Composites For Electromagnetic Shielding Research Articles

Multifunctional AgNWs@MXene/AgNFs electromagnetic shielding composites for flexible and highly integrated advanced electronics

The electromagnetic interference and heat accumulation pose a significant challenge for the traditional high-density single-function electromagnetic shielding materials in advanced flexible integrated electronics. Herein, nano-silver flakes (AgNFs, reflective layer), MXene (Ti3CNTx, loss layer) and silver nanowires (AgNWs, heat conduction and shielding layer) constructed ordered multi heterogeneous layers high-performance flexible electromagnetic shielding functional composites (AMA composites). Especially the composites exhibited outstanding electromagnetic interference shielding efficiency (EMI SE) of 70.96 dB even with an extremely thin coating of 25 g/m2, which is 350% higher than that of the commercial standard (20 dB). It is worth noting that the AMA composites also possessed certain qualities such as superior thermal conductivity, flame retardancy, chemical resistance, high-temperature resistance (25 °C–100 °C), and mechanical properties (tensile strength of 44.4 MPa, Young's modulus of 0.6 GPa). The composites display application possibilities in highly integrated advanced flexible electronic products and wearable electronic devices, as well as provide structural design and research ideas for the usage of a new MXene material (Ti3CNTx) in electromagnetic shielding composite materials.

Constructing PA6/PS composite foam with porous and hybrid isolation structure to synergistically control absorption and electromagnetic interference shielding effectiveness

AbstractIsolation structure has been proven to be an effective method for constructing electromagnetic shielding composites, achieving high electrical conductivity with shallow filler content and high‐efficiency electromagnetic shielding. However, there are still many challenges in further optimizing the design and improving absorption. This article designed a hybrid isolation structure using nylon magnetic microspheres and polystyrene (PS). First, we prepared PA magnetic microspheres (Ni@PA6M) with Ni nanoparticles uniformly dispersed by the reaction induced phase separation (RIPS) method, then mixed with MWCNT and PS at high speed and formed by hot pressing. Under the optimized ratio, the hybrid structure has more interfaces and a more complete conductive network. Simultaneously, the magnetic microspheres can promote the absorption of electromagnetic waves, thereby improving the electromagnetic shielding performance of the material. When the MWCNT content is 7 wt%, Ni@PA6M:PS = 7:3, the total shielding effectiveness (EMI SET) and reflection coefficient (R) of the composite reached 28.6 dB and 0.77, respectively, while the EMI SET and R of the composite constructed with pure nylon microspheres and PS are 26.1 dB and 0.74, respectively. Further, using supercritical CO2 foaming technology to foam the PS phase in the composite to form many cells can improve the impedance matching and absorption of electromagnetic waves. The results show that introducing the cell structure reduces the reflection coefficient (R) from 0.77 to 0.69, and the EMI SET drops to a certain extent. Introducing the hybrid isolation and porous structure we designed provides a new idea for creating electromagnetic shielding materials for isolation structures.

Experiment and simulation of flexible CNT/SA/PDMS electromagnetic shielding composite

Flexible electromagnetic shielding composites have a great potential for wide range applications. In this study, two flexible composites were produced by plating Ni nanoparticles on carbon nanotubes (CNTs) or infiltrating carbon nanofibers/polydimethylsiloxane (CNF/PDMS) polymer into CNT/sodium alginate (CNT/SA) sponge skeleton (CNT/SA/CNF/PDMS composites). The composites are tested under the X band in the frequency range of 8.2 – 12.4 GHz, the electromagnetic interference shielding effectiveness (EMI-SE) values of the above two composites are almost as twice as that of CNT/SA/PDMS composite at a same CNT loading. Introducing nano-sized Ni particles on CNT improved the microwave absorption capacity of the composite, while adding CNF on the PDMS matrix enhanced the conductivity of these composites. Under 10% strain, both flexible composites show stable conductivity. Simulation and calculation results shown that increasing the cladding rate of Ni nanoparticles on the surface of CNT, reducing the average size of Ni particles, and increasing the loading of CNF in PDMS matrix can significantly improve conductivity and then EMI performance of the materials. All of these could benefit for the design of flexible electromagnetic shielding composites.

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.

Achieving structurally and functionally integrated electromagnetic shielding composites based on polyetheretherketone by sandwich structure

This study aims to prepare a structurally and functionally integrated polyetheretherketone/multi-wall carbon nanotubes (PEEK/MWCNTs) electromagnetic shielding composites by sandwich structure. The PEEK ultra-fine powder and MWCNTs mixed by mechanical blending were selected as the core-layer and PEEK-based film acted as the surface-layer. The results indicate that the electromagnetic shielding effectiveness (SE) and mechanical properties of the composites can be controlled by adjusting the ratio of PEEK which was chosen as the binder in the core-layer, the number of the core-layer and the composition of the surface-layer without sacrificing their thermal stability. Moreover, the specific electromagnetic shielding effectiveness (SSE), electrical conductivity, tensile strength and temperature of 5% weight loss (Td5%) of the optimized PEEK/MWCNTs composite reach 79.5 dB/mm, 1.8 S/cm, 93 MPa and 594°C, respectively. The performances of the above composite are obviously superior to those of the recently reported EMI composites. The improvements in the properties should be mainly attributed to the two factors: the dense conductive network formed by MWCNTs in the core-layer, and the good interface adhesion between MWCNTs-MWCNTs in the core-layer as well as between the core-layer and the surface-layer.

Preparation of CF/Ni-Fe/CNT/silicone layered rubber for aircraft sealing and electromagnetic interference shielding applications

To meet the needs of preventing information leakage in space engineering and military industry, an efficient method was introduced to obtain layered electromagnetic shielding sealing rubber. The carbon fiber, Ni-Fe coating, and Carbon NanoTube (CNT) were combined by chemical plating and in-situ polymerization to obtain a lightweight (0.14 g/cm2) and thin (1 mm thick) Carbon fiber Fabric (CF)/Ni-Fe/CNT/silicone layered electromagnetic shielding composites. The layered material obtained by adjusting the electroless plating time exhibited a high Shielding Efficiency (SE) of 60.2–85.5 dB in the range of 0–4800 MHz, which can be used for aviation electromagnetic shielding. Carbon fibers and carbon nanotubes mainly attenuated electromagnetic waves through absorption loss, while the nickel-iron alloy coating through reflection loss interacted with the magnetic vector of incident ElectroMagnetic (EM) radiation and magnetic dipoles, therefore, the EM Interference (EMI) shielding composite attenuated EM waves with the “absorption-reflection-absorption” cooperative interaction. Moreover, the flexible fabric substrate adhered with silicone rubber possessed a breaking elongation of 52.3%, which can be utilized as a good sealing material. Simultaneously, the outstanding exothermicity (67.2 °C under the applied voltage of 5 V) makes it possible to be applied in electric heating area. The electromagnetic shielding composites prepared in this paper have good potential in the fields of precision electronic equipment and aviation systems.

Flexible, electrothermal-driven controllable carbon fiber/poly(ethylene-co-vinyl acetate) shape memory composites for electromagnetic shielding

Carbon fiber felt (CFF) has a broad range of applications in electromagnetic interference (EMI) shielding because it is a multi-functional rigid material with a conductive property. In the present work, the flexible and intelligent CFF/poly(ethylene-co-vinyl acetate) (EVA) EMI shielding composites with electrothermal-driven shape memory performance was prepared by hot-pressing method, which provide precise and convenient control-method for driving EMI shielding conversion. As revealed, the CFF/EVA composites can achieve an EMI shielding effect of 45.6 dB in X-band and maintain a ca. 99% shape memory recovery ratio. Moreover, the composites can quickly return to the original shape at low voltage, and realize accurate and fast remote emergency control EMI shielding. The excellent flexible, intelligent and controllable high-performance EMI shielding effect of the CFF/EVA composites will play a key role in the frontier fields of flexible electronic equipment, actuators, chip protection, and information security.

Multifunctional Graphene Composites for Electromagnetic Shielding and Thermal Management at Elevated Temperatures

AbstractA method for scalable synthesis of epoxy composites with graphene and few‐layer graphene fillers is described, and the electromagnetic interference (EMI) shielding and thermal properties of such composites at elevated temperatures are reported. The tested materials reveal excellent total EMI shielding of SET ≈ 65 dB (≈ 105 dB) at a thickness of 1 mm (≈ 2 mm) in the X‐band frequency range. At higher filler loading fractions, composites reveal a room‐temperature cross‐plane thermal conductivity of 11.2 ± 0.9 Wm−1 K−1, which is a factor of ×41 larger than that of the pristine epoxy. Interestingly, the EMI shielding efficiency improves further as the temperature increases while the thermal conductivity remains approximately constant. The enhancement in the EMI shielding is explained by the temperature dependence of the two electrical conduction mechanisms, electronic band‐type conduction inside the fillers, and hopping conduction between the fillers. The excellent EMI shielding and heat conduction characteristics of such multifunctional graphene composites at high temperatures are promising for packaging applications of microwave components where EMI shielding and thermal management are important design considerations.

Lightweight microwire/graphene/silicone rubber composites for efficient electromagnetic interference shielding and low microwave reflectivity

Most traditional fillers used in electromagnetic shielding composites require high loading, uniform distribution and complicated structures for modest property enhancement. Here, we propose a simple shielding system incorporating magnetic microwires M and graphene fibers G in different arrangements. Integrating both fillers in the composite resulted in superior shielding effectiveness (SE) with respect to incorporating either individual type of filler, due to improved absorption efficiency, impedance matching and polarization triggered by different arrangements of the fillers. Randomly dispersed arrays provided a maximum shielding of 6 dB for equal amount of G and M, in which polarization effects at the interface between the two regions contributed to the SE value. The highest SE of 18 dB (98.4% attenuation) was reached by the MMMGGG periodic arrays with merely 0.059 wt% filler loading enabled by the optimized arrangement and wave attenuation from the microwires dielectric/magnetic response. The normalized SE of this composite was about two to four orders of magnitude higher than that of many other shielding candidate materials. High SE, low loading, simple structure, and multifunctionality make these composites attractive for several applications. Moreover, tailoring topological and structural factors of both fillers would facilitate further SE enhancement without sacrificing the important lightweight advantage.

Conductive polyaniline-coated poly(p-phenylenetere phthamide) yarn-reinforced multiaxial composites for electromagnetic shielding

Poly(p-phenylenetere phthamide) fiber is a high-performance synthetic fiber whose reinforced composites are widely used for their advantages of high strength and lightweight. However, the further potential usage of poly(p-phenylenetere phthamide) and its reinforced composites is limited in areas such as antistatic materials, conducting materials, and electromagnetic shielding materials due to their high electrical insulation. To improve the electrical conductivity, an online polymerization coating technology was used to manufacture conductive poly(p-phenylenetere phthamide)/polyaniline composite yarns continuously. The conductive poly(p-phenylenetere phthamide)/polyaniline composite yarns’ structure and properties such as surface morphology, electrical conductivity, Fourier-transform infrared spectroscopy spectra, thermogravimetric performance, and mechanical properties were studied in details. Then, three kinds of multiaxial composites were prepared by using the conductive poly(p-phenylenetere phthamide)/polyaniline composite yarn as the reinforcement and unsaturated polyester resin as a matrix, and the electromagnetic shielding performance of the composites was measured. The results indicated that the conductivity of conductive poly(p-phenylenetere phthamide)/polyaniline composite yarn can reach to ∼160 S/m. The thermogravimetric performance of poly(p-phenylenetere phthamide) was reduced after conductive treatment. The mechanical properties of the composite yarns, such as the breaking strength and elongation, remained unchanged when the oxidant concentration was lower than 0.6 mol/L and decreased with the increase in the oxidant concentration. The electromagnetic shielding composites show a certain anti-electromagnetic radiation capability, and the shielding effectiveness value increased with the axial number and density of the conductive poly(p-phenylenetere phthamide)/polyaniline composite yarns. For the tetra-axial composite with a conductive yarn density of 37 yarns per inch, the average shielding effectiveness value in the frequency range of 100 MHz to 1500 MHz can exceed 22 dB.

Lightweight sandwich fiber-welded foam-like nonwoven fabrics/graphene composites for electromagnetic shielding

With the remarkable increment speed of consumer electronics, shielding materials qualified for favourable minimal thickness, mechanical behaviors and efficient conduction path are imperiously demanded. To manufacture desired shielding materials qualified for favourable mechanical behaviors and efficient conduction path, we designed a foam-like nonwoven multiscale composite with welding-network, sandwich and random orientation combined architectures for the first time. A 0.5-mm-thick epoxy composite exhibits an outstanding shielding effectiveness of 65 dB, and the specific electromagnetic interference shielding effectiveness reaches to ∼23103.4 dB cm2 g−1, which surpassed that in reported literature. The continuous backbone with sandwich microstructure enables the epoxy composites to be mechanically robust with the tensile MPa of 349. The exceptional mechanical performance exhibited an alternative approach to exploit potentials of carbon fiber-based nonwoven fabrics for developing advanced multifunctional materials.

Segregated double network enabled effective electromagnetic shielding composites with extraordinary electrical insulation and thermal conductivity

Miniaturization and high frequency are two key features of the next generation electronic devices, thus advanced electronic packaging materials with high thermal conductivity and excellent electromagnetic shielding performance (EMI SE) are highly expected. This work presents poly (vinylidene fluoride)@multi-wall carbon nanotube/boron nitride (PVDF@MWCNT/BN) composites with effective EMI SE and satisfactory insulation and thermal conductivity through a tailor-made segregated double network. PVDF@MWCNT composite microspheres were fabricated as the thermal and electrical conductive micro-network, then another BN macro-network was further prepared to provide electrical insulation and further thermal conductivity enhancement. This so-called double segregated network of PVDF@MWCNT/BN composites shows a thermal conductivity of 0.83 W m−1 K−1, electron insulation of 8.33 × 10−14 S cm−1 and electromagnetic shielding of 8.68 dB at 8.2 GHz when loaded 5 wt% MWCNT and 40 wt% BN. The study sheds new lights on the development of special functional materials and the PVDF@MWCNT/BN composites are highly promising as a future electronic packaging material.

Flexible and conductive polyurethane composites for electromagnetic shielding and printable circuit

With recent emergence of portable and wearable electronics, it is imperative to design a novel electromagnetic interference (EMI) shielding material which possesses flexibility, ultra-thinness and excellent EMI shielding effectiveness (SE) to prevent the adverse effect of electromagnetic radiation. Herein, we fabricate the ultrathin and flexible four corners needle zinc oxide whiskers/silver/waterborne polyurethane (T-ZnO/Ag/WPU) conductive films to realize different EMI shielding demand by tuning the nanofiller dispersion morphology. The T-ZnO/Ag/WPU composite film with uniform structure (prepared by blade coating method) shows excellent flexibility and EMI SE of over 42 dB at a thickness of only 0.02 mm. Highly reliable shielding ability is achieved with 92% EMI SE retention after 1000 folding cycle tests. The T-ZnO/Ag/WPU composite film with deposited layer structure (prepared by casting method) exhibits an ultrahigh EMI SE of over 87 dB at a thickness of 0.25 mm. At the same time, the T-ZnO/Ag/WPU composite shows great potential in printable circuit. The ultrathin and flexible T-ZnO/Ag/WPU composite films with excellent EMI SE are highly promising for applications in next-generation flexible electronics, especially the portable and wearable electronic devices.

Dual‐Functional Graphene Composites for Electromagnetic Shielding and Thermal Management

AbstractThe synthesis and characterization of epoxy‐based composites with few‐layer graphene fillers, which are capable of dual‐functional applications, are reported. It is found that composites with certain types of few‐layer graphene fillers reveal an efficient total electromagnetic interference shielding, SEtot ≈ 45 dB, in the important X‐band frequency range, f = 8.2 −12.4 GHz, while simultaneously providing high thermal conductivity, K ≈ 8 W m−1 K−1, which is a factor of ×35 larger than that of the base matrix material. The efficiency of the dual‐functional application depends on the filler characteristics: thickness, lateral dimensions, aspect ratio, and concentration. Graphene loading fractions above the electrical and thermal “percolation thresholds” allow for strong enhancement of both the electromagnetic interference shielding and heat conduction properties. Interestingly, graphene composites can block the electromagnetic energy even below the electrical percolation threshold, remaining electrically insulating, which is an important feature for some types of thermal interface materials. The dual functionality of the graphene composites can substantially improve the electromagnetic shielding and thermal management of airborne systems while simultaneously reducing their weight and cost.

Resistance gradient polymeric electromagnetic shielding composites: Preparation and Characterization

Based on the principle of Stokes’ law, a series of polyvinyl butyral (PVB)/nickel (Ni) composite films with a resistance gradient were successfully prepared using a suspension casting method with the aid of gravity. Gradient distribution structure, conductive and mechanical properties, and electromagnetic shielding effectiveness (SE) were investigated. Scanning electron microscopy (SEM) observations and energy‐dispersive spectrometer (EDS) detection show that the gradient distribution of Ni particles in the PVB matrix was formed along the thickness‐direction. A surface resistivity difference of 10 orders of magnitude appears between the top surface (PVB‐rich side) and the bottom surface (Ni‐rich side). Percolation transformation occurs in the range of Ni content of 3.0∼4.5 vol% at the Ni‐rich side, which is much lower than that of PVB/Ni composites with homogeneous Ni distribution. The gradient distribution structure grants the composite both good electromagnetic shielding performance and good mechanical properties. When the Ni loading reaches 10.5 vol% in the film, its SE value rises to 30 dB, which is 15 dB higher than that of a homogenous film with the same filler content. It is believed that electrically conductive gradient polymeric composites have potential application value in the field of electromagnetic shielding. POLYM. COMPOS., 40:1842–1849, 2019. © 2018 Society of Plastics Engineers

Polypyrrole-MWCNT-Ag composites for electromagnetic shielding: Comparison between chemical deposition and UV-reduction approaches

In this study, we focused on the synthesis of polypyrrole-MWCNT-Ag composites and we evaluated their electrical properties to determine the electromagnetic interference shielding performance. We reduced silver nanoparticles in composites using two different in situ methods: UV-reduction and chemical deposition. Composites were characterized using spectroscopic and microscopic tools for evaluation of the chemical, morphological, electrical conductivity and electromagnetic shielding effectiveness. Results from Fourier transform infrared spectroscopy and dispersive Raman microscope showed chemical interactions between silver and the polypyrrole-MWCNT composite due to the charge-transfer within the structure. X-ray diffraction confirmed appearance of two new peaks for silver nanoparticles embedded in polypyrrole-MWCNT independent to reduction method. According to microscopy images, silver nanoparticles were homogenously distributed at the PPy-MWCNTs interfaces by UV reduction, while, chemical reduction resulted to deposition of silver within the PPy matrix. Finally, our results revealed that the polypyrrole-MWCNT-Ag composite produced via UV-reduction has higher electrical conductivity and shielding effectiveness in comparison to chemically reduced one.

Electrically conductive carbon fiber / PEKK / silver nanowires multifunctional composites

New multifunctional composites with high through-thickness electrical conductivity were elaborated with carbon fiber (CF) reinforced PEKK filled with silver nanowires (AgNWs). Composites were fabricated by film stacking at high temperature for the first series of samples and by powder impregnation for the second series. Morphological analysis of composites was performed by scanning electron microscopy (SEM) in order to check impregnation quality of carbon fibers and dispersion of AgNWs across the ply. Electrical conductivity was measured in the out-of-plane direction of laminates and recorded as a function of the volume fraction of silver nanowires. It was observed that the presence of small fractions of AgNWs (∼1.5 vol%) within the carbon fiber reinforced PEKK increased the transverse conductivity of non-filled CF/PEKK laminates by at least 3 orders of magnitude. The maximum conductivity achieved by laminates is 250 S m−1. These new multifunctional composites may be used as structural high performance composites for electromagnetic shielding, or lightning strike protection.

Characteristics and properties of wood/polyaniline electromagnetic shielding composites synthesized via in situ polymerization

Semiconducting wood/polyaniline (PANI) composites were synthesized via in situ polymerization of aniline monomer, which was impregnated into the wood veneer in advance. Thus, the resulting composites exhibited the characteristics of the conducting PANI and natural wood. The light microscopy and scanning electron microscopy images showed that PANI was uniformly dispersed into the wood substrate. The weight percent gain and volume bulk increase of the composites were 16.13% and 6.21%, respectively. The equilibrium water absorption studies showed that the composites were less hydrophilic, because of the addition of hydrophobic PANI. The electrical conductivity of the wood/PANI composite ranged from 2.57 × 10−5 to 9.23 × 10−3 S cm−1 and was tuned by changing the phosphoric acid concentration. The electromagnetic shielding effectiveness of the wood/PANI composites was mainly in the range 30–60 dB, which may be used for general industry or commercial electronics. Fourier transform infrared spectra revealed that PANI was closely polymerized onto the wood substrate and allowed the accessibility of the amine groups of the aniline to the hydroxyl groups of the wood. Furthermore, the X‐ray diffraction analysis indicated that the crystal lattice of the crystalline cellulose region was not damaged, and the relative crystallinity of wood increased. POLYM. COMPOS., 39:537–543, 2018. © 2016 Society of Plastics Engineers

Effect of different photoinitiators on the properties of UV-cured electromagnetic shielding composites

Abstract A series of UV-cured electromagnetic shielding composites (UV-EMSC) containing different content of graphene oxide (GO) were prepared with oligomer, acrylate active diluents and different photoinitiators (Darocur 1173, Irgacure 184 or Irgacure 651). To fabricate conductive oligomer with low resistivity, polyurethane-acrylate (PUA) was used as the polymer matrix to help construct two-dimensional conductive networks consisting of GO. For forming conductive network structure, the surface functional groups (-OH, -COOH) of GO served as slightly conductive particles bonded with -NCO from the chain of polyurethane. The UV-EMSC exhibited a low resistivity of approximately 402 Ω·cm and an outstanding enhanced electrical conductivity of 249 mS/m at a GO content of 0.0200%. The effects of different photoinitiators on the properties of UV-cured films were investigated. The results indicate that the prepared UV-EMSC has great potential applications in different regions, such as in coatings of electronic, electrical, communications, plastic coatings and wood finishes.

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.