• Korean Journal of Materials Research
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• v.14 no.5
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• pp.353-357
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• 2004

The influences of the ozone oxidation, reaction temperature and NaOH equivalent ratio on the iron oxide formation were studied with fixed ferrous sulfate concentration(0.5M $FeSO_4$ㆍ$7H_2$O). Geothite($\alpha$-FeOOH) and/or Magnetite ($Fe_3$$O_4$) were synthesized depending on the reaction conditions. The characteristics of the synthesized powders were evaluated by XRD, SEM and quantitative phase analysis. The synthetic conditions to get Goethite were quite different from the results of Kiyama's and the Goethite was conveniently synthesized at low temperature and at low NaOH equivalent ratio.

• Nuclear Engineering and Technology
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• v.52 no.10
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• pp.2299-2305
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• 2020

Zr alloy specimens were coated with Cr-Al alloy to enhance their resistance to oxidation. The coated samples were oxidized at 1200 ℃ in a steam environment for 300 s and showed extremely low oxidation when compared to uncoated Zr alloy specimens. The microstructure and elemental distribution of the oxides formed on the surface of Cr-Al alloys have been investigated by transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS). A very thin protective layer of Cr₂O₃ formed on the outer surface of the Cr-Al alloy, and a thin Al₂O₃ layer was also observed in the Cr-Al alloy matrix, near the surface. Our results suggest that these two oxide layers near the surface confers excellent oxidation resistance to the Cr-Al alloy. Even after exposure to a high temperature of 1200 ℃, inter-diffusion between the Cr-Al alloy and the Zr alloy occurred in very few regions near the interface. Analysis of the inter-diffusion layer by high-resolution transmission electron microscopy (HRTEM) and energy dispersive X-ray spectroscopy (EDS) measurement confirmed its identity as Cr₂Zr.

• Clean Technology
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• v.26 no.4
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• pp.286-292
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• 2020

This study confirmed the effect of the Cu/CeO2-X catalyst on the CO oxidation activity at low temperature through the catalyst's structure and reaction characteristics. The catalyst was prepared by the wet impregnation method. Cu/CeO2_X catalysts were manufactured by loading Cu (active metal) using CeO2 (support) formed at different calcination temperatures (300-600 ℃). Manufactured Cu/CeO2_X catalysts were evaluated for the low-temperature activity of carbon monoxide. The Cu/CeO2_300 catalyst showed an activity of 90% at 125 ℃, but the activity gradually decreased as the calcination temperature of the CeO2-X and Cu/CeO2_600 catalysts showed an activity of 65% at 125 ℃. Raman, XRD, H2-TPR, and XPS analysis confirmed the physicochemical properties of the catalysts. Based on the XPS analysis, the lower the calcination temperature of the CeO2 was, the higher the unstable Ce3+ species (non-stoichiometric species) ratio became. The increased Ce3+ species formed a solid solution bond between Cu and CeO2-X, and it was confirmed by the change of the CeO2 peak in Raman analysis and the reduction peak of the solid solution structure in H2-TPR analysis. According to the result, the formation of the solid solution bond between Cu and Ce has been enhanced by the redox properties of the catalysts and by CO oxidation activity at low temperatures.

• Journal of environmental and Sanitary engineering
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• v.18 no.4
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• pp.45-51
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• 2003

This study was conducted to remove the color in dyeing wastewater by ozone oxidation process, and the results were summarized as follows ; The 18.3％ of BOD and 56.3％ TOC were removed as decreasing with pH 1 in dyeing wastewater, containing the polyester reducing process. It showed that terephthalic acid was precipitated at low pH. The color of dyeing wastewater was removed by the first order reaction, and the reaction rate constants at pH 3, 7, 12 were investigated $0.234{\;}min^{-1},{\;}0.215{\;}min^{-1}{\;}and{\;}0.201{\;}min^{-1}$ respectively. It showed that color was more effectively removed with direct reaction of ozone than radical reaction(non-direct reaction). As increasing of the water temperature, the reaction rate constants were increased slightly. It indicated that activity of ozone was improved at high water temperature.

• Proceedings of the Korean Society for Agricultural Machinery Conference
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• 1996.06c
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• pp.878-885
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• 1996

The brown rice drying is effective for energy saving and cost reduction. However, deterioration after drying is one problem, because the skin damage occurs during the drying. So, the measures to preserve the quality has been investigated. One of major quality deteriorations is the oxidation of fat which is contained in the bran layer. So, milling should be carried out to remove the fat as soon as possible after brown rice drying. And the low temperature storage is also worth to be examined for prevention of oxidation. The effect of skin damage on the increase of fat oxidation was clarified. For the grain of skin damage, the increased of fatty acid vaule was remarkable after 70 days elapsed from occurrence of skin damage even in $15\;^{\circ}C$ condition. Therefore it is impossible to keep grain as brown rice form after brown rice drying. For the clean rice and excessively milled rice, the quality can be preserved even in high temperature of $30\;^{\circ}C$. Therefore the brown rice drying can b applied practically using the clean rice technique.

• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2006.09b
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• pp.1067-1070
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• 2006

Experimental samples were produced with mullite and cordierite powders with SiC. Effects of temperature, atmosphere and additive on the composite properties were investigated by XRD, STA and PSA methods. Results show that samples containing calcinate cordierite and calcinate mullite with SiC baked in air atmosphere have not suitable properties at the temperature range of $1380-1450^{\circ}C$ due to SiC intensive oxidation, while argon atmosphere decrease SiC oxidation. Using $Bi_2O_3$ as the additive, cordierite phase formation and prevention from SiC oxidation at low temperatures were achieved, leading to the improvement of physical and mechanical properties

• Journal of the Korean Society of Safety
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• v.10 no.4
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• pp.75-80
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• 1995

Spontaneous ignition characteristics of rice cracker were observed by preforming experiments at constant ambient temperature. As the results of the experiments, the critical spontaneous ignition temperature were exponentially decreased with the increase of ambient temperature. Type of combustion of rice cracker are smouldering combustion at low ignition temperature and flame combustion at high temperature. The rice cracker containing pam oil showed lower spontaneous ignition temperature than pure rice cracker because of oxidation heat of pam oil.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.31 no.10
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• pp.855-859
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• 2007

Hydrogen as an energy carrier in fuel cell offers perhaps the largest potential benefits of reduced emissions of pollutants and greenhouse gases. The generation of high-purity hydrogen from hydrocarbon fuels is essential for efficient operation of fuel cell. Reduction of carbon monoxide to an acceptable level of 10ppm involves high temperature and low temperature water gas shift (WGS), followed by selective oxidation of residual carbon monoxide. The WGS reactor was designed and tested in this study to produce hydrogen-rich gas with CO to less than 5000 ppm. In the water gas shift operation, gas emerges from the reformer is taken through a high temperature shift (HTS) catalyst to reduce the CO concentration to about $2{\sim}4%$ followed to about 5000 ppm via a low temperature shift (LTS) catalyst.

• Transactions of the Korean Society of Automotive Engineers
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• v.11 no.6
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• pp.59-64
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• 2003

Recently, as people pay attention to the environmental pollution, the emissions of diesel engine have been a serious problem. We carried out the performance evaluation test of Diesel Oxidation Catalysts (DOC) for HSDI diesel engine equipped vehicles. The DOC, basically coated with Pt catalyst, was manufactured with various washcoat materials. It was found that CO conversion efficiency depends on temperature, but THC conversion efficiency is dominated by temperature and space velocity. The THC and CO conversion efficiencies of aged catalysts were increased with additions of $ZrO_2$ and zeolite B in the washcoat. We found that DOC performance changes with coating techniques, even through it has same washcoat materials. The DOC coated by high temperature washcoat coating technology showed good conversion efficiency than low temperature washcoat coated DOC.

• Tribology and Lubricants
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• v.7 no.1
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• pp.46-54
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• 1991

As the additives of engine oil, Mo-DTP and Zn-DTP were studied by experimental works. These additives were added to the engine oil with various ratios, which was an attempt to find out the best ratio at which the wear and friction can be reduced effectively; Mo-DTP is belived to be able to decrease the frictioh of the sliding metal, while Zn-DTP is known as a very stable additive for oxidation at high temperature in addition to the good antiwear property. This study showed that the optimum addition ratio of Mo-DTP and Zn-DTP is 3:2. This oil made it possible to slide steel with minimum wear and low friction over various lovels of load at moderate temperature. But as the oil temperature increased, the wear slid with Mo-DTP oil was increased more. The reason of this result was that Mo-DTP deteriorated the property of oil at high temperature by the higher oxidation and viscosity of Mo-DTP oil than that of Zn-DTP oil.