Synthesis And Characterization Of Fluor-hydroxyapatite And Mesoporous Hydroxyapatite Coatings On Titanium Substrate By Sol-gel Method

As a kind of biomaterials, the composite material capping hydroxyapatite coating on titanium substrate has broad development prospects. At first, titanium is widely used in orthopedic surgery because of its high mechanical strength and low elastic modulus. Besides, the hydroxyapatite coating on the surface of titanium can provide bioactivity for metal material. Thus, we can get the composite material combining the good mechanical strength and bioactivity. However, the hydroxyapatite coating’s high solubility leads to its premature failure in the body. Therefore, the improvement of the performance of hydroapatite coating to make it meet the requirements of clinical application has important significance.Nowadays, sol-gel techniques are widely used due to their many advantages, such as the high chemical homogeneity of the resultant coating, being both economical and technically simple as well as easily preparing coating at the complex surface, etc. In this study, fluor-hydroapatite and mesoporous hydroapatite coatings were synthesized on titanium by sol-gel method. Meanwhile, the chemical properties and bioactivity of the coatings were investigated. The obtained results are listed as follows.Fluor-hydroxyapatite coating was prepared by using calcium nitrate as the calcium source, diethyl phosphite as the phosphorus source, 1-butyl-3-methylimidazolium tetrafluoroborate as the fluorine source at room temperature by sol-gel method. All the synthesized hydroxyapatite (HA) coating and fluor-hydroxyapatite coatings with different fluorine proportion (25FHA,50FHA,75FHA) possess good crystal structure after heat treatment at 500℃, and the coatings are homogeneous without crack. The in vitro test results by simulated body fluid soaking method show that all of the 25FHA,50FHA and 75FHA coatings have good bioactivity, showing the formation of bone-like apatite. Especially the 25FHA coating, its thickness of bone-like apatite particles deposited on the coating reached to 650 nm after soaked in SBF for 24 h.Mesoporous hydroapatite coating was prepared by using calcium nitrate as the calcium source, diethyl phosphite as the phosphorus source, hexadecyl trimethyl ammonium bromide (CTAB) as the template at room temperature by sol-gel method. For all the synthesized mesoporous hydroxyapatite coatings with different CTAB proportions (CTAB1, CTAB2, CTAB3, CTAB4), CTAB was decomposed below 400℃ and led to the nano mesoporous structure of the coatings. After heat treatment at 500℃, the resultant coatings have good crystal structure without crack. The in vitro test results by simulated body fluid soaking method show that the CTAB3 and CTAB4 coatings are bioactive. The thickness of bone-like apatite deposited on the CTAB3 coatings reached to 300 nm after soaked in SBF for 24 h.