Size And Morphology Control Of Fe₃ O₄ Preparation And Charaterization

Magnetic nanoparticles Fe₃O₄ had unique physical and chemical characteristics, which was found to possess broad applications in many aspects,such as magnetic recording materials , Magnetic fluid, absorbing material, catalysis,pigment and biomedicine.The properties of Fe₃O₄ was greatly effected by their size and morphology,so the control-size and control-morphology of Fe₃O₄ had very important value of research. In recent years,there was many researches for size and morphology of Fe₃O₄, but it was found to have some problems such as the high cost ,process complex, serious reunion of the products , poor uniformity of particle and few works had been reported about the control mechanism of morphology of Fe₃O₄ . Therefore this paper was discussed to prepared different morphology and size of Fe₃O₄ using air oxidation process and simple hydro-thermal method, then this study provided theoretical basis for application of Fe₃O₄ .The main research work is summarized as follow:(1) Preparation and properties of sized-controled Fe₃O₄It was studied that the hydroxyl compound (ethanol, glycol, PEG- 600)and carboxyl compounds (sodium oxalate, Sodium citrate, EDTA) had effect on the size of Fe₃O₄ adopting air oxidation process.Results found that with the increasing hydroxyl (carboxylic) number, the size of Fe₃O₄ gradually become small.At using ethanol as additives , size of Fe₃O₄ was reduced with increasing the volume of ethanol in the range of V_CH3CH2OH /V_H2O=0-1/2.At using different carboxyl compounds as additives, the number of carboxyl and the concentration of EDTA improved the dispersion of Fe₃O₄. The system using ethanol and EDTA as additives showed better dispersion and size of Fe₃O₄ than single system of ethanol. The 11.1 nm of nano Fe₃O₄ that has good dispersion and uniformity was prepared by using ethanol and EDTA as additives.Compared with propertites of different size of Fe₃O₄ , the results shows that with decreasing the size of Fe₃O₄, specific surface area of Fe₃O₄ and coercivity increased and Saturation magnetic strength decreased.The sample that the particle size is the range of 48.66—25.12nm exhibited a ferromagnetic behavior. The 11.1 nm of nano Fe₃O₄ that was prepared by using ethanol and EDTA as additives had super paramagnetic behavior and good dispersion.(2)Preparation and properties of morphology-controled Fe₃O₄Different kinds of morphology of Fe₃O₄ such as stick, spherical ,flake, octagonal, carambola, cube was prepared by the hydrothermal synthesis method using chloride-ferric, ferrous sulfate, potassium ferricyanide as iron source. The structure and morphology of Fe₃O₄ was investigated by changes of the auxiliary additives (polyethylene glycol and glycol),the sodium hydroxide, the reaction temperature and the reaction time. The results of the study indicate that:With chloride-ferric as raw materials, along with the increase of polyethylene glycol, the morphology of spherical occurs from the change to stick; Adopt ferrous sulfate as an iron source, quantitative changes through regulation sodium hydroxide, spherical became irregular flake, by adding glycol got flake morphology Fe₃O₄, through reaction temperature increase and the extension of time, sheet will continue to grow four oxidation, further grew into octahedron structure; Adopt potassium ferricyanide for iron source, preparation of Fe₃O₄ by adjusting the amount of sodium, found that the more, the benefit of sodium hydroxide octagonal Fe₃O₄ generation, and at the same time, the more, the greater the particle size of sodium hydroxide with the increase of ethylene glycol morphology, grow from carambola shape for octahedron, cube; Through improving the reaction temperature and reaction time, available to extend the cube shape shape rules SanTie four oxidation.Further to analysis magnetic of stick, flake, octagonal, cube shape of Fe₃O₄ at room temperature are ferromagnetic, stick Fe₃O₄ saturation magnetization for 59.48 emu/g, flake Fe₃O₄. saturation magnetization for 87.92 emu/g, Fe₃O₄. cube shape saturation magnetization for 102.23 emu/g, there are exist obvious differences in different shape of Fe₃O₄, maybe magnetic was closely relat ed to morphology of anisotropic.