Preparation Of TiO₂ Film Containing Magnetic Powder On Metallic Substrates And Study On Its Blood Compatibility

With the development of new materials and biologic technology, the biomedical material industry has risen. More and more biomedical materials have been applied in the reality of medical field. However, thrombus would be generated when biomedical materials contacted with blood, which restricted the development of biomedical materials strongly.Thus a new method was suggested to settle thrombus problem in this thesis: micromagnetic field, produced by TiO₂ film coating with magnetic powders, would effect the movement of plasma protein, hemocyte and some ions which with negative charge, so that the adsorbing of these ions on the surface of biomedical materials would be restrained. The execution method:â‘ The SrFe₁₂O₁₉ ultrafine powders were prepared by sol-gel method.â‘¡TiO₂ film containing SrFe₁₂O₁₉ was coated on the surface of NiTi alloy and 316L stainless steel by sol-gel method.â‘¢The effecting of different kinds of substrates and film, different content magnetic powders on the blood compatibility were studied.The formation process, the structure and surface morphology of SrFe₁₂O₁₉ powders, the formation process, surface composition, structure and morphology of the films were studied by X-ray Diffraction(XRD), Transmission Electron Microscope(TEM) and Scanning Electron Microscope(SEM) etc. The magnetic performance of ferrite was measured by HH-15 vibrating sample magnetometer (VSM). The interface adhesive strength between the film and substrate was measured by scratching test. The component and the roughness of film were studied by XRD and surface roughness measuring instrument. The micromagnetic field was tested by CT3 tesla instrument. The corrosion resistance of the films was studied by the number of releasing toxic ions in Simulated Body Fluid (SBF). Additionally, the blood compatibility was primarily evaluated by dynamic clotting time, hemolysis and blood platelet adhesion test.Pure SrFe₁₂O₁₉ magnetice powders with average dimension of 20-50nm were obtained by sol-gel route. The morphologies of powders were hexagon. According to the results calculated by the scherrer formulation, the dimension of grains was 51.06nm which closed to the trim size. The magnetic hysteresis loops of SrFe₁₂O₁₉ were tested. Results indicated that magnetic powders heated at 850℃for lh then heated to 950℃ had good magnetic performance. Coercive force, saturation intensity and residual magnetization of powders mentioned above were 2275.45Oe, 99.95emu/g and 30.39 emu/g respectively.According to optimum process, TiO₂ film containing SrFe₁₂O₁₉ was coated on the surface of NiTi alloy and 316L stainless steel by sol-gel method. Titanium butoxide (Ti(OC₄H₉)₄) was used as the starting material, ethanol as solvent, chlorhydric acid and acetylacetone as additives, respectively. The results showed that crystal structure of TiO₂ film heated at 500℃for lh was anatase. The crystal grains were refined and the film became dense at slow heating speed (1～2℃/min). The results of scratching test showed that the interface adhesive strength between the film coating SrFe₁₂O₁₉ and 316L stainless steel and NiTi alloy substrate is about 27N, 30N, respectively.The results of corrosion experiment indicated that the corrosion of metallic materials by SBF could be reduced by TiO₂ film containing SrFe₁₂O₁₉ on NiTi alloy and 316L stainless steel and the precipitating Ni ion could be prevented. The result of dynamic dotting time test showed that dynamic dotting time of 316L stainless steel and NiTi alloy was increased with TiO₂ film containing SrFe₁₂O₁₉, and the more magnetic powders the better of anticoagulant performance. The TiO₂ film contained SrFe₁₂O₁₉ would have lower hemolysis rate, which would reduce wrecking degree of hemocyte caused by micromagnetic field, and the blood compatibility would be improved. The blood platelet adhesion test illuminated that the film contained SrFe₁₂O₁₉ has good blood compatibility, the number of the blood platelet adhered to film was lower than the surface of the substrate, the filopodium growth of blood platelet is not obvious.