• Korean Journal of Metals and Materials
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• v.47 no.4
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• pp.235-241
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• 2009

The STS304 stainless steel was oxidized isothermally and cyclically at temperatures between 1050 and $1200^{\circ}C$ for 1 hr in air. During isothermal oxidation, it displayed good oxidation resistance at $1050^{\circ}C$. However, it suffered from breakaway oxidation above $1100^{\circ}C$, being accompanied with internal oxidation. During cyclic oxidation, it also displayed good oxidation resistance at $1050^{\circ}C$, but it suffered from massive weight loss above $1125^{\circ}C$. The oxide scales formed consisted primarily of $Fe_2O_3$, $Fe_3O_4$ with and without $Cr_2O_3$. They were generally non-adherent.

• Metals and materials international
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• v.24 no.6
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• pp.1293-1302
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• 2018

Nanocrystalline (NC) Ni electrodeposits (EDs) with a mean grain size of $34{\pm}12nm$ has been investigated, from room temperature to $800^{\circ}C$ under a purge gas of argon, by both non-isothermal and isothermal differential scanning calorimetry measurements, in combination with characterization of temperature-dependent microstructural evolution. A significant exothermic peak resulting from superimposition of recrystallization and surface oxidation occurs between 340 and $745^{\circ}C$ at a heating rate of $10^{\circ}C/min$ for the NC Ni EDs. The temperatures for recrystallization and oxidation increase with increasing the heating rate. In addition, recrystallization leads to a profound brittle-ductile transition of the Ni EDs in a narrow range around the peak temperature for the recrystallization.

• Proceedings of the Korean Ceranic Society Conference
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• 2004.04b
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• pp.48.2-48.2
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• 2004

• Proceedings of the Materials Research Society of Korea Conference
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• 2005.05a
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• pp.87-87
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• 2005

• Carbon letters
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• v.9 no.2
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• pp.121-126
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• 2008

High modulus pitch based carbon fibers (HM) were exposed to isothermal oxidation using tube furnace in carbon dioxide gas to study the oxidation kinetics under the temperature of $800-1100^{\circ}C$. The kinetic equation $f=1-{\exp}(-at^b)$ was introduced and the constant b was obtained in the range of 1.02~1.42. The oxidation kinetics were evaluated by the reaction-controlling regime (RCR) depending upon the apparent activation energies with the conversion increasing from 0.2 to 0.8. The activation energies decrease from 24.7 to 21.0 kcal/mole with the conversion increasing from 0.2 to 0.8, respectively. According to the RCR, the reaction was limited by more diffusion controlling regime for the HM fibers with the conversion increasing. Therefore, it seems that the oxidation which is under the diffusion controlling regime takes place continuously from the skin to the core of the fiber.

• Journal of the Korean Chemical Society
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• v.55 no.5
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• pp.819-823
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• 2011

The relationship between the microstructure, mechanical properties, and oxidation behavior of pitch-, polyacrylonitrile (PAN)-, and Rayon-based carbon fibers (CFs) has been studied in detail. Three types of carbon fiber were exposed to isothermal oxidation in air and the weight change was measured by thermogravimetric analyzer (TGA) apparatus. After activation energy was gained according to the conversion at reacting temperature, the value of specific surface area and the surface morphology was compared, and the reaction mechanism of oxidation affecting development of pores of carbon fibers was examined. This study will lead to a new insight into the relationship between the microstructure and mechanical properties of carbon fibers.

• Journal of the Korean institute of surface engineering
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• v.29 no.6
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• pp.607-614
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• 1996

Yttrium(Y) coating was incorporated by ion-plating method either directly on the TiAl substrate or after pack aluminizing on TiAl to improve the oxidation resistance of TiAl alloy. After Y-coating, heat treatment at low oxygen partial pressure was carried out. Performance of various coating was evaluated by isothermal and cyclic oxidation tests. A simple Y-coating without pack aluminizing can give a detrimental effect on the. oxidation resistance of TiAl alloy, because it enhances formation of $TiO_2$. On the other hand, a composite coating of aluminide-yttrium has shown excellent oxidation resistance. A continuous protective $Al_2O_3$ scale is formed on the aluminized TiAl, and Y-coating improves $Al_2O_3$ scale adherence and substantially prevents depletion of Al in the aluminide-coating layer.

• Corrosion Science and Technology
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• v.7 no.4
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• pp.233-236
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• 2008

Halide-activated pack cementation was utilized to deposit B-doped silicide coating. The pack powders were consisted of $3Wt.c/oNH_4Cl$, 7Wt.c/oSi, $90Wt.c/oAl_2O_3+TiB_2$. B-doped silicide coating was consisted of two layers, an outer layer of $NbSi_2$ and an inner layer of $Nb_5Si_3$. Isothermal oxidation resistance of B-doped silicide coating was tested at $1250^{\circ}C$ in static air. B-doped silicide coating had excellent oxidation resistance, because continuous $SiO_2$ scale which serves as obstacle of oxygen diffusion was formed after oxidation.

• Journal of the Korean institute of surface engineering
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• v.28 no.6
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• pp.333-342
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• 1995

Stainless steels are widely selected as commercial engineering materials mainly because of their excellent corrosion resistance, oxidation resistance and strength. Because the manufacturing temperature of stainless steels is relatively high, the chemical and physical properties of the oxide film which was formed on the stainless steels are of importance in determining the rate of oxidation and the life of equipment exposed to high temperature oxidizing environments. In this study, the oxidation behavior of S. S. 304 and S. S. 430 added by a small amount of oxygen active elements(each +0.5wt% Hf and Y) was studied to improve oxidation resistance. The results of cyclic and isothermal oxidation on S. S. 304 added by OAE showed relatively poor oxidation resistance due to spallations and cracks of $Cr_2O_3$ layer. But all S. S. 430+0.5wt% OAE maintained constant oxidation rates and stable oxide layers at high temperature environment. Especially S. S. 430+0.5wt% Y formed a $Cr_2O_3$ oxide layer and improved cyclic oxidation resistance preventing loss of protective layers about 1000 hours at $1000^{\circ}C$

• Nuclear Engineering and Technology
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• v.41 no.2
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• pp.163-170
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• 2009

In order to evaluate high-temperature oxidation behavior of the advanced alloy cladding under LOCA conditions, isothermal oxidation tests in steam were performed with cladding specimens prepared from high burnup PWR fuel rods that were irradiated up to 79 MWd/kg. Cladding materials were $M5^{(R)}$ and $ZIRLO^{TM}$, which are Nb-containing alloys. Ring-shaped specimens were isothermally oxidized in flowing steam at temperatures from 1173 to 1473 K for the duration between 120 and 4000s. Oxidation rates were evaluated from measured oxide layer thickness and weight gain. A protective effect of the preformed corrosion layer is seen for the shorter time range at the lower temperatures. The influence of pre-hydriding is not significant for the examined range. Alloy composition change generally has small influence on oxidation in the examined temperature range, though $M5^{(R)}$ shows an obviously smaller oxidation constant at 1273 K. Consequently, the oxidation rates of the high burnup $M5^{(R)}$ and $ZIRLO^{TM}$ cladding are comparable or lower than that of unirradiated Zircaloy-4 cladding.