The Research On Electromagnetic Wave Absorption Performances Of Hollow Carbon Nanospheres Composites With Fe₃O₄ And Co

Hollow carbon nanospheres?HCN?have the characteristics of light weight and good electrical conductivity,which can be applied in many fields.However,the relative dielectric constant of HCN is high,and only tiny amounts of incident electromagnetic waves can be attenuated by the HCN,resulting in poor electromagnetic wave absorption performance.It is found that the electromagnetic parameters of the composites composed of HCN and magnetic particles can be effectively adjusted,and the absorption performance can also be significantly improved.In this paper,HCN was successfully synthesized by soft template method.On this basis,Fe₃O₄/HCN composites and Co@HCN core-shell composites were prepared and their electromagnetic wave absorption properties were studied.The main contents are as follows:Fe₃O₄ and Fe₃O₄/HCN composites were prepared by chemical precipitation method.In composites,Fe₃O₄ nanoparticles take HCN as template and embedded on its surface forming small bulges.With the increase of Fe₃O₄ in the system,the Fe₃O₄ nanoparticles on the surface of HCN gradually increased and grew up.The electromagnetic wave absorption properties of each sample were tested.The results show that the Fe₃O₄/HCN-2/1 composite has excellent electromagnetic wave absorption properties,and the reflection loss can reach-63.9 dB at a thickness of 1.5 mm with a frequency of 13.5GHz,the effective absorption bandwidth?reflection loss below-10 dB?is 7.2 GHz.In addition,the thickness of Fe₃O₄/HCN-2/1 composite is in the range of 1.2⁴ mm,and the frequency is in the range of 4.2¹5.0 GHz,the reflection loss can reach-20 dB?99%electromagnetic waves are absorbed?.Co@HCN core-shell composites were prepared by switching liquid phase transport of active substances and high-temperature reduction method.Co nanoparticles attached to the edge of the cavity of HCN and crystallize grew.With the increase of Co content in the system,the core-shell structure is gradually becoming obvious.The electromagnetic wave absorption performance of the composites were tested.It was found that the absorption properties of Co@HCN composites were improved.Among them,Co@HCN-1/1core-shell composite has the best electromagnetic wave absorption performance.At the thickness of 2.4 mm and the frequency of 12.0 GHz,the reflection loss can reach-61.5 dB,and the effective absorption bandwidth is 7.3 GHz?8¹5.3 GHz?.Moreover,by adjusting the thickness of the Co@HCN-1/1 absorber,the reflection loss can reach-20 dB at 5.9¹8 GHz with the thickness of 1.5⁴ mm.