Surface Modification Of Titanium Matrix Biomedical Material And Simulated Body Fluid Cultivation

Biocompatibility is one of the most considerable problems in the study of Ti matrix biomedical material. The surface of Ti matrix was modified to improve its biocompatibility in this study. Bioactivity of the material after surface modification was evaluated through the simulated body fluid (SBF) cultivation experiment. Surface morphology, phase constitution and biocompatibility of the material were analyzed and evaluated in this paper.Ti alloys were produced by vacuum induction smelting furnace and non-consumable vacuum arc smelting furnace respectively. The structure, composition and property of Ti alloys were analyzed. The matrix was badly contaminated by carbon and oxygen in graphite crucible or CaO coating crucible, so it was found that the contents of carbon and TiC particles were high. CaO coating crucible reduced the carbon contamination to Ti alloy. But the oxygen contamination in high temperature and the unstable technology make it impossible to fabricate Ti alloy with even normal property. The structure character of cast Ti alloy produced by non-consumable vacuum arc smelting furnace was studied. The Effects of the addition alloying elements on the structure and the asymmetry law of the addition elements were also analyzed.In order to get a ceramic layer with biocompatibility on the surface of Ti matrix, the processing technique of potassium titanate (K2O-6TiO2) was researched. Effects of K2CO3/TiO2 ratio and reaction temperature on purity and growth of the whisker were analyzed. The results indicate that while the K2CO3/TiO2 ratios is about 1:5.5-1:6, the high quality and high productivity potassium titanate whisker is synthesized by calcination method at applicable reaction temperature. The diameter of whisker is about 0.1-0.3um and the length to diameter ratio is about 100-200. According to the processing technique of the whisker, Potassium titanate coating was in situ synthesized on the surface of titanium. The coating was made up of potassium titanate whisker in orientation, perpendicular to the surface of the matrix. The coating thickness was about 2-3um. The surface oxidation of matrix participated in the in situ synthesis reaction. The effect of the reaction mode thatsolid phase formation and liquid, gas phase escaping happen synchronously on potassium titanate whisker's growth in orientation were analyzed. Bioactivity of the potassium titanate coating was evaluated through the simulated body fluid (SBF) cultivation experiment. After cultivation for some days, calcium-phosphorus layer was not found. The primary reason is that the low chemical activity of potassium titanate for its tunnel crystal structure and cannot adsorb calcium-phosphorus ions almost. In addition, the smooth coating surface with high surface energy makes it difficult for the solute to nucleate and grow up.The surface porous titanium was fabricated by using oxidation stratification for the thermal stress and growth stress between the coating and the base. The porous surface was modified using simplified acid-alkali treatment method. The mechanism of porous titanium and activity reaction were studied. The result was showed that the partly connected pores' orientation is related to the microstructure of titanium base. The pores' diameter is about 10-40um and the depth is about 10-15um. After SBF solution cultivation for some days, the Ca/P coating was very easily deposited on the porous surface that was constituted of cystiform polygon made up with irregular nanometer circles like honeycomb. The energy spectrum showed that n(Ca)/n(P) atom ratio is about 1.61:1 which is very similar to that of HA and human bone. The active surface of the porous titanium after acid-alkali treatment and SBF solution condition which calcium-phosphorus ions was supersaturated induced the formation of Ca/P deposition layer.