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

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.

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

Nanomaterials ◽  
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.

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

2019 ◽  
Vol 803 ◽  
pp. 81-87
Author(s):  
Hyun Ji Kim ◽  
Sung Hoon Kim
Keyword(s):  
Electromagnetic Wave ◽  
Nonwoven Fabric ◽  
Woven Fabric ◽  
Operating Frequency ◽  
Shielding Effectiveness ◽  
Frequency Range ◽  
Cross Sectional ◽  
Operating Frequency Range ◽  
Wide Operating ◽  
Carbon Based

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.

Extracting Maximum Power in the Presence of Internal Inductance of Electromagnetic Energy Harvesting Systems

2020 ◽  
Author(s):  
Yamini Sharma ◽  
Lei Zuo
Keyword(s):  
Energy Harvesting ◽  
Electromagnetic Energy ◽  
Maximum Power ◽  
Operating Frequency ◽  
Frequency Range ◽  
Low Frequencies ◽  
Internal Inductance ◽  
Piezoelectric Energy ◽  
Operating Frequency Range ◽  
Electromagnetic Energy Harvesting

Abstract In this paper, the effect of internal inductance of electromagnetic generators in the field of energy harvesting is discussed. Electromagnetic energy harvesters are typically operated at low frequencies. This results in the generator internal inductor impedance being significantly less than the generator internal resistance. However, at high frequencies, this inductance can no longer be ignored. Therefore, to maximize the harvested power, the internal inductance must be considered while designing the power electronics. This paper presents two methods to tackle this issue. The first method involves making use of a discrete capacitor which is able to reduce the inductance effect not just at resonant frequency but for the entire operating frequency range. The second method makes use of a concept similar to synchronized switching harvesting on inductors (SSHI) in piezoelectric energy harvesting. A capacitor and switch are added in the electromagnetic energy harvesting circuit to reduce the generator internal inductance effect. This method not only provides the benefit of performing well in the entire operating frequency range but also eliminates the need for precise maximum power tracking techniques, which further helps in reducing the circuit losses. Simulation results show a maximum power output increase of 56%.

PERFORMANCE ANALYSIS OF AN ENGINE MOUNT FEATURING ER FLUIDS AND PIEZOACTUATORS

1996 ◽  
Vol 10 (23n24) ◽  
pp. 3143-3157 ◽  
Author(s):  
S.H. CHOI ◽  
Y.T. CHOI ◽  
S.B. CHOI ◽  
C.C. CHEONG
Keyword(s):  
Electric Field ◽  
Frequency Domain ◽  
Control Technique ◽  
Operating Frequency ◽  
Frequency Range ◽  
Engine Mounts ◽  
Operating Frequency Range ◽  
Engine Mount ◽  
Er Fluids ◽  
Er Fluid

Conventional rubber mounts and various types of passive or semi-active hydraulic engine mounts for a passenger vehicle have their own functional aims on the limited frequency band in the broad engine operating frequency range. In order to achieve high system performance over all frequency ranges of the engine operation, a new type of engine mount featuring electro-rheological(ER) fluids and piezoactuators is proposed in this study. A mathematical model of the proposed engine mount is derived using the bond graph method which is inherently adequate to model the interconnected hydromechanical system. In the low frequency domain, the ER fluid is activated upon imposing an electric field for vibration isolation while the piezoactuator is activated in the high frequency domain. A neuro-control algorithm is utilized to determine control electric field for the ER fluid, and H∞ control technique is adopted for the piezoactuator Comparative works between the proposed and single-actuating(ER fluid only or piezoactuator only) engine mounts are undertaken by evaluating force transmissibility over a wide operating frequency range.

scholarly journals Electromagnetic Wave Shielding Effectiveness Based on Carbon Microcoil-Polyurethane Composites

2014 ◽  
Vol 2014 ◽  
pp. 1-6 ◽  
Author(s):  
Gi-Hwan Kang ◽  
Sung-Hoon Kim
Keyword(s):  
Electromagnetic Wave ◽  
Chemical Vapor Deposition ◽  
Layer Thickness ◽  
Vapor Deposition ◽  
Chemical Vapor ◽  
Shielding Effectiveness ◽  
Frequency Range ◽  
Thermal Chemical Vapor Deposition ◽  
Shielding Properties ◽  
Polyurethane Composites

Carbon microcoils (CMCs) were deposited onto Al2O3substrates using C2H2/H2as source gases and SF6as an incorporated additive gas in a thermal chemical vapor deposition system. CMC-polyurethane (PU) composites were obtained by dispersing the CMCs in the PU with a dimethylformamide additive. The electromagnetic wave shielding properties of the CMC-PU composites were examined in the frequency range of 0.25–1.5 GHz. The shielding effectiveness (SE) of the CMCs-PU systematically increases with increasing the content of CMCs and/or the layer thickness. Based on these results, the main SE mechanism for this work was suggested and discussed.

scholarly journals Гибридный металлополимер как потенциальная активная среда оптоакустического генератора

2022 ◽  
Vol 48 (3) ◽  
pp. 36
Author(s):  
Е.И. Гиршова ◽  
Е.П. Микитчук ◽  
А.В. Белоновский ◽  
К.М. Морозов
Keyword(s):  
Silver Nanoparticles ◽  
Active Medium ◽  
Hybrid Material ◽  
Volume Fraction ◽  
Silver Content ◽  
Thermodynamic Characteristics ◽  
Operating Frequency ◽  
Frequency Range ◽  
Volume Fractions ◽  
Operating Frequency Range

A hybrid material was studied, consisting of polydimethylsiloxane and silver nanoparticles distributed throughout its volume, its optical and thermodynamic characteristics were calculated for different volume fractions of silver content. It is theoretically shown that this material with a volume fraction of silver of about 30% can be used as an active medium for an optoacoustic transducer with an operating frequency range of about 10 MHz.

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