Fabrication And Properties Of Fe Based SMCs With High Saturation Magnetization

Soft magnetic materials(SMCs)are new type of functional materials.They have been fully noticed and developed by researchers in recent years.Among them,SMCs with high effective permeability and low loss are widely applyed in areas such as electric,power and telecom industries.In modem society,with the revolutionary development of power and electric industries,it is significant to keep frequency stability and low loss while maintaining SMCs’ high saturation magnetization.For the purpose of reaching high property standard,researchers usually consider to introduce a high resistivity coating layer on the surface of metal magnetic powders,the well coated insulating coating can decrease the current loss of metal soft magnetic powder under magnetic field,and consequently be used in high frequency environments.Insulating adhesives is a common method of insulating coating.Insulating coating and adhesive could be reached simultaneously by this method.In addition,there is another common insulating coating method-atmosphere heat treatment:the surface of soft magnetic powders will form an insulating phase and structure by heat treatment.Usually,materials with high resistivity are non-magnetic,thus in order to obtain high insulating coating performance while keep high saturation magnetization,magnetic Fe3O4 phase is used to reduce the magnetic dilution effect.In this paper,two methods were introduced to fabricate:1,Novel inorganic-organic insulating adhesives composite coating on the surface of Fe based SMCs.2,Nitridation followed by oxidation heat treatment to prepar Fe based SMCs.In this study,we carried out measurements like XRD,SEM,XPS,TEM,SQUID,and TG to test the core-shell structure SMCs.The correlation between material structure and magnetic performance is systematically described and concluded as follows:1,Introducing SiO2 and Fe3O4 nanoparticles into epoxy-modified silicone resin can effectively enhance the insulating property of coating,also the introduction of magnetic phase Fe3O4 avoids magnetic dilution effect as well.1)The well dispersed with high resistivity SiO2 nanoparticles were introduced into ESR by hydrolysis condensation,the resistivity,thermal stability and mechanical strength of SMCs are enhanced.2)The SMCs containing SiO2 and Fe3O4 exhibit optimized magnetic performance with high effective permeability(～124.6)and low core loss(～807.8 mW/cm3)due to combined high electrical resistivity of the SiO2 and reduced magnetic dilution induced by the Fe3O4.2,High resistivity insulating coating is formed by atmosphere heat treatment method,which maintain relatively high saturation magnetization and prevent magnetic dilution effect.The optimized atmosphere heat treatment condition was founded by nitridation and nitridation followed by oxidation.We focused on the research reaction mechanism of insulating layer by nitridation and oxidation.1)The samples nitrided under different temperature and followed by different oxide temperature condition.We found that iron powder has optimized soft magnetic property at 300 ℃ nitridation followed by 200 ℃ oxidation,where the effective permeability reached to 104.0 and the core loss got the lowest(810 mW/cm3).2)Iron powder nitride at 300 ℃ has the fastest oxidation speed.Under the same condition,iron powder has the thickest oxidation layer.The insulating layer is a dual layer after nitridation followed by oxidation.The outer layer is Fe2O3 while the inner layer is Fe3O4.This specific dual iron oxide insulating coating attribute to higher resistivity,and the inner Fe3O4 decrees the magnetic dilution effect.