Preparation And Electromagnetic Wave Absorbing Properties Of Carbon-based Composites Derived From Metal-organic Frameworks

With the rapid development of communication and military technology,electromagnetic wave(EMW)is widely used in military and daily life,resulting in increasingly serious electromagnetic interference.Therefore,developing high-performance electromagnetic wave absorption materials(EMWAs)is of great significance.Carbon-based materials are widely applied in electromagnetic wave absorption due to their advantages of low density,high dielectric loss and good chemical stability.In recent years,porous carbon-based EMWAs derived from metal-organic frameworks(MOFs)have attracted wide attention because of their high specific surface area and ordered porous structure.However,the small aperture,single morphology and level of MOF-based EMWAs limit the absorption bandwidth of EMWAs.In this paper,we synthesized HKUST-1(Cu)as the precursor,after catalysis,carbonization and chemical washing,the EMWAs with hierarchical porous structure were prepared.The impedance matching of the material was effectively regulated by adjusting the size and distribution of the pores and compounding with magnetic material,obtaining high electromagnetic wave absorption performance.The main work details are listed as follows:(1)HKUST-1(Cu)was prepared by hydrothermal method,carbon fiber bundles(MCFB/Cu)was obtained by adding ammonium heptamolybdate as the catalyst for catalysis and carbonization at high temperature,and the metal-organic framework-derived hierarchical porous carbon fiber bundles(MCFB)was obtained after washing.(2)The size and distribution of the pores in the sample were regulated by changing the concentration of catalyst and carbonization time.By changing the concentration of catalyst,a reflection loss of-70.7 dB at 12.9 GHz and an effective absorption bandwidth of 4.31 GHz were obtained.By changing the concentration of catalyst and carbonization time,the MCFB-8h-20%sample obtained strong absorption below-10 dB in Ku,K and Ka bands within the thickness range of 0.8-1.9 mm,and the density was merely 1.17 cm~3/g.The absorbing mechanism of materials is mainly originated from the multiple scattering and dipole polarization of the hierarchical porous structure.(3)In order to further broaden the EMWA bandwidth,we prepared MCFB/Y2Co8Fe9composite by combining dielectric material MCFB with the rare earth material Y2Co8Fe9.By adjusting the filling radio of MCFB,a broadband MAMs with good impedance matching and strong absorption can be obtained.When the filling ratio was 0.1 wt%,the composite showed the optimal MA performance.When the thickness was 1.44 mm,the minimum reflection loss(RL)was-64.79 dB and the effective absorption bandwidth was 5.02 GHz.In this paper,a MOF-derived hierarchical porous carbon EMWAs with broadband was prepared,improving the impedance matching and broadening the bandwidth of the material.This study provides a new idea for the design of efficient MOF-based EMWAs.