• Journal of the Korean Electrochemical Society
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• v.25 no.4
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• pp.184-190
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• 2022

Spinel LiMn₂O₄ (LMO) and layered LiNi_0.5Co_0.2Mn_0.3O₂ (NCM) are widely used as positive electrode materials for lithium-ion batteries. LMO and NCM positive electrode materials have a complementary properties. LMO has low cost and high safety and NCM materials show a relatively high specific capacity and better cycle life even at elevated temperature. Therefore, the LMO and NCM active materials are blended and used as a positive electrode in large-size batteries for electric vehicles (xEV). In this study, the cycle performance of a blended electrode prepared by simply mixing LMO and NCM and a bi-layer electrode in which two electrode layers aree sequentially coated are compared. The bi-layer electrode prepared by composing the same ratio of both active materials has similar capacity and cycle performance to the blend electrode. However, the LN electrode coated with LMO first and then NCM is the best in the full cell cycle performance at elevated temperature, and the NL electrode, in which NCM is first coated with LMO has a faster capacity degradation than the blended electrode because LMO is mainly located on the top of the electrode adjacent to electrolyte and graphite negative electrode. Also, the LSTA (linear sweep thermmametry) analysis results show that the LN bi-layer electrode in which the LMO is located inside the electrode has good thermal stability.

• Applied Chemistry for Engineering
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• v.10 no.6
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• pp.832-837
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• 1999

Stability of a cathode material was determined by Tafel plot in 1 M LiOH solution. The stabilized $LiM_xMn_{2-x}O_4$ (x=0.05~0.1) electrode resulted in overpotential of 0.13~0.15 mV at 100 mA. This overpotential was 0.05 mV lower than that of the spinel structured $LiMn_2O_4$ electrode. Conductivity test at various potentials showed that the conductivity of $LiM_xMn_{2-x}O_4$ was higher than that of the spinel structured $LiMn_2O_4$ and the bulk resistance of $LiM_xMn_{2-x}O_4$ due to the dissolution of $Mn^{2+}$ was lowered.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.30 no.9
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• pp.589-595
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• 2017

MOS-FET structured gas sensors were manufactured using MWCNTs for application as NOx gas sensors. As the gas sensors need to be heated to facilitate desorption of the gas molecules, heat dispersion plays a key role in boosting the degree of uniformity of molecular desorption. We report the desorption of gas molecules from the sensor at $150^{\circ}C$ for different sensor electrode gaps (30, 60, and $90{\mu}m$). The COMSOL analysis program was used to verify the process of heat dispersion. For heat analysis, structure of FET gas sensor modeling was proceeded. In addition, a property value of the material was used for two-dimensional modeling. To ascertain the degree of heat dispersion by FEM, the governing equations were presented as partial differential equations. The heat analysis revealed that although a large electrode gap is advantageous for effective gas adsorption, consideration of the heat dispersion gradient indicated that the optimal electrode gap for the sensor is $60{\mu}m$.

• 한국신재생에너지학회:학술대회논문집
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• 2010.06a
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• pp.57.1-57.1
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• 2010

Development of low cost hybrid functional nano-structured materials has great interest to enhance sensitivity of dye-sensitized solar cells and reduction of the production cost. In this talk we will discuss about using different processes to modify functional characteristics of photoelectrode and investigate effects of chemical modification without significant structural variation on to enhance performance of DSSCs. Efficient electron transportation between dye molecules and photoelectrode has been obtained by appropriate chemical modification and efficiency of DSSC has been significantly improved. A comparative analysis on effects of surface functional and electron states of photoelectrode on VOC and JSC has been also carried out to discuss effects of composite materials on physical structure and electronic properties to correlate enhanced performance of these devices.

• Proceedings of the Materials Research Society of Korea Conference
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• 2011.05a
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• pp.40.2-40.2
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• 2011

As the old saying 'nothing is complete unless you put it in final shape', although nanosheets (NSs) are a promising functional building block for various electrochemical applications, their true value cannot be realized until they are well woven into electrical conducting materials. As an effort to determine their ideal shape, in this study, a unique manufacturing route to build a layer-by-layer (LBL) structure of two-dimensionally ordered, free-standing ${\beta}$-nickel hydroxide nanosheets (${\beta}$-NHNSs) that are fully electrically addressed with single-wall carbon nanotube fabrics was demonstrated, and its capabilities were verified through a comparative study on the differences between a simple bulky and LBL-structured electrochemical cathode, representing two extreme cases. The LBL-structured cathode showed a discharging current peak that was 25 times larger than the bulky structured one measured in cyclic voltammetry, which implies that the LBL structure is near an ideal electrode configuration for NS-based electrochemical applications.

• Proceedings of the KIEE Conference
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• 1999.07d
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• pp.1800-1802
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• 1999

Electroluminescence is occurred when phosphor is located in electric field. In this paper, we made powder electroluminescent device (PELD) with structured ITO film/phosphor/Insulator/silver paste. The transparent electrode was ITO film and green(2704-01) and orange(2702-02) and blue-green(2703-01) were used as phosphor. The insulator was $BaTiO_3$ and $Y_2O_3$, back electrode was silver paste. To investigate electrical and optical properties of PELDs, EL spectrum, Brightness, Transferred charge density using Sawyer-Towers circuit was measured.

• Journal of Powder Materials
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• v.10 no.5
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• pp.337-343
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• 2003

Nanostructured Cu-$Al_2O_3$ composite powders were synthesized by thermochemical process. The synthesis procedures are 1) preparation of precursor powder by spray drying of solution made from water-soluble copper and aluminum nitrates, 2) air heat treatments to evaporate volatile components in the precursor powder and synthesis of nano-structured CuO + $Al_2O_3$, and 3) CuO reduction by hydrogen into pure Cu. The suggested procedures stimulated the formation of the gamma-$Al_2O_3$, and different alumina formation behaviors appeared with various heat treating temperatures. The mean particle size of the final Cu/$Al_2O_3$ composite powders produced was 20 nm, and the electrical conductivity and hardness in the hot-extruded bulk were competitive with Cu/$Al_2O_3$ composite by the conventional internal oxidation process.

• Journal of Powder Materials
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• v.25 no.1
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• pp.60-68
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• 2018

The design and fabrication of photoelectrochemical (PEC) electrodes for efficient water splitting is important for developing a sustainable hydrogen evolution system. Among various development approaches for PEC electrodes, the chemical vapor deposition method of atomic layer deposition (ALD), based on self-limiting surface reactions, has attracted attention because it allows precise thickness and composition control as well as conformal coating on various substrates. In this study, recent research progress in improving PEC performance using ALD coating methods is discussed, including 3D and heterojunction-structured PEC electrodes, ALD coatings of noble metals, and the use of sulfide materials as co-catalysts. The enhanced long-term stability of PEC cells by ALD-deposited protecting layers is also reviewed. ALD provides multiple routes to develop improved hydrogen evolution PEC cells.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1999.05a
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• pp.286-290
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• 1999

Electroluminescence is occurred when phosphor is located in electric field. In this paper, we made powder electroluminescent device (PELD) with structured ITO film/Phosphor/Insulator/Silver paste. The transparent electrode was ITO film and green(2704-01), orange(2702-02) and blue-green(2703-01) were used as phosphor. The insulator was BaTiO$_3$ and $Y_2$O$_3$, back electrode was silver paste. To investigate electrical and optical properties of PELDs, EL spectrum, Brightness, Transferred charge density using Sawyer-Tower\`s circuit was measured.

• Bulletin of the Korean Chemical Society
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• v.33 no.4
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• pp.1247-1252
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• 2012

In this paper, a potentiometric sensor based on polyaniline conducting polymer for potentiometric determination of Cr (VI) ions is reported. Polyaniline was synthesized electrochemically (cyclic voltammetry method) onto a micro pencil graphite electrode (0.7 mm diameter) in the presence of HCl and diphenylcarbazide (termed as (PGE/PAni/DPC). Some initial experiments were performed in order to find out the optimized conditions for preparation of the introduced Cr (VI) sensor electrode. The plot of E vs. log [Cr (VI)], showed a linear response in the range from $1.0{\times}10^{-6}$ to $1.0{\times}10^{-1}$ M. High repeatability with the detection limit of $8.0{\times}10^{-7}$ M was obtained.