• Journal of the Microelectronics and Packaging Society
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• v.13 no.4
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• pp.65-70
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• 2006

Carbon nanotubes (CNT) grown by chemical vapor deposition (CVD) and plasma enhanced chemical vapor deposition (PECVD), and followed by annealing at $400{\sim}500^{\circ}C$ were investigated for gas sensing under 1.5ppm $NO_{2}$ concentration at an operating temperature of $200^{\circ}C$. The electrical resistance of CNT sensor decreased with temperature, indicating a semiconductor type. The resistance of CNT sensor decreased with $NO_{2}$ adsorption. It was found that the sensitivity of sensor was affected by humidity and decreased under microwave irradiation for 3 minutes. The CNT sensor grown by PECVD had a higher sensitivity than that of CVD.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.20 no.5
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• pp.389-393
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• 2007

We fabricated field-effect transistor based carbon nanotubes(CNTs) directly grown by thermal chemical vapor deposition(CVD) and analyzed their performance. The Ethylene ($C_2H_4$), hydrogen($H_2$) and Argon(Ar) gases were used for the growth of CNTs at $700\;^{\circ}C$. The growth properties of CNTs on the device were analyzed by SEM and AFM. The electrical transport characteristics of CNT FET were investigated by I-V measurement. Transport through the nanotubes is dominated by holes at room temperature. By varying the gate voltage, we successfully modulated the conductance of FET device by more than 7 orders of magnitude.

• Transactions on Electrical and Electronic Materials
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• v.3 no.1
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• pp.23-29
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• 2002

The electronic properties of Carbon Nanotube(CNT) are currently the focus of considerable interest. In this paper, the electronic properties of finite length effect in CNT for the carbon nano-scale device is presented. To Calculate the electronic properties of CNT, Empirical potential method (the extended Brenner potential for C-Si-H) for carbon and Tight Binding molecular dynamic (TBMD) simulation are used. As a result of study, we have known that the value of the band gap decreases with increasing the length of the tube. The energy band gap of (6,6) armchair CNT have the ranges between 0.3 eV and 2.5 eV. Also, our results are in agreements with the result of the other computational techniques.

• 한국정보디스플레이학회:학술대회논문집
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• 2000.01a
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• pp.49-50
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• 2000

5.2" microtip field emission displays (FEDs) with high voltage applications are fabricated. Nano-structural analysis on microtips is performed for the reliable operation of FEDs. Chemical compositions on the apex of microtips are fully analyzed. A charging mechanism on spacers is simulated and experimentally confirmed with micro-images. A gas-aging mechanism is also studied with integration step of FEDs. The brightness of more than 300 $cd/m^2$ is achieved. In addition, as a new concept, 9" color carbon nanotube FEDs (CNT-FEDs) are introduced using well-aligned carbon nanotubes on glass substrates by paste squeeze and surface treatment techniques. A number of carbon nanotubes, $5-10/{\mu}m2$, are uniformly distributed over a large area. The turn-on fields of 1 $V/{\mu}m$ and field emission currents of 1.5 mA at 3 $V/{\mu}m$ are acquired. Different mechanisms between microtip FEDs and CNT-FEDs are discussed.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2007.06a
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• pp.164-165
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• 2007

The effect of hydrogen and oxygen plasma treatments on the structural properties of carbon nanotubes (CNTs) has been systematically investigated. The plasma treatment resulted in the removal of the amorphous carbon particles. As the plasma treatment time was longer, the CNT diameter was reduced, regardless of gas types. Especially, for the sample treated in hydrogen plasma, the catalyst metal on the tip of CNTs was eliminated.

• Steel and Composite Structures
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• v.25 no.3
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• pp.315-326
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• 2017

In this work, thermoelastic dynamic behavior of functionally graded carbon nanotube reinforced composite (FG-CNTRC) cylinders subjected to mechanical pressure loads, uniform temperature environment or thermal gradient loads is investigated by a mesh-free method. The material properties and thermal stress wave propagation of the nanocomposite cylinders are derived after solving of the transient thermal equation and obtaining of the time history of temperature field of the cylinders. The nanocomposite cylinders are made of a polymer matrix and wavy single-walled carbon nanotubes (SWCNTs). The volume fraction of carbon nanotubes (CNTs) are assumed variable along the radial direction of the axisymmetric cylinder. Also, material properties of the polymer and CNT are assumed temperature-dependent and mechanical properties of the nanocomposite are estimated by a micro mechanical model in volume fraction form. In the mesh-free analysis, moving least squares shape functions are used to approximate temperature and displacement fields in the weak form of motion equation and transient thermal equation, respectively. Also, transformation method is used to impose their essential boundary conditions. Effects of waviness, volume fraction and distribution pattern of CNT, temperature of environment and direction of thermal gradient loads are investigated on the thermoelastic dynamic behavior of FG-CNTRC cylinders.

• Carbon letters
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• v.28
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• pp.55-59
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• 2018

Transition-metal-embedded carbon nanotubes (CNTs) have been accepted as a novel type of sensing material due to the combined advantage of the transition metal, which possesses good catalytic behavior for gas interaction, and CNTs, with large effective surface areas that present good adsorption ability towards gas molecules. In this work, we simulate the adsorption of $O_2$ and $O_3$ onto Rh-doped CNT in an effort to understand the adsorbing behavior of such a surface. Results indicate that the proposed material presents good adsorbing ability and capacities for these two gases, especially $O_3$ molecules, as a result of the relatively large conductivity changes. The frontier molecular orbital theory reveals that the conductivity of Rh-CNT would undergo a decrease after the adsorption of two such oxidizing gases due to the lower electron activity and density of this media. Our calculations are meaningful as they can supply experimentalists with potential sensing material prospects with which to exploit chemical sensors.

• Carbon letters
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• v.11 no.2
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• pp.107-111
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• 2010

We prepared the amine epoxy adducts (AEA)/thin multiwalled carbon nanotubes (TWCNTs) composite particles using nonsolvent based methods including dry mechano-chemical bonding(MCB) process and supercritical fluid (SCF) process. The resulting TWCNTs/AEA composite particles have been used as curing agents for urethane modified bispheol A type epoxy resin. The thermal, thermomechanical properties of the epoxy resins cured with TWCNTs/AEA composite particles were measured by DMA and the dispersion of CNT was characterized by SEM. Because of high degree of CNT dispersion, thermal and mechanical properties of the epoxy resin cured with TWCNTs/AEA composite particles prepared by SCF process are better than those cured with mechano-chemically prepared TWCNTs/AEA composite particles.

• Macromolecular Research
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• v.13 no.3
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• pp.206-211
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• 2005

Multi-walled carbon nanotubes (MWNTs) pre-treated by concentrated mixed acid or oxidized at high temperature were melt mixed with poly(methyl methacrylate) (PMMA) using a twin screw extruder. The morphologies and electrical properties of the MWNT/PMMA composites were investigated. The thermally treated MWNTs (t-MWNTs) were well dispersed, whereas the acid treated MWNTs (a-MWNTs) were highly entangled, forming large-sized clusters. The resulting electrical properties of the composites were analyzed in terms of the carbon nanotube (CNT) dispersion. The experimental percolation threshold was estimated to be $3 wt\%$ of t-MWNTs, but no percolation occurred at similar concentrations in the a-MWNT composites, due to the poor dispersion in the matrix.

• Elastomers and Composites
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• v.45 no.2
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• pp.80-86
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• 2010

Carbon nanotubes (CNTs) exhibit excellent mechanical, electrical, and magnetic properties as well as nanometer scale diameter and high aspect ratio, which make them an ideal reinforcing agent for high strength polymer composites. The functionalized CNTs are believed to be very promising in the fields such as preparation of functional and composite materials. CNT-Polymer composites are expected to have good processability characteristics of the polymer and excellent functional properties of the CNTs. However, since CNTs usually form stabilized bundles due to Van der Waals interactions, are extremely difficult to disperse and align in a polymer matrix. The biggest issues in the preparation of CNT-reinforced composites reside in efficient dispersion of CNTs into a polymer matrix, and the alignment and control of the CNTs in the matrix. There are several methods for the dispersion of nanotubes in the polymer matrix such as solution mixing, bulk mixing, melt mixing, in-situ polymerization and chemical functionalization of the carbon nanotubes, etc. These methods and preparation of high performance CNT-polymer composites are described in this review.