Study On The Microstrure And Properties Of Bio- Mg-Zn/HAp Composite Fabricated By Spark Plasma Sintering

Biodegradable magnesium based materials are expected to be a kind of temporary biodegradable implant material in bone tissue engineering, for magnesium alloys possessing good biocompatibility, biomechanical matching and can being degraded in vivo. However, the high degradation rate in vivo impede its widely application as an biodegradable medical material. Thus, how to regulate vivo corrosion rate of magnesium matrix composites and ensure enough mechanical strength are the key issues to promote it as the bone tissue repairing materials in clinical application, which is also hot topic in study of bio-magnesium materials.This study is focusing on regulating and controling the corrosion and mechanical propertis by adding Zn and nano HAp particles. Using pure magnesium as the matrix, the bio-Mg-Zn/HAp composite with different Zn and HAp contents were fabricated through high energy ball mixing and SPS sinter. The mechanical properties and corrosion resistance of bio-Mg-Zn/HAp composite were adjusted by changing the Zn and HAp content and the transformation of the microstructure, phase composition, interfacial behaviors, mechanical properties, corrosion resistance and vitro cytotoxic were investigated. The main results are summarized as follows:By adding the Zn element(0wt%, 2wt%, 4wt%, 6wt%, 8wt%) into Mg, the bio-Mg-Zn alloy was prepared. The interface bonding between Mg particles were strengthened by adding the Zn element into pure Mg matrix, as well as the relative density, mechanical and corrosion properties, showed by microstructure analysis, mechanical and corrosion experiment results. The microhardness, compressive strength achieve the maximum 69.0 Hv0.1 and 379.5 MPa respectively, when the Zn content is 6wt%, meanwhile self corrosion current density reach the minimum value 106.4 mA/cm2. The optimal adding Zn content in bio-Mg-Zn alloy should be 4~6wt%.Based on the preparation of bio-Mg-Zn alloy, Mg-Zn/HAp composite was prepared with adding nano-HAp particles into the Mg-5.5wt%Zn matrix. Microstructural analysis and mechanical tests reveal that the microhardness, compression strength and bending resistance were enhanced, while relative density and interface bonding strength were decreased. The interface bonding between Mg particles was mechanical coupling and weakened with increasing of nano HAp mass fraction;Electrochemical tests and hydrogen evolution experiment were conducted to investigate corrosion behaviors and mechanism of Mg-Zn/HAp composite. The results reveal that, compared with that of Mg-5.5wt%Zn matrix, the corrosion potential of Mg-Zn/HAp composite were raised and self corrosion current density, hydrogen evolution rate in SBF were reduced by adding nano HAp. The corrosion process influenced by the particle bonding condition and occurred preferentially in the inner interface defects but its extension into internal Mg matrix were delayed for existence of nano HAp and MgZn phase layer on the interface.Vitro cytotoxicity tests measure by the MTT method showed that the Mg-Zn/HAp composites have no significant inhibition on growthing of L-929 cell and the cytotoxic evaluation result of the composites is qualified.