Evaluation of the hydroxyapatite film coating on titanium cathode by QCM : Biomaterials and bioengineering

A titanium substrate was coated with a hydroxyapatite (HA) film under a cathodic potential in aqueous solutions containing calcium and phosphate ions and hydrogen peroxide at pH 5.5 and a temperature of 309.5 K. The deposition process was monitored using the current density change, and the mass change was measured using the electrochemical quartz crystal microbalance (QCM) technique at cathodic potentials, and compared with deposition on a gold substrate. The deposits were analyzed using X-ray diffraction and scanning electron microscopy. HA films were obtained at different cathodic potentials, and the film morphology changed with the potential. With electrolysis at -557 mV, HA was deposited and accumulated after 800 s, when the mass gain increased significantly, as determined using QCM. After 800 s, the cathodic current increased and then decreased with HA growth. The HA film was porous, with pores several hundred nanometers in size, and formed a network of aggregates with walls about 50 nm thick. The filling factor was about 59 vol%, as evaluated from the mass gain using QCM and microscopic observation.