Electromagnetic Shielding Characteristics Research Articles

Silver nanowire-infused carbon aerogel: A multifunctional nanocellulose-derived material for personal thermal management

Personal thermal management (PTM) textiles for outdoor activities have become increasingly important for addressing energy consumption and thermal comfortable. Cellulose nanofiber (CNF) aerogels have emerged as promising candidates for PTM due to the eco-friendliness, lightweight, and low thermal conductivity. However, the singular insulation capability may not be sufficient to accommodate the diverse and harsh outdoor conditions. Herein, we carbonized CNF-based aerogel to fabricate anisotropic carbon aerogels, and then incorporated silver nanowires (AgNWs) upon onside to fabricate the dual-function AgNWs/carbon aerogel. The resulting material inherits high porosity (99.3 %), high surface area (503.2 m2/g), low density (7.08 mg/cm3), and low thermal conductivity (18.2 mW·m−1·k−1 in the axial direction) to act as an ideal thermal insulator. The AgNWs coating side demonstrates low IR-emissivity (17.6 % at 7–14 μm) and the carbon aerogel side has high solar absorptivity (91.97 %). Moreover, the AgNWs/carbon aerogel shows Joule heating performance (∆T = 44.5 °C within 3 min at 5 V). The multi-heating modes enabling self-adaptable thermal comfortable under various harsh environment. Additionally, the material's breathability, permeability, and electromagnetic shielding characteristics also make it suitable candidate for advanced wearable textiles for PTM.

Evaluation of the Electromagnetic Shielding Performance of UHPFRCC before and after Cracking

In this study, the crack distribution and electromagnetic shielding characteristics of UHPFRCC before and after cracking were evaluated according to fiber combinations. After evaluating the mechanical and electrical properties of each combination, an electromagnetic shielding test of a non-cracked panel specimen was conducted. Subsequently, the panel specimen was subjected to a monotonic load or repeated load. In the case of the test specimen with a repetitive load, the crack length, crack area, and electromagnetic shielding were measured at each load stage. According to the experimental results, the incorporation of organic fiber decreased the compressive strength and density of UHPFRCC. In particular, the incorporation of carbon fibers adversely affected the tensile behavior owing to dispersibility problems. The hybrid fiber combination increased the electrical resistivity. However, the incorporation of carbon fibers improved electromagnetic shielding performance compared with the single incorporation of steel fibers. The fiber combination significantly affected the crack length and width than the crack area. In addition, as cracks occurred, the electromagnetic shielding performance of a test specimen showed an average decrease of up to 20%.

Water vapor transmission and electromagnetic shielding characteristics of stainless steel/viscose blended yarn woven fabrics

In this study, stainless steel/viscose blended yarn was prepared and different structured woven fabrics were prepared for studying the moisture transmission and electromagnetic shielding behaviour. By doubling viscose spun yarn with SS filament yarn, the SS/viscose blended yarn was prepared. The woven fabrics were made in a sample loom using viscose yarn and SS/viscose blended yarn. By changing the metal content, thread density and conductive fibre proportions at different levels, the developed fabrics were analyzed for maximum shielding effectiveness in the frequency of 300 kHz to 1.5 GHz. The fabric having conductive threads in warp and weft directions showed larger shielding effectiveness (SE) compared to fabric having conductive threads in one direction. The increase in weft density, proportions of conductive threads (in weft direction) and metal content increases the shielding level of fabric. The highest SE of 56 dB was observed for plain woven fabric compared to 3/1 twill, 2/2 twill and 2/2 basket fabrics in the frequency of 700 MHz. The influence of environmental factors such as relative humidity and pH on shielding behaviour of fabrics were also studied. As the relative humidity was increased, the SE was also increased. The fabric treated with acidic (or) basic condition exhibited better SE than the fabric in neutral condition. Similarly, air permeability and water vapour transmission characteristics of the developed conductive fabrics were also analyzed. The air permeability of the fabric was higher when the metal content in the fabric was low. The fabric having more floats showed higher air permeability compared to fabrics with less floats. Similarly, the water vapour transmission rate was also high for long float fabrics. The developed conductive fabrics could be used as wall covering and personal protective clothing in defense industry.

Experimental Study on Electromagnetic Shielding Characteristics of a Fe-Based Amorphous Soft Magnetic Composite

An Fe-based amorphous soft magnetic composite with flexibility and elasticity was fabricated to shield harmful electromagnetic waves in industrial and military defense applications. Through the combination and structural arrangement of the amorphous soft magnetic sheet and the conductive sheet, the inlet (POE) form of electromagnetic waves was artificially diversified, and shielding performance was measured according to the criteria of MIL-STD-188-125-1 in the range from 1 kHz to 10 GHz, in consideration of the electromagnetic pulse (EMP) protection. As a result, the shielding effectiveness of 80 dB was achieved in a triple “sandwiched” structure by alternately stacking an iron-based amorphous soft magnetic material on top of a flexible conductive sheet at a 90-degree angle, rather than in parallel.

Electromagnetic shielding characteristics of carbon and glass fiber composites

Electromagnetic shielding characteristics for orientation angle and number of plies of carbon fiber reinforced epoxy composites were investigated in the frequency range between 900 and 6000 MHz. In this study, both unidirectional and bidirectional carbon fiber fabrics were utilized as reinforcement materials to manufacture the composite samples. Twill bidirectional glass fiber fabrics were also used in order to provide a large amount of flexibility. To prepare the composite laminates for measurement, hand lay-up method was preferred. Measurements were carried out by using DFG 4060 signal generator and HF 60105 spectrum analyzer. According to the measurements, it was observed that electromagnetic shielding effectiveness (EMSE) was very higher when the orientation angle of the carbon fiber was 90°, as compared to 0°. Another parameter that affects EMSE is whether the carbon fiber fabric used is unidirectional or bidirectional because it was observed that the bidirectional fabric increased EMSE. In addition, it has been determined that the number of plies has less effect on EMSE than the orientation angle.

SiC Nanofiber-Coated Carbon/Carbon Composite for Electromagnetic Interference Shielding

Carbon/carbon–silicon carbide (C/C-SiC) composites have been widely reported in aerospace and military projects for their mechanical properties and electromagnetic shielding characteristics. However, high production costs, a complex process, and poor electrical conductivity have prohibited the large-scale application of these excellent EMI shielding materials. Herein, in situ growth of the SiC nanofibers (SiCnf) on carbonized phenolic resin with the reinforcement of graphite fibers is proposed for a strategy to overcome this challenge. The laser-irradiated carbon fibers (LCFs) were filled into the phenolic resin and hot-pressing was conducted; thereafter, the C/C-SiC composites were obtained by high-temperature carbothermal reduction of the LCF/phenolic resin and the industrial silicon power. Because of the conductive network of the LCF, the dense carbon matrix and the decoration of nanoporous SiCnf, the as-prepared SiCnf grown on the LCF/carbonized phenolic resin (LCF/PC-SiC) composite exhibited an EMI shielding effectiveness of 27.86 dB in the X-band at room temperature. This work proposed a new strategy to efficiently fabricate C/C-SiC composites for electromagnetic shielding.

Analysis and Development Review of Metal and Metal/Ceramic Composite Coating Prepared on Magnesium Alloy Surface

Magnesium, as one of the lightest metal structural materials, also has its advantages such as high specific strength, good electromagnetic shielding characteristics, good processability and easy recycling, so it has a wide application prospect. However, its poor insulation, corrosion resistance, wear resistance and other properties limited it to be an alloy that can be used in a large area. Therefore, how to improve the corrosion resistance and wear resistance of magnesium alloy is the key to promote the development of magnesium alloy field. This paper reviews the research progress of using magnetron sputtering technology to prepare ceramic composite film on the surface of magnesium alloy and briefly introduces the film corrosion resistance and wear resistance of the thin films. It analyzes the impact of metal transition layer, process parameters and other factors on structure and properties of metal / ceramic coatings and prospects for the development prospects of magnetron sputtering in the field of magnesium alloy surface protection.

Aerodynamic characteristics analysis of quadrangle inlet and exhaust grille for embedded ventilation cooling system of aircraft

Adding grilles at the inlet and exhaust of the aircraft ventilation cooling system helps to improve the aerodynamic characteristics and electromagnetic shielding characteristics of the whole system. Taking the X-47B aircraft as the research object, the quadrilateral open inlet and exhaust ducts and their grilles of the ventilation and cooling system embedded in the fuselage are designed. Based on CFD method, the influence of four design parameters of intake and exhaust grille: diversion angle, grille thickness, aperture shape and aperture size on flow resistance characteristics of the pipeline system is analyzed. The results show that the flow resistance characteristics are better when the grille diversion angle of inlet and outlet is smaller and closer to the conventional inlet and outlet. For the inlet, the rectifier effect is better when the grille thickness is larger, and the outlet of the exhaust duct needs a suitable thickness of the grille to balance the rectification and exhaust resistance. Besides, the circular hole grille shows good effect in the inlet and exhaust port. The small flow rate of inlet needs to use small aperture grilles to increase the rectification effect and suppress the internal and external flow interference, while the small flow rate of exhaust channel uses large aperture grilles, and the large flow rate uses small aperture grilles to improve the mixing rectification efficiency of internal flow to external flow.

Cellulose-derived flexible carbonized paper for high-performance electromagnetic interference shielding

In this study, we describe the fabrication of flexible carbonized paper (f-CP) from toilet paper samples using a sandwich-type installation technique in a thermal chemical vapor deposition system. During the reaction, the substrate was heated up to 1000 °C at a rate of ~20 °C/min and naturally cooled down to room temperature in an Ar gas environment without temperature holding. The f-CP sample thus obtained contained continuous carbon fibers similar to the native toilet paper sample while carbonized paper (CP) fabricated using the conventional installation technique contained discontinuous carbon fibers. Compared to CP, f-CP exhibited higher electrical conductivity, mechanical flexibility, and shielding effectiveness (SE) against electromagnetic radiation. Even after bending the f-CP sample several hundred times, its SE decreased only slightly. Multi-layered f-CP (mf-CP; 3 mm thickness and 0.053 g/cm3 density) fabricated by stacking f-CP samples showed a remarkably high SE of 58 dB in the operating frequency range of 8.2–12.4 GHz. Therefore, f-CP and mf-CP, which exhibit excellent electromagnetic shielding characteristics, may potentially be used in electronic devices.

Evaluation of electromagnetic radiation shielding characteristics of facing building vaterials

The article presents the results of theoretical studies of the protective properties of composite facing materials based on a dielectric matrix with an electrically conductive non-magnetic filler in a wide frequency range of incident electromagnetic radiation. Expressions are got for the values of the transmission, reflection and absorption, and the electromagnetic radiation shielding efficiency calculated on their basis. The dependences of the permittivity and electrical conductivity of the composite on the volume fraction of the electrically conductive additive required for calculations were got based on the hypothesis of similarity, considering the nonzero conductivity of the dielectric matrix. Satisfactory agreement between the calculation results and the measured shielding characteristics of specimens of metal silicate materials based on calcium hydro silicates and copper powder was established. The results presented show the adequacy of the proposed calculation method and indicate that it can be used for preliminary estimates of the shielding characteristics when designing electromagnetic radiation shields based on composite facing materials.

Electrically Insulating Flexible Films with Quasi-1D van der Waals Fillers as Efficient Electromagnetic Shields in the GHz and Sub-THz Frequency Bands.

Polymer composite films containing fillers comprising quasi-1D van der Waals materials, specifically transition metal trichalcogenides with 1Dstructural motifs that enable their exfoliation into bundles of atomic threads, are reported. These nanostructures are characterized by extremely large aspect ratios of up to ≈106 . The polymer composites with low loadings of quasi-1D TaSe3 fillers (<3vol%) reveal excellent electromagnetic interference shielding in the X-band GHz and extremely high frequency sub-THz frequency ranges, while remaining DC electrically insulating. The unique electromagnetic shielding characteristics of these films are attributed to effective coupling of the electromagnetic waves to the high-aspect-ratio electrically conductive TaSe3 atomic-thread bundles even when the filler concentration is below the electrical percolation threshold. These novel films are promising for high-frequency communication technologies, which require electromagnetic shielding films that are flexible, lightweight, corrosion resistant, inexpensive, and electrically insulating.

Surface functionalization of nanostructured Cu/Ag-deposited polypropylene fiber by magnetron sputtering

Abstract Metallic nanoparticles are widely used due to their superior electrical, antimicrobial, and electromagnetic shielding characteristics. In this work, the surface functionalization of polypropylene (PP) fibers using magnetron sputtering with pure Cu and Ag targets in the presence of Ar gas was systematically investigated, in detail, in terms of surface morphology, tensile, abrasion resistance, moisture regain, antibacterial, and electrostatic properties. The results indicated that the nanocomposite films deposited on the PP surface were even and dense under proper treatment conditions. Compared with pristine fiber, breaking tenacity, abrasion resistance, and antibacterial properties of the Cu/Ag-deposited PP fibers were significantly improved, whereas the extension at break and moisture regain decreased in different degrees. Also, the electrostatic property of treated PP fabrics was studied. This work reveals that surface functionalization of Cu/Ag-deposited PP fiber is versatile, and the surface treatment that uses metallic nanoparticles by magnetron sputtering is a promising approach for achieving multifunctional textiles.

Influence of carbon fiber additions on the electromagnetic wave shielding characteristics of CNT-cement composites

This study examined the synergistic effect of carbon fiber (CF) addition on the electromagnetic wave shielding characteristics of carbon nanotube (CNT)-cement composites. Effect of the amount and length of CF on the electrical conductivity, electromagnetic interference (EMI) shielding effectiveness (SE), and complex permittivity of the composites were systematically investigated. The electrical conductivity was determined by means of a digital multimeter, and a network analyzer was used to measure the EMI SE and complex permittivity of the composites in the frequency range of 0.1 to 18 GHz. The electrical conductivity and complex permittivity of the composites incorporating 3 mm CF or 6 mm CF were shown to be proportional to the CF content, while the effect of CF length on the EMI SE was more pronounced as the CF length increased from 0.1 mm (aspect ratio 14) to 3 mm (aspect ratio 417). Enlargement of the aspect ratio of CF led to the enhancement of electrical conductivity and absorption loss of the composites, attributing to a notable increase in the SE.

Evaluating of Electromagnetic Shielding Characteristics of Reinforced Concrete Using Reinforcing Details

In this study, experimental tests were performed to determine the electromagnetic shielding characteristics of reinforced concrete based on the thickness of concrete and rebar. In addition, the electromagnetic shielding characteristics based on the steel-fiber volume ratio and rebar spacing of fiber-reinforced concrete were evaluated. Concrete showed significant Shielding Effectiveness (SE) in a high-frequency band with increasing thickness, but the rebar exhibited significant SE in the low-frequency band with increasing diameter, decreasing rebar spacing, and increasing layer. The SE increased with the steel fiber volume ratio, and it also increased owing to the decrease in the rebar spacing for 1.5 vol.% steel fibers.

Preparation and Characteristics of Graphene-based Polymeric Leather Fatliquor

Although the research of leather chemicals has experienced considerable advances, it remains imperative and challenging to develop functional ones; especially functionalized fatliquors or re-tanning agents. In consideration with the unique structure and properties, graphene oxide (GO) has been reported as a potential alternative to ameliorate the performance of leather. However, one of the intractable handicaps is how to make graphene penetrate evenly and react with collagen fibers. Here, we demonstrate a method for preparing graphene-based polymeric fatliquor (PFGO) via an amidation reaction between amino-groups of aminated graphene (AGO) and anhydride bonds of maleic anhydride-rapeseed oil copolymer (MRO), which was synthesized by free radical copolymerization. The results show that the as-prepared fatliquor has good emulsion stability and can penetrate into the collagen fibers uniformly. Compared with the control sample without graphene, the antibacterial, electromagnetic shielding, flame retardant and UV resistance characteristics of the PFGO-treated leather were significantly improved. Overall, this e?ective yet promising paradigm may provide an achievable solution toward developing graphene-based polymer composites simultaneously with high physical property and high functional performance.

Material Application of a Transformer Box: A Study on the Electromagnetic Shielding Characteristics of Al–Ta Coating Film with Plasma-Spray Process

In this study we present the results of two experiments. In the first one, a Ta–Al–SS (stainless steel (SS)) multilayer coating structure was prepared using plasma spraying equipment to investigate the coating structure and interface properties. In the second one, Ta–Al on multilayer glass was prepared using the sputtering process to measure the thickness effect of thin film on electromagnetic wave shielding (EMI) characteristics and on the design of high-power switchboard covers. According to the experimental results, the multilayer structure of Ta–Al on SS improves the mechanical properties of a stainless steel plate by enhancing the explosion-proof property. An appropriate thickness of the plasma-sprayed pure aluminum layer can increase the adhesion to the stainless steel substrate and buffer the stress effect. After heat treatment (annealing), the Ta–Al–SS multilayer structural characteristics are excellent and suitable for shielding effects at different temperatures and humidity, which can be used as a reference for the engineering application of communication rooms and base power stations. According to EMI test of multi-coated glass (Ta–Al–glass), by increasing the thickness of Ta layer, we cannot effectively improve full-frequency EMI shielding with improved shielding at low-mid frequency condition. In addition, the Ta–Al interface formation of an Al–Ta–O compound layer can improve the adiabatic effect to reduce the thermal conductivity.

Simulation Research on Electromagnetic Shielding Characteristics of Carbon Fiber Car Body for Railway Vehicles

The carbon fiber composite materials have been widely used in the field of rail transit.Carbon fiber body is more advantageous than traditional material especially in weight.This paper introduces main characteristics of carbon fiber composites and outlines the principles of electromagnetic shielding effectiveness.Electromagnetic shielding characteristics of carbon fiber reinforced polymer (CFRP) was studied through electromagnetic shielding simulation technology and test compared with aluminum, aluminum alloy and carbon steel. Some suggestions are provided in terms of the CFRP electromagnetic characteristics. This research sets a foundation for the EMC design for railway vehicles.

Electromagnetic shielding performance of three-dimensional woven fabrics with copper-based hybrid yarn in X-band frequency range

This study involves a comprehensive evaluation of electromagnetic shielding characteristics of multilayer three-dimensional conductive fabrics by using cotton/copper wrapped hybrid yarn in X band frequency range. Five, three-dimensional fabrics with different structural configuration, such as orthogonal, angle interlock, cellular spacer, multi-tubular spacer, and contour were produced. Three different series of all five structures was also developed using pure cotton fabric, conductive hybrid yarn in weft and one-third hybrid yarn and two-third cotton yarn in warp Also, the effect of vertical and horizontal polarization of electromagnetic waves on electromagnetic shielding effectiveness was studied. The comparative analysis of reflectance transmittance and absorption behavior was also undertaken. The results indicate that pure cotton fabric (A series) does not have electromagnetic shielding capabilities. The difference between the electromagnetic shielding effectiveness values in vertical and horizontal planes of fabrics, having conductive hybrid yarn in weft direction (B series), showed significantly better results on the vertical plane in comparison to that on the horizontal plane. Fabric containing conductive hybrid yarn in both warp and weft (C series) exhibits consistent electromagnetic shielding effectiveness in both the planes. It is worth mentioning that the structural configuration in all five three-dimensional fabrics in B and C series has shown differential trends of electromagnetic shielding effectiveness in terms of reflectance, transmittance and absorption behavior. They are also found to be statistically significant. Finally, it is concluded that the conductive 3-D multilayer system develops special protective capabilities, mostly due to its larger surface area.

Electromagnetic Shielding Characteristics of Eco-Friendly Foamed Concrete Wall

The electromagnetic shielding characteristics according to the material composition of foamed concrete, which was manufactured to reduce environmental pollution and to economically apply it in actual building walls, were researched herein. Industrial by-products such as ladle furnace slag (LFS), gypsum, and blast furnace slag (BFS) were added to manufacture foamed concrete with enhanced functionalities such as lightweight, heat insulation, and sound insulation. The electrical characteristics such as permittivity and loss tangent according to the foam and BFS content were calculated and measured. Free space measurement was used to measure the electromagnetic shielding characteristics of the actually manufactured foamed concrete. It was confirmed that electromagnetic signals were better blocked when the foam content was low and the BFS content was high in the measured frequency bands (1–8 GHz) and that approximately 90% of the electromagnetic signals were blocked over 4 GHz.

Microstructure and Electrochemical Characterizations of Mn-Ce Conversion Coating on LZ91 Magnesium Alloy

In the past few years, the energy crisis and environmental issues have been emphasized. In order to reduce the greenhouse effect and enhance the efficiency of energy consumption, each country has enacted relative laws to decline the emission of carbon dioxide year by year. Magnesium alloys, the lightest structural metal, have found their potential use in the aerospace, automobile, tool, and electronic industries due to their attractive damping capacity, high specific strength and specific stiffness, as well as good electromagnetic shielding characteristics. In comparison to the AZ (with aluminum and zinc as the major alloy elements) series magnesium alloys, the LZ (with lithium and zinc as the major alloy elements) series magnesium alloys have been developed by substituting aluminum with lithium. However, because of the difference in the standard reduction potential between the α phase and the β phase and the presence of active lithium, Mg-Li alloys display poor corrosion resistance. Surface modification is thus essential for Mg-Li alloys. In this study, the main theme is aimed at the improvement of phosphate/permanganate conversion coating. With substituting phosphate for cerium (III), magnesium dissolved more magnesium ions and released more electrons to enhance the oxidation-reduction reaction. The conversion coating showed better adhesion and less severe crack by virtue of increasing the chemical reactivity and lowering the immersion time, expecting to replace hexavalent chromate conversion coating and reduce the cost. The LZ91 magnesium alloys were mechanically grinded up to 1200 grade silica emery paper, rinsed with deionized water, and dried with an air stream. The conversion coating treatment was conducted in the solution composed potassium permanganate (KMnO4) and cerium nitrate (Ce(NO3)3). The pH of the solution was about 1.5-4.5. After conversion coating treatment, the LZ91 plate was rinsed in deionized water and left drying overnight at room temperature. Based on the microstructural, and XPS, the formation and deposition mechanism of the Mn-Ce conversion coating on LZ91 is discussed in detail. The corrosion resistance of the coating was characterized by potentiodynamic polarization, electrochemical impedance spectroscopy (EIS), and salt spray tests (SST). The results of the electrochemical measurement and SST demonstrated that the corrosion resistance of LZ91 alloy was markedly improved by the Mn-Ce conversion treatment. Figure 1. shows the potentiodynamic polarization curves of bare LZ91 and the various Mn-Ce coated LZ91 plates (for pH=1.5) in 0.05 M NaCl and 0.1 M Na2SO4 solution. In general, the cathodic reaction in the polarization curve is related to the evolution of hydrogen and the anodic polarization curve is the characteristics corresponding to the corrosion resistance of the coating. Both the cathodic and anodic reactions were inhibited in the presence of the conversion coating, indicating the coating effectively enhances the corrosion resistance of the LZ91. And, the values of electrochemical corrosion parameters were shown in Table 1. In contrast with the un-coated LZ91 alloy, the corrosion current density Icorr of the Mn-Ce coated LZ91 plates was decreased by one orders of magnitude (with the value from 46.9 µA/cm2 to 1.78 µA/cm2), which functioned as a barrier. References S. Y. Jian, Y. R. Chu, C. S. Lin, Corrosion Science 93(2015) 301-309 C. Wang, F. Jiang, F. Wang, Corrosion Science 46 (2004) 75–89G. Bikulčius, A. Ručinskienė, A. Sudavičius, V. Burokas, A. Grigucevičienė, Surface & Coatings Technology 203(2008) 115–120 H. Zhang, G. Yao, S. Wang, Y. Liu, H. Luo, Surface & Coatings Technology 202 (2008) 1825–1830 L. Yang, J. Li, X. Yu, M. Zhang, X. Huang, Applied Surface Science 255 (2008) 2338–2341 C. S. Lin, S. K. Fang, Journal of The Electrochemical Society, 152 (2) B54-B59 (2005) Figure 1