Study Of Microstructure And Properties Of HA And β-TCP Particles Reinforced Zinc Matrix Composites

Zinc alloys have attracted great attention in respect of biodegradable bone implant applications due to their excellent mechanical properties and biodegradable characteristics.Zinc, being an organism indispensable trace element, has a great effect on the normal development of bone, but the biocompatibility of zinc alloys need to be improved.Hydroxyapatite (HA) and tricalcium phosphate (β-TCP) bioceramics have excellent biocompatibility and can be used to improve the degradation rate of the zinc alloys. Therefore,composites of zinc alloys reinfored with HA and β-TCP have been fabricated in order to meet the requirement of the biomedical materials.Firstly, the single-phase HA and β-TCP powder have been prepared using the liquid precipitation method. Then the HA or β-TCP powder have been mechanical mixed with zinc powder according to mass ratio. HA/Zn,β-TCP/Zn,(HA+β-TCP)/Zn and β-TCP/Zn-3Sn composites have been prepared by hot pressing sintering method. The microstructure,mechanical property and corrosion behaviors of the composites have been evaluated by means of scanning electron microscopy (SEM),energy dispersive spectroscopy (EDS), X-ray diffraction (XRD), mechanical testing, electrochemical and immersion test.The results showed that the reinforcement phases of the composite materials had agglomerated at the crystal grain boundaries, but with the increasing of content, reinforcement phase gradually distributed into the crystal grain and the extent of agglomeration decreased.The compression strength of the composites reduced with the increasing of the content of HA or P-TCP and can satisfy the requirement of implant materials.The electrochemical test results showed that the corrosion current of several composites were higher than that of the pure Zn in Hank’s simulated body fluid,which indicated that the corrosion tendency of composites were higher than that of the pure Zn. That is to say, the corrosion tendency of the Zn added with the reinforcement phases was increased. The corrosion rate of the composites has been improved, which can solute the problem of slow degradation of the zinc alloys. The results of four composites immersed in Hank’s solution showed that the main corrosion products of the surface of the matrix and composites were Zn(OH)2, HA or β-TCP. The pH values of the Hank’s solution incubating the composites were fluctuated between 6.6-7.6, which indicated that the composites had good chemical stability in Hank’s solution. In the immersion process, the Zn2+ concentrations of the composites increased constantly for the first 15 days and then reduced to the level of about 7 days after 20 days of immersion. The maximum amount of Zn2+ concentrationin was 9.91mg/L, which is no toxic effect on the human body.Hemolysis test showed that the hemolysis ratio of metal Zn and composites were lower than 5% which indicated that they have good compatibility with the blood.