Synthesis And Characterization Of Spinel Ferrites Magnetic Nanomaterials

As important functional inorganic materials,magnetic nanoparticles have been applied in many fields,such as,electronics,information,electrical and mechanical products,automobiles,metallurgy,aerospace,transportation systems,biology, medicines,etc.Ferrite material is one of the most important kinds magnetic materias, which take a very large percentage in magnetic materials market.Ferrite materials and devices have played an important role for construction of modern technologies,global economy and even the new life style of the people in the world.In recent years,the magnetic ferrite nanoparticles have attracted more and more people's attention.Some techniques for synthesis of ultra-fine ferrite magnetic particles with unique properties has been developed.Currently,synthesis of different types of nano-ferrite materials with more efficient synthesis routes has become a hot topic in materials research.Spinel ferrite nanoparticles have been studied extensively because of their excellent physical,chemical and mechanical properties.Up to now,some synthesis methods for preparation of spinel nanoparticles,include the traditional hydrothermal, sol-gel,chemical co-precipitation,wet air oxidation,micro-emulsion,and hot-spray have been developed.However,most of above methods are related to high pressure, expensive chemicals,surfaetants,or complex equipment.Recently,a new methodology,called as composite-hydroxide-mediate method,for synthesis of spinel nanoparticles was proposed by our group.This method is besed on the reactioin of synthesis of spinel materials in a molten mixed-hydroxide solvent.In this thesis,ferrite nanoparticles,CoFe₂O₄,and NiFe₂O₄ with cubic spinel structure were synthesized successfully through this composite-hydroxide-mediate method with some common commercial chemicals at about 200℃.In this synthesis, molten mixed basic method(melting of NaOH and KOH)was used as solvent..X-ray diffraction(XRD),transmission electron microscopy(TEM)and infrared spectrometer(IR)were used to characterize the obtained samples.Vibration magnetometer was used to measure the hysteresis loop of the samples to characterize the magnetic properties of the samples.The results showed that the purity and morphology of the obtained samples is related to the synthesis conditions and the species of raw materials with different reaction activities.In the same process,salts raw materials are more active than the oxides,and has more benefit for getting ferrite nanoparticles with better quality.Cobalt ferrite and nickel ferrite with uniform particle sizes in the range of 10-50 nm can be obtained by using nitrates or acetates as raw materials.The optimal temperature and reaction time are 200-220℃and 24-48 hours, respectively.The synthesized nano-particles are small in sizes with uniform diameter, and have a good dispersion feature.Their magnetic properties are middle magnetic saturation magnetization and high coercivity.This method enriches and develops the preparation technology of ferrite materials and has an important theoretical significance and far-reaching practical significance.