Synthesis And Electromagnetic Wave Absorption Properties Of One Dimensional Magnetic Metal-based Nanomaterials

Serious electromagnetic interference problems not only threat national defense but also harm human's healthy.Thus,it is significant to exploit ideal electromagnetic wave absorption materials to consume electromagnetic wave efficiently.Nanomagnetic metals have been received much attention for its compatibility of dielectric loss and magnetic loss.Yet,nanomagnetic metals have strong skin-effect for its ultrahigh conductivity,inhabiting the fluent entrance of electromagnetic wave.What's more,large Snoek's limits weak electromagnetic wave absorption capacity at high frequency for magnetic metals.Hence,in this paper,we have emphasized on reforming magnetic nanomaterials,well combining of dielectric loss and magnetic loss,enhancing absorption capacity.One dimensional magnetic nanomaterials have improved magnetocrystalline anisotropy,which can break Snoek's limits,promoting enhanced permeability.Combining one dimensional magnetic metal with low dielectric materials can further impair high permittivity of metals.In this paper,series of methods have been adopted to improve the complementarities of permittivity and permeability.1:Chain-like MxFe3-xO4/CoNi(M=Co,Ni)complex structures have been successfully synthesized in the present of magnetic field by solvothermal method,and the as prepared complex is about tens micrometers in length assembled by submicron spheres 500 nm in diameter.The results show that this structure and components exhibits excellent electromagnetic wave absorption capacity,the efficient bandwidth is about 6 GHz(reflection loss<-10 dB)and the strongest reflection loss is up to-20 dB at the thickness of 1.5 mm.While either the chain-like structure or MxFe3-xO4/CoNi(M=Co,Ni)components is destroyed,the absorption capacity can't be well sustained.2:Chain-like CoNi@MOF-74(Ni)core@shell structures have been successfully constructed through self-sacrificed template method by chain-like CoNi alloys as precursor and 2,5-dihydroxyterephthalic acid as ligands.The results show that the as prepared core@shell structure owns appropriate permittivity as well as sustained permeability in all frequency compared with the chain-like CoNi alloys at a certain thickness of shell.Thus,this structure can have well impendence matching at the range of 14-17 GHz,and in this 3 GHz range the reflection loss lower than-20 dB(99%absorption).3:Segmented Fe@C York@shell structures have been well obtained when annealed Fe3O4@phenol formaldehyde resins core@shell structure,which is synthesized by hydrothermal method successfully,at 600 °C at Ar/H2 atmosphere.And this structure has enhanced electromagnetic wave absorption capacity for its more reasonable permittivity and improved permeability,at the thickness of 1.5 mm,the efficient bandwidth is up to 7.0 GHz while at the thickness of 2.0 mm,the efficient bandwidth covers all X-band(8-12 GHz).