• 공업화학
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• 제21권1호
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• pp.58-62
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• 2010

$TiOSO_4$와 다층벽탄소나노튜브(MWCNT)를 사용하여 가수분해법으로 CNT-$TiO_{2}$ 나노복합체를 제조하였다. 제조된 $TiO_{2}$-CNT 복합체의 CNT는 아나타제 $TiO_{2}$에 균일하게 분산되어 있으며 MWCNT의 첨가량이 증가함에 따라 결정성 탄소의 비율과 O/Ti 비율이 증가함을 확인할 수 있다. CNT-$TiO_{2}$복합체의 광활성 및 오염물 흡착능력을 UV 조사 시간에 따른 메틸렌블루의 분해정도로 확인하였다. MWCNT의 비율이 높아질수록 높은 흡착능과 광분해능을 나타내었다. 이는 MWCNT의 높은 비표면적, 산소포함 관능기, 낮은 밴드갭 에너지, 높은 전기전도성, 높은 부피 대 표면적 비율, 균일한 구조 및 특성으로 인하여 CNT-$TiO_{2}$ 복합체의 광활성에 도움을 주는 것으로 보인다.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2016년도 제50회 동계 정기학술대회 초록집
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• pp.297.2-297.2
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• 2016

Photoacoustic generation of ultrasound is an effective approach for development of high-frequency and high-amplitude ultrasound transmitters. This requires an efficient energy converter from optical input to acoustic output. For such photoacoustic conversion, various light-absorbing materials have been used such as metallic coating, dye-doped polymer composite, and nanostructure composite. These transmitters absorb laser pulses with 5-10 ns widths for generation of tens-of-MHz frequency ultrasound. The short optical pulse leads to rapid heating of the irradiated region and therefore fast thermal expansion before significant heat diffusion occurs to the surrounding. In this purpose, nanocomposite thin films containing gold nanoparticles, carbon nanotubes (CNTs), or carbon nanofibers have been recently proposed for high optical absorption, efficient thermoacosutic transfer, and mechanical robustness. These properties are necessary to produce a high-amplitude ultrasonic output under a low-energy optical input. Here, we investigate carbon nanotube (CNT)-polydimethylsiloxane (PDMS) composite transmitters and their nanostructure-originated characteristics enabling extraordinary energy conversion. We explain a thermoelastic energy conversion mechanism within the nanocomposite and examine nanostructures by using a scanning electron microscopy. Then, we measure laser-induced damage threshold of the transmitters against pulsed laser ablation. Particularly, laser-induced damage threshold has been largely overlooked so far in the development of photoacoustic transmitters. Higher damage threshold means that transmitters can withstand optical irradiation with higher laser energy and produce higher pressure output proportional to such optical input. We discuss an optimal design of CNT-PDMS composite transmitter for high-amplitude pressure generation (e.g. focused ultrasound transmitter) useful for therapeutic applications. It is fabricated using a focal structure (spherically concave substrate) that is coated with a CNT-PDMS composite layer. We also introduce some application examples of the high-amplitude focused transmitter based on the CNT-PDMS composite film.

• 공업화학
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• 제26권1호
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• pp.40-46
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• 2015

카본나노튜브(CNT)와 폴리아닐린(PANI)과 같은 도전성물질의 서스펜션을 함유한 마이크로캡슐이 멜라민과 포름알데히드의 in situ 중합법에 의해 제조되었다. 평균직경 $10-20{\mu}m$의 안정된 마이크로캡슐이 관찰되었으며, 이 마이크로 캡슐의 표면 모폴로지와 화학구조, 열적특성을 광학현미경, 주사전자현미경(SEM), 적외선 분광분석(FT-IR), 열중량분석(TGA) 등으로 측정하였다. 테트라클로로에틸렌과 아이소파 G (isopar-G) 및 CNT나 PANI로 구성된 도전성물질 서스펜션을 함유한 마이크로캡슐의 전기전도도를 캡슐벽을 깨뜨린 후 측정하였다. 마이크로캡슐의 심물질인 CNT나 PANI의 양이 증가할수록 측정된 전류는 증가하였다. 분쇄된 캡슐의 심물질의 전도도를 측정한 결과는 CNT나 PANI가 캡슐이 깨졌을 때, 빠져나온 심물질인 전도성 물질이 단락된 서킷을 연결해 줄 수 있는, 자기치유형 전자재료 시스템에 폴리 멜라민 포름알데히드 베이스의 코어 쉘(core shell) 마이크로캡슐이 적용 가능한 것을 보여준다.

• 멤브레인
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• 제24권5호
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• pp.358-366
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• 2014

Chitosan에 HNT (halloysite nanotube)의 함량을 0, 3, 5, 10 wt%로 가하여 chitosan-HNT 복합막을 제조하였다. 복합막의 구조는 FT-IR, XRD, TGA, SEM으로 알아보았다. 기체투과 실험은 $30^{\circ}C$, $4kg/cm^2$ 조건에서 수행하였고, chitosan-HNT 복합막의 HNT 함량 변화에 따른 $CO_2$와 $CH_4$의 기체투과도와 선택도를 조사하였다. Chitosan-HNT 복합막의 기체 투과도는 HNT 함량이 3 wt%에서 가장 큰 값을 보였고, 그 이상의 함량에서는 감소하였다. 선택도($CO_2/N_2$)는 0~10 wt% 범위에서 HNT 내의 OH기와 $CO_2$ 간의 친화력으로 인하여 증가하였고, 약 1.3~3.8의 값을 보였다.

• 공업화학
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• 제28권6호
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• pp.601-606
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• 2017

금속 표면처리의 대표적인 기술인 양극산화를 통하여 일차원 나노구조 금속 산화물을 형성할 수 있다. 여러 가지 금속 산화물 중에 기능성이 뛰어난 $TiO_2$에 대한 관심의 증대로 $TiO_2$ 나노 튜브를 이용한 연구가 많이 이루어지고 있다. 본 총설논문에서는 지금까지 연구되어 밝혀진 $TiO_2$ 나노 튜브가 형성원리에 대한 해설논문으로 전기화학적 측면에서의 양극 산화 공정에 대한 이해를 통하여 나노 튜브 형성을 위한 전기적 조건, 화학적 조건, 물리적 조건에 대하여 다루었다. 특히 $TiO_2$ 나노 튜브 성장의 핵심 요소인 산화물의 형성과 에칭의 평형관계, 다공성 구조의 형성 원인을 다루었다. 나아가 전해질 조건에 따른 $TiO_2$ 나노 튜브의 형태학적 고찰을 함으로써 향후 양극 산화를 통한 $TiO_2$ 나노 튜브 응용에 관한 연구를 하는 연구자에게 이해하기 쉽게 설명하고자 하였다.

• Composites Research
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• 제24권6호
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• pp.1-6
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• 2011

본 연구에서는 탄소나노튜브를 물상에서 균일하게 분산시키기 위하여 물에 녹으면서 분자 내에서 자체 도핑이 가능한 새로운 종류의 그래프트 공중합체(PSSA-g-PANI, poly(styrenesulfonic acid-graft-aniline))를 합성하였고, 그 분산 능력을 실험해 보았다. PANI 고분자는 벤조이드와 퀴노이드 구조가 반복되어 존재하는 판상구조로 탄소나노튜브와 같은 탄소나노 소재의 벽에 강하게 결합할 수 있고, 따라서 짧은 시간의 sonication 처리 만으로 나노튜브를 분산시킬 수 있었고 그 분산 용액의 장시간 안정성은 다른 상용화된 분산제보다 뛰어났다. 또한 PSSA-g-PANI 그래프트 고분자/탄소나노튜브 복합 필름은 대략 1.5-2.5 S/cm의 전도도를 기록하였다.

• 한국표면공학회지
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• 제49권2호
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• pp.218-224
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• 2016

Thermal radiation pastes were prepared by dispersing carbon materials as fillers with a content of 1 weight percent in an acrylic resin. The kind of fillers was as follows; $25{\mu}m$ graphite, $45{\mu}m$ graphite, $15{\mu}m$ carbon nanotube(CNT), a 1:1 mixture of $25{\mu}m$ graphite and $15{\mu}m$ CNT, and a 1:1 mixture of $45{\mu}m$ graphite and $15{\mu}m$ CNT. Thermal emissivity was measured as 0.890 for the samples with graphite only, 0.893 for that with CNT only, and 0.892 for those containing both. After coating prepared pastes on a side of 0.4 mm thick aluminium plate and placing the plate over an opening of a box maintained at $92^{\circ}C$ with the coated side out, the temperatures on the uncoated side of the plates were measured. The samples containing graphite and CNT showed the lowest temperatures. The paste with mixed fillers was coated on the back side of the PCB of an LED module and thermal analysis was carried out using Thermal Transient Tester (T3ster) in a still air box. The thermal resistance of the module with coated PCB was measured as 14.34 K/W whereas that with uncoated PCB was 15.02 K/W. The structure function analysis of T3ster data revealed that the difference between junction and ambient temperatures was $13.8^{\circ}C$ for the coated case and $18.0^{\circ}C$ for the uncoated. From the infrared images of heated LED modules, the hottest-spot temperature of the module with coated PCB was lower than that of the uncoated one for a given period of LED operation.

• 한국재료학회지
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• 제20권3호
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• pp.117-124
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• 2010

Titanium dioxide ($TiO_2$) particles deposited on different quantitative Fe-treated carbon nanotube (CNT) composites with high photocatalytic activity of visible light were prepared by a modified sol-gel method using TNB as a titanium source. The composites were characterized by BET, XRD, SEM, TEM and EDX, which showed that the BET surface area was related to the adsorption capacity for each composite. From TEM images, surface and structural characterization of for the CNT surface had been carried out. The XRD results showed that the Fe-ACF/$TiO_2$ composite mostly contained an anatase structure with a Fe-mediated compound. EDX results showed the presence of C, O, and Ti with Fe peaks in the Fe-CNT/$TiO_2$ composites. The photocatalytic activity of the composites was examined by degradation of methylene blue (MB) in aqueous solution under visible light, which was found to depend on the amount of CNT. The highest photocatalytic activity among the different composites was related to the optimal content of CNT in the Fe-CNT/$TiO_2$ composites. In particular, the photocatalytic activity of the Fe-CNT/$TiO_2$ composites under visible light was better than that of the CNT/$TiO_2$ composites due to the introduction of Fe particles.

• 한국환경과학회지
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• 제27권11호
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• pp.967-974
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• 2018

In this study, we evaluated the photocatalytic oxidation efficiency of aromatic volatile hydrocarbons by using $WO_3$-doped $TiO_2$ nanotubes (WTNTs) under visible-light irradiation. One-dimensional WTNTs were synthesized by ultrasonic-assisted hydrothermal method and impregnation. XRD analysis revealed successful incorporation of $WO_3$ into $TiO_2$ nanotube (TNT) structures. UV-Vis spectra exhibited that the synthesized WTNT samples can be activated under visible light irradiation. FE-SEM and TEM images showed the one-dimensional structure of the prepared TNTs and WTNTs. The photocatalytic oxidation efficiencies of toluene, ethylbenzene, and o-xylene were higher using WTNT samples than undoped TNT. These results were explained based on the charge separation ability, adsorption capability, and light absorption of the sample photocatalysts. Among the different light sources, light-emitting-diodes (LEDs) are more highly energy-efficient than 8-W daylight used for the photocatalytic oxidation of toluene, ethylbenzene, and o-xylene, though the photocatalytic oxidation efficiency is higher for 8-W daylight.

• 대한금속재료학회지
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• 제46권11호
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• pp.730-736
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• 2008

$TiO_2$ nanotubes fabricated in aqueous HF-based electrolytes have been generally grown only to about 500nm in length because of the strong dissolubility of HF acid. In this paper, ethylene glycol solution has been applied for increasing the length of the anodic $TiO_2$ nanotubes, and the growth behaviors of the nanotubes according to water contents has been investigated. Anodization of Ti in ethylene glycol + 1 wt% $NH_4F$ (EG solution) with water additions up to 10 wt% were carried out at the constant voltage of 20 V. The results show that a thin titanium oxide layer is formed in the initial stage and the nanotube structure grows underneath the initial layer. And the length of $TiO_2$ nanotubes decreases with the increasing water content in the solution. It can be ascribed to the locally acidified circumstance around the barrier layer inside the nanopore due to $H^+$ ion originated from water. The XPS for the nanotubes suggests that the spectra of Ti2p and O1s are the major chemical bonding states of the $TiO_2$, and those for F1s, N1s and C1s come from the compound of $(NH_4)_2TiF_6$.