Defect engineering could provide new ideas for the design of transition metal disulfide electromagnetic wave (EMW) absorbers with high performance. Since the effects of dipoles on impedance matching and EMW absorption are crucial for the development of novel absorbers, the polarization attenuation dependence on defect engineering should be understood at micro- and macro-scales. In this paper, it is found that the defect-rich WS 2 nanoflowers synthesized by the cold plasma method possess excellent EMW absorption properties. Cold plasma treatment of materials is easy to perform and maintains the original shape of the material to a high degree. The formation of defects results in abundant electrochemically active sites, increased multiple reflection losses, improved dielectric properties and impedance matching in the materials. The RL min of the defect-rich material with a thickness of 3.19 mm is as high as −54.36 dB at 8.16 GHz, and the effective absorption bandwidth is 4.72 GHz. The results reveal that the formation of defective vacancies enhances the effects of dipole polarization of the material on improving its EMW absorption properties. Thus, this work provides not only a facile preparation route for novel EMW-absorbing materials, but also a new strategy for tunning defects in transition metal disulfides.
Using air/SiO 2 @Fe/C yolk-shell nanospheres (NSs) absorbers as a carrier, this research studies the coupling relationship between low-frequency electromagnetic wave (EMW) absorption performance and construction of materials with dual-sized pores and dual-component. Endured via synergistic process of pyrolysis and etching, the sizes of large cavities (∼ 200 nm) and mesopores (∼ 10 nm) were finely tuned at near-atomic scales. In addition, plenty of polarization attenuation structures (e.g., cavities/carbon, cavities/silica, iron/carbon and defects) were also generated. Results revealed that construction of multi-scale pores has slender contribution on the peak reflection loss (RL min ) values, while EMW absorption in the low-frequency range was obviously enhanced. The resulted H12 sample presented a resonance reductions at 6.72 GHz with the RL min value of −22.4 dB, which shifted ∼9.8 GHz towards lower frequencies compared to H0 (-20 dB, 16.52 GHz). This case can be elucidated via the resonance mechanism of cavity, where the air/SiO 2 @Fe/C yolk-shell NSs function as dielectric resonators. This work offers a novel way to design the micro/nano-scale pores in carbon-based EMW-absorbing materials, and a promising approach to develop materials designed for low-frequency EMW absorption.
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