• Journal of the Korean GEO-environmental Society
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• v.11 no.10
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• pp.49-55
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• 2010

The oil spill occurred frequently due to probably the increased consumption of oil as the energy source and the raw materials of various chemicals. For the treatment of oil contaminated groundwater, DAF(Dissolved Air Flotation) is being used but the removal efficiency is low. Therefore it is necessary to reduce the free phase oil, oil-in water type or water-in oil type emulsified oil, and soluble oil which are the main sources of contaminated groundwater. In this study, treatment of contaminated groundwater was performed using the Fenton oxidation process. The optimum conditions for the removal of THP(Total Petroleum Hydrocarbon) were 3 of pH, 25mM of $H_2O_2$ concentration and 25mM of $Fe^{2+}$ concentration. THP and COD(Chemical Oxygen Demand) concentrations decreased less than 1.5mg/L and 40.0mg/L in 7 minutes using DAF and Fenton oxidation process. However it is necessary to install the settling basin as the sludge concentration increased approximately 5 times.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.24 no.1
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• pp.41-45
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• 2014

We have investigated the passivation property of $SiN_x$ and $SiO_2$ thin films formed using various process conditions for the application of crystalline Si solar cells. An increase in the thickness of $SiN_x$ deposited using plasma enhanced chemical vapor deposition (PECVD) led to the improvement of passivation quality. This could be associated with the passivation of Si dangling bonds by hydrogen atoms which were supplied during PECVD deposition. The $SiO_2$ thin films grown using dry oxidation process exhibited better passivation behavior than those using wet oxidation process, implying the dry oxidation process was more effective in the formation of high quality $SiO_2$ thin films. The relative effective life time gradually decreased with increasing dry oxidation temperature. Such a degradation of passivation behavior could be attributed to the increase in interface trap density caused by thermal damages.

• Journal of Welding and Joining
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• v.25 no.4
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• pp.35-41
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• 2007

In kinetic spraying process, the critical velocity is an important criterion which determines the deposition of a feedstock particle onto the substrate. In other studies, it was experimentally and numerically proven that the critical velocity is determined by the physical and mechanical properties and the state of materials such as initial temperature, size and the extent of oxidation. Compared to un-oxidized feedstock, oxidized feedstock required a greater kinetic energy of in-flight particle to break away oxide film during impact. The oxide film formed on the surface of particle and substrate is of a relatively higher brittleness and hardness than those of general metals. Because of its physical characteristics, the oxide significantly affected the deposition behavior and critical velocity. In this study, in order to investigate the effects of oxidation on the deposition behavior and critical velocity of feedstock, oxygen contents of Al feedstock were artificially controlled, individual particle impact tests were carried out and the velocities of in-flight Al feedstock was measured for a wide range of process gas conditions. As a result, as the oxygen contents of Al feedstock increased, the critical velocity increased.

• Proceedings of the Korean Vacuum Society Conference
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• 2012.08a
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• pp.288-288
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• 2012

The oxidation characteristics of tungsten line pattern during the carbon-based mask layer removal process using oxygen plasmas and the reduction characteristics of the WOx layer formed on the tungsten line surface using hydrogen plasmas have been investigated for sub-50 nm patterning processes. The surface oxidation of tungsten line during the mask layer removal process could be minimized by using a low temperature ($300^{\circ}K$) plasma processing instead of a high temperature plasma processing for the removal of the carbon-based material. Using this technique, the thickness of WOx on the tungsten line could be decreased to 25% of WOx formed by the high temperature processing. The WOx layer could be also completely removed at the low temperature of $300^{\circ}K$ using a hydrogen plasma by supplying bias power to the tungsten substrate to provide an activation energy for the reduction. When this oxidation and reduction technique was applied to actual 40 nm-CD device processing, the complete removal of WOx formed on the sidewall of tungsten line could be observed.

• Corrosion Science and Technology
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• v.5 no.2
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• pp.77-83
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• 2006

The plasma electrolytic oxidation (PEO) process is a relatively new surface treatment technique that produces a chemically stable and environment-friendly electrolytic coating that can be applied to all types of magnesium alloys. In this study, the characteristics of oxide film were examined after coating the extruded AZ31 alloy through the PEO process. Hard ceramic coatings were obtained on the AZ31 alloy by changing the coating time from 10min to 60min. The morphologies of the surface and the cross-section of the PEO coatings were examined by scanning electron microscopy and optical microscopy, and the thickness of the coating was measured. The X-ray diffraction pattern of the coating shows that the coated layer consists mainly of the MgO and $Mg_2SiO_4$ phases after the oxidation reaction. The hardness of the coated AZ31 alloy increased with increasing coating time. In addition, the corrosion rates of the coated and uncoated AZ31 alloys were examined by salt spray tests according to ASTM B 117 and the results show that the corrosion resistance of the coated AZ31 alloy was superior to that of the un-coated AZ31 alloy.

• Composites Research
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• v.13 no.2
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• pp.22-29
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• 2000

Although C/C composites have excellent mechanical properties at high temperature, the disadvantage of oxidation in air restricts their applications. Thus a lot of investments have been studied to improve this drawback. In this study, SiC used as a thermal protective coating material possesses almost the same expansion coefficient compared to that of carbon, so SiC was coated on 4D C/C composites by Pack-Cementation process. For SiC-coated C/C composites, optical microscopy observations were performed to estimate the conversion mechanism involved and air oxidation tests were also performed to evaluate the improvement of oxidation resistance. Afterwards the optimum conditions of coating process were estimated from the results of several analysis and tests.

• Environmental Engineering Research
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• v.13 no.4
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• pp.210-215
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• 2008

The present study investigates the effect of oxidation-reduction potential (ORP) and organic compounds on specific anaerobic ammonium oxidation activity (SAA) using batch experiments. The batch tests were based on the measurement of nitrogen gas production. The relationship between ORP and dissolved oxygen (DO) concentration was found to be ORP (mV) = 160.38 + 68 log [$O_2$], where [$O_2$] is the DO concentration in mg/L. The linear relationship obtained between ORP and SAA ($R^2$ = 0.99) clearly demonstrated that ORP can be employed as an operational parameter in the Anammox process. At ORP value of -110 mV, the SAA was $0.272{\pm}0.03\;g\;N_2-N\;(g\;VSS)^{-1}\;d^{-1}$. The investigation also revealed inhibitory effect of glucose on the SAA while acetate concentration up to 640 mg COD/L (corresponding to 10 mM) had stimulating effect on the SAA. However, acetate concentration beyond 640 mg COD/L had inhibitory effect on the Anammox activity. The results indicated that nitrogen rich wastewaters containing low level organic matter could be better treated by Anammox microorganisms in real-world conditions after some acidification process.

• Carbon letters
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• v.25
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• pp.50-54
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• 2018

Large-size graphene samples are successfully prepared by combining ultrosonic assisted liquid phase exfoliation process with oxidation-deoxidation method. Different from previous works, we used an ultrasound-treated expanded graphite as the raw material and prepared the graphene via a facile oxidation-reduction reaction. Results of X-ray diffraction and Raman spectroscopy confirm the crystal structure of the as-prepared graphene. Scanning electron microscopy images show that this kind of graphene has a large size (with a diameter over $100{\mu}m$), larger than the graphene from graphite powder and flake graphite prepared through single oxidation-deoxidation method. Transmission electron microscopy results also reveal the thin layers of the prepared graphene (number of layers ${\leq}3$). Furthermore, the importance of preprocessing the raw materials is also proven. Therefore, this method is an attractive way for preparing graphene with large size.

• Journal of the Korean Institute of Telematics and Electronics A
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• v.32A no.3
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• pp.68-77
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• 1995

Characteristics of electron cyclotron resonance (ECR) plasma thermal oxide grown at low-temperature have been investigated. The effects of several process parameters such as substrate temperature, microwave power, gas flow rate, and process pressure on the growth rate of the oxide have been also investigated. It was found that the plasma density, reactive ion species, is strongly related to the growth rate of ECR plasma oxied. It was also found that the plasma density increases with microwave power while it decreases with decreasing O2 flow rate. The oxidation time dependence of the oxide thichness showed parabolic characteristics. Considering ECR plasma thermal oxidation at low-temperature, the linear as well as parabolic rate constants calculated from fitting data by using the Deal-Grove model was very large in comparison with conventional thermal oxidation. The ECR plasma oxide grown on (100) crystalline-Si wafer exhibited good electrical characteristics which are comparable to those of thermal oxide: fixed oxide charge(N$_{ff}$)= 7${\times}10^{10}cm^{-2}$, interface state density(N$_{it}$)=4${\times}10^[10}cm^{-2}eV^{-1}$, and breakdown field > 8MV/cm.

• Proceedings of the Korean Vacuum Society Conference
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• 2011.02a
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• pp.325-325
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• 2011

Very initial stage of oxidation process of Si (001) surface at room temperature (300 K) and high temperature (1200 K) was investigated using large scale molecular dynamics simulation. Reactive force field potential [1] was used for the simulation owing to its ability to handle charge variation as well as breaking and forming of bonds associated with the oxidation reaction. The results show that oxygen molecules adsorb dissociatively or otherwise leave the silicon surface. Initial position and orientation of oxygen molecule above the surface play important role in determining final state and time needed to dissociate. At 300 K, continuous transformation of ion $Si^+$ (or suboxide Si2O) to $Si2^+$ (SiO), $Si3^+$ (Si2O3) and finally to $Si4^+$ (SiO2) clearly observed. High temperature silicon surface provide heat energy that enable oxygen atom to penetrate into deeper silicon surface. The heat energy also retards adsorption process. As a result, transformation of ion $Si^+$ is impeded at 1200 K.