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RISS 인기검색어
- 검색키워드
- 저자 : Dang Mo Yoon (검색결과 6 건)
- 무료
- 기관 내 무료
- 유료
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Controlling the Shape of a Carbon Nanotube by Using the Reaction Chamber Pressure
D. Q. Duy,김현석,Dang Mo Yoon,Jung Woong Ha,Kang Jea Lee,황용규,Bach Thanh Cong,이충훈 한국물리학회 2009 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.55 No.1
We report the effects of the reaction chamber pressure on the shape and the structure of verticallyaligned carbon nanotubes (CNT) grown on a Ni catalyst by using dc plasmaenhanced chemical vapor deposition system. By controlling the pressure of the reaction chamber We were able to alter the shape and the crytallinity of CNTs. With increasing the chamber pressure, the length was rapidly reduced from 4.5 μm to 800 nm, but the crytallinity was strongly enhanced. As the reaction chamber pressure decreases, the tips of the CNTs were observed to change from a hemispherical tip with one conical Ni particle to a distorted the tip with more than one tiny Ni particle which means that the formation of Ni conglomerates does not only occur during the pretreatment process but also continues during the CNT growth process. These results have further clarified the role of the reactive etching ions in the growth of CNTs. We report the effects of the reaction chamber pressure on the shape and the structure of verticallyaligned carbon nanotubes (CNT) grown on a Ni catalyst by using dc plasmaenhanced chemical vapor deposition system. By controlling the pressure of the reaction chamber We were able to alter the shape and the crytallinity of CNTs. With increasing the chamber pressure, the length was rapidly reduced from 4.5 μm to 800 nm, but the crytallinity was strongly enhanced. As the reaction chamber pressure decreases, the tips of the CNTs were observed to change from a hemispherical tip with one conical Ni particle to a distorted the tip with more than one tiny Ni particle which means that the formation of Ni conglomerates does not only occur during the pretreatment process but also continues during the CNT growth process. These results have further clarified the role of the reactive etching ions in the growth of CNTs.
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Role of Atomic and Molecular Nitrogen in Carbon Nanotube Formation
Dao Quang Duy,김현석,Dang Mo Yoon,Jung Woong Ha,Kang Jea Lee,황용규,Bach Thanh Cong,이충훈 한국물리학회 2009 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.54 No.4
We have investigated the pretreatment effects of nitrogen on the length and the alignment of carbon nanotubes (CNTs) grown on a Ni catalyst by using dc-plasma enhanced chemical vapor deposition system. The surface of the Ni catalyst was pretreated with a mixture of NH3 and N2, instead of pure NH3 and the length of the CNTs has changed from 1.6 um to 400 nm as the NH3/N2 flow rate ratio was decreased. We showed that the length and the alignment of the CNTs could be controlled by changing the NH3/N2 flow rate ratio. The fabricated CNTs were further evaluated by using their Raman spectra. The nitrogen concentration on the surface of the Ni catalyst after the pre-treatment was analyzed by using X-ray photoelectron spectroscopy and the physical structure of CNTs was analyzed using scanning electron microscopy and high resolution transmission electron microscope. We suggest that the N2 adsorption on the surface of Ni changes the carbon atom diffusion during the CNT growth and that the physical structures of CNTs are drastically changed We have investigated the pretreatment effects of nitrogen on the length and the alignment of carbon nanotubes (CNTs) grown on a Ni catalyst by using dc-plasma enhanced chemical vapor deposition system. The surface of the Ni catalyst was pretreated with a mixture of NH3 and N2, instead of pure NH3 and the length of the CNTs has changed from 1.6 um to 400 nm as the NH3/N2 flow rate ratio was decreased. We showed that the length and the alignment of the CNTs could be controlled by changing the NH3/N2 flow rate ratio. The fabricated CNTs were further evaluated by using their Raman spectra. The nitrogen concentration on the surface of the Ni catalyst after the pre-treatment was analyzed by using X-ray photoelectron spectroscopy and the physical structure of CNTs was analyzed using scanning electron microscopy and high resolution transmission electron microscope. We suggest that the N2 adsorption on the surface of Ni changes the carbon atom diffusion during the CNT growth and that the physical structures of CNTs are drastically changed
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Enhanced out-coupling efficiency in OLEDs using ZnS nanodots
Bae, Il-Ji,Song, Dasom,Yoon, Dang Mo,Ghimire, Deepak,Kim, Miyoung,Lee, Bum-Joo,Joo, Byung Yun,Choi, Ju Hwan,Shin, Jin-Koog,Kang, Jae-Wook Informa UK (TaylorFrancis) 2016 Molecular Crystals and Liquid Crystals Vol.635 No.1
<P>We demonstrated highly efficient OLEDs by incorporating ZnS nanodots on top of a glass substrate via a chemical bath deposition process. The device efficiency of OLEDs with ZnS nanodot arrays was 1.26times higher than that of OLEDs without ZnS. This enhancement in device efficiency is attributed to the improved light out-coupling efficiency that is enabled by the improved optical performance of nanodot arrays, which results from their high refractive index and optical transmittance in the visible wavelength.</P>
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무하마드 싸빗 아이만(Muhammad Tsabit Ayman),배현모(Hyeon Mo Bae),권희진(Heejin Kwon),이재형(Jaehyung Lee),윤당혁(Dang-Hyok Yoon) 한국세라믹학회 2020 세라미스트 Vol.23 No.3
Among many kinds of transparent ceramics, polycrystalline gamma-aluminum oxynitride (γ-AlON) exhibits superior optical and mechanical properties to MgAl 2 O 4 (Mg-spinel), ZnS, MgO, and Y 2 O 3 , which are even comparable to those of sapphire. Due to its high strength, hardness, and wide transmittance range from the UV to mid-IR (0.2 – 5.2 µm), γ-AlON is being applied to IR cameras, scratch-resistant windows, missile domes, transparent armor, and others, especially with increasing demand nowadays. This report discusses the basic formation mechanism of transparent γ-AlON from the Al 2 O 3 and AlN starting materials as well as its stoichiometry based on a proposed constant anion model. In addition, the results from authors’ own research, including the effects of 2-step pressureless sintering and rare earth sintering additive on the properties of γ-AlON, are explained. We hope that this article helps expanding readers’ understanding on transparent ceramics as well as establishing research direction for further breakthrough of transparent polycrystalline γ -AlON.
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Field-Emission Electron Source Using Carbon Nanotubes for X-ray Tubes
KIM Hyun Suk,Lee Choong Hun,박종윤,DUY Dao Quang,HA Jung Woong,HWANG Yong Gyoo,KIM Jae Hoon,LEE Hyung Joo,LEE Kang Jea,SHIN Seok Seung,YOON Dang Mo 한국물리학회 2008 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.52 No.4
We have studied the feasibilities of using carbon nanotubes (CNTs) for the X-ray generation. The CNTs were grown on stainless-steel (SUS304) substrates by using a rapid thermal chemical vapor deposition (RTCVD) system and they were examined by scanning electron microscope and Raman spectroscopy. The CNTs were used to make field emitters in the triode geometry designed for X-ray generation. The grid was 500 μm from the cathode and the anode was 10 mm from the grid. The maximum anode current was measured to be 2.0 mA when +5.0 kV and --4.0 kV, with the grid grounded, were applied to the anode and the cathode, respectively. The stability of the anode current was examined and the X-ray images of biological structure were obtained using a field-emission CNT X-ray tube.
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