Synthesis And Electromagnetic Properties Of Magnetic/Electrical And Electrical/Electrical Compound Absorbent

Absorbent is the main source of absorbing properties of absorbing materials.With the wide application of absorbing materials in military and civil fields,it has become an important research direction to obtain absorbent with higher performance to build absorbing materials with large absorption bandwidth,strong absorption capacity,light weight and thin thickness.Starting from the design and regulation of the composition,structure and electromagnetic characteristics of the absorbent,the preparation of new electro-magnetic composite absorbent and dielectric dielectric composite absorbent was carried out in this paper.The main research and conclusions are as follows:Using an improved st(?)ber method,carbonyl iron powder(CIP)is coated with silicon dioxide and nitrogen-doped carbon(NC)by dopamine self-polymerization and carbonization in a nitrogen atmosphere,and then alkaline hydrothermal etching was carried out on silicon dioxide layer to prepare CIP@void@NC.The analysis of chemical composition,crystal phase structure and microscopic morphology proves that the CIP@void@NC is a yolk-shell structure with CIP as the spherical core and NC as the spherical shell.Evenly mixed with paraffin to measure electromagnetic parameters within 2-18 GHz frequency range;and according to the transmission line theory,it is calculated that the absorbing material composed of 70 wt% CIP@void@NC can reach the minimum reflectance of-25.7 dB at 17.2GHz;the effective absorption bandwidth(absorption rate ? 90%)can reach 6.9 GHz(11.1-18 GHz)at a thickness of 1.7 mm absorbing material.The absorbing properties are derived from the dipole orientation polarization and interface polarization brought by the unique structure,the synergistic effect of dielectric and magnetic losses,as well as the impedance matching and quarter-wavelength interference cancellation.Nitrogen-doped graphene(NG)/ stannic oxide hollow sphere hybrids was synthesized by hydrothermal method using silicon dioxide as template,urea as nitrogen source and reducing agent.Its chemical composition,crystal phase structure and microscopic morphology prove that the stannic oxide hollow sphere are evenly dispersed on the surface of the nitrogen-doped graphene and between the nitrogen-doped graphene sheets,forming a spatial sandwich structure.Evenly mixed with paraffin to measure electromagnetic parameters within the 2-18 GHz frequency range;and according to the transmission line theory,the effective absorption bandwidth(absorption rate ? 90%)can reach 4.2 GHz when the thickness of the absorbing material composed of 40 wt% NG/stannic oxide hollow sphere hybrids is 1.3mm;when the thickness of the absorbing material is 2.3 mm,the minimum reflectance can reach-50.3 dB at 8.6 GHz.The absorption performance is attributed to good dielectric loss,better impedance matching,multiple scattering and quarter-wavelength interference cancellation.Magnetic loss-dielectric loss component recombination,dielectric loss-dielectric loss component recombination make composite absorbents have a richer loss mechanism,and provide new ideas for the design of new absorbents.