Preparation and characterization of silicon-substituted hydroxyapatite coating by a biomimetic process on titanium substrate

A biomimetic method has been used to prepare silicon-substituted hydroxyapatite coatings on titanium substrates. The surface structures of the coatings were characterized by X-ray diffraction, X-ray photoelectron spectroscopy (XPS) and Fourier transformed infrared spectroscopy (FTIR). Si substituted hydroxyapatite (Si–HA) coatings with different Si contents were deposited successfully on the titanium substrate by immersing the pretreated titanium substrate into silicon containing supersaturated solutions (SSS) with different SiO32− concentrations. The pretreatment of the Ti substrate in a mixed alkaline (NaOH + Ca(OH2)) followed by a heat treatment produced a 3D porous surface structure with rutile and CaTiO3 as main phases, which contributed mainly to the fast precipitation and deposition of Si–HA. FTIR results showed that Si in the Si–HA coating existed in the form of SiO44− groups. The cross-section microstructure was observed by scanning electronic microscopy and the shear strength was tested. The coating was about 5–10 μm in thickness and no interval was observed at the interface between the coating and the substrate. Shear strength testing showed that Si–HA/Ti exhibited higher shear strength than HA/Ti due to the existence of the SiO44− group in the coating.