• Environmental Sciences Bulletin of The Korean Environmental Sciences Society
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• v.3 no.2
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• pp.137-142
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• 1999

One of the most important parameters required to model the absorption of CO2 into aqueous alkanolamine solutions is physical solubility. However, since CO2 reacts in amine solutions, its physical solubility cannot be measured directly. As a result, a nonreacting gas which is similar to CO2 has to be used such as N2O. The solubility of nitrous oxide (N2O) in aqueous solutions of 0wt%-50wt% MDEA, 0wt%-30wt% DEA, and 50wt % total amine with DEA/MDEA molar ratios of 0.05, 0.25, 0.5 and 0.67 was measured using a modified Zipperclave reactor over a temperature range of 293-353 K with near atmospheric partial pressures of N2O. the solubility data from this work were K with near atmospheric partial pressures of N2O. The solubility data from this work were found to be in good agreement with previously reported data where available.

• Elastomers and Composites
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• v.39 no.2
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• pp.153-160
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• 2004

Fullerene oxides were synthesized by fullerene ($C_{70}$) and several amine N-oxides such as 3-picoline N-oxide, pyridine N-oxide hydrate, quinoline N-oxide, and isoquinoline N-oxide under ultrasonic condition at $25{\sim}43^{\circ}C$. The reactivity of fullerene ($C_{70}$) with various amine N-oxides undo, ultrasonic irradiation showed the same in all of the proceeding experiments; 3-picoline N-oxide : pyridine N-oxide hydrate : quinoline N-oxide : isoquinoline N-oxide. The MALDI-TOF MS, UV-vis spectrophotometer and HPLC analysis confirmed that the products of fullerene oxidation are [$C_{70}(O)n$] (n=1).

• Proceedings of the Materials Research Society of Korea Conference
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• 2003.11a
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• pp.120-120
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• 2003

The metallic oxide nanomaterials including ZnO, Ga$_2$O$_3$, TiO$_2$, and SnO$_2$ have been synthesized by a number of methods including laser ablation, arc discharge, thermal annealing procedure, catalytic growth processes, and vapor transport. We have been interested in preparing the nanomaterials of Ga$_2$O$_3$, which is a wide band gap semiconductor (E$_{g}$ =4.9 eV) and used as insulating oxide layer for all gallium-based semiconductor. Ga$_2$O$_3$ is stable at high temperature and a transparent oxide, which has potential application in optoelectronic devices. The Ga$_2$O$_3$ nanoparticles and nanobelts were produced using GaN single crystals, which were grown by flux method inside SUS$^{TM}$ cell using a Na flux and exhibit plate-like morphologies with 4 ~ 5 mm in size. In these experiments, the conventional electric furnace was used. GaN single crystals were pulverized in form of powder for the growth of Ga$_2$O$_3$ nanomaterials. The structure, morphology and composition of the products were studied mainly by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), and high-resolution transmission electron microscopy (HRTEM).).

• Korean Journal of Materials Research
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• v.28 no.1
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• pp.32-37
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• 2018

We report on the efficient detection of NO gas by an all-oxide semiconductor p-n heterojunction diode structure comprised of n-type zinc oxide (ZnO) nanorods embedded in p-type copper oxide (CuO) thin film. The CuO thin film/ZnO nanorod heterostructure was fabricated by directly sputtering CuO thin film onto a vertically aligned ZnO nanorod array synthesized via a hydrothemal method. The transport behavior and NO gas sensing properties of the fabricated CuO thin film/ZnO nanorod heterostructure were charcterized and revealed that the oxide semiconductor heterojunction exhibited a definite rectifying diode-like behavior at various temperatures ranging from room temperature to $250^{\circ}C$. The NO gas sensing experiment indicated that the CuO thin film/ZnO nanorod heterostructure had a good sensing performance for the efficient detection of NO gas in the range of 2-14 ppm under the conditions of an applied bias of 2 V and a comparatively low operating temperature of $150^{\circ}C$. The NO gas sensing process in the CuO/ZnO p-n heterostructure is discussed in terms of the electronic band structure.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.08a
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• pp.138.2-138.2
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• 2013

Copper oxide is a multi-functional material being used in various research areas including catalysis, electrochemical materials, oxidizing agents etc. Among these areas, we have synthesized and utilized graphene based copper oxide nanocomposites (CuOx/Graphene) for the catalytic applications (C-N cross coupling reaction). Briefly, Cu precursors were anchored on the graphite oxide(GO) sheets being exfoliated and oxidized from graphite powder. Two different crystalline structures of Cu2O and CuO on graphene and GO were prepared by annealing them in Ar and O2 environments, respectively. The morphological and electronic structures were systemically investigated using FT-IR, XRD, XPS, XAFS, and TEM. Here, we demonstrate that the catalytic performance was found to depend on oxidative states and morphological structures of CuOx graphene nanocomposites. The relationship between the structure of copper oxides and catalytic efficiency toward C-N cross coupling reaction will be discussed.

• Journal of Sensor Science and Technology
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• v.31 no.5
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• pp.337-342
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• 2022

Hydrogen (H₂) gas is widely preferred for use as a renewable energy source owing to its characteristics such as environmental friendliness and a high energy density. However, H₂ can easily reverse or explode due to minor external factors. Therefore, H₂ gas monitoring is crucial, especially when the H₂ concentration is close to the lower explosive limit. In this study, metal oxide materials and their p-n heterojunctions were synthesized by a hydrothermal-assisted dip-coating method. The synthesized thin films were used as sensing materials for H₂ gas. When the H₂ concentration was varied, all metal oxide materials exhibited different gas sensitivities. The performance of the metal oxide gas sensor was analyzed to identify parameters that could improve the performance, such as the choice of the metal oxide material, effect of the p-n heterojunctions, and operating temperature conditions of the gas sensor. The experimental results demonstrated that a CuO/ZnO gas sensor with a p-n heterojunction exhibited a high sensitivity and fast response time (134.9% and 8 s, respectively) to 5% H₂ gas at an operating temperature of 300℃.

• Korean Journal of Materials Research
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• v.3 no.1
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• pp.7-11
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• 1993

Abstract Oxidation kinetics of silicon oxide films formed by rapid thermal oxidizing Si substrate in $N_2$O ambient studied. The data on $N_2$0 oxidation shows that the interfacial nitrogen-rich layers results in oxide growth in the parabolic regime by impeding oxidant diffusion to the Si$O_2$-Si interface even for ultrathin oxides. The activation energy of parablic rate constant, B, is about 1.5 eV, and the energy increses with oxide thickness.

• Korean Journal of Materials Research
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• v.23 no.9
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• pp.477-482
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• 2013

We investigated the detection properties of nitrogen monoxide (NO) gas using transparent p-type $CuAlO_2$ thin film gas sensors. The $CuAlO_2$ film was fabricated on an indium tin oxide (ITO)/glass substrate by pulsed laser deposition (PLD), and then the transparent p-type $CuAlO_2$ active layer was formed by annealing. Structural and optical characterizations revealed that the transparent p-type $CuAlO_2$ layer with a thickness of around 200 nm had a non-crystalline structure, showing a quite flat surface and a high transparency above 65 % in the range of visible light. From the NO gas sensing measurements, it was found that the transparent p-type $CuAlO_2$ thin film gas sensors exhibited the maximum sensitivity to NO gas in dry air at an operating temperature of $180^{\circ}C$. We also found that these $CuAlO_2$ thin film gas sensors showed reversible and reliable electrical resistance-response to NO gas in the operating temperature range. These results indicate that the transparent p-type semiconductor $CuAlO_2$ thin films are very promising for application as sensing materials for gas sensors, in particular, various types of transparent p-n junction gas sensors. Also, these transparent p-type semiconductor $CuAlO_2$ thin films could be combined with an n-type oxide semiconductor to fabricate p-n heterojunction oxide semiconductor gas sensors.

• Environmental Engineering Research
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• v.24 no.1
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• pp.107-116
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• 2019

Nitrogen removal, nitrous oxide ($N_2O$) emission and microbial community in sequencing batch and continuous-flow intermittent aeration processes were investigated. Two sequencing batch reactors (SBRs) and two continuous-flow multiple anoxic and aerobic reactors (CMRs) were operated under high dissolved oxygen (DO) (SBR-H and CMR-H) and low DO (SBR-L and CMR-L) concentrations, respectively. Nitrogen removal was enhanced under CMR and low DO conditions (CMR-L). The highest total inorganic nitrogen removal efficiency of 91.5% was achieved. Higher nitrifying and denitrifying activities in SBRs were observed. CMRs possessed higher $N_2O$ emission factors during nitrification in the presence of organics, with the highest $N_2O$ emission factor of 60.7% in CMR-L. SBR and low DO conditions promoted $N_2O$ emission during denitrification. CMR systems had higher microbial diversity. Candidatus Accumulibacter, Nitrosomonadaceae and putative denitrifiers ($N_2O$ reducers and producers) were responsible for $N_2O$ emission.

• Proceedings of the Korean Vacuum Society Conference
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• 2014.02a
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• pp.346.2-346.2
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• 2014

To use the GaN based light-emitting diodes (LEDs) as solid state lighting sources, the improvement of light extraction and internal quantum efficiency is essential factors for high brightness LEDs. In this study, we suggested the new materials system of a zinc tin oxide (ZTO) layer formed on blue LED epi-structures to improve the light extraction. ZTO is a representative n-type oxide material consisted of ZnO and SnO system. Moreover, ZTO is one of the promising oxide semiconductor material. Even though ZTO has higher chemical stability than IGZO owing to its SnO2 content this has high mobility and high reliability. After formation of ZTO layer on p-GaN layer by using the spin coating method, structural and optical properties are investigated. The x-ray diffraction (XRD) measurement results show the successful formation of ZTO. The photoluminescence (PL) and absorption spectrum shows that it has 3.6-4.1eV band gap. Finally, the light extraction properties of ZTO/LED chip using electroluminescence (EL) measurement were investigated. The experimental and theoretical analyses were simultaneously conducted.