• Carbon letters
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• v.1 no.1
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• pp.17-21
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• 2000

Catalytic reduction and oxidation of NO over polyacrylonitrile based activated carbon fibers (PAN-ACF) under various conditions were carried out to develop removal process of NO from the flue gas. The effect of temperature, oxygen concentration and the moisture content for the reduction of NO with ammonia as a reducing agent was investigated. The reduction of NO increased with the oxygen concentration, but decreased with the increased temperature. The moisture content in the flue gas affects the reduction of NO as the inhibition of the adsorption of the other components and the reaction on the surface of ACE For the oxidation of NO to $NO_2$ over PAN-ACF without using a reducing gas, it showed the temperature and the oxygen concentration of the flue gas are the important factors for the NO conversion in which the conversion increased with oxygen concentration and decreased with the temperature increase and might be the alternative option for the selective catalytic reduction process.

• 한국신재생에너지학회:학술대회논문집
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• 2009.11a
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• pp.217-217
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• 2009

In this work, the oxidation-induced characteristics of five nuclear graphites (NBG-17, NBG-18, NBG-25, IG-110, and IG-430) were studied. The oxidation characteristics of nuclear graphites were measured at the three temperature areas (300, 600, and $900^{\circ}C$). As experimental results, the pore size of oxidized graphite was increased with increasing of oxidation time. It was also found that the oxdation rate was propotional to the oxidation temperature and time. This was probably due to the oxidation was occurred on the surface and inner bulk phase of nuclear graphites at the same time by the socalled chemical regime.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2011.05a
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• pp.75-76
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• 2011

Hot-rolled steel plates of SPHC and SS400 were oxidized at 600, 750 and $900^{\circ}C$ for 2hr in air. With an increase in oxidation temperature, their oxidation rates increased, being accompanied with formation of pores and cracks in the thickened oxide scales that were non-adherent. The SPHC steels that were manufactured by either the arc furnace or the blast furnace displayed similar oxidation rates, indicating that their oxidation rates were insensitive to the manufacturing processes. The medium-carbon SS400 steel displayed a little faster oxidation rates than the low-carbon SS400 steel, indicating that the carbon content did not significantly influence the oxidation rates.

• Korean Journal of Materials Research
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• v.6 no.1
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• pp.57-66
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• 1996

MoSi2 heating elements were fabricated by sintering of MoSi2 powders which were synthesized through SHS(Self-propagating high-temperature synthesis). Their high-temperature oxidation behavior in air through SHS(Self-propagating high-temperature synthesis). Their high-temperature oxidation behavior on air at 1000-1600$^{\circ}C$ was investigated through a high-temperature X-ray diffractomer and isothermal heating in a muffle furnace. The thermal expansion of MoSi2 and SiO2 was studied by measuring their lattice parameters on heating. The linear expansion coeffcient of MoSi2 along c-axis was about 1.5 times larger than that along a-axis showing a strong thermal anisotropy. Few $\mu\textrm{m}$-thick Mo5Si3 layer was found beneath SiO2 layer suggesting that The major reaction products would be SiO2 and Mo5Si3. The Si-rich bentonite resulted in the faster growth of MoSi2 grains probably by enhancing the mass transport when they are melted during high-temperature oxidation.

• Transactions of the Korean Society of Pressure Vessels and Piping
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• v.7 no.2
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• pp.34-41
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• 2011

Wrought nickel-base superalloys are being considered as the structural materials in very-high temperature gas-cooled reactors. To understand the effects of impurities, especially oxygen, in helium coolant on the mechanical properties of Alloy 617, creep tests were performed in high temperature flowing He environments with varying $O_2$ contents at 800, 900, and $1000^{\circ}C$. Also, creep life in static He was measured to simulate the pseudo-inert environment. Creep life was the longest in static He, while the shortest in flowing helium. In static He, impurities like $O_2$ and moisture were quickly consumed by oxidation in the early stage of creep test, which prevented further oxidation during creep test. Without oxidation, microstructural change detrimental to creep such as decarburization and internal oxidation were prevented, which resulted in longer creep life. On the other hand, in flowing He environment, surface oxides were not stable enough to act as diffusion barriers for oxidation. Therefore, extensive decarburization and internal oxidation under tensile load contributed to premature failure resulting in short creep life. Limited test in flowing He+200ppm $O_2$ resulted in even shorter creep life. The oxidation samples showed extensive spallation which resulted in severe decarburization and internal oxidation in those environments. Further test and analysis are underway to clarify the relationship between oxidation and creep resistance.

• Journal of Powder Materials
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• v.20 no.6
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• pp.432-438
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• 2013

In this study, analysis on the oxidation behavior was conducted by a series of high-temperature oxidation tests at both $800^{\circ}C$, $900^{\circ}C$ and 1000 in the air with sintered STS 316L. The weight gain of each oxidized specimen was measured, the oxidized surface morphologies and composition of oxidation layer were analyzed with Scanning Electron Microscope-Energy Dispersive x-ray Spectroscopy (SEM-EDS), finally, the phase change and composition of the oxidized specimen were shown by X-Ray Diffraction (XRD). As a result, the weight gain increased sharply at $1000^{\circ}C$ when oxidation test was conducted for 210 hours. Also, a plentiful of pores were observed in the surface oxidation layers at $900^{\circ}C$ for 210 hours. In addition, the following conclusions on oxidation behavior of sintered STS 316L can be obtained: $Cr_2O_3$ can be formed on pores by influxing oxygen through open-pores, $(Fe_{0.6}Cr_{0.4})_2O_3$ can be generated on the inner oxidation layer, and $Fe_2O_3$ was on the outer oxidation layer. Also, $NiFe_2O_4$ could be precipitated if the oxidation time was kept longer.

• Journal of the Korean Applied Science and Technology
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• v.33 no.1
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• pp.100-109
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• 2016

In this study, the NO oxidation using dry oxidant produced by catalytic $H_2O_2$ conversion was conducted. It was shown that Mn-based $Fe_2O_3$ support catalyst has the best performance in the catalytic $H_2O_2$ conversion and its combined-NO oxidation. The reaction characteristics of NO oxidation was investigated by the various operation conditions such as $H_2O_2$ amount, oxidation temperature and space velocity. As a results, the oxidation efficiency of NO greatly depends on the oxidation reaction temperature, $H_2O_2$ amount and space velocity. The performance of NO oxidation was increased with increasing the oxidation temperature and $H_2O_2$ amount. Also, the performance of NO oxidation was decreased with increasing the space velocity.

• Proceedings of the Korean Vacuum Society Conference
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• 2010.08a
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• pp.171-171
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• 2010

In this work, we investigated the effect of the oxidation temperature on the unipolar and bipolar resistance switching behaviors of the oxidized TiO-x films. TiOx films on Pt electrodes were fabricated by the oxidation of Ti films at $550^{\circ}C$ for 1 to 3 hours. The unipolar and bipolar resistance switching properties were investigated with the oxidation temperature and time. Also, the crystal structure and the physical properties such as chemical bonding states of TiOx layers were characterized in addition to the resistance switching characteristics. The resistance switching behaviors of TiOx films oxidized at above $450^{\circ}C$ and below $650^{\circ}C$ was shown. So, we investigated that the resistance switching behaviors of TiOx films oxidized at $550^{\circ}C$ with the oxidation time from 1 to 3 hour. The memory windows of unipolar switching in the oxidized TiOx films were reduced with increasing the oxidation time, but those of the bipolar switching were slightly enlarged. The enlargement of rutile TiO2 peak with increasing the oxidation time and temperature was studied by X-ray diffraction. An increase of non-lattice oxygen and Ti3+ in the TiOx films with the oxidation times was investigated by X-ray photoemission spectroscopy. It was expected that the uipolar and bipolar resistive switching of the oxidized TiOx film was strongly related with the migration of non-lattice oxygen anions and schottky barrier height, respectively.

• Journal of Powder Materials
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• v.21 no.1
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• pp.55-61
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• 2014

Fe-Cr-Al powder porous metal was manufactured by using new electro-spray process. First, ultra-fine fecralloy powders were produced by using the submerged electric wire explosion process. Evenly distributed colloid (0.05~0.5% powders) was dispersed on Polyurethane foam through the electro-spray process. And then degreasing and sintering processes were conduced. In order to examine the effect of cell size ($200{\mu}m$, $450{\mu}m$, $500{\mu}m$) in process, pre-samples were sintered for two hours at temperature of $1450^{\circ}C$, in $H_2$ atmospheres. A 24-hour thermo gravimetric analysis test was conducted at $1000^{\circ}C$ in a 79% $N_2$ + 21% $O_2$ to investigate the high temperature oxidation behavior of powder porous metal. The results of the high temperature oxidation tests showed that oxidation resistance increased with increasing cell size. In the $200{\mu}m$ porous metal with a thinner strut and larger specific surface area, the depletion of the stabilizing elements such as Al and Cr occurred more quickly during the high-temperature oxidation compared with the 450, $500{\mu}m$ porous metals.

• Nuclear Engineering and Technology
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• v.52 no.9
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• pp.2054-2063
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• 2020

The high-temperature oxidation behavior of ZrSi₂ used as a coating material for nuclear fuel cladding was investigated for developing accident-tolerant fuel cladding of light water reactors. Bulk ZrSi₂ samples were prepared by spark plasma sintering. In situ X-ray diffraction was conducted in air at 900, 1000, and 1100 ℃ for 20 h. The microstructures of the samples before and after oxidation were examined by scanning electron microscopy and transmission electron microscopy. The results showed that the oxide layer of zirconium silicide exhibited a layer-by-layer structure of crystalline ZrO₂ and amorphous SiO₂, and the high-temperature oxidation resistance was superior to that of Zircaloy-4 owing to the SiO₂ layer formed. ZrSi₂ was coated on the Zircaloy-4 tube surface using laser 3D printing, and the coated tube was oxidized for 2000 s at 1200 ℃ under a vapor/argon mixture atmosphere. The outer surface of the coated tube was hardly oxidized (10-30 ㎛), while the inner surface of the uncoated tube was significantly oxidized to approximately 300 ㎛.