The Preparation And Magnetic Properties Of Iron Nanocomposites With Core-shell Structure

With the rapid development of the technology of the nano-structured materials, the simple preparation of nano-structured materials has no longer been the focus. Recently, the synthesis of nanocomposites with special properties and nanostructures has attracted increasing attention for the demand of the special applications. Considerable experimental investigation has been focused on the core/shell nanopareticles because of their controllable advantages. Recently, metallic magnetic nanoparticles have been applied in many fields due to their high saturation magnetization, high permeability, high Curie temperature and low coercivity. However, they may undergo growth in size and agglomeration during heat treatment. Moreover, the instability toward oxidation also limits their applications. Furthermore, because of the metallic property and direct metal contact between iron particles, the eddy current often can be induced by the applied alternating field. The nanocomposites with core-shell structure may be a good way to solve these problems.1. The preparation and magnetic properties of Fe/TiO2 nanocomposites(1)The Fe/TiO2 nanocomposites have been prepared by a simple sol-gel combined hydrogen reduction method. The thickness of the shell can be controlled easily because the reaction was in nonaqueous solvent and no washing process was used.(2)The TiO2 shell not only acts as an insulating layer, but also prevents the size increase of Fe core effectively; the nanocomposites have high saturation magnetization and low coercivity, and show good soft magnetic property. 2. The preparation and magnetic properties of Fe/FeTiO3 nanocomposites(1)The Fe/FeTiO3 nanocomposites have been prepared by a simple sol-gel combined hydrogen reduction method. The Fe/TiO2 and Fe/FeTiO3 nanocomposites can be obtained at different reduced temperature, respectively.(2)The FeTiO3 shell not only acts as an insulating layer, but also prevents the size of Fe core to increase effectively. Moreover, the nanocomposites have high saturation magnetization and low coercivity, show good soft magnetic property.(3)The real permeability of the Fe/FeTiO3 nanocomposites is almost independent of frequency up to 50 MHz, and the imaginary permeability keeps small. With the increasing of the pressure, the real permeability of the Fe/FeTiO3 increases.3. The high temperature magnetic properties of Fe/FeTiO3 nanocomposites(1)The complex permeability of the Fe/FeTiO3 nanocomposites is almost independent of temperature up to 210℃when they are kept in Ar atmosphere.(2)When the Fe/FeTiO3 nanocomposites are in contact with air, the Fe core can be oxidized to iron oxide above 250℃, as a result, the real permeability of the Fe/FeTiO3 nanocomposites may decrease.