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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
Pretreatment Effects on the Lengths and Diameters of Carbon Nanotubes
이충훈,Dao Quang Duy,김현석,윤당모,김재훈,하정웅,이강재,황용규,Bach Thanh Cong 한국물리학회 2008 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.53 No.5
We have investigated the pretreatment effects on the lengths and the diameters of carbon nanotubes (CNTs) grown on a Ni catalyst by using dc plasma-enhanced chemical-vapor deposition system. The average sizes of the Ni particles changed with the cathode bias during the pretreatment, with the minimum value at a cathode voltage -100 V. The diameters of the CNTs followed the size of the Ni particles. In the cathode voltage range from -100 V to -600 V, the average diameter of the CNTs changed from 31.7 nm to 66.5 nm with increasing Ni sizes. The plasma power and the pretreatment time should be optimized to control the diameters of vertically-aligned CNTs. Also, N2 is added in NH3 during the pretreatment, the lengths and the densities of the CNTs can be controlled.
Yang, Byeong Woo,Quang Dao, Pham Duy,Yoon, Nam Sik,Cho, Chan Sik Elsevier 2017 Journal of organometallic chemistry Vol.851 No.-
<P><B>Abstract</B></P> <P>2-(2-Bromovinyl)benzimidazoles are coupled and cyclized with 1,3-diketones in DMF in the presence of a catalytic amount of copper(I) iodide and a base to afford the corresponding benzo[4,5]imidazo[1,2-<I>a</I>]pyridines in moderate yields. 2-(2-Bromoaryl)benzimidazoles also react with 1,3-diketones under similar reaction conditions to give benzo[4,5]imidazo[2,1-<I>a</I>]isoquinolines in similar yields.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Copper-catalyzed carbon-carbon coupling followed by cyclization. </LI> <LI> Synthesis of benzimidazole-fused pyridines and isoquinolines. </LI> <LI> A new synthetic method for N-fused heterocycles using coupling and cyclization protocol. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>
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.