• Polymer(Korea)
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• v.34 no.4
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• pp.357-362
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• 2010

Poly(ethyleneglycol diacrylate)(PEGDA) or 2-ethylhexyl acrylate(2EHA)-based gel polymer electrolytes(GPEs) which have a solid content in the range of 8～54 wt% were synthesized and their ionic conductivity and electrochemical properties were measured at room temperature. It was observed that the ionic conductivity over $1\times10^{-3}$ S/cm was obtained in a homogeneous PEGDA-based GPE with 21 wt% of solid content. However the electrochemical stability of the GPE was lower than that of a liquid electrolyte. The presence of AIBN initiator which can produce a N2 gas during polymerization process might be the reason of this low oxidation decomposition potential. As an alternative, benzoyl peroxide was used as an initiator and GPE with enhanced electrochemical stability was obtained. Finally, the formation of stable solid electrolyte interphase on a graphite anode was evidenced by cyclic voltammetry measurement.

• Journal of Soil and Groundwater Environment
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• v.18 no.5
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• pp.1-6
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• 2013

This study was performed to develop a method for quantitative analysis obtaining the amount of calcium carbonate minerals formed when Ca salts biomimetically reacted with carbon dioxide. There were two methods compared; 1) volumetric calcimeter method that determining the amount of released carbon dioxide after calcium carbonate minerals were acidified by 4N HCl and 2) Thermogravimetry-Differential Thermal Analysis (TG-DTA) adopting differential decomposition temperature breaking-up the structural link within calcium carbonate minerals. The comparisons were made by batch experiment (i.e., biocalcification process) along with control (i.e., nominal concentration of $CaCO_3$ prepared). For the control, TG-DTA took a minor root mean square deviation (RMSD) of 1.1~5.9 mg, whereas volumetric calcimeter exposed a greater RMSD of 28.3 mg. For the biocalcification, the amount of $CaCO_3$ was more precisely obtained for TG-DTA rather than that of volumetric calcimeter. It was decided that TG-DTA was more successfully used for quantitative analysis to observe the amount of calcium carbonate minerals derived from biocalcification.

• Journal of the Semiconductor & Display Technology
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• v.16 no.2
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• pp.94-97
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• 2017

Amorphous Si has been used for data processing circuits in flat panel displays. However, low mobility of the amorphous Si is a limiting factor for the data transmission speed. Metal oxides such as ZnO have been studied to replace the amorphous Si. ZnO is a wide bandgap (3.3 eV) semiconductor with high mobility and good optical transparency. When ZnO is grown by sputtering with $O_2$ as an oxidizer, there can be many ion species arising from $O_2$ decomposition. $O^+$, $O_2{^+}$, and $O^-$ ions are expected to be the most abundant species, and it is not clear which one contributes to the ZnO growth. We applied alternating substrate voltage (0 V and -70 V) during sputtering growth. We studied changes in transistor characteristics induced by the voltage switching. We also compared ZnO grown by dc and rf sputtering. ZnO film was grown at $450^{\circ}C$ substrate temperature. ZnO thin-film transistor grown with these methods showed $7.5cm^2/Vsec$ mobility, $10^6$ on-off ratio, and -2 V threshold voltage.

• Journal of the Korean Society of Propulsion Engineers
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• v.23 no.4
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• pp.61-69
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• 2019

Accelerated aging test for the double base propellant was carried out at three different temperatures (60, 70, and $75^{\circ}C$) for over a year. To evaluate the aging characteristics of the double base propellant, the stabilizer contents and thermal decomposition kinetics were analyzed by using high performance liquid chromatography (HPLC) and AKTS-Thermokinetics software. As a result, stabilizer contents in the double base propellant gradually decreased according to the aging temperature and aging duration. The consumption rate of 2-NDPA in the accelerated aged propellants showed that it was two times faster at $75^{\circ}C$ in compared with ther rate at $70^{\circ}C$. These experimental values were simulated by the SB kinetic model, and it was shown that the two-step model with constant reaction orders n1=1 and n2=0 best describes the process of the stabilizer depletion for the double base propellant.

• Composites Research
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• v.31 no.6
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• pp.293-298
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• 2018

In this paper, we have studied the physical properties of braided composites for use as aircraft stringers. Process variables such as drum winder speed, braid velocity, and mandrel diameter for $30^{\circ}$, $45^{\circ}$ and $60^{\circ}$ braid preforms were quantified and different epoxy resin types were applied to the braided preform using TGDDM, YD-128. Physical properties such as tensile strength and flexural strength of braided composites were investigated. Thermal properties and decomposition temperature of epoxy resin were investigated by TGA analysis. As a result, the lower the angle of the braid composites, the higher the tensile strength and the Flexural strength. The physical properties of braided composites fabricated using TGDDM epoxy resin were superior to the physical properties of braided composites fabricated using YD-128 epoxy resin. This is because the molecular weight of TGDDM epoxy resin was higher than that of YD-128 epoxy resin.

• Journal of Industrial and Engineering Chemistry
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• v.67
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• pp.148-155
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• 2018

To get a better understanding of the effect of physicochemical properties and microstructure on $SO_2$ absorption behavior of DESs with different molar ratios of EmimCl and EG (from 2:1 to 1:2), densities (${\rho}$), viscosities (${\eta}$), speeds of sound (u), refractive indices ($n_D$), and thermal decomposition temperatures ($T_d$) of EmimCl-EG DESs were measured and used to obtain the other derived properties, such as thermal expansion coefficient (${\alpha}_p$) and activation energy for viscous flow ($E_{\eta}$). Moreover, FT-IR spectra and in situ variable-temperature NMR spectroscopy were employed to study the microstructures of DESs. Based on physicochemical and spectroscopic properties, the influence of the concentrations of EmimCl on the interactions in DESs was explored to be associated with their $SO_2$ absorption behavior. The results show that the interactions between $Emim^+$ and $Cl^-$ of EmimCl is gradually weakening with increasing the concentration of EG in DESs by forming of hydrogen bond interaction of $O-H{\cdots}Cl^-$, resulting in a decrease of ${\rho}$, ${\eta}$, u, $n_D$, and $T_d$ of DESs, and hindering the charge-transfer interaction of $SO_2$ with $Cl^-$ and deceasing $SO_2$ capture capacity. Moreover, the $SO_2$ absorption capacity of DESs is proportional to their ${\rho}$ and $E_{\eta}$, 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.

• Korean Journal of Construction Engineering and Management
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• v.23 no.1
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• pp.73-82
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• 2022

Waste paint, one of the specified wastes in Korea, is currently treated entirely by incineration treatment method, and is hardly recycled compared to other wastes. Incineration treatment method also causes environmental problems such as air pollution. Thus, this study breaks away from the existing incineration treatment method of waste paint and switch to a method of pretreatment operation through evaporation, condensation, and thermal decomposition by temperature control. and then proposes a sustainable waste paint treatment process that can be recycled as an alternative energy heat source. If a new method of disposing of waste paint and technology for recycling are developed and disseminated, it is expected that the effect will be large from an economic and environmental point of view.

• Applied Chemistry for Engineering
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• v.33 no.5
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• pp.466-470
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• 2022

The catalytic thermal oxidizer process has recently attracted considerable attention for the oxidation and decomposition of volatile organic compounds at low temperatures (< 450 ℃) with high efficiency (> 95%). Although many noble metal catalytic materials are well established, they are expensive and hazardous. Herein, highly active and low-cost Cu-Mn bimetallic catalysts were prepared using a simple and facile synthesis method involving the co-precipitation of Cu and Mn precursors. The synthesis of the catalyst was optimized by controlling the composition ratio of Cu and Mn. The optimized catalyst exhibited a large surface area of 230.8 m²/g with a mesoporous structure. To demonstrate the catalytic performance, the Cu-Mn catalyst was tested for the oxidation reaction of ethyl acetate, showing a high conversion efficiency of 100% at a low temperature of 250 ℃.