Fabrication And Properties Of Hydroxyapatite/Ti-13Nb-13Zr Composites For Biomedical Application

Ti-13Nb-13Zr biomedical alloys are promising as implantable biomaterials due to excellent mechanical properties,anticorrosive properties,fatigue strength and biocompatibility.However for the bioinert of Ti alloys,they cannot adapt to natural bone tissue and physiological environment.And conjunction between implanted Ti-alloys and natural bone tissue is mechanical interlocking which cannot form beneficial osseointegration.For a long service,Ti-alloys would become loose or even cause failure of implantation.In this work,given this,Ti-13Nb-13Zr alloy matrix was biofunctionalized with spark plasma sintering（SPS）method.The（Ti-13Nb-13Zr）-x HA biocomposites were expected to combine the mechanical properties and biocompatibility of Ti-13Nb-13Zr alloy and bioactive hydroxyapatite（HA）ceramic.The effect of different preparation technologies and HA ceramic contents on microstructure evolution,mechanical properties,biological friction property,corrosion resistance,bioactivity and biocompatibility have been researched systematically.Ti-13Nb-13Zr matrix enhancing with HA bioactive ceramic were prepared by means of mechanical ball milling and spark plasma sintering.The phases of as-sintered（Ti-13Nb-13Zr）-xHA composites were mainlyβ-Ti,α-Ti,HA and reaction products of Ca₃（PO₄）₂,Ti₅P₃,CaZr O₃ and CaO.With the increase of sintering temperature,the trend fromα-phase toβ-phase of composites was improved while the contents of reaction products were increased.Meanwhile with the increasing HA contents,degrees of reactions between HA ceramic and metal powders were enhanced,namely,the formation of high strength and low elastic modulus ofβ-Ti phase was inhibited.Changes in the relationship between relative density and microhardness and HA contents showed inverse proportion and direct proportion,respectively.When the HA content was 5-10 wt.%,the compressive strength,yield strength and elastic modulus of the composites reached the optimum value respectively.The corrosion resistance of composites in simulated body fluids decreased with the increase of HA content,and the corrosion current density and corrosion potential of（Ti-13Nb-13Zr）-10HA composites were-448.9 mV（vs.SCE）and 4.601μA·cm^-2,respectively,which demonstrated good corrosion resistance.The friction properties of composites in simulated body fluid（SBF）show that the wear mechanism is adhesion wear and abrasive wear.The elastic modulus of composites declined after rising first.The wear rate of（Ti-13Nb-13Zr）-10HA composite was 6.5×10^-4 mm³N^-1m^-1,which showed the optimal value among the composites in SBF solution.The bioactivity and biocompatibility of（Ti-13Nb-13Zr）-xHA biocomposites were studied in vitro.The immersion tests in SBF,the formation ability of bone-like apatite layer on（Ti-13Nb-13Zr）-xHA composites were enhanced with the increasing HA contents while the Ti-13Nb-13Zr alloys presenting the deposition of NaCl crystal.The hemolysis rate for as-milled mixtures and as-sintered composites of（Ti-13Nb-13Zr）-xHA were both lower 5%.And the hemolytic rate of as-sintered composites was significantly lower than that of as-milled mixtures.The composites conformed to the biomedical material standard,which showed that the composites had good blood compatibility.Experimental results of cell adhesion,cell proliferation,ALP activity and cell apoptosis showed that（Ti-13Nb-13Zr）-xHA composites had good biocompatibility in vitro.The addition of HA ceramic was beneficial to the adhesion,proliferation and differentiation of BMSCs,and BMSCs on the surface of composites showed active grow and mineralization which mean their good bioactivity.