Abstract
H2 plasma treatment was performed on carbon-based nonwoven fabrics (c-NFs) in a 900 W microwave plasma-enhanced chemical vapor deposition system at 750 °C and 40 Torr. Consequently, the electromagnetic wave shielding effectiveness (SE) of the c-NFs was significantly enhanced across the operating frequency range of 0.04 to 20.0 GHz. We compared the electromagnetic wave SE of the H2 plasma-treated c-NFs samples with that of native c-NFs samples coated with nano-sized Ag particles. Despite having a lower surface electrical conductivity, H2 plasma-treated c-NFs samples exhibited a considerably higher electromagnetic wave SE than the Ag-coated c-NFs samples, across the relatively high operating frequency range of 7.0 to 20.0 GHz. The carbon component of H2 plasma-treated c-NFs samples increased significantly compared with the oxygen component. The H2 plasma treatment transformed the alcohol-type (C–O–H) compounds formed by carbon-oxygen bonds on the surface of the native c-NFs samples into ether-type (C–O–C) compounds. On the basis of these results, we proposed a mechanism to explain the electromagnetic wave SE enhancement observed in H2 plasma-treated c-NFs.
Highlights
Electromagnetic waves are composed of oscillating electric and magnetic fields
The shielding effectiveness (SE) of electromagnetic wave shielding materials is given in units of dB and can be estimated using the following empirical equation, which was proposed by Simon [8]: SE = 50 + 10log(ρf )−1 + 1.7t(f /ρ)1/2, where ρ is resistivity, t is the thickness of the shielding material, and f is the operating frequency
At high operating frequencies required by technologies such as fifth-generation wireless networks, the absorption loss characteristics of shielding materials are especially important for effectively protecting electromagnetic waves
Summary
Electromagnetic waves are composed of oscillating electric and magnetic fields. materials with electromagnetic wave shielding capabilities are expected to interact with either one or both of these fields. The shielding effectiveness (SE) of electromagnetic wave shielding materials is given in units of dB and can be estimated using the following empirical equation, which was proposed by Simon [8]: SE = 50 + 10log(ρf )−1 + 1.7t(f /ρ)1/2, where ρ is resistivity, t is the thickness of the shielding material, and f is the operating frequency. In this equation, reflection loss, that is, 10log(ρf )−1, decreases with increasing operating frequency. At high operating frequencies required by technologies such as fifth-generation wireless networks, the absorption loss characteristics of shielding materials are especially important for effectively protecting electromagnetic waves
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