| Compared with zinc alloys with the poor mechanical properties of and magnesium alloys with the faster degradation rate,Fe based biomaterials are considered to be a new generation of biodegradable biomaterials with great application potential due to their better mechanical properties,biocompatibility,safety and non-toxicity.Porous Fe-Mn alloys have similar structure to bone,which can not only accelerate the degradation of the alloy,but also benefit the three-dimensional growth of bone tissue in the implants,so they have attracted much attention.In light of it,the porous degradable Fe-Mn alloys were prepared by organic sponge impregnation with Fe-Mn powders as raw materials,and the compsoition of Fe-Mn slurry,pretreatment of sponge and powder sintering process were optimized.The microstructure and mechanical properties of the porous Fe-Mn alloys were characterized,and their degradation behavior in the simulated body fluid?SBF?and biocompatibility were studied.The main contents and conclusions are as follows:1)The preparation and debinding processes of the sponge precursor were optimized.It is found that the prepared the alloy slurry containing 4 g·m L-1prealloyed Fe-Mn powders with the particle size less than 15?m and,and 6%binder polyvinyl alcohol?PVA?exhibits the appropriate viscosity with the evenly diepersed powders,and the skeleton of the sponge precursor impregnated with the slurry is complete.After the polyurethane sponge surface was treated with carboxymethyl cellulose?CMC?,the sponge skeleton surface was coarsened and the mechanical properties of the impregnated sponge precursor were improved.A thermal weight loss curve of the sponge precursor was measured,and its low debinding temperature was determined to be 350°C.2)The consolidation process of Fe-Mn porous alloys was optimized and the composition,microstructure and mechanical properties of sintered porous alloys were characterized.The results show that the sintering temperature has an important influence on the Mn content of Fe-Mn alloy,and the composition of the alloy sintered at 1100,1150 and 1200°C are Fe-44Mn,Fe-30Mn,Fe-12Mn,respectively;The porous alloys exhibit the interconnected porous structure with a porosity of about 85%and an average pore size of 375?500?m,which well replicates the porous structure of the sponge;The Fe-44Mn and Fe-30Mn porous alloys are mainly composed of?-austenite phases,while the Fe-12Mn alloys are composed of?-ferrite phases.The yield strength and elastic modulus of the prepared porous Fe-Mn alloys are 6?10 MPa and 0.12 and 0.37 GPa,respectively,which match the mechanical properties of human cancellous bone.3)The degradation properties of Fe-Mn porous alloys in simulated body fluids?SBF?were studied and their biocompatibility was evaluated.It is found that the degradation rate of porous Fe-Mn alloys decreases gradually with the extension of the immersing time in the SBF.After immersed in SBF for 14 days,the degradation rates for the Fe-44Mn,Fe-30Mn,Fe-12Mn alloys are 0.0855 mm/y,0.0596mm/y,and0.0352,mm/y,respectively,which is much higher than that of pure Fe under the same conditions?0.0185 mm/y?.The biocompatibilty of the Fe-Mn porous alloys was evaluated by the direct culture test of MC3T3-E1 osteoblasts on the alloys,and the results show that,after cultured for 7 days,the cell proliferation is obvious and the survival rate of the cells is more than 90%,implying that the porous Fe-Mn alloy showed good biocompatibility. |
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