• Korean Journal of Materials Research
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• v.14 no.2
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• pp.90-93
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• 2004

Silicon dioxide thin films were deposited on p-type Si (100) substrates by atomic layer deposition (ALD) method using alternating exposures of $SiH_2$$Cl_2$ and $O_3$ at $300^{\circ}C$. $O_3$ was generated by corona discharge inside the delivery line of $O_2$. The oxide film was deposited mainly from $O_3$ not from $O_2$, because the deposited film was not observed without corona discharge under the same process conditions. The growth rate of the deposited films increased linearly with increasing the exposures of $SiH_2$$Cl_2$ and $O_3$ simultaneously, and was saturated at approximately 0.35 nm/cycle with the reactant exposures over $3.6 ${\times}$ 10^{9}$ /L. At a fixed $SiH_2$$Cl_2$ exposure of $1.2 ${\times}$ 10^{9}$L, growth rate increased with $O_3$ exposure and was saturated at approximately 0.28 nm/cycle with $O_3$ exposures over$ 2.4 ${\times}$ 10^{9}$ L. The composition of the deposited film also varied with the exposure of $O_3$. The [O]/[Si] ratio gradually increased up to 2 with increasing the exposure of $O_3$. Finally, the characteristics of ALD films were compared with those of the silicon oxide films deposited by conventional chemical vapor deposition (CVD) methods. The silicon oxide film prepared by ALD at $300^{\circ}C$ showed better stoichiometry and wet etch rate than those of the silicon oxide films deposited by low-pressure CVD (LPCVD) and atmospheric-pressure CVD (APCVD) at the deposition temperatures ranging from 400 to $800^{\circ}C$.

• Korean Chemical Engineering Research
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• v.48 no.2
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• pp.172-177
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• 2010

This study reports the high-temperature oxidation kinetics, ASR(area specific resistance), and interfacial microstructure of metallic interconnects coated with conductive oxides in oxidation atmosphere at $800^{\circ}C$, The conductive material LSC($La_{0.8}Sr_{0.2}CoO_3$, prepared by Solid State Reaction) was coated on the Crofer22APU. The contact behavior of coating layer/metal substrate was increased by sandblast. The electrical conductivity of the LSC coated Crpfer22APU was measured by a DC two probe four wire method for 4000hr, in air at $800^{\circ}C$. Microstructure and composition of the coated layer interface were investigated by SEM/EDS. These results show that a coated LSC layer prevents the formation and growth of oxide scale such as $Cr_2O_3$ and enhances the long-term stability and electrical performance of metallic interconnects for SOFCs.

• Korean Chemical Engineering Research
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• v.48 no.2
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• pp.185-192
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• 2010

The chemical-looping combustion(CLC) has advantages of no energy loss for separation of $CO_2$ without $NO_x$ formation. This CLC system consists of oxidation and reduction reactors where metal oxides particles are circulating through these two reactors. In the present study, the reaction kinetic equations of iron oxide oxygen carriers supported on bentonite have been determined by the shrinking core model. Based on the reactivity data, design values of solid circulation rate and solids inventory were determined for the rector. Two types of interconnected fluidized bed systems were designed for CLC application, one system consists of a riser and a bubbling fluidized bed, and the other one has a riser and two bubbling fluidized beds. Solid circulation rates were varied to about $30kg/m^2s$ by aeration into a loop-seal. Solid circulation rate increases with increasing aeration velocity and it increases further with an auxiliary gas flow into the loop-seal. As solid circulation rate is increased, solid hold up in the riser increases. A typical gas leakage from the riser to the fluidized bed is found to be less than 1%.

• Journal of the Korean Institute of Gas
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• v.19 no.4
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• pp.22-28
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• 2015

In order to keep the competitiveness of LPG fuel for transportation fuel, the difference in fuel consumption with gasoline and cost for an aftertreatment system should be reduced with continuous development of technology for LPG engine. In the present study, spray-guided type direct injection combustion system, whose configuration is composed of direct injector in the vicinity of spark plug, was employed to realize stable lean combustion. A certain level of nitrogen oxides($NO_x$) emits due to a locally rich mixture regions in the stratified mixture. With the application of EGR system for the reduction of $NO_x$, 15% of $NO_x$ reduction was achieved whereas fuel consumption and hydrocarbon emission increased. By the application of EGR, the combustion speed reduced especially appeared at initial flame development period and peak heat release rates and increasing rates for heat release rate decreased as EGR rate increased due to the dilution effect of intake air.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.25 no.10
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• pp.805-810
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• 2012

Transparent conducting oxides (TCOs) have wide range of application areas in transparent electrode for display devices, Transparent coating for solar energy heat mirrors, and electromagnetic wave shield. $SnO_2$ is intrinsically an n-type semiconductor due to oxygen deficiencies and has a high energy-band gap more than 3.5 eV. It is known as a transparent conducting oxide because of its low resistivity of $10^{-3}{\Omega}{\cdot}cm$ and high transmittance over 90% in visible region. In this study, co-doping effects of Al and Y on the properties of $SnO_2$ were investigated. The addition of Y in $SnO_2$ was tried to create oxygen vacancies that increase the diffusivity of oxygen ions for the densification of $SnO_2$. The addition of Al was expected to increase the electron concentration. Once, we observed solubility limit of $SnO_2$ single-doped with Al and Y. $\{(x/2)Al_2O_3+(x/2)Y_2O_3\}-SnO_2$ was used for the source of Al and Y to prevent the evaporation of $Al_2O_3$ and for the charge compensation. And we observed the valence changes of aluminium oxide because generally reported of valence changes of aluminium oxide in Tin - Aluminium binary system. The electrical properties, solubility limit, densification and microstructure of $SnO_2$ co-doped with Al and Y will be discussed.

• Journal of the Korean Recycled Construction Resources Institute
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• v.7 no.4
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• pp.423-430
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• 2019

In this study, the flexural strength, absorption rate, methylene blue photo catalyst decomposition performance and anti-fouling performance were evaluated according to the photo catalyst mixing rate and block surface wash status by applying photo catalyst to the surface layer of concrete sidewalk block. The results showed that the flexural strength of the block that mixed photo catalyst only in the surface layer of the concrete block was 5.32MPa of the general block (SNW) of 5% photo catalyst, compared to 5.46MPa of the non-mixed concrete block of the reference concrete block. Surface washing block (SW) 5.26MPa, 10% photo catalyst general block (SNW) 5.26MPa, and 5.15MPa surface washing block (SW). It has been shown that the presence of surface washing and the mixing rate of photo catalyst in the concrete block have no effect on the flexural strength. Moreover, the photoreaction performance of concrete sidewalk blocks showed that the methylene blue removal rate of specimens with 5% TiO₂ was 34.2%, the methylene blue removal rate of specimens with 10% TiO₂ was 37.1%, and the removal rate of the methylene blue of specimens with 5% TiO₂ was about 37.9% and 10% mixed specimens with TiO₂ was about 37.6%.

• Journal of Sensor Science and Technology
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• v.5 no.5
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• pp.79-84
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• 1996

A $1\;{\mu}m$ thick n-type GaAs layer with Si doping density of $1{\times}10^{17}/cm^{3}$ and a $500{\AA}$ thick undoped single crystalline AlAs layer were subsequently grown by molecular beam epitaxy on the $n^{+}$ GaAs substrate. The AlAs/GaAs layer was oxidized in $N_{2}$ bubbled $H_{2}O$ vapor($95^{\circ}C$) ambient at $400^{\circ}C$ for 2 and 3 hours. From the result of XPS analysis, small amounts of $As_{2}O_{3}$, AlAs, and elemental As were found in the samples oxidized up to 2 hours. After 3 hours oxidation, however, various oxides related to As were dissolved and As atoms were diffused out toward the oxide surface. The as-grown AlAs/GaAs layer was selectively converted to $Al_{2}O_{3}/GaAs$ at the oxidation temperature $400^{\circ}C$ for 3 hours. The oxidation temperature and time is very critical to stop the oxidation at the AlAs/GaAs interface and to form a defect-free surface layer.

• Journal of Korean Society of Environmental Engineers
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• v.22 no.1
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• pp.169-178
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• 2000

Perovskite oxide catalysts doped on porous alumina beads are prepared in a citric acid solution. To investigate the applicability of the catalysts to the hot gas cleanup, a series of experiments on the reduction characteristics of $NO_x$ by CO as a reducing agent are carried out in a packed bed reactor containing the catalysts. Parameters tested are the operating temperature and $CO/NO_x$ molar ratio. It is found that mixed complex oxides of $La_{0.5}Sr_{0.5}CoO_3$, $SrAl_{12}O_{19}$ and $LaAl_{11}O_{18}$ are uniformly distributed on the alumina beads. The conversion efficiency of $NO_x$ by CO sharply increases with the operating temperature up to $700^{\circ}C$ and then approaches 100% when $CO/NO_x$ molar ratio is greater than 1.0. The conversion efficiency of $NO_x$ is maintained by over 98% during a continuous operation for 23 hours at $800^{\circ}C$ and space velocity of $10700hr^{-1}$.

• Journal of Korean Society of Environmental Engineers
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• v.29 no.5
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• pp.571-576
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• 2007

Manganese-Coated Sand(MCS) prepared with three different methods were applied in the treatment of soluble $Mn^{2+}$ in batch and column experiments. In the bench-scale MCS preparation, the coating efficiency of manganese on the surface of sand increased as the dosage of initial Mn(II) increased. The removed amount of the soluble $Mn^{2+}$ by MCS increased as the solution pH increased, following a typical anionic-type adsorption. The removed amounts of the soluble $Mn^{2+}$ through adsorption was quite similar over the entire pH range, without depending on the contents of Mn on the surface of sand as well as coating methods. When NaClO was used an oxidant, the removed amount of the soluble $Mn^{2+}$ by MCS increased as the concentration of NaClO increased, This trend might be explained by the increased removal efficiency through coating of manganese oxides produced from oxidation of the soluble $Mn^{2+}$ by NaClO on the surface of MCS. From the bench-scale column experiments, the breakthrough of $Mn^{2+}$ occurred after 4,100 bed volume without presence of NaClO while 1.6-times delayed breakthrough of $Mn^{2+}$ was observed in the presence of NaClO. This result also supports that the removal efficiency of the soluble $Mn^{2+}$ could be enhanced by using NaClO.

• Journal of the Korean Institute of Gas
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• v.19 no.2
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• pp.12-19
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• 2015

$CO_2$ is non-flammable, non-toxic gas and not cause of chemical explosion. However, various impurities and some oxides can be included in the captured $CO_2$ inevitably. While the $CO_2$ gas was temporarily stored, the pressure in a storage tank would be reached above 100bar. Therefore, the tank could occur a physical explosion due to the corrosion of vessel or uncertainty. Evaluating the intensity of explosion can be calculated by the TNT equivalent method generally used. To describe the physical explosion, it is assumed that the capacity of a $CO_2$ temporary container is about 100 tons. In this work, physical explosion damage in a $CO_2$ storage tank is estimated by using the Hopkinson's scaling law and the injury effect of human body caused by the explosion is assessed by the probit model.