Preparation Of Phosphate Conversion And Hydroxyapatite Composite Coating On Biomedical Titanium

Hydroxyapatite(HA)has good biocompatibility and bone conductivity,can provide a physiological scaffold for the growth of new bone and promote the growth of bone tissue,so it is widely used in bone repair.However,hydroxyapatite is basically brittle,and it is easy to crash under the action of external force.The application of hydroxyapatite on the surface of medical metal to synthesize ceramic/metal composite materials has greatly expanded its application.However,after a single hydroxyapatite coating is implanted into the body,it will peel off when subjected to high shear forces.Adding a chemically stable,uniform and dense transition layer between the coating and the metal substrate is expected to enhance the bonding strength of the hydroxyapatite coating and the metal substrate.In this study,a layer of phosphate conversion coating was first prepared on the surface of titanium by hydrothermal synthesis,and then a hydroxyapatite coating was prepared on the surface of the conversion coating.The main research contents and conclusions are as follows:(1)The influence of temperature and time on the phosphate conversion coating on the surface of polished titanium was studied.The experiment showed that the phosphate conversion coating obtained under 12h and 250?had the best morphology;the grains were sharp and angular,the size was the largest,and the coating was dense and uniform.And the roughness of the sample was the largest,the wettability was the best,and the comprehensive performance was excellent.(2)The effect of the pretreatment of the titanium substrate on the phosphate conversion coating was studied.The results showed that the polishing substrate had the best micro-morphology of the conversion coating;in the scratch strength test,the bonding strength of the polishing substrate coating was the largest;the cell compatibility experiments showed that the growth rate of L-929 cells with polished substrate coating was the highest,and the cytotoxicity level was 0,indicating that the biocompatibility was the best and could be applied in the biomedical fiel.(3)The effects of Ca²⁺source,solution p H and Ca Cl₂ concentration on the micro-morphology of hydroxyapatite coating were studied.The results showed that 0.25mol/L pure Ca Cl₂ solution was more conducive to the nucleation and growth of hydroxyapatite,with the best micro-morphology.According to X-ray diffraction analysis,the main components of the coating were hydroxyapatite and titanium dioxide.The sample had the largest roughness and the best wettability.The corrosion resistance of hydroxyapatite composite coating was lower than that of phosphate conversion coating,but better than that of pure titanium.The preparation of the chemical conversion coating made hydroxyapatite and the substrate had a good bonding strength.The experimental results of osteoblasts showed that phosphate conversion coating,especially hydroxyapatite coating,could promote cell adhesion,and osteogenic differentiation.