• Journal of Powder Materials
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• v.8 no.1
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• pp.49-54
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• 2001

The synthesis and characteristics of W-Ni-Fe nanocomposite powder by hydrogen reduction of ball milled W-Ni-Fe oxide mixture were investigated. The ball milled oxide mixture was prepared by high energy attrition milling of W blue powder, NiO and $Fe_2O_3$ for 1 h. The structure of the oxide mixture was characteristic of nano porous agglomerate composite powder consisting of nanoscale particles and pores which act as effective removal path of water vapor during hydrogen reduction process. The reduction experiment showed that the reduction reaction starts from NiO, followed by $Fe_2O_3$ and finally W oxide. It was also found that during the reduction process rapid alloying of Ni-Fe yielded the formation of $\gamma$-Ni-Fe. After reduction at 80$0^{\circ}C$ for 1 h, the nano-composite powder of W-4.57Ni-2.34Fe comprising W and $\gamma$-Ni-Fe phases was produced, of which grain size was35nm for W and 87 nm for $\gamma$-Ni-Fe, respectively. Sinterability of the W heavy alloy nanopowder showing full density and sound microstructure under the condition of 147$0^{\circ}C$/20 min is thought to be suitable for raw material for powder injection molding of tungsten heavy alloy.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2007.11a
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• pp.446-447
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• 2007

The rapid thermal annealing effect of transparent IZTO(indium zinc oxide) and IAZO(indium alminium zinc oxide) films grown on glass substrate for solar cell or flat panel displays(FPDs) was studied. We prepared IZTO using RF magnetron sputtering and IAZO using DC co-sputtering method. Subsequently, using rapid thermal annealing(RTA) system, prepared IZTO and IAZO films were annealed at 300, 400, 500, $600^{\circ}C$ for 90sec. In addition, Electrical and optical characteristics were measured by Hall effect measurement and UV/Vis spectrometer examinations, respectively. To analyze structural properties and surface smoothness of the IZTO and IAZO films, XRD and SEM examinations were performed, respectively. It was shown that IZTO and IAZO films exhibited microcrystalline structure over $400^{\circ}C$ and amorphous structural regardless of RTA temperature, respectively.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2009.10a
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• pp.217-220
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• 2009

This paper presents fabrication method of nano-structured PMMA substrates as well as evaluations of their optical transmittance. For anti-reflective surface, surface coating method had been conventionally used. However, it requires high cost, complicated process and post-processing times. In this study, we suggested the fabrication method of anti-reflective surface by the hot embossing process. Using the nano patterned master fabricated by anodic aluminum oxidation process. Anodic aluminum oxide(AAO) is widely used as templates or a molds for various applications such as carbon nano tube (CNT), nano rod and nano dots. Anodic aluminum oxidation process provides highly ordered regular nano-structures on the large area, while conventional pattering methods such as E-beam and FIB can fabricate arbitrary nano-structures on small area. We fabricated a porous alumina hole array with various inter-pore distance and pore diameter. In order to replicate nano-structures using alumina nano hole array patterns, we have carried out hot-embossing process with PMMA substrates. Finally the nano-structured PMMA substrates were fabricated and their optical transmittances were measured in order to evaluate the charateristivs of anti-reflection. Anti-reflective structure can be applied to various displays and automobile components.

• Proceedings of the Korean Society For Composite Materials Conference
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• 2001.10a
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• pp.137-140
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• 2001

Oragnic/inorganic hybrid materials prepared by sol-gel method have rapidly become a fasci nating research field in materials science. In this study, Polyimide/$\textrm{TiO}_2$ composites were synthesized from nano-sized anatase $\textrm{TiO}_2$ and two types of Polyimide (BTDA-PPD, PMDA-ODA) by Sol-gel method. Nano-sized $\textrm{TiO}_2$ particles were prepared from $\textrm{TiOEt}_4$ solution. The composites were charcaterized by using XRD, TGA, IR, TEM, and Atomic Force Microscope(AFM). $\textrm{TiO}_2$ nano particles were dispersed well in polyimide matrix and the thermal stability of polyimide was improved with $\textrm{TiO}_2$ nano-sized particles.

• Journal of the Korean institute of surface engineering
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• v.41 no.6
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• pp.331-334
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• 2008

The replica of highly ordered nano-sphere array patterns were fabricated using hot embossing method. First, silica nano-sphere array on Si substrate was transferred to PVC film at $130^{\circ}C$ and 7 bar using hot embossing process. Then, silica nano-sphere array on PVC template was removed by soaking the PVC film in buffered oxide etcher. In order to form anti-stiction layer, the PVC template was coated with silicon dioxide layer and self-assembled monolayer. Through UV nanoimprint lithography with the fabricated flexible PVC template, highly ordered nano-sphere array pattern was imprinted on curved substrates with high fidelity.

• Journal of the Korean Chemical Society
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• v.57 no.5
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• pp.547-553
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• 2013

Zirconium oxide ($ZrO_2$) nano porous membranes were fabricated by electrochemical two-step anodization with an electropolished zirconium substrate in inorganic water-based and organic electrolyte systems containing small amounts of fluoride. Using two-step anodization and organic electrolytes, highly regular and ordered nanotubular $ZrO_2$ oxide layers can be compared with aqueous electrolytes. The morphology and size of the nano porous layers were characterized by FE-SEM (field emission scanning electron microscopy), XRD (X-ray diffraction), and EDS (energy dispersive spectroscopy). Luminescence properties were investigated by photoluminescence measurements.

• Bulletin of the Korean Chemical Society
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• v.35 no.9
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• pp.2749-2752
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• 2014

Recent studies have shown that single-stranded DNA adsorbed onto graphene oxide is protected from DNase I cleavage. However, double-stranded DNA bound to graphene oxide and could be digested by DNase I. To elucidate whether single-stranded DNA is protect from DNase I in the presence of graphene oxide, this study conducted DNase I digestion using single-stranded DNA and single-stranded DNA containing the duplex region in the presence of graphene oxide. Addition of DNase I resulted in restoration of the fluorescence emission that had been quenched when DNA was adsorbed to graphene oxide. It indicates that DNase I cleaved the adsorbed single-stranded DNA onto graphene oxide, which was sufficient for the detection of DNase I activity.

• Bulletin of the Korean Chemical Society
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• v.27 no.8
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• pp.1235-1238
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• 2006

• Bulletin of the Korean Chemical Society
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• v.19 no.9
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• pp.1002-1005
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• 1998

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.21 no.5
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• pp.205-209
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• 2011

Zinc oxide has semi-conductivity and super conductivity characteristics. It can be used optically and is applied on many areas such as gas sensor, solar cell and optical waveguide. In this paper, to improve optical characteristics of ZnO, aluminum was added on zinc oxide. Zinc oxide and aluminum zinc oxide was fabricated as nano fiber form. ZnO solution was created by mixing poly vinyl pyrrolidone, ethyl alcohol, and zinc acetate. An Al doped ZnO was created by adding aluminum solution to ZnO sol. By applying these sols on electro spinning method, nano fibers were fabricated. These fibers are heat treated at 300, 500, and $700^{\circ}C$ degrees and were analyzed with X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM) to examine the nano structures. TGA and DSC measurement was also used to measure the change of mass and calorie upon temperature change. The absorbance of ZnO and Al-doped ZnO was carried out by UV-vis measurement.