Preparation And Properties Of Nano-Carbon Reinforced Titanium Matrix/Hydroxyapatite Nanocomposites

In recent years,the biotransplant composites prepared by combining titanium alloy with excellent mechanical properties and good bioactive hydroxyapatite?HA?have become research emphasis.However,the composites also have some problems,such as stress shielding effect,complex interface reactions and so on.Based on the research of Ti-29.2Ta-12.2Nb-4.3Zr?wt.%?-HA material system,nano-carbon materials?Graphene nanoflakes and Carbon nanotubes?are added to obtain a new biomaterials with excellent mechanical properties and biocompatibility.In the experiment,the surface modification of nano-carbon was firstly carried out by ultrasonic treatment and organic acid treatment.Then the nano-carbon reinforced titanium matrix/HA biocomposites were prepared by mechanical alloying and vacuum hot-pressingsintering/spark plasma sintering.Based on the analysis of microstructure and mechanical properties,effects of nano-carbon on the properties of the composites were investigated.Moreover,the strengthening mechanism,fracture mechanism and wear mechanism of composites were also analyzed.The results showed that graphene-reinforced titanium matrix/HA composites prepared by vacuum hot-pressing sintering occurred complex chemical reactions during high temperature sintering and resulted in new phases of nucleation,such as Ca₃?PO₄?₂,Ti_xP_y,Ti₃O.Moreover,the microhardness,shear strength and compressive strength of composites had the decreasing tend with graphene content of 0.5-1.5 wt.%.And this was caused by the agglomeration of graphene.Besides,strengthening mechanisms of composites were mainly the super-interface strengthening,dispersion strengthening,wrinkle structure and load transfer of GNFs.And solid solution strengthening,fine grain strengthening,and dispersion strengthening of other elements also can play a certain role.There are some new phases in nano-carbon reinforced titanium matrix/HA biocomposites successfully prepared by spark plasma sintering?SPS?,such as?-Ti,TiO₃,ZrO₂,etc.Moreover,a small amount of Ti₁₇P₁₀,CaTiO₃,Ca₃?PO₄?₂ were also detected.Compared with results of the composites prepared by hot-pressed sintering,the microhardness,compressive strength and shear strength of 0.5-GNFs composites prepared by SPS were increased by about 2.8,4.8,and 4.1 times,respectively.The better mechanical properties of 0.5-GNFs composite in nano-carbon reinforced titanium matrix/HA composites are mainly due to the lower degree of agglomeration of lamellar graphene nanoflakes?GNFs?.Moreover,the strengthening mechanisms of nano-carbon reinforced titanium matrix/HA composite were mainly the strengthening effects of nano-carbon,such as load transfer,super-large interface strengthening of GNFs,unique fold structure,bridging of CNTs,etc.The in vitro bioactivity test showed that the addition of nano-carbon was beneficial to promote the adhesion and proliferation of cells on the surface of titanium matrix/HA composite.Because nano-carbon can promote the formation of mineralized necks of composites after transplantation,stimulate biomineralization.The wear test results show that the main wear mechanisms of nano-carbon reinforced titanium matrix/HA composite in the process of dry friction sliding wear are abrasive wear.The adhesive wear and oxidative wear is also included.