Excellent Electromagnetic Interference Shielding Effectiveness Research Articles

Polyaniline-decorated carbon fibers for enhanced mechanical and electromagnetic interference shielding performances of epoxy composites

The development of carbon fiber-reinforced polymers (CFRPs) with high electromagnetic interference (EMI) shielding effectiveness is highly desirable for engineering applications. Nevertheless, poor interfacial adhesion between carbon fibers (CFs) and polymer matrix remains a serious issue. Herein, a mechanically enhanced CF/epoxy composite with highly efficient EMI shielding was fabricated through in-situ polymerization of polyaniline (PANI) nanolayer. The PANI nanolayer improved the interfacial adhesion in the composites via the entanglement of molecular chains, π–π stacking, and chemical bonding et al. The resulting CF/PANI/epoxy composite exhibited an interlaminar shear strength of 72.8 MPa, which was a 24% improvement over 58.5 MPa for the virgin CF/epoxy composite. Moreover, an excellent EMI shielding effectiveness of 54.8 dB was achieved, which was 58% higher than that of the virgin CF/epoxy composite. This could be attributed to the significant enhancement in conduction loss, interfacial polarization loss, and multiple reflections with the help of PANI nanolayer. This study provides a novel strategy for the development of high-performance CFRPs for efficient EMI shielding.

Reduced Graphene Oxide/MXene Composite Foam with Multilayer Structure for Electromagnetic Interference Shielding and Heat Insulation Applications

The electromagnetic interference (EMI) shielding performance of reduced graphene oxide (rGO) foam is restricted to its poor conductivity and macro‐monotonic structure. In this work, highly conductive MXene nanosheets are introduced into graphene oxide (GO) solution and multilayer structures were designed to improve the EMI shielding performance of graphene foam. The multilayer rGO/MXene composite foam shows an excellent EMI shielding effectiveness of more than ≈28 dB in C and ≈35 dB in X band. Meanwhile, it reveals an outstanding heat insulation performance equaling to air (0.025 W m−1 K). The macro multilayer and microporous structure plays a prominent role in the EMI shielding and heat insulation performance. This work provides valuable ideas for designing multifunctional EMI shielding materials for the next generation of smart electronic devices.

A Multifunctional Flexible Composite Film with Excellent Multi‐Source Driven Thermal Management, Electromagnetic Interference Shielding, and Fire Safety Performance, Inspired by a “Brick–Mortar” Sandwich Structure

AbstractThe rapid development of portable flexible electronic devices means a multifunctional composite film with excellent thermal management capability, high electromagnetic interference (EMI) shielding, and a strong fire safety performance is urgently required. In this paper, inspired by a “brick–mortar” sandwich structure, phase change capsules (PCCs) and MXene nanosheets are prepared. Subsequently, a one‐step vacuum‐assisted filtration method is used to fabricate a multifunctional flexible PCC/MXene/polyvinyl alcohol (PMP) phase change composite film with high light‐to‐thermal conversion efficiency, Joule heating generation, fire safety, and EMI shielding effects. The superior preparation technology endows the film with multi‐source driven thermal management capabilities and excellent EMI shielding effectiveness values (43.13 dB). In addition, the PMP film exhibits good flexibility and high enthalpy (136.8 J g−1). Surprisingly, the PMP film's excellent fire safety properties improve its reliability and safety. In summary, the simple preparation technique and outstanding overall performance of the PMP films provide broad application prospects in advanced thermal management and EMI shielding in wearable products.

Constructing hierarchical structure via in situ growth of CNT in SiO2-coated carbon foam for high-performance EMI shielding application

Carbonated melamine foam (CMF) with a three-dimensional (3D) inner connected network is considered as one of the promising candidates to fabricate electromagnetic interference (EMI) shielding materials. To further improve EMI shielding performance, CMF based hybrids with three-dimensional structure by the combination of SiO2 and in-situ growth carbon nanotubes (CNT) have been synthesized for preparing polydimethylsiloxane (PDMS) composite: CMF@SiO2-CNT/PDMS. Owing to the structural match between the length of CNT and the diameter of holes in the CMF@SiO2, the relatively high electrical conductivity of 50.43 S/m has been achieved in the composite with the thickness of 2 mm, which assures an excellent EMI shielding effectiveness (SET = 61.34 dB) in the frequency range from 8.2 to 12.4 GHz. Meanwhile, a high absorption effectiveness (SEA = 53.65 dB) of the composite infers an absorption dominant performance of the composite because of the unique porous structure and inter-connected conductive network, which helps to avoid secondary EMI pollution. We hope this work can provide a new route for fabricating EMI shielding materials with high performance.

Nature inspired hierarchical structures in nano-cellular epoxy/graphene-Fe3O4 nanocomposites with ultra-efficient EMI and robust mechanical strength

• Nacre/bone like hierarchical structures in epoxy-based nanocomposites. • Simple compression molding with eco-friendly supercritical CO 2 foaming process to achieve porous layered nanocomposites. • Lightweight nano-cellular (52.6 nm) nanocomposite with 75 wt.% rGO-Fe 3 O 4 loading. • Low density (1.26 g/cm 3 ) and high specific EMI SE >5200 dB/cm 2 /g, with preserved tensile strength of 67 MPa achieved. Hierarchical layered structures, whether in a compact form like nacre or a porous manner like bone, are well known for their combined features of high stiffness, strength, and lightweight, inspiring many man-made materials and structures for high performance applications. The use of nacre/bone like hierarchical structures in polymer nanocomposites can achieve excellent mechanical and functional properties with high filler volume fractions after carefully aligning functional nanofillers, although the fabrication and processing remain a great challenge. In this work, a bio-inspired lightweight nano-cellular epoxy/graphene-Fe 3 O 4 nanocomposite with high nanofiller loading of 75 wt.% was successfully fabricated by combining features from both nacre and bone structures, via a simple compression molding process together with an eco-friendly supercritical CO 2 foaming process to achieve robust mechanical strength and excellent electromagnetic interference (EMI) shielding effectiveness (SE) simultaneously. Highly aligned graphene-Fe 3 O 4 nanoplatelets with well controlled nanoscale porous structures (52.6 nm) enabled both low density (1.26 g/cm 3 ) and high specific EMI SE >5200 dB/cm 2 /g, as well as preserved tensile strength of 67 MPa. This study provides a sustainable route to fabricate nature mimicked structures with high performance and high flexibility for a wide range of applications, from portable electronics to healthcare devices.

Electromagnetic asymmetric films comprise metal organic frameworks derived porous carbon for absorption-dominated electromagnetic interference shielding

Electromagnetic interference (EMI) shielding materials with low thickness, outstanding mechanical flexibility, especially absorption-dominated high performance, continue to be a significant challenge. Herein, environmentally friendly and mechanically robust double-layered zeolitic imidazolate framework-67 (ZIF-67) derived porous carbon (C-ZIF67) and graphene nanoplate (GNP) films based on cellulose were fabricated via filtration-assisted self-assembly followed by hot-pressing. The optimum double-layered composite films with 0.1 mm thickness exhibit excellent mechanical properties with a tensile strength of 46.33 MPa, superior EMI shielding effectiveness (SE) of 50.5 dB in the X-band frequency range, with an absorption coefficient (A) of 0.87, and the absorption rate (SE A /SE T ) is as high as 98.7%, benefiting from the highly efficient asymmetric conductive network structures and high-performance cellulose nanofibers (CNFs) matrix. The results indicated that “absorption-reflection-reabsorption” asymmetric double-layered functional network structured films possess excellent potential for applications in absorption-dominated EMI shielding fields. • Double-layered asymmetric conductive network structure is designed for EMI shielding. • The ultrathin film shows excellent EMI shielding effectiveness. • It features an absorption-dominated EMI shielding mechanism. • Cellulose nanofiber as a matrix for the C-ZIF67/GNP composite exhibits excellent mechanical properties and stability.

Multifunctional Wearable Silver Nanowire Decorated Leather Nanocomposites for Joule Heating, Electromagnetic Interference Shielding and Piezoresistive Sensing

AbstractMultifunctional wearable electronic devices based on natural materials are highly desirable for versatile applications of energy conversion, electronic skin and artificial intelligence. Herein, multifunctional wearable silver nanowire decorated leather (AgNW/leather) nanocomposites with hierarchical structures for integrated visual Joule heating, electromagnetic interference (EMI) shielding and piezoresistive sensing are fabricated via the facile vacuum‐assisted filtration process. The AgNWs penetrate the micro‐nanoporous structures in the corium side of leather constructing highly‐efficient conductive networks. The resultant flexible and mechanically strong AgNW/leather nanocomposites exhibit extremely low sheet resistance of 0.8 Ω/sq, superior visual Joule heating temperatures up to 108 °C at low supplied voltage of 2.0 V due to efficient energy conversion, excellent EMI shielding effectiveness (EMI SE) of ≈55 dB and outstanding piezoresistive sensing ability in human motion detection. This work demonstrates the fabrication of multifunctional AgNW/leather nanocomposites for next‐generation wearable electronic devices in energy conversion, electronic skin and artificial intelligence, etc.

Multifunctional Wearable Silver Nanowire Decorated Leather Nanocomposites for Joule Heating, Electromagnetic Interference Shielding and Piezoresistive Sensing.

Multifunctional wearable electronic devices based on natural materials are highly desirable for versatile applications of energy conversion, electronic skin and artificial intelligence. Herein, multifunctional wearable silver nanowire decorated leather (AgNW/leather) nanocomposites with hierarchical structures for integrated visual Joule heating, electromagnetic interference (EMI) shielding and piezoresistive sensing are fabricated via the facile vacuum-assisted filtration process. The AgNWs penetrate the micro-nanoporous structures in the corium side of leather constructing highly-efficient conductive networks. The resultant flexible and mechanically strong AgNW/leather nanocomposites exhibit extremely low sheet resistance of 0.8 Ω/sq, superior visual Joule heating temperatures up to 108 °C at low supplied voltage of 2.0 V due to efficient energy conversion, excellent EMI shielding effectiveness (EMI SE) of ≈55 dB and outstanding piezoresistive sensing ability in human motion detection. This work demonstrates the fabrication of multifunctional AgNW/leather nanocomposites for next-generation wearable electronic devices in energy conversion, electronic skin and artificial intelligence, etc.

Mechanically and environmentally robust composite nanofibers with embedded MXene for wearable shielding of electromagnetic wave

Flexible materials based on two-dimensional titanium carbides (MXene) exhibit great potential for electromagnetic interference (EMI) shielding applications. However, MXene base EMI shielding materials usually cannot possess combined favorable properties of high strength, environmental stability and air permeability, which can inhibit practical implementations as wearable components. Herein, newly designed EMI shielding Poly (vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP) composite fabric with MXene embedded in nanofibers have been prepared by one-step electrospinning technique. The highly hydrophobic composite fabric shows excellent specific EMI shielding effectiveness of 160 dB/mm, which remains unchanged when exposed in acidic, alkali or saline solutions for 10 days due to the polymer matrix protection. Moreover, the embedded MXene can greatly enhance the strength and modulus of the fabric. The ultimate strength of the highly flexible composite can reach as high as20 MPa, which is 33% higher compared with untreated PVDF-HFP fabric. Our study could allow us to implement MXene based EMI shielding materials for more practical applications.

Lightweight leaf-structured carbon nanotubes/graphene foam and the composites with polydimethylsiloxane for electromagnetic interference shielding

One of the key requirements for novel electromagnetic interference (EMI) shielding composites is lightweight. In this article, we report a kind of novel foam materials (labeled as CGF) with a leaf structure composed of carbon nanotubes (CNTs) and reduced graphene oxide (rGO) for EMI shielding. It was found that adding 20 wt% CNTs into the new material could expand the conductive network and increase the conductivity of CGF by 274.4%. Such an expansion could facilitate the multiple reflections and absorptions of EMWs within the materials and boost the conversion efficiency to induced currents (ICs), resulting in excellent total EMI shielding effectiveness (SE) of 71.4 dB at mass per unit area of only 12.5 mg·cm−2. Moreover, the CGF materials manifest exceptional EMI SE divided by density (SED) or mass per unit area (SEMA) value were 1142 dB·cm3·g−1 and 5712 dB·cm2·g−1, respectively. Considering the radar chart prepared by the total EMI SE, SED and SEMA, CGF reflects excellent comprehensive performance. Being compounded with polydimethylsiloxane (PDMS), the EMI SE of CGF/PDMS show excellent pressure resistance. After press CGF/PDMS for 100 times under a pressure of 500 kPa, the EMI SE retention rate can reach 71.6%. Furthermore, the addition of CGF increase the heat resistance indexes (THRI) of the composites by 6 °C. In conclusion, CGF/PDMS are extremely practical in the field of EMI shielding.

Superior Electromagnetic Shielding and Mechanical Buffering Achieved by Alternating Conductive and Porous Supramolecular Networks

The development of electromagnetic interference (EMI) shielding materials with excellent EMI shielding effectiveness (SE), and superior mechanical performance is of great importance in daily life and in the military, where they are used for intelligent transportation systems and ammunition. Generally, shielding performances can be realized via reflection loss and absorption loss. However, it is still a challenge to enhance these two kinds of electromagnetic wave loss in the same material at the same time to achieve ideal shielding performance. Herein, a flexible Ag NDs/CNT@PC/Ni‐9 film composed of five conductive layers and four porous layers is prepared by alternating Ag NDs/CNT layers and PC/Ni layers through self‐assembly. The obtained film with a thickness of 890 μm exhibits a remarkable SE performance of 138 dB in the X‐band. Additionally, with a series of continuous volcanic mechanical impacts (>10 000 g), the maximum instantaneous acceleration is decreased by 30.02% due to the buffering of the film, which constitutes a much‐improved energy absorption cushion relative to that of traditional buffering materials, such as foam metal and rubber. A material integrated with strong EMI shielding and high mechanical shock resistance is designed, which provides an effective strategy for the development of functional materials for extreme environments.

Leaf-structured Carbon Nanotubes/Graphene Aerogel and the Composites with Polydimethylsiloxane for Electromagnetic Interference Shielding

Lightweight is indispensable in the field of future electromagnetic interference (EMI) shielding. A low areal density three-dimensional leaf-structured carbon nanotubes (CNTs)/reduced graphene oxide (rGO) aerogel (noted as CGA) was prepared. In CGA, vein-structured CNTs expand conductive network of mesophyll-structured rGO, which promotes reflection and absorption of electromagnetic waves (EMWs) inside the materials, resulting in excellent EMI shielding effectiveness (SE) of 33.1 dB at the areal density of 2.27 mg·cm−2. EMI SE divided by areal density of the material was measured as 14581 dB·cm2·g−1. Furthermore, EMI SE of the composites prepared by three layers of CGA and polydimethylsiloxane (PDMS) was increased to 72.5 dB. The heat resistance index was increased by 10.29 °C compared with pure PDMS.

Lightweight and flexible PAN@PPy/MXene films with outstanding electromagnetic interference shielding and Joule heating performance.

Lightweight and flexible multifunctional materials with excellent electromagnetic interference (EMI) shielding and Joule heating performances are highly demanded for smart and wearable electronics. In this work, polyacrylonitrile (PAN) nanofiber films are prepared by electrospinning and then coated with polypyrrole (PPy) via vapor deposition, yielding a continuous three-dimensional (3D) conductive network of PAN@PPy. Ti3C2Tx MXene nanosheets with high electrical conductivity are sprayed on the PAN@PPy film to enhance its EMI shielding performance. The as-prepared PAN@PPy/MXene films (55 μm thick) exhibit a high EMI shielding effectiveness (SE) of 32 dB, achieving an extraordinarily high normalized surface-specific SE (SSE/t) of up to 17 534.5 dB cm2 g-1 from 8.2 to 12.4 GHz; simultaneously, the temperatures of PAN@PPy/MXene films can be driven up to 170.5 °C at an input voltage of 4 V, and exhibit fast-response, stable, and long-term Joule heating performance. The high SSE/t and efficient Joule heating ability of the films bode potential applications in smart and wearable devices.

CNT@PDMS/NW composite materials with superior electromagnetic shielding

Abstract Lightweight materials with high electrical conductivity and hydrophobic mechanical properties are ideal materials for electromagnetic interference (EMI) shielding. Herein, the conductive composites with great EMI shielding effectiveness (SE) were successfully obtained by introducing multi-walled carbon nanotube (CNT) and polydimethylsiloxane (PDMS) based on the original structure of natural wood (NW). CNT@PDMS/NW composites were prepared via vacuum-pulse impregnation method and characterized by Fourier transform infrared (FTIR), scanning electron microscope (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD) patterns, hydrophobicity analysis, and EMI shielding performance. As demonstrated, CNT nanosheets were successfully inserted into wood matrices, and hydrogen bonding between CNT nanosheets and cellulose nanofibers induced the fabrication of CNT@PDMS/NW composites. CNT@PDMS/NW composites exhibited excellent EMI SE values of 25.2 dB at the X-band frequency.

Carbonization of Graphene-Doped Isocyanate-Based Polyimide Foams to Achieve Carbon Foams with Excellent Electromagnetic Interference Shielding Performance.

Lightweight carbon foams with excellent electromagnetic interference (EMI) shielding performance were prepared by carbonization process, using isocyanate-based polyimide foams as carbon precursors. The influence of carbonization temperature and graphene-doping on the morphological, electrical and EMI shielding effectiveness (SE) of corresponding carbon foams was studied in detail. Results showed that the addition of graphene was beneficial to the improvement of electrical conductivity and EMI shielding performance of carbon foams. The electrical conductivity of carbon foams increased with the carbonization temperature which was related to the increase of graphitization degree. Collapse of foam cells was observed at higher carbonization temperatures, which was detrimental to the overall EMI SE. The optimal carbonization temperature was found at 1100 °C and the carbon foams obtained from 0.5 wt% graphene-doped foams exhibited a specific EMI SE of 2886 dB/(g/cm3), which shows potential applications in fields such as aerospace, aeronautics and electronics.

3D printing of free-standing Ti3C2Tx/PEO architecture for electromagnetic interference shielding

Recently, two-dimensional (2D) MXenes have emerged as filler materials for electromagnetic interference (EMI) shielding polymer composites due to their extraordinary electrical conductivity, high surface area, hydrophilic nature, and flexibility. Three-dimensional (3D) Printing with MXenes appears to be a new paradigm for manufacturing EMI shielding structures, where complex and specific 3D architecture is often required. In this study, composite inks incorporating 2D Ti3C2Tx MXenes with highly thixotropic properties were developed for the liquid deposition modeling (LDM) 3D Printing method. The use of these inks enabled the fabrication of semi-transparent EMI shielding 3D architectures. The 3D-Printed EMI shields exhibited excellent EMI shielding effectiveness (EMI SE), particularly in the X-band (∼231 dB/mm) and semi-transparency (54.61%) in the visible light range. Moreover, excellent thermal management capability with highly anisotropic thermal conductivity (anisotropic index: 3.6) was achieved through 3D Printing. It is anticipated that the approach developed in this study has potential for the fabrication of advanced EMI shielding architecture with good thermal management capability for various applications, for example, precision wireless communication devices using variable frequencies with multiple channels, autonomous driving vehicles, and the Internet of Things (IoT).

Metallic fusion of nanocrystal thin films for flexible and high-performance electromagnetic interference shielding materials

Low-cost flexible electromagnetic interference (EMI) shielding materials are attracting considerable attention because of the rapid development of wearable smart electronics, such as wearable health monitoring systems, and flexible energy storage and harvesting systems. In the present study, we developed ultrathin, flexible, and high-performance EMI shielding materials using Ag nanocrystals (NCs) through low-cost, room-temperature wet chemical processes conducted at atmospheric pressure. Sequential ligand-exchange and reduction processes not only substantially reduced the distance between the Ag NCs but also induced intensive metallic fusion of the Ag NCs, resulting in large-scale three-dimensional interconnected conductive pathways. The fused Ag NC thin films exhibited high electrical conductivity (∼24,000 S/cm for a film ∼800 nm thick) and outstanding mechanical stability, offering stable EMI shielding performance over 1000 cycles of various mechanical deformations, including twisting, crumpling, and folding. In addition, compared with most previously reported solution-based materials, our Ag NC thin films demonstrated an excellent EMI shielding effectiveness value of ∼60 dB in the X-band range 8.2–12.2 GHz at much thinner thickness (∼1.3 μm). With the advantages of easy processing, good mechanical flexibility, and high-performance EMI shielding, the fused NC thin films developed in the present work represent innovative potential EMI shielding materials for next-generation wearable smart electronics.

Ultrafine Cellulose Nanofiber-Assisted Physical and Chemical Cross-Linking of MXene Sheets for Electromagnetic Interference Shielding.

Transition metal carbides and nitrides (MXenes) have shown great potential for constructing thin, high-performance electromagnetic interference (EMI) shields. The challenges with these materials involve the weak interfacial interactions of MXenes, which results in inferior mechanical properties and structure of the MXene films and a conductivity/EMI shielding performance decay related to the poor MXene oxidation stability. Numerous efforts have been devoted to improving the mechanical properties or oxidation stability of the films, which always comes at the expense of EMI shielding performance. Here, ultrafine (≈1.4nm) cellulose nanofibers are employed to achieve physical and chemical dual cross-linking of MXene (PC-MXene) nanosheets. The procedure involves drying of flexible and highly conductive PC-MXene films at ambient pressure and is energy-efficient and scalable. Compared to the MXene films, the PC-MXene films show significantly improved mechanical strength, hydrophobicity, oxidation stability, and are waterproof, without compromising the excellent EMI shielding effectiveness (SE). Moreover, the freestanding PC-MXene films reach a thickness of merely 0.9µm and exhibit a high SE of 33.3dB, which cannot be achieved by pure MXene films. This leads to ultrahigh thickness-specific SE and surface-specific SE values of 37000dBmm-1 and 148000dBcm2 g-1 respectively, significantly surpassing those of previously reported MXene-based films.

Holocellulose nanofibrils assisted exfoliation to prepare MXene-based composite film with excellent electromagnetic interference shielding performance

A high-yield and straightforward method is proposed to obtain an electromagnetic interference (EMI) shielding film based on multilayered Ti3C2Tx (m-Ti3C2Tx). Holocellulose nanofibrils modified by sulfamic acid (SHCNF) with unique “core-shell” structure can act as a dispersant and a binder to assist in exfoliating m-Ti3C2Tx into delaminated-Ti3C2Tx (d-Ti3C2Tx) and fabricate flexible Ti3C2Tx/SHCNF composite films with a high-yield value. The “brick-and-mortar” composite films exhibit a superior electromagnetic interference (EMI) shielding effectiveness (SE) of 45.02 dB with an ultrathin thickness of 40 μm at the 12.4 GHz. Moreover, these flexible and strong integrated Ti3C2Tx/SHCNF composite films also display excellent specific EMI SE of SSE/t (4437 dB cm2 g−1) and high EMI shielding efficiency (99.996%). Therefore, the SHCNF-assisted method provides a cost-effective approach to fabricate a strong and flexible MXene-based nanocomposite films toward EMI shielding application.

Microwave-induced segregated composite network with MXene as interfacial solder for ultra-efficient electromagnetic interference shielding and anti-dripping

MXenes, a fast-growing family of two-dimensional (2D) materials, can offer an excellent electromagnetic interference (EMI) shielding performance because of ultra-high electrical conductivity, multi-layered structure, and abundant termination groups. In turn, as a result of the favorable interaction with electromagnetic wave, MXene might evoke an intense energy conversion from electromagnetic energy to thermal energy upon exposure to the microwave irradiation. Herein, for the first time, the microwave heating behavior of Ti3C2Tx caused by the strong electromagnetic wave absorption was investigated. Ti3C2Tx nanosheets were flocculation-assembled onto the surface of polypropylene (PP) and used as the “interfacial solder”, inducing a unique selective heating to construct a continuous and compact network in segregated Ti3C2Tx/PP composite under the optimal microwave field. The sintered composite possessed the ultrahigh EMI shielding effectiveness (EMI SE) of 75.12 ~ 78.85 dB over the X-band with an extremely low Ti3C2Tx loading of 1.138 vol%, superior to the vast majority of Ti3C2Tx-based polymer composites. In addition, the compact Ti3C2Tx frameworks also provided an excellent anti-dripping performance for composite even with 0.284 vol% Ti3C2Tx. Therefore, by fully utilizing the intrinsic response of MXene to electromagnetic wave, we developed a novel method for not only process molding but also structural/chemical decoration of MXene-based materials.