Selective broadband electromagnetic wave absorption performance
Electromagnetic wave absorbents have been researched and developed to combat the escalating concern of electromagnetic pollution. Specifically, magnetic ferrites have been identified as promising candidate for synthesis of high-performance electromagnet absorbers owing to its excellent conductivity, magnetic moment, permittivity and high curie temperature properties favorable for both magnetic and dielectric loss. Despite their excellent absorption properties, several drawbacks, including high density and poor impedance matching, hinder their practical applications. As such, magnetic ferrite nanoparticles have been combined with other appropriate dielectric materials to address the challenges. However, this requires accurate tailoring of the heterostructures to meet the demands of broad bandwidth, including the low-frequency band.
In a recent paper published in the research journal, Composites Part A: Applied Science and Manufacturing, scientists at the School of Physical Science and Technology from the Northwestern Polytechnical University in China: Jiaolong Liu (PhD candidate), Dr. Hongsheng Liang, and led by Professor Hongjing Wu developed a facile hydrothermal method to fabricate binary Fe3O4/MoS2 composites for use in selective broadband electromagnetic wave absorption. To obtain the different morphologies of 3D MoS2 nanoflowers decorated with monodispersed Fe3O4 particles, the molar ratio of Fe3O4 was tailored to MoS2.
Four samples out of which three were obtained by changing the addition of Fe3O4 denoted as S2, S3 and S4 as well as a sample without MoS2 denoted as S1 was considered. Results showed enhanced electromagnetic wave absorption ability for binary Fe3O4/MoS2 composites as compared to pristine Fe3O4 nanoparticles. This was mainly attributed to the excellent impedance matching and good dielectric/magnetic loss properties. Critical electromagnetic wave absorption properties such as the reflection loss were evaluated for all the samples. Sample 3 (S3) exhibited the best electromagnetic wave absorption performance. A strong minimum reflection loss of -64dB was attained at an ultra-thin thickness of 1.7 mm, while an effective absorption bandwidth of 6.1GHz was also attained at an ultra-thin thickness of 2.0mm. Furthermore, a 100% frequency occupy ratio could be obtained even for low-frequency bands without severe deterioration of the reflection loss intensity. In view of the results, S3 portrayed robust absorption characteristics than other MoS2 based absorbers.
It was worth noting that the dielectric loss, consisting of conduction and relaxation losses, is largely associated with the imaginary permittivity. All the samples exhibited irregular semicircles with grater radii and numbers being observed in S2-S4. This resulted in the enhancement of the multiple interfacial polarization and dipolar polarization observed in the hybridized MoS2. Consequently, the hierarchical nanoflower-like structure ample the interfaces to bring about strong interfacial polarization. Despite S2 appearing to possess the best electromagnetic wave absorption ability due to its high attenuation and dielectric loss, it was overtaken by S3, followed by S4, which are extremely good in terms of absorption intensity.
Overall, the research team successfully synthesized hierarchical flowerlike Fe3O4/MoS2 composites. Fe3O4 content was tuned to obtain different morphologies of Fe3O4/MoS2 from which sample 3 exhibited the best electromagnetic wave absorption ability. Altogether, the study provides useful insights in the facile synthesize of brilliant electromagnetic wave absorbers and Fe3O4 composites, in particular, are promising electromagnetic wave absorbers with selective broadband absorption performance.
Liu, J., Liang, H., & Wu, H. (2020). Hierarchical flower-like Fe3O4/MoS2 composites for selective broadband electromagnetic wave absorption performance. Composites Part A: Applied Science and Manufacturing, 130, 105760.