Investigation of electromagnetic interference shielding effectiveness and electrical percolation of carbon nanotube polymer composites with various aspect ratios

Lee Dong-Kwan,Yoo Jongchan,Kim Hyunwoo,Park Sung-Hoon 한국탄소학회 2024 Carbon Letters Vol.34 No.1

Metals are recognized as electromagnetic interference (EMI) shielding materials owing to their high electrical conductivity. However, the need for light and flexible EMI shielding materials has emerged, owing to the heavyweight and inflexible nature of metals. Carbon nanotube (CNT)/polymer composites have been studied as promising flexible EMI shielding materials because of their lightweight nature due to the low density of CNTs and their high electrical conductivity. CNTs evenly dispersed in the polymer form an electrically conductive network, and the aspect ratio of the CNTs, which are one-dimensional nanofillers, is an important factor affecting electrical conductivity. In this study, we prepared three types of multi-walled carbon nanotubes (MWNTs) with different aspect ratios and fabricated polydimethylsiloxane (PDMS)/MWNT composites. Subsequently, the electrical conductivities and electrical percolation thresholds of the three PDMS/MWNT composites with different MWNT aspect ratios were measured to analyze the behavior of electrically conducting network formation according to the aspect ratio. Furthermore, the total EMI shielding effectiveness of each composite was determined to evaluate the effect of the MWNT aspect ratio on the EMI shielding. Reflection and absorption of electromagnetic wave were measured for the PDMS/MWNT composite with the largest aspect ratio to analyze the EMI shielding mechanism of the composite. Additionally, the effects of the MWNT content on the conductivity and EMI shielding performance were examined. The results provide valuable guidance for designing polymer MWNT composites with good electrical conductivity and EMI shielding performance under different aspect ratios of MWNTs.

Effect of nickel plating on EMI shielding effectiveness and tensile properties of polyacrylonitrile fibers

임윤지,백윤미,박수진 한국공업화학회 2018 한국공업화학회 연구논문 초록집 Vol.2018 No.0

In this study, highly conductive Ni/Cu-polyacrylonitrile (PAN) fibers were prepared by electroless nickel plating on Cu-PAN fibers. In addition, the electromagnetic interference (EMI) shielding properties of the Ni/Cu-PAN fibers were investigated by varying the nickel plating time. The surface morphology of the Ni/Cu-PAN fibers was observed with a scanning electron microscope (SEM) in order to determine its surface properties and the volume resistivity of the samples was measured by using a four-point probe electrical resistivity tester to evaluate its electric properties. The electromagnetic interference shielding effectiveness (EMI-SE) was tested by a EMI shielding analyzer. Tensile test of the Ni/Cu-PAN were conducted using a universal test machine (UTM). The EMI-SE of Ni/Cu-PAN fibers was much improved compared with that of the as-received CuS-PAN fibers.

Electrospun Magnetic Nanofiber as Multifunctional Flexible EMI-Shielding Layer and its Optimization on the Effectiveness

Yu, Jiwoo,Nam, Dae-Hyun,Lee, Young-Joo,Joo, Young-Chang The Korean Microelectronics and Packaging Society 2016 마이크로전자 및 패키징학회지 Vol.23 No.2

We developed a flexible and micro-thick electromagnetic interference (EMI) shielding nanofabric layer that also functions as a water resisting and heat sinking material. Electrospinning followed by a simple heat treatment process was carried on to produce the EMI-shielding Ni/C hybrid nanofibers. The ambient oxygen partial pressure ($pO_2$ = 0.1, 0.7, 1.3 Torr) applied during the heat treatment was varied in order to optimize the effectiveness of EMI-shielding by modifying the size and crystallinity of the magnetic Ni nanoparticles distributed throughout the C nanofibers. Permittivity and permeability of the nanofibers under the electromagnetic (EM) wave frequency range of 300 MHz~1 GHz were measured, which implied the EMI-shielding effectiveness (SE) optimization at $pO_2$ = 0.7 Torr during the heat treatment. The materials' heat diffusivity for both in-plane direction and vertical direction was measured to confirm the anisotropic thermal diffusivity that can effectively deliver and sink the local heat produced during device operations. Also, the nanofibers were aged at room temperature in oxygen ambient for water resisting function.

Synergistic effect of MWNT/fly ash incorporation on the EMI shielding/absorbing characteristics of cementitious materials

Nam, I.W.,Lee, H.K. Butterworth Scientific ; Elsevier Science Ltd 2016 Construction and Building Materials Vol.115 No.-

The present study aims to develop electromagnetic interference (EMI) shielding materials of which the EM wave shielding/absorbing capabilities were enhanced by a synergistic effect of multi-wall carbon nanotube (MWNT) and fly ash (FA) in terms of EM characteristics. The MWNT/FA-added cementitious materials were fabricated with various content ratios of FA and silica fume (SF). SF was incorporated as a dispersion agent of MWNT and EMI shielding effectiveness (SE) of the cementitious materials was assessed in an effort to determine optimum content ratios of FA and SF. The best EMI SE was achieved by the specimen comprised of MWNT 0.6%, SF 20%, and FA 75% (C-FA75-SF20) as exhibiting -8.0~-57.1dB at a frequency range from 1 to 18GHz, indicating a synergistic effect of MWNT and FA. The superior EMI SE of the C-FA75-SF20 was assessed by three different tests, i.e., SEM observation, energy-dispersive X-ray spectroscopy analysis, and electrical & electromagnetic properties evaluation. Furthermore, a computational simulation work demonstrated that the experimental EMI SE results of the C-FA75-SF20 correspond to the simulation results.

Simulation and design of EMI shielding performance of smart adhesives for mobile applications

김상우 한국공업화학회 2015 한국공업화학회 연구논문 초록집 Vol.2015 No.0

Recently, the widespread use of mobile devices and wireless networks has created a hostile electromagnetic environment for integrated circuits (ICs) and even the human body. The electromagnetic radiation from ICs with very small feature sizes may induce undesirable electromagnetic coupling between data paths, which results in the unintentional electromagnetic field that can cause undesirable currents and various disturbances. Such disturbances can cause either temporary malfunctions or even permanent damage of the recently developed electronic devices that operate at hundreds of MHz with harmonic noise emissions in the GHz region. In particular, highly integrated electronic systems can result in very complex issues around radio frequency noise in the near-field magnetic field that cannot be removed with conventional shields and grounding techniques, because of the noise signal reflected from the highly conductive shields. In our study, we have investigated EMI shieding characteristics of smart adhesive materials for mobile applications by predicting and designing shielding performance through numerical analysis on a transmmision line in a predominantly magnetic field.

EMI shielding effectiveness and mechanical properties of MWCNTs-reinforced biodegradable epoxy matrix composites

Yoon-Ji Yim,Dong Chul Chung,Soo-Jin Park 한국탄소학회 2017 Carbon Letters Vol.22 No.-

Biodegradable epoxy (B-epoxy) was prepared from diglycidyl ether of bisphenol A and epoxidized linseed oil. The mechanical properties of B-epoxy composites reinforced with multi-walled carbon nanotubes (MWCNTs/B-epoxy) were examined by employing dynamic mechanical analysis, critical stress intensity factor (KIC) tests, and impact strength tests. The electromagnetic interference shielding effectiveness (EMI-SE) of the composites was evaluated using reflection and absorption methods. Mechanical properties of MWCNTs/B-epoxy were enhanced with an increase in the MWCNT content, whereas they deteriorated when the MWCNT content was >5 parts per hundred resin (phr). This can likely be attributed to the entanglement of MWCNTs with each other in the B-epoxy due to the presence of an excess amount of MWCNTs. The highest EMI-SE obtained was ~16 dB for the MWCNTs/B-epoxy composites with a MWCNT content of 13 phr at 1.4 GHz. The composites (13 phr) exhibited the minimum EMI-SE (90%) when used as shielding materials at 1.4 GHz. The EMI-SE of the MWCNTs/B-epoxy also increased with an increase in the MWCNT content, which is a key factor affecting the EMI-SE.

ITO/Ag/ITO 구조의 투명 전도성 전자파차폐 필름

김준동,이기범,이준식,홍준표,Malkeshkumar Patel 대한전기학회 2022 전기학회논문지 Vol.71 No.3

Electromagnetic wave shielding has been a huge issue in the aspect of device performance reliability and stability. Recently, human health concern is emerging as the increase the use of personal electronic devices, which arise the need of transparent interfaces which can transmit visible light to see the displays and invisibly block the harmful Electromagnetic wave. To realize both features, multi-functional film is required to ensure the visible transparency and the control of EM interference (EMI). Herein, the multi-functional EMI film was developed in the structure of multi-staking transparent conductor layers. Large-scale ITO-silver (Ag)-ITO composite film has the high optical transmittance (43%) and the excellent electrical conductivity (30000 S/cm). As a result the ITO/Ag/ITO film gives the significant EMI shielding effectiveness upto 40 dB, which is over the specification of commercials (20 dB). This transparent EMI-shielding film can invisibly endow the protection from the human electronics and interfaces, such as cell phones, displays, vehicles and residential buildings.

Electromagnetic interference shielding effectiveness of high-density polyethylene composites reinforced with multi-walled carbon nanotubes

Yim, Yoon-Ji,Park, Soo-Jin Elsevier 2015 Journal of industrial and engineering chemistry Vol.21 No.-

<P><B>Abstract</B></P> <P>The effect of multi-walled carbon nanotubes (MWCNTs) (1–18wt.%) on the electromagnetic interference shielding effectiveness (EMI-SE) of high-density polyethylene (HDPE) composites was investigated. The volume resistivity of the composites was tested using a four-point probe electrical resistivity tester. The EMI-SE of the composites was defined as the attenuation of the propagating electromagnetic waves produced. Our results indicated that the EMI-SE was enhanced with increase in the MWCNT content, which played a key factor in determining the EMI-SE. The highest EMI-SE of the composites was approximately 58dB for 18wt.% MWCNT/HDPE at 1.4GHz.</P> <P><B>Graphical abstract</B></P> <P>This shows the electromagnetic interference shielding effectiveness of MWCNT/HDPE composites as a function of MWCNT content at 1.4GHz.</P>

전장 시스템의 전자파 적합성 대응 기술

신영산,이성수,Shin, Youngsan,Lee, Seongsoo 한국전기전자학회 2018 전기전자학회논문지 Vol.22 No.2

최근 전장 시스템에서 부품의 개수와 주파수가 급증함에 따라 전자파에 의해 오동작이 발생하는 전자파 간섭(EMI: electromagnetic interference)이 자주 발생하고 있다. 본 논문에서는 EMI 필터, EMI 차폐 물질, 분산 스펙트럼 클록 등 다양한 전자파 적합성(EMC: electromagnetic compatibility) 대응 기술을 살펴보고 각 기술의 장단점에 대해 설명한다. Recently, number of components and operation frequency rapidly increase in automotive systems. This often leads to EMI (electromagnetic interference) where automotive systems suffer from malfunctions induced by electromagnetic wave. This paper surveys various EMC (electromagnetic compatibility) compliance technologies such as EMI filter, EMI shielding materials, and spread spectrum clock generator. Their pros and cons are also explained.

Recent advancement of electromagnetic interference (EMI) shielding of two Dimensional (2D) MXene and graphene aerogel composites

오수빈,김진수 한국공업화학회 2020 한국공업화학회 연구논문 초록집 Vol.2020 No.-

The two Dimensional (2D) materials such as MXene and graphene, are most promising materials, as they have attractive properties and attract numerous application areas like sensors, supper capacitors, displays, wearable devices, batteries, and Electromagnetic Interference (EMI) shielding. The proliferation of wireless communication and smart electronic systems urge the world to develop light wt., flexible, cost effective EMI shielding materials.