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Fe계 나노결정립 분말과 페라이트 복합체의 전자파 흡수특성
구숙경,이민혁,문병기,송용설,손근용,박원욱,Koo, S.K.,Lee, M.H.,Moon, B.G.,Song, Y.S.,Sohn, K.Y.,Park, W.W. 한국분말야금학회 2008 한국분말재료학회지 (KPMI) Vol.15 No.4
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.
Fe계 나노결정립 분말의 표면 산화에 따른 전자파 흡수특성
구숙경,우수정,문병기,송용설,박원욱,손근용,Koo, S.K.,Woo, S.J.,Moon, B.G.,Song, Y.S.,Park, W.W.,Sohn, K.Y. 한국분말야금학회 2007 한국분말재료학회지 (KPMI) Vol.14 No.5
The oxidation of $Fe_{73}Si_{16}B_7Nb_3Cu_1$ nanocrystalline powder has been conducted to investigate its influence on the electromagnetic wave absorption characteristics of the soft magnetic material. Oxidation occurred primarily on the surface of nanocrystals. Oxidation reduced the real part of complex permeability due to the reduction of the relative volume of the powder, which otherwise contributes to the permeability. Oxidation reduced the absorption efficiency of the sheet at frequencies over 1GHz, indicating that the relative contribution of skin depth increments to the absorption was not significant. The pulverization and milling process lowered the optimum crystallization temperature of the material by $40{\sim}50^{\circ}C$ because of the internal energy accumulated during the fragmentation and powder thinning processes.
연자성 합금 분말의 입자크기에 따른 전자파 흡수 특성 비교
홍순호,손근용,박원욱,남정미,문병기,송용설,Hong, S.H.,Sohn, K.Y.,Park, W.W.,Nam, J.M.,Moon, B.G.,Song, Y.S. 한국분말야금학회 2007 한국분말재료학회지 (KPMI) Vol.14 No.4
The electromagnetic wave (EM) absorption properties of various particle size have been investigated in a sheet-type absorber using the $Fe_{73}Si_{16}B_{7}Nb_{3}Cu_{1}$ alloy powder. With decreasing the average particle size, the complex permeability (${\mu}_{r}$) and permittivity (${\varepsilon}_{r}$) increased and the matching frequency is shifted toward lower frequency. The fabricated EM wave absorbers showed permeability $2{\sim}6$, permittivity $17{\sim}23$ for a $-325{\sim}+400$ mesh sample, and the calculated power absorption was as high as 80% in the frequency range over 2 GHz.
연자성 나노결정합금 분말의 열처리 온도에 의한 전자파 흡수 특성의 영향
홍순호,손근용,박원욱,문병기,송용설,Hong, S.H.,Sohn, K.Y.,Park, W.W.,Moon, B.G.,Song, Y.S. 한국분말야금학회 2008 한국분말재료학회지 (KPMI) Vol.15 No.1
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.
Yun, S.I.,Yun, B.K.,Moon, B.K.,Seo, H.G.,Park, H.L. 부산대학교 물성연구소 1986 물성연구소연구논문집 Vol.5 No.-
비방사과정에 의해 발행하는 열을 음파로 바꾸어 마이크로폰으로 검출하는 광음향법을 실리콘 태양전지에 적용하여 태양전지의 전기에너지 반환효율과 양자효율을 측정했다. 이 방법에서는 입사광의 세기, 태양전지의 유효면적등을 측정하지 않고도 에너지 변화효율을 얻을 수 있다. 태양전지가 개회로 상태에 있을 때에는 전기에너지 출력이 없기 때문에 받아들인 에너지 전부가 열에너지로 바꾸어지지만 부하가 걸리면 전기에너지 출력이 있어 발생하는 열이 감소된다. 따라서 개회로 때와 부하가 있을 때의 광음향신호의 세기가 달라진다. 이와같은 원리가 에너지변화효율 측정에 사용되었다. 입사광의 세기에 따른 에너지 변환효율 및 양자효율, 입사광의 파장에 따른 에너지 변화효율 및 양자효율등을 측정했다. The photoacoustic technique for the measurement of energy conversion efficiency and quantum efficiency of photovoltaic processes is studied, using a Si solar cell as the sample. The most significant advantage of this method over the conventional method is the capability of determining intrinsic energy conversion efficiency and quantum efficiency of the solar cell without knowlege of the irradiance or the number of photons irradiated and/or absorbed.