High porosity scaffold composites of graphene and carbon nanotubes as microwave absorbing materials

Abstract

The design of microwave absorbing materials requires low reflection and high absorption of radiation simultaneously. Low reflection of electromagnetic waves can be achieved inducing porous faces which minimize the impedance mismatch. High absorption can be obtained by increasing the conductivity of the material. We report the preparation of highly porous scaffolds from a combination of graphene and carbon nanotubes. The bimodal porous structure was controlled making use of the surface properties of graphene oxide that are able to stabilize hexane droplets in aqueous dispersions of graphene oxide and carbon nanotubes. After hydrothermal and two step freeze-drying processes, macro-(220 microns) and mesoporous (10 microns) structures, due to hexane droplets and freeze drying, respectively, were obtained. DC conductivities of 8.2, 14.7, 33.2, and 60.7 S m 1 were obtained for graphene scaffolds containing 0, 10, 20 and 40% of carbon nanotubes respectively. An electromagnetic characterization was performed on scaffolds infiltrated with epoxy resin; using appropriate models, the electromagnetic properties of the conducting phase have been obtained. Scaffolds with a thickness of 9 mm were able to absorb up to 80% of the incident radiation keeping the reflection as low as 20%.

Facile approach for a robust graphene/silver nanowires aerogel with high-performance electromagnetic interference shielding

“…2a) was further tted into three subpeaks at $284.6, $286.5 eV, and $288. 33 Moreover, the two peaks in the Ag 3d XPS spectrum of hybrid aerogels at 368.1 eV and 374.1 eV ( Fig. 2b) corresponded to Ag 3d 5/2 and Ag 3d 3/2 , 2 respectively, conrming the effective combination of AgNWs and RGO.…”

“…28 | RSC Adv., 2019, 9, 27-33 This journal isFig. 4 EMI-shielding performances of RGO/AgNWs aerogel with different mass ratios in the frequency range from 8.2 to 12.4 GHz: (a) SE T , (b) SE A , (c) SE R ; (d) average EMI-SE values from (a), (b), (c).30 | RSC Adv., 2019,9,[27][28][29][30][31][32][33] This journal is…”

Electromagnetic Shielding Materials in GHz Range

“…%) exhibit a EMI SE of 14–35 dB in the frequency range 8–18 GHz . In another work, graphene and graphene/CNT hybrid foams with controlled porosity via a modified hydrothermal method (HT) have been successfully prepared . In this shielding material, the dielectric is substituted by graphene which acts as the CNT binder and as a surfactant controlling the pore size and stabilizing the scaffold's structure.…”

Electromagnetic Properties of Carbon Gels

“…It is commonly accepted that carbon foams are good candidates for electromagnetic shielding materials [9][10][11]. Various other porous carbon structures, as well as carbon-filled composites, are also often investigated for electromagnetic applications [12][13][14]. However, the electromagnetic properties of carbon gels are still relatively unknown.…”