• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.19 no.2
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• pp.59-65
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• 2019

The EMI shielding effectiveness of shielding layers thickness was analyzed when the low conductivity shielding layers was placed in the near field of the noise source. A spiral antenna with broadband characteristics was used as the noise source, and graphite was selected as the low conductivity shielding material. Two spiral antennas were constructed to analyze the transmission coefficient between two antennas, and the distances between the transmitting and receiving antennas were 5 cm and 10 cm. The thickness of the shielding layers was changed from 1 um to 200 um. The frequency was changed from 100 MHz to 6 GHz to obtain a maximum SE(Shielding Effectiveness) of 70 dB. In this simulation, electronic shielding was used due to the nature of graphite, which is a shielding film material. Based on these results, we will study how to improve the shielding performance by implementing magnetic shielding in the future.

• Composites Research
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• v.19 no.3
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• pp.1-6
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• 2006

As the structures of the high performance electronic equipments and devices recently become more complex, the electromagnetic interference (EMI) and compatibility (EMC) have been very essential for commercial and military purposes. Thus, sensitive electrical devices and densely packed systems need to be protected from electromagnetic wave. In this research, glass fabric/epoxy composites containing conductive multi-walled carbon nanotube (MWNT) and carbon fiber/epoxy composites as electrical shielding materials were fabricated and electrical properties of the composites were measured. The concerning frequency band is from 300 MHz to 1 GHz. The performances of composite shielding enclosures were predicted using electromagnetic wave 3-D simulation tool, CST Microwave Studio. The shielding enclosure made of carbon fiber/epoxy composites were fabricated and the shielding effectiveness (SE) was measured in the anechoic chamber.

• Proceedings of the Korean Society For Composite Materials Conference
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• 2003.10a
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• pp.107-110
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• 2003

The electromagnetic intereference(EMI) shielding is very essential for commercial and military purposes. We fabricated multi-walled carbon nanoube(MWNT)/epoxy composites and studied the electromagnetic characteristics of the composites before we study the characteristics of MWNT-filled glass fiber-reinforced composites. After setting up the fabrication process, we measured the permittivities of MWNT/epoxy composites with process variables and MWNT concentrations in X-band(8.2GHz- 12.4GHz). Process variables changed the degree of dispersion, which influenced permittivities and permittivities increased rapidly from 0.5wt% to 1.0wt%.

• Applied Chemistry for Engineering
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• v.30 no.2
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• pp.212-218
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• 2019

To investigate the effect of the oxyfluorination of carbon nanotubes (OF-CNTs) on electroless Ni deposition and electromagnetic interference shielding efficiency (EMI SE), CNTs were treated with a mixture of oxygen and fluorine gases and sequentially deposited with nickel. These samples were then manufactured into thin films on a polyimide film to evaluate their EMI SE. The surface chemical property of OF-CNTs was investigated by X-ray photoelectron spectroscopy. From the results of thermogravimetric and scanning electron microscopic analyses, it was found that both the amount of deposited Ni and the surface morphology changed depending on oxyfluorination. Moreover, the Ni-deposited CNTs pretreated with $O_2:F_2=1:9vol%$ exhibited the maximum EMI SE as approximately 19.4 dB at 1 GHz. These results were attributed to the formation of oxygen and fluorine functional groups on the surface of CNTs due to the oxyfluorination, and the functional groups enabled to deposit a suitable amount of Ni and improve the dispersion in the deposited solution.

• Composites Research
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• v.17 no.3
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• pp.38-44
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• 2004

The electromagnetic interference (EMI) shielding is very essential for commercial and military purposes. We fabricated multi-walled carbon nanotube (MWNT)/epoxy composites and studied the electromagnetic characteristics of the composites before we study the characteristics of MWNT-added glass fiber-reinforced composites. After setting up the fabrication process, we measured the permittivity of MWNT/epoxy composites with process variables and MWNT concentrations in X-band (8.2GHz~12.4GHz). We also observed re-aggregation phenomenon of MWNTs and investigated its effect on the permittivity. The permittivity of the composites was influenced by the degree of dispersion of MWNTs and increased almost linearly as MWNT concentration increases.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.7 no.4
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• pp.10-16
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• 2008

This study investigated electromagnetic interference(EMI) shielding effectiveness(SE) of the aluminum film, conductive fabric and nano carbon black carbon fiber reinforced composites. We fabricated carbon fiber reinforced composites filled with nano carbon black where they bonded aluminum film and conductive fabric. The measurements of SE were carried out frequency range from 300MHz to 1.5GHz. It is observed that the SE of the bonded aluminum film and conductive fabric composites is the frequency dependent, increase with the increase in filler nano carbon black content. The aluminum film bonded composites showed higher SE compared to that of carbon black and conductive fabric. The aluminum film bonded epoxy composite was shown to exhibit up to 80dB of SE. The result that aluminum film bonded composite can be used for the purpose of EMI shielding as well as for some microwave applications.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.11 no.6
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• pp.169-174
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• 2012

Electromagnetic interference(EMI) shielding effectiveness(SE) was investigated in of woven fabric made of epoxy/copper-nickel fabrics and nickel coated carbon fiber reinforced acrylonitrile-butadiene-styrene(ABS) composites. The coaxial transmission line method was used to measure the EMI shielding effectiveness of the composites. We designed and constructed a measuring system, consisting of a network analyzer and a device that plays the serves as a sample holder and at the same time as a transmission medium of the incident electromagnetic wave. The measurement of SE were carried out frequency range from 100MHz to 2GHz. It is observed that the SE of the composits is the frequency dependent increase with the increase in nickel coated carbon fibre volume fraction. The nickel coating with 20wt% ABS composite was shown to exhibit up to 60dB of SE. The result that nickel coated carbon fibre ABS composite can be used for the purpose of EMI shielding as well as for some microwave applications.

• Bulletin of the Korean Chemical Society
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• v.34 no.1
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• pp.99-106
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• 2013

Polyaniline-yttrium trioxide (PAni-$Y_2O_3$) composites were synthesized by the in-situ polymerization of aniline in the presence of $Y_2O_3$ The composite formation and structural changes in these composites were investigated by X-ray diffraction (XRD), Fourier transform infra red spectroscopy (FTIR), scanning electron microscopy (SEM) and high resolution transmission electron microscopy (HRTEM). The direct current (DC) electrical conductivity of the order of $0.51{\times}10^{-2}\;S\;cm^{-1}-0.283\;S\;cm^{-1}$ in the temperature range 300 K-473 K indicates semiconducting behavior of the composites. Room temperature AC conductivity and dielectric response of the composites were studied in the frequency range of 10 Hz to 1 MHz. The variation of AC conductivity with frequency obeyed the power law, which decreased with increasing weight percentage (wt %) of $Y_2O_3$. Studies on dielectric properties shows the relaxation contribution coupled by electrode polarization effect. The dielectric constant and dielectric loss in these composites depend on the content of $Y_2O_3$ with a percolation threshold at 20 wt % of $Y_2O_3$ in PAni. Electromagnetic interference shielding effectiveness (EMI SE) of the composites in the frequency range 100 Hz to 2 GHz was in the practically useful range of -12.2 dB to -17.2 dB. The observed electrical and shielding properties were attributed to the interaction of $Y_2O_3$ particles with the PAni molecular chains.

• Journal of electromagnetic engineering and science
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• v.9 no.2
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• pp.53-60
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• 2009

Remarkable developments in the electric and electronic industry have given people's daily life much more convenience and abundance. However, in electrical communication, or electric and electronic fields, making electrical and electronic devices more functional, more integrated, and faster have put electromagnetic interference(EMI) into more complex forms, and lots of problems such as interruption, malfunction, or interference by noise between electrical communication systems occurs every day. In this research, the electromagnetic compatibility(EMC) filter in the high powered breaker was designed and fabricated as a counter measure. The filter attenuated noise more than 20${\sim}$50 dB in the range of 10 MHz${\sim}$1.5 GHz. And, when the electric fast transient(EFT) of 4 kV in the level 4 of IEC 61000-4-4 was induced, it was soon suppressed to 600 V.

• Proceedings of the KIEE Conference
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• 1997.11a
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• pp.308-310
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• 1997

In this paper, to anlayze electromagnetic distribution, measure the variation of relative permittivity of Glass-epoxy substrate for Computer-main-board and Tenon substrate for handphone or PCS in the frequency range $100[MHz]{\sim}1[GHz]$, in room temperature. To measure relative permittivity, suggested the Microstripline method. As the frequency increase, the variation of relative permittivity of Glass-epoxy is bigger than Tefoln's. And simulate the electromagnetic distribution on the PCBs in the infinite region applying the open boundary condition with these results by Finite Element Method.