Preparation And Propertity Of Biodegradable Mg Foam Material

With the development of biomaterials,magnesium alloy has been paid more attention by medical workers because of their good biocompatibility,elastic modulus close to bone and gradual degradation in vivo.However,magnesium alloy implanted in the human body is still not conducive to blood circulation and circulation problems,and the degradation rate too fast.Hydroxyapatite(HA)has become a hot research topic in the field of biological materials with its excellent bioactivity and bone conductivity as a kind of anticorrosive biological material.In this paper,biodegradable biomaterials were prepared by melt direct foaming method,porous structure of foam material was used to provide three-dimensional space for cell proliferation and regeneration,and HA particles were added into the foam,combined the advantages of HA to develop a new porous material.Mg-3%Ca alloy was prepared by adding pure magnesium into Mg-20%Ca alloy,which as matrix material,HA particles as thickening agent,and MgCO3 as blowing agent.The effects of factors such as temperature,time,MgCO3 and HA on the prepared materials were studied.The phase,microstructure,mechanical properties and corrosion behaviors were analyzed by SEM,XRD and other test measures.The main conclusions are as follows:(1)Preparation of biodegradable magnesium foamed material parameters are presented below:the stirring temperature of MgCO3 610?,the addition amount of MgCO3 2wt.%,particle size 120?,m;foaming temperature 640? and foaming time 2min;the addition amount of HA 4wt.%and 20?m.The specimen density obtained by this procedure is between 0.525?1.259g/cm3,porosity between 27.62%?69.83%.(2)The particle size of MgCO3 has a great influence on the pore size of foam material.With the decrease of the particle size of MgCO3,the pore size of the prepared sample is smaller,the average pore diameter is between 0.32?.22mm,and the average pore wall thickness is between 32?140?m.XRD analysis showed that Mg,Mg2Ca and HA existed in the material.The microstructures of the foam were analyzed by SEM.The results show that there are holes and missing cell walls in the cells.The smaller the density of the materials,the more holes in the pores.HA particles distribute at the edges of the foam material.(3)Compressive experiments were carried out on different foam materials.The results show:The yield strength increases with the increase of the content of HA in the foam,and the maximum is up to 15.67 MPa.With the decrease of HA particle size,the yield strength increases with the foam density increasing,65.36 MPa.(4)The simulated fluid corrosion experiments were carried out on different foam materials.The hydrogen evolution and PH tests were carried out.The results of hydrogen evolution show that the increase of HA content can reduce the amount of hydrogen evolution.The particle size of HA has no obvious effect on the amount of hydrogen evolution.The higher the density of the material is,the lower the amount of hydrogen evolution is.XRD analysis of the white substance after the etching on the surface of the sample showed that this material was mainly Mg(OH)2.The residue in SBF is a fragment of HA that is broken off during the corrosion process into the solution.Electrochemical experiments showed that the corrosion resistance of the samples with HA content of 8wt.%is the best.