Preparation And High Frequency Electromagnetic Properties Of Submicron Amorphous Fe-B

With the development of power electronics and information technology,there is an increasing demand for high frequency,integration and high performance of devices to meet the development needs of communication,Internet of Things,electromagnetic compatibility and microwave engineering.Therefore,the research and development of high-frequency electromagnetic materials has become a popular research topic,and how to make materials in the field of high frequency still maintain high permeability and low magnetic loss is a difficult point in the research.Compared with conventional metallic magnetic materials,amorphous soft magnetic alloys have low coercivity and high permeability due to the disorderly arrangement of atoms in the alloys and the anisotropy of magnetic crystals tending to zero.At the same time,since amorphous alloys usually add elements such as Si,B,and P to maintain their amorphous state,and the addition of these elements will greatly increase their resistivity,thus reducing the eddy current loss of the material.Amorphous soft magnetic powder can also be adjusted by the size of the particles to regulate the permeability and eddy current loss,these characteristics make the amorphous soft magnetic powder in the field of high frequency applications have certain advantages.Therefore,Fe-B amorphous is chosen as the object of study in this paper.Submicron spherical amorphous Fe-B were prepared using the liquid-phase reduction method,and the effects of Fe²⁺concentration,Na BH₄ drop acceleration and the amount of Na BH₄ on the microscopic morphology,static magnetic properties of particles and composites'electromagnetic were studied.The results show that the spherical Fe-B/polyurethane(PU)composite(80 wt%)has^?of 2.61 and^?of 12,and the sample has a high domain wall resonance frequency and a small eddy current loss according to magnetic spectrum fitting.In order to investigate the application of Fe-B amorphous in high frequency antennas,this experiment uses HFSS to simulate microstrip patch antenna with spherical Fe-B/PU composite(80 wt%)as the substrate material.The simulation results show that the area of the antenna is reduced by 88.1%near 1 GHz compared to the FR4-based antenna,which greatly reduces the size of the antenna.In order to further reduce the domain wall resonance intensity of spherical amorphous Fe-B,high aspect ratio amorphous Fe-B chains were prepared by using magnetic field induction.The effects of magnetic field intensity on the microscopic morphology,static magnetic properties,amorphous degree of particles and the complex permeability of the composites were studied.The composite(80 wt%)made by the optimal sample has^?of 3.05,^?of 19.32,tan_?of 0.04 and tan_?of 0.13 at 1GHz.It is proved by the magnetic spectrum fitting that the domain wall resonance intensity is greatly reduced compared with that of spherical Fe-B,so that its tan_?is lower and can still maintain a high^?value in the high frequency band.The composite was used as a substrate to design a microstrip patch antenna and simulated at different working frequency bands.The results show that when the working band is1 GHz,the area of the antenna is reduced by 90.9%compared to the FR4-based antenna and has good impedance matching;when the working band is 2 GHz,the antenna area is reduced by 92.3%comparing with the FR4-based antenna and by 43.3%comparing with the spherical Fe-B/PU composite-based antenna,and the gain is slightly higher than that of the latter.These demonstrates that the chain structure is beneficial to reduce the magnetic loss of magnetic material and improve the antenna performance.Meanwhile,in order to explore the application of Fe-B amorphous in the field of high-frequency wave absorption,we prepared composites with a mass fraction of 80%by using spherical Fe-B particles and chain-like Fe-B particles as fillers,respectively.And the wave absorption performance at different thicknesses was calculated based on the electromagnetic parameters obtained from the tests.The results show that the absorbers prepared using spherical Fe-B/PU composites reach their strongest absorption peak at 24.04 GHz with a peak intensity of-47.94 d B and a peak width of5 GHz(RL<-10 d B)at a thickness of 0.88 mm.