| 其他摘要 | Ti2448 alloy is a new kind of high strength and multi-functional -titanium alloy. This alloy has some desirable properties suitable for biomedical applications, e. g., low elastic modulus, good recoverable elastic strain and energy adsorptivity, high strength and biosaft. However, this alloy is bioinert like other titanium alloys. The naturally formed oxide layer of the alloy can not induce bioactive compound to form on itself. Therefore, in order to meet all the clinical requirements, surface modification should be performed to improve its biological properties. In this work, a micro arc oxidation (MAO) plus heat treatment process is applied to the Ti2448 alloy to form a porous and Ca-contained oxide layer on the surface of the alloy, and then the effects of this process on bioconductiviy, corrosion resistance and histocompatibility, such as ostealblast adhesion, propagation, protein adsorption, are evaluated.
In this research, a micro arc oxidation plus heat treatment process, defined as the MH treatment, is developed. In MAO treatment, acetate calcium aqueous solution is used as the electrolyte; the MAO treatment is performed on a DC power supply with a final working voltage of 250V. And heat treatment is performed at 600 °C for 1 h and then cooled in furnace to room temperature. It shows that the oxide layer is porous and two-layered, which is composed of TiO2, Nb2O5, CaO, SnO2 and TiO2 including rutile and anatase crystal structure. The bonding strength between the oxide layer and substrate is strong. After soaked in simulated body fluid, the oxide layer is covered by apatite on its surface in 7 days. The results indicate that the MH treatment improves bioconductivity of the oxide layer.
A MAO plus alkaline treatment plus heat treatment process, defined as MAH three-step treatment, is developed too. MAO and heat treatment are the same as that mentioned above, while the process of alkaline treatment is that the specimens are soaked in 5M NaOH solution at 60 °C for 24 hours. After this three-step treatment, a networked, porous layer is formed on the surface of the alloy. This layer is composed of Na2TiOx, CaTiO3 and Nb2O5. The MAH treatment further improves the bioconductivity of this alloy.
The corrosion resistance of Ti2448alloy in simulated body environment and the effects of two processes above on this alloy are studied. The corrosion resistance of Ti2448 is better than that of c. p. Ti and Ti-6Al-4V in acid mediums and a medium that contained H2O2 or bovine serum albumin, while is the same as the latter two in neutral and basic mediums. After the MH treatment, the corrosion resistance of Ti2448alloy is significantly improved. The oxide layer mainly consisted of TiO2 and Nb2O5. These two oxides are inert and hardly soluble in corrosive medium, which is beneficial for the corrosion resistance of Ti2448 alloy. The pores structure do not impair the corrosion resistance of the alloy. After the MAH treatment, the corrosion resistance of Ti2448 alloy is also improved, but is not as good as those after the MH treatment.
Finally, the effects of the MH treatment on the histocompatibility such as osteolblast adhesion, propagation, protein adsorption of Ti2448 alloy are analyzed. The number of osteolblast cells propagated on the surface after the MH treatment is larger than that of the untreated one. The pseudopods on the osteolblast cells fasten in the pores and stages It shows that these osteolblast cells are bioactive. The specimens after the MH treatment absorb proteins much easier and much more than the untreated ones. The number of bovine serums albumin adsorbed on the specimens after MH treatment is larger than that of bovine hemoglobins that is beneficial for the bone healing. |
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