The Study On Preparation And Property Of Nano-sized Magnetite Particles

As new materials, nano-sized magnetite particles are a group of technologically important magnetic materials of current interest. They are mainly used as magnetic cores in the electronics, communication and information industries. In addition, they are also extensively used as catalysts. Nano-sized magnetite particles are now being studied intensively as their physical and chemical properties are quite different from those of the bulk materials in optics, calorifics, electricity and magnetism, such as quantum size effect, undersized effect, surface and interface effect and macroscopical quantum tunnel effect, etc. With the development of electronic components towards small size, light weight, high performance and the exploitation of application field, it brings the demand of increasinging improvement for electronic and magnetic materials used for. The synthesis of nanosized magnetite particles has been one of the most interesting research field.Many chemical methods have been developed to prepare nanosized magneitite powders, such as co-precipitation, hydrothermal processes, micro-emulsion mediated process, sol-gel method, and so on. In this thesis, a new method by oxidation -coprecipitation phase transformation has been successfully developed for the fist time. Nanosized magnetite powders was prepared at low temperature. In this novel method, control in size and composition was obtained.Ferrous sulfate was used as initial material Fe(OH)₂ precipitation was formed by adding NaOH to the ferrous ion solution. The precipitation was transformed into feroxyhyte (δ-FeOOH) by oxidation successively at room temperature. And then, metal ions in some ratio were added to the feroxyhyte solution. The pH of the mixture was adjusted by adding NaOH and thus the co-precipitation was obtained. The co-precipitation was refluxed sometime under constant stiring, and filtered and washed several times with de-ionized water to get rid of sulfuric and hydroxide ions. Finally, the mixture was dried at 60℃ in an oven overnight and the nanosized magnetite powders...