Metal–organic frameworks (MOFs)-derived compounds exhibit tremendous potential for applications in the field of microwave absorption, attributed to their unique structural characteristics, high specific surface area, and tunable magnetic and dielectric properties. However, their practical application in the microwave absorption field is limited by poor impedance matching. To address this issue, we successfully synthesized a composite microwave-absorbing material, labeled as Fe/Fe2O3/C/N,SGPE, by introducing heteroatom (N and S) codoped graphene (labeled as N,S-GPE) into an Fe/Fe2O3/C MOF derivative and employing a solvothermal method followed by subsequent pyrolysis. The introduction of N and S codoped graphene introduces defects and disordered structures, thereby enhancing interface and dipolar polarization processes, which in turn improve the dielectric properties and optimize impedance matching. The experimental results demonstrate that when the addition amount of N,S-GPE is 0.15 g, the material exhibits a maximum reflection loss of -62.8 dB at 7.6 GHz with a thickness of 3.09 mm, capable of absorbing over 99.9999% of microwaves. Consequently, this composite stands out as a promising candidate for high-efficiency microwave absorbers.
Yan Yuefeng,Cheng Ziyan,Ma Guansheng,Chen Tao,Gao Boshi,Liu Yuhao,Huang Xiaoxiao
Reduced Graphene Oxide (RGO) has been proved to be a promising electromagnetic wave absorption (EMWA) material candidate owing to its superior electrical and dielectric properties, along with rich potential for structural design. However, the complicated synthesis process and the contradiction between impedance matching and attenuation capacity have hindered the further development and application of graphene-based absorbing materials. Herein, a Fe nanoparticle/RGO composites was synthesized through a facile in-situ chemical reduction process. The configuration of Fe nanoparticles regulates the permittivity and permeability of RGO and balances the impedance matching. The dipole polarization caused by the residual oxygen-containing functional groups in RGO, coupled with the interfacial polarization loss caused by the Fe/RGO interface, enhance the dielectric loss capacity, contributing to microwave loss in the high-frequency range. The natural resonance and exchange resonance caused by the nano Fe particles enhance the microwave loss capacity in the low-frequency range. Benefitting from the synergistic enhancement from dielectric loss and magnetic loss, Fe/RGO composites exhibit the characteristic of daul-band absorption. Notably, the sample FG-0.25 achieved an effective absorption bandwidth ( EAB ) of 5.33 GHz and a minimum reflection loss ( RL min ) of −48.9 dB. The absorption peaks in the low-frequency band can encompass a significant portion of the C-band. This research provides unique insights for the advancement of environmentally friendly and energy-efficient RGO based EMWA materials.
Jimei Xue,Xiaoling Liu,Yuqiu Wang,Hepeng Zhao,Xiaomeng Fan
Oxide ceramic matrix composites (OCMC) have good high-temperature resistance, oxidation resistance, and mechanical properties. However, the microwave absorbing properties of OCMC areinsufficient due to the low dielectric and low loss characteristics of oxide ceramics, so it is urgent to develop a kind of the oxide ceramic matrix with adjustable microstructure and electromagnetic properties. PDC-SiOC ceramics are the optimal oxide ceramics whose component and microstructure can be adjusted by rare earth nitrate modified polysiloxane precursor. For Sc(NO 3 ) 3 modified PDC-SiOC ceramics, rare earth metals not only can react with siloxy groups to form silicates at high temperatures but also can catalyze the formation of SiCnws. Herein, rare earth nitrate modified polysiloxane precursor was pyrolyzed at 900°C, and then annealing at high temperature to form silicate and SiCnws. After annealing at 1400°C, a large amount SiCnws was in situ formed conductive network structure in SiOC ceramic, so the SiOC ceramic with SiCnws had great electromagnetic wave (EMW) absorbing properties, the maximum effective absorption bandwidth (EAB max ) and the minimum reflection coefficient (RC min ) at the thickness of 2.75 mm reach 4.0 GHz and −42.3 dB in X -band, respectively. By the double-layer impedance matching design, the EAB can be effectively improved, which provide a good way for the design and fabrication of OCMC with advanced (EMW) absorbing properties.
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