• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2000년도 춘계학술대회 논문집
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• pp.820-823
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• 2000

The characteristics of wire deflection, surface roughness and roundness were observed on changing discharge time for electrical discharge machining(EDM) of tungsten carbide in various conditions of thickness. The wire deflection was decreased as increasing discharge time and wire tension, the gap of deflection was decreased after thickness 60mm and discharge time of 6$\mu\textrm{s}$ due to the changing from fundamental mode to vibration mode. The deflection is the smallest at the water specific resistivity of 7.5 kΩ ㆍcm. The deflection is found to be decreased as increasing dwell time, and the result is due to the vibration of the pressure and the amount of the dielectric. The component of copper(Cu) and zinc(Zn), which is the main material of wire electrode, was observed for rough wire-cutting EDM of STD-11. This phenomena is found to be decreased as the number of EDM is increased. But it will be improved by changing the material and the shape of wire. The roundness of middle is found to be worse than that of upper and it is increased as the thickness of material is increased.

• Carbon letters
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• 제9권4호
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• pp.303-307
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• 2008

The studies on integrated operation of fuel cell with fuel processor are very essential prior to its commercialization. In this study, Polymer Electrolyte Membrane Fuel Cell (PEMFC) was operated with a fuel processor, which is mainly composed of two parts, methanol steam reforming reaction and preferential oxidation (PROX). In fuel processor, ICI 33-5 (CuO 50%, ZnO 33%, $Al_2O_3$ 8%, BET surface area: $66\;m^2g^{-1}$) catalyst and CuO-$CeO_2$ catalyst were used for methanol steam reforming, preferential oxidation (PROX) respectively. PEMFC was operated by hydrogen fuel generated from fuel processor. The resulting gas from PROX reactor is used to operate PEMFC equipped with our prepared anode and cathode catalyst. PtRu/C catalyst gives more tolerance to CO.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2005년도 추계학술대회 논문집 전기물성,응용부문
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• pp.36-38
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• 2005

This study is about how to lower the driving voltage that enables to move the micro droplet by the EWOD (Electro Wetting On Dielectric) mechanism. EWOD is well known that it is used ${\mu}-TAS$ digital micro fluidics system. As the device which is fabricated with dielectric layer between electrode and micro droplet is applied voltage, the hydrophobic surface is changed into the hydrophilic surface by electrical property. Therefore, EWOD induces the movement of micro droplet with reducing contact angle of micro droplet. The driving voltage was depended on the dielectric constant of dielectric layer, thus it can be reduced by increase of dielectric constant. Typically, very high voltage ($100V{\sim}$) is used to move the micro droplet. In previous study, we used $Ta_{2}O_{5}$ as the dielectric layer and driving voltage was 23V that reduced 24 percent compared with $SiO_2$. In this study, we used $BZN(Bi_{2}O_{3}ZnO-Nb_{2}O_{5})$ layer which had high dielectric constant. It was operated the just 12V. And micro droplet was moved within Is on 15V. It was reduced the voltage until 35 percents compare with $Ta_{2}O_{5}$ and 50 percents compare with $SiO_2$. The movement of micro droplet within 1s was achieved with BZN (ferroelectrics)just on 15V.

• 한국공작기계학회:학술대회논문집
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• 한국공작기계학회 2000년도 춘계학술대회논문집 - 한국공작기계학회
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• pp.537-542
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• 2000

Wire deflection, surface roughness and roundness were observed on changing discharge time for electrical discharge machining(EDM) of STD-11 in various conditions of thickness. The wire deflection was decreased as increasing discharge time and wire tension. The deflection is the smallest at the speed of wire of 10.6m/min and the water specific resistivity of 5k$\Omega$.cm. The deflection is found to be decreased as increasing dwell time. But if the water pressure is high, it is found not to be changed after the vibration of 4sec. The component of copper(Cu) and zinc(Zn), which is the main material of wire electrode, is observed for rough wire-cutting EDM of STD-11. This phenomena is found to be similar in spite of the change of EDM energy level. But it will be improved by changing the material and the shape of wire. The roundness of middle is found to be worse than that of upper and it is increased as the thickness of material is increased.

• Bulletin of the Korean Chemical Society
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• 제35권1호
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• pp.182-188
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• 2014

Three new transition metal complexes based on Ozagrel $[Cu(Ozagrel)]_n$ (1), $[Zn(Ozagrel)(Cl)]_n$ (2), ${[Mn_2-(Ozagrel)(1,4-ndc)_2]{\cdot}(H_2O)}_n$ (3), (Ozagrel = 3-(4-((1H-imidazol-1-yl)methyl)phenyl)acrylic acid; 1,4-ndc = 1,4-Naphthalenedicarboxylic acid) have been hydrothermally synthesized and characterized by elemental analyse, IR, TG, PXRD, electrochemical analysis and single crystal X-ray diffraction. X-ray structure analysis reveals that 1 and 3 are 3D coordination polymers, while complex 2 is a two-dimensional network polymer, the 2D layers are further packed into 3D supramolecular architectures that are connected through hydrogen bonds. The electrochemistry of 1-3 was studied by cyclic voltammetry in methanol and water using a glassy carbon working electrode. Also, thermal decomposition process and powder X-ray diffraction of complexes were investigated.

• Bulletin of the Korean Chemical Society
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• 제28권4호
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• pp.553-556
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• 2007

We previously reported a 27.12 MHz inductively coupled plasma source at atmospheric pressure for atomic emission spectrometry based on polymer microchip plasma technology. For the PDMS polymer microchip plasma, molecular emission was observed, but no metallic detection was done. In this experiment, a lab-made electrothermal vaporizer (ETV) with tantalum coil was connected to the microchip plasma for aqueous sample introduction to detect metal ions. The electrode geometry of this microchip plasma was redesigned for better stability and easy monitoring of emission. The plasma was operated at an rf power of 30-70 W using argon gas at 300 mL/min. Gas kinetic temperatures between 800-3200 K were obtained by measuring OH emission band. Limits of detection of about 20 ng/mL, 96.1 ng/mL, and 1.01 μ g/mL were obtained for alkali metals, Zn, and Pb, respectively, when 10 μ L samples in 0.1% nitric acid were injected into the ETV.

• Bulletin of the Korean Chemical Society
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• 제32권3호
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• pp.847-851
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• 2011

This study examined In-Zn-Sn-O (IZTO) films deposited on glass substrates by pulsed DC magnetron sputtering with various substrate temperatures. The structural, electrical, optical properties were analyzed. Xray diffraction showed that the IZTO films prepared at temperatures > $150^{\circ}C$ were crystalline which adversely affected the electrical properties. Amorphous IZTO films prepared at $100^{\circ}C$ showed the best properties, such as a low resistivity, high transmittance, figure of merit, and high work function of $4.07{\times}10^{-4}\;{\Omega}$, 85%, $10.57{\times}10^{-3}\;{\Omega}^{-1}$, and 5.37 eV, respectively. This suggests that amorphous IZTO films deposited at relatively low substrate temperatures ($100^{\circ}C$) are suitable for electrode applications, such as OLEDs as a substitute for conventional crystallized ITO films.

• Bulletin of the Korean Chemical Society
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• 제33권4호
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• pp.1204-1208
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• 2012

A new photoelectrode composed of $Sb_6O_{13}$ nanoparticles with the size of 20-30 nm has been prepared via thermolysis of a colloidal antimony pentoxide tetrahydrate ($Sb_2O_5{\cdot}4H_2O$) suspension. The $Sb_6O_{13}$ electrode showed good semiconducting properties applicable to dye-sensitized solar cells (DSSCs); the energy band gap was estimated to be $3.05{\pm}0.5$ eV and the position of conduction band edge was close to those of $TiO_2$ and ZnO. The DSSC assembled with the $Sb_6O_{13}$ photoelectrode and a conventional ruthenium-dye (N719) exhibited the overall photo-current conversion efficiency of 0.74% ($V_{oc}$ = 0.76 V, $J_{sc}=1.99\;mAcm{-2}$, fill factor = 0.49) under AM 1.5, $100\;mWcm^{-2}$ illumination.

• 한국분말재료학회지
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• 제27권4호
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• pp.305-310
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• 2020

In this study, partially dry transfer is investigated to solve the problem of fully dry transfer. Partially dry transfer is a method in which multiple layers of graphene are dry-transferred over a wet-transferred graphene layer. At a wavelength of 550 nm, the transmittance of the partially dry-transferred graphene is seen to be about 3% higher for each layer than that of the fully dry-transferred graphene. Furthermore, the sheet resistance of the partially dry-transferred graphene is relatively lower than that of the fully dry-transferred graphene, with the minimum sheet resistance being 179 Ω/sq. In addition, the fully dry-transferred graphene is easily damaged during the solution process, so that the performance of the organic photovoltaics (OPV) does not occur. In contrast, the best efficiency achievable for OPV using the partially dry-transferred graphene is 2.37% for 4 layers.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2016년도 제50회 동계 정기학술대회 초록집
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• pp.289.2-289.2
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• 2016

In-Ga-Zn-O(IGZO) receive great attention as a channel material for thin film transistors(TFTs) as next-generation display panel backplanes due to its superior electrical and physical properties such as a high mobility, low off-current, high sub-threshold slope, flexibility, and optical transparency. For the purpose of fabricating high performance IGZO TFTs, a thermal recovery process above a temperature of $300^{\circ}C$ is required for recovery or rearrangement of the ionic bonding structure. However diffused metal atoms from source/drain(S/D) electrodes increase the channel conductivity through the oxidation of diffused atoms and reduction of $In_2O_3$ during the thermal recovery process. Threshold voltage ($V_{TH}$) shift, one of the electrical instability, restricts actual applications of IGZO TFTs. Therefore, additional investigation of the electrical stability of IGZO TFTs is required. In this paper, we demonstrate the effect of Ti diffusion and modulation of interface traps by carrying out an annealing process on IGZO. In order to investigate the effect of diffused Ti atoms from the S/D electrode, we use secondary ion mass spectroscopy (SIMS), X-ray photoelectron spectroscopy, HSC chemistry simulation, and electrical measurements. By thermal annealing process, we demonstrate VTH shift as a function of the channel length and the gate stress. Furthermore, we enhance the electrical stability of the IGZO TFTs through a second thermal annealing process performed at temperature $50^{\circ}C$ lower than the first annealing step to diffuse Ti atoms in the lateral direction with minimal effects on the channel conductivity.