| Nowadays,with the rapid development of electronic technology such as information technology and wireless communication,people pay more attention to the problem of electromagnetic radiation pollution.Excessive electromagnetic radiation not only interferes with the normal operation of high-precision equipment,but also causes the huge threat to the human health.The need for stealth technology in the military field is urgent.Hence,it is of great significance to explore the light-weight and high-performance electromagnetic wave absorption composites.Metal-organic framework（MOF）materials serve as ideal precursors to synthesize diverse magnetic MOF-derived carbon composites with controlled pyrolysis processes in an inert atmosphere.The magnetic MOF-derived carbon composites with polypyrrole（PPy）can reasonably balance the magnetic loss and dielectric loss,and have the characteristics of light weight,strong electromagnetic wave absorption performance,and good impedance matching,which have great development potential in the field of microwave absorption.Therefore,in this paper,starting from the acquisition of absorbing materials with multiple loss mechanisms,three magnetic MOF-derived carbon/PPy composites were prepared,and their phase compositions,microstructures,magnetic properties and absorbing properties were characterized and studied.The main contents are as follows:（1）A novel N-doped rod-like Fe-MOF was prepared by an improved two-ligand strategy,then the rod-like Fe/Fe3O4/Fe N/NC（FON/NC）composites were obtained,followed by a high-temperature calcination process.The polypyrrole（PPy）shell was coated on the outer side by a facile polymerization method to obtain Fe/Fe3O4/Fe N/NC@PPy（FON/NC@PPy）composites.The effects of different filler loadings（20 wt%,25 wt%,30 wt%and 35 wt%）on the electromagnetic wave absorption properties of FON/NC@PPy composites were discussed.The results showed that the composite exhibits the best absorbing performance under the loading condition of 30 wt%filler.The minimum reflection loss of the composite material could reach-60.08 d B with the absorption thickness of only 1.44 mm.The widest effective absorption bandwidth of 5.06 GHz could be obtained with the thickness of 1.64 mm.（2）One-dimensional magnetic nanowires were prepared by chemical reduction method with an external magnetic field,and then MOF derived Co/C was coated on the Ni nanowires through self-assembly and high-temperature calcination.Finally,the PPy was coated on the outer layer by polymerization reaction,the one-dimensional Ni@Co/C@PPy composite was obtained.The addition of Co/C and PPy could provide more dielectric loss,which make up for the deficiencies of Ni nanowires in terms of absorbing properties.Compared with single Ni nanowires,the core-shell structure formed by Co/C and PPy induces more reflection/scattering,The as-prepared Ni@Co/C@PPy composite exhibited great electromagnetic wave absorption performance.Under the filler loading of 30 wt%,the composite material showed the minimum reflection loss of-48.76 d B with the absorption thickness of merely 2.0 mm,and the corresponding effective absorption bandwidth of 5.10 GHz.Meanwhile,the widest effective absorption bandwidth could reach 5.54 GHz（7.24-12.78 GHz）with the thickness of 2.2 mm.（3）Bimetallic MOF derived leaf-like Co Zn/C carbon/magnetic composites were prepared by an aqueous self-template method and high-temperature calcination.Then the flower-like Mo S2 and PPy shell were prepared by hydrothermal and polymerization to obtain Co Zn/C@Mo S2@PPy composite.The results showed that the as-prepared Co Zn/C@Mo S2@PPy composites exhibited a reflection loss of-49.18 d B and a corresponding effective absorption bandwidth of 4.56 GHz with the thickness of merely1.5 mm.It could be concluded that Co Zn/C@Mo S2@PPy composites exhibited better performance than Co Zn/C and Co Zn/C@Mo S2 composites at low thickness range（<2mm）.After coating the dielectric material Mo S2 and the conductive polymer PPy,the leaf-like Co Zn/C@Mo S2@PPy composites have strong absorption at the thinner thickness,including wider effective absorption bandwidth,which significantly improved the electromagnetic wave absorption performance.In summary,three magnetic MOF-derived carbon/PPy composites with different morphologies were designed and fabricated using traditional metal（Fe,Co）based MOFs as precursors.The impedance matching of the material could be optimized by compounding with the functional absorbing material,and the shortcomings of the material such as weak absorption and narrow absorption were improved.In addition,the influence of different filler loadings of absorbing materials on the electromagnetic parameters was explored,which had certain guiding significance for the preparation of new,lightweight and efficient MOF-derived composite absorbing materials. |
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