Enhanced Microwave Absorption Bandwidth in Graphene-Encapsulated Iron Nanoparticles with Core–Shell Structure

Abstract

Graphene-encapsulated iron nanoparticles (Fe(G)) hold great promise as microwave absorbers owing to the combined dielectric loss of the graphene shell and the magnetic loss of the ferromagnetic metal core. Transmission electron microscopy (TEM) revealed transition metal nanoparticles encapsulated by graphene layers. The microwave electromagnetic parameters and reflection loss (R) of the Fe(G) were investigated. Graphene provided Fe(G) with a distinctive dielectric behavior via interfacial polarizations taking place at the interface between the iron cores and the graphene shells. The R of Fe(G)/paraffin composites with different Fe(G) contents and coating thickness was simulated according to the transmit-line theory and the measured complex permittivity and permeability. The Fe(G)/paraffin composites showed an excellent microwave absorption with a minimum calculated R of −58 dB at 11 GHz and a 60 wt% Fe(G) loading. The composites showed a wide bandwidth (the bandwidth of less than −10 dB was about 11 GHz). The R of composites with 1–3 mm coating thickness was measured using the Arch method. The absorption position was in line with the calculated results, suggesting that the graphene-coated iron nanoparticles can generate a suitable electromagnetic match and provide an intense microwave absorption. Excellent Fe(G) microwave absorbers can be obtained by selecting optimum layer numbers and Fe(G) loadings in the composites.

Binary vanadium pentoxide carbon-graphene foam composites derived from dark red hibiscus sabdariffa for advanced asymmetric supercapacitor

“…In the same range, figure 2a Raman frequency (cm −1 ) vibration assignment references 99 A g [68,72] . same D and G bands in the binary V 2 O 5 @C-R 2 HS/GF composites which were observed at 1335-1350 cm −1 and 1577.2-1581 cm −1 , respectively [76]. The D and G peaks in the Raman spectrum of the binary V 2 O 5 @C-R 2 HS/GF composites are narrower and more pronounced than that of the V 2 O 5 @C-R 2 HS due to the additional contribution of the GF in the materials.…”

“…The D peak is linked to the disorder or defect in the graphitic structure while the G peak is ascribed to the tangential vibration of the sp 2 carbon atoms [75]. In the same range, figure 2a Raman shift (cm −1 ) [76]. The D and G peaks in the Raman spectrum of the binary V 2 O 5 @C-R 2 HS/GF composites are narrower and more pronounced than that of the V 2 O 5 @C-R 2 HS due to the additional contribution of the GF in the materials.…”

Design and Synthesis Strategies: 2D Materials for Electromagnetic Shielding/Absorbing

“…These structures are conducive to extending the propagation path of EM waves, enhancing multiple reflection loss (RL) and interfacial polarization, providing more polarization centers and reducing complex permittivity in order to balance the impedance matching. The typical microstructure of EMI shielding and absorbing materials includes segregated structure, [36] “brick and mortar” structure, [37] core‐shell structure, [38] and porous aerogel [39] . The preparation strategies and EM properties will be expatiated as follows.…”

Rational design of two-dimensional flaky Fe/void/C composites for enhanced microwave absorption properties

“…22,23 For example, Che et al have filled Fe into carbon nanotubes by catalytic pyrolysis; 24 Li et al have synthesized rose-like carbon-wrapped iron (Fe@C) with a porous structure; 25 and Zhang et al have reported graphene-encapsulated iron nanoparticles by arc discharge. 26…”