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서봉현,석지원,Bong Hyun Seo,Yonas Tsegaye Megra,Ji Won Suk 한국복합재료학회 2023 Composites research Vol.36 No.5
To enhance the performance of graphene-based devices, it is of great importance to better understand the interfacial interaction of graphene with its underlying substrates. In this study, the adhesion energy of monolayer graphene placed on dielectric substrates was characterized using mode I fracture tests. Large-area monolayer graphene was synthesized on copper foil using chemical vapor deposition (CVD) with methane and hydrogen. The synthesized graphene was placed on target dielectric substrates using polymer-assisted wet transfer technique. The monolayer graphene placed on a substrate was mechanically delaminated from the dielectric substrate by mode I fracture tests using double cantilever beam configuration. The obtained force-displacement curves were analyzed to estimate the adhesion energies, showing 1.13 ± 0.12 J/m<sup>2</sup> for silicon dioxide and 2.90 ± 0.08 J/m<sup>2</sup> for silicon nitride. This work provides the quantitative measurement of the interfacial interactions of CVD-grown graphene with dielectric substrates.
임수묵,석지원,Soomook Lim,Ji Won Suk 한국복합재료학회 2023 Composites research Vol.36 No.5
There has been increasing demand for real-time monitoring of body and ambient temperatures using wearable devices. Graphene-based thermistors have been developed for high-performance flexible temperature sensors. In this study, the temperature coefficient of resistance (TCR) of monolayer graphene was controlled by coating polyethylenimine (PEI) on graphene surfaces to enhance its temperature-sensing performances. Monolayer graphene grown by chemical vapor deposition (CVD) was wet-transferred onto a target substrate. To facilitate the interfacial doping by PEI, the hydrophobic graphene surface was altered to be hydrophilic by oxygen plasma treatments while minimizing defect generation. The effect of PEI doping on graphene was confirmed using a back-gated field-effect transistor (FET). The CVD-grown monolayer graphene coated with PEI exhibited an improved TCR of -0.49(±0.03) %/K in a temperature range of 30~50℃.
양돈장 작업장소별 암모니아 및 황화수소의 실시간 모니터링
박지훈 ( Ji Hoon Park ),강태선 ( Tae Sun Kang ),석지원 ( Ji Won Seok ),진수현 ( Su Hyun Jin ),허용 ( Yong Heo ),김경란 ( Kyung Ran Kim ),이경숙 ( Kyung Suk Lee ),윤충식 ( Chung Sik Yoon ) 한국산업위생학회 2013 한국산업보건학회지 Vol.23 No.4
Objectives: This study aims to assess the concentrations of ammonia and hydrogen sulfide according to task unit area at swine farms. Methods: A total of six swine farms were selected for this study. Ammonia and hydrogen sulfide were monitored using a real-time multi-gas monitor which could sample the gases simultaneously. The sampling was done in the pig building, manure storage facility and composting facility of each farm. Results: The concentration of ammonia in the pig buildings(GM 22.6 ppm, GSD 2.3) was significantly higher(p<0.0001) than in the manure storage facilities(GM 10.4 ppm, GSD 2.7) and composting facilities(GM 8.6 ppm, GSD 2.8). The concentration of hydrogen sulfide in the manure storage facilities(GM 9.8 ppm, GSD 3.2) was higher(p<0.0001) than in the pig buildings(GM 2.3 ppm, GSD 2.3) and composting facilities(GM 1.9 ppm, GSD 2.5). In particular, the levels of hydrogen sulfide in the confined manure storage facilities were higher than those in open-type facilities and the peak concentration(98 ppm) in the confined facilities was approximate to 100 ppm, at the value of Immediately Dangerous to Life or Health(IDLH). Conclusions: Suffocation accidents caused by hazardous gases at a swine farm have occurred annually. Real-time monitoring of the hazards should be done in order to protect farm workers and livestock from the sudden accidents.
탄소나노튜브 복합재를 이용한 고분자 액추에이터의 냉각 개선
박성욱 ( Chengxu Piao ),석지원 ( Ji Won Suk ) 한국복합재료학회 2017 Composites research Vol.30 No.2
낚싯줄이나 재봉실을 꼬아서 만드는 코일형 고분자 액추에이터는 열을 가하거나 냉각하면 수축하거나 늘어나면서 작동을 하게 된다. 따라서, 코일형 고분자 액추에이터의 동작 속도는 가열 및 냉각 속도에 매우 민감하게 되는 문제가 있다. 코일형 고분자 액추에이터의 동작 속도를 개선하기 위해서, 폴리디메틸실록산 복합재를 액추에이터에 코팅하였다. 폴리디메틸실록산에 다중벽 탄소나노튜브를 혼합함으로써, 액추에이터의 동작 속도를 약 13% 개선하였다. Coiled polymer actuators fabricated by twisting polymer fishing lines or sewing threads respond to heating and cooling with their contraction and relaxation. However, their actuation speed is highly dependent on the heating and cooling rates. In order to improve the actuation speed, the coiled polymer actuator was coated with polydimethylsiloxane composites. The introduction of multi-walled carbon nanotubes into the polydimethylsiloxane improved the actuation speed by about 13%.