Microstructure And Characterization Of Biodegradable Zn-Based Composites Fabricated Via AgNWs-Assisted Hetero-Agglomeration

Nowadays,biofunctional ceramic reinforced biodegradable Zinc（Zn）-based composites as biodegradable implant materials have been recognized as a promising approach to overcome the insufficient mechanical performance of Zn matrix,adjust degradation rates of Zn-based biomaterials,improve its biocompatibility and endow the Zn-based materials with biofunctionality.However,due to the large difference in physicochemical properties and the poor wettability between Zn matrix and reinforcement,it is easy for reinforcement particles to agglomerate during the preparation of composites and then lead to poor dispersion properties of Zn-based composites.In order to deal with these problems,in this present study,a novel and effective protocol was employed to obtain Zn matrix composites reinforced by uniformly dispersed copper oxide（CuO）or beta-tricalcium phosphate（β-TCP）via silver nanomwires（AgNWs）-assisted hetero-agglomeration and subsequent spark plasma sintering（SPS）and hot extrusion（HE）processes.The hetero-agglomeration method based on the principle of electrostatic self-assembly can allow reinforcement to disperse homogeneously into reinforcement/metallic matrix mixed powder.In an appropriate polarity solvent,the negatively charged AgNWs could combine with both the positively charged Zn powder and reinforcement particles by electrostatic attraction and charge neutralization.Due to the nature of hetero-agglomeration,the AgNWs with large specific area could adhere to the large Zn powder and attract a certain amount of reinforcement particles to form reinforcement（CuO orβ-TCP）/AgNWs/Zn structure by charge neutralization,thereby forming a uniform dispersion of reinforcement particles within Zn matrix.Combined with subsequent SPS and HE processes,CuO or?-TCP reinforced Zn matrix composites with different biofunctionalities could be prepared.Due to the homogeneous dispersion of reinforcement ceramic particles,fine and uniform microstructure,and robust interfacial strength,the HEed CuO/Zn-0.8Ag andβ-TCP/Zn-2.0Ag composites manufactured by this method all exhibited great mechanical properties.Among them,the HEed 2CuO/Zn-0.8Ag composites possessed yield strength（YS）of 269.8±1.0MPa,ultimate tensile strength（UTS）of 271.3±4.0 MPa,and elongation at failure of15.8±0.1%.Meanwhile,this biocomposite showed a degradation rate of 128.0±19.2μm·y^-1,good cytocompatibility to MC3T3-E1 cells and superior antibacterial behavior.On the other hand,the HEed 1β-TCP/Zn-2.0Ag composite possessed YS of 235.8±1.2 MPa,UTS of 271.3±4.0 MPa,and elongation at failure of 22.8±1.5%.A uniform corrosion morphology and a degradation rate of 86.1±26.4μm·y^-1were displayed in simulated body fluid（SBF）solution.Moreover,this composites exhibited satisfying biocompatibility and antibacterial activity.Therefore,biodegradable 2CuO/Zn-0.8Ag and 1β-TCP/Zn-2.0Ag composites fabricated by AgNWs-assisted hetero-agglomeration,subsequent SPS-induced in situ alloying and HE processes manifested great application prospect in the field of biomedical bone implantation.