• 한국세라믹학회지
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• 제40권12호
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• pp.1150-1153
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• 2003

Carbon nanofilaments were formed on silicon substrate using microwave plasma-enhanced chemical vapor deposition method. The structures of carbon nanofilaments were identified as carbon nanotubes or carbon nanofibers. The formation of bamboo-like carbon nanotubes was initiated by the application of the bias voltage during the plasma reaction. The growth kinetics of bamboo-like carbon nanotubes increased with increasing the bias voltage. The growth direction of bamboo-like carbon nanotubes was vertical to the substrate.

• 대한화학회지
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• 제47권6호
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• pp.659-662
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• 2003

• Carbon letters
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• 제11권3호
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• pp.184-191
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• 2010

Carbon nanotubes are unique tubular structures of nanometer diameter and large length/diameter ratio. The nanotubes may consist of one up to tens and hundreds of concentric shells of carbons with adjacent shells separation of ~0.34 nm. Multiwalled carbon nanotubes were synthesized by arc-discharge technique. MWCNTs were formed at the cathode deposit along with other carbonaceous materials like amorphous carbon, graphite etc. However, to get the best advantage of carbon nanotubes in various advanced applications, these undesired carbonaceous materials to be removed which is a challenging task. In the present study, various techniques were tried out for purifying MWCNTs such as physical filtration, chemical treatment and thermal annealing. SEM, FTIR, TGA and BET techniques were used to characterize the CNTs at various stages. Results shows that suitable chemical treatment followed by thermal annealing under controlled flow of oxygen gives the better route for purification of carbon nanotubes.

• 한국복합재료학회:학술대회논문집
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• 한국복합재료학회 2004년도 춘계학술발표대회 논문집
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• pp.165-168
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• 2004

Carbon nanotube is a geometrical frame-like structure and the primary bonds between two nearest-neighboring atoms act like beam members, whereas an individual atom acts as the joint of the related beam members. The sectional property parameters of these beam members are obtained from molecular mechanics. Computations of the elastic deformation of single-walled carbon nanotubes reveal that the Young's moduli of carbon nanotubes vary with the tube diameter and are affected by their helicity. With increasing tube diameter, the Young's moduli of carbon nanotubes approach the Young's modulus of graphite.

• 한국결정성장학회지
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• 제16권1호
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• pp.20-24
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• 2006

Iridium-catalyzed carbon nanofilaments were formed on MgO substrate as a function of the gap between the substrate and the plasma using microwave plasma-enhanced chemical vapor deposition method. Under the remote plasma condition, carbon nanofibers were formed on the substrate. Under the adjacent plasma condition, on the other hand, carbon nanotubes-like materials instead of carbon nanofibers could be formed. When the substrate immersed into the plasma, any carbon nanofilaments formation couldn't be observed. During the reaction, the substrate temperatures were measured as a function of the gap. Based on these results, the cause for the different carbon nanofilaments formation according to the gap was discussed.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2000년도 제18회 학술발표회 논문개요집
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• pp.64-64
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• 2000

Since its discovery in 1991, the carbon nanotube has attracted much attention all over the world; and several method have been developed to synthesize carbon nanotubes. According to theoretical calculations, carbon nanotubes have many unique properties, such as high mechanical strength, capillary properties, and remarkable electronical conductivity, all of which suggest a wide range of potential applications in the future. Here we report the synthesis in the catalytic decomposition of acetylene at ~65 $0^{\circ}C$ over Ni deposited on SiO2, For the catalyst preparation, Ni was deposited to the thickness of 100-300A using effusion cell. Different approaches using porous materials and HF or NH3 treated samples have been tried for synthesis of carbon nanotubes. It is decisive step for synthesis of carbon nanotubes to form a round Ni particles. We show that the formation of round Ni particles by heat treatment without any pre-treatment such as chemical etching and observe the similar size of Ni particles and carbon nanotubes. Carbon nanotubes were synthesized by chemial vapour deposition ushin C2H2 gas for source material on Ni coated Si substrate. Ni film gaving 20~90nm thickness was changed into Ni particles with 30~90nm diameter. Heat treatment of Ni fim is a crucial role for the growth of carbon nanotube, High-resolution transmission electron microscopy images show that they are multi-walled nanotube. Raman spectrum shows its peak at 1349cm-1(D band) is much weaker than that at 1573cm-1(G band). We believe that carbon nanotubes contains much less defects. Long carbon nanotubes with length more than several $\mu$m and the carbon particles with round shape were obtained by CVD at ~$650^{\circ}C$ on the Ni droplets. SEM micrograph nanotubes was identified by SEM. Finally, we performed TEM anaylsis on the caron nanotubes to determine whether or not these film structures are truly caron nanotubes, as opposed to carbon fiber-like structures.

• 한국재료학회지
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• 제22권5호
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• pp.237-242
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• 2012

We report on the NO gas sensing properties of Al-doped zinc oxide-carbon nanotube (ZnO-CNT) wire-like layered composites fabricated by coaxially coating Al-doped ZnO thin films on randomly oriented single-walled carbon nanotubes. We were able to wrap thin ZnO layers around the CNTs using the pulsed laser deposition method, forming wire-like nanostructures of ZnO-CNT. Microstructural observations revealed an ultrathin wire-like structure with a diameter of several tens of nm. Gas sensors based on ZnO-CNT wire-like layered composites were found to exhibit a novel sensing capability that originated from the genuine characteristics of the composites. Specifically, it was observed by measured gas sensing characteristics that the gas sensors based on ZnO-CNT layered composites showed a very high sensitivity of above 1,500% for NO gas in dry air at an optimal operating temperature of $200^{\circ}C$; the sensors also showed a low NO gas detection limit at a sub-ppm level in dry air. The enhanced gas sensing properties of the ZnO-CNT wire-like layered composites are ascribed to a catalytic effect of Al elements on the surface reaction and an increase in the effective surface reaction area of the active ZnO layer due to the coating of CNT templates with a higher surface-to-volume ratio structure. These results suggest that ZnO-CNT composites made of ultrathin Al-doped ZnO layers uniformly coated around carbon nanotubes can be promising materials for use in practical high-performance NO gas sensors.

• Carbon letters
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• 제13권4호
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• pp.248-253
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• 2012

Dielectrophoretic filtering and alignment of single-walled carbon nanotubes (SWCNTs) were tested using deuterium oxide as a solvent. A solution of deuterium oxide-SWCNTs was dropped on top of a silicon chip and an ac electric field was applied between pre-defined electrodes. Deuterium oxide was found to be a better solvent than hydrogen oxide for the dielectrophoresis process with higher efficiency of filtering. This was demonstrated by comparing Raman spectra measured on the initial solution with those measured on the filtered solution. We found that the aligned nanotubes along the electric field were not deposited on the substrate but suspended in solution, forming chain-like structures along the field lines. This so-called pearl chain formation of CNTs was verified by electrical measurements through the aligned tubes. The solution was frozen in liquid nitrogen prior to the electrical measurements to maintain the chain formation. The current-voltage characteristics for the sample demonstrate the existence of conduction channels in the solution, which are associated with the SWCNT chain structures.

• 한국재료학회지
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• 제12권6호
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• pp.458-463
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• 2002

Carbon nanotubes were synthesized at various conditions using Ni-catalytic thermal chemical vapor deposition method and their characteristic properties were investigated by SEM, TEM and Raman spectroscopy. Carbon nanotubes were formed on very fine Ni-catalytic particles. The carbon nanotubes synthesized by thermal decomposition of acetylene at $700^{\circ}C$ had a coiled shape, while those synthesized at $850^{\circ}C$ showed a curved and Y-shape having a bamboo-like morphology. It was found that the carbon nanotube was also made on the fine Ni-catalytic particles formed on the surface of 100~400nm sized large ones after pretreatment with $NH_3$.ber composites show the high dielectric constant and large conduction loss which is increased with anisotropy of fiber arrangement. It is, therefore, proposed that the glass and carbon fiber composites can be used as the impedance transformer (surface layer) and microwave reflector, respectively. By inserting the foam core or honeycomb core (which can be treated as an air layer) between glass and carbon fiber composites, microwave absorption above 10 dB (90% absorbance) in 4-12 GHz can be obtained. The proposed fiber composites laminates with sandwitch structure have high potential as lightweight and high strength microwave absorbers.

• Carbon letters
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• 제15권2호
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• pp.77-88
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• 2014

Double walled carbon nanotubes (DWCNTs) are considered an ideal model for studying the coupling interactions between different concentric shells in multi-walled CNTs. Due to their intrinsic coaxial structures they are mechanically, thermally, and structurally more stable than single walled CNTs. Geometrically, owing to the buffer-like function of the outer tubes in DWCNTs, the inner tubes exhibit exciting transport and optical properties that lend them promise in the fabrication of field-effect transistors, stable field emitters, and lithium ion batteries. In addition, by utilizing the outer tube chemistry, DWCNTs can be useful for anchoring semiconducting quantum dots and also as effective multifunctional fillers in producing tough, conductive transparent polymer films. The inner tubes meanwhile preserve their excitonic transitions. This article reviews the synthesis of DWCNTs, their electronic structure, transport, and mechanical properties, and their potential uses.