Fabrication And Microwave Absorption Properties Of Iron Based Core@shell Structural Nanocomposites

With the rapid development of electronics,the electromagnetic radiation has made a series of bad influences on equipment operation quality and information transmission security.Electromagnetic absorbing material is one of the most effective methods to solve these tough problems,which could not only absorb the radiation source from electronic component,but also the source from external devices.Microwave absorption materials are usually in connection with the components and microstructures of absorbers.The microwave absorption capacity is also related to the electromagnetic matching between the microwave and materials,and intrinsic electromagnetic properties,like complex permeability(μr=μ’+iμ")and permittivity(εr=ε’+iε")which could be enhanced by integrating magnetic and/or dielectric compositions and specific structural units.The main conclutions are as follows:(1)Iron based core@shell nanocomposites(Fe@C,Fe@ZnO)were synthesized by insitu arc-disging in a mixture of methane(CH4)and argon(Ar),which consist of the particle sizes of 20～80 nm in diameter and the graphitic shells of 2～7 nm in thickness.Core-shell structure were very complete.(2)The complex permittivity of Fe@Graphite nanocapsules at gigahertz can be effectively enhanced up to～130%by a simple annealing procedure.Experimental results reveal that it is originated from the intrinsic polarization of atomic-scale oxygen-carbon complexes,which is ascribed to the formation of the substitutional oxygen in highly defective graphitic layers.(3)The Fe@ZnO nanocapsules composed of a ferromagnetic Fe core and a dielectric ZnO shell.By integrating such heterogeneous components in each particle,it results in reciprocal resonances for the relatively complex permeability and permittivity at～15 GHz,contributing to efficient complementarities between the dielectric and magnetic losses.Therefore,more than 90%microwave power can be attenuated at 8.2-18 GHz.X-ray photoelectron spectra reveals that the origin of reciprocal resonances is induced by the electronic interactions at Fe and ZnO interfaces.