Comparative Investigation into the Electromagnetic Wave Shielding Effectiveness of Different Type Carbon-Based Fabrics

Different type carbon-based fabrics, namely woven or nonwoven fabric, were employed to investigate the electromagnetic wave shielding effectiveness of the fabrics in the wide operating frequency range, namely 0.4GHz to 40GHz. The surface and cross sectional morphologies of the fabrics, their electrical conductivities, and their electromagnetic wave shielding effectiveness were investigated. In the case of woven fabric, the value of the electrical conductivity was much different according to the measuring direction in the woven fabric. For the nonwoven fabric, however, this value was independent on the measuring direction. The shielding effectiveness of the woven fabric was above 20dB in the range of 0.04GHz to 4GHz and then it decreased to below 20dB in the range of 4GHz to 40GHz. In contrast, the shielding effectiveness of nonwoven fabric was above 40dB in the whole operating frequency range in this work. Based on these results, the dependence of the shielding effectiveness of the woven or nonwoven fabrics according to the operating frequency and the optimal shielding effectiveness material in the wide operating frequency range was suggested and discussed.

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Enhanced Electromagnetic Wave Shielding Effectiveness of Carbon-Based Nonwoven Fabrics by H2 Plasma Treatment

Key Engineering Materials ◽

10.4028/www.scientific.net/kem.834.120 ◽

2020 ◽

Vol 834 ◽

pp. 120-126

Author(s):

Hyun Ji Kim ◽

Sung Hoon Kim

Keyword(s):

Electromagnetic Wave ◽

Plasma Treatment ◽

Microwave Plasma ◽

Operating Frequency ◽

Shielding Effectiveness ◽

Frequency Range ◽

Cross Sectional ◽

Structure Variation ◽

Nonwoven Fabrics ◽

Operating Frequency Range

Electromagnetic wave shielding effectiveness of the nonwoven fabrics was measured in the wide operating frequency range, namely 0.4GHz to 20GHz. The shielding effectiveness of the nonwoven fabric was below 45dB in the range of 0.04GHz to 15GHz and then it increased to above 45dB in the range of 15GHz to 20GHz. To enhance the electromagnetic wave shielding effectiveness of the nonwoven fabrics, 3 minutes H2 plasma treatment of the nonwoven fabrics was carried out under the microwave plasma-enhanced chemical vapor deposition system. By H2 plasma treatment, the shielding effectiveness of the nonwoven fabrics was greatly enhanced in the whole operating frequency range. The surface electron conductivity of the nonwoven fabrics was also enhanced from 2.11×103 S/m to 3.02×103S/m by H2 plasma treatment. The surface and cross sectional morphologies of the nonwoven fabrics with or without H2 plasma treatment were investigated and compared with each other. Crystal structure variation of the nonwoven fabrics by H2 plasma treatment was also investigated. Based on these results, the cause for the enhancement of the shielding effectiveness of the nonwoven fabrics by H2 plasma treatment was suggested and discussed.

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Enhancement of Electromagnetic Wave Shielding Effectiveness of Carbon Fibers via Chemical Composition Transformation Using H2 Plasma Treatment

Nanomaterials ◽

10.3390/nano10081611 ◽

2020 ◽

Vol 10 (8) ◽

pp. 1611

Author(s):

Hyun-Ji Kim ◽

Gi-Hwan Kang ◽

Sung-Hoon Kim ◽

Sangmoon Park

Keyword(s):

Electromagnetic Wave ◽

Plasma Treatment ◽

Microwave Plasma ◽

Chemical Vapor ◽

Lower Surface ◽

Operating Frequency ◽

Shielding Effectiveness ◽

Frequency Range ◽

Operating Frequency Range ◽

Type C

H2 plasma treatment was performed on carbon-based nonwoven fabrics (c-NFs) in a 900 W microwave plasma-enhanced chemical vapor deposition system at 750 °C and 40 Torr. Consequently, the electromagnetic wave shielding effectiveness (SE) of the c-NFs was significantly enhanced across the operating frequency range of 0.04 to 20.0 GHz. We compared the electromagnetic wave SE of the H2 plasma-treated c-NFs samples with that of native c-NFs samples coated with nano-sized Ag particles. Despite having a lower surface electrical conductivity, H2 plasma-treated c-NFs samples exhibited a considerably higher electromagnetic wave SE than the Ag-coated c-NFs samples, across the relatively high operating frequency range of 7.0 to 20.0 GHz. The carbon component of H2 plasma-treated c-NFs samples increased significantly compared with the oxygen component. The H2 plasma treatment transformed the alcohol-type (C–O–H) compounds formed by carbon-oxygen bonds on the surface of the native c-NFs samples into ether-type (C–O–C) compounds. On the basis of these results, we proposed a mechanism to explain the electromagnetic wave SE enhancement observed in H2 plasma-treated c-NFs.

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