Defect‐Engineered Graphene/Si₃N₄Multilayer Alternating Core‐Shell Nanowire Membrane: A Plainified Hybrid for Broadband Electromagnetic Wave Absorption

Abstract

To tackle the increasing electromagnetic pollution, broadband electromagnetic wave (EMW) absorption materials are urgently needed. Toward this goal, traditional strategies resort to the construction of multicomponent dielectric/magnetic hybrid materials, including ternary, quaternary, or even more complicated systems. However, they always suffer from many intrinsic drawbacks in practical applications. Herein, a theory‐directed strategy is presented to design plainified EMW absorption materials (binary hybrids) via amplified interface effects, which are based on well‐designed multilayer alternating core‐shell nanostructures by chemical vapor deposition (CVD). A defect‐engineered CVD graphene (DG) core composed of graphitic open edges and in‐plane defects is used as a lossy phase. Correspondingly, a CVD Si3N4 layer with nanometer thickness is used as an impedance matching shell. By optimizing the alternating numbers of DG/Si3N4 units, enhanced interface polarization and strong frequency dispersion behavior of permittivity (especially the real part, ε′) are obtained, which helps the plainified binary hybrids to reach an effective absorption bandwidth (EAB) of 8.0 GHz at a thickness of 2.7 mm. Moreover, these plainified hybrids show excellent thermal and pH stability. Even after 1000 °C oxidation, for example, an EAB of 7.44 GHz coupling with a minimum reflection coefficient of −77.3 dB is still achieved.

Engineering of the Core–Shell Boron Nitride@Nitrogen-Doped Carbon Heterogeneous Interface for Efficient Heat Dissipation and Electromagnetic Wave Absorption

“…That is to say, the absorption peaks of different BN@NC/WPU films moving toward low frequency at the same thickness should be attributed to the increase of ε ′ and ε″. According to Serghei’s derivation, a lower phase thickness can lead to stronger interface polarization intensity, and the strong interface polarization can theoretically lead to a high ε ′ , which can increase the value of | ε r | | μ r | . Therefore, the reason for the peaks shifting to lower frequencies may be attributed to the enhanced interface polarization between the BN and conductive carbon layer with the increasing in temperature.…”

1D CNT-Expanded 3D Carbon Foam/Si3N4 Sandwich Heterostructure: Utilizing the Polarization Compensation Effect for Keeping Stable Electromagnetic Absorption Performance at Elevated Temperature

“…Therefore, two conclusions can be deduced from the above-mentioned analysis: (1) the addition of CNTs could strengthen the conductive loss. (2) The Si 3 N 4 coating layer helps enhance impedance matching …”

“…(2) The Si 3 N 4 coating layer helps enhance impedance matching. 43 In addition, compared to S-1-Si 3 N 4 , S-0-Si 3 N 4 has low conductive loss and a larger EAA, which could be attributed to its larger Z area (as shown in Figure 2g). However, it is worth nothing that the RL min of S-1-Si 3 N 4 is lower and the EAB can be achieved in a thinner thickness, which means more abundant attenuation effects in S-1-Si 3 N 4 .…”

Architecture inspired structure engineering toward carbon nanotube hybrid for microwave absorption promotion

“…The electromagnetic parameters of samples were studied to unravel the underlying interaction and synergy between AC and CNTs for their variant EM responses. Based on the Debye equations, the relative complex permittivity that reflects the electronic energy storage and attenuating capacities of materials can convey their dielectric behaviors ( Liang et al., 2022 ). As shown in Figure 4 A, pristine CNTs exhibited a typical frequency dispersion behavior with a linearly steep decreasing real permittivity ( ε r ') from 70.33 to 20.70 upon the ascending frequency, which is caused by the aggravated lag of dielectric polarization as frequency increases; while pristine AC exhibited a much gentler decrease of ε r ' within a range of 12.08–10.54.…”