| Hydroxyapatite (HA) is a most representative bioactive material,which is widely used as bone-repairing material on clinic.The magnetic field can stimulate primitive cells to differentiate into new bone cells,thus accelerates the healing process of bones.Combining the two will not only solve the issue of biocompatibility but also can induce or stimulate the formation of new bone.In this study, Hydroxyapatite (HA) and magnetic material Fe3O4 were synthesized beforehand,and then some pore forming agent and high temperature adhesive were added to prepare magnetic porous HA bioceramic by sintering method.The phase composition and microstructure of the material were characterized by TG-DTA, XRD, SEM and FE-SEM,and the relationship of composition,process structure with properties was researched.HA nano-powders were prepared by sol-gel process and using Ca(NO3)2·4H2O and P2O5 as starting materials.The optimum process was reacting at 30℃with pH of 8,then heated at 600℃.XRD analysis showed that the the size of HA prepared in this study was 40-50nm with a high crystallinity of 95.03%.This HA began to decompose at 650℃while CaO emerged.Microstructure analysis by FE-SEM indicated that the HA particles were rod and columnar, some of the powder agglomerating.FT-IR analysis showed that there were trace CO32- in the crystal lattice of nano-HA,which was favorable for improving its bionic performance.Magnetic material Fe3O4 was prepared by hydrothermal method.The best sample was obtained by reacting at 140℃for 24h with 2mol/L NaOH in the reactant.SEM and XRD analysis showed that the Fe3O4 synthesized in this study was octahedral with an approximate particle size of 1.5～2.5μm and the crystallinity was 87.70%. The saturated magnetization value of the Fe3O4 in this study was 86.93emu/g, the coercive force was 85Oe, safe to hunman body, which was suitable for bone defect healing.Nano-HA and magnetic Fe3O4 were used as main material,some bioglass and amylum were added as high temperature adhesive and pore forming agent to prepare magnetic porous hydroxyapatite nano-bioceramics of four different formula. The testing results of microstructure and properties showed that the optimum bioceramic sample was formula NO.2 fired at 1020℃, in which the content of HA, Fe3O4,amylum and bioglass was 57.69%,7.69%,11.54% and 23.08% respectively.The porosity of the sample was 45.46%, bending strength was 12.33 MPa, the saturated magnetization value was 61.92emu/g and the the coercive force was 103Oe. XRD analysis indicated that the main crystal phases of the bioceramic were Ca10(PO4)6(OH)2(hydroxyapatite),Fe3O4(ferroferrite) and y-Fe2O3(y-hematite). SEM analysis showed pores of sample were three-dimensional bonded and well distributed. The pore sizes were different, and the diameters of the macropores were 10-30μm while the micropores were only 1～5μm, which was beneficial to the degradability of the material. Fe3O4 well distributed in the HA matrix, which was favorable for the magnetic properties to functionate. Columnar Ca10(PO4)6(OH)2 crystal grains composed the framework while other crystal grains were distributing around them.All the crystal grains were connected by glass phase,in order to make sure the bioceramic has a high bending strength.
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