Preparation of TiO2 Coated Biomedical Porous NiTi Alloys by Sol-gel Method

A uniform anatase TiO2 layer was dip-coated on porous NiTi alloy via the sol-gel route, and a bilayer composite TiO2 coating consisting of the porous outer layer and the dense layer beneath was also deposited on porous NiTi alloy by adding polyethyleneglycol(PEG) in sol as pore-forming agent. The surface morphology of the TiO2-coated porous NiTi alloy and the cross-sectional structure of coatings show that the TiO2 coatings cover not only the outer surface but also the inner surface of porous NiTi alloy. The corrosion behaviors of the samples in Hanks solution at 37 degrees C show that the dense TiO2 coatings increase the corrosion resistance of porous NiTi alloy significantly. In contrast with dense TiO2 coating, the porous TiO2 composite coating can improve the surface bioactivity owing to the increased surface area.