Study On Preparation And Properties Of Carbon Nanotube Reinforced Zinc Matrix Composites

Compared with magnesium alloys,zinc alloys have good workability and suitable degradation performance,and no gas is generated during the degradation process.Moreover,zinc plays an important role in the growth and mineralization of bone tissue and is considered to be a new type of biodegradable implant material.The electrode potential of zinc is between magnesium and iron,so zinc has a more suitable degradation rate and is expected to become a substitute for magnesium and iron degradable implant materials.This study uses metal matrix composites to improve the mechanical properties of pure zinc.In this paper,pure zinc is used as the matrix,and multi-walled carbon nanotubes(MWCNTs)are used as the reinforcing material,combining with electroless copper coating,spark plasma sintering(SPS)and hot rolling technology to prepare CNTs/Zn composites.The effects of electroless copper coating,sintering methods and different CNTs contents on the microstructure,density,interface and mechanical properties of CNTs/Zn composites were studied.To evaluate the degradation performance and cytotoxicity of composites.(1)During the pretreatment,more hydrophilic groups-OH and-COOH are formed on the surface of CNTs,and the dispersibility of CNTs is improved.Moreover,a tightly bonded interface is formed between the CNTs and the nano-copper layer on the surface of the CNTs.In addition,the reduction of CNTs surface defects improves the integrity of CNTs.Oxygen-mediated formation of C-O-Zn bonds provides favorable conditions for the tight bonding between CNTs and zinc matrix.And the mechanical properties of the copper-coated CNTs/Zn composites are higher than those without copper coating.The copper-coated CNTs/Zn composite with CNTs content of 2 wt% compared with the uncoated copper,the ultimate tensile strength and microhardness were increased by 34 % and 4 %,respectively.The copper-coated CNTs/Zn composite with CNTs content of 3 wt% compared with the uncoated copper,the ultimate tensile strength and microhardness were increased by 25 % and 5 %,respectively.(2)The sintering process and density of vacuum hot press sintering and spark plasma sintering samples are compared.The density of spark plasma sintering samples is better than vacuum hot pressing sintering,but the hardness value of the composite material using two sintering methods not much differences.The density of the composites after hot rolling is further improved,with the increase of the content of CNTs,the grains of the CNTs/Zn composites are gradually refined,and CNTs are evenly dispersed in the zinc matrix.However,when CNTs are greater than 1.5 wt%,some of the CNTs are agglomerated significantly,and the agglomeration range expands with increasing content.As the content of CNTs increases,the mechanical properties of CNTs/Zn composites have improved to varying degrees compared to pure zinc.The 3 wt% copper-coated CNTs/Zn composite exhibits excellent mechanical properties and ultimate tensile strength and microhardness were 281 MPa and 89 HV,respectively,which were increased by 127 % and 37 % compared with pure zinc,respectively.And the strengthening mechanism of CNTs/Zn composites includes load transfer effect and fine-grain strengthening,and the load transfer effect plays a important role in the two strengthening mechanism.(3)The addition of CNTs improved the degradation rate of pure zinc,and 0.5 wt.% CNTs/Zn composite showed appropriate degradation rate.Cytotoxicity experiments showed that the biocompatibility of 0.5 wt.% CNTs/Zn composite was superior to other components.