Surface Nanocrystallization And Biocompatibility Of Titanium

Titanium is one of the most widely used materials for the implant in medical techniques due to excellent anticorrosion properties and bioactivity. However, its poor mechanical properties were the most serious obstacles for application in load-bearing implants. Increasing the hardness and wear resistance of titanium had received considerable interests in recent decades.In this work, we prepared a nanostructured surface layer on a pure titanium sample by means of a surface mechanical attrition technique. The structure and performance in such layer were examined. And then the biological behaviors of the samples after nanocrystallization were investigated in comparison with those in the original materials.Samples were characterized by means of X-ray diffraction (XRD), transmission electron microscope (TEM), scanning electron microscope (SEM), microhardness tests and profile tests. The main results include:Experimental evidences showed that a nanocrystallization layer and a severely deformation layer were obtained in the surface of pure titanium sample by using surface mechanical attrition. The grains on the top nanostructure layer were in the range of 6-33 nm with random crystallographic orientations. The thickness of deformation layer increased with increasing treatment time.After ball-milling, the hardness of the surface layer increased siginificantly, which value reached to 8.0 GPa, much larger than that of conventional titanium. The depth of effective hardened layer attained 30μm. The roughness enhanced after surface mechanical attrition.The osteoblast-like cells were seeded on different titanium discs for biological experiment. The results showed that surface mechanical attrition effectively facilitates the biocompatibility of titanium. The adhesion and proliferation of osteoblast were significantly greater on nanocrystalline surface than that on original Titanium surface. The ALP activity and OC production on the surface of nanostructured Titanium were also enhanced in comparison with that on original titanium surface.