Study Of Preparation And Electromagnetic Wave Absorption Properties Of Fe-based Magnetic Micro/nano Particles And Its Composites

Electromagnetic wave generated by electronic equipment not only brings great harm to the normal work of electronic devices,but also threat people's physical health.The most effective shielding method to control electromagnetic pollution is using absorbing materials to absorb electromagnetic waves,so the research of absorbing materials has great engineering application value.In this paper,Fe-based magnetic micro/nano particles were selected as the object of study,aiming to explore its high-frequency electromagnetic dynamic response characteristics,mechanism and absorption properties.The research contents and results are as follows:?1?Fe-B particles were prepared by liquid phase reduction method,and the effects of NaBH₄ addition,FeSO₄/NaBH₄ ratio and NH₃·H₂O content on the morphology,boron content,crystal structure and static magnetic properties of Fe-B particles were systematically studied.Electromagnetic wave absorbption properties of Fe-B particles/paraffin samples with different boron content and particle size were also studied.Results showed that the Fe-B particles were spherical and amorphous.With the FeSO₄/NaBH₄ ratio decreasing from 1/1 to 1/6,average size of the spherical amorphous Fe-B particles changed little?132-167 nm?,while the boron content increased from 18.50at.%to 32.09 at.%.With NH₃·H₂O content increasing from 50 ml to 200 ml,boron content of spherical amorphous Fe-B particles didn't change significantly?25.52-28.68 at.%?,while the average particle size increased from 120 nm to 370 nm.The boron content and particle size both have significant influence on the electromagnetic wave absorption properties of Fe-B particles.With the increase of the boron content,both|RL_max|and the maximum effective absorption bandwidth of Fe-B particles/paraffin samples?Fe-B particles:70 wt.%?increased firstly and then decreased.With the increase of particle size,the maximum effective absorption bandwidth of the Fe-B particles/paraffin samples increased first and then decreased.Fe-B particles with boron content of 27.12 at.%and an average particle size of 250 nm exhibited the widest effective absorption bandwidth of 7.6 GHz and its|RL_max|was 42.843 dB,showing excellent electromagnetic absorbing ability.?2?The spherical amorphous Fe-B particles were annealed at 400?,500?and600?.The effects of annealing temperature on the morphology,crystal structure,static magnetic properties and electromagnetic wave absorption properties of Fe-B particles were investigated.Results showed that the spherical amorphous Fe-B particles were crystallized to Fe₂B phase at 479?.With the increase of annealing temperature,saturation magnetization of Fe-B particles changed little?136.68-146.54 emu/g?,while the coercivity increased first and then decreased.Appropriate annealing temperature can significantly increase the|RL_max|of the spherical amorphous Fe-B/paraffin sample with the addition of Fe-B of 60 wt.%,However,the annealing treatment had an adverse effect on the maximum effective absorption bandwidth of spherical amorphous Fe-B/paraffin sample.?3?The Fe-B/SiO₂ composite particles with shell-core structure were prepared by surface coating of Fe-B particles by Stober method.The morphology,crystal structure,static magnetic properties and electromagnetic wave absorption properties of the composite particles were characterized.Results showed that compared with Fe-B particles/paraffin sample,|RL_max|and the maximum effective absorption bandwidth of Fe-B/SiO₂particles/paraffin sample were both reduced.?4?FeNi₃ particles with different morphologies?FeNi₃ spheres,FeNi₃ acanthospheres and FeNi₃ chains?were prepared by ultrasonic assisted liquid phase reduction and their electromagnetic wave absorbption properties were studied.Results showed that the morphology of FeNi₃ particles had great effect on their electromagnetic wave absorbption properties.For the FeNi₃ spheres,FeNi₃ acanthospheres and FeNi₃ chains prepared in this experiment,in the range of 2-18 GHz.|RL_max|:FeNi₃ spheres<FeNi₃ acanthospheres<FeNi₃ chains,the maximum effective absorption bandwidth:FeNi₃ spheres>FeNi₃acanthospheres>FeNi₃ chains.The maximum|RL_max|of FeNi₃ chains had the largest value of 54.130 dB,and the maximum effective absorption bandwidth of the FeNi₃ spheres was the widest,which was 7.22 GHz.