Component Modulation Of Ferrite Absorbers And Wave Absorption Properties Of Magnetoelectric Composites

In recent years,with the development of computer and communication technology,many devices have been operating at frequencies close to the GHz range.The higher operating frequencies have led to serious electromagnetic interference and radiation pollution,and this pollution has caused very serious health and environmental problems.In order to solve these problems,the development of absorbent materials is increasingly important.Ferrite materials have been one of the main focuses of absorber research due to their high magnetic permeability,chemical stability,and low cost.However,the low microwave absorption performance,narrow absorption band,material specific gravity,poor thermal stability and other shortcomings,It still affects the inability of ferrites to meet the requirements of high absorption,wide frequency range,light mass and low thickness.Therefore,their overall performance can be improved by ionic substitution,multiple compounding and structural specialisation.This experiment investigates several different ways of improving the performance of ferrite absorbing materials,the main elements of which are as follows:（1）First,Manganese-doped W-type barium ferrite Ba Mn_xCo_2-xFe₁₆O₂₇（x=0.0、0.2、0.4、0.6、0.8）prepared by sol-gel self-propagation combustion,The effect of different doping amounts on the morphological structure and electromagnetic parameters of the barium ferrite was investigated.the results show that the sample has a W-shaped hexagonal structure with a larger radius of substitution ions compared to cobalt ions,which leads to an increase in the lattice parameters.the doping of Mn elementsimproves the dielectric loss and enhances the attenuation of electromagnetic waves.The final sample with a doping of x=0.4 after calcination at 1250°C for 3 h reached a reflection loss of-41.78 d B at 7 mm and an effective bandwidth of 2.475 Ghz.（2）Secondly,the conductive polymer PANI was homogeneously coated onto the surface of W-type barium ferrite Ba Co₂Fe₁₆O₂₇particles synthesized by the sol-gel method using an in situ polymerisation process,and the phase composition,morphology,magnetic properties,and microwave absorption properties of the polypyrrole/ferrite composites were analysed and discussed.The efficient microwave absorption performance of the PANI@Ba Co₂Fe₁₆O₂₇composite is the result of multiple loss mechanisms and perfect impedance matching with significant electromagnetic wave absorption.A minimum reflection loss of-40.4 d B at 2.9 GHz was achieved when the thickness was 6.0 mm.（3）Finally,hierarchical hollow Co Fe₂O₄/polypyrrole nanocubes（CF@PPy-1,CF@PPy-2 and CF@PPy-3）with enhanced electromagnetic properties were prepared by a combination of self-sacrificing templates and in situ polymerisation.The Co Fe₂O₄@PPy HNCs composites were characterised by different test methods.The results show that PPy is uniformly encapsulated on the surface of Co Fe₂O₄nanocubes,forming a unique hierarchical hollow structure.By adjusting the polypyrrole ratio to tune the electromagnetic properties,the right amount of PPy coating gives the Co Fe₂O₄@PPy composite improved impedance matching and multiple loss mechanisms.Finally,the CF@PPy-2 achieves a minimum reflection loss of-43.85 d B at a thickness of 3.0 mm at 9.7 GHz and a wide effective bandwidth of 5.7 GHz at a thickness of 2.0 mm.