Porous and Ultra-Flexible Crosslinked MXene/Polyimide Composites for Multifunctional Electromagnetic Interference Shielding
Zhihui ZengNa WuJingjiang WeiYunfei YangTingting WuBin LiStefanie Beatrice HauserWeidong YangJiurong LiuShanyu Zhao
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Abstract Lightweight, ultra-flexible, and robust crosslinked transition metal carbide (Ti 3 C 2 MXene) coated polyimide (PI) (C-MXene@PI) porous composites are manufactured via a scalable dip-coating followed by chemical crosslinking approach. In addition to the hydrophobicity, anti-oxidation and extreme-temperature stability, efficient utilization of the intrinsic conductivity of MXene, the interfacial polarization between MXene and PI, and the micrometer-sized pores of the composite foams are achieved. Consequently, the composites show a satisfactory X-band electromagnetic interference (EMI) shielding effectiveness of 22.5 to 62.5 dB at a density of 28.7 to 48.7 mg cm −3 , leading to an excellent surface-specific SE of 21,317 dB cm 2 g −1 . Moreover, the composite foams exhibit excellent electrothermal performance as flexible heaters in terms of a prominent, rapid reproducible, and stable electrothermal effect at low voltages and superior heat performance and more uniform heat distribution compared with the commercial heaters composed of alloy plates. Furthermore, the composite foams are well attached on a human body to check their electromechanical sensing performance, demonstrating the sensitive and reliable detection of human motions as wearable sensors. The excellent EMI shielding performance and multifunctionalities, along with the facile and easy-to-scalable manufacturing techniques, imply promising perspectives of the porous C-MXene@PI composites in next-generation flexible electronics, aerospace, and smart devices.Flexible and wearable electromagnetic interference (EMI) shielding material is one of the current research focuses in the field of EMI shielding. In this work, for the first time, WS2-carbon fiber (WS2-CF) composites are synthesized by implanting WS2, which has a multiphase structure and a large number of defects, onto the surface of carbon fiber (CF) by using a simple one-step hydrothermal method, and are applied to protect electronic devices from EMI. It is found that the EMI shielding performance of WS2-CF is significantly improved, especially for those at S and C-bands. At 2 GHz, the EMI shielding efficiency could reach 36.0 dB at a typical thickness of 3.00 mm of the composite, which is much better than that of pure CF (25.5 dB). Besides paving a novel avenue to optimize the electromagnetic shielding performance of flexible and wearable CF-based EMI shielding materials, which have great potential in the practical application for EMI shielding, this work provides a new paradigm for the design and synthesis of EMI shielding materials which have a broad application prospect.
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Environmentally friendly materials that exhibit high-performance electromagnetic interference (EMI) shielding are extremely necessary. Herein, we fabricated ultrathin Ti3C2Tx (U-Ti3C2Tx) MXene nanosheets (NS) by atomic-layer tailoring the layer thickness of Ti3C2Tx MXene. The U-Ti3C2Tx NS composites with highly efficient EMI shielding effectiveness can reduce secondary reflection, demonstrating its environmentally friendly performance. The U-Ti3C2Tx NS composite with 80 wt% loading exhibits an EMI shielding effectiveness of 58.1 dB at a thickness of 1 mm. Shielding performance analysis of different layer thicknesses shows that electron transport has an important contribution to the EMI shielding performance. Furthermore, the polarization induced by defects and terminal atoms plays an important role in the EMI shielding performance. Based on the electromagnetic (EM) wave response mechanism, a novel approach to effectively tune the EMI attenuation and shielding effectiveness can be achieved by adjusting the local conductive network. These findings will offer an effective strategy for designing environmentally friendly 2D materials with high-performance EMI shielding.
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This paper presents a review summary of radiated emission and interference shielding methodologies currently describes in brief on Electromagnetic interference measurement system allow measurement and reducing of electromagnetic interference by using electromagnetic interference shielding effectiveness. To use shielding technique as a coaxial holder with uniform diameters that maintains 50 ohm impedance throughout the length of the device. The EMI tester was calibrated and the shielding effectiveness of common and new materials was determined through several experiments.
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Abstract A kind of pollution known as electromagnetic interference (EMI), which results from ubiquitous usage of various electronic communication and military radar equipment, has received increasing attention recently. However, it is still a big challenge to obtain good EMI shielding in transparent and/or curved surfaces. In this paper, a light, ultrathin, transparent, and flexible EMI shielding film based on woven silver nanowire (Ag‐NW) 3D networks is successfully prepared via a room‐temperature template production method. For transparent application scenario, Ag‐NWs with 91% transmittance in visible range show ≈27 dB shielding efficiency. This sample shows ≈27 dB shielding efficiency, although with a low density of Ag‐NWs (≈0.0168 mg cm −2 ), which implies that this material has a cost‐effectiveness. Moreover, total shielding as high as ≈40 dB is obtained by using thickened Ag‐NW grids. The EMI has not changed remarkedly after bended 1200 times, which indicates the as‐prepared flexible film has a relative stability of the EMI performance. Considering the facile production technology, this material can be readily applied in transparent EMI shielding.
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Abstract The densely packed electronic components in electronic devices emit electromagnetic (EM) radiations, and the interaction of the emitted EM radiations with external EM signals of neighboring components leads to device malfunctions and also creates health issues in human beings. Particularly, in aircraft, EM interference is a serious threat that leads to disastrous outcomes. The shielding of electronic components is an ideal way to reduce the pollution of electromagnetic interference (EMI). The mechanism of EMI shielding efficiency is discussed elaborately in this article. The factors associated with the EMI shielding of materials are discussed in detail. The EMI shielding by reflection and absorption are two possible routes to improve the shielding performance of the shielding materials. This article also highlights the EMI shielding mechanisms by reflection and absorption. However, the risk of secondary EM pollution is associated with the reflection of EM waves. This review also outlines the methods to improve the absorption‐based shielding performance of the materials. The significance of the microstructure of the shielding materials in enhancing the absorption‐dominant shielding efficiency is also presented with a detailed analysis. This helps to fabricate the absorption‐dominant EMI shielding materials with suitable microstructures. The EM loss is associated with the magnetic, dielectric, and conduction losses according to EM theory. Highlights This article highlights the recent progress in epoxy‐based EMI shielding materials. EMI shielding mechanisms by reflection and absorption are discussed elaborately. Reviewed the methods to improve the absorption‐based shielding performance in detail. Materials with EMI shielding efficiency greater than 30 dB are highly preferable.
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Increasingly serious electromagnetic wave pollution puts forward higher requirements for efficient and widely applicable electromagnetic interference (EMI) shielding materials. Herein, aristate sphere Ni@Carbon fibers were synthesized through an in-situ ultrasonic reduction method. The phase structure, morphology, magnetic, electrical conductivity and EMI shielding performances of the specimens were analyzed by various technologies. Experimental results revealed that the introduction of magnetic aristate sphere Ni endowed the carbon fibers with an outstanding EMI shielding effectiveness (SE) of 38.5 dB (99.9% attenuation) and specific shielding effectiveness (SSE/T) of 642 dB cm2/g. The advanced EMI shielding performances of aristate sphere Ni/Carbon fibers could originate from the synergistic effect of high electrical conductivity, well magnetic loss, and multiple electromagnetic reflection. Consequently, aristate sphere Ni@Carbon fibers would be an ideal candidate as light-weight, high-efficiency and widely applicable EMI shielding materials in electromagnetic shielding applications fields.
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Integrated circuits (IC) operate in increasingly complex environments in terms of electromagnetic compatibility (EMC). Over time, ICs have implemented certain features that enable higher performance. Among these features, it is worth mentioning the use of higher frequencies, which are often electromagnetic interferences (EMI) sources. In addition, the device size reduction makes it difficult to introduce some specific elements to avoid EMC problems. For this reason, using board-level shielding (BLS) solutions can solve many problems. One of the most widespread methods, shielding cabinets, is discussed in this paper. Shielding cabinets are a kind of metal box that encloses the IC and insulates it. It can enclose the EMI source as well. The objective of this paper is the characterization of different models of shielding cabinets up to 5 GHz. The cabinets are characterized through two experimental measurements and a group of simulations.
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Conducted electromagnetic interference
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With rapid development of 5G communication technologies, electromagnetic interference (EMI) shielding for electronic devices has become an urgent demand in recent years, where the development of corresponding EMI shielding materials against detrimental electromagnetic radiation plays an essential role. Meanwhile, the EMI shielding materials with high flexibility and functional integrity are highly demanded for emerging shielding applications. Hitherto, a variety of flexible EMI shielding materials with lightweight and multifunctionalities have been developed. In this review, we not only introduce the recent development of flexible EMI shielding materials, but also elaborate the EMI shielding mechanisms and the index for "green EMI shielding" performance. In addition, the construction strategies for sophisticated multifunctionalities of flexible shielding materials are summarized. Finally, we propose several possible research directions for flexible EMI shielding materials in near future, which could be inspirational to the fast-growing next-generation flexible electronic devices with reliable and multipurpose protections as offered by EMI shielding materials.
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Abstract The proliferation of electronic devices has made electromagnetic interference (EMI) shielding an exponentially growing business. Regulatory requirements change constantly as new technologies continue to emerge. Innovations in materials and new advances in shielding implementation techniques are needed to pass regulatory compliance tests at an affordable cost. Here, we print various EMI shielding materials such as copper, silver and a composite of copper with Fe 3 O 4 using plasma jet printing. Printing enables shields only a few microns thick capable of high shielding effectiveness. Copper’s EMI shielding performance is primarily contributed by reflection mechanism, as expected and this is known to cause secondary pollution. A Green Index for EMI shielding, given by the ratio of absorption and reflection contributions to shielding, indicates values lower than 0.1 for printed copper films.
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Due to substantial development of electronics and telecommunication techniques, materials with electromagnetic interference (EMI) shielding performance are significant in alleviating the interference impacts induced from a remarkable variety of devices. In the work, we propose novel sandwich structures for manipulating the EM wave transport, which holds unique EMI shielding features of frequency selectivity. By employing electrical and magnetic loss spacers, the resultant sandwich structures are endowed with tunable EMI shielding performance, showing substantial improvements in overall shielding effectiveness along with pronounced shielding peak shift. The mechanisms suggest that the multiple interfaces, electromagnetic loss media, and changes of representative EM wavelength could be critical roles in tailoring the EMI shielding performance. The results provide a versatile strategy that could be extended in other frequency ranges and various types of sandwich structures, promising great opportunities for designing and fabricating advanced electromagnetic attenuation materials and devices.
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