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.
Highlights
With the rapid development of electronic and wireless technologies, electromagnetic interference (EMI) and pollution are becoming serious issues worldwide, affecting more and more electronic integrated devices and the living environment [1,2]
The Fe(G) nanoparticles showed a spherical morphology and a core–shell structure, with the inner iron core being completely encapsulated by the outer graphene shells
Fe(G) nanoparticles with a core of magnetic iron nanoparticles and a shell of dielectric graphene were prepared by an arc discharge method
Summary
With the rapid development of electronic and wireless technologies, electromagnetic interference (EMI) and pollution are becoming serious issues worldwide, affecting more and more electronic integrated devices and the living environment [1,2]. Carbon-encapsulated metal nanoparticle structure composite materials present numerous advantages, including wide electromagnetic absorption bandwidth, low density, and stable physical and chemical properties [24]. This outer nanocarbon shell prevents the inner nanometallic particles from oxidation and agglomeration, and the core–shell structure is conducive to the impedance matching of the enclosed space. The preparation of thin materials combining high-efficiency microwave absorption and a wide effective bandwidth remains highly challenging, and the electromagnetic loss mechanism of core–shell structured nanoparticles requires further studies In terms of this view, graphene is a new nanocarbon material that can be used for this purpose. Experimental R measurements were conducted over Fe(G)/epoxy coatings and the results were compared with the calculated R values
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