• Korean Journal of Optics and Photonics
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• v.15 no.5
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• pp.449-454
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• 2004

The optical limiter is an optical component which reduces laser beam intensity for the protection of eyes and light sensors. Carbon nanotube is now known as a highly efficient optical limiting material. Optical limiting effect of the multi-walled carbon nanotube suspensions, in several kinds of solvents such as distilled water, chloroform, ethanol and ethylene glycol, were measured in the range from room temperature to near to the boiling points of the solvents. The pulsed Nd:YAG laser whose wavelength is 1064 nm and pulse duration is 6 ns was used as a light source. The experimental result shows that the limiting efficiency was reduced as the temperature increased, and the suspension which has lower boiling point, viscosity and surface tension has highest efficiency.

• Journal of Energy Engineering
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• v.20 no.3
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• pp.209-215
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• 2011

In this study, for efficiency enhancement of low temperature heat exchanger, the thermal conductivity and the viscosity of carbon nanofluids and oxidized carbon nanofluids were measured at $10^{\circ}C$ and $25^{\circ}C$, respectively. Carbon nanofluids were made by ultrasonic-dispersing ones in distilled water after Multi-Walled Carbon Nanotubes (MWCNTs) mixed Sodium Dodecyl Sulfate (SDS, 100 wt%), Polyvinyl pyrrolidone (PVP, 300 wt%) each. Oxidized carbon nanofluids were made by ultrasonic-dispersing Oxidized Carbon Nanotubes (OMWCNTs) in distilled water. The thermal conductivity of carbon nanofluids was measured by using a transient hot-wire method. The viscosity was measured by using a digital viscometer. As a result, the thermal conductivity of oxidized carbon nanofluids was the highest of those compared and the other carbon nanofluids at the same mixture ratio and temperature, and the viscosity was measured the lowest of those compared and the other carbon nanofluids.

• Composites Research
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• v.37 no.1
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• pp.32-39
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• 2024

Solid-state hydrogen storage is gaining prominence as a crucial subject in advancing the hydrogen-based economy and innovating energy storage technology. This storage method shows superior characteristics in terms of safety, storage, and operational efficiency compared to existing methods such as compression and liquefied hydrogen storage. In this study, we aim to evaluate the solid hydrogen storage performance on the nanotube surface by various structural design factors. This is accomplished through molecular dynamics simulations (MD) with the aim of uncovering the underlying ism. The simulation incorporates diverse carbon nanotubes (CNTs) - encompassing various diameters, multi-walled structures (MWNT), single-walled structures (SWNT), and boron-nitrogen nanotubes (BNNT). Analyzing the storage and effective release of hydrogen under different conditions via the radial density function (RDF) revealed that a reduction in radius and the implementation of a double-wall configuration contribute to heightened solid hydrogen storage. While the hydrogen storage capacity of boron-nitrogen nanotubes falls short of that of carbon nanotubes, they notably surpass carbon nanotubes in terms of effective hydrogen storage capacity.

• Proceedings of the Korean Vacuum Society Conference
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• 2016.02a
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• pp.383.1-383.1
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• 2016

열전달 시스템에서 임계 열유속 발생 시 시스템의 물리적 손상을 야기하기 때문에 비등 열전달에서 임계 열유속은 열전달 시스템의 한계 또는 안전성을 나타낸다. 따라서 열전달 시스템의 안정성을 위해서는 임계 열유속 향상이 필수적이다. 최근에는 나노유체를 열전달 시스템에 적용할 경우 임계 열유속이 증가한다고 보고되었다. 하지만 나노유체는 원전 및 각종 열전달 시스템에 적용 시 나노입자가 열전달 표면에 침착되는 파울링 현상을 발생시킬 수 있으며, 이 때문에 시스템의 열효율이 크게 감소할 수 있다. 따라서 본 연구에서는 열전달 시스템에 나노유체를 적용했을 때, 나노유체의 침착현상이 시스템에 미치는 영향을 분석하였다. 그 결과 유속과 코팅시간이 증가할수록 산화처리된 다중벽 탄소나노튜브 나노유체의 임계 열유속이 크게 증가하고 있음을 확인할 수 있다. 하지만 나노입자 침착정도와 유속이 증가할수록 비등 열전달 표면과 유체의 포화온도의 차이인 과열도가 상당히 크게 증가함을 알 수 있었으며, 열전달 계수는 순수 물의 0 m/s의 비등 열전달 계수와 비교하면 감소하는 것을 확인하였다.

• 한국신재생에너지학회:학술대회논문집
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• 2011.05a
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• pp.160-160
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• 2011

In this work, magnesium (Mg) nanoparticles were plated onto the surfaces of multi-walled carbon nanotubes (MWNTs) in order to investigate the effects of their presence on the high pressure hydrogen storage behaviors of the resultant Mg/MWNTs. The structure of Mg/MWNTs was characterized by X-ray diffraction (XRD) and transmission electron microscopy (TEM). The pore structure and total pore volumes of Mg/MWNTs were analyzed by $N_2$/77 K adsorption isotherms. The hydrogen storage behaviors of the Mg/MWNTs were investigated by BEL-HP at 298K and 100 bar. From the results, it was found that Mg particles were homogeneously distributed on the MWNT surfaces. The hydrogen storage capacity increased in proportion to the Mg content. It can be concluded that Mg paricles play an important role in hydrogen storage characteristics due to the hydrogen spillover effect.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2006.05a
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• pp.465-466
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• 2006

A single-wall carbon nanotube (SWCNT) has been studied as a material of Nano-Eletro-Mechanical-System (NEMS) device together with various nanowires. In order for oscillation of a multi-wall carbon nanotube (MWCNT) or a single-walled carbon nanotube (SWCNT) on plane surface, it needs suspension of a CNT across trench electrodes. So we propose fabrication method of a MWCNT resonator using dielectrophoresis and show successful results of suspeneded MWNT. Thin electrodes with large gaps could not suspend small diameter MWNT but thicker electrodes could. Thin MWNT could be suspended only when the electrode gap was reduced.

• Journal of Korean Society of Environmental Engineers
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• v.34 no.11
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• pp.757-764
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• 2012

The surface of graphite fiber fabric anode was modified with a hydrogel and a mixture of hydrogel and multiwall carbon nanotube, and their effectiveness were compared to the unmodified anodes in a batch microbial fuel cell (microbial fuel cells). The maximum power density of the MFC was determined by both performance of the anode and cathode. The maximum power density for the MFC with the anode modified with the mixture of hydrogel and multiwall carbon nanotube was $1,162mW/m^2$ which was 27.7% higher than that with the unmodified graphite fiber fabric anode. "The mixture of hydrogel and multiwall carbon nanotube is a good surface modifier for anode with high biological affinity and low activation losses."

• Journal of the Korean Vacuum Society
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• v.17 no.4
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• pp.365-373
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• 2008

We have succeeded in synthesizing vertically aligned thin multi-walled carbon nanotubes (VA thin-MWCNTs) by a catalytic chemical vapor deposition (CCVD) method onto Fe/Al thin film deposited on a Si wafers using an optimum amount of hydrogen sulfide ($H_2S$) additive. Scanning electron microscope (SEM) images revealed that the as-synthesized CNT arrays were vertically well-oriented perpendicular to the substrate with relatively uniform length. Transmission electron microscope (TEM) observations indicated that the as-grown CNTs were nearly catalyst-free thin-MWCNTs with small outer diameters of less than 10nm. The average wall number is about 5. We suggested a possible growth mechanism of the VA thin-MWCNT arrays. The VA thin-MWCNTs showed a low turn-on electric field of about $1.1\;V/{\mu}m$ at a current density of $0.1\;{\mu}A/cm^2$ and a high emission current density about $2.5\;mA/cm^2$ at a bias field of $2.7\;V/{\mu}m$. Moreover, the VA thin-MWCNTs presented better field emission stability without degradation over 20 hours (h) at the emission current density of about $1\;mA/cm^2$.

• Journal of the Korean Vacuum Society
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• v.12 no.4
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• pp.281-287
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• 2003

We have performed classical molecular dynamics simulations for hypothetical silicon nanotubes using the Tersoff potential. Our investigation presented a systematic study about the thermal behavior of hypothetical silicon nanotubes and showed the difficulty in Producing silicon nanotubes or graphitelike sheets. Through the investigations on the structure and properties of a double-wall silicon nanotube, we concluded that quasi-one dimensional structures consisting of silicon atoms become nanowires or multi wall nanotubes rather than single wall nanotubes in order to minimize the number of $sp^2$ bonds.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.11 no.7
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• pp.2713-2718
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• 2010

To improve the CNT's dispersion, we tried to chemically modify the surface of MWNT with the butyllithium and the hexyllithium solution in sonicated reactor. The functionalized-MWNTs were characterized by Fourier transform infrared spectrometer(FT-IR) and Raman spectrophotometer. Also, we investigated the amount of alkyl moiety incorporated into MWNT's surface with Thermal gravimetric analyzer(TGA) and dispersibility in various organic solvents. Finally, we could find organic content was about 5% of the functionalized MWNT and dispersibility was enhanced in some solvents having intermediate solubility parameter.