Fabrication And Mechanical Properties Of Porous Titanium Scaffolds With Directional Lamellar Pore Structure Reinforced By Carbide

Because of the anisotropic pore structure,the directional layered porous titanium scaffolds have higher mechanical strength in a single direction,which has a broad application prospect in bone implant load-bearing materials.When porous titanium is subjected to compression load,the pore wall will be buckling deformation,and the weak interlaminar bonding will lead to interlaminar splitting.Therefore,improving the pore wall strength and interlaminar stability is the key to improve the mechanical properties of the scaffold.In this paper,porous titanium scaffolds with directional straight through structure were prepared by directional freeze-drying combined with in-situ reduction reaction of TiH₂.The pore wall was strengthened by in-situ reaction of TiC by introducing graphene sheets into the pore wall.In addition,carbon fiber is introduced into the interlayer to form a bridging structure,which can constrain the pore wall to improve the interlayer stability.The phase composition,pore structure and the interface between the reinforcement phase and matrix of the porous titanium scaffold reinforced with carbide were studied.After the introduction of graphene sheets,the porous titanium scaffold still shows layered porous structure,and the pore size and porosity decrease.The graphene sheets react with the Ti in the pore wall in situ to form titanium carbide,which is well bonded with the matrix interface in the pore wall.TiC generated by in-situ reaction as the second phase strengthened the compressive strength of porous titanium,up to 389.94MPa,which was 3.78 times that of the unstrengthened scaffold.Meanwhile,its elastic modulus was only 8.2GPa,which matched with the modulus of human bone.Moreover,the in-situ reinforced porous titanium scaffold had good biocompatibility.After the introduction of carbon fibers,some of the carbon fibers enter the pore wall and react in situ to form TiC,and some of the carbon fibers form interlamellar bridges.The interlamellar bridges of the carbon fibers through the diffusion of titanium atoms and carbon atoms on the surface of the fibers generate TiC/Ti fibers by in-situ reaction.The two ends of the carbon fibers are tightly bound with the matrix,which can effectively reduce the interlamellar splitting.With the increase of carbon fiber content,the fiber bridging density increases,and the compressive strength of the porous titanium scaffold is up to 161.66MPa,which is increased by 58.24MPa compared with the pure titanium scaffold,while the elastic modulus is only 5.99GPa.At the same time,the scaffold has low biotoxicity and good biocompatibility,so it has a good application prospect as bone implant material.