Study On The Porous Bioactive Titanium For Medical Materials

Titanium is a main metal material applied to the clinic due to its good biocompatibility, mechanical property and corrosion resistance. In recent years, researches on porous titanium have gained much attention, because porous titanium has certain bearing capacity whose porous structure benefits for biological tissue to grow into. But how to obtain the porous titanium with controlled porosity and excellent surface activity requires further studies.Porous titanium was prepared by powder metallurgy and ammonium hydrogen carbonate was selected as pore former in this paper. The surface of porous titanium was modified by alkaline solution and heat treatment. Bioactivity was studied by simulation test in vitro. The structures and the properties of samples were characterized by means of electron analytical balance, scanning electron microscope (SEM), omnipotence material experiment machine, energy disperse spectroscopy(EDS) and X-ray diffraction (XRD).The effects of ammonium hydrogen carbonate content as well as sintering temperture on porosity and compressive strength of porous titanium were investged. Moreover, the relationship between the porosity of porous body and the content of ammonium hydrogen carbonate was studied systematically. The results showed that the shrinkage of titanium body was treated as the shrinkage of the pore left by ammonium hydrogen carbonate and titanium powder during sintering process. The reciprocal of porosity was expressed as a function of the quality ratio of titanium to ammonium hydrogen carbonate. The shrinkage of the pore left by ammonium hydrogen carbonate and titanium powder increased with sintering temperature heightened. The compressive strength was a power function of the relative density of porous titanium and the power reduced when sintering temperature was enhanced.The results have showed that when the content of ammonium hydrogen carbonate additive was 33.33wt%~63.64wt%, the porous titanium with porosity of 48.54%~77.24% and compressive strength of 19.85~89.86MPa was prepared at 1100℃, 1150℃and 1200℃vacuum sintering. Among them, the porous titanium sintered at 1200℃has relative density of 95% excess, porosity of 48.54%~77.24%, compressive strength of 19.85~89.86Pa and pore size of 50~200μm. The porous titanium prepared had the characteristics of interconnected pore, uniform pore size distribution, controlled porosity and intensity, good repetition.After the surface of porous titanium was modified 24h by 5mol/Lthermal alkaline solution at 60℃, the gel coating of amorphous Rutile and Na2TiO3 with 2μm thickness were formed on the surface of titanium matrix. After the modified porous titanium was treated at 600℃, the amorphous Na2TiO3 translated into crystal Na2TiO3 while amorphous Rutile had no change. The simulation test in vitro showed that plentiful bioactive hydroxyapatite and octacalcium phosphate formed on the surface of the porous titanium modified by thermal alkaline solution and heat treatment after two weeks, which indicated that porous titanium being modified had good biocompatibility and bioaffinity.