Synthesized silicon-substituted hydroxyapatite coating on titanium substrate by electrochemical deposition

Silicon-substituted hydroxyapaptite (Si-HA) coatings were prepared on titanium substrates by electrolytic deposition technique in electrolytes containing Ca(2+), PO(4)(3-) and SiO(3)(2-) ions with various SiO(3)(2-)/(PO(4)(3-) + SiO(3)(2-)) molar ratios (η(si)). The deposition was all conducted at a constant voltage of 3.0 V, with titanium substrate as cathode and platinum as anode, for 1 h at 85°C. The coatings thus prepared were characterized with inductively coupled plasma (ICP), X-ray diffraction (XRD), fourier transform infrared spectroscopy (FTIR), field-emission-type scanning electron microscope (FSEM). The results show that the silicon amount in the coatings increases linearly to about 0.48 wt% at first with increasing η(si) between 0 and 0.03, then increases slowly to about 0.55 wt% between 0.03 and 0.10 and finally maintains almost at a level around 0.55 wt% between 0.10 and 0.30. The tree-like Si-HA crystals are observed in the coatings prepared in the electrolyte of η(si) = 0.20. And the presence of silicon in electrolytes decreases the thickness of the coatings, with effect being more significant as η(si) increased. Additionally, the substitution of Si causes some OH(-) loss and changes the lattice parameters of hydroxyapatite (HA).