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김형근(Hyeongkeun Kim),박영철(Young-Chul Park),강준모(Junmo Kang),최성(Sung Choi),김근수(Keun Soo Kim),김영진(Young-Jin Kim),홍병희(Byung Hee Hong),최재붕(Jae-Boong Choi) 대한기계학회 2010 대한기계학회 춘추학술대회 Vol.2010 No.11
Graphene, a sheet consisting of sp²-bonded carbon atoms, is an attracting material for both scientists and industrial researchers because of its outstanding electrical and mechanical properties. Recently, the large-scale synthesis methods based on chemical vapor deposition (CVD) have been discovered, enabling the future application of graphene films as transparent electrodes. In this study, we measured the optical properties of graphene films through a various surface treatments such as multiple stacking, UV exposure, chemical doping and organic/inorganic hybrid. The optical properties of graphene samples were measured by imaging spectroscopic ellipsometry.
열화학기상증착법에 의해 성장된 탄소나노튜브의 기하학적 구조에 있어 촉매 두께가 미치는 영향
김형근(Hyeongkeun Kim),전경용(Kyoung-Yong Chun),최재붕(Jaeboong Choi),김영진(Youngjin Kim),백승현(Seunghyun Baik) 대한기계학회 2009 대한기계학회 춘추학술대회 Vol.2009 No.5
Vertically aligned carbon nanotube (CNT) arrays have been a hot topic in material research since ljima confirmed their structure and morphology in 1991. Here, we report the growth of carbon nanotubes (CNTs) by thermal chemical vapor deposition (CVD). We investigate the effect of catalyst thickness on the morphology of CNTs according to catalyst deposition methods. The diameters, density, and growth rate of the aligned CNTs were found to strongly depend on the catalyst thickness. The effect of different catalyst thickness on the characteristics of CNTs was systematically analyzed.
김형근(Hyeongkeun Kim),최재붕(Jaeboong Choi),홍병희(Byung Hee Hong),김영진(Youngjin Kim) 대한기계학회 2010 대한기계학회 춘추학술대회 Vol.2010 No.5
Recently, graphene has been extensively studied as a material for making future electronic device. In this work we report a chemical vapor deposition (CVD) synthesis of 30-inch scale monolayer graphene and roll-based layer-by-layer transfer onto polyethylene terephthalate (PET) substrates. Transmission electron microscopy (TEM), UV/Vis/IR spectroscopy, 4-probe electrical measurements and Raman spectroscopy studies indicate that these graphenes have highly-quality crystalline structures with the controllable number of layers.
그래핀/사파이어 기판상에 스퍼터링 후 열처리된 VO<sub>2</sub>박막의 구조 및 광학적 특성변화 연구
김근수,김형근,김예나,한승호,배동재,양우석,Kim, Keun Soo,Kim, Hyeongkeun,Kim, Yena,Han, Seung-Ho,Bae, Dong Jae,Yang, Woo Seok 한국진공학회 2013 Applied Science and Convergence Technology Vol.22 No.2
이산화바나듐($VO_2$)는 써모크로믹(thermochromic) 물질로서 온도변화에 따른 구조적 상전이에 의해 전기적, 광학적 특성을 스위칭 할 수 있는 매력적인 소재이며, 최근 신소재로써 그 연구가 활발한 그래핀 역시, 전기적으로나 광학적으로 그 특성이 우수하여 투명전극에 관한 연구가 아주 활발하게 진행되고 있다. 이에 우리는 $VO_2$와 그래핀 두 가지 소재를 접목했을 경우 나타나는 현상을 그래핀의 층 수와 온도를 변수로 하여 형성된 박막의 구조와 광학적 특성을 측정하고 분석하였다. 본 연구 결과에 따르면 그래핀 필름이 전사된 사파이어 기판 위에 형성된 $VO_2$ 박막의 표면구조 및 특성이 bare 사파이어 기판 위의 $VO_2$ 박막보다 그레인이 작고 밀도가 높아 균일하였으며, IR 영역에서의 광투과도 역시 그래핀 필름이 있을 경우 ~10% 정도 개선됨을 확인하였다. 아울러 평균상전이 온도를 낮출 수 있으며, 상전이 히스테리시스 변화폭 또한 좁아지는 것을 확인하였다. $VO_2$ is an attractive thermochromic material, in which its electrical and optical properties can be switched by the structural phase-transition about $68^{\circ}C$. Recently, graphene is also a rising material which is researched as a transparent electrode because of its superior electrical and optical characteristics. In this respect, we try to fabricate the hybridized films using $VO_2$ and graphene on transparent sapphire substrate and then we investigate a structure and characterize an optical property for the samples as a function of temperature. According to the result of IR-transmittance analysis of $VO_2$ films as a function of temperature, the graphene-supported sapphire substrates are better about 10% than the bare sapphire substrates. The mean phase transition temperatures are also decreased as the number of graphene-layers increased and the hysteresis of phase transitions are narrowed.
강준모(Junmo Kang),김형근(Hyeongkeun Kim),박영철(Young Chul Park),김주동(Joo Dong Kim),최성(Sung Choi),홍병희(Byung Hee Hong),김영진(Young-Jin Kim),최재붕(Jae-Boong Choi) 대한기계학회 2010 대한기계학회 춘추학술대회 Vol.2010 No.11
We demonstrate the application of graphene coated heat pipe, showing high thermal transfer and corrosion resistant by water environment. The graphene coating layer was directly synthesized on both the inside and the outside of Cu pipe using chemical vapor deposition (CVD) method. The surface properties of Cu pipe exposed to water were investigated by optical and Raman spectroscopy. The heat transfer property of Cu pipe was tested by using hot water flows, showing improved heat transfer effect on the graphene coated heat pipe. This suggested that the graphene coated heat pipe would be very useful for the corrosion resistant coating and high thermal conductive material.