Study On Zinc-substituted Hydroxyapatite Powders And Coatings

Zinc-substituted hydroxyapatite[Ca_10-xZn_x(PO₄)₆(OH)₂, Zn-HA] as a modified materials of hydroxyapatite[Ca₁₀(PO₄)₆(OH)₂, HA] has a good bioactivity and biocompatibility. However, because of a brittle material of Zn-HA which is limited as the application of bone substitute materials. So, it must be used with traditional biomedical metallic materials, and the strength of component materials in the structural system is satisfactory for medcine. In this paper, we mainly studied on the synthesis of Zn-HA and the coatings on anodized titanium substrate.Firstly, nanometer Zn-HA materials were fabricated by hydrothermal and sol-gel methods. X-ray fluorescence spectroscopy(XRF), X-ray diffraction(XRD), Fourier transform infrared spectroscopy(FTIR), Transmission electron microscopy(TEM) and Thermogravimetryand differential thermal analysis(TG-DTA) were used to characterize Zn-HA. The results show that the substitution of the zinc ions for the calcium ions caused the change of lattice parameters of HA, furthermore, the substitution of the zinc ions restrained the growth of Zn-HA crystal. XRD and TG-DTA analysis show that zinc incorporated into HA lattice decrease the thermal stability of HA.Secondly, the highly-ordered TiO₂ nanotube arrays were fabricated by potentiostatic anodization of Ti foil. Scanning electron microscopy(SEM), Energy dispersision X-ray spectroscopy(EDX), XRD, FTIR and TEM were used to characterized TiO₂ nanotube arrays. The thermal stability and the biactivity of TiO₂ nanotube arrays are also discussed. The results show that the highly-ordered TiO₂ nanotube arrays were fabricated by potentiostatic anodization of Ti foil. The as-prepared nanotubes are amorphous but crystallize with annealing at elevated temperatures. Anatase phase appears after heat-treated at 300℃and the pore diameter of TiO₂ nanotubes arrays begin to constriction. The TiO₂ nanotublar structure takes place collapse at 600℃and is destroyed completely at 700℃. The structure of TiO₂ nanotube changes from anatase to the rutile phase at 600℃. The grain size, crystallinity, lattice parameter and phase contents of TiO₂ at different temperatures are changed. After the annealed titania nanotubes soaked in simulate body fluid for 14d, the thick carbonate apaptite layer about 13μm deposit on its the surface. The study of bioactivity shows that Ti plate forming TiO₂ nanotube arrays on its surface has a good bioactivity.Lastly, the hydrothermal and sol-gel methods are used to prepare hydroxyapatite coatings. The influence of the coating technique conditions on the morphology of coatings was studied, and the phase constitutes and microstructures of coatings were studied too. The results show that the condation at pH=5, 200℃is benefit for HA deposition. The uniform thickness HA coatings can be prepared by sol-gel method.