化学共沉淀法制备ni-zn软磁铁氧体及其性能研究word格式论文.docx

优秀毕业论文 精品参考文献资料 ABSTRACT Ni-Zn soft magnetic ferrites are widely used in transformer cores, high- frequency inductors and read-write heads because of their low coercivity and high electrical resistivity. The method of mass-production Ni-Zn ferrites in industry is traditional ceramic calcination method, namely heating the metal oxides at a relative high temperature. But it is difficult to get fine and homogeneous particles which are important to good properties by using this method. In addition, the process is complex and it is hard to control the characteristics of the particle. In this work, the chemical coprecipitation method was used to synthesize three kinds of Ni-Zn ferrites with different compositions. Morphology, structure, and composition of the Ni-Zn ferrite powder were characterized by Scanning Electron Microscopy (SEM), Energy Dispersive X-ray (EDX) and X-ray Diffractometer (XRD); Thermogravimetry and Differential Thermal Analyses (TG-DTA) were used to reveal the phase transition of the different compositions. The effects of additional surfactant in the mixed solution on the microstructure of the ferrites were studied. Finally, the DC (Direct Current) magnetic properties of ferrites were measured by Vibrating Sample Magnetometer (VSM). It was found that ultrafine NiFe2O4, ZnFe2O4 and Ni0.5Zn0.5Fe2O4 nanopowders could be synthesized via coprecipitation method followed by a heating treatment. The optimized heating temperatures were ~500oC, 400oC and 490oC respectively. Higher temperature led to the ferrite decomposition with Fe2O3 as the main product. The thermal stability of NiFe2O4 was better than that of ZnFe2O4. The raw precipitate with the addition of surfactant had more homogeneous size distribution than that of precipitate without surfactant, which was due to the function of surfactant as a dispersant. The surfactant capping inhibited the grain growth of the particles under low heating temperatures. The hydroxide precursor was paramagnetic at room