4 years ago

Unique Multilayered Assembly Consisting of “Flower-Like” Ferrite Nanoclusters Conjugated with MWCNT as Millimeter Wave Absorbers

Unique Multilayered Assembly Consisting of “Flower-Like” Ferrite Nanoclusters Conjugated with MWCNT as Millimeter Wave Absorbers
Sourav Biswas, Suryasarathi Bose, Sujit S. Panja
Unique multilayered assembly was designed here using polymeric blends containing “flower-like” ferrite nanoparticles conjugated with multiwall carbon nanotubes (MWCNTs) for attenuating 99.999% of the incoming electromagnetic (EM) radiation. In comparison to a traditional single layered structure, this unique assembly is superior for myriad applications related to suppressing the incoming EM radiation, mostly by absorption. The three key requirements—impedance wave matching, absorption, and multiple scattering from the heterogeneous structures—were accounted here by suitably modifying the nanomaterials. A bicomponent blend consisting of two immiscible polymers, polyvinylidine fluoride (PVDF) and polycarbonate (PC), was used here to construct the multilayered assembly wherein selective localization of nanoparticles in one of the components, driven by thermodynamics, reduced the percolation threshold of the nanoparticles. In order to improve the impedance matching, MWCNTs were functionalized using the defect sites induced by harsh chemical treatment and incorporated in PC/PVDF blends as the inner layer of the multilayered assembly. The conjugation of flower-like Fe3O4 nanoclusters on the defect sites of the surface functionalized MWCNTs absorbs the incident EM waves due to the interfacial polarization of different heterogeneous structures. The value of total loss tangent, attenuation constant, and absorption coefficient supports absorption driven shielding in PC/PVDF blends. The efficient thermal dissipation together with high absorption led to fix this as the intermediate layer of the assembly. Finally, multiple scattering through the network of pristine MWCNTs was utilized as the outermost layer of the assembly, which guided the penetrated waves to interact with this layer resulting in maximum attenuation. This unique three-layered assembly, which exhibited a shielding effectiveness of −64 dB at 18 GHz for 0.9 mm thickness, powered by multifunctionality, offer amendable replacement of the existing solution related to EM absorption.

Publisher URL: http://dx.doi.org/10.1021/acs.jpcc.7b02668

DOI: 10.1021/acs.jpcc.7b02668

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