Study On Synthesis And Microwave Absorption Properties Of CoFe₂O₄/FeCo And Its Composites

In recent years,microwave absorbing materials have received more and more attention in the electromagnetic environment and military stealth technology.The development of a new type of microwave absorbing material,including a strong absorption,thin thickness,wide bandwidth,and lightweight,has become an urgent requirement at present.The magnetic metal Fe,Co and their alloys stand out among many microwave absorbers due to their excellent electromagnetic properties.In this paper,FeCo alloy,CoFe2O4 and its composite materials are taken as the research object.Based on the synthesis process conditions,a series of microwave absorbing materials w:ith excellent properties are obtained.The main research conclusions are as follows:(1)Using hydrothermal reduction method,polyhedral FeCo alloy with grain size of 1-2 ?m was obtained under different holding time and Fe:Co molar ratio.Firstly,XRD results indicate that the characteristic diffraction peaks of all samples correspond to the crystal plane of body-centered cubic FeCo alloy(JCPDS No.49-1658)Secondly,EDS and EDS Mapping results show that the coexistence of Fe and Co elements is consistent with the composition of the experimental design.Finally,microwave absorption performance test results show that all samples exhibit excellent microwave absorption performance in the X band and the entire Ku band.Specifically,Fe4Co6 with a holding time of 10 h has an optimal reflection loss of-48.64 dB and an effective bandwidth of 7.28 GHz when the matching thickness is 1.4 mm,covering the X band and the entire Ku band.Furthermore,the best reflection loss of the Fe6Co4 sample when the matching thickness is 1.7 mm is-52.20 dB,and the effective absorption bandwidth is 6 GHz,covering the C-band,Ku band and the entire X band.Excellent microwave absorption performance is attributed to high magnetic performance and excellent impedance matching.(2)The hydrothermal method was used to obtain(1-x)CoFe2O4/xCoFe composites by changing the different ratios of CoFe2O4 and CoFe.FESEM results is shown that due to the strong magnetic interaction,the face-centered cubic structure CoFe2O4 adheres to the surface of the polyhedral CoFe,forming a composite material Magnetic performance test results show that the dipole interaction between the composite materials is accompanied by a weak exchange coupling behavior.In addition,composite materials have excellent microwave absorption properties.Firstly,compared to CoFe2O4 and CoFe,CoFe2O4/CoFe composites exhibit enhanced electromagnetic wave absorption capabilities owing to enhanced natural resonance and optimized impedance matching.Secondly,the absorption performance can be optimized by adjusting the ratio of CoFe2O4:CoFe and Co:Fe.Specifically,when the matching thickness is 1.45 mm,the best reflection loss of the sample 4CoFe2O4/6Co4Fe6 is-58.22 dB,and the effective absorption bandwidth(RL<-10 dB)is 4.16 GHz,covering the X band and Ku band.This achieves strong effective absorption in multiple frequency bands.(3)Using grapevine as the carbon source,microwave absorption properties of La-doped C/CoLaxFe2-xO4 composites at different ratios were studied by hydrothermal synthesis.Firstly,XRD results showed that La doping did not change the crystal structure of CoFe2O4.Secondly,XPS results show that La3+ partially replaces Fe3+.Thirdly,the BET test results show that the specific surface area of C/CoLa0.2Fe1.8O4 is 19.50 m2g-1,which is higher than the complex specific surface area of CoLao.2Fe1.8O414.71 m2g-1.Finally,the electromagnetic parameters of the material were measured and analyzed,and it was found that the C/CoLaxFe2-xO4 composite has excellent microwave absorption properties.C/CoLa0.2Fei.8O4 has an optimal reflection loss of-49.56 dB when the matching thickness is d=3.83 mm.In addition,C/CoLa0.3Fe1.7O4 shows the most excellent effective absorption bandwidth.When matching thicknesses are d=4.5 mm and d=5 mm,the effective absorption bandwidth reaches 4 GHz,covering the C band and Ku band,achieving effective absorption in multiple bands The performance enhancement is due to the optimized impedance matching by interfacial polarization and dipole polarization.(4)Using graphene as a carbon source,microwave absorption properties of La-doped N-rGo/CoLaxFe2-xO4 composites at different ratios were studied by solvothermal method.Firstly,the XPS results showed that La3+partially replaced Fe3+,and nitrogen was successfully doped into the reduced graphene oxide.Secondly,the microwave absorption performance test shows that the best reflection loss of N-rGo/CoLao.2Fe1.8O4 is-58.46 dB when the matching thickness is d=4.4 mm,and the effective absorption bandwidth reaches 3.52 GHz.In addition,N-rGo/CoLa0.3Fe1.7O4 has an effective absorption bandwidth of 3.84 GHz when the matching thickness is d=2 mm,covering the X band and Ku band.The performance enhancement is due to the optimized impedance matching and strong attenuation capability.Consequently,N-rGo/CoLaxFe2-xO4 will be a potential candidate for an excellent microwave absorber in the multi-band range.Figure[46]Table[12]References[126]...