• 한국정보디스플레이학회:학술대회논문집
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• 2002.08a
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• pp.1028-1031
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• 2002

Ga-based semiconductor nanowires (GaN, GaP) were synthesized by the reaction of Ga metal and GaN/GaP powder with a $NH_3/Ar$ gas using thermal chemical vapor deposition. The field emission and emission stability under oxygen and argon environments were investigated. Field emission energy distributions of electrons from these nanowires revealed that field emission mechanism of the semiconductor nanowires were different from carbon nanotubes.

• Journal of the Korean Ceramic Society
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• v.55 no.5
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• pp.407-418
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• 2018

Increasing demand for portable and wireless electronic devices with high power and energy densities has inspired global research to investigate, in lieu of scarce rare-earth and expensive ruthenium oxide-like materials, abundant, cheap, easily producible, and chemically stable electrode materials. Several potential electrode materials, including carbon-based materials, metal oxides, metal chalcogenides, layered metal double hydroxides, metal nitrides, metal phosphides, and metal chlorides with above requirements, have been effectively and efficiently applied in electrochemical supercapacitor energy storage devices. The synthesis of self-grown, or in-situ, nanostructured electrode materials using chemical processes is well-known, wherein the base material itself produces the required phase of the product with a unique morphology, high surface area, and moderate electrical conductivity. This comprehensive review provides in-depth information on the use of self-grown electrode materials of different morphologies in electrochemical supercapacitor applications. The present limitations and future prospects, from an industrial application perspectives, of self-grown electrode materials in enhancing energy storage capacity are briefly elaborated.

• Composites Research
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• v.16 no.1
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• pp.19-25
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• 2003

In this paper, electrical properties of nanostructured carbon blacks (CB)-filled high density polyethylene (HDPE) composites were investigated as a function of temperature, which were prepared by the conventional melt-mixing method. The composites were irradiated with electron beam in a dosage of 30∼150 kGy to enhance an electronical reproducibility and to reduce a negative temperature coefficient (NTC) phenomenon. And, gel contents (%) of irradiated CB/HDPE composites were estimated by solvent extraction method. From the experimental results. the positive temperature coefficient (PTC) intensity of the composites was strongly depended on the CB content and particle size. And, the increase of gel contents (%) and disappearance of NTC behavior of the composites were identified at a dosage of 60 kGy. It was also found that the electron beam irradiation made an improvement of electrical reproducibility of the composites. This result was probably due to the reduction of the freedom of CB movement at above the melting temperature of the polymer crystalline, resulting in increasing the crosslinking structure of the composites.

• Journal of the Korean institute of surface engineering
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• v.51 no.6
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• pp.365-371
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• 2018

1D core-shell nanostructures have attracted great attention due to their enhanced physical and chemical properties. Specifically, oriented single-crystalline $TiO_2$ nanorods or nanowires on a transparent conductive substrate would be more desirable as the building core backbone. However, a facile approach to produce such structure-based hybrids is highly demanded. In this study, a three-step hydrothermal method was developed to grow NiMn-layered double hydroxide-decorated $TiO_2$/carbon core-shell nanorod arrays on transparent conductive fluorine-doped tin oxide (FTO) substrates. XRD, SEM, TEM, XPS and Raman were used to analyze the obtained samples. The in-situ fabricated hybrid nanostructured materials are expected to be applicable for photoelectrode working in water splitting.

• Korean Journal of Metals and Materials
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• v.48 no.12
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• pp.1130-1135
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• 2010

Cu/carbon nano-particle hybrids were fabricated through the cathodic electrophoretic deposition (EPD) process. CNT and CNF nano-particles were modified to give positive charges by polyethyleneimine (PEI) treatment before depositing them on the substrate. Since a Cu plate was used as an anode in the EPD process, Cu particles were also deposited along with the carbon nano-particles. Experimental observation showed the nano-hybrids constructed a novel formicary-like nano-structure which is strong and highly conductive. Utilizing the hybrids, carbon fiber composites were manufactured, and their electrical conductivity and interlaminar shear strength were measured. In addition, the deposition morphology and failure surface were examined by SEM observations. Results demonstrated that the electrical conductivities in the through-the-thickness direction and the interlaminar shear strength significantly increased by 350~2100% and 14%, respectively.

• Korean Journal of Metals and Materials
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• v.49 no.1
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• pp.79-84
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• 2011

Double-walled carbon nanotubes (DWCNTs) with high purity were produced by the catalytic decomposition of tetrahydrofuran (THF) using a Fe-Mo/MgO catalyst at $800^{\circ}C$. The as-synthesized DWCNTs typically have catalytic impurities and amorphous carbon, which were removed by a two-step purification process consisting of acid treatment and oxidation. In the acid treatment, metallic catalysts were removed in HCl at room temperature for 5 hr with magnetic stirring. Subsequently, the oxidation, using air at $380^{\circ}C$ for 5 hr in the a vertical-type furnace, was used to remove the amorphous carbon particles. The DWCNT suspension was prepared by dispersing the purified DWCNTs in the aqueous sodium dodecyl sulfate solution with horn-type sonication. This was then air-sprayed on ITO glass to fabricate DWCNT field emitters. The field emission properties of DWCNT films related to transmittance were studied. This study provides the possibility of the application of large-area transparent CNT field emission cathodes.

• Korean Journal of Metals and Materials
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• v.48 no.4
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• pp.335-341
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• 2010

High-quality single-walled carbon nanotubes (SWCNTs) were synthesized by catalytic decomposition of $C_2H_2$ using Fe-Mo/MgO catalyst at $800^{\circ}C$. The as-synthesized SWCNTs typically occurred in the form of a bundle with a diameter of 10~20 nm together with amorphous carbon and catalytic impurities, which were removed by a two-step purification process consisting of oxidation and an acid treatment. The oxidation step, using an $O_2$-Ar mixture at $380^{\circ}C$ for 5 hr in a vertical-type furnace and a $HNO_3$ treatment at $100^{\circ}C$ for one hour, was utilized to remove the amorphous carbon particles. Subsequently, metallic catalysts were removed in HCl at room temperature for 5 hr under magnetic stirring. The SWCNT suspension was prepared by dispersing the purified SWCNTs in an aqueous sodium dodecyl benzene sulfonate solution with horn-type sonication. This was then air-sprayed on glass to fabricate CNT field emitters. The samples had a turn-on field value of 4 V/${\mu}m$ and a current density of 0.67 mA/$cm^2$ at 9 V/${\mu}m$. Increasing the HCl treatment time improved the field emission properties.

• Journal of the Microelectronics and Packaging Society
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• v.21 no.4
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• pp.77-82
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• 2014

Stretchable electrodes are focused due to many demands for soft electronics. One of the candidates, carbon black composites have advantages of low cost, easy processing and decreasing resistivity in a certain range during stretching. However, the electrical conductivity of carbon black composites is not enough for electronic devices. Graphene is 2-dimensional nanostructured carbon based material which shows good electrical properties and flexibility. They may help to improve electrical conductivity of the carbon black composites. In this study, graphene was added to a carbon black electrode to enhance electrical properties and investigated. Electrical resistivity of graphene added carbon electrode decreased comparing with that of carbon black electrode because graphene bridged non-contacting carbon black aggregates to strengthen the conductive network. Also graphene reduced an increase in the resistance of the carbon black electrode applied to strain because they connected gap of separated carbon black aggregates and aligned along the stretching direction at the same time. In conclusion, an addition of graphene to carbon black gives two benefits on the electrical properties of carbon black composite as a stretchable electrode.

• Carbon letters
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• v.13 no.2
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• pp.130-132
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• 2012

In this study, cobalt oxide ($Co_3O_4$)/graphene composites were synthesized through a simple chemical method at various calcination temperatures. We controlled the crystallinity, particle size and morphology of cobalt oxide on graphene materials by changing the annealing temperatures (200, 300, $400^{\circ}C$). The nanostructured $Co_3O_4$/graphene hybrid materials were studied to measure the electrochemical performance through cyclic voltammetry. The $Co_3O_4$/graphene sample obtained at $200^{\circ}C$ showed the highest capacitance of 396 $Fg^{-1}$ at 5 $mVs^{-1}$. The morphological structures of composites were also examined by scanning electron microscopy and transmission electron microscopy (TEM). Annealing $Co_3O_4$/graphene samples in air at different temperatures significantly changed the morphology of the composites. The flower-like cobalt oxides with higher crystallinity and larger particle size were generated on graphene according to the increase of calcination temperature. A TEM analysis of the composites at $200^{\circ}C$ revealed that nanoscale $Co_3O_4$ (~7 nm) particles were deposited on the surface of the graphene. The improved electrochemical performance was attributed to a combination effect of graphene and pseudocapacitive effect of $Co_3O_4$.

• Journal of Electrochemical Science and Technology
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• v.9 no.2
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• pp.109-117
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• 2018

A novel carbon paste electrode modified with $Cu-TiO_2$ nanocomposite, 2-(ferrocenylethynyl)fluoren-9-one (2FF) and ionic liquid (IL) (2FF/$Cu-TiO_2$/IL/CPE) was fabricated and employed to study the electrocatalytic oxidation of droxidopa, using cyclic voltammetry (CV), chronoamperometry (CHA) and differential pulse voltammetry (DPV) as diagnostic techniques. It has been found that the oxidation of droxidopa at the surface of modified electrode occurs at a potential of about 295 mV less positive than that of an unmodified CPE. DPV exhibits a linear dynamic range from $5.0{\times}10^{-8}$ to $4.0{\times}10^{-4}M$ and a detection limit of 30.0 nM for droxidopa. Finally this modified electrode was used for simultaneous determination of droxidopa and tryptophan. Also the 2FF/$Cu-TiO_2$/IL/CPE shows excellent ability to determination of droxidopa and tryptophan in real samples.