Study Of Surface Biological Activation For Ti-25Nb-2Zr Alloy

It is well known thatβ-Ti alloys combine excellent mechanical properties, biocompatibility, and lower modulus of elasticity, which draw much more attention. In this study,β-Ti-25Nb-2Zr(at%) alloy developed by our group was experienced surface biological activation treatment.Ti-25Nb-2Zr alloy was first undergone oxidization treatment in air and subsequently immersed in 1.5 SBF for biomimetic growth of Ca-P layer. The oxide layer and Ca-P layer on the surface of the alloy were analyzed and characterized by SEM, AFM, XRD, FT-IR and XPS. The results show: after oxidation at 300℃and 400℃in air, an oxide layer composed of metastable Ti_xO_2x-1 and poor crystallized anatase TiO₂ were formed on the alloy surface; when oxidized at 500℃, similar prism-shaped nanometer rutile TiO₂ with relatively higher crystallinity and small amounts of Nb₂O₅ and ZrO₂ were obtained, which possesses apatite inducing ability; at 600℃, besides similar rutile oxide layer appeared on the alloy surface,αphase also precipitated in the alloy; for the 500℃oxidized alloy, the Ca-P layer got thicker and its crystallinity got better as time went by; the microstructure changed from granule to short bar, long bar and eventually into interconnected network and (002) was the preferred growth orientation. The Ca-P layer after immersed 3 day in 1.5SBF was HA containing CO₃^2-, i.e. bone-like apatite, which means such Ca-P layer might greatly improve the bioactivity and biocompatibility of the alloy. In addition, pre-calcification treatment before biomimetic growth for the alloy could enable the formation of initial nucleus for Ca-P layer, which will consequently provide preferential nucleation sites for the biomimetic growth of apatite layer, and facilitate the heterogeneous nucleation and growth of the apatite crystals.