Preparation And Magnetic Properties Of Fe@Ferrite Soft Magnetic Composite Magnetic Powder Core

With the development of miniaturization and high frequency of modern electronic devices,the magnetic cores are required to have high saturation magnetization,high magnetic permeability,and excellent high frequency performance.In this paper,according to the advantages of metals and soft ferrites,the core-shell structured Fe@soft ferrite composites in which the soft ferrite was employed as insulating coating agent and pure iron powder as the core were prepared by chemical co-precipitation method.The influence of composition and preparation process on the properties of composite magnetic powder cores was discussed.Firstly,MnZn ferrite was prepared by chemical co-precipitation method.Effects of element ratio,sintering temperature and oxygen content on the micro structure of the ferrite and properties of magnetic powder core were studied.With the increase of manganese content,the magnetic permeability and saturation magnetization of MnZn ferrites increased at the early stage and then decreased.And the saturation magnetization reached a maximum of 83.7 emu/g when the ratio of Mn to Zn was 0.6:0.4.At 1200 ?,MnZn ferrite had good magnetic properties.The pH of the reaction solution had important influence on the formation of ferrite precursors.The saturation magnetization of the sample reached a maximum of 88.1 emu/g when the pH value was 10.3.Oxygen content caused changes in the valence of metal ions and composition,which had a marked impact on the microstructure of MnZn ferrites.The magnetic properties of MnZn ferrite were the best when the oxygen content was 3%,and its saturation magnetization reached a maximum of 93.6emu/g.Fe@MnZn ferrite soft magnetic composites were prepared by chemical co-precipitation method combined with high temperature sintering.The ferrite was uniformly coated on the surface of iron particles to form a core-shell structure.The appropriate sintering temperature could remove the internal stress in the sample and also reduce defects and porosity better.Experiments finally showed that when the temperature was determined as 1200 °C?the magnetic properties of the composite was optimal.The thickness of the shell increased with the increase of the ferrite content,but the increase of the thickness would lead to the decrease of the saturation magnetic induction.A mass fraction of 6%was the optimum coating amount of the composite magnetic powder core.Excessive oxygen content can cause peeling and cracking of the coating on the surface of the sample,resulting in a decrease in its overall magnetic properties.At a partial content of 3%,the magnetic permeability and saturation magnetization of the composite material reached a maximum of 65.0 and 182.4 emu/g,respectively.NiZn ferrite and Fe@NiZn ferrite soft magnetic composites were prepared by chemical co-precipitation method combined with sintering method.With the increase of nickel content,the magnetic permeability and saturation magnetization of NiZn ferrite increased first and then decreased.The permeability and saturation of the sample reached a maximum of 24.3 and 77.2 emu/g.when the ratio of nickel to zinc is 0.5:0.5 being Ni0.5Zn0.5Fe2O4.With the increase of pH value,the effective magnetic permeability and saturation magnetization of NiZn ferrite decreased after the first increased.The saturation magnetization of the sample reached a maximum of 77.2 emu/g at a pH of 10.3,and the effective permeability of the sample was 24.3.The sintering temperature had great influence on the magnetic properties of Fe@NiZn ferrite soft-magnetic composite magnetic powder cores.At 600 ?,the composite had better magnetic properties.As the content of NiZn ferrite increased,the frequency stability of the composite magnetic powder core became better,and its saturation magnetization gradually decreased.The NiZn ferrite with a mass fraction of 3%was the optimal cladding of the composite magnetic powder core.When the heat treatment temperature was 600?,the mass fraction of ferrite was 3%,and the oxygen content was 9%,the saturation magnetization and the permeability of the composite both reach a maximum of 173.3 emu/g and 64.2.