• 한국세라믹학회지
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• 제45권12호
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• pp.777-781
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• 2008

Experiments were conducted using SUS430 and Crofer 22 APU steels coated by LSM using plasma spray and slurry spray methods, respectively. High-temperature conductivity and oxidation resistance were investigated. For comparison, SUS430 and Crofer 22 APU without LSM coating were also investigated and coefficient of thermal expansion (CTE) was measured. The results show that the materials without LSM coating exhibit almost the same CTE as YSZ electrolyte in a range of temperatures of $550{\sim}850^{\circ}C$. When coated with LSM, the oxidation rate of the steels decreases by $30{\sim}40%$ using slurry spray and by $10{\sim}30%$ using plasma spray whereas the steels using plasma spray have a better high-temperature conductivity than the steels using slurry spray. It is thus concluded that the LSM coating has a limited effect on increasing high-temperature conductivity while it can effectively reduce the oxidation of the steels.

• Corrosion Science and Technology
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• 제2권3호
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• pp.155-160
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• 2003

Plasma spraying technique was used to fabricate functionally graded coating (FGC) of NiCrAIY/YSZ 8wt%$Y_2O_3-ZrO_2$ on a Co-base superalloy (HAYNES 188) substrate. Six layers were coated on the substrate for building up compositionally graded architecture. Conventional thermal barrier coating (TBC) of NiCrAIY/SZ with sharp interface was also fabricated. As-coated FGC and TBC samples were exposed at the temperature of $1100^{\circ}C$ for 10, 50, 100 hours in air. Microstructural change of thermally exposed samples was examined. Pores and microcracks were formed in YSZ layer due to evolution of thermal internal stress at high temperature. The amount of pores and microcracks in YSZ layer were increased with increasing exposure time at high temperature. High temperature oxidation of coatings occurred mainly at the NiCrAIY/YSZ interface. In comparison with the case of TBC. the increased area of the NiCrAIY/YSZ interface in FGC is likely to attribute to forming the higher amount of oxides.

• 한국재료학회지
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• 제24권7호
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• pp.357-362
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• 2014

Thermal barrier coatings(TBCs) are being applied in many industrial fields such as thermal power generation, aviation and seasonal fields. $ZrO_2-Y_2O_3$(8%) thermal spray coating powders are commercially used as thermal-barrier coating materials to protect against oxidation and corrosion of heat-resistant alloys at elevated temperatures. Currently, $ZrO_2-Y_2O_3$(8%) thermal-spray powder is made using the industrial co-precipitation process, which is very complex and requires a lot of time. In this study, orthorhombic $ZrO_2$ and $Y_2O_3$ powders were fabricated by mechanical mixing, which is more economical than the co-precipitation process. A tetragonal, yttria-stabilized zirconia(YSZ) coating-layer was produced by plasma spraying, using orthorhombic $ZrO_2-Y_2O_3$(8%) powder. Our experimental results indicate that $ZrO_2-Y_2O_3$(8%) mixed powder can be used economically in industry because it is no longer necessary to make this powder by liquid and gas-phase methods.

• 한국전기전자재료학회논문지
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• 제31권4호
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• pp.244-248
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• 2018

We propose a method for improving the reliability of a solar cell by applying a fluorinated surface coating to protect the cell from the outdoor environment using an atmospheric pressure plasma (APP) treatment. An APP source is operated by radio frequency (RF) power, Ar gas, and $O_2gas$. APP treatment can remove organic contaminants from the surface and improve other surface properties such as the surface free energy. We determined the optimal APP parameters to maximize the surface free energy by using the dyne pen test. Then we used the scratch test in order to confirm the correlation between the APP parameters and the surface properties by measuring the surface free energy and adhesive characteristics of the coating. Consequently, an increase in the surface free energy of the cover glass caused an improvement in the adhesion between the coating layer and the cover glass. After treatment, adhesion between the coating and cover glass was improved by 35%.

• Journal of Ceramic Processing Research
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• 제19권6호
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• pp.450-454
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• 2018

In recent years, thermal insulation coating technology for automotive engine parts has received significant attention as a means of improving the thermal efficiency of automotive engines. One of the characteristics of thermal insulation coatings is their low thermal conductivity, and, materials such as YSZ (Yttria-stabilized zirconia), which have low thermal conductivity, are used for this purpose. This research presents a study of the changes in the microstructure and thermal conductivity of $8YSZ/SiO_2$ multi compositional thermal insulation coating for different compositions, and particle size distributions of suspension, when it is subjected to suspension plasma spraying. To obtain a porous coating structure, the mixing ratio of 8YSZ and $SiO_2$ particles and the particle sizes of the $SiO_2$ were changed. The microstructure, phase formation behavior, porosity and thermal conductivity of the coatings were analyzed. The porosities were found to be 1.2-32.1%, and the thermal conductivities of the coatings were 0.797-0.369 W/mK. The results of the study showed that the microstructures of the coatings were strongly influenced by the particle size distributions, and that the thermal conductivities of the coatings were greatly impacted by the microstructures of the coatings.

• 한국재료학회지
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• 제32권6호
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• pp.301-306
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• 2022

This study explored the possibility of forming a coating layer containing alginic acid on the surface of a magnesium alloy to be used as a biomaterial. We formed a coating layer on the surface of a magnesium alloy using a plasma electrolytic oxidation process in an electrolytic solution with different amounts of alginic acid (0 g/L ~ 8 g/L). The surface morphology of all samples was observed, and craters and nodules typical of the PEO process were formed. The cross-sectional shape of the samples confirmed that the thickness of the coating layer became thicker as the alginic acid concentration increased. It was confirmed that the thickness and hardness of the sample significantly increase with increasing alginic acid concentration. The porosity of the surface and cross section tended to decrease as the alginic acid concentration increased. The XRD patterns of all samples revealed the formation of MgO, Mg₂SiO₄, and MgF₂ complex phases. Polarization tests were conducted in a Stimulate Body Fluid solution similar to the body's plasma. We found that a high amount of alginic acid concentration in the electrolyte improved the degree of corrosion resistance of the coating layer.

• Journal of Welding and Joining
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• 제21권4호
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• pp.46-55
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• 2003

TiO$_2$-WO$_3$(8.2wt%) coatings were prepared by the APS (Atmospheric Plasma Spraying) process to clarify the relationship between the process parameters(H$_2$ gas flow rate of plasma 2nd gas and spraying distance) of the APS coating and photo-decomposition efficiency kinetics of the MB(methylene blue) aqueous solution decomposition and to understand the effect of addition of WO$_3$ on photocatalytic properties of TiO$_2$ sprayed coating. Further, the temperature and velocity of flying particles were measured by DPV-2000 to investigate the relationship between microstructure of coatings and process parameters. Properties of coatins were investigated by XRD, SEM, XPS, RAMAN, UV/VIS spectrometer. In case of the TiO$_2$-WO$_3$(8.2wt%) coating, it had a lower anatase fraction than that of pure-TiO$_2$ coatings because of flying in the higher temperature plasma plume by the heavy weight of TiO$_2$, WO$_3$. And, when WO$_3$ added powders were spayed, the doping effects of W ions substituted into the Ti ion sites was not occured during melting and solidification cycles of spraying. It was found that the addition of WO$_3$ was ineffective effective on increasing photo-decomposition efficiency of TiO$_2$ sprayed coating.

• 한국분말재료학회지
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• 제28권4호
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• pp.310-316
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• 2021

The effects of different spray angles (90°, 85°, 80°) on the microstructure and mechanical properties of a Y₂O₃ coating layer prepared using the atmospheric plasma spray (APS) process were studied. The powders employed in this study had a spherical shape and included a cubic Y₂O₃ phase. The APS coating layer exhibited the same phase as the powders. Thickness values of the coating layers were 90°: 203.7 ± 8.5 ㎛, 85°: 196.4 ± 9.6 ㎛, and 80°: 208.8 ± 10.2 ㎛, and it was confirmed that the effect of the spray angle on the thickness was insignificant. The porosities were measured as 90°: 3.9 ± 0.85%, 85°: 11.4 ± 2.3%, and 80°: 12.7 ± 0.5%, and the surface roughness values were 90°: 5.9 ± 0.3 ㎛, 85°: 8.5 ± 1.1 ㎛, and 80°: 8.5 ± 0.4 ㎛. As the spray angle decreased, the porosity increased, but the surface roughness did not show a significant difference. Vickers hardness measurements revealed values of 90°: 369.2 ± 22.3, 85°: 315.8 ± 31.4, and 80°: 267.1 ± 45.1 HV. It was found that under the condition of a 90° angle with the lowest porosity exhibited the best hardness value. Based on the aforementioned results, an improved method for the APS Y₂O₃ coating layer was also discussed.

• 접착 및 계면
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• 제4권1호
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• pp.28-34
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• 2003

강철 타이어 코드의 접착력 향상을 위하여 아세틸렌 플라즈마 중합 코팅, 아르곤 에칭+아세틸렌 플라즈마 중합 코팅, 그리고 아르곤 에칭+담채를 이용한 아세틸렌 플라즈마 중합 코팅을 실시하였으며, 접착력은 TCAT시편으로 측정하였다. 플라즈마 중합 코팅된 타이어 코드의 내구성을 고찰하기 위하여 제 1 단계로 아세틸렌 플라즈마 중합 코팅된 타이어코드를 상온에서 1, 3, 5, 10, 15일 동안 방치한 후 TCAT 시편을 제조하여 접착력변화를 측정하였으며, 제 2 단계로는 플라즈마 중합 코팅된 코드로 TCAT 시편을 제조한 후 증류수, 10% NaCl 수용액에서 또는 $100^{\circ}C$ 오븐에서 1, 2, 3, 4주간 노화시키면서 접착력 변화를 측정하였다. SEM/EDX을 이용하여 코드의 파괴표면을 분석하였으며, 황동코팅과 비교 분석하였다. 아르곤 에칭+담채를 이용한 아세틸렌 플라즈마 중합으로 코팅된 강철 타이어 코드의 접착력은 황동코팅된 시편의 접착력과 거의 같은 수준이었다. 타이어 코드의 상온 노화시험에서 황동코팅된 시편이 아세틸렌 플라즈마 중합 코팅된 시편에 비하여 우수 내구성을 보여주었으나, TCAT 시편의 노화에서는 아세틸렌 플라즈마 중합 코팅이 황동코팅에 비하여 우수하거나 비슷한 결과를 보였다.

• 한국표면공학회지
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• 제31권6호
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• pp.325-333
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• 1998

A duplex surface treatment process of simultaneous aluminizing-chromizing process followed by plasma nitriding was performed on AISI HI3 steel and STS 403 steel. The properties of these duplex-treated steels were investigated and were compared with those of steels treated by single process of either simultaneous aluminizing-chromizing or plasma nilriding, in terms of microstructure, microhardness and high temperature wear resistance. Sim~dtaneous alumizing-chromizing process was done using a 2-step coating cycle and plasma nitriding process was done at $530^{\circ}C$ for 1.5 hour. AISI HI3 steel and STS 403 steel showed a FeA1 compound layer of approximately 350$\mu\textrm{m}$ thickness on the surface after simultaneous diffusion coating and nitrided layer of approximately 70-80$\mu\textrm{m}$ formed after the subsequent plasma nitriding process. The microhardness was improved much more by the duplex surface heatment than only by plasma nitriding. In addition the duplex treated specimens showed an improved high temperature wear resistance.