• Nuclear Engineering and Technology
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• 제41권2호
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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.

• 연구논문집
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• 통권29호
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• pp.141-149
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• 1999

Brazing of Fe-Cr-Al alloy was carried out at $1200^{\circ}C$ in vacuum furnace using nickel-based filler metals : BNi-5 powder(Ni-Cr-Si-Fe base alloy} and MBF-50 foil (Ni-Cr-Si-B). The effect of boron content on the stability of oxide scale on the brazed joint was investigated by means of cyclic oxidation test performed at $1050^{\circ}C$ and $1200^{\circ}C$. Apparently, the joints brazed with MBF-50 containing boron showed relatively stable oxidation rates compared to boron-free BNi-5 at both temperatures. However, it was considered that the slower weight loss of MBF-50 brazed specimen wasn’t resulted from the low oxidation rate but from the spallation of oxide layer. The oxide layer consisted of thick spinel oxide on the surface and $Al_2 O_3$ internal oxide layer along the interface between mother alloy and braze, the mother alloy was also eroded seriously by the formation of spinel oxides such as $FeCr_2 O_4$ and $NiCr_2 O_4$ on the surface, likely to be induced by the change of oxide forming mechanism due to diffusion of boron from the braze. On the contrary, the joint brazed with BNi-5 showed the good oxidation resistance during the cyclic oxidation test. It seems that the oxidation can be retarded by the formation of stable $Al_2 O_3$ layer at the surface.

• 한국재료학회지
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• 제12권9호
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• pp.718-723
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• 2002

$Ti_{1-x}$ $Al_{ x}$N thin films as barrier layer for memory devices application were deposited by reactive magnetron sputtering. The crystallinity, micro-structure, oxidation resistance and oxidation mechanism of films were investigated as a function of Al content. Lattice parameter and grain size of thin films were decreased with increasing the Al content Oxidation of the film with higher Al content is slow and then, total oxide thickness is thinner than that of lower Al content film. Oxide layer formed on the surface is AlTiNO layer. Oxidation of $Ti_{1-x}$ /$Al_{x}$ N barrier layer is diffusion limited process and thickness of oxide layer with oxidation time increased with a parabolic law. The activation energy of oxygen diffusion, Ea and diffusion coefficient, D of $Ti_{0.74}$ /X$0.74_{0.26}$N film is 2.1eV and $10^{-16}$ ~$10^{-15}$ $\textrm{cm}^2$/s, respectively. $_Ti{1-x}$ /$Al_{x}$ XN barrier layer showed good oxidation resistance.

• Nuclear Engineering and Technology
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• 제52권12호
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• pp.2880-2886
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• 2020

A small leak occurring on the surface of a fuel rod due to damage exposes UO₂ to a steam atmosphere. During this time, fission gas trapped inside the fuel rod leaks out, and the gas leakage can be increased due to UO₂ oxidation. Numerous studies have focused on the steam oxidation and its thermodynamic calculation in UO₂. However, the thermodynamic calculation of the UO₂ oxidation in a pressurized water reactor (PWR) environment has not been studied extensively. Moreover, the kinetics of the oxidation of UO₂ pellet also has not been investigated. Therefore, in this study, the thermodynamics of UO₂ oxidation under steam injection due to a damaged fuel rod in a PWR environment is studied. In addition, the diminishing radius of the UO₂ pellet with time in the PWR environment was calculated through an experiment simulating the initial time of steam injection at the puncture.

• 한국분말재료학회지
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• 제20권1호
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• pp.48-52
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• 2013

A study of oxidation kinetic of Fe-36Ni alloy has been investigated using thermogravimetric apparatus (TGA) in an attempt to define the basic mechanism over a range of temperature of 400 to $1000^{\circ}C$ and finally to fabricate its powder. The oxidation rate was increased with increasing temperature and oxidation behavior of the alloy followed a parabolic rate law at elevated temperature. Temperature dependence of the reaction rate was determined with Arrhenius-type equation and activation energy was calculated to be 106.49 kJ/mol. Based on the kinetic data and micro-structure examination, oxidation mechanism was revealed that iron ions and electrons might migrate outward along grain boundaries and oxygen anion diffused inward through a spinel structure, $(Ni,Fe)_3O_4$.

• 대한전자공학회논문지
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• 제25권7호
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• pp.759-766
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• 1988

the effect of heat treatment in oxygen ambient on the nucleation and growth of oxidation induced stacking faults(OSF) in n-type(100)silicon wafer has been investigated. The growth of OSF is determind as a function of oxygen concentration in silicon wafer, heat treatment time and temperature, and the activation energy for the growth of OSF can be obtained from the growth kinetics. The activation energies are respectively 2.66 eV for dry oxidation and 2.37 eV for wet oxidation. In this paper, we have also studied the structural feature of OSF with the comparison of optical microscopic morphology and crystalline structure.

• 한국전기전자재료학회논문지
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• 제25권4호
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• pp.294-297
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• 2012

In this work, local oxidation behavior in phosphorous ion-implanted 4H-SiC has been investigated by using atomic force microscopy (AFM). The AFM-local oxidation (AFM-LO) has been performed on the implanted samples, with and without activation anneal, using an applied bias (~25 V). It has been clearly shown that the post-implantation annealing process at $1,650^{\circ}C$ has a great impact on the local oxidation rate by electrically activating the dopants and by modulating the surface roughness. In addition, the composition of resulting oxides changes depending on the doping level of SiC surfaces.

• 한국표면공학회지
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• 제33권5호
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• pp.365-372
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• 2000

Pure $Fe_3$Al alloys with three different compositions of Fe-21.8%Al, Fe-24.1%Al and Fe-27.2%Al were prepared by vacuum induction melting followed by homogenization and hot forging. The long-time oxidation behavior of the prepared alloys was studied at 1073, 1273 and 1473k in air. The oxidation resistance greatly increased with an increase in Al contents. Thin and uniform oxide scales were always formed on Fe-27.2%Al, while thick and fragile oxide scales were formed on Fe-(21.8, 24.1%)Al. Internal oxidation was observed in Fe-(21.8, 24.1%)Al, when oxidized above 1273K. The major oxidation product of all the oxidized alloys was always $\alpha$-$Al_2$$O_3$.

• 한국표면공학회지
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• 제20권2호
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• pp.60-73
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• 1987

For the purpose of improving the cyclic oxidation resistance of Ni-base superalloy, Inconel 600, aluminide coating methods are studied. The formation rate of aluminide coating layers is measured as a function of time and pack composition to find out the optimum coating condition. The evaluation of cyclic oxidation is established by the change in weight, the microphotography and EPMA of cross sectional area during $200^{\circ}C\;{\leftrightarrow}\;950^{\circ}C\;and\;200^{\circ}C\;{\leftrightarrow}\;1100^{\circ}C$, respectively. The thickness of coating layer and weight gains are parabolic behavior in propotion to time and Al contents. In pack of low aluminum contents, 2 wt%, however, weight gain is decreased when activator, $NH_4Cl$ is higher than 2 wt%. The cyclic oxidation resistance of the coating carried out at 1100$^{\circ}C$ are superior to those of the coating diffusion-treated after pack cementation at 800$^{\circ}C$. Aluminide oxide, which is formed in external scale, is barrier to the cyclic oxidation.

• 한국표면공학회:학술대회논문집
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• 한국표면공학회 2007년도 춘계학술발표회 초록집
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• pp.73-73
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• 2007

Amorphous BON and Si-DLC thin films were synthesized by the RF plasma enhanced CVD method, and their oxidation behavior was studied up to $500^{\circ}C$ in air. The oxidation of both films was accompanied by evaporation of volatile species. The oxidation of BON film was preceded by nitrogen escape from the film, and oxygen penetration into the film. The oxidation of Si-DLC film was preceded by carbon escape probably as CO or $CO_2$from the film, and oxygen penetration into the film. The inwardly transported oxygen simply stayed in the oxidized BON and Si-DLC thin films.