Coating Characteristic of Hydroxyapatite on Titanium Substrates via Hydrothermal Treatment

Medical pure titanium (Ti) shows excellent chemical stability and mechanical properties in clinical uses, but its initial fixation with host bone, when implanted, is usually delayed owing to the bioinert Ti surface. In this study, we fabricate the hydroxyapatite (HA)-coated titanium by three steps reactions: (1) to form an activated O2− layer by immersing Ti substrate into an alkaline solution such as NaOH; (2) the O2− bonds with Ca2+ to form Ca–O–Ti bonding, in which O plays the part of bridge materials between Ca and Ti substrate and (3) the conversion of Ca–O–Ti samples to HA-coated Ti samples by immersion into Na2HPO4 2 M at 180 °C for 48 h using hydrothermal methods. The effect of different phosphate solutions (NaH2PO4 2 M and Na2HPO4 2 M solution) and hydrothermal treatment time (24 and 48 h) on the characteristic of hydroxyapatite coating titanium substrate is also investigated using the optical microscope, thin film XRD and SEM/EDX. The HA-coated Ti samples fabricated by immersion into Na2HPO4 2 M at 180 °C for 48 h show fiber HA covering Titan substrate with a diameter varying from 0.1 to 0.3 µm. These HA-coated Ti samples can be regarded as promising multifunctional biomaterials.