Minimum Shielding Effectiveness Research Articles

Structural and shielding effectiveness properties of (NiFe2O4/chopped strands) composites for 6.5–18 GHz applications

In this research, a mixed oxide technique was employed to create composite materials comprising NiFe2O4-chopped strands, aimed at evaluating their structural properties and microwave shielding effectiveness. The composites, produced through a hot-pressing process with varying proportions of NiFe2O4 and chopped strands, were integrated with epoxy to enhance their shielding capabilities. X-ray diffraction confirmed the formation of single-phase NiFe2O4, free from secondary phases. Scanning electron microscopy analysis corroborated the presence of cubic crystalline NiFe2O4, without microstructural impurities. The microwave shielding performance of the composites was assessed within the 6.5–18 GHz frequency range using a network analyzer (NA), revealing a minimum shielding effectiveness of − 36.34 dB at 16.56 GHz for a 1.3 mm thick sample. These findings demonstrate the successful fabrication of NiFe2O4-chopped strands composites with tunable microwave shielding properties, achieved by adjusting the NiFe2O4 content, allowing for tailored performance across various frequency bands.

Prediction of the Electromagnetic Shielding Effectiveness of Metal Grid Using Neural Network Algorithm

With the advantages of simple structure, high electromagnetic (EM) shielding effectiveness (SE), wide shielding bandwidth and adjustable transmittance, the metal grid is a popular tool in the field of electromagnetic shielding. In this work, the deep learning algorithm of artificial neural network was used to predict the EM SE of the metal grid. After certain number of trainings, both the SE spectrum and the minimum SE value in a given frequency band can be predicted accurately and effectively. On the other hand, for a target SE, the design parameters of the metal grid structure can be immediately predicted. The results show that the relative mean square deviation of the predicted SE curve is about 5%, the relative error of the minimum SE value of the curve is less than 5%, and the average relative error of the minimum SE value in the predicted frequency band is 11.5%.

Analytic Magnetic Shielding Effectiveness of Multiple Long Slots on a Metal Plate Using Rectangular Loops

This article proposes an analytical formulation to calculate the magnetic near-field shielding effectiveness (SE) of a metal plate with multiple long slots in the low frequency range below 10 MHz. Mutual inductances of two rectangular loop antennas in the presence and absence of the metal plate with slots are analytically derived. Then, the magnetic SE is obtained by the ratio of two analytic mutual inductances. In addition, an analytical SE formulation based on the transmission line model is used to consider the diffusion effect caused by a low conductivity of the metal plate. The total magnetic SE is finally determined by choosing the minimum SE between two analytic results due to the slot and diffusion effects. For validation, the results obtained by the proposed method are compared with the numerical results of full-wave simulation, and good agreement is achieved.

Modeling and Measuring the Shielding Effectiveness of Carbon Fiber Composites

We provide a model able to predict the shielding effectiveness (SE) of carbon fiber composite (CFC) panels made of stacked layers of conducting fibers. This model permits us to obtain simple formulas in which the only parameters needed are the sheet square resistance and the effective panel thickness. These tools let us predict a minimum SE, which always increases with the frequency and therefore constituting the worst case, from an electromagnetic shielding perspective. Consequently, the measurement of minimum SE requirements can be simply measured with a micro-ohmmeter using an specific experimental setup which is also described here. Additionally, this method allows to measure very high SE falling far beyond the dynamic range of the values measurable with the most commonly used standard, the ASTM D4935. After describing the modeling technique and the different test setups used, across-validation between theoretical and experimental results is made for four different samples of CFC; two designed to test the modeling assumptions and two which are representative of the ones nowadays used in a real aircraft.

Electromagnetic Shielding Effectiveness of Nickel Fiber-Reinforced Cement Composites

The nickel fiber was added into the cement-based composite materials as a shielding medium. Influences of the three different types and amount of dispersants and weight fraction of nickel fiber on the electrical conductivity and electromagnetic shielding effectiveness of the cement matrix composite were discussed. The conductivity of cement based composite materials and the uniformity distribution of shielding medium were characterized by four-point probe meter and scanning electron microscopy, respectively. Electromagnetic interference shielding effectiveness in the frequency range of 1 MHz to 1500 MHz was characterized by coaxial cable method. The results indicated that the improved dispersion of nickel by incorporation of dispersants might yield the enhancement of the electrical properties of nickel fiber-reinforced cement composites. When the dosage of methyl cellulose reaches 0.4 wt.%, the pre-dispersing nickel fiber enhances the electrical conductivity of the cement-based composite materials significantly. With the increase of fiber volume fraction, the shielding effectiveness and trend of frequency change of the corresponding fiber-reinforced concrete were enhanced. When the content of nickel fiber powder was 9.0 vol.%, the conductivity was 2.65×10-3 s·cm-1, and the average shielding effectiveness of the specimen in 1MHz-1500 MHz was about 21.78 dB, with the maximum shielding effectiveness of 24.48 dB and the minimum shielding effectiveness 19.85 dB.

The influence of gradient and sandwich configurations on the electromagnetic interference shielding performance of multilayered thermoplastic polyurethane/graphene composite foams

Multilayered thermoplastic polyurethane/graphene (PUG) composites were fabricated by stacking single-layered PUG foams together. The arrangement of single-layered PUG foams in different orders could realize the gradient concentration of graphene, which was proved to be a facile approach to enhance the microwave-absorbing (MA) property of PUG composites, rather than their electromagnetic interference (EMI) shielding effectiveness (SE). Further sandwiching a wave-transmitting layer between two pieces of PUG foams formed a sandwich structure, by which the SE of the two samples could be significantly improved and the resultant composites still possessed strong MA performance. The SE increment was assigned to the enhanced reflection loss induced by constructive interference, and largely dependent on the thickness of the interlayer d. Particularly, when the values of the d were zero and the quarter of the largest wavelength in the testing frequency range, the minimum and maximum SE could be obtained, respectively. These results are critical to the fabrication of high-performance polymer-based shielding materials with strong MA property.

Process and Analysis of Electromagnetic Shielding in Composite Fiberboard Laminated with Electroless Nickel-plated Carbon Fiber

To develop a composite fiberboard with high electromagnetic shielding effectiveness (SE) and an easily industrialized process, electroless nickel-plated carbon fiber technology was used to improve the conductivity and electromagnetic properties of carbon fiber and carbon fiber sheets. The SE of composite fiberboards laminated with nickel-plated carbon fiber with different arrangements was also studied. The results showed that the best plating scheme in this study was a NiSO4 concentration of 35 g/L, plating temperature of 70 °C, pH of 9, and plating time of 15 min. When nickel-plated carbon fiber in a grid arrangement was added to the core between two fiberboards, the minimum and maximum SE of 19 × 19 grid arrangement was 41.54 dB and 63.73 dB in the 200 to 1000 MHz frequency range, respectively, and reached medium grade. SE of composite fiberboard laminated with double layers of plated carbon fiber sheet ranged from 45.29 dB to 52.01 dB and reached medium grade. It is thus feasible to use two-layer nickel-plated carbon fiber with a 19 × 19 grid arrangement to make composite fiberboard with high SE, mechanical properties greater than the national standard, and an easily industrializable process.

Optimization design of electromagnetic shielding composites

The effective electromagnetic parameters physical model of composites and prediction formulas of composites' shielding effectiveness and reflectivity were derived based on micromechanics, variational principle and electromagnetic wave transmission theory. The multi-objective optimization design of multilayer composites was carried out using genetic algorithm. The optimized results indicate that material parameter proportioning of biggest absorption ability can be acquired under the condition of the minimum shielding effectiveness can be satisfied in certain frequency band. The validity of optimization design model was verified and the scheme has certain theoretical value and directive significance to the design of high efficiency shielding composites.

The Research on Wood Fiber/Stainless Steel Net Electromagnetic Shielding Composite Board

In this paper, the electromagnetic shielding function composite fiberboards were made by filling with stainless steel nets dipped with urea-formaldehyde resin adhesive (UF) and the influence of different mesh and layers of nets on its electromagnetic shielding performance, static bending strength (MOR), modulus of elasticity (MOE) and internal bonding strength (IB) were studied. The results showed that: when the mechanical strength was enough and the frequency was in range of 50MHz to 1GHz, of all the composite fiberboards filled with one-layer stainless steel net, the one filled with 60 mesh was best and the minimum shielding effectiveness (SE) was 36.22 dB; when filled with two-layers nets, the one filled with 80 mesh was best and the minimum SE was 42.54dB; when filled with three-layers nets, the one filled with 60 mesh was best and the minimum SE was 50.77dB.

On the Shielding Effectiveness of Small-Dimension Enclosures Using a Reverberation Chamber

Research on the shielding effectiveness (SE) of small shielding enclosures has attracted more and more attention since small shielding enclosures are widely applied in many areas, such as aviation electronics, testing equipment, and industrial control. By using a reverberation chamber, a multipoint field test procedure is applied to measure SE for small-dimension enclosures. The SE of a small enclosure is simulated and measured by moving a field probe along particular positions inside the enclosure. For specifying the possible maximum field that the internal electronics may be exposed to, the minimum SE is suggested to characterize the SE of shielding enclosures together with average SE. The experimental results of SE by using an automatic testing system proved that the definition of SE and the test method are highly effective and excellent repeatability has been achieved. Hence, the proposed testing method is useful for SE testing of small-dimension enclosures.

Fabrication and characterization of organic semiconductor for electromagnetic interference shielding material

Abstract Conducting polymer films produced by electropolymerization technique are highly conductive, simple, and suitable for use especially in electronic devices. An attempt has been made to produce polypyrrole-poly(vinyl alcohol) (PPy-PVA) conducting polymer composite films using 0.1 m p-toluene sulfonate dopant at a potential of 1.2 V (vs. standard calomel electrode) on indium tin oxide glass electrode. The potential application of the prepared PPy-PVA conducting polymer composite films as an electromagnetic interference (EMI) shielding material has been investigated in the present study. The EMI shielding effectiveness of PPy-PVA composite films prepared from different experimental conditions was analyzed in the microwave frequency range of 8–12 GHz. The shielding effectiveness of 45.67–35.7 dB has been demonstrated by PPy-PVA conducting polymer composite films, which appears to be very attractive in any EMI shielding applications where a minimum shielding effectiveness of 35 dB is required.

Electromagnetic Shielding Effectiveness of Cement-Matrix Composite Containing Nickel Fiber

The cement-matrix composite with the function of building structure and electromagnetic interference shielding was prepared by filling nickel fiber into cement. The dispersion of nickel fiber in cement-matrix composite and the shielding effectiveness of composite containing various volume fractions of nickel fiber were investgated in this paper. The electromagnetic interference shielding effectiveness in the frequency range of 0.1 MHz to 1.5 GHz and the conductivity of composite were measured by coaxial cable method and two-probe method, respectively. The dispersion of nickel fiber in cement was characterized by EPMA. The results indicated that the dispersion property of nickel fiber by sodium hexametaphosphatecan was better than sodium carboxymethylcellulose. The optimum contents of nickel fiber in composite was 5 vol.%, the maximum shielding effectiveness was 45.7 dB in 140 MHz and the minimum shielding effectiveness was 36 dB in 1240 MHz. The shielding effectiveness of composite with 7 vol.% nickel fiber was lower than that with 5 vol.% nickel fiber due to the tendency of nickel fiber cling to each other.

A novel structure of woven continuous-carbon fiber composites with high electromagnetic shielding

A novel structure employing the woven continuous-carbon fiber (CCF) epoxy composite with high electromagnetic (EM) shielding is presented experimentally and theoretically. The influences of weave type, number, and angle of overlapped plates upon the shielding effectiveness (SE) of the woven CCF-epoxy composite are investigated. The minimum SE of the single, double, and triple-plain or balanced-twill woven CCF-composite plates was measured to be as high as 50 dB, 60 dB, and 70 dB, respectively. More than 100 dB in SE was obtained for the triple-overlapped, plain-weave CCF composite at a frequency of 0.9 GHz. The weight percentage of the single CCF-composite plate required for electronic application is 4.8% only, which is less than one quarter of the CF content, and the performance in SE is 10 dB higher in comparison with long, CF-filled, liquid-crystal polymer (LCP) composites. The SE calculated theoretically is consistent with that measured by the experiment.