• Transactions of the Korean Society of Automotive Engineers
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• v.13 no.2
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• pp.178-185
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• 2005

The synergistic effect of ethylene/propane mixture on soot formation is studied experimentally using a concentric co-flow diffusion burner, which provides the stratified fuel mixture. The soot volume fraction, soot particle diameter, number density and PAH concentrations are measured with various fuel supply configurations and compared to the homogeneously mixed case. When propane is supplied through the inner nozzle, an increase of soot formation is observed. However, when propane is supplied through the outer nozzle, a decrease is observed. The reaction path of PAH's formed from the pyrolysis process of propane is likely to be responsible to the observed differences. When propane is supplied through the outer nozzle, PAH's are formed in the relatively near oxidation region and exposed to the oxidization environment; on the other hand, when propane is supplied through the inner nozzle, PAH's are not likely to be oxidized and thus get involved in soot formation process. The synergistic effect in ethylene/propane diffusion flames is found to be affected not only by the com position of the mixture but also by the way of mixing.

• Corrosion Science and Technology
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• v.7 no.3
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• pp.145-151
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• 2008

Material degradation such as high temperature oxidation of metallic material is a severe problem in energy generation systems or manufacturing industries. The metallic materials are oxidized to form oxide films in high temperature environments. The oxide films act as diffusion barriers of oxygen and metal ions and thereafter decrease oxidation rates of metals. The metal oxidation is, however, accelerated by mechanical fracture and spalling of the oxide films caused by thermal stresses by repetition of temperature change, vibration and by the impact of solid particles. It is therefore very important to investigate mechanical properties and adhesion of oxide films in high temperature environments, as well as the properties in a room temperature environment. The oxidation tests were conducted for Ni and Ni-Co alloy under high temperature corrosive environments. The hardness distributions against the indentation depth from the top surface were examined at room temperature. Dynamic indentation tests were performed on Ni oxide films formed on Ni surfaces at room and high temperature to observe fractures or cracks generated around impact craters. As a result, it was found that the mechanical property as hardness of the oxide films were different between Ni and Ni-Co alloy, and between room and high temperatures, and that the adhesion of Ni oxide films was relatively stronger than that of Co oxide films.

• Korean Journal of Materials Research
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• v.23 no.1
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• pp.1-6
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• 2013

A simple thermal oxidation of Cu thin films deposited on planar substrates established a growth of vertically aligned copper oxide (CuO) nanorods. DC sputter-deposited Cu thin films with various thicknesses were oxidized in environments of various oxygen partial pressures to control the kinetics of oxidation. This is a method to synthesize vertically aligned CuO nanorods in a relatively shorter time and at a lower cost than those of other methods such as the popular hydrothermal synthesis. Also, this is a method that does not require a catalyst to synthesize CuO nanorods. The grown CuO nanorods had diameters of ~100 nm and lengths of $1{\sim}25{\mu}m$. We examined the morphology of the synthesized CuO nanorods as a function of the thickness of the Cu films, the gas environment, the oxidation time, the oxidation temperature, the oxygen gas flow rate, etc. The parameters all influence the kinetics of the oxidation, and consequently, the volume expansion in the films. Patterned growth was also carried out to confirm the hypothesis of the CuO nanorod protrusion and growth mechanism. It was found that the compressive stress built up in the Cu film while oxygen molecules incorporated into the film drove CuO nanorods out of the film.

• Journal of Electrochemical Science and Technology
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• v.4 no.1
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• pp.1-18
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• 2013

Gallium is an important element in the production of a variety of compound semiconductors for optoelectronic devices. Gallium has a low melting point and is easily oxidized to give oxides of different compositions that depend on the conditions of solutions containing Ga. Gallium electrode reaction is highly irreversible in acidic media at the dropping mercury electrode. The passive film on a gallium surface is formed during anodic oxidation of gallium metal in alkaline media. Besides, some results in published reports have not been consistent and reproducible. An increase in the demand of intermetallic compounds and semiconductors containing gallium gives rise to studies on electrosynthesis of them and an increase of gallium concentration in the environment with various application of gallium causes the development of electroanalysis tools of Ga. It is required to understand the electrochemistry of Ga and to predict the electrochemical behavior of Ga to meet these needs. Any review papers related to the electrochemistry of gallium have not been published since 1978, when the review on the subject was published by Popova et al. In this study, the redox behavior, anodic oxidation, and electrodeposition of gallium, and trace determination of gallium by stripping voltammetries will be reviewed.

• 한국방재학회:학술대회논문집
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• 2008.02a
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• pp.807-810
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• 2008

Permeable reactive barriers containing Zero-valent iron (ZVI) are used to purify ground-water contaminants. One of the representative contaminant is trichloroethylene (TCE). ZVI can act as a reducing agent of TCE. When ZVI is oxidized to Ferric iron, TCE reduced to Ethene, which is non-harmful matter. As a ZVI becomes ferric iron, the reducing effect decreases and iron becomes unavailable. So, constant reduction of TCE requires the regular supply of reducing agent. So, we use Iron-reducing bacteria(IRB) to extend the TCE degrading ability. We perform three experiment DI water, DI water with medium, and DI water with medium and IRB. By the experiment we try to found the dissolve ability.

• Journal of the Korean institute of surface engineering
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• v.52 no.5
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• pp.246-250
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• 2019

Nano-multilayered $Cr_{25.2}Al_{19.5}Si_{4.7}N_{50.5}$ films were deposited on the steel substrate by cathodic arc plasma deposition. They were corroded at $900^{\circ}C$ in $Ar/1%SO_2$ gas in order to study their corrosion behavior in sulfidizing/oxidizing environments. Despite the presence of sulfur in the gaseous environment, the corrosion was governed by oxidation, leading to formation of protective oxides such as $Cr_2O_3$ and ${\alpha}-Al_2O_3$, where Si was dissolved. Iron diffused outward from the substrate to the film surface, and oxidized to $Fe_2O_3$ and $Fe_3O_4$. The films were corrosion-resistant up to 150 h owing to the formation of thin ($Cr_2O_3$ and/or ${\alpha}-Al_2O_3$)-rich oxide layers. However, they failed when corroded at $900^{\circ}C$ for 300 h, resulting in the formation of layered oxide scales due to not only outward diffusion of Cr, Al, Si, Fe and N, but also inward movement of sulfur and oxygen.

• Journal of Ceramic Processing Research
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• v.19 no.6
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• pp.519-524
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• 2018

Carbon/carbon composites (C/C) have been widely studied in the aerospace field because of their excellent thermal shock resistance and specific strength at high temperature. However, they have the problems that is easily oxidized and deteriorated under atmospheric environment. In order to overcome these shortcomings, the CVD coating of ultra-high-temperature ceramics to C/C has become an important technical issue. In this study, thermodynamic calculations were performed to TaC CVD coating on C/C by FactSage 6.2 program. The Ta-C phase diagrams were constructed with the results of thermodynamic calculations in the Ta-C-H-Cl system. Based on the Ta-C phase diagram, the experimental conditions were designed to confirm the deposition of various phases such as TaC single phase, TaC + C and $TaC+Ta_2C$ by varying the composition of Ta/C ratio. The deposited films were found to be in good agreement with the predicted phases.

• Journal of Korean Society on Water Environment
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• v.22 no.2
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• pp.277-287
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• 2006

Production loads of the contaminants near the Nakdong-river are, BOD : $1,006ton{\cdot}day^{-1}$, TN : $117ton{\cdot}day^{-1}$, and TP : $21ton{\cdot}day^{-1}$. Among the sources of contamination, the biggest contribution to the production load was shared by the human population, which maintains 40.7% of BOD, 44.2% of TN, and 52.5% of TP production. Similarly, among the sources of discharge load, the human population contributed 45.0% of BOD, 34.5% of TN, and 45.8% of TP. Results of flow investigation in 2001 and 2002 indicate that among the side streams, Nam-river showed the greatest average flow. In case of main stream flow, it was increased in the downstream due to the increase of the influents from the side streams. In case of BOD, COD, TOC and SS, high values were detected at Keumho-river where industrial wastewater was discharged as high level concentration. In case of the main stream, Koryoung point where direct influence of Keumho-river and Seongseo industrial complex is evident showed high BOD, COD and TOC. Oxidized nitrogen compounds and total nitrogen showed similar patterns of BOD, COD, and TOC. Especially, nitrate nitrogen was relatively high at all points. However, in case of Chlorophyll-a, relatively high values were observed at mid- and downstream areas such as Koryoung, Namjee, Soosan, Moolkeum and Hakooeun. This could be caused by the slow flow rate and the abundant nutrient salts attributed by the side streams. Relatively better water quality was observed in 2002 when the flow was relatively abundant than that in 2001. Results of investigation during 2001-2002 showed that delivery load increased as the flow reaches downstream. In 2001, delivery loads at the downstream Soosan-bridge were BOD $22,152ton{\cdot}day^{-1}$, COD $45,467ton{\cdot}day^{-1}$, TN $22,062ton{\cdot}day^{-1}$, TP $926ton{\cdot}day^{-1}$. Delivery loads in 2002 were increased due to the increase of the rainfall. They are BOD $25,876ton{\cdot}day^{-1}$, COD $64,200ton{\cdot}day^{-1}$, TN $41,101ton{\cdot}day^{-1}$, and TP $1,362ton{\cdot}day^{-1}$.

• Journal of Soil and Groundwater Environment
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• v.10 no.5
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• pp.45-51
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• 2005

The sorption/desorption characteristics of phenanthrene on the natural manganese oxide (NMD) were investigated in the presence of phenolic compounds. 4-chlorophenol (4-CP) was effectively oxidized by NMD catalyzed reaction and transformed into humic-like macromolecular compound through inter-or cross-coupling reaction between byproducts. As 4-CP was degraded with time, sorbed amount of phenanthrene on NMD was significantly increased, resulting from the formation of oxidative coupling products. These results imply that NMD can be used for simultaneous treatment of phenolic contaminants and polycyclic aromatic hydrocarbons (PAHs) in soils, sediments, or water. Also, sorbed phenanthrene on NMD in the presence of 4-CP showed high degree of desorption resistance, indicating that sequestration process of phenanthrene was ongoing with time.

• Journal of Korean Society on Water Environment
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• v.23 no.3
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• pp.319-323
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• 2007

The Advanced Oxidation Process (AOP) is being increasingly used to oxidize complex organic constituents in treated effluents from domestic wastewater treatment plants. Generally, ${NO_3}^--N$ concentrations ranges between 5 and 8 mg/L for biologically well-treated effluents. However, nitrate ions, ${NO_3}^-$, affects on oxidation as not only a well-known strong absorber of UV light below 250 nm of wavelength but also as an OH radical scavenger. The objective of this study was to evaluate the AOP systems for degradation of 2,4-DCP, and to delineate the effect of nitrate ions on UV oxidation of 2,4-DCP by conducting a bench-scale operation at various reaction times and initial concentrations of $H_2O_2$. The experimental results indicated that 2,4-DCP could be completely oxidized by $UV/H_2O_2$ process with an initial $H_2O_2$ concentration of 20 mg/L at a retention time of 1.0 min or longer. Nitrate ions did not show any adverse effect on 2,4-DCP oxidation at this high $H_2O_2$ concentration, and the practical initial $H_2O_2$ concentration and reaction time for the 80% oxidation turned out to be 5 mg/L and 1.0 min, respectively.