| Preparing hydroxyapatite(HA)bio-coatings on titanium alloy surface is one of hot spots on the study of artificial bone implants,which combines the good mechanical property of titanium alloy and the good biocompatibility of hydroxyapatite.However,because of the big difference of coefficient of thermal expansion between titanium alloy and hydroxyapatite,the bonding strength of the substrate and coating is very low,and in some friction force area the coating is very easy to fall off as a result of the stress fatigue.In order to improve the situation, bioactive glass(BG)and HA composite bio-coatings were coated on a titanium substrate which was prepared by micro-arc oxidation treatment using a sol-gel method.In this study a good bonding strength TiO2 layer was obtained by pretreatment,then we added a BG layer as a transition layer between HA layer and TiO2 layer to accommodate the coefficient of thermal expansion.The reasons why designed such composite coating were that the BG coating of controllable element can lower internal stress among coatings,and its good strength and wear resistance fited for implantation of biomaterial.This article focused on the sol-gel process parameters on the performance of coating.The result indicated that:the ratio of EtOH/TEOS in sol was about 5,the BG2 is appropriate element,the optimum concentration of reactant were 1mol/L P2O5-CH3CH2OH solution and 2mol/L Ca(NO3)2·4H2O-CH3CH2OH solution,the heat treatment temperature of the coating was 800℃.Through theoretical analysis and experimental verification,adding the proper amount of the complexing agent and aging above 24h could guarantee the stability of sol;the viscosity of the sol was about(1.0～5.0)mPa·S and dragging speed was about 4～10cm/min could guarantee the uniformity of sol.The microstructure,surface morphologies,phases and chemical compositions of the coatings were analyzed by scanning electron microscopy(SEM),X-ray diffraction(XRD)and energy dispersive spectrometry(EDS),the bonding strength of the coatings was analyzed by nick apparatus.The result indicated that:the composite coating was uniform and dense,which contained 100-200nm grains and 30～40nm micropore;the bonding strength between the substrate and coatings was formed not only the mechanical interaction but also some metallurgical bonding,there were two stable phase,Ca2SiO4 and P3Ti5.It could strengthen the bonding force,which reached about 45N.The dissolvability test was finished cooperating with Fourth Military Medical University. The result indicated that dissolution rate of the composite coating was moderate,and after soaking HA and HCA were obtained in SBF which belong to the main inorganic substance in natural bone.This suggested that the possibility of extending the planting life by this composite coating.
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