MPO coatings and titanium alloy substrate at various applied voltages. In vitro experiments indicated that the MPO coating can induce apatite formation.