• Fibers and Polymers
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• v.5 no.3
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• pp.198-203
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• 2004

Composite films were prepared by casting the solution of polyacrylonitrile (PAN) and single wall nanotube (SWNT) in DMF subsequent to sonication. The SWNTs in the films are well dispersed as ropes with 20-30 nm thickness. Moreover, AFM surface image of the composite film displays an interwoven fibrous structure of nanotubes which may give rise to conductive passways and lead to high conductivity. The polarized Raman spectroscopy is an ideal characterization technique for identification and the orientation study of SWNT. The well-defined G-peak intensity at 1580 $cm^{-1}$shows a dependency on the draw ratio under cross-Nicol. The degree of nanotube orientation in the drawn film was measurable from the sine curve obtained by rotating the drawn film on the plane of cross-Nicol of polarized Raman microscope. The threshold loading of SWNT for electrical conductivity in PAN is found to be lower than 1 wt% in the composite film. The electrical conductivity of the SWNT/PAN composite film decreased with increasing of draw ratio due to the collapse of the interwoven fibrous network of the nanotubes with uniaxial orientation.

• Journal of Information Display
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• v.7 no.2
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• pp.16-21
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• 2006

The effect of improvement on the surface morphology of screen-printed carbon nanotube (CND) films was studied by using the optically clear poly-dimethylsiloxane (PDMS) elastomer for surface treatment. After the PDMS activation treatment was applied to the diode-type CNT cathode, the entangled carbon nanotube (CNT) bundles were broken up into individual free standing nanotubes to remarkably improve the field-emission characteristics over the as-deposited CNT film. Also, the cathode film morphology of a top gated triode-type structure can be treated by using the proposed surface treatment technique, which is a low-cost process, simple process. The relative uniform emission image showed high brightness with a high anode current. This result shows the possibility of using this technique for surface treatment of large-size field emission displays (FEDs) in the future.

• Journal of Electrochemical Science and Technology
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• v.7 no.1
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• pp.76-81
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• 2016

An anatase TiO₂ nanotube array (NTA) was fabricated by anodization and successive heat treatments. When the anatase TiO₂ NTA was cathodically polarized, its color changed to blue, and it could be used as an electrochemically active anode for an oxygen evolution reaction (OER) in alkaline water electrolysis. The structure of the blue anatase TiO₂ NTA was controlled by the anodization conditions and its catalytic activity increased with an increase of the surface area. The activity of the blue anatase TiO₂ NTA gradually reduced with the continued OER because of the partial oxidation of Ti³⁺ to Ti⁴⁺. However, an intermittent cathodic regeneration process could significantly slow its reduction rate. The blue anatase TiO₂ NTA could be an alternative anode for alkaline water electrolysis.

• Tribology and Lubricants
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• v.36 no.5
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• pp.290-296
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• 2020

When two layers of carbon nanotube (CNT) arrays are loaded to mate, the free ends of individual CNTs come into contact at the interface of the two layers. This leads to a higher contact resistance due to a smaller contact region. However, when the free CNT ends of one array penetrate into the mating array, the contact region increases, effectively lowering the contact resistance. To explore the penetration of mating CNTs, we perform molecular dynamic simulations of a simple unit cell model, incorporating four CNTs in the lower array layer coupled with a single moving CNT on the upper layer. The interaction with neighboring CNTs is modelled by long-range carbon bond order potential (LCBOP I). The model structure is optimized by energy minimization through the conjugate gradient method. A NVT ensemble is used for maintain a room temperature during simulation. The time integration is performed through the velocity-Verlet algorithm. A significant vibrational motion of CNTs is captured when penetration is not available, resulting in a specific vibration mode with a high frequency. Due to this vibrational behavior, the random behaviors of CNT motion for predicting the penetration are confirmed under the specific gap distances between CNTs. Thus, the probability of penetration is examined according to the gap distance between CNTs in the lower array and the aspect ratio of CNTs. The penetration is significantly affected by the vibration mode due to the van der Waals forces between CNTs.

• Korean Journal of Materials Research
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• v.20 no.2
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• pp.104-110
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• 2010

The characteristics of all polymer composites containing carbon materials are determined by four factors: component properties, composition, structure and interfacial interactions. The most important filler characteristics are particle size, size distribution, specific surface area and particle shape. As a consequence, in this paper we discuss the aspects of the mechanical, electrical and thermal properties of composites with different fillers of carbon black, carbon nanotube (CNT), graphene and graphite and focus on the relationship between factors and properties, as mentioned above. Accordingly, we fabricate rubber composites that contain various carbon materials in carbon black-based and silica based-SBR matrixes with dual phase fillers and use scanning electron microscopy, Raman spectroscopy, a rhometer, an Instron tensile machine, and a thermal conductivity analyzer to evaluate composites' mechanical, fatigue, thermal, and electronic properties. In mechanical properties, hardness and 300%-modulus of graphene-composite are sharply increased in all cases due to the larger specific surface. Also, it has been found that the thermal conductivity of the CNT-composite is higher than that of any of the other composites and that the composite with graphene has the best electrical properties.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.61 no.7
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• pp.1001-1006
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• 2012

This paper presents a carbon nanotube (CNT) triode-structure field emitter as an ion source in a micro time-of-flight mass spectrometer(TOF-MS). In the ion source by field emission, the electrons emitted from cathodes under an electric field accelerated to the anode and ionize gas molecules by impact before arriving the anode. The generated positive ions are to be accelerated to the ion collector. Whereas most of ions are drawn to the cathodes in diode field emitters, a grid in the triode field emitter prevents the ions from being drawn to the cathodes. The triode field emitter is fabricated by micromachining. The cathode is composed of six CNT cylinders. The total size of the fabricated device is $8.0{\times}7.3{\times}1.9mm^3$. The anode and the grid current of the fabricated CNT field emitter were measured for various anode and grid voltages. When the anode and the grid voltages are 1000 V and 990 V, respectively, the emission current passing through the ionization region is 8.6 ${\mu}A$, which is a sufficient emission current for ionization and mass spectrometry.

• Proceedings of the Korean Vacuum Society Conference
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• 2000.02a
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• pp.213-213
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• 2000

Direct laser vaporization of transition-metal(Co, Ni)/graphite composite pellet produced single wall carbon naotubes(SWNT) in the condensing vapor in a heated flow cylinder-type tube furnace, Transition metal/graphite composite pellet target was made by mixing graphite, Co, and Ni in 98:1:1 atomic weight ratios, pressing the mixed powder, and curing it. The target was placed in a tube furnace maintained at 1200$^{\circ}C$ and Ar inert collision gas continuously flowed into the tube. The 2nd harmonic, 532nm wavelength light from Nd-YAG laser was used to vaporize the tube. The carbon nanotubes produced by the laser vaporization were accumulated on quartz tube wall. The raw carbon nanotube materials were purified with surfactants(Triton X-100) in a ultrasonicator. These carbon nanotubes were analyzed using SEM, XRD, and Raman spectroscopic method. The carbon nanotube growth on the Ni-patterned Si substrate was investigated by the CVD process. Transition-metal, Ni and CH4 gas were used as a catalyst and a reactant gas, respectively. The structure and the phonon frequencies of the carbon nanotubes formed on the patterned Si substrate were measured by SEM and Raman spectrometer.

• Journal of Environmental Science International
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• v.32 no.6
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• pp.477-482
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• 2023

Halloysite nanotube (HNT) has a nanotube structure with the chemical formula of Al₂Si₂O₅(OH)₄ · nH₂O and is a natural sediment of aluminosilicate. A lot of research has been conducted to improve the mechanical properties of epoxy composites by generating interactions between HNTs and polymers through surface treatment of HNTs, such as exchange of amine group as a terminal functional group. However, most of the surface modification methods are performed under wet conditions, which require a relatively large amount of time, manpower and solvent. In order to save time and simplify complicated procedures, a dry coating machine was designed and used for amine group exchange. Comparing the XPS results, it was found that the results of NH₂-HNT prepared using a dry coating machine and the substitution through the wet method were not significantly different, and it has been confirmed that the amount of solvent used and the time savings can be made.

• Journal of the Korean Society of Industry Convergence
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• v.27 no.2_2
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• pp.371-375
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• 2024

Epoxy resins are widely used in various fields due to their high adhesion, mechanical strength, and solvent resistance. However, as the volume decreases during the hardening process and the cooling process after hardening, stress is generated and when an external force is applied, the brittle material exhibits destruction behavior. To complement this, research has been conducted using inorganic nanofillers such as halloysite nanotube(HNT). HNT has a nanotube structure with the chemical formula of Al₂Si₂O₅(OH)₄·nH₂O and is a natural sediment of aluminosilicate. It has been used as additive to improve the mechanical properties of epoxy composites with exchange of amine group as a terminal functional group. In order to simplify complicated procedures of common wet method, a dry coating machine was designed and used for amine group exchange in previous research. In this study, they were applied as filler in epoxy composites, and mechanical properties such as tensile strength and flexural strength of composites were examined.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.18 no.4
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• pp.357-362
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• 2005

The tandem solar cell composed of a dye-sensitized solar cell (DSC) and a thermoelectric generator (TEG) was designed. In such new cell, the characteristics of DSC and TEG were investigated. DSC uses the wavelength range of 380∼750 nm and has the maximum efficiency of below 10 ％. If the solar light transmitted through DSC can be converted to heat energy, TEG can generate electric energy using this heat energy. By this means, it is possible to utilize most of solar energy in the wavelength range of 350∼3000 nm for electric generation and it can be expected to obtain higher solar energy conversion efficiency exceeding the known limit of maximum efficiency. For this purpose we suggest the tandem solar cell constructed with DSC and TEG. In this structure, DSC has a carbon nanotube film as a counter electrode of DSC in order to collect the solar light and convert it to heat energy. We measured the I-V characteristics of DSC and TEG, assembled to the tandem cell. As a result, it was shown that DSC with carbon nanotube and TEG had the efficiency of 9.1 ％ and 6.2 ％, respectively. From this results, it is expected that the tandem solar cell of the new design has the possibility of enhanced conversion efficiency to exceed above 15 ％.