Microwave attenuation of multiwalled carbon nanotube-fused silica composites

Abstract

Multiwalled carbon nanotubes (MWCNTs) were used to convert radome materials to microwave absorbing materials. Dense MWCNT-fused silica composites were prepared by hot-pressing technique. The composites exhibit high complex permittivities at X-band frequencies, depending on the content of MWCNTs. The value of the loss tangent increases three orders over pure fused silica only by incorporating 2.5vol% MWCNTs into the composites. The average magnitude of microwave transmission reaches −33dB at 11–12GHz in the 10vol% MWCNT-fused silica composites, which indicates the composites have excellent microwave attenuation properties. The attenuation properties mainly originate from the electric loss of MWCNTs by the motion of conducting electrons.

Electrical properties and applications of carbon nanotube composites

“…This is clearly shown in Figure 1(b). In Figure 1(a) and (b), the values of ε r ' and σ reported for the CNT composites [3][4][5][6][7][8][9] are plotted, although they were not measured at 5.8 or 60 GHz. The reported CNT composites seemed to be unsuitable for the single-layer absorbers with sufficient absorption coefficients at both frequencies.…”

“…In the design of commonly used multilayer EM absorbers with metal backplanes, the thickness, permittivity, and/or conductivity of each layer must be adjusted to achieve high absorbance at a target frequency [2]. CNT composites are effective to achieve wide ranges of permittivity and conductivity [3][4][5][6][7][8][9] and to widen design flexibility of EM absorbers. A high conductivity of more than 10 3 S/m has been reported for both singlewalled (SW) [10] and multi-walled (MW) [11] CNT composites, while a large real permittivity of 200 at 18 GHz has been observed for MWCNT/cellulose composite paper [12].…”

Electromagnetic interference shielding effectiveness of composite carbon nanotube macro-film at a high frequency range of 40 GHz to 60 GHz

“…Therefore, a growing number of alternative lightweight materials with high EMI SE at high frequencies have been developed to replace or supplement typical metals used in EMI shielding. [7][8][9][10] In recent years, electrically conductive ceramic materials or their composites, such as Ti 3 SiC 2 or Ti 3 SiC 2 /Al 2 O 3 composites, 11 and others 12 have been examined for use in EMI shielding, and a high EMI SE of 35 dB to 54 dB in the frequency range of 8.2 GHz to 18 GHz can be obtained. In particular, carbon materials, such as carbon black, 13 graphite flakes, 14 carbon fiber, 15 and carbon nanotubes (CNTs) 16 have been explored as possible lightweight electromagnetic shielding and absorbing materials.…”

Correlation between Electrical Conductivity and Microwave Shielding Effectiveness of Natural Rubber Based Composites, Containing Different Hybrid Fillers Obtained by Impregnation Technology

“…For example, Mishra et al [10] found that the phenolic resin sheet consisting of multiphase such as EG, γ-Fe 2 O 3 , silica and carbon fiber exhibits enhanced shielding effectiveness (from 18.77 to 55.40 dB) in the frequency range of 8.2 -12.4 GHz (X-band). However, Xiang et al [12] used silica particles for fabricating MWCNT-fused silica composites for electromagnetic interference shielding.…”