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Vertically-aligned carbon nano-tube membrane filters with superhydrophobicity and superoleophilicity
Lee, Cheesung,Baik, Seunghyun Elsevier 2010 Carbon Vol.48 No.8
<P><B>Abstract</B></P><P>A membrane filter possessing both superhydrophobicity and superoleophilicity is of great interest for the possible separation of oil and water. Such a filter was realized in this study by synthesizing vertically-aligned multi-walled carbon nano-tubes on a stainless steel mesh. The dual-scale structure, nano-scale needle-like tubes on the mesh with micro-scale pores, combined with the low surface energy of carbon amplified both hydrophobicity and oleophilicity. For the tests, diesel was selected as a representative of low viscosity oils. The contact angles for diesel and water were 0° and 163±4°. The nano-tube filter could separate diesel and water layers, and even surfactant-stabilized emulsions. The successful phase separation of the high viscosity lubricating oil and water emulsions was also carried out. The separation mechanism can be readily expanded to a variety of different hydrophobic and oleophilic liquids. The simple nano-tube filter might be practically employed in environmental and chemical separation processes including oil spill cleanup.</P>
열화학기상증착법을 이용한 세장비가 긴 탄소나노튜브 어레이 합성 및 유수 분리필터 응용
이치성(Cheesung Lee),윤도경(Dokyung Yoon),윤종주(Jongju Yun),백승현(Seunghyun Baik) 한국생산제조학회 2011 한국생산제조시스템학회 학술발표대회 논문집 Vol.2011 No.4
We have investigated the effects of catalyst layers (Fe/Al2O3) on the growth of vertically aligned carbon nanotubes (CNTs) synthesized by thermal chemical vapor deposition to control the length, diameter, and alignment of CNTs. We produced vertically aligned CNTs more than several millimeters in length under the optimized conditions. Also we have demonstrated that vertically aligned multi-walled CNTs synthesized on a stainless steel mesh could be utilized as an oil-water separation membrane filter, having both superhydrophobicity and superoleophilicity.
Yoon, Dokyung,Lee, Cheesung,Yun, Jongju,Jeon, Wonjae,Cha, Bong Jun,Baik, Seunghyun American Chemical Society 2012 ACS NANO Vol.6 No.7
<P>The separation of gas molecules and water vapor has become increasingly important for electronic, energy, and environmental systems. Here we demonstrate a new mechanism of enhanced condensation, agglomeration, and rejection of water vapor by superhydrophobic aligned multiwalled carbon nanotubes with the intertube distance of 73 nm, channel aspect ratio of ~5.5 ?? 10(4), and tortuosity of 1.157. The array with the characteristic channel dimension some 300 times greater than the target molecule size effectively suppressed water molecular transport at room temperature with the selectivity as high as ~2 ?? 10(5) (H(2)/H(2)O). The flow through the interstitial space of nanotubes allowed high permeability of other gas molecules (2.1 ?? 10(-9) to 3.8 ?? 10(-8) mol · m/m(2) · s · Pa), while retaining high selectivity, which is orders of magnitude greater than the permeate flux of polymeric membranes used for the water-gas mixture separation. This new separation mechanism with high selectivity and permeate flux, enabled by the unique geometry of aligned nanotubes, can provide a low-energy and cost-effective method to control humidity.</P>
Yun, Jongju,Lee, Cheesung,Zheng, Qing,Baik, Seunghyun American Scientific Publishers 2012 Journal of Nanoscience and Nanotechnology Vol.12 No.8
<P>We synthesized vertically-aligned multi-walled carbon nanotubes with an inner diameter of 1.6-7.5 nm and stack height of 80-28600 microm by chemical vapor deposition. The effects of synthesis conditions such as substrate position in the tube furnace, maximum temperature, temperature increasing rate and synthesis duration on the structure of nanotubes were investigated. It was found that slightly faster temperature increase rate resulted in significantly longer length, larger diameter and more defects of nanotubes. Structural parameters such as inner, outer diameters, wall thickness and defects were investigated using transmission electron microscopy and Raman spectroscopy.</P>
Hyeongkeun Kim,Cheesung Lee,최재붕,전경용,김영진,백승현 한국물리학회 2009 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.54 No.3
The effects of sandwich-like catalysts on the vertical growth of multiwalled carbon nanotubes (MWCNTs) are investigated. We achieved the synthesis of 2.2-mm-long MWCNT forests with carefully designed catalyst films by thermal chemical vapor deposition. Two types of sandwich-like catalysts were prepared by electron beam evaporation. Fe and Al2O3 layers were deposited on a SiO2 surface of 300 nm in thickness. Here, Fe and Al2O3 were used for the catalyst and the supporting buffer layer, respectively. C2H4 was used as a carbon source while Ar and H2 were used as carrier gases. The sandwich-like catalyst supported by a buffer layer of Al2O3 significantly enhanced the quality of the CNTs. The termination of MWCNT growth was found to depend on the position of the Fe layer. Also, the type of sandwich-like catalyst affects the crystalline perfection of the MWCNTs.