• 한국재료학회:학술대회논문집
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• 한국재료학회 2009년도 춘계학술발표대회
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• pp.31.2-31.2
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• 2009

In this research, single walled carbon nano-tube film was manufactured with spray coating method on glass for application as transparent heat element. SWNTs solution to be used for spraying is obtained by dispersion of 0.01 wt% purified SWNTs in dimethylformamide (DMF) solution through ultrasonification and centrifugation. The transmittance and sheet resistance of SWNTs film were determined by the number of spray injection. Manufactured SWNTs film will have sheet resistance range of $200\;\Omega/\square-900\;\Omega/\square$ at transmittance range of 70-90 %. Heat generation characteristic of SWNTs film was measured by applying constant DC voltage of 15V. The result confirmed that SWNTs film with sheet resistance of $200\;\Omega/\square$ reaches surface temperature of $80^{\circ}C$ within several seconds. In addition, PET coating film was coated on top of the SWNTs film by using laminator in order to solve weak adhesive property of the spray coated SWNTs film on the substrate as well as to maintain its electrical and optical properties.

• 대한전기학회논문지:전기물성ㆍ응용부문C
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• 제54권4호
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• pp.139-143
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• 2005

For application of carbon nano-tube (CNT) as a counter electrode materials of dye-sensitized solar cell (DSSC), the electrochemical behavior of CNT electrode was studied, employing cyclic-voltammetry (C-V) and impedance spectroscopy. Fabrication of CNT-paste and formation of CNT-counter electrode for characteristic measurement have been carried out using ball-milling and doctor blade process, respectively. Unit cell for measurements was assembled using Pt electrode, CNT electrode, and iodine-embedded electrolyte. Field emission-scanning electron microscopy (FE-SEM) was used for structural investigation of CNT powder and electrode. Sheet resistance of electrode was measured with 4-point probe method. Electrochemical properties of electrode, C-V and impedance spectrum, were studied, employing potentiogalvanostat (EG&G 273A) and lock in amplifier (EG&G 5210). As a results, the sheet resistance of CNT electrode is almost similar to that of F-doped SnO2 (FTO) coated glass substrate as approximately 10 ohm/sq. From C-V and impedance spectroscopy measurements, it was found that CNT electrode has high reaction rate and low interface reaction resistance between CNT surface and electrolyte. These results provides that CNT electrode were superior to that of conventional Pt electrode. Particularly, the reaction rate in the CNT electrode is about thrice high than Pt electrode. Therefore. CNT electrode is to be good candidate material for counter electrode in DSSC.

• 한국재료학회지
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• 제25권7호
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• pp.341-346
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• 2015

The feasibility of obtaining graphitic carbon films on targeted substrates without a catalyst and transfer step was explored through the pyrolysis of the botanical derivative camphor. In a horizontal quartz tube, camphor was subjected to a sequential process of evaporation and thermal decomposition; then, the decomposed product was deposited on a glass substrate. Analysis of the Raman spectra suggest that the deposited film is related to unintentionally doped graphitic carbon containing some $sp-sp^2$ linear carbon chains. The films were transparent in the visible range and electrically conductive, with a sheet resistance comparable to that of graphene. It was also demonstrated that graphitic films with similar properties can be reproduciblyobtained, while property control was readily achieved by varying the process temperature.

• 한국지진공학회논문집
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• 제12권1호
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• pp.21-28
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• 2008

CFT(Concrete Filled Steel Tube)기둥은 부재의 합성효과와 경제적인 측면 때문에 최근 고층건물 시공 시 널리 쓰이고 있다. 그러나 기존의 연구문헌을 살펴보면 CFT 기둥은 강관의 항복이후 강관의 일정지점에 국부좌굴이 생기는 단점을 지니고 있다. 이러한 문제점을 해결하기 위하여 예상 국부좌굴부위를 탄소섬유쉬트로 보강하여 국부좌굴을 방지하거나 지연시키는 TR-CFT (Transversely Reinforced Concrete Filled Steel Tube) 기둥에 관한 연구가 진행되고 있다. 본 연구에서는 고강도 콘크리트를 사용한 TR-CFT기둥의 실험을 수행하였으며 휨내력에 대한 해석을 수행한 결과 실험값과 해석값이 잘 일치하였다. 또한 기존의 ACI 318 설계법은 강관내부에서 발생하는 콘크리트에 대한 구속효과를 고려하지 않아 저평가가 되어있음을 알 수 있었다.

• Journal of Welding and Joining
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• 제22권6호
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• pp.19-24
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• 2004

The laser welding and its analysis of thin-sheet carbon steels were carried out with high power $CO_{2}$ laser. The main factor of weld quality of laser welding is gap and edge quality. This work was preformed to focus on the gap tolerance problem during laser welding. First, bead on plate welding of thin sheet was examined to investigate the effect of laser welding variables, and to obtain optimum welding condition. Butt welding was also carried out to show the effect of gap on the laser weldability of thin sheet. In order to investigate the effect of gap on formability of welded thin sheet, LDH test was caried out. At high welding speed, the partial penetration was obtained by low heat input. Otherwise, porosity was formed in the bead at low weld speed because of too much heat input. The optimum welding condition of welding was derived from bead width, penetration and hardness property. The maximum gap tolerance on laser welding was observed to be about 0.2mm. This gap size has good relationship with beam size of laser spot(about 0.3mm). The formability of welded sheet was about $80{\%}$ value of base metal and the gap size has not affected on the formability, although weld quality is dependent on the gap size.

• 한국강구조학회 논문집
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• 제22권2호
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• pp.185-195
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• 2010

본 연구에서는 탄소섬유쉬트로 추가구속된 각형 CFT기둥 실험체의 단조압축실험을 수행하였고 이를 토대로 실험체의 연성능력을 평가하였다. 실험변수는 탄소섬유쉬트 보강겹수와 폭-두께비, 갭부착유무이며 실험변수에 따라 총 9개의 실험체를 제작하여 단조압축실험을 수행하였다. 실험을 통하여 각 실험체의 파괴거동, 하중-축변위 곡선, 최대내력, 변형성능을 비교한다. 탄소섬유쉬트의 추가구속은 기둥의 국부좌굴을 지연시켰으며 갭의 부착으로 탄소섬유쉬트의 구속분담시점을 지연시켜 연성능력은 상승한 것으로 나타났다.

• Carbon letters
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• 제6권1호
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• pp.31-40
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• 2005

The carbon nanofibers (CNFs) were synthesized through the catalytic decomposition of hydrocarbons in a quartz tube reactor. The CNFs prepared from $C_3H_8$ at $550^{\circ}C$ was selected as the purification sample due to the higher content of impurity than that prepared from other conditions. In this study, we carried out the purification of CNFs by oxidation in air or carbon dioxide after acid treatment, and investigated the influence of purification parameters such as kind of acid, concentration, oxidation time, and oxidation temperature on the structure of CNFs. The metal catalysts could be easily eliminated from the prepared CNFs by liquid phase purification with various acids and it was verified by ICP analysis, in which, for example, Ni content decreased from 2.51% to 0.18% with 8% nitric acid. However, the particulate carbon and heterogeneous fibers were not removed from the prepared CNFs by thermal oxidation in air and carbon dioxide. This result can be explained by that the direction of graphene sheet in CNFs is vertical to the fiber axis and the CNFs are oxidized at about the similar rate with the impurity carbon.

• Steel and Composite Structures
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• 제10권2호
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• pp.187-205
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• 2010

The existing CFT columns present the deterioration in confining effect after the yield of steel tube, local buckling and the deterioration in load capacity. If lateral load such as earthquake load is applied to CFT columns, strong shearing force and moment are generated at the lower part of the columns and local buckling appears at the column. In this study, axial compression test and beam-column test were conducted for existing CFT square column specimens and those reinforced with carbon fiber sheets (CFS). The variables for axial compression test were width-thickness ratio and the number of CFS layers and those for beamcolumn test were concrete strength and the number of CFS layers. The results of the compression test showed that local buckling was delayed and maximum load capacity improved slightly as the number of layers increased. The specimens' ductility capacity improved due to the additional confinement by carbon fiber sheets which delayed local buckling. In the beam-column test, maximum load capacity improved slightly as the number of CFS layers increased. However, ductility capacity improved greatly as the increased number of CFS layers delayed the local buckling at the lower part of the columns. It was observed that the CFT structure reinforced with carbon fiber sheets controlled the local buckling at columns and thus improved seismic performance. Consequently, it was deduced that the confinement of CFT columns by carbon fiber sheets suggested in this study would be widely used for reinforcing CFT columns.

• 한국강구조학회 논문집
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• 제19권4호
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• pp.403-411
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• 2007

CFT(Concrete filled steel tube)기둥은 콘크리트와 강관의 이질적인 성질을 상호보완 할 수 있는 구조체 일뿐만 아니라 시공적인 측면에서도 공기단축으로 인한 공사원가 절감으로 인해 최근 널리 사용되고 있다. 그러나 기존CFT기둥은 강관의 항복이후 일정지점의 국부좌굴을 생기는 단점을 지니고 있다. 이를 개선하고자 본 연구에서는 예상국부좌굴위치에 탄소섬유쉬트로 보강을 한 TR(Tranversely reinforced) -CFT기둥에 대해 실험을 수행하였다. 실험변수는 콘크리트강도와 탄소섬유쉬트보강량이며 CFT실험체와 TR-CFT실험체의 이력곡선, 초기강성, 내력, 소성변형능력, 흡수에너지를 각각 비교분석하였다.

• Nuclear Engineering and Technology
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• 제25권4호
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• pp.507-514
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• 1993

Titanium재료는 해수에서 좋은 내식성을 가지는 이유로 최근 원자력발전소 복수기에 사용되고 있다. 그러나, Ti이 tubesheet재 료인 Cu 합금에 접하고 이것이 water box 재료인 탄소강에 접하게될 경우 접촉금속에 심한 galvanic corrosion이 일어나게 된다. 전기화학적 실험에 의하면, 탄소강이 해수속에서 Ti나 Cu에 접할 때 탄소강의 부식속도는 증가할 것이며, Cu가 Ti에 해수중에서 장기간 접촉할 경우에는 Cu의 부식속도는 증가할 것으로 생각된다, 또한 표면적비, R$_1$(surface area of carbon steel/surface area of Ti).와 R$_2$(surface area of carbon steel/surface area of Cu)가 탄소강의 galvanic corrosion에 매우 중요하며. Water box 재료인 탄소강의 부식속도를 최소화하기 위해서는 이들 표면적비가 낮게 유지되어서는 안될 것이라고 생각된다 침지 galvanic 부식 시험결과 surface area of Fe/surface area of Al Brass값이 1일때 탄소강의 부식속도는 4.4mpy 이었으나 이 비가 $10^{-2}$ 일때는 570mpy이었다. 이렇게 연결된 galvanic시편에 Ti tube를 연결한 경우에는 이 비가 1일때 탄소강의 부식율이 4.4mpy에서 13mpy로 증가하였다. 이는 R$_1$가 R$_2$가 분극곡선에 복합적인 영향을 미치는것으로 설명할 수 있다.