• The Transactions of The Korean Institute of Electrical Engineers
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• v.57 no.11
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• pp.2015-2022
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• 2008

The effect of content of $Al_2O_3+Y_2O_3$ sintering additives on the densification behavior, mechanical and electrical properties of the pressureless-sintered $SiC-ZrB_2$ electroconductive ceramic composites was investigated. The $SiC-ZrB_2$ electroconductive ceramic composites were pressurless-sintered for 2 hours at 1,700[$^{\circ}C$] temperatures with an addition of $Al_2O_3+Y_2O_3$(6 : 4 mixture of $Al_2O_3$ and $Y_2O_3$) as a sintering aid in the range of $8\;{\sim}\;20$[wt%]. Phase analysis of $SiC-ZrB_2$ composites by XRD revealed mostly of $\alpha$-SiC(6H), $ZrB_2$ and In Situ YAG($Al_5Y_3O_{12}$). The relative density, flexural strength, Young's modulus and vicker's hardness showed the highest value of 89.02[%], 81.58[MPa], 31.44[GPa] and 1.34[GPa] for $SiC-ZrB_2$ composites added with 16[wt%] $Al_2O_3+Y_2O_3$ additives at room temperature respectively. Abnormal grain growth takes place during phase transformation from $\beta$-SiC into $\alpha$-SiC was correlated with In Situ YAG phase by reaction between $Al_2O_3$ and $Y_2O_3$ additive during sintering. The electrical resistivity showed the lowest value of $3.l4{\times}10^{-2}{\Omega}{\cdot}cm$ for $SiC-ZrB_2$ composite added with 16[wt%] $Al_2O_3+Y_2O_3$ additives at 700[$^{\circ}C$]. The electrical resistivity of the $SiC-TiB_2$ and $SiC-ZrB_2$ composite was all negative temperature coefficient resistance (NTCR) in the temperature ranges from room temperature to 700[$^{\circ}C$]. Compositional design and optimization of processing parameters are key factors for controlling and improving the properties of SiC-based electroconductive ceramic composites.

• 한국태양에너지학회:학술대회논문집
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• 2009.04a
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• pp.220-224
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• 2009

The effect of addition of single and binary additives on the performance of dye-sensitized $TiO_2$ solar cells based on 1,2-dimethyl-3-propylimidazolium iodide (DMPII) in ethylene carbonate (EC) and gamma-butyrolactone (GBL) has been evaluated at different cell temperatures in the $30-120^{\circ}C$ range. The electrolyte containing a single additive, 2-(dimethylamino)-pyridine (DMAP) showed best performance, which showed further enhancement for an electrolyte containing binary additives, DMAP and 5-chloro-1-ethyl-2-methylimidazole (CEMI) in equal molar ratio. The performance of the dye sensitized solar cell (DSC) based on electrolyte containing binary additives were found to be better than an acetonitrile based electrolyte. The dependence of different photovoltaic parameters (Voc, Jsc, ff, n) of the DSC upon temperature has been studied over the $30-120^{\circ}C$ range and only a small decrease in conversion efficiency has been observed. Thus the electrolyte containing binary additives (DMAP, CEMI) in EC/GBL solvent and show better performance in the investigated temperature range ($30-120^{\circ}C$).

• Proceedings of the KIEE Conference
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• 1999.07d
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• pp.1723-1725
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• 1999

This paper is the study for piezoelectric properties of PMN-PT-PZ composition for high power piezoelectric device. It needs the properties such as high mechanical quality factor(Qm), high electromechanical coupling coefficient(kp) and high dielectric strain constant$(d_31)$, and the stable electromechanical properties under high vibration level. For acquiring this results, the value of x is changed in 0.1Pb$(Mn_{1/3}Nb_{2/3})O_3$+(0.9-x)$PbZrO_3+xPbTiO_3$ composition to find MPB(morphotropic phase boundary), and the piezoelectric constants is measured by resonance-antiresonance frequency method, based on IRE Standard. Also, it is measured as a function of the amount of additive, $Nb_2O_5$. When the composition is applied to high power device, the electromechanical properties is measured by laser vibrometer to confirm the reliablity under high vibration level. From these results, PMN-PT-PZ composition is shown excellent properties and capacity of application to high power device.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.25 no.3
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• pp.224-228
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• 2012

We have developed new materials that lead to methyl meth acrylate monomer and styrene monomer to using polymerization method. The materials have a powder form and show liquid behavior. We call the "Electronic Bead". An our experiment, a positive-charged particle has $TiO_2$, polymer and CCA(-), while a negative-charged particle consists of carbon black, polymer and CCA(+). The charged particles have electrical characteristic of white -10 uC/g and black 10 uC/g, respectively. Also, these particles have good fluidity by additive of nano-sized silica. Using these materials, we demonstrated prototype displays that have $320{\times}320$ array of pixels and 6-in-diagonal viewable image size, driven by passive-matrix addressing. The reflectivity shows about 30% even though our experiment is at the beginning point. Also, the panel has contrast ratio 6:1. We think there are many chances to improve reflectivity through modifying components of particle resin, mixture ratio of each particle, panel structure and so on.

• Transactions of the Korean hydrogen and new energy society
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• v.27 no.5
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• pp.540-546
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• 2016

Besides high-efficient photovoltaics based on silicon, polymers, dye-sensitization and hybrid perovskite materials, biomimetic solar cells inspired by a leaf in nature has also been actively studied. As one example, a hydrogel based photovoltaics (HGPV) is a low-cost, environmentally friendly device and requires easy fabrication process. In this paper, the effect of hydroquinone additive on the performance of the HGPV is discussed. The photocurrent increases ~14 times upon the addition of hydroquinone into the agarose hydrogel medium. The photocurrent increase is maximum at the optimum dye concentration, while the photovoltage is barely affected by the dye concentration. The effect of the agarose content in the hydrogel and the types of dyes on the photocurrent is also investigated. Finally, it is shown that the photovoltaic performance of HGPV with hydroquinone can be drastically improved when $TiO_2$ film is deposited on the anode electrode.

• Applied Chemistry for Engineering
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• v.21 no.1
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• pp.104-110
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• 2010

Deactivation of SCR catalysts applied in coal, orimulsion, and LNG power plants in Korea were studied for the regeneration of the deactivated catalyst. The catalysts were characterized by XRD, ICP-AES, BET and SEM, and were examined for ammonia SCR. Deactivation of SCR catalyst applied in coal power plant was mainly caused by the blockade of the pore due to the deposition of sulfate and particulate related to the ingredients of the fuel. The surface area of SCR catalyst applied in orimulsion power plant decreased considerably by the accumulation of the compounds of vanadium, sulfur, and magnesium on the surface of the catalyst. The compounds of vanadium and sulfur were related to the ingredients of the fuel, and the compound of magnesium was related to the additive of the fuel. The activity of the deactivated catalyst for ammonia SCR, however, decreased slightly. Despite the long use for more than two-year, deactivation of SCR catalyst applied in LNG power plants hardly occurred.