• Korean Journal of Metals and Materials
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• v.48 no.10
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• pp.907-913
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• 2010

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

• Journal of the Korean Society for Heat Treatment
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• v.20 no.5
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• pp.231-236
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• 2007

High velocity oxy-fuel (HVOF) spraying was used to coat Ti(Al,O)/$Al_2O_3$ powder onto the SS41 steel plate. Macrostructure of the coated specimen has been investigated by scanning electron micrograph (SEM). High temperature oxidation behavior of the coated specimen and SS41 steel have been studied. From the results of SEM observation, Ti(Al,O)/$Al_2O_3$ powder was coated well onto the substrate SS41 steel. Porosity onto the coated layer was only 0.38%. The oxidation results showed that Ti(Al,O)/$Al_2O_3$ powder coated SS41 steel have improved little oxidation resistance at $900^{\circ}C$ in air, but improved remarkably oxidation resistance at $800^{\circ}C $ in air compare to the substrate SS41 steel.

• Proceedings of the KIEE Conference
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• 1998.11c
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• pp.947-949
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• 1998

In this paper, the NO was oxidized $NO_2$ by using the non-thermal plasma and NOx removal characteristics were measured by showering NaOH water-solution to $NO_2$. The NO oxidation increased in the order of DC, AC, and Pulse. NOx oxidation for two stage with applied voltage was better than that for one stage with applied voltage. NO oxidation didn't depend on applied voltage. While NO oxidation was going on, NOx removal efficiency was 20-25%, however, significantly depended on the injection method of air and $H_2O$ + air. When NaOH water-solution density of 20% was showered to flue gases, NOx removal efficiency increased to 64%.

• Carbon letters
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• v.6 no.1
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• pp.31-40
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• 2005

The carbon nanofibers (CNFs) were synthesized through the catalytic decomposition of hydrocarbons in a quartz tube reactor. The CNFs prepared from $C_3H_8$ at $550^{\circ}C$ was selected as the purification sample due to the higher content of impurity than that prepared from other conditions. In this study, we carried out the purification of CNFs by oxidation in air or carbon dioxide after acid treatment, and investigated the influence of purification parameters such as kind of acid, concentration, oxidation time, and oxidation temperature on the structure of CNFs. The metal catalysts could be easily eliminated from the prepared CNFs by liquid phase purification with various acids and it was verified by ICP analysis, in which, for example, Ni content decreased from 2.51% to 0.18% with 8% nitric acid. However, the particulate carbon and heterogeneous fibers were not removed from the prepared CNFs by thermal oxidation in air and carbon dioxide. This result can be explained by that the direction of graphene sheet in CNFs is vertical to the fiber axis and the CNFs are oxidized at about the similar rate with the impurity carbon.

• Journal of the Korean institute of surface engineering
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• v.46 no.2
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• pp.80-86
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• 2013

Magnesium alloys of AZ31 containing (0.5, 1, 1.5) wt.% of initially added CaO particles were cast in air, and their oxidation behavior was studied at $450-650^{\circ}C$ in air. The initially added CaO particles either decomposed to dissolve in the ${\alpha}$-Mg matrix or precipitated as $Al_2Ca$ along the grain boundaries of the matrix during casting. The ignition temperatures were $565.4^{\circ}C$ for AZ31, $608.6^{\circ}C$ for AZ31+0.5 wt.%CaO, and $689.7^{\circ}C$ for AZ31+1 wt.%CaO. No ignition occurred for AZ31+1.5 wt.%CaO up to $700^{\circ}C$, displaying good oxidation resistance. The CaO-rich oxide scales that formed on the surface of the AZ31+(0.5, 1, 1.5) wt.%CaO alloys improved the oxidation resistance of AZ31 alloys.

• Journal of Sensor Science and Technology
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• v.27 no.1
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• pp.13-20
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• 2018

Gas sensors based on metal oxide semiconductors are used in numerous applications including monitoring indoor air quality and detecting harmful substances like volatile organic compounds. Nanostructures, for example, nanoparticles, nanotubes, nanodomes, and nanofibers have been widely utilized to improve gas sensing properties of metal oxide semiconductors, and this increases the effective surface area, resulting in participation of more target gas molecules in the surface reaction. In the recent times, 1-dimensional (1D) metal oxide nanostructures fabricated using anodic oxidation have attracted great attention due to their high surface-to-volume ratio with large-area uniformity, reproducibility, and capability of synthesis under ambient air and pressure, leading to cost-effectiveness. Here, we provide a brief overview of 1D metal oxide nanostructures fabricated by anodic oxidation and their gas sensing properties. In addition, recent progress on thin film-based anodic oxidation for application in gas sensors is introduced.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.16 no.4
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• pp.349-354
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• 1983

A study on the color changes of fish meat during drying was conducted using fishes with different lipid contents, such as Alaska pollack as lean fish, conger eel as white fleshed fatty fish, and sardine as dark fleshed fatty fish. The fish meat was dried in a forced air dryer for 20 hours at 40, 55 and $70^{\circ}C$, The air velocity was 0.4 m/sec and the relative humidity of air was controlled to a constant value in the range of 10 to $50\%$. The color changes were evaluated with the brown color densities developed by lipid oxidation and Maillard reaction. The predominant reaction for the brown color developed during drying was lipid oxidation, The more the lipid content of fish and the higher the drying temperature were, the more violent the oxidative reaction of Lipid was. The rate of lipid oxidation during drying at 40 and $55^{\circ}C$ was affected by the relative humidity of air and was the slowest around $30\%$. But no remarkable influence of relative humidity on the rate of lipid oxidation could be confirmed during drying at $70^{\circ}C$. It seemed that the rate of lipid oxidation at higher temperature was more sensitive to the temperature than the relative humidity of air. Maillard reaction showed not so significant influence on the color changes of fish meat during drying. The rate of reaction was increased with increasing relative humidity of air in the range of 10 to $50\%$.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.33 no.3
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• pp.192-197
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• 2000

To develop plain dried products of large anchovy, Engraulis japonica, lipid oxidation during drying of large anchovy and optimal drying condition were investigated. The moisture contents of large anchovy on 7 hrs dryness were $ 9.0{\%},\;34.0{\%},\;38.0{\%} and\;38.8{\%}\;in\;60^{\circ}C$ hot-air drying (wind velocity, 1.4m/sec), $40^{\circ}C$ hot-air drying (wind velocity, 1.4 m/sec), sun drying($30{\pm}5^{\circ}C$) and $20^{\circ}C$ cold-air drying (wind velocity, 3.1 m/sec), respectively. The cold-air drying depressed remarkably the lipid oxidation of large anchovy during drying, resulting from AV, POV, COV and the formation of browning pigment. The fatty acid composition of large anchovy was $35.8{\%} in saturates, 20.0{\%} in monoenes and 44.2{\%}$ in polyenes. Saturates and monoenes were increased in proportion to the increase of drying time, while polyenes were decreased. The contents of 20 : 5 and 22 : 6 of polyenes were decreased remarkably in proportion to the progress of lipid oxidation, while 14 : 0, 16 : 0, 16 : 1 and 18 : 1 of saturates and monoenes were increased. The changes in fatty acid compositions by drying conditions were remarkably clarified in sun drying, followed by $60^{\circ}C$ hot-air drying $40^{\circ}C$ hot-air drying and $20^{\circ}C$ cold-air drying in order.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2004.08a
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• pp.285-293
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• 2004

Oxidation behavior of 304 and 430 stainless steel were studied using thin film X-ray analysis and glow discharge spectrum analysis (here-after GDS). The oxidation layer of 304 stainless steel was composed of $Cr_2O_3\;and\;FeCrO_4$ and its thickness was about $1.5{\mu}m$ after $1\~5$ minutes of annealing at $1120^{\circ}C$ open air. However, the oxidation layer of 430 stainless steels was mainly composed of $Cr_2O_3$ and its typical thickness was 0.5um after $1\~5$ minutes of annealing at $1000^{\circ}C$ open air. Electro-chemical analysis revealed that the descaling of oxidation layer could be activated by Fe, Cr dissolution from the matrix behind the oxidation layer at the current density of $5\~10ASD$ and by Fe, Cr-oxide dissolution from the oxidation layer at the current density over than 10ASD. Electrolytic stripping of 430 and 304 revealed the intial incubation period of descaling by oxygen evolving at low current density range such as $5\~10ASD$. However the dissolution of oxide layer was occurred when applying the anodic current of $10\~20ASD$ on 430 and 304 stainless steels. It was suggested that the electrolytic pickling of high Cr bearing stainless steel such as 430 and 304 seemed to be the more effective in the high current density range such as $10\~20ASD$ than the low current density range such as $5\~10ASD$.

• Carbon letters
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• v.18
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• pp.18-23
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• 2016

Polyacrylonitrile (PAN)-based carbon fibers have high specific strength, elastic modulus, thermal resistance, and thermal conductivity. Due to these properties, they have been increasingly widely used in various spheres including leisure, aviation, aerospace, military, and energy applications. However, if exposed to air at high temperatures, they are oxidized, thus weakening the properties of carbon fibers and carbon composite materials. As such, it is important to understand the oxidation reactions of carbon fibers, which are often used as a reinforcement for composite materials. PAN-based carbon fibers T300 and T700 were isothermally oxidized in air, and microstructural changes caused by oxidation reactions were examined. The results showed a decrease in the rate of oxidation with increasing burn-off for both T300 and T700 fibers. The rate of oxidation of T300 fibers was two times faster than that of T700 fibers. The diameter of T700 fibers decreased linearly with increasing burn-off. The diameter of T300 also decreased with increasing burn-off but at slower rates over time. Cross-sectional observations after oxidation reactions revealed hollow cores in the longitudinal direction for both T300 and T700 fibers. The formation of hollow cores after oxidation can be traced to differences in the fabrication process such as the starting material and final heat treatment temperature.