The electromagnetic (EM) properties of polyurethane template-based reticulated carbon foams were investigated in the 26-37 GHz microwave frequency range (Ka-band). It was experimentally proved that carbon foams of a thickness of 2 mm and a density of 22-55 mg cm −3 are almost not transparent to microwave radiation, and this is especially true for the densest ones. Depending on bulk density, the EM response of carbon foams in the microwave region can be mainly accounted for by either reflection or absorption. EM shielding efficiency of more dilute samples is due to absorption mechanisms, whereas denser foams provide up to 80% reflection of EM signals. EM properties of carbon foams in the Ka-band can be accurately predicted by a very simple model based on Fresnel formulae developed in this communication.
How to cite this paper: Zhuravlev, V.A., Suslyaev, V.I., Korovin, E.Yu. and Dorozhkin, K.V. (2014)
AbstractResults of measurements of permeability, permittivity and radar absorption properties of composites on basis of carbonyl iron particles R-10 brand are presented in this paper. The calculations and experimental studies have shown that in the super high frequency (SHF) and extremely high frequency (EHF) ranges on the basis of two-layer structures with different content of carbonyl iron particles can create a radar absorbing coatings with a reflectivity of less than −10 dB over a wide bandwidth from 3.1 to 17.1 GHz and from 27 to 37 GHz. Absorbing properties of composites are saved in terahertz frequency range from 250 to 525 GHz.
Coagulation technique was applied for preparation of multiwall carbon nanotube- (MWNT-)containing polystyrene (PSt) composite materials with different MWNT loading (0.5–10 wt.%). Scanning and transmission electron microscopies were used for investigation of the morphology and structure of produced composites. It was shown that synthesis of MWNT/PSt composites using coagulation technique allows one to obtain high dispersion degree of MWNT in the polymer matrix. According to microscopy data, composite powder consists of the polystyrene matrix forming spherical particles with diameter ca. 100–200 nm, and the surface of MWNT is strongly wetted by the polymer forming thin layer with 5–10 nm thickness. Electrical conductivity of MWNT/PSt composites was investigated using a four-probe technique. Observed electrical percolation threshold of composite materials is near to 10 wt.%, mainly due to the insulating polymer layer deposited on the surface of nanotubes. Electromagnetic response of prepared materials was investigated in broadband region (0.01–4 and 26–36 GHz). It was found that MWNT/PSt composites are almost radiotransparent for low frequency region and possess high absorbance of EM radiation at higher frequencies.
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