• Korean Journal of Metals and Materials
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• v.46 no.10
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• pp.652-661
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• 2008

Reduction of NOx in emission gas, improvement of engine efficiency, and extension of warranty period has made demands for developing materials more corrosively resistant to the inner-muffler environments or predicting the lifetime of materials used in muffler more precisely. The corrosion inside muffler has been explained with condensate corrosion mainly though thermal oxidation experiences prior to condensate corrosion. Hence, the aim of this study is to describe how the thermal oxidation affects the corrosion of stainless steel exposed to the inner-muffler environments. Auger electron spectroscopy and electrochemical tests were employed to analyze oxide scale and to evaluate corrosion resistance, respectively. Thermal oxidation has different role of condensate corrosion depending on the temperature: inhibiting condensate corrosion below $380^{\circ}C$ and enhancing condensate corrosion above $380^{\circ}C$. The low temperature oxidation causes to form compact oxide layer functioning a barrier for penetrating condensate into a matrix. Although though thermal oxidation caused chromium-depleted layer between oxide layer and matrix, the enhancement of the condensate corrosion in high temperature oxidation resulted from corrosion-induced crevice formed by oxide scale rather than corrosion in chromium-depleted layer. It was proved by aids of anodic polarization tests and measurements of pitting corrosion potentials. By the study, the role of high temperature oxidation layer affecting the condensate corrosion of stainless steels used as muffler materials was well understood.

• Korean Journal of Materials Research
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• v.15 no.4
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• pp.233-239
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• 2005

In this study, the effects of Pd buffer layer on the oxidation resistance of Pt modified-pack aluminized Inconel 738LC, used for gas turbine, were investigated. Pd was electroplated on Inconel 738LC, and Pt was electroplated on the electroplated Pd surface. Thus, the thickness of electroplated Pt/Pd was $10\;{\mu}m$ and the atomic ratio of Pt : Pd was about 6 : 4. After Pt/Pd electroplating, Inconel 738LC was pack aluminized to form the oxidation resistant layer. To investigate the oxidation resistance of Pt/Pd modified-pack aluminized Inconel 738LC, iso-thermal oxidation and cyclic oxidation were performed. The iso-thermal oxdation and the cyclic oxidation data indicated that the Pt/Pd modified-pack aluminized Inconel 738LC was more oxidation resistant than the Pt modified-pack aluminized Inconel 738LC. It was thought that the difference of thermal expansion coefficient between Inconel 738LC and Pt was lowered by the Pd buffer layer.

• Journal of the Korean institute of surface engineering
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• v.32 no.1
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• pp.49-60
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• 1999

The protective oxide scales and coatings formed on high temperature materials must be preserved in high temperature atmosphere. And the thermal stresses induced by thermal cycling and the growth stresses by the formation of oxide scales can cause the loss of adherence and spalling of the oxide scales and coated layers. Among the coating processes Al diffusion coating is favored due to thermochemical stability and superior adherence in an hostile atmosphere. In this study, protective oxide forming element, Al was coated on Ni, Inconel 600 and 690 by diffusion coating process varying coating temperature and time. And the surface stability and adherence of oxide scales formed on those Al diffusion coated materials were evaluated by thermal cycling test. Al diffusion coated specimens showed superior cyclic oxidation resistance compared to bare ones and specimens coated for longer period had better cyclic oxidation resistance, due to the abundant amount of Al in the coated layer. Meanwhile Al diffusion coated Inconel 600 and 690 showed improved cyclic oxidation resistance by the effect of Al in the coated layer and Cr in the substrate. Comparing both Al diffusion coated Inconel 600 and 690, Al diffusion coated Inconel 690 maintained better adhesion between coated layer and substrate by virtue of the bridging effect resulting from the segregation of Cr in the interdiffusion zone.

• Journal of the Korean institute of surface engineering
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• v.39 no.4
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• pp.147-152
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• 2006

Failure mechanisms of electron beam physical vapor deposited thermal barrier coatings(EB-PVD TBCs) that occur during thermal cyclic oxidation were investigated. The investigations include microstructural degradation of NiCrAIY bond coat, thermally grown oxides(TGOs) along the ceramic top coat-substrate interface and fracture path within TBCs. The microstructural degradation of the bond coat during cyclic oxidation created Al depleted zones, resulting in reduction of NiAl and ${\gamma}$-Ni solid solution phase. It was observed that the fracture took placed primarily within the TGOs or at the interfaces between TGOs and bond coat.

• Carbon letters
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• v.6 no.2
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• pp.71-78
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• 2005

Anti-oxidation coatings are the key technique for carbon/carbon (C/C) composites used as the thermal structural materials. The microstructure and oxidation behavior of several kinds of high-performance ceramic coatings for C/C composites prepared in Northwestern Polytechnical University were introduced in this paper. It showed that the ceramic coatings such as SiC, Si-$MoSi_2$, SiC-$MoSi_2$, $Al_2O_3$-mullite-SiC and SiC/yttrium silicate/glass coatings possessed excellent oxidation resistance at high temperatures, and some of these coatings were characterized with excellent thermal shock resistance. The SiC-$MoSi_2$ coating system has the best oxidation protective property, which can effectively protect C/C composites from oxidation up to 1973 K. In addition, the protection and failure reasons of some coatings at high temperature were also provided.

• 한국신재생에너지학회:학술대회논문집
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• 2011.05a
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• pp.122.1-122.1
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• 2011

Phosphorus is known to pile-up at the silicon surface when it is thermally oxidized. A thin layer, about 40nm thick from the silicon surface, is created containing more phosphorus than the bulk of the emitter. This layer has a gaussian profile with the peak at the surface of the silicon. In this study the pile-up effect was studied if this layer can act as a front surface field for solar cells. The effect was also tested if its high dose of phosphorus at the silicon surface can lower the contact resistance with the front metal contact. P-type wafers were first doped with phosphorus to create an n-type emitter. The doping was done using either a furnace or ion implantation. The wafers were then oxidized using dry thermal oxidation. The effect of the pile-up as a front surface field was checked by measuring the minority carrier lifetime using a QSSPC. The contact resistance of the wafers were also measured to see if the pile-up effect can lower the series resistance.

• Korean Journal of Metals and Materials
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• v.48 no.6
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• pp.514-522
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• 2010

Graphite epoxy composite material (GECM) shows high specific strength and its application in the aerospace industry is gradually increasing. However, its application would induce galvanic corrosion between GECM and metallic materials. This work focused on the effects of anodizing and thermal oxidation on galvanic corrosion in a 3.5% NaCl solution between GECM and aluminium and titanium. In the case of anodized aluminium, galvanic corrosion resistance to the GECM was greatly improved by the anodizing treatment regardless of area ratio. In the case of anodized titanium, the anodizing by a formation voltage of 50V increased corrosion resistance of titanium in galvanic tests. Thermal oxidation of titanium also improved corrosion resistance of Ti to GECM.

• Korean Journal of Metals and Materials
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• v.48 no.11
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• pp.981-988
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• 2010

The effects of Cr and Al contents in Fe-Al and Fe-Cr alloys on oxidation resistance, hardness, and the thermal expansion coefficient were investigated. Fe-Al and Fe-Cr alloys above 10wt.%Al and 20wt.%Cr contents have a high oxidation resistance. The hardness of the Fe-Al and Fe-Cr alloys increased with an increase in Al and Cr contents due to solid solution or formation of an intermetallic compound. The coefficients of thermal expansion of the Fe-Al alloys were higher than those of the Fe-Cr alloys because the coefficient of thermal expansion of Al was higher than that of Fe and Cr.

• Journal of the Korean Ceramic Society
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• v.33 no.7
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• pp.832-838
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• 1996

Thermite reaction products of MgO and Al were added to MgO-C refractory to improve the properties of corrosion against the attack of slag, oxidation and mechanical spalling. Corrosion rate of MgO-C-MgAl2O4 spinel refractory at the ratio of 3.3(CaO/SiO2) slag was smaller than that of MgO-C and MgO-C-Al refractory. The excellent corrosion resistance of the MgO-C-MgAl2O4 spinel refractory against the slag attack was appeared by Al and MgAl2O4 spinel with high melting point and corrosion resistance and the high thermal conductivity and low thermal expansion of AIN. Hot M.O.R at 140$0^{\circ}C$ and the resistance of oxidation weight loss at 90$0^{\circ}C$ were 210kg/cm2 and -12% respectively.

• Progress in Superconductivity and Cryogenics
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• v.24 no.4
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• pp.40-45
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• 2022

The electrical/thermal stabilities and magnetic field controllability of a no-insulation (NI) high-temperature superconducting magnet are characterized by contact resistance between turn-to-turn layers, and the contact resistance characteristics are determined by properties of conductor surface and winding tension. In order to accurately predict the electromagnetic characteristics of the NI coil in a design stage, it is necessary to control the contact resistance characteristics within the design target parameters. In this paper, the contact resistance and critical current characteristics of a rare-earth barium copper oxide (REBCO) conductor were measured to analyze the effects of surface treatment conditions (roughness and oxidation level) of the copper stabilizer layer in REBCO conductor. The test samples with different surface roughness and oxidation levels were fabricated and conductor surface analysis was performed using scanning electron microscope, alpha step surface profiler and energy dispersive X-ray spectroscopy. Moreover, the contact resistance and critical current characteristics of the samples were measured using the four-terminal method in a liquid nitrogen impregnated cooling environment. Compared with as-received REBCO conductor sample, the contact resistance values of the REBCO conductors, which were post-treated by the scratch and oxidation of the surface of the copper stabilizer layer, tended to increase, and the critical current values were decreased under certain roughness and oxidation conditions.