• Resources Recycling
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• v.28 no.3
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• pp.59-67
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• 2019

This study was conducted to fabrication pig iron containing copper and to reduce sulfur content pig iron. Roasting test was conducted for 1 ~ 9 hours at each temperature of $500^{\circ}C$, $700^{\circ}C$, and $900^{\circ}C$. In addition, the effect of oxygen partial pressure with 0.5, 0.8, and 1 atm was carried out for 30 minutes at $900^{\circ}C$. It was found that there is no effect to reduce sulfure in pig iron through roasting and oxygen partial pressures. The addition of CaO with 15 wt.% was found to reduce sulfur content up to 0.001 wt.%. The suitable temperature and reactive time for carbothermic reduction were $1600^{\circ}C$ and 30 minutes which shows the highest recovery rate of iron from the copper slag.

• Journal of Electrochemical Science and Technology
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• v.12 no.1
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• pp.137-145
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• 2021

Among the non-precious metal catalysts, iron-nitrogen doped carbon (Fe-N/C) catalysts have been recognized as the most promising candidates for an alternative to Pt-based catalysts for the oxygen reduction reaction (ORR) under alkaline and acidic conditions. In this study, the nano replication method using mesoporous silica, which features tunable primary particle sizes and shape, is employed to prepare the mesoporous Fe-N/C catalysts with different shapes. Platelet SBA-15, irregular KIT-6, and spherical silica particle (SSP) were selected as a template to generate three different kinds of shapes of the mesoporous Fe-N/C catalyst. Physicochemical properties of mesoporous Fe-N/C catalysts are characterized by using small-angle X-ray diffraction, nitrogen adsorption-desorption isotherms, and scanning electron microscopy images. According to the electrochemical evaluation, there is no morphological preference of mesoporous Fe-N/C catalysts toward the ORR activity with half-cell configuration under alkaline electrolyte. By implementing X-ray photoelectron spectroscopy analysis of Fe and N atoms in the mesoporous Fe-N/C catalysts, it is possible to verify that the activity towards ORR highly depends on the portions of "Fe-N" species in the catalysts regardless of the shape of catalysts. It was suggested that active site distribution in the Fe-N/C is one important factor towards ORR activity.

• Korean Chemical Engineering Research
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• v.60 no.1
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• pp.151-158
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• 2022

Iron and nitrogen coordinated carbon catalyst (Fe-N-C) is the most promising non-precious metal catalyst (NPMC) studied to alternate the Pt-group oxygen reduction reaction (ORR) catalyst. In this work, Fe/N/C type catalysts are prepared by four different nitrogen precursors; N, N, N', N'-tetramethylethylenediamine (TMEDA), 1,2-ethylenediamine (EDA), m-dicyanobenzene (DCB), dicyandiamide (DCDA) which can chelate a transition metal; In addition, the catalysts conducted the pyrolysis process at four different temperatures of 700, 800, 900, 1000 ℃ to investigate the ORR activities depend on pyrolysis temperature and to find an appropriate temperature. The characterizations of catalysts were investigated by scanning electron microscope-energy dispersive X-ray spectrometer (SEM-EDS), X-ray diffraction (XRD), and element analysis (EA). The electrocatalytic activity was measured by ORR polarization, also the electron transfer number was calculated from the slope of the K-L plot. The FeNC-EDA-800 which were prepared at pyrolysis temperature of 800 ℃ with EDA showed better ORR activity than the other catalysts.

• Korean Membrane Journal
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• v.9 no.1
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• pp.34-42
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• 2007

A perovskite-type ($La_{0.6}Sr_{0.4}Ti_{0.2}Fe_{0.8}O_{3-{\delta}}$) dense ceramic membrane was prepared by polymerized complex method, using citric acid as a chelating agent and ethylene glycol as an organic stabilizer. Effect of Ti addition on lanthanum-strontium ferrite mixed conductor was investigated by evaluating the thermal expansion coefficient, the oxygen flux, the electrical conductivity, and the phase stability. The thermal expansion coefficient in air was $21.19\;{\times}\;10^{-6}/K$ at 473 to 1,223 K. At the oxygen partial pressure of 0.21 atm ($20%\;O_2$), the electrical conductivity increased with temperature and then decreased after 973 K. The decrement in electrical conductivity at high temperatures was explained by a loss of the lattice oxygen. The oxygen flux increased with temperature and was $0.17\;mL/cm^2{\cdot}min$ at 1,223 K. From the temperature-dependent oxygen flux data, the activation energy of oxygen ion conduction was calculated and was 80.5 kJ/mol at 1,073 to 1,223 K. Also, the Ti-added lanthanum-strontium ferrite mixed conductor was structurally and chemically stable after 450 hours long-term test at 1,173 K.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.41 no.5
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• pp.493-504
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• 2021

The target site, Goejeongcheon flows through downtown of Saha-gu, Busan and it connects to the Nakdong-gang estuary. But non-point pollutants and sewage sludge are partially flowing into the stream and deposited. As a result, dissolved oxygen concentrations of the stream were observed close to the anaerobic condition. Multistage Vortex Aerator was applied for restoring this urban stream. It dissolves oxygen by repeatedly causing collisions between water and oxygen by vortex flow. The changes in water quality and odor were monitored for 2 months while circulating 1 m³/min of water with 22 ppm dissolved oxygen. As a result of the operation, the dissolved oxygen was improved from slightly Bad (4)~Bad (5) to Good (1b)~Normal (3) grade, and the total phosphorus concentration was decreased by 76 % on average. In the case of complex odor, a maximum reduction of 84.5 % was observed on the day the entire river was anaerobic. Through this study, we evaluated the feasibility of applying pure oxygen and Vortex Aerator for the the stream restoration. It is expected that the results of this study can be used for full-scale design.

• Transactions of the Korean hydrogen and new energy society
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• v.34 no.5
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• pp.535-548
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• 2023

The intermittent nature of renewable energy is a challenge to overcome for safety and stable performance in water electrolysis systems linked to renewable energy. Oxygen removal using the catalyst is suitable for maintaining the oxygen concentration in hydrogen below the explosive level (4%) even in intermittent power supply. Metals such as Pd, Pt, and Ni are expected to be effective materials due to their hydrogen affinity. The oxygen removal performance was compared under high hydrogen concentration conditions by loading on γ-Al₂O₃ with high reactivity and large surface area. The characteristics of the catalyst before and after the reaction were analyzed through X-ray diffraction, transmission electron microscope, H₂-temperature programmed reduction, X-ray photoelectron spectroscope, etc. The Pd catalyst that showed the best performance was able to lower 2% oxygen to less than 5 ppm. Changes in catalyst characteristics after the reaction indicate that oxygen vacancies are related to oxygen removal performance and catalyst deactivation.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.13 no.6
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• pp.2479-2483
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• 2012

This paper discusses the development of a personal compact oxygen generator for portable and mobility. The compact oxygen generator is operated with vacuum swing absorption by compact vacuum pump. The components of oxygen generator is composed on the miniaturization and weight reduction, and it is optimized by discharge pump speed, nozzle diameter and 3-way valve interval. In 0.5mm of nozzle diameter, $O_2$ concentration is approximately 37%, and flow rate is $1{\ell}$/min. On the 30cm away from the nozzle, $O_2$ concentration is increased approximately 0.5%.

• Korean Journal of Materials Research
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• v.12 no.8
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• pp.661-668
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• 2002

A study was made to examine the electrical, compositional, structural and morphological properties of Ag thin films deposited by DC magnetron sputtering in $O_2$ atmosphere with deposition temperature from room temperature to 15$0^{\circ}C$ using in-line sputter system. The Ag films deposited at temperature above $100^{\circ}C$ in oxygen atmosphere gave a similar specific resistivity to and even lower oxygen content than those deposited using pure Ar sputter gas The Ag films deposited with pure Ar gas was mainly composed of crystallites with [111] preferred orientation, while, for those deposited in oxygen atmosphere, more than 50% of the volume was composed of crystallites with [100] orientation. The difference in the micro structure did not cause any difference in the specific resistivity of Ag films. The results showed that the transparent conducting oxide films and the Ag films could be processed sequentially in the same deposition chamber with careful control of deposition temperature, which might result in a cost reduction for constructing the large scale in-line deposition system.

• Journal of the Korean Ceramic Society
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• v.47 no.2
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• pp.99-105
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• 2010

The electrical transport properties of mayenite ($Ca_{12}Al_{14}O_{33}$ or $12CaO{\cdot}7Al_2O_3$; mostly abbreviated as $C_{12}A_7$) can be controlled in a wide range by varying the oxygen deficiency: At high temperatures mayenite becomes either an oxygen solid electrolyte, a mixed ionic/electronic conductor or an inorganic electride with metal-like properties upon chemical reduction (removing oxygen). The underlying defect chemistry can be understood on the basis of a relatively simple model-despite the complex cage structure: A point defect model based on the assumption that the framework $[Ca_{12}Al_{14}O_{32}]^{2+}$ acts as a pseudo-donor describes well the high temperature transport properties. It accounts for the observed conductivity plateau at higher oxygen activities and also describes the experimentally observed oxygen activity dependence of the electronic conductivity with -1/4 slope at temperatures between 800 and $1000^{\circ}C$. Doping effects in mayenite are still not well explored, and we review briefly the existing data on doping by different elements. Hydration of mayenite plays a crucial role, as Mayenite is hygroscopic, which may be a major obstacle for technical applications.

• JSTS:Journal of Semiconductor Technology and Science
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• v.3 no.2
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• pp.96-101
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• 2003

Direct evidence on the incorporation of high concentration of oxygen into undoped AlGaN layers for the AlGaN/GaN heterostuctures is provided by scanning photoemission microscopy using synchrotron radiation. In-situ annealing at $1000^{\circ}C$ resulted in a significant increase in the oxygen concentration at the AlGaN surface due to the predominant formation of Al-O bonds. The oxygen incorporation into the AlGaN layers resulting from the high reactivity of Al to oxygen can enhance the tunneling-assisted transport of electrons at the metal/AlGaN interface, leading to the reduction of the Schottky barrier height and the increase of the sheet carrier concentration near the AlGaN/GaN interface.