Magnetic Iron Oxide Nanostructure Synthesis And Characterization

With the development and improvement of nano-techniqe, new fields of created for reaearch and application of magnetic ferrite, especialiy on biomedicine. Magnetic nanoparticles have been widely applied, such as, separating magnetic immune cells, labeling biologic molecule by magnetism, controlling medicine release and so on. The magnetic inductive heating, in use of tumour therapy by its hyperthermia based on core loss of the magnetic ferrite material under the high frequency magnetic field, has attractive more and more people's intensive interests.In this thesis, for its good biocompatibility and low biotoxicity.selecting Fe3O4 as research object, we investigated static magnetic properties and permeability and core loss in high frequency alternating magnetic field of Fe-Zn firrite which have different zinc contents. And we explored the size effect and surface modificatin influnce of the ferrite particles. At last we trying to control the growth and orientation of one-dimension Fe3O4 nanoparticle chains.under applied inductive magnetic field. My detail work as follows:Firstly, we have prepared a series of Fe-Zn ferrite with different zinc contents by chemical coprecipitation method. TEM characterization indicated that the samples consists of homogeneous, discrete, spherical particles with means size about 15nm. XRD proved that the samples were all single phase of spinel. By we measrement of magnetic properties found that the curie temperature Tc decrease with the zinc contents increasing and saturated magnetic moment reaches maximum value when zinc contents increase to 0.3, then decrease with the zinc contents increasing. This is because the nonemagnetic impurties cut down the exchange interaction. For smaller than size of single domain, particles show some quantum effections, such as its saturate magnetic moment smaller than block material.Secondly we prepared nanoparticles with different size and shape using aging ferrous hydroxide gel, method by varing different mol concentration of KOH and FeSO4. We measured the relation between the coercive force and the particle size, thus obtained the critical size of single domain and super paramagnetic particles. Then we made the Fe3O4@SiO2core-shell nanostructures are using the conventional St?ber polycondensation with dilute silicate solution treatment directly in ethanol. By comparing with the coercivity of particles between having and having not nonmagnetic core-shell, we found that their dependence relation between coercivity and particle diameter have a same trends, But the value of coercivity increasing for Fe3O4@SiO2core-shell structure, This can be explained by weaking the interaction between particles.We found the difference in aggregate forms is due to the different magnetic dipole interactions according to the point dipoles model.Finally, One-dimensional magnetite chains of spheres with different radii and lengths were prepared by aging ferrous hydroxide gel with KNO3 under different external magnetic fields which induced the ultra-fine magnetite particles to combine into chain structure. The magnetite particle size and the chain length could be adjusted by varying the field intensity. The chains could be deposited on silicon substrates to form aligned structure in magnetic field. The hysteresis loops were measured in different directions The result show that the ordered 1D pattern behaves a uniaxial anisotropy originating from the effects of shape anisotropy and the multi-domain of the each Fe3O4 particle. Last, we fitting the chains covercive force by bucking model.