• Proceedings of the Computational Structural Engineering Institute Conference
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• 2010.04a
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• pp.632-635
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• 2010

본 논문에서는 다중벽 탄소 나노튜브를 작동유체로 사용하는 전자장치 냉각용 소형 히트파이프의 열적성능을 실험적으로 확인 하였다. 실험의 결과들을 바탕으로 다중벽 탄소 나노튜브 나노유체를 작동유체로 사용하는 히트파이프의 열저항은 동일한 충진량을 가지는 물을 작동유체로 사용한 히트파이프와 비교하여 나노유체의 부피비가 0.5%일때, 최대 18.6% 감소한다. 다중벽 탄소 나노튜브 나노유체의 열저항은 동일한 입열량에서 나노유체의 부피비가 증가 할수록 감소하는 것을 알 수 있다. 이를 통하여 다중벽 탄소 나노튜브 나노유체 히트파이프의 열저항은 나노유체의 부피비에 변화에 따라서 변한다는 것을 확인 할 수 있으며, 추가적으로 증발부에서 유체의 기화로 인한 나노입자의 증착에 의하여 열전달 표면적의 증가 또한 열저항의 감소 원인으로 예측가능 하다.

• 한국신재생에너지학회:학술대회논문집
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• 2011.05a
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• pp.74.1-74.1
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• 2011

탄소나노튜브는 높은 전기 전도성과 열 전도성을 가지며, 이러한 특성 때문에 21세기를 주도해 나갈 수 있는 차세대 첨단 소재로서 각광을 받고 있다. 또한 최근에는 나노공학기술의 발달로 인하여 획기적으로 높은 열전도도를 나타내는 다중벽 탄소나노튜브(Multi-walled Carbon Nanotubes, MWCNTs)의 대량 생산이 가능하게 되면서 다중벽 탄소나노튜브의 높은 열전도도 특성을 이용하여 탄소나노튜브를 기본 유체 및 기능성 유체에 안정하게 분산 시킨 후 이를 이용하고자 하는 연구가 활발히 진행되고 있으며, 탄소나노튜브를 유체에 안정하게 분산시키기 위한 방법으로는 기계적 분산법, 물리적 흡착에 의한 분산법, 화학적 개질에 의한 분산법이 있다. 따라서 본 연구에서는 이들 분산 방법과 탄소나노튜브 입자의 물성치에 따른 나노유체의 특성을 알아보기 위하여 나노유체의 열전도도와 점도 특성을 비교 분석하였다. 모든 물성치는 같지만 탄소나노튜브의 길이만 다른 두 종류의 다중벽 탄소나노튜브에 각각 계면 활성제(Sodium Dodecyl Sulfate, SDS) 100 wt%와 고분자 화합물(Polyvinyl Pyrrolidone, PVP) 300 wt%를 첨가하여 나노유체를 제조하였으며, 산화처리 된 다중벽 탄소나노튜브(Oxidized Multi-Walled Carbon Nanotubes, OMWCNTs)를 증류수에 초음파 분산하여 산화나노유체를 제조하였다. 나노유체의 열전도도는 전기 전도성 유체의 비정상 열선법(Transient Hot-wire Method)을 이용하여 측정하였고, 나노유체의 점도는 회전형 디지털 점도계를 이용하여 측정하였다. 실험 결과, 상온에서 동일 혼합비의 나노유체를 비교했을 때, 산화나노유체가 SDS 100 wt%, PVP 300 wt%를 혼합한 다른 나노유체보다 높은 열전도도 특성을 보였으며 점도 특성 또한 가장 낮은 것으로 측정되었다. 특히 상온에서 0.1vol%의 산화 CM-100 나노유체는 증류수보다 열전도도가 8.34%가 증가하였고, $10^{\circ}C$의 저온에서는 상온에서 증류수와 비교하여 측정된 열전도도 값보다 0.36%가 감소한 7.98%가 증가함을 보였다. 본 연구를 통하여 얻어진 결과는 높은 열전도도를 필요로 하는 열교환기의 작동유체나 기타 활용 분야에 대한 기초 자료로써 유용한 정보를 제공할 것이라 판단된다.

• 한국신재생에너지학회:학술대회논문집
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• 2008.05a
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• pp.445-447
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• 2008

본 연구에서는 다중벽 탄소나노튜브용 표면개질제를 리빙라디칼중합법을 통하여 제조하고, 이를 이용하여 표면개질되고 분산제어된 다중벽탄소나노튜브를 제조하고 염료감응형 태양전지의 대전극 재료로 사용하였다. 우선 리빙라디칼중합법 중 nitroxide mediated polymerization (NMP) 기술을 이용하여 poly(maleic anhydride-co-p-acetoxystyrene)-block-poly(p-acetoxystyrene)를 합성하고, 공중합체중의 maleic anhydride기에 이미드화 반응을 통하여 pyrene기를 도입하였다. 공중합체 중의 p-acetoxystyrene 반복단위들은 가수분해 반응을 통하여 p-hydroxystyrene 반복단위로 변환하였으며, 제조된 공중합체의 구조와 열 특성 등을 GPC, GC, $^1H$-NMR, TGA을 통하여 분석하였다. 제조된 공중합체를 이용하여 다중벽 탄소나노튜브의 표면을 polymer wrapping법으로 처리하였고, 표면개질된 탄소나노튜브의 분산성을 다양한 용매에서 비교분석하였다. 표면이 개질되고 페이스트 내에의 분산성이 향상된 다중벽탄소나노튜브를 염료감응태양전지의 대전극 제조에 응용하였으며, 표면처리 및 분산제어 여부에 따른 제작 특성 및 동작특성 등을 평가하였다.

• Polymer(Korea)
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• v.35 no.6
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• pp.548-552
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• 2011

Two functionalization methods, i.e., acid treatment and chemical amidation were performed to prepare the functionalized multi-walled carbon nanotubes (MWCNT), and the properties of epoxy/functionalized MWCNT composites were investigated and compared. Fourier transform infrared spectroscopy (FTIR) was used to confirm the surface functionality of the MWCNT obtained by the functionalization methods. The effects of the MWCNT functionalization on the interface and thermal conductivity were studied by zeta potential analyzer, scanning electron microscope and thermal conductivity analyzer. From these results, it was confirmed that the thermal conductivity of the epoxy/MWCNT composites could be increased by grafting with dodecylamine. This could be interpreted by relatively strong dispersion forces of the grafting MWCNT with dodecylamine in DGEBF epoxy resin. These results were in good agreement with the results that the zeta potential value of the grafting MWCNT with dodecylamine has a higher negative value than that of MWCNT with acid treatment.

• Journal of the Korean Vacuum Society
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• v.17 no.1
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• pp.67-72
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• 2008

We have studied the effect of heat treatment of multi-walled carbon nanotubes (MWNTs) as a counter electrode on the electro-chemical properties of dye-snsitized solar cells. MWNTs on the p-type Si substrate were synthesized by thermal chemical vapor deposition (CVD) using Fe catalysts. We prepared the two types of MWNTs samples with the different diameters. The rapid thermal annealing (RTA) treatment for the MWNTs was carried out at the growth temperature ($900^{\circ}C$) for 1 minute with $N_2$ gas atmosphere. The structural, electrical and electrochemical properties of MWNTs were investigated by field-emission scanning electron microscopy (FE-SEM), Raman spectroscopy, 2-point probe station and electrochemical impedance spectroscopy (EIS). The I(D)/I(G) ratio of heat-treated MWNTs in Raman spectra was considerably decreased. It was also found that the heat-treated MWNTs showed better redox reaction of iodide at the interface between MWNTs surface and electrolyte than that of as-grown MWNTs. The redox resistance value of heat-treated electrodes was measured to be much lower than that of as-grown electrode at the interface. As a result, the counter electrode using the heat-treated MWNTs showed better electrochemical properties.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.9 no.5
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• pp.1150-1153
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• 2008

The coupled oscillation of multi-walled carbon-nanotube (MWCNT) oscillators consisting of (5n, 5n) CNTs was investigated by molecular dynamics simulations. The results show that the inter-wall coupling leads to frequency splits. And there are consistently three primary frequency peaks for the quadric-walled, penta-walled and hexa-walled CNT oscillators. It is independent of the wall parameters, suggesting applications as triple-frequency generators. Furthermore, at least one of the primary frequencies of a MWCNT oscillator is lower than that of its double-walled counterpart.

• Composites Research
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• v.17 no.3
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• pp.38-44
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• 2004

The electromagnetic interference (EMI) shielding is very essential for commercial and military purposes. We fabricated multi-walled carbon nanotube (MWNT)/epoxy composites and studied the electromagnetic characteristics of the composites before we study the characteristics of MWNT-added glass fiber-reinforced composites. After setting up the fabrication process, we measured the permittivity of MWNT/epoxy composites with process variables and MWNT concentrations in X-band (8.2GHz~12.4GHz). We also observed re-aggregation phenomenon of MWNTs and investigated its effect on the permittivity. The permittivity of the composites was influenced by the degree of dispersion of MWNTs and increased almost linearly as MWNT concentration increases.

• Applied Chemistry for Engineering
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• v.25 no.3
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• pp.268-273
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• 2014

In this study, multi-walled carbon nanotubes (MWCNT) were treated with nickel by electroless plating method for improving electromagnetic interference (EMI) shielding performance of MWCNT. The physical properties of electroless plated MWCNT were analyzed by using ultra-high resolution scanning electron microscope (UHR-SEM), thermogravimetry (TGA), sheet resistance analyzer and EMI shielding analyzer. EMI shielding efficiencies of nickel electroless plated MWCNT were measured to be 16 dB from 800 MHz band, which was 1.6 times increased compared to that of the activated MWCNT. Also, the average sheet resistance of nickel electroless plated MWCNT was measured to be $70{\Omega}/sq$, which was 56% decreased compared to that of the activated MWCNT. This result could be attributed to the plating morphology on the surface of MWCNT. This result could be attributed to uniformity of plating morphology on the surface, which has more effect on EMI shielding efficiency than the amount of nickel plating.

• Composites Research
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• v.17 no.6
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• pp.1-7
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• 2004

The studies of particulate reinforced composites have been conducted for many years. The nanocomposites to be studied vigorously in recent years are one of them. We fabricated and studied multi-walled carbon nanotube(MWNT)/epoxy composites which may be useful as matrix for continuous fiber-reinforced composites. We investigated tensile properties of MWNT/epoxy composites as a function of MWNT concentration, which were prepared by the fabrication method established in this study. Tensile stiffness and strength increased 19% at 0.5 wt% and 12% at 0.2 wt%, respectively. We observed the reaggregation phenomenon of MWNTS during curing, which should be controlled to obtain higher tensile properties.

• Polymer(Korea)
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• v.33 no.5
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• pp.452-457
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• 2009

Hybrid nanomaterials consisting of multi-walled carbon nanotube(MWNT) and/or PEDOT of conductive polymer were prepared in this study. In the presence of catalyst and ligand, the MWNT-Br compound prepared by the successive surface treatment reaction was mixed with MMA to initiate the atom transfer radical polymerization process. PMMA was covalently linked to the surface of MWNT for the formation of MWNT/PMMA nanocomposites. The EDOT and oxidant were added in the aqueous emulsion of PS produced via a miniemulsion polymerization process and then it proceeded to carry out the oxidative chemical polymerization of EDOT for the preparation of PEDOT/PS nanoparticles with the core-shell structure. The aqueous dispersion of PEDOT:poly(styrene sulfonate) (PSS) was mixed with the silica particles treated with a silane compound and thus PEDOT:PSS-clad silica nanoparticles were prepared by the surface chemistry reaction. The hybrid nanomaterials were analyzed by using TEM, FE-SEM, TGA, EDX, UV, and FT-IR.