• Title/Summary/Keyword: electromagnetic wave absorption

Search Result 160, Processing Time 0.024 seconds

Electromagnetic Wave Absorbers Prepared with Alnico Magnets

  • Song Jae-Man;Kim Dong-Il;Choi Jeung-Hyun;Jeung Jae-Hyun
    • Journal of electromagnetic engineering and science
    • /
    • v.5 no.3
    • /
    • pp.117-121
    • /
    • 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.

Electromagnetic Wave Shield Characteristics of Thermal Sprayed Ferrite Coatings (자성 페라이트 용사피막의 전자파 차폐 특성)

  • 정태식;김태형;박경채
    • Journal of Welding and Joining
    • /
    • v.20 no.1
    • /
    • pp.76-82
    • /
    • 2002
  • In these days, many advanced nations have enforced import restrictions against things emitting electromagnetic wave which has report that it is so harmful. In general, electromagnetic wave is composed of electric wave and magnetic wave. The reflection of electromagnetic wave is mainly reflected by conductive materials and the magnetism loss is generated by magnetic ferrite. The magnetism loss of ferrite is separated by eddy current loss, residual magnetism loss and hysteresis loss. Thermal sprayed coating is intended to manufacture because of simple processes and high efficient electromagnetic wave shielding. The high efficient thermal sprayed coatings were made from the magnetic ferrite materials that characterizes absorption of electromagnetic wave, and the electric conductive materials that characterize emitting of electromagnetic wave. This study was manufactured thermal sprayed coatings to improve absorption-efficiency, and measured the electromagnetic wave shielding efficiency. As the experimental results, high electromagnetic wave shield efficiency was obtained at wave frequency 2GHz to thermal sprayed ferrite coatings manufactured by size distribution range of spray powders, $38~88\mu\textrm{m}$.

Characteristic of Electromagnetic Wave Shielding Coatings by Thermal Spray (용사에 의한 페라이트 자성재료 코팅의 .전자파 차폐특성)

  • 정태식;박경채
    • Proceedings of the KWS Conference
    • /
    • 2000.10a
    • /
    • pp.240-242
    • /
    • 2000
  • This study was investigated absorption properties of electromagnetic wave in thermal sprayed Sr-ferrite coatings. The experiment of this study was ; manufactured thermal spraying powder for improving absorption-efficiency, processed for increasing strength of thermal spray coatings, and measured the electromagnetic wave shielding efficiency. This study was obtained excellent absorption-efficiency by thermal sprayed Sr-ferrite coatings.

  • PDF

Electromagnetic Wave Absorption Properties in Fe-based Nanocrystalline P/M Sheets with Carbon Black and BaTiO3 Additives

  • Kim, Mi-Rae;Park, Won-Wook
    • Journal of Powder Materials
    • /
    • v.16 no.1
    • /
    • pp.33-36
    • /
    • 2009
  • In order to increase the magnetic loss for electromagnetic(EM) wave absorption, the soft magnetic $Fe_{73}Si_{16}B_7Nb_3Cu_1$(at%) alloy strip was used as the basic material in this study. The melt-spun strip was pulverized using an attrition mill, and the pulverized flake-shaped powder was crystallized at $540^{\circ}C$ for 1h to obtain the optimum grain size. The Fe-based powder was mixed with 2 wt% $BaTiO_3$, $0.3{\sim}0.6$ wt% carbon black, and polymer-based binders for the improvement of electromagnetic wave absorption properties. The mixture powders were tape-cast and dried to form the absorption sheets. After drying at $100^{\circ}C$ for 1h, the sheets of 0.5 mm in thickness were made by rolling at $60^{\circ}C$, and cut into toroidal shape to measure the absorption properties of samples. The characteristics including permittivity, permeability and power loss were measured using a Network Analyzer(N5230A). Consequently, the properties of electromagnetic wave absorber were improved with the addition of both $BaTiO_3$ and carbon black powder, which was caused by the increased dielectric loss of the additive powders.

Electromagnetic Wave Absorption Properties According to by Controling Ferrite Particle Size in Electromagnetic Wave Absorber of Sheet Type (Sheet형 전파흡수체에 있어 페라이트 입자 크기의 제어에 따른 전파흡수특성)

  • 김동일;김수정;옥승민;송재만
    • Proceedings of the Korea Electromagnetic Engineering Society Conference
    • /
    • 2002.11a
    • /
    • pp.319-323
    • /
    • 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 ㎓.

  • PDF

A Study on Composite EM Absorber's Absorption Characteristics Using Natural Lacquer by Binder (옻을 지지재로 사용한 복합형 전자파 흡수체의 흡수 특성에 관한 연구)

  • Choi, Dong-Han
    • Proceedings of the Korea Electromagnetic Engineering Society Conference
    • /
    • 2003.11a
    • /
    • pp.622-629
    • /
    • 2003
  • Generally, a silicone rubber and a chloride polyethylene(CPE) have been used for the development of high-performance composite EM(ElectroMagnetic) wave absorber. In this study, the EM wave absorption abilities for natural lacquer which is newly suggested in this study as a binder for composite EM wave absorber were investigated to develop an improved EM wave absorber In addition, MnZn ferrite composite EM wave absorber mixed with the natural lacquer were prepared and their absorption ability was also investigated. MnZn ferrite composite EM wave absorber which employs the natural lacquer as a binder showed an improved EM wave absorption characteristics in comparison with the conventional binder such as a silicone rubber and a chloride polyethylene(CPE). The matching frequency and the absorption ability of EM wave absorber mixed with natural lacquer can be controled the change of the thickness of them.

  • PDF

Electromagnetic Wave Absorption Behavior of a Fe-based Nanocrystalline Alloy mixed with a Ferrite Powder (Fe계 나노결정립 분말과 페라이트 복합체의 전자파 흡수특성)

  • Koo, S.K.;Lee, M.H.;Moon, B.G.;Song, Y.S.;Sohn, K.Y.;Park, W.W.
    • Journal of Powder Materials
    • /
    • v.15 no.4
    • /
    • pp.292-296
    • /
    • 2008
  • The electromagnetic (EM) wave absorption properties of the $Fe_{73}Si_{16}B_7Nb_3Cu_1$ nanocrystalline powder mixed with 5 to 20 vol% of Ni-Zn ferrites has been investigated in a frequency range from 100MHz to 10GHz. Amorphous ribbons prepared by a planar flow casting process were pulverized and milled after annealing at 425 for 1 hour. The powder was mixed with a ferrite powder at various volume ratios to tape-cast into a 1.0mm thick sheet. Results showed that the EM wave absorption sheet with Ni-Zn ferrite powder reduced complex permittivity due to low dielectric constant of ferrite compared with nanocrystalline powder, while that with 5 vol% of ferrite showed relatively higher imaginary part of permeability. The sheet mixed with 5 vol% ferrite powder showed the best electromagnetic wave absorption properties at high frequency ranges, which resulted from the increased imaginary part of permeability due to reduced eddy current.

A Study on Development of EM Wave Absorber Using TiO2 for Automotive Radar in Cars

  • Choi, Chang-Mook;Kim, Dong-Il
    • Journal of electromagnetic engineering and science
    • /
    • v.8 no.3
    • /
    • pp.110-113
    • /
    • 2008
  • In this paper, we designed and fabricated an electromagnetic(EM) wave absorber for automotive radar in cars using $TiO_2$ as a dielectric material and chlorinated polyethylene(CPE) as a binder. First of all, we confirmed that the optimum composition ratio of $TiO_2$ was about 70 wt.%. The complex relative permittivity of a sample containing $TiO_2$: CPE=70:30 wt.% was calculated from S-parameter. The EM wave absorption abilities were simulated for the EM wave absorbers of different thickness using the calculated relative permittivity, and the EM wave absorber was manufactured based on the simulated design. A comparison of simulated and measured results is in good agreement. Measurement shows that a 1.85 mm thick absorber has absorption ability higher than 20 dB in the frequency range of $76{\sim}77$ GHz for automotive radars.

A Study on the Electromagnetic Wave Absorption Properties by the Preparing Condition of NiCuZn Ferrite (NiCuZn 페라이트의 제조 조건에 따른 전자파흡수 특성에 관한 연구)

  • 이영구;박찬규;이문수
    • Proceedings of the Korea Electromagnetic Engineering Society Conference
    • /
    • 2001.11a
    • /
    • pp.304-309
    • /
    • 2001
  • With the development of electromagnetic communication technology and increased use of electromagnetic wave, the countermeasure of EMI(Electromagnetic Interference) becomes more important socially, and interest for the electromagnetic wave absorber has also increased. In this paper, we have studied characteristics of frequency dependency on complex permittivity and complex permeability according to the changes of composition rate and sintering temperature of NiCuZn ferrite also known as electromagnetic wave absorber and further looked into effect of electromagnetic wave absorption properties. From the measurement where the composition of Fe$_2$O$_3$ and ZnO of NiCuZn ferrite was fixed at 49 and 34 mol% respectively while composition of NiO and CuO has been varied at each test, we found out that initial permeability and permittivity were high and the absorbing ability of electromagnetic wave recorded best with loss tangent(${\mu}$r"/${\mu}$r′) displays more than 1 within the frequency band of 2MHz~9.5MHz when the composition ratio of NiO was ranged around 8.5~9.5 mol% and the sintering temperature was 1,080$^{\circ}C$.

  • PDF

Effect of Annealing Temperature on the Electromagnetic Wave Absorbing Properties of Nanocrystalline Soft-magnetic Alloy Powder (연자성 나노결정합금 분말의 열처리 온도에 의한 전자파 흡수 특성의 영향)

  • Hong, S.H.;Sohn, K.Y.;Park, W.W.;Moon, B.G.;Song, Y.S.
    • Journal of Powder Materials
    • /
    • v.15 no.1
    • /
    • pp.18-22
    • /
    • 2008
  • The electromagnetic (EM) wave absorption properties with a variation of crystallization annealing temperature have been investigated in a sheet-type absorber using the $Fe_{73}Si_{16}B_7Nb_3Cu_1$ alloy powder. With increasing the annealing temperature the complex permeability (${\mu}_r$), permittivity (${\varepsilon}_r$) and power absorption changed. The EM wave absorber shows the maximum permeability and permittivity after the annealing at $610^{\circ}C$ for 1 hour, and its calculated power absorption is above 80% of input power in the frequency range over 1.5 GHz.