Strontium ferrites/graphene (SrFe12O19/G) composites were synthesized by a facile one-step surfactant assisted hydrothermal method. The structure, magnetic properties and electromagnetic parameters of the as-prepared composites were evaluated. Uniform SrFe12O19 nanoparticles with a diameter of 60–70 nm were well distributed on the graphene. The formation of SrFe12O19 nanoparticles and the reduction of graphene oxide were accomplished simultaneously. The re-stacking of graphene sheets and the aggregation of SrFe12O19 nanoparticles were inhibited. The as-obtained composites exhibited better absorbing properties than the pristine SrFe12O19 particles due to the synergistic effect of SrFe12O19 and graphene. The minimum reflection loss (RL) of SrFe12O19/G composites with the thickness of 3 mm reached −34.8 dB at 13.6 GHz, and the effective absorption bandwidth (RL < −10 dB) was 5.7 GHz. However, the minimum RL of the SrFe12O19 particles only reached −13.5 dB, and the effective absorption bandwidth was 4.6 GHz. A possible mechanism for the enhanced absorbing performance was proposed.
Yu Zhou,Wenjun Zhou,Chunhua Ni,Shenggang Yan,Liangmin Yu,Xia Li
Precursors of a nickel-based metal–organic framework, denoted Ni-MOF, and the loofah plant were prepared by the microwave method, and “tree blossom” Ni/Nitrogen doped Carbon (NC)/ Carbon (C) composites were prepared by in situ pyrolysis under an argon atmosphere. During pyrolysis, the morphology, specific surface area, porous structure and electromagnetic parameters of the Ni/NC/C composites were adjusted by adjusting the pyrolysis temperature. The maximum reflection loss of the corresponding Ni/NC/C composites can reach −63.1 dB at 13.84 GHz and a thickness of 2 mm when the pyrolysis temperature was 650 ℃ and the filling amount was 16 wt%. And the effective absorption bandwidth was 35.44 GHz when the thickness was adjusted from 1 mm to 5.5 mm within the range of 2–40 GHz. Excellent performance comes from conduction loss, dipole and interface polarization, magnetic resonance, multiple electromagnetic reflections and scattering, and equilibrium impedance matching.
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