The Preparation Of Iron-Based Composite Particles With Magnetic Property

Magnetic materials have a long history and widely used as functional materials. With the continuous development of science and technology as well as the improvement of the people's demand, the research of magnetic materials are constantly updated. New types of magnetic polymer composites with its superior performance are applied in various fields.We prepared the Fe₃O₄ particles with coprecipitation method firstly, then we obtained the magnetic composite particle PMMA/Fe₃O₄ with different content of Fe₃O₄ through precipitation polymerization technique. In this reaction, we used methyl methacrylate as the monomer, azodiisobutyronitrile as initiator and ethanol as reaction medium. We have characterized them by means of IR, P-XRD, AAS, SEM and VSM. Successfully it turns out that we obtained the Fe₃O₄ particles with spinel structure, moreover, they also have good crystalline form and high purity. Its saturation magnetization intensity is 71.81 emu/g. When the Fe₃O₄ particles was encapsulated by the PMMA, its crystalline form still for spinel structure, there is no change, but its saturation magnetization intensity is decreased. When the content of Fe₃O₄ in the sample is more than 38.73 %, most of them have the shape for coral reefs shape, it is the same to pure Fe₃O₄. The shape and size of the composite particle is uniform distributed. There are some gaps exist between the particles. The top of the particles' surface is irregular round sphere. Its size is less than 0.5μm. However, when the content of Fe₃O₄ in the sample is 38.73 %, the size is smallest and the dispersibility is the best. This result prove that when the polymer content increase to a certain extent, the particles size and shape as well as dispersibility will be changed. In addition, we used a mixed-valence triiron complexes and as initial material and prepared two types of magnetic composite particles with the different molar ratio to the initial material through high-temperature polycondensation reaction. They were characterized by several techniques such as SEM, AAS, P-XRD, VSM and IR. The result shows that the magnetic composite particles of Fe₃O₄ have the crystalline form spinel structure, which was obtained at the conditions of to mixed-valence triiron complexes and p-hydroxybenzoic acid at molar ratios of 1:12, 1:24, but their crystalline form are worse, magnetic are weaker. Most of them have the shape for coral reefs shape, the size is less than 0.5μm; Further, when the molar ratio is 1:48, the prepared sample has a different crystalline form compared to the others. The size is smallest and dispersibility is the best. In the magnetic aspect, it is similar to the sample obtained by molecular rational of 1:24, they are separately 3.35 emu/g and 3.06 emu/g. The size is smallest and dispersibility is the best.