Evolution of double magnetic resonance behavior and electromagnetic properties of flake carbonyl iron and multi-walled carbon nanotubes filled epoxy-silicone

Graphene nanosheet- and flake carbonyl iron particle-filled epoxy–silicone composites as thin–thickness and wide-bandwidth microwave absorber

“…It is reasonable that higher values of l 0 and l 00 can be obtained when the composite is filled with higher FCI content. Furthermore, two interesting phenomena can be obtained in the complex permeability spectra of the composites, which have also been investigated in the composites containing MWCNTs and FCI particles in our previous works [41,42]. The first phenomena is the slight increase in complex permeability with increase in GN content with the same FCI particle content.…”

“…Therefore, the slight increase in the complex permeability is believed to be due to the interactions between the GNs and FCI particles in the epoxy-silicone resin matrix, as the GN content increased with the same FCI particle content. It is well accepted that there are two mechanisms responsible for the permeability dispersion of GNs and FCI particles: the natural resonance at lower frequencies and the exchange resonance at higher frequencies [41]. The natural resonance frequency obtained in the GHz range was attributed to the incorporation of magnetocrystalline anisotropy and shape anisotropy of FCI magnetic particles.…”

“…Compared with the SCI particles, flake carbonyl iron (FCI) particles have attracted more interest in MAM application due to their high permeability and matched permittivity, which are mainly attributed to low eddy current loss arising the effects of particle shape and size [8]. In our previous reports, absorbers with simple fabrication techniques and uniform dispersion of multiwalled carbon nanotubes (MWCNTs) and FCI particles have been exploited as efficient EM absorbers [41,42]. On the other hand, compared with GP and RGO, GNs proved to be more appealing as the alternative carbon nanomaterials for design MAMs, as they are a cost-effective option and more easily processable for composite preparation, and exhibit a higher real part of the complex permittivity [43][44][45].…”

DESIGN OF ABSORPTIVE COATINGS FOR ARBITRARILY SHAPED TARGETS FOR REDUCTION OF RADAR CROSS SECTION (RCS) USING AN ALTERNATIVE TO THE TRANSFORMATION OPTICS (TO) ALGORITHM (Invited Paper)

“…Figure 20 shows the example of a five-layer absorber designed for a planar surface using the optimization techniques discussed previously. Wideband absorption performance is achieved from 2 to 16.9 GHz with a total thickness of 4.26 mm (as opposed to a frequency range of 4.6 to 18 GHz and a total thickness of 3 mm) [39]. The increased number of layers provides increased degrees of freedom, which could potentially achieve the required level of performance without having to resort to synthesis of new material.…”

Synthesis and microwave absorbing characteristics of functionally graded carbonyl iron/polyurethane composites

“…Carbonyl iron (CI) particles possessing relatively low permittivity, high Curie temperature, and high specific saturation magnetization intensity, 4πM S and high resistivity can be embedded in an insulating polymer matrix to become an effective magnetic absorber for the higher frequency ranging from 2 to 18 GHz. [1][2][3][4][5] However, a single layer of magnetic absorber possesses narrow bandwidth and the bandwidth cannot be widened through the increase of thickness nor the weight percentage of the magnetic fillers. Functionally graded materials (FGMs) are a new class of two-component composite materials in which the composition or the microstructure is varied in one specific direction.…”