Sol-gel Preparation And Properties Of Fluoridated Hydroxyapatite Films

Hydroxyapatite (Ca₁0(PO₄)₆(OH)₂, HA) is a kind of medical biomaterials with outstanding bioactivity, which has been widely applied to modifying the surface performances of metallic implants for repairing hard tissues. However, a relatively fast degradation speed of hydroxyapatite in human bodies will finally lead to the deteriorating of performance of the implants. We could reduce the solubility of hydroxyapatite by adding a small amount of fluorine, which will be used to replace the hydroxyl in the hydroxyapatite to form fluoridated hydroxyapatite (FHA), but with no change in crystalline structure. In addition, with the special function to stimulate the propagate of bone-forming cells and to refrain the growth of the bone broken cells, the zinc functions well in improving the bioactivity of materials. With that we could say the Zn-doped FHA films will have a very good prospect.In this work, the mixture of ethanol solutions of HPF₆ and Zn(NO₃)₂ 6H₂Ois used as dipping-liquid, the Zn-doped FHA films with different content of zinc on the titanium alloy substrates are prepared by sol-gel technology.This thesis also carries on the research on the relevant performances of fluoridated hydroxyapatite.During the experiment, by adopting the technologies like XRD, XPS, SEM to make analysis of the components and surface appearance of film phase derived from the experiment and the impact of zinc on the existence of fluorine in the films. By soaking the film with the simulated body fluid (1.5SBF) to evaluate the level of biological activation of Zn-doped FHA films.The results obtained in this thesis are as follows:Through changing the Ca/Zn ratio in the film liquid can get the film materials with different content of zinc. Through SEM technology, with the increase of zinc, the surface of film will become coarse, porous and with more cracks.Through XRD analysis, it is found that there are two phases in Zn-doped FHAfilm, namely hydroxyapatite and tricalcium phosphate. It seems that zinc inclines to enter into tricalcium phosphate and, to a certain extent, the existence of zinc has suppressed the crystallization of the hydroxyapatite, which helps the zinc largely colleted on the surface to release in the body, thus to stimulate the growth of bone cells.By soaking the film with different content of zinc in 1.5SBF solution for some time, the surface of film will be covered by the deposition of apatite. With the increasing of zinc, the distributing density of apatite that deposits on the film will become large accordingly. It shows that the increase of zinc content can well suppress the crystallization of the apatite, thus help to release zinc in the body fluid environment, promote the bone to grow, and improve the biological activation of the film material. At the same time, the hydroxyl apatite can be well covered on the surface of the film, which also indicates that Zn-doped FHA film have the same biological activation with fluoridated hydroxyl apatite.The Zn-doped FHA film derived from the experiment shows the sound physical and chemical properties and good bioactivity. Thus, the results throughout the work are of directive significance both theoretically and practically.