Preparation Technology,Mechanical Behavtor And Biological Research Of Channel-like Porous Titanium

Porous titanium is an ideal embedded material in orthopedics,and has a great application prospect in the field of bone transplantation and repair.It still remain many problems in the structure controllability,mechanical properties,biological properties,cost for the porous titanium fabricated by the mainstream technologies.Therefore,it is necessary to develop a kind of porous titanium with controllable structure and good performance.Infiltration casting and selective etching technology is first used to fabricate the porous titanium.The titanium liquid is cast into the entangled molybdenum wires in a vacuum environment,and then the molybdenum wires are removed by selectively dissolving in an special corrosion solution.In the research process,some testing methods,such as stereo microscope,optical microscope,scanning electron microscope,X-ray diffractometer,Micro-CT and universal material testing machine,are used.The results show:The preparation efficiency of porous titanium can be improved by optimizing the ratio of reagents in mixed liquid.The inner pores of porous titanium exhibit unique channel-like structure with uniform pore size.Pore orientation,porosity and pore size of porous titanium can be precisely controlled.Pore orientation,porosity and pore size have a regular effect on the mechanical properties of porous titanium.The compressive yielding strength of transverse,quasi-ordered,oblique 45 o and vertical pores increases in turn,but the elastic modulus of quasi-ordered porous titanium is obviously lower than that of other three types of porous titanium.With the increase in porosity,the compressive,tensile and bending strength and elastic modulus decrease.With the increase in pore size,the compressive,tensile and bending strength and elastic modulus increase.The channel-like structure improves the mechanical properties of porous titanium.The main failure modes in the compression process are upsetting,plastic bending,buckling deformation,rotational bending and slipping of the pore walls.The main failure modes in the tensile process are longitudinal fracture,transverse fracture,rotational failure and slipping of the pore walls.The stress concentration results in different mechanical properties of porous titanium with different pore orientations.According to the stability theory of compression bar,with the increase in porosity,the critical length of unstable "channel-like tube" decreases,the proportion of unstable "channel-like tube" increases,and the probability of failure for porous titanium increases.With the increase in pore size,the critical length of unstable "channel-like tube" increases,the proportion of unstable "channel-like tube" decreases,and the probability of failure for porous titanium decreases.Pore structure is a major factor affecting the compressive strength of porous titanium.The smaller the roundness of pore structure,the larger the power exponent in the strength-density equation of porous titanium,and the smaller the compressive strength.After being treated by 20 wt.% HCl,the surface roughness value of porous titanium is increased,meanwhile,the surface activity and the proliferation of MG-63 myeloma cells are improved.In contrary,the strength of the porous titanium decreases monotonically with etching time.Considering the dual influence of the etching treatment on cell response and strength,a proper etching time is 60 min.The channel-like structure improves the biological properties of porous titanium.The quasi-ordered porous titanium has the best osteoconduction when the pore size is 0.4 mm within the range of porosity of 40% and pore size of 0.3 mm-0.5mm.The quasi-ordered porous titanium modified by acid etching for 60 minutes with porosity of 40% and pore size of 0.4 mm has a good application potential in the field of artificial bone implantation.