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고온열처리가 고체산화물연료전지의 전극과Ag 페이스트의 계면에 미치는 특성 평가
전상구 ( Sang Koo Jeon ),남승훈 ( Seung Hoon Nahm ),권오헌 ( Oh Heon Kwon ) 한국안전학회(구 한국산업안전학회) 2015 한국안전학회지 Vol.30 No.1
In this study, interfacial characteristics between SOFC and Ag paste as current collector was estimated in the high temperature environment. The Ag paste was used to connect the unit cell of SOFC strongly with interconnector and provide the electrical conductivity between them. To confirm electrical conductivity, Ag paste was treated in the furnace at 800°C for 48 hours. The sheet resistance of Ag paste was measured to compare the resistance values before and after the heat treatment. Also, the four-point bending test was performed to measure the interfacial adhesion. The unit cell of SOFC and SiO2 wafer were diced and then attached by Ag paste. The SiO2 wafer had the center notch to initiate a crack from the tip of the notch. The modified stereomicroscope combined with the CCD camera and system for measuring the length was used to observe the fracture behavior. To compare the characteristics before heat treatment and after heat treatment, the specimen was exposed in the furnace at 800 °C for 48 hours and then the interfacial adhesion was evaluated. Finally, the interfacial adhesion energy quantitatively increases 1.78±0.07 J/m2 to 4.9±0.87 J/m2 between the cathode and Ag paste and also increase2.9±0.47 J/m2 to 5.12±1.01 J/m2 between the anode and Ag paste through the high temperature. Therefore, it is expected that Ag paste as current collector was appropriate for improving the structural stability in the stacked SOFC system if the electrical conductivity was more increased
변형률-수명 평가기법을 이용한 Al/CFRP 하이브리드 적층 복합재의 피로수명 측정
양성진,권오헌,전상구,Yang, Seong Jin,Kwon, Oh Heon,Jeon, Sang Koo 한국안전학회 2021 한국안전학회지 Vol.36 No.3
Hybrid laminated Al/carbon-fiber-reinforced plastic (CFRP) composites are attracting considerable attention from industries such as aerospace and automobiles owing to their excellent specific strength and specific rigidity. However, when this material is used to fabricate high-pressure fuel storage containers subjected to repeated fatigue loads, fatigue life evaluation for the working load is regulated as an important criterion for operational safety and ease of maintenance. Among the existing evaluation methods for these vessels, the burst test and the hydraulic repeat test require expensive facilities. Thus, the present study aims to develop an improved fatigue life test for Al/CFRP laminated hybrid composites. The test specimen was manufactured using a curved mold considering the shape of a type III high-pressure storage container. The strain-life method was used for fatigue life evaluation, and the life was predicted based on the transition life. The results indicate that the more complex the CFRP stacking sequence, the longer is the transition life. This test method is expected to be useful for ensuring the fatigue safety and economy of hybrid laminate composites.
다중벽 탄소나노튜브의 기계적-전기적 물성 과 나노튜브 시트 특성
장훈식(Hoon-Sik Jang),전상구(Sang Koo Jeon),정인현(In Hyun Jeong),박종서(Jong-Seo Park),남승훈(Seung Hoon Nahm) 대한기계학회 2010 대한기계학회 춘추학술대회 Vol.2010 No.11
The mechanical and electrical properties of a multi walled carbon nanotubes (MWCNTs) were investigated inside a scanning electron microscope. The mechanical strain was applied to the MWCNT by a tungsten tip controlled by a nano-manipulator. The tensile strength of the MWCNT was about 41.01 GPa and the elastic modulus was calculated at 0.98 TPa. The electrical resistance was significantly changed during the elongation process of the MWCNT and corresponded with the nanotube strain. The strain sensitivity of a single MWCNT was calculated to be around 25. We also investigated a flexible transparent film using the spinning MWCNTs. The MWCNT sheets were produced by continuously pulling out from super well-aligned MWCNTs on a substrate. The MWCNT sheet films were produced simply by direct coating on the flexible film or grass. Single and double sheets were produced with sheet resistance of ~699 and ~349 Ω/sq, respectively, transmittance of 81~85 % and 67~72 %, respectively.