| Porous Ti-based metallic materials were fabricated by powder metallurgy. The effects ofpowder metallurgy process and addition of Ag, Si element on the microstructure, mechanicalproperties, biological activity, biological safety of the Ti-based metallic materials, weresystematically investigated. The powders of titanium, Ti-Ag mixed powder and Ti-Si mixedpowders were obtained by planet milling. With urea particles as the space-holder, the porousTi-based metallic materials were sintered at high temperature under Ar atmosphere. Alkalitreatment was introduced to modificate the surface activation of the porous Ti-based metallicmaterials. The apatite-inducing ability was evaluated by simulation body fluid (SBF)immersion test. The particle sizes, microstructure of powders were investigated by scanningelectron microscope (SEM), X-ray diffraction (XRD), laser particle size analyzer. Themechanical properties of porous Ti-based metallic materials were revealed by compressiontest. porosity characteristics, microstructure of prous Ti-based metallic materials before andafter alkali treatment, as well as the apatite growth after soaking in the SBF, were investigatedby scanning electron microscope (SEM), X-ray diffraction (XRD), X-ray photoelectronspectroscopy (XPS), Fourier transform infrared spectrum (FT-IR). The cytotoxicity of porousTi-based metallic materials was evaluated by the MTT method.The average particale size and ratio of surface area to volume of the titanium powderswith different milling time (1h,5h,10h), varied respectively from29.25μm to1.84μm andfrom0.24m~2/mm~3to3.90m~2/mm~3. With the increase of the ball milling time, titaniumparticles were refined with less particle size and higher ratio of surface area, as well as thegrain size of titanium particle more finer. The efficiency of ball milling process would be thehighest for5hours’ balling time, and be lower with more ball milling time. Titanium powderswere consisted of α-Ti phase particles. The pore size, porosity, elastic modulus andcompressive strength of the porous titaniu materials fabricated by the different titaniumpowders, varied respectively from200μm to500μm, from46.5%to66.5%, from0.9GPa to1.9GPa, from15.7MPa to61.9MPa. With the increase of the ball milling time, the pore sizeand the porosity of the porous titanium mateials decrease, but the elastic modulus and thecompression strength increase. Porous titanium materials consist of α-Ti phase and TiO phase, with longer ball milling time of titanium powders more TiO formed and higher oxygencontent at the porous titanium surface.The average particale size and ratio of surface area to volume of the Ti-Ag powders withdifferent Ag content (1wt%,3wt%,5wt%) after5hours’s milling time, variedrespectively2.08μm to2.13μm and from3.37m~2/mm~3to3.46m~2/mm~3. It was helpful torefining powder particle size that a small amount of Ag (1-5wt%) was added to the mixtureof titanium powders. The Ti-Ag powders were consisted of α-Ti phase particles and Agparticles with uniform distribution. No reaction happened during the balling milling process,but a lamellar complex mechanical mixing Ti-Ag structure was formed in the powders. Thepore size, porosity, elastic modulus and compressive strength of the porous Ti-Ag materialsfabricated by the different Ti-Ag powders, varied respectively from200μm to500μm, from57.8%to59.5%, from1.2GPa to1.5GPa, from27.9MPa to32.8MPa. Porous Ti-Agmaterials consist of α-Ti phase and TiO phase. With Ag content increasing, the pore size andthe porosity of the porous Ti-Ag materials decrease, but the elastic modulus and thecompression strength increase.The average particale size and ratio of surface area to volume of the Ti-Si powders withdifferent Si content (1wt%,3wt%,5wt%) after5hours’s milling time, varied respectivelyfrom1.94μm to2.11μm and from3.40m~2/mm~3to3.69m~2/mm~3. It was helpful to refiningpowder particle size that a small amount of Si (1-5wt%) was added to the mixture oftitanium powders. The Ti-Si powders were consisted of α-Ti phase particles and Si particleswith uniform distribution. No reaction happened during the balling milling process, but alamellar complex mechanical mixing Ti-Si structure was formed in the powders. The poresize, porosity, elastic modulus and compressive strength of the porous Ti-Si materialsfabricated by the different Ti-Si powders, varied respectively from100μm to500μm, from46.2%to55.8%, from1.6GPa to2.0GPa, from35.9MPa to58.2MPa. Porous Ti-Simaterials consist of α-Ti phase, Ti3Si5phase and TiO phase. With Si content increasing, moreTi3Si5formed, the pore size and the porosity of the porous Ti-Si materials decrease, but theelastic modulus and the compression strength increase. Porous Ti-base material prepared inthis strudy, meet requirements of pore and mechanical performance from human body bonesubstitute materials.The pores are intrudeced to reduce the elastic modulus of the porous Ti-based materials for matching with the elatic modulus of bone tissue, but also lead to significant reduction ofmechanical properties. There are large differences of porous Ti-based materials prepared bydiference methods and process parameters. The experiment results show that the mechanicalproperties of porous Ti-based materials prepared by the powders with longer milling timewould be better to meet requirements of mechanical performance from human body bonesubstitute materials, but more impurities brought to the porous Ti-based materials. Theaddition of Ag element could improve the mechanical properties of porous Ti-based materials,but it is limited for the presence of the microns wide hole in the cell wall. The addition of Sielement could improve significantly the mechanical properties of porous Ti-based materials,which effectively promoting the titanium powder sintering process through strong diffusionreaction.After alkali treatment, activation layer of micro/nano network structure was formed onthe surface porous Ti-base materials which could improve the Ti-base materials biologicalactivity. It was indicated by the results of the simulated body fluids soaking experiment. Thenucleation ability of apatit on the porous titanium surface, fabricated by the titanium powderwith longer ball milling time, would be stronger. Thus, porous titanium fabricated by thetitanium powder with longer ball milling time would show better apatite-inducing ability.With Ag content increase, the nucleation ability of apatite on the porous Ti-Ag materialssurface would be weaker. Thus, addition of Ag would reduce the apatite-inducing ability ofporous Ti-based materials. With Si content increase, the nucleation ability of apatite on theporous Ti-Si materials surface would rise. Thus, addition of Si would increase theapatite-inducing ability of porous Ti-based materials.The cytotoxicity experiment results show that the porous Ti-base materials prepared bypowder metallurgy have good biological safety. The cytotoxicity of porous titanium, porousTi-Ag and porous Ti-Si materials was below grade1. Alkali treatment has no evident effecton the porous titanium cytotoxicity, and a little negative effect on the Ti-Ag and porous Ti-Simaterials. |
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