Preparation And Modification Of Co₂Y Ferrite(Ba₂Co₂Fe₁₂O₁₉)Microwave Absorbing Material

In recent decades,with the development of communications technologies and military equipments,electromagnetic waves exist everywhere in our working and living environment.To solve the electromagnetic interference and meet the electromagnetic stealth requirements of military equipment,the research and development of new high-performance microwave absorption materials has become an important issue in the civil and military fields.In this paper,Y-type(Ba2Co2Fe12O22)ferrite fibers were prepared by sol-gel method and mechanical spinning method.The effects of doping content,sintering temperature,and thickness of the absorbing coating on the phase structure,composition,morphology and the microwave adsorption properties of the materials were thoroughly studied.The results show that the Y-type ferrite microfiber absorbing materials have excellent microwave absorbing properties;the Zn2+ doped Y type ferrite shows better reflection loss and wider effective bandwidth;double-layered absorber based on Y-type ferrite microfiber and carbon nanofiber is an excellent way to improve the performance of microwave absorption.The specific research results are as follows:1.Preparation and microwave absorption properties of Y-type ferrite microfibers.It was found that the microfiber material exhibits more excellent microwave absorbing properties than the Y-ferrite particulate material at the same calcining temperature.When the absorbing coating thickness is 2.5 mm,the minimum reflection loss value is—13.6 dB and the effective absorption bandwidth is 5.7 GHz for the microfiber,In comparison,all the Y-type ferrite particles did not exceed-10 dB in reflection loss at the same thickness of 2.5 mm.2.For the Zn2+-doped Y-type ferrite microfibers,by adjusting the different Zn2+ratios,a set of samples with the formula of Ba2Co2-xZnxFe12O22(x=0,0.5,1.0,1.5,2)was obtained.The electromagnetic performance test shows that the Ba2Co0.5Zn1.5Fei2O22 sample has the best microwave absorption performance.When the coating thickness is 3 mm,the minimum reflection loss value is—25.4 dB,and the effective bandwidth is 9.8 GHz(5.6-15.4 GHz).3.Microwave absorption properties of Y-type ferrite microfiber and carbon nanofiber composites.Within the range of the studied experimental conditions,when the ferrite material was used as the matching layer and the carbon nanofibers were used as the absorber layer,the double-layered wave-absorbing composite material shows better absorbing performance with stronger reflection loss and wider effective bandwidth than the single Y-type ferrite micron fiber.The double-layer absorber has a minimum reflection loss value of—74.8 dB,while the effective bandwidth is a maximum of 13.2 GHz,covering 73.3%test range.Compared with the recently reported ferrite absorbers,the microfiber materials prepared in this work have the advantages of traditional ferrite absorbers,and they have improved absorption performance.Doping Zn2+ instead of Co2+ makes the wave absorbing properties of Y-type ferrite microfibers significantly improved.The double-layered wave-absorbing materials not only improve the microwave-absorbing properties but also effectively reduce the weight and thickness of the absorbing coating.The studies are expected to prepare absorbing materials with better performance to further meet the actual requirements of 'thinness,lightness,wideness,and strength' for potential applications.