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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.
Fe계 나노결정 분말코아의 연자성특성에 미치는 입도제어 및 바인더 첨가의 영향
조은경,조현정,권훈태,조은민,류혁현,손근용,박원욱,Cho E.K.,Cho H.J.,Kwon H.T.,Cho E.M.,Ryu H.H.,Sohn K.Y.,Park W.W. 한국분말야금학회 2006 한국분말재료학회지 (KPMI) Vol.13 No.4
The amorphous $Fe_{73}Si_{16}B_7Nb_3Cu_1$ alloy strip was pulverized to get a flake-shaped powder after annealing at $425^{\circ}C$ for 90 min and subsequently ground to obtain finer flake-shaped powder by using a ball mill. The powder was mixed with polyimide-based binder of $0.5{\sim}3wt%$, and then the mixture was cold compacted to make a toroidal powder core. After crystallization treatment for 1 hour at $380{\sim}600^{\circ}C$, the powder was transformed from amorphous to nanocrystalline with the grain size of $10{\sim}15nm$. Soft magnetic characteristics of the powder core was optimized at $550{\sim}600^{\circ}C$ with the insulating binder of 3wt%. As a result, the powder core showed the outstanding magnetic properties in terms of core loss and permeability, which were originated from the optimization of the grain size and distribution of the insulating binder.
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.
Al<sub>2</sub>O<sub>3</sub> 첨가에 따른 Fe계 나노결정립 P/M시트의 전자파 흡수특성
우수정,조은경,조현정,이재준,손근용,박원욱,Woo, S.J.,Cho, E.K.,Cho, H.J.,Lee, J.J.,Sohn, K.Y.,Park, W.W. 한국분말야금학회 2007 한국분말재료학회지 (KPMI) Vol.14 No.4
Electromagnetic wave absorbing materials have been developed to reduce electromagnetic interference (EMI) for electronic devices in recent years. In this study, Fe-Si-B-Nb-Cu base amorphous strip was pulverized using a jet mill and an attritor and heat-treated to get flake-shaped nanocrystalline powders, and then the powders were mixed, cast and dried with dielectric $Al_{2}O_{3}$ powders and binders. As a result, the addition of $Al_{2}O_{3}$ powders improved the absorbing properties of the sheets noticeably compared with those of the sheets without dielectric materials. The sheet mixed with 2 wt% $Al_{2}O_{3}$ powder showed the best electromagnetic wave absorption, which was caused by the increase of the permittivity and the electric resistance due to the dielectric materials finely dispersed on the Fe-based powder.
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.
멜트스피닝과 포정반응에 의해 제조된 YBCO 초전도체의 미세조직
박수진,김선화,박원욱,정형식 대한금속재료학회(대한금속학회) 1990 대한금속·재료학회지 Vol.28 No.4
YBa₂Cu₃O_(7-x) Preform was melted and solidified into ribbon shape via melt spinning process. The as-spun ribbon contains melt-decomposed phases of rod shaped 211 phase aligned to spinning direction and Ba, Cu-rich matrix. Superconducting 123 phase is formed by a heat treatment through reaction between the 211 phase and the matrix. The grain morphology of the 123 phase is very much dependent of the presence of liquid phase during the heat treatment. The highly aligned large grain structure with strong (00ℓ) peak obtained through peritectic transformation indicates that the 123 phase is predominantly grown from the rod shaped 211 phase through reaction at the interface with the matrix. Heat treatment below peritectic transformation temperature yielded equiaxed type grain structure, indicating the random nucleation and growth of 123 phase. In case of a bulk specimen prepared by conventional powder consolidation technique, sintering above peritectic transformation temperature produced large grain structures but with random orientations. This strongly indicates that the presence of liquid phase can improve grain structure by promoting grain growth but is not effective for aligning the grains during the 123 phase formation.