Effects of titanium surface treatment on adhesive properties of hydroxyapatite ceramics coating to titanium substrates by double layered capsule hydrothermal hot-pressing

This report described the effects of Ti surface modification with NaOH hydrothermal solution on adhesion strength of HA coating produced by newly developed hydrothermal (DC-HHP) method. 2 kinds of surface layer (containing anatase-type TiO₂ or not) were formed on Ti surface by immersing to 5mol/L NaOH solution before HA coating process. Pull out tests were conducted to obtain an estimate for the adhesion properties of the HA coating. Shear strength of specimens with 5mol/L NaOH treated at 423K for 2 hours was estimated in the range of 4.1-5.7 MPa. The enhancement of the HA adhesive properties as well as more than three times values was achieved, in comparison to the specimens without the surface layer (approximate 1.5 MPa). It was demonstrated that 423K hydrothermal treatment with 5mol/l NaOH solution on Ti surfaces is significantly effective to enhancing adhesion strength of the HA coating produced by the DC-HHP method.