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Materials ◽  
2021 ◽  
Vol 15 (1) ◽  
pp. 300
Author(s):  
Zhenming Sun ◽  
Hailong Shi ◽  
Xiaoshi Hu ◽  
Mufu Yan ◽  
Xiaojun Wang

In this study, we reported a laminated CNTs/Mg composite fabricated by spray-deposition and subsequent hot-press sintering, which realized simultaneous enhancement effects on strength and electromagnetic interference (EMI) shielding effectiveness (SE) by the introduced CNTs and CNT induced laminated ‘Mg-CNT-Mg’ structure. It was found that the CNTs/Mg composite with 0.5 wt.% CNTs not only exhibited excellent strength-toughness combination but also achieved a high EMI SE of 58 dB. The CNTs increased the strength of the composites mainly by the thermal expansion mismatch strengthening and blocking dislocation movements. As for toughness enhancement, CNTs induced laminated structure redistributes the local strain effectively and alleviates the strain localization during the deformation process. Moreover, it could also hinder the crack propagation and cause crack deflection, which resulted in an increment of the required energy for the failure of CNTs/Mg composites. Surprisingly, because of the laminated structure induced by introducing CNTs, the composite also exhibited an outperforming EMI SE in the X band (8.2–12.4 GHz). The strong interactions between the laminated ‘Mg-CNT-Mg’ structure and the incident electromagnetic waves are responsible for the increased absorption of the electromagnetic radiation. The lightweight CNTs/Mg composite with outstanding mechanical properties and simultaneously increased EMI performance could be employed as shell materials for electronic packaging components or electromagnetic absorbers.


2021 ◽  
pp. 095400832110645
Author(s):  
Karim Benzaoui ◽  
Achour Ales ◽  
Ahmed Mekki ◽  
Abdelhalim Zaoui ◽  
Boudjemaa Bouaouina ◽  
...  

The conventional electromagnetic interference (EMI) shielding materials are being gradually replaced by a new generation of supported conducting polymer composites (CPC) films due to their many advantages. This work presents a contribution on the effects of silane surface–modified flexible polypyrrole-silver nanocomposite films on the electromagnetic interference shielding effectiveness (EMI-SE). Thus, the UV-polymerization was used to in-situ deposit the PPy-Ag on the biaxial oriented polyethylene terephthalate (BOPET) flexible substrates whose surfaces were treated by 3-aminopropyltrimethoxysilane (APTMS). X-ray Photoelectron Spectroscopy (XPS) analyzes confirmed the APTMS grafting procedure. Structural, morphological, thermal, and electrical characteristics of the prepared films were correlated to the effect of substrate surface treatment. Thereafter, EMI-SE measurements of the elaborated films were carried out as per ASTM D4935 standard for a wide frequency band extending from 50 MHz to 18 GHz. The obtained results confirmed that the APTMS-treated BOPET film exhibit higher EMI shielding performance and better electrical characteristics compared to the untreated film. In fact, a 32% enhancement of EMI-SE was noted for the treated films compared to the untreated ones. Overall, these results put forward the role played by the surface treatment in strengthening the position of flexible PPy-Ag supported films as high-performance materials in electronic devices and electromagnetic interference shielding applications.


Nanomaterials ◽  
2021 ◽  
Vol 12 (1) ◽  
pp. 20
Author(s):  
Zhen Miao ◽  
Xiaohong Chen ◽  
Honglei Zhou ◽  
Ping Liu ◽  
Shaoli Fu ◽  
...  

A unique self-standing membrane composed of hierarchical thermoplastic polyurethane (TPU)/polyacrylonitrile (PAN) fibers is prepared by the electrospinning technique, followed by a simple dip-coating process. Fe3O4 nanoparticles are uniformly anchored on TPU/PAN fibers during the electrospinning process, enabling the membrane to achieve effective electromagnetic interference shielding (EMI SE) performance. Such a hybrid membrane has a high magnetization of 18.9 emu/g. When MXene (Ti3C2Tx) layers are further loaded on the TPU/PAN/Fe3O4NPs hybrid membrane, its EMI SE performance in the X band can exceed 30 dB due to the hydrogen bonds generated between the macromolecular chain of PAN and the functional group (Tx) on the surface of MXene. Simultaneously, the interfacial attraction between MXene and the TPU/PAN/Fe3O4NPs substrate is enhanced. The EMI SE mechanism of the hybrid membrane indicates that this film has great potential in the fields of wearable devices and flexible materials.


Materials ◽  
2021 ◽  
Vol 14 (24) ◽  
pp. 7551
Author(s):  
Hui Jing ◽  
Zongnan Miao ◽  
Zhong Zeng ◽  
Hui Liu ◽  
Shengtai Zhou ◽  
...  

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.


2021 ◽  
pp. 002199832110526
Author(s):  
Hafiz Shehbaz Ahmad ◽  
Tanveer Hussain ◽  
Yasir Nawab ◽  
Shuaib Salamat

Tremendous development in electronic devices and their indiscriminate use has created a severe problem of electromagnetic pollution. Different types of electromagnetic interference (EMI) shielding materials and structures are used to protect electronic devices from the harmful effect of electromagnetic pollution. A present study was conducted to compare the effect of dielectric and magnetic nanofillers on electromagnetic shielding effectiveness (EMI SE) of carbon fiber reinforced composite structures (CFRC). Composites structures were developed using different dielectric and magnetic nanofillers. Effect of nanofillers on microwave absorption properties and reduction in electromagnetic pollution was investigated. Relationship between electrical conductivity and EMI shielding effectiveness in L, S, C, and X-frequency range was also studied. Among the dielectric nanofillers, silicon carbide showed excellent EMI SE in X-frequency range, while among magnetic nanofillers, zinc oxide showed excellent EMI shielding characteristics in a broad frequency range of 100 MHz to 13.6 GHz. Among magnetic nanofillers, CFRC with zinc oxide nanofillers showed the lowest skin depth value of 3.32 × 10−4 mm and among dielectric nanofiller, CFRC with silicon carbide nanofillers gave the lowest skin depth value of 6.49 × 10−4 mm, implying their excellent potential in EMI shielding applications.


Polymers ◽  
2021 ◽  
Vol 13 (19) ◽  
pp. 3277
Author(s):  
Jian Wang ◽  
Baohua Liu ◽  
Yu Cheng ◽  
Zhenwan Ma ◽  
Yanhu Zhan ◽  
...  

A flexible, wearable electronic device composed of magnetic iron oxide (Fe3O4)/reduced graphene oxide/natural rubber (MGNR) composites with a segregated network was prepared by electrostatic self-assembly, latex mixing, and in situ reduction. The segregated network offers the composites higher electrical conductivity and more reliable sensing properties. Moreover, the addi-tion of Fe3O4 provides the composites with better electromagnetic interference shielding effectiveness (EMI SE). The EMI shielding property of MGNR composites is more stable under tensile deformation and long-term cycling conditions and has a higher sensitivity to stretch strain compared with the same structure made from reduced graphene oxide/natural rubber (GNR) composites. The EMI SE value of MGNR composites reduces by no more than 2.9% under different tensile permanent deformation, cyclic stretching, and cyclic bending conditions, while that of GNR composites reduces by approximately 16% in the worst case. Additionally, the MGNR composites have a better sensing performance and can maintain stable signals, even in the case of cyclic stretching with a very small strain (0.05%). Furthermore, they can steadily monitor the changes in resistance signals in various human motions such as finger bending, wrist bending, speaking, smiling, and blinking, indicating that the MGNR composites can be used in future wearable electronic flexibility devices.


Author(s):  
Jiaxuan Huang ◽  
Hujie Wan ◽  
Mian Li ◽  
Yiming Zhang ◽  
Jianfeng Zhu ◽  
...  

AbstractElectromagnetic interference (EMI) shielding materials have received considerable attention in recent years. The EMI shielding effectiveness (SE) of materials depends on not only their composition but also their microstructures. Among various microstructure prototypes, porous structures provide the advantages of low density and high terahertz wave absorption. In this study, by using carbonised wood (CW) as a template, 1-mm-thick MAX@CW composites (Ti2AlC@CW, V2AlC@CW, and Cr2AlC@CW) with a porous structure were fabricated through the molten salt method. The MAX@CW composites led to the formation of a conductive network and multilayer interface, which resulted in improved EMI SE. The average EMI SE values of the three MAX@CW composites were > 45 dB in the frequency of 0.6–1.6 THz. Among the composites, V2AlC@CW exhibited the highest average EMI SE of 55 dB.


2021 ◽  
pp. 2151041
Author(s):  
Wei Wang ◽  
Xiaoyu Bing ◽  
Yutong Zhou ◽  
Miaomiao Geng ◽  
Yanhu Zhan ◽  
...  

The structural design of thin films is attracting attention in academia and industry in attempts to improve electromagnetic interference shielding effectiveness (EMI SE). In this study, MXene/chitosan/silver nanowire (AgNW) sandwich films, in which the AgNW core layer was bordered by two MXene/chitosan layers, were fabricated by vacuum-assisted filtration. Because of the interconnected AgNWs in the core layer and the aligned MXene sheets in the MXene/chitosan layers, the electrical conductivity of the sandwich film reached 11,459.1 S/m. Consequently, the sandwich film exhibited an SE value of 82.3 dB. What is more, when both the AgNW and MXene contents were 33.3%, the sandwich film’s EMI SE divided by its thickness was 26,167 dB/cm, which was much superior to the values reported for inorganic hybrid composites and polymer composites filled with hybrid fillers. Such a simple approach was proved to be an effective way for further structure design of thin films in EMI shielding field.


Polymers ◽  
2021 ◽  
Vol 13 (16) ◽  
pp. 2753
Author(s):  
Maria Kosarli ◽  
Anastasia Polymerou ◽  
Georgios Foteinidis ◽  
Christos Vazouras ◽  
Alkiviadis S. Paipetis

In this study, the effect of the addition of multi-walled carbon nanotubes (MWCNTs), at three percentages, into the urea-formaldehyde (UF) shell-wall of microcapsules on the healing efficiency is reported. The modified shell-wall created a conductive network in semi-conductive epoxies, which led to an improvement of the electromagnetic interference shielding effectiveness (EMI SE); utilizing the excellent electrical properties of the CNTs. The microcapsule’s mean diameter and shell wall were examined via scanning electron microscopy (SEM). Thermal stability was evaluated via thermogravimetric analysis (TGA). The healing efficiency was assessed in terms of fracture toughness, while the electrical properties were measured using impedance spectroscopy. The measurements of the EMI SE were carried out in the frequency range of 7–9 GHz. The derived results indicated that the incorporation of the CNTs resulted in a decrease in the mean size of the microcapsules, while the thermal stability remained unchanged. In particular, the introduction of 0.5% w/v CNTs did not affect the healing efficiency, while it increased the initial mechanical properties of the epoxy after the incorporation of the self-healing system by 27%. At the same time, it led to the formation of a conductive network, providing electrical conductivity to the epoxies. The experimental results showed that the SE increased on average 5 dB or more after introducing conductive microcapsules.


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