| Following rapid development of the electronics industry and wireless communication,exploring high-performance electromagnetic(EM)wave absorption materials has been attracting considerable attention.For meeting the requirement of excellent microwave absorption,it is usually required to possess multiple merits such as lightweight,strong absorption,broad frequency band and high thermal stability,all of which are directly related to the components and microstructures of absorbers.An ideal electromagnetic wave absorbing material should be lightweight and exhibit high absorption efficiency in a broad frequency band at a low filler loading ratio.Although single magnetic material or single dielectric material have a certain property of microwave absorption,those materials show poor absorption in the microwave frequency region ascribed to the poor electromagnetic matching between absorbers and air.Therefore,the integrating of magnetic material and dielectric material is an effective way to resolve this problem by improving the electromagnetic matching between absorbers and air.The microwave absorption capacity is also related to the electromagnetic matching between the microwave and materials,and intrinsic electromagnetic properties,like complex permeability(?r=?'-i?")and permittivity(?r-?'-i?")which could be enhanced by controlling the microstructure of absorbers and integrating magnetic or dielectric compositions.In this paper,we will explore the microwave absorption of Fe@SiC composites by ball mailing to control the microstructure and changing the mass ratio of magnetic/dielectric material to change the thickness of the dielectric material shell.The main research results of this paper are as follows:Flake-like Fe@SiC composites were synthesized by a combined approach consisting of ball-milling and heat-assisted surface adhesion processes.The experimental results indicate that the Fe micropowders with an initial size of 30-40 ?m can be completely milled into a flake-like shape with the diameter of 35 ?m and the thickness of 10 ?m after 5 h ball-milling,and then the flakes would be further fractured to smaller pieces as increasing the milling time.The as-made Fe flakes were subsequently encapsulated within SiC nanopowders by high-speed mixing at 120? for 2 hours under nitrogen atmosphere.By turning the ball-milling time and the Fe/SiC ratios,the reflection loss(RL)could be optimized to-10 dB in the frequency ranges of 21.5-22.3 GHz and 20.1-26.5 GHz for the absorber thicknesses of 0.3 mm and 0.5 mm,respectively.In particular,the maximum RL peaks for the flake-like Fe@SiC composites shifted to higher frequencies compared with the spherical Fe@SiC composite due to the increased magnetic anisotropy.The enhanced microwave absorption properties are a synergistic effect of magnetic loss and dielectric loss,resulting from the heterogeneous components,and their proper electromagnetic impedance matching.We synthesized the controllable magnetic/dielectric Fe/SiC hybrids with a combined approach consisting of heat-assisted surface adhesion processes,and further controlled the SiC thicknesses by adjusting the thickness of SiC components.The optimized microwave absorption performances reached the minimum reflection loss of-51 dB at the absorber thickness of 1.6 mm and an absorption<-10 dB bandwidth of 7.5 GHz at 18-26.5 GHz.This also proves that it has good absorbing properties.As the thickness of the shell increases,the absorbing material has a thinner thickness,a wider absorbing band and a smaller reflection loss value.The present study shows an efficient and lowcost approach to realize Fe/SiC hybrids as a promising microwave absorbent. |
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