• Journal of the Korean Vacuum Society
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• v.18 no.6
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• pp.481-487
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• 2009

To control the diameter size of the carbon nanofilaments (CNFs), SF6 was incorporated in the source gases ($C_2H_2/H_2$) during the initial deposition stage. The source gases and $SF_6$ were manipulated as the cyclic on/off modulation of $C_2H_2/H_2/SF_6$ flow in a thermal chemical vapor deposition system. The characteristics of the CNFs formation on the substrate were investigated according to the different cyclic modulation processes and the substrate temperatures. By $SF_6\;+\;H_2$ flow injection during the cycling etching interval time, the diameter size of CNFs was extremely decreased. The cause for the decrease in the diameter size of the individual CNFs by the cyclic on/off modulation process of $C_2H_2/H_2/SF_6$ flow was discussed in association with the slightly enhanced etching ability by the incorporation of $SF_6$.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.20 no.3
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• pp.133-140
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• 2010

Carbon fiber has many potential applications in a wide array of fields of solar cell, fuel cell, batteries, and polymer matrix composites due to an exceptional mechanical properties and chemical stability. In this study, the effects of catalysts on the property of carbon nanostructures grown on the carbon fiber were systematically investigated. The surface treatment of carbon fiber and catalysts synthesis for carbon nanostructures growth were carried out by one-pot ELP method and thermal CVD, respectively. The surface morphology and crystal structure of carbon nanostructures were examined using a field emission scanning electron microscope and transmission electron microscope. Depending on the type of catalysts and the molar ratio, various types of carbon nanostructures like carbon nanotube, carbon nanofilament, carbon nanospring and etc. were synthesized on the surface of carbon fibers surface.

• Applied Chemistry for Engineering
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• v.19 no.4
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• pp.413-420
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• 2008

Over the past decade, there have been significant advancement in the field of electrospinning area. This study has focused on preparing yarn using polycarbonate (PC) nanofibers including modified multi-walled carbon nanotube (mMWNT) by solution electrospinning process using the mixture of solvents consisting of tretrahydronfuran (THF) and N,N-dimethylformamide (DMF). In order to enhance the dispersion, MWNT was chemically modified. TEM analysis for the prepared PC/mMWNT nanofibers reveals that mMWNT was well-dispersed into the PC nanofiber matrix. Also with increasing contents of mMWNT, thermal stability of PC/mMWNT nanofibers was improved than that of PC nanofibers. Moreover when 3 to 5 wt% of mMWNT was added, the nanofibers showed good electrical properties expecting antistatic effect, ranging 109.1~109.5 ${\Omega}$. It was confirmed that the multi-filament fibers using PC/mMWNT had $60{\sim}100{\mu}m$ in diameter and 4~5 cm in length.

• Proceedings of the Korean Institute of Resources Recycling Conference
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• 2003.10a
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• pp.181-184
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• 2003

본 연구에서는 열 필라멘트 화학증착 방법에 의한 나노 다이아몬드 박막 증착을 위해 핵 생성 밀도를 증가시키기 위해서 다이아몬드 특성을 갖는 탄소(Diamond-Like Carbon)박막들을 연속 및 펄스 플라즈마를 이용한 화학 증착법에 의하여 증착하여 그 특성을 SEM, XPS, Raman 및 Nano-Tester를 이용하여 분석하였으며 열 필라멘트 화학 증착법에 의하여 나노 다이아몬드 박막 형성에 대한 핵 밀도와 다아이몬드 특성을 갖는 탄소 박막의 특성의 연관성을 관찰하여 공구(WC-Co)의 표면 사전 처리 없이 나노 다이아몬드 박막 형성을 용이하게 하는 실험을 수행하였다.

• Proceedings of the International Microelectronics And Packaging Society Conference
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• 2002.05a
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• pp.158-164
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• 2002

본 연구에서는 탄소나노튜브를 직류 바이어스가 인가된 유도결합형 플라즈마 열선 화학기상증착 장치를 이용하여 58$0^{\circ}C$ 이하의 저온에서 유리기판의 변형 없이 수직 배향 시켰다. 탄소나노튜브의 성장을 위해 강화유리기판 위에 전도층으로 Cr을 증착하였고, 그 위에 촉매 층으로 Ni을 순차적으로 RF magnetron cputtering 장치를 이용하여 증착 시켰다. 성장 시 탄소나노튜브의 저온에서의 좋은 특성을 위해 높은 온도에서의 열분해를 목적으로 텅스텐 필라멘트를 이용하였으며, 수직 배향 시키기 위해서 직류 바이어스를 이용하였다. 성장된 탄소나노튜브는 수직적으로 잘 배향 되었으며, 저온에서 좋은 특성을 보였다. 탄소나노튜브의 특성화에는 SEM, TEM을 관찰하였으며, Raman spectroscopy를 이용하여 흑연화도를 측정하였고, 전계방츨 특성은 전류 전압 특성곡선과 Fowler-Nordheim plots를 이용하였다.

• Journal of the Korean Vacuum Society
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• v.17 no.6
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• pp.566-575
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• 2008

We investigated the field emission characteristics from the planar field emitters made of double-walled carbon nanotubes (DWCNTs) synthesized by a catalytic chemical vapor deposition (CCVD) method. Transmission electron microscopy, Thermogravimetric and Raman analysis showed that the carbon materials have a low defect level in their atomic carbon structure, pointing to the synthesis of high-purity DWCNTs. For field emission properties of DWCNTs, the turn-on field of DWCNTs was $1.9\;V/{\mu}m$ and the current density was about $74\;mA/cm^2$ at $8.1\;V/{\mu}m$, which is sufficient for the applications of field emission displays and vacuum microelectronic devices. The DWCNT field emitters also exhibited a uniform field emission pattern and good field emission stability in a diode configuration.

• Proceedings of the Korean Vacuum Society Conference
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• 2014.02a
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• pp.283.2-283.2
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• 2014

열필라멘트 화학증착공정(Hot Wire Chemical Vapor Deposition)에서 기상 에서 생성되는 하전된 실리콘 나노입자와 저온결정성 실리콘박막 증착의 연관성을 압력의 변화에 따른 상호비교를 통해 조사하였다. 필라멘트 온도는 $1800^{\circ}C$로 고정시키고 0.3~2 torr의 범위에서 공정 압력을 변화시키면서 증착하였다. 압력이 증가함에 따라 증착된 실리콘 박막의 결정화도는 증가하였으며, 증착속도는 감소하였다. 반응기 압력에 따른 기상에서 생성되는 나노입자의 크기분포의 변화를 조사하기 위하여 탄소막이 코팅된 투과전자현미경(Transmission Electron Microscopy) 그리드 위에 실리콘 나노입자를 포획하고 관찰하였다. 포획된 실리콘 나노입자의 크기분포와 개수농도는 압력이 증가함에 따라 감소하였다. 투과전자현미경을 이용하여 분석한 결과, 나노입자는 결정성 구조를 보였다. 압력이 증가함에 따라 나노입자의 크기가 감소하고 개수농도가 감소하는 것은 증착속도의 감소와 관련됨을 알 수 있다. 한편, 공정압력 증가에 따른 나노입자의 크기분포 및 개수농도 감소와 증착속도의 감소는 일반적으로 알려진 기상에서 석출하는 고상의 평형석출량(equilibrium amount of precipitation)이 압력의 증가함에 따라 증가한다는 사실과 일치하지 않는다. 이러한 압력경향성은 Si-H 시스템이 0.3~2 torr의 압력 영역에서 retrograde solubility를 갖는 것을 의미한다. 나노입자의 하전여부, 크기분포 및 개수농도를 측정하기 위하여 입자빔질량분석장비(Particle Beam Mass Spectroscopy)를 이용하였다. 그 결과, 실리콘 나노입자는 양 또는 음의 극성을 가진 하전된 상태임을 확인하였고, 투과전자현미경(TEM) grid에 포획한 실리콘 나노입자의 크기와 경향성이 일치하였다. 이는 나노입자가 저온의 기판에서 핵생성되어 성장하여 생성된 것이 아니라 열필라멘트 주위의 고온영역에서 생성된 것을 의미한다.

• Journal of the Korean Ceramic Society
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• v.39 no.2
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• pp.171-177
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• 2002

In this study, the vertical aligned carbon nanotubes was synthesized by DC bias-assisted Inductively Coupled Plasma Hot-Filament Chemical Vapor Deposition (ICPHFCVD). The substrate used CNTs growth was Ni(300 ${\AA}$)/Cr(200 ${\AA}$)-deposited one on glass by RF magnetron sputtering. R-F, DC bias and filament power during the growth process were 150 W, 80 W, 7∼8 A, respectively. The grown CNTs showed hollow structure and multi-wall CNTs. The top of grown CNT was found to Ni-tip that the CNT end showed to metaltip. The graphitization and field emission properties of grown was better than grown CNTs by ICPCVD. The turn-on voltage of CNT grown by DC bias-assisted ICPHFCVD showed about 3 V/${\mu}m$.

• Proceedings of the Materials Research Society of Korea Conference
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• 2001.11a
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• pp.55-55
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• 2001

• Polymer(Korea)
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• v.38 no.2
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• pp.240-249
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• 2014

Multi-walled carbon nanotube (MWNT) reinforced poly(ethylene terephthalate) (PET) composites are studied. To increase the interfacial interactions between PET and MWNTs, the MWNTs are functionalized with bishydroxy-ethylene-terephthalate (BHET). The functionalized MWNTs are melt blended into PET matrix using a twin screw extruder. The amount of MWNTs loaded in PET matrix ranges from 0.5 to 2.0 wt%. After compounding and spinning, the filaments are post-drawn and annealed. To verify the chemical modifications of carbon nanotubes, Raman, $^1H$ NMR, XPS, TGA and FE-SEM are used. The nanocomposites are also analyzed with DSC, TGA, and UTM. These tests show that crystallization temperature and thermal degradation temperature increase due to the functionalized MWNTs. Also, tensile test shows that yield strength and toughness increase more than 30% with addition of only 1 wt% of MWNTs. These results show that the introduction of BHET onto the MWNTs is a very effective way in manufacturing MWNT/PET composite.