The porosity and roughness of electrodeposited calcium phosphate coatings in simulated body fluid

Calcium phosphate coatings were electrochemically deposited on titanium from the aqueous solution of Ca(NO3)2 and NH4H2PO4 with the current density of 10 mA cm-2 for deposition time of 15 min. The obtained brushite coatings, (CaHPO4?2H2O), were converted to hydroxyapatite (HA) by soaking in simulated body fluid (SBF) for 2, 7 and 14 days. The brushite and hydroxyapatite coatings were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and atomic force microscopy (AFM). It was shown that the increase in soaking time increases the porosity, roughness and crystallite domain size of HA coatings and decreases the unit cell parameters and unit cell volume, while does not affect the HA mean pore area. The calcium and phosphorus ions concentrations in SBF were determined by atomic absorption spectroscopy (AAS) and UV-Vis spectroscopy, respectively and the mechanism of HA growth based on dissolution-precipitation was proposed.