Biomedical Titanium Matrix Composites

Titanium and its alloys are widely used as load-bearing implants for bone tissue engineering due to their good mechanical properties, good biocompatibility and excellent corrosion resistance. However, titanium and its alloys in their solid forms are much stiffer than human bone and do not provide new bone tissue ingrowth abilities and vascularisation, leading to implant loosening and eventual failure. It is estimated that20-25%of patients having an orthopaedic implant will eventually require a secondary revision surgery. The solution is to match both the architecture and the mechanical properties of implants to those of nature bone. However, the strength of porous pure titanium deceases dramatically with the introduction of porosity and is lower than that of natural bone, when the porosity is increased sufficiently to match the stiffness of natural bone and enable new bone tissue ingrowth and vascularisation. Therefore, it is important to enhance the strength of titanium and its alloys to ensure appropriate stiffness, as well as adequate strength when it is used in a porous structure.Porous pure titanium (Ti) scaffold with high porosity is promising for use as implant materials. Particulate-reinforced metal composites have attracted extensive attention as a result of their relatively low costs and characteristic isotropic properties. The mechanical properties of metal and its foams can be improved by matrix reinforcement, e.g. adding fine ceramic particles or alloying elements in the base powder of the powder metallurgical route. The size, shape and volume fraction of the reinforcement affect the elastic modulus, strength, fracture toughness and compressive creep propertiesIn this study, biocompatible SiO2/ZrO2/Nb2O5particles are selected for fabricating the particulate-reinforced Ti composites to ensure its biocompatibility and mechanical property. The particulate-reinforced Ti composites are fabricated using powder metallurgy (P/M). The effects of composition and sintering temperature on the microstructure and properties of the Titanium-Based Composites were investigated by X-ray diffraction, optical microscope, scanning electron microscopy and mechanical properties tests. The relative density result showed that the relative density increased with increasing sintering temperature. The results indicate that the strengths of the composites are significantly higher than that of pure titanium. At the same time these composites preserved good elasticity. The sample added2%SiO2and sintered at1100℃exhibited a compressive strength of1566MPa and a ultimate strain of15.96%. The sample added4%ZrO2and sintered at1100℃exhibited a compressive strength of1280MPa and a ultimate strain of24.13%. The sample added2%Nb2O5and sintered at1100℃exhibited a compressive strength of1494MPa and a ultimate strain of16.44%. In vitro results reveal that the composite possesses excellent biocompatibility and cell adhesion. Osteoblast-like cells grew and spread better on the surfaces of the Ti/SiO2composites than pure Ti.This study demonstrates that the SiO2/ZrO2/Nb2O5particulate-reinforced Ti composite is a promising material for great potential use as an orthopedic implant material.