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Ni0.5Cu0.1Zn0.4Fe₂O₄ Ferrite - Rubber Composite의 전파흡수특성에 미치는 열처리 온도의 영향 및 Carbon 첨가효과
윤국태(Kuk-Tae Youn),이찬규(Chan-Gyu Lee),박연준(Youn-Joon Park) 한국자기학회 2001 韓國磁氣學會誌 Vol.11 No.1
The structure, shape, size, and magnetic properties of Ni_(0.5)Cu_(0.1)Zn_(0.4)Fe₂O₄ have been investigated as a function of annealing temperatures. In order to control the microwave absorbing properties of ferrite-rubber composite and the complex losses (magnetic loss and conduction loss), the effect of carbon addition was also studied. It was found that the coercive force decreased with increasing heat-treatment temperatures. Relative complex permeability and reflection loss were measured by the network analyzer. As a result, the natural resonance occurred in the low frequency range, and the matching frequency of the ferrite-rubber composite prepared at 1300℃ was found to be lower. As heat-treatment temperatures were increased, the magnetic loss (μr/μr') and the dielectric loss (εr/εr') were increased. It was caused that the absorption characteristics of the absorber were improved. The conduction loss and magnetic loss were expected to be occurred together because two matching frequencies were shown with carbon addition. It was confirmed that the matching frequency of the microwave absorber could be controlled by controlling heat-treatment temperatures and carbon additions.
$Ni_{0.5}-Zn_{0.4}-X_{0.1}{\cdot}Fe_2O_4$(X=Cu, Mg, Mn)-Rubber Composite의 전파흡수특성에 관한 연구
임희대,윤국태,이찬규,Im, Hui-Dae,Yun, Guk-Tae,Lee, Chan-Gyu 한국재료학회 1999 한국재료학회지 Vol.9 No.12
Electromagnetic wave asorbing properties of the $Ni_{0.5}-Zn_{0.4}-X_{0.1}{\cdot}Fe_2O_4$, where X was replaced by substitution elements Cu, Mg, Mn, have been studied. The structure, shape, size and magnetic properties of the $Ni_{0.5}-Zn_{0.4}-X_{0.1}{\cdot}Fe_2O_4$ were analyzed by XRD, SEM, VSM. The relative complex permittivity, permeability, and electromagnetic wave absorbing properties were measured by Network Analyzer. The structure, shape, size and magnetization value of the $Ni_{0.5}-Zn_{0.4}-X_{0.1}{\cdot}Fe_2O_4$ were found to be similar in spite of substitution elements. The coercive force and hysteresis-loss showed maximum value when Mg was substituted for X. The dielectric loss(${\varepsilon}_r"/{\varepsilon}_r'$) was found to be maximum value when Mn was substituted for X. Also the magnetic loss(${\mu}_r"/{\mu}_r'$} was found to be maximum with Cu substitution. The electromagnetica wave absorbing property of the $Ni_{0.5}-Zn_{0.4}-X_{0.1}{\cdot}Fe_2O_4$-Rubber composite with 4mm thickness was excellent as over - 40dB at 9GHz, and the $Ni_{0.5}-Zn_{0.4}-X_{0.1}{\cdot}Fe_2O_4$-Rubber composite with 8mm thickness was over-40dB at 2GHz. Those composites also showed superior microwave absorbing properties. $Ni_{0.5}-Zn_{0.4}-X_{0.1}{\cdot}Fe_2O_4$의 조성에서 X를 각각 Cu, Mg, Mn으로 치환시켜 치환원소에 따른 결정구조와 형상, 입도 및 자기적 성질을 비교 분석하여고, Network Analyzer을 이용하여 $Ni_{0.5}-Zn_{0.4}-X_{0.1}{\cdot}Fe_2O_4$-Rubber Composite의 재료정수 및 전파흡수특성에 대하여 비교 조사하였다. 치환원소에 관계없이 동일한 결정구조와 형상 및 입도를 나타냈고, VSM 분석결과 치환원소에 관계없이 동일한 자화값을 가지며, Mg로 치환된 경우 가장 큰 보자력과 자기이력손실을 나타냈다. 또한 Mn으로 치환된 경우 가장 높은 유전손실(${\varepsilon}_r"/{\varepsilon}_r'$)을, Cu로 치환된 경우에는 가장 큰 자기손실(${\mu}_r"/{\mu}_r'$)을 나타냈다. 4mm의 두께로 제조한 Compos-Composite에서는 Mg로 치환된 시료가 2GHz에서 -40dB이상의 가장 우수한 전파흡수특성을 나타내었다.
초고장력강판 성형용 냉간 프레스 금형의 Ti/Cr계 PVD코팅에 대한 마모 특성 평가
허재영,윤국태,송재선,강익수,윤일채,박춘달 한국소성∙가공학회 2022 소성가공 : 한국소성가공학회지 Vol.31 No.4
The application of UHSS sheet is being expanded up to 50% to reduce the weight of automobiles and improve safety. However, due to the high strength and low elongation of the ultra-high tensile strength steel sheet, product defects such as spring back and mold defects such as cracks and chippings also occur. In this study, Pin/Ring on Disc and Spiral wear tests were conducted to evaluate the durability of Ti/Cr-coated molds for forming 1.2GPa grade UHSS sheets. Component analysis and thickness were measured for each coating layer, and hardness and adhesion were investigated to determine mechanical properties. Combining the results of various wear tests, it was found that the TiAlN coating had the best wear and sticking resistance.