• Proceedings of the Korean Society of Precision Engineering Conference
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• 2004.10a
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• pp.1331-1334
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• 2004

The research on electromagnetic shielding has been advanced for military applications as well as for commercial products. Utilizing the reflective properties and absorptive properties of shielding material, the replied signal measured at the rear surface or at the signal source can be minimized. The shielding effect was obtained from materials having special absorptive properties or from structural characteristics such as stacking sequence. Recently researchers studied the electromagnetic properties of nano size particles. In this research {glass fiber}/{epoxy}/{nano particle} composites(GFR-Nano composites), was fabricated using various nano particles, and their properties in electromagnetic shielding were compared. For the visual observation of the nano composite materials, SEM(Scanning Electron Microscope) and TEM(Transmission Electron Microscope) were used. For the measurement of electromagnetic shielding, HP8719ES S-parameter Vector Network Analyser System was used on the frequency range of 8 GHz～12GHz. Among the nano particles, carbon black and Multi-Walled Carbon Nano-Tube (MWCNT) revealed outstanding electromagnetic shielding. Although silver nano particles (flake and powder) were expected to have effective electromagnetic shielding due to their excellent electric conductivities, test showed little shielding effect.

• Journal of the Korean Society for Precision Engineering
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• v.22 no.10 s.175
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• pp.121-128
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• 2005

The research on electromagnetic shielding has been advanced for military applications as well as for commercial products. Utilizing the reflective properties and absorptive properties of shielding material, the replied signal measured at the rear surface or at the signal source can be minimized. The shielding effect was obtained from materials having special absorptive properties and structural characteristics such as stacking sequence. Recently researchers studied the electromagnetic properties of nano size particles. In this research {glass fiber}/{epoxy}/{nano particle} composites(GFR-Nano composites) was fabricated using various nano particles, and their properties in electromagnetic shielding were compared. For the visual observation of the nano composite materials, SEM(Scanning Electron Microscope) and TEM(Transmission Electron Microscope) were used. For the measurement of electromagnetic shielding, HP8719ES S-parameter Vector Network Analyser System was used on the frequency range of 8 GHz${\~}$12GHz. Among the nano particles, carbon black and Multi-Walled Carbon Nano-Tube (MWCNT) revealed outstanding electromagnetic shielding. Although silver nano particles (flake and powder) were expected to have effective electromagnetic shielding due to their excellent electric conductivities, test results showed little shielding characteristics.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2000.05b
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• pp.149-154
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• 2000

In this paper, we studied the relation between addition of carbon and electromagnetic wave absorbing properties of ferrite-rubber composite. The ratio of carbon was 7 wt%. As s result, it has been shown that the electromagnetic wave absorbing properties of ferrite-rubber composite are changed by the addition of carbon in composite. And, we can control electromagnetic wave absorbing properties of ferrite-rubber composite by the using of carbon.

• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2006.09b
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• pp.1239-1240
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• 2006

Effects of $Ag_2O$ doping on the electromagnetic properties in the BiSrCaCuO superconductors. The electromagnetic properties of $Ag_2O$ doped and undoped BiSrCaCuO superconductor were evaluated to investigate the contribution of the pinning centers to the magnetic effect. It was confirmed experimentally that a large amount of magnetic flux was trapped in the $Ag_2O$ doped sample than that in the undoped one, indicating that the pinning centers of magnetic flux are related closely to the occurrence of the magnetic effect. It is considered that the area where normal conduction takes place increases by adding $Ag_2O$ and the magnetic flux penetrating through the sample increases. The results suggested that Ag acts to increase pinning centers of magnetic flux, contributing to the occurrence of the electromagnetic properties.

• Journal of Electrical Engineering and Technology
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• v.2 no.1
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• pp.102-105
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• 2007

Effects of $Ag_2O$ doping on the electromagnetic properties in the BiSrCaCuO superconductors. The electromagnetic properties of the $Ag_2O$ doped and undoped BiSrCaCuO superconductor were evaluated to investigate the contribution of the pinning centers to the magnetic effect. It was confirmed experimentally that a large amount of magnetic flux was trapped in the $Ag_2O$ doped sample than that in the undoped one, indicating that the pinning centers of magnetic flux are related closely to the occurrence of the magnetic effect. It is considered that the area where normal conduction takes place increases by adding $Ag_2O$ and the magnetic flux penetrating through the sample increases. The results suggested that Ag acts to increase the pinning centers of the magnetic flux, contributing to the occurrence of the electromagnetic properties.

• Journal of electromagnetic engineering and science
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• v.5 no.3
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• pp.117-121
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• 2005

We compared electromagnetic(EM) wave absorption properties between Alnico magnet (A) and (B) with different magnetic properties. Also, we investigated the effect of carbon, thickness of absorbers, and Alnico contents on EM wave absorption, and clarified the relation between Alnico content and central frequency.

• Proceedings of the Korea Electromagnetic Engineering Society Conference
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• 2002.11a
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• pp.319-323
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• 2002

Electromagnetic wave absorbers with the shape of sheet have been fabricated and their absorption properties are measured. The fabricated ferrite absorbers have different particle sizes and the absorbtion property is increased with decreasing the size of particle in a certain frequency range of 2.4∼3.2 ㎓.

• Journal of Magnetics
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• v.21 no.1
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• pp.61-64
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• 2016

In this study, we report the as-prepared MgO-doped $BaFe_{12}O_{19}$, which was prepared by calcination technique and high-energy ball milling process, as an electromagnetic wave absorber. The phase analysis of $BaFe_{12}O_{19}$ and the as-prepared MgO-doped $BaFe_{12}O_{19}$ was detected utilizing X-ray Diffractometer (XRD). The microstructure was characterized using Scanning Electron Microscope (SEM). By means of the transmission/reflection coaxial line method, the electromagnetic properties and microwave absorbing properties of the as-prepared electromagnetic wave absorber were studied. It is found that the electromagnetic wave absorber has a minimum reflection loss value of -41 dB at 4.27 GHz with a matching thickness of 2.6 mm. The experiment results revealed that the as-prepared electromagnetic wave absorber could find potential applications in many military as well as commercial industries.

• Journal of Korea Foundry Society
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• v.22 no.3
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• pp.130-136
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• 2002

The growing use of aluminum for castings over the past decade has brought with it the increased scrutiny of component properties. One area that has received much attention is the effect of in inclusions - or impurities particles held in the metal - on casting properties. A new method of electromagnetic separation for removal of inclusions in aluminum alloy melts is proposed. The principle is that as the electromagnetic force induced in metal acts on inclusions due to low electric conductivity, they are moved to the direction opposite to electromagnetic force and can be separated and removed from the melt. Experiments were carried out on A356 melt mixed alumina particles and commercial Al alloys of ADC 10 and 12. In the experiment using A356, it was proved that $Al_2O_3$ particles was separated and removed continuously from matrix melt by electromagnetic force. Based on these results, the continuous separation experiment that used ADC 10, 12 was carried and the cleanliness of melt was assessed by the amount of porosity, hydrogen contents, PoDFA and mechanical properties through tensile test. As the results of analyses, the amount of porosity and hydrogen contents decreased without variation of chemical composition in the specimen that passed the electromagnetic continuous separator. In addition, tensile strength and elongation of this specimen increased by $20{\sim}30%$ because of reduction of inclusions.

• Corrosion Science and Technology
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• v.9 no.4
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• pp.153-158
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• 2010

Electrical appliances such as audiovisual equipment and personal computers have recently had heat and electromagnetic problems. In order to solve those problems, 'High heat absorbing pre-painted steel sheet (hereinafter referred to as PSS)', 'High electromagnetic shielding PSS' and 'High heat absorbing and high electromagnetic shielding PSS' have been developed. In this paper, the heat characteristics and electromagnetic shielding properties of PSS are investigated by methods that use enclosures and their mechanisms are discussed. It was found that 'High heat absorbing PSS' and 'High heat absorbing and high electromagnetic shielding PSS'could reduce the heat problem. The mechanism of the heat characteristics was presumed for the high heat absorptivity of the back coating inside the enclosure. And it was also found that 'High electromagnetic shielding PSS' and 'High heat absorbing and high electromagnetic shielding PSS' could shield electromagnetic waves well. The mechanism of the electromagnetic shielding properties was considered for the low transfer impedance of the back coating inside the enclosure. 'High heat absorbing PSS' and 'High electromagnetic shielding PSS' have been adopted as materials for electrical appliances and 'High electromagnetic shielding and high heat absorbing PSS' have been tested for that purpose.