In this study, the electromagnetic wave absorption properties of woven glass fiber reinforced epoxy composites with Sb2O3 and SnO2 nanoparticles doped mica pigments were investigated. Herein, we synthesized SnO2/mica, Sb2O3/mica, and Sb2O3:SnO2/mica pigments using the sol–gel method. Subsequently, mica pigments filled glass fiber/epoxy composite panels were fabricated with a vacuum assisted resin mold. The phase, crystal, and morphological examinations of particles confirm the deposition of SnO2 and Sb2O3 nanoparticles on the mica surfaces. The electromagnetic wave absorption properties of samples were measured using the S parameters and obtained dielectric data. Sb2O3:SnO2/mica particles display higher complex permittivity and dielectric loss values due to the strong interfacial polarization between conductive nano metal‐oxide shells and mica surfaces. According to the calculated reflection loss values, Sb2O3:SnO2/mica particles exhibit superior electromagnetic wave absorption performance with a minimum reflection loss of −25.62 dB for 2.4 mm thicknesses with effective bandwidth between 9.3 and 12.4 GHz. The S parameters of the prepared structural composites with the size of 30 cm × 30 cm × 3 mm was determined by the free‐space technique using the transmission line technique. According to the S12 parameters, filled glass fiber/epoxy composite containing 25 wt% Sb2O3:SnO2/mica show a minimum reflection loss of −20.426 dB at 8.2 GHz with effective bandwidth between 8.2 and 9.67 GHz. These results indicate that Sb2O3:SnO2/mica‐filled fiber/epoxy composite is an excellent candidate for the practical application of electromagnetic wave absorbers.
Abstract-This paper examines the electromagnetic shielding characteristics of milano, cardigan and lacoste with respect to weft and rib type composite knitted fabrics. All of these fabrics, made of hybrid yarns containing 50 µm diameter metal fibres such as copper, silver and stainless steel, were produced for electromagnetic shielding purposes. The shielding effectiveness (SE) of the fabrics was measured by reading S parameters from the signal when the sample was placed in the path of signal at the frequency range 1.7 to 2.6 GHz inside the WR430 waveguide system. After which S parameters was converted to SE values. The variation in electromagnetic shielding effectiveness (EMSE) with the factors, such as radiant frequency, metal type, wales density and geometry, were discussed. Experimental results show that all factors, especially the geometry of the fabric, have significant effect on SE. The best EMSE values were obtained by milano type knitted fabrics which was above 20 dB. It was found that milano, cardigan and lacoste composite fabrics, uncommon in EMSE experiments found in literature, give better shielding performances than rib and weft composite fabrics, under the same conditions.
In this study, the microwave absorption properties of single‐ and double‐layer composites were investigated for experimental and numerical solution in the 8.2 to 12.4 GHz for different thickness (t m) of composites. Herein, the single‐layer composites (R1: CuO and R2: CuO‐containing graphene nanoparticle [GNP]) and double‐layer composites that composed of R1 and R2 layers were fabricated. The first double‐layer composite labeled as D1 contains R1 as a matching layer and R2 as an absorbing layer and the second double‐layer composite labeled as D2 contains R2 as a matching layer and R1 as an absorbing layer. D1 and D2 produced composites were also designed numerically and denoted as M1 and M2, respectively. The measured and simulated reflection loss (R L) of double‐layer composites shows similar performance, and it was observed that the microwave absorbers obtained with experimental studies can be modeled using computer design. The M2 double‐layer design based on 5 mm of the matching layer and 2 mm of the absorbing layer shows a minimum R L value of −33.7 dB at 10.06 GHz and an absorption bandwidth of about 1.13 GHz below −10 dB compared to single‐layer composites.
Debye model is used for approximating the frequency dependent complex effective permittivity of the composite structures in filter and shielding applications at microwave frequencies. In Debye model, desired shielding effectiveness (SE) is obtained by determining the Debye parameters using trial and error method. But this may result in wasting time or not converging to an optimum solution. In this work to overcome this problem Debye parameters were optimized by using Differential Evolution (DE) algorithm. A Maxwell Garnett (MG) mixing rule was applied to these optimized parameters to obtain frequency selective surface (FSS) parameters. 12dB shielding threshold was chosen between 0.05 -5GHz frequency range. In accordance with the obtained parameters of FSS, a structure was designed in CST simulation software and simulations had been conducted to obtain SE results. It was seen that the results obtained from analytical computations agree with those obtained from simulations.
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