• Transactions of the Korean hydrogen and new energy society
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• v.16 no.4
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• pp.343-349
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• 2005

In this study, We had surface-treated single-walled carbon nanotubes (SWNTs) for improving hydrogen storage capacity. The SWNTs were treated by heat treatment, acid treatment and fluorinated at various temperatures. The SWNTs were characterized by Raman spectroscopy and TEM and estimated hydrogen storage capacities at 303K. As shown Raman spectra and TEM images, the structure of fluorinated SWNTs were stable at 423K but changed to the MWNTs-like structure or onion structure over 523K. Hydrogen storage capacity of SWNTs fluorinated at 423K was remarkably increased 2.6 times than that of pristine SWNTs. For SWNTs fluorinated at 573K, the amount of hydrogen adsorbed wasn't increased compared with SWNTs fluorinated at 423K. Therefore, high hydrogen storage capacity of SWNTs could be archived by fluorinated condition at 423K, which was not changed SWNT structure.

• Proceedings of the Korean Vacuum Society Conference
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• 2016.02a
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• pp.337.1-337.1
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• 2016

단일벽 탄소나노튜브(Single-walled carbon nanotubes, SWNTs)는 나노 스케일의 크기와 우수한 물성을 갖고 있어, 전자, 에너지, 바이오 등 다양한 분야로의 응용이 기대되고 있다. 이러한 응용의 실현을 위해서는 경제적, 산업적인 면에서 보다 손쉬운 합성법이 요구된다. SWNTs의 합성에는 대면적의 균일한 CNTs를 합성할 수 있다는 장점이 있는 열화학기상증착법(Thermal chemical vapor deposition, TCVD)이 가장 일반적으로 사용되고 있다. 하지만 탄화수소가스를 효율적으로 분해하기 위하여 $900^{\circ}C$ 이상의 고온공정이 요구되며, 이는 경제적, 산업적인 면에서 사용이 제한적이다. 따라서 저결함, 고수율의 SWNTs를 저온합성 할 수 있는 공정의 개발이 지속적으로 필요하다. 본 연구에서는, TCVD법을 이용하여 에틸렌 원료가스로 SWNTs의 저온합성 가능성을 확인하였다. 합성을 위한 기판과 촉매로는 실리콘 산화막 기판(SiO2/Si wafer)에 철 나노입자를 지닌 ferritin을 스핀코팅 후 산화하여 이용하였다. 저온합성 공정의 변수로는 합성온도와 원료가스인 에틸렌의 분율을 설정하여, 변수가 SWNTs의 결정성과 수율에 미치는 영향을 고찰하였다. 합성된 SWNTs의 분석의 용이함과 손지기(Chirality)의 제어 가능성을 확인하기 위하여 나노 다공성 물질인 제올라이트(Zeolite)를 보조 기판으로 사용하였다. 실험결과 에틸렌 원료가스로 합성한 SWNTs는 메탄을 원료가스로 사용한 경우보다 낮은 $700^{\circ}C$ 부근에서도 합성이 가능함을 확인하였다. 또한 에틸렌의 분율과 합성 시간의 정밀한 제어를 통해 SWNTs의 합성온도를 더욱 감소시키는 것도 가능할 것으로 예상된다.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2018.06a
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• pp.47-47
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• 2018

단일벽 탄소나노튜브 (Single-walled carbon nanotubes, SWNTs)는 우수한 물리적 화학적 특성을 갖고 있어 나노전자소자, 투명전도막, 에너지소자, 센서 등 다양한 분야로의 응용이 기대되고 있다. 열화학기상증착(Thermal chemical vapor deposition, TCVD)법은 SWNTs의 합성 공정이 간단하고 공정변수의 제어가 용이하다는 장점이 있어 SWNT 합성 연구에 가장 널리 사용되어 왔다. 일반적으로 금속 촉매의 박막이 증착된 합성 기판은 온도가 가장 높고 비교적 균일성이 보장되는 TCVD 반응기의 중심부에 위치시키고 공정변수를 변화해가며 연구를 진행해 왔다. 본 실험실에서는 수평형 반응기 전역에 합성 기판을 설치하여 SWNTs를 합성한 결과, 반응기의 중심보다 뒤의 영역에서 SWNTs의 합성 수율이 상당히 증가하는 것을 초기실험을 통해 확인하였다. 본 연구에서는 SWNTs 합성 시 가스 유량과 합성 온도를 변화시켰을 때 기판 위치에 따른 SWNTs의 수율 및 물성변화를 구체적으로 조사하였다. 합성가스와 촉매로는 메탄가스와 철 박막을 사용하였으며, 합성 수율의 변화는 고분해능 주사전자현미경을 이용하여 관찰하였다. 그리고 합성된 SWNTs의 형태 및 결정성은 라만분광법과 원자간힘현미경을 이용하여 평가하였다. 결과적으로, 진행하였던 모든 합성 조건에서 반응기 중심보다 뒤의 영역에서 더 고수율의 SWNTs가 합성되었으며, 최적 합성 조건의 SWNTs 면밀도는 99% 이상이었다. 본 연구의 결과는 CVD 공정을 이용하는 다양한 저차원 나노 소재의 합성에도 적용될 수 있을 것으로 사료되며, 추후 이에 대한 연구가 필요하다.

• Advances in nano research
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• v.6 no.4
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• pp.339-356
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• 2018

In this article, the critical buckling of a single-walled carbon nanotube (SWCNT) embedded in Kerr's medium is studied. Based on the nonlocal continuum theory and the Euler-Bernoulli beam model. The governing equilibrium equations are acquired and solved for CNTs subjected to mechanical loads and embedded in Kerr's medium. Kerr-type model is employed to simulate the interaction of the (SWNT) with a surrounding elastic medium. A first time, a comparison with the available results is made, and another comparison between various models Winkler-type, Pasternak-type and Kerr-type is studied. Effects of nonlocal parameter and aspect ratio of length to diameter of nanobeam, as well as the foundation parameters on buckling of CNT are investigated. These results are important in the mechanical design considerations of nanocomposites based on carbon nanotubes.

• Proceedings of the Korean Vacuum Society Conference
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• 2007.08a
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• pp.373-373
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• 2007

• Korean Journal of Materials Research
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• v.23 no.12
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• pp.737-744
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• 2013

We demonstrated size control of Au nanoparticles by heat treatment and their use as a catalyst for single-walled carbon nanotube (SWNTs) growth with narrow size distribution. We used uniformly sized Au nanoparticles from commercial Au colloid, and intentionally decreased their size through heat treatment at 800 oC under atmospheric Ar ambient. ST-cut quartz wafers were used as growth substrates to achieve parallel alignment of the SWNTs and to investigate the size relationship between Au nanoparticles and SWNTs. After the SWNTs were grown via chemical vapor deposition using methane gas, it was found that a high degree of horizontal alignment can be obtained when the particle density is low enough to produce individual SWNTs. The diameter of the Au nanoparticles gradually decreased from 3.8 to 2.9 nm, and the mean diameter of the SWNTs also changed from 1.6 to 1.2 nm for without and 60 min heat treatment, respectively. Raman results reconfirmed that the prolonged heat treatment of nanoparticles yields thinner tubes with narrower size distribution. This work demonstrated that heat treatment can be a straightforward and reliable method to control the size of catalytic nanoparticles and SWNT diameter.

• Bulletin of the Korean Chemical Society
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• v.27 no.10
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• pp.1651-1654
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• 2006

Field emission (FE) currents were measured for silver-pasted and glass-pasted single-walled carbon nanotubes (SWNTs) after illuminating the tubes with a pulsed 532 nm laser. A very low turn-on field of approximately 0.4 V/m m and a high current density ~1700 $\mu A/cm^2$ at 3.5 V/m m was obtained for the silver-pasted SWNTs after laser irradiation but on the whole, no improvements were found for the glass-pasted SWNTs. Two roles of laser irradiation for the silver-pasted SWNTs were proposed. First, the embedded SWNTs and SWNT bundles inside the silver paste were immerged on the outer surface due to an instantaneous melting or annealing of the silver metals by the laser resulting in an increase of the field emission sites. Second, the laser irradiation was thought to improve the electrical contact between SWNTs and the silver metal by reducing the contact resistance via laser-induced thermal annealing, which was responsible for increasing the FE currents.

• Composites Research
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• v.19 no.5
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• pp.7-11
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• 2006

The improved SWNTs/PANi composite actuator films applicable to an artificial muscle were fabricated successfully using a new process of manufacture that consists of 90% pure single-walled carbon nanotubes (SWNT) and chemical polymerization. PANi is electrically conducting polyaniline polymer. The conductivities of the composite SWNTs/PANi film-type actuators and the pure PANi films fabricated were measured as 56.15 S/cm and 17.38 S/cm, respectively, by the 4-prove method. The conductivity of the composite actuator is 3.2 times higher than the pure PANi film. The fabricated composite actuator showed higher conductivity than any other similar ones. The quality of samples was investigated by an electron scanning microscope (SEM). To measure the actuating strains, a specially designed beam balance apparatus was developed and strains of the composite actuators was measured by a laser displacement sensor subjected to electric currents. During the operation, the sample was soaked in the $NaNO_3$ solution and the sine-wave voltage in the range of $+1V{\sim}-1V$ was applied. The length of the composite actuator changed from $l_0=12.690$ mm to $l_1=12.733$ so that the change of length was l=0.043 mm and the strain was 0.34 %. This is a very high strain for this kind of a composite actuator. Other result reported by Tahhan showed 0.23 % strain, so that the present result is improved by 48%.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2005.06a
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• pp.927-931
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• 2005

Carbon nanotube actuator, working under physical conditions (in aqueous solution) and converting electrical energy into mechanical energy directly, can be a good substitute for artificial muscle. The carbon nanotube actuator simulated in this paper is an isotropic cantilever type with an adhesive tape which is sandwiched between two single-walled carbon nanotubes. For predicting the static and dynamic characteristic parameters, the analytical model for a 3 layer bimorph carbon nanotube actuator is developed by using Euler-Bernoulli beam theory. The governing equation and boundary conditions are derived from energy principles. The induced displacements of the theoretical model are presented in order to investigate the performance of the carbon nanotube actuator with different control voltages. The developed model presents invaluable means for designing and predicting the performance of carbon nanotube actuator that can be used in artificial muscle applications.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2007.06a
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• pp.426-426
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• 2007

We report the field emission characteristics of transparent single-walled carbon nanotube (SWNT) film printed using an inkjet. Pure SWNTs dispersed in dimethylformamide were printed in a transparent layer on indium-tin oxide-coated glass and annealed at $350^{\circ}C$. After taping treatment, SWNTs were oriented vertically on the substrate. The front and the back of the fabricated device produced simultaneous emissions of identical quality. In addition, inkjet printing directly achieved a patterned emission, without a secondary pattern process. This method allows simple fabrication using only SWNTs, without the use of other additives.