Preparation And Properties Of Symmetrical Controlled Degradable Zn-Mg Functional Gradient Bio-materials

Based on excellent bio-compatibility and degradability,zinc alloy and magnesium alloy are expected to be used as medical materials to prepare various bone tissue repair and implant materials.However,due to the rapid degradation rate of magnesium and its alloys in the physiological environment,and their will be seriously degraded before the damaged bone tissue is fully healed,leading to the failure of implantation.However,the metal zinc has an appropriate degradation rate,its strength is low and cannot meet the clinical needs.To solve the above problems,based on the relationship between the mechanical properties and degradation rate of ideal degradable bio-materials,the paper proposes to fabricate symmetrical and controllable degradation Zn-Mg Functionally Gradient Biomaterials?FGB?by using Spark Plasma Sintering?SPS?technology from the perspective of bionics.In order to match the mechanical properties and healing cycle of bone tissue.The single-layer Zn-xMg?x=10,30,60,90?and multi-layer controllable degradation Zn-Mg FGBs were successfully prepared by material composition optimization design.The microstructure,phases composition,interfacial behavior,mechanical properties and corrosion resistance of various materials were emphatically analyzed.In addition,their bio-compatibility were evaluated.The results are as following:1.In this experiment,there is a unique core-shell?CS?structure with Mg particles as the core and MgZn₂ as the shell in the Zn-xMg alloy prepared by the SPS method.In addition,with the increase of Mg content,the number of such CS structure also increased,and finally formed four kinds of Zn-Mg alloys.Then the macroscopic mechanical properties of Zn-xMg alloy were tested.It was found that the mechanical properties of Zn-x Mg alloy were improved with the increase of the CS structure in the alloy.For example,the strength?239MPa?and plasticity?8.03%?of Zn-60Mg alloy with continuous network CS structure reached the maximum.The strength and plasticity had good synergetic effect.2.The corrosion test of Zn-xMg alloy immersed in SBF solution shows that the corrosion rate of Zn-xMg alloy was from small to large within 7 days with the increase of Mg content:Zn-10Mg<Zn-30Mg<Zn-60Mg<Zn-90Mg.Moreover,the corrosion rate of Zn-10Mg alloy within 30 days is only 0.26mm/a.From the perspective of corrosion rate,Zn-10Mg alloy is an excellent potential biodegradable implantation material.In addition,the cell compatibility of the alloy was evaluated,and it was found that Zn-x Mg alloy had good cell compatibility,and Zn-90Mg alloy had the best cytotoxicity test performance.3.After gradient lamination of each single Zn-xMg alloy,it is found that the introduction of gradient structure could improve mechanical properties of the sample.Compared with the single Zn-xMg alloy,the maximum compressive and bending strength was increased by 126%and 41%,respectively.In addition,as the number of gradient layers increases,the strength of FGBs also increases.The maximum compressive and bending strength of the 7-layered FGB were261MPa and 114MPa,respectively.Moreover,the immersion corrosion of FGBs'section in SBF showed that Zn-Mg FGBs had a gradient degradation function.Therefore,the Zn-Mg FGB studied in this study is expected to be a degradable metal implant material with controllable degradation function and excellent mechanical properties.