• 한국진공학회지
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• 제12권S1호
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• pp.21-27
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• 2003

Micro-arc discharge oxidation (MDO) is a cost-effective plasma electrolytic process which can be used to improve the wear and corrosion resistance of Al-alloy parts by forming a alumina coating on the component surface. However, the MDO coated Al-alloy components often exhibit relatively high friction coefficients and low wear resistance fitted with many counterface materials, additionally, the pitting corrosion for the MDO coated AI-alloy components, especially for a thinner alumina coating, often occurs in atmosphere circumstance due to the porous alumina coats. Therefore, a duplex treatment, combining a MDO coated ahumina thin layer with a TiN coating, prepared by magnetron sputtering (MS), has been investigated. The Vicker's microhardness, pin-on-disc, electrochemical measurement, salt spray, XRD and SEM tests were used to characterize and analyze the treated samples. The work demonstrates that the MDO/MS coated samples have a combination of a very low friction coefficient and good wear resistance as well as corrosion since the micro-holes on alumina coating are partly or fully covered by TiN material.

• 한국표면공학회:학술대회논문집
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• 한국표면공학회 2018년도 춘계학술대회 논문집
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• pp.124-124
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• 2018

Polydopamine은 수중 접착력, 친환경 접착제, nanoparticle absorption 등 다양한 특성으로 많이 연구되고 있는 소재이다. 본 연구에서는 dopamine을 이용하여 수중 금속을 흡착시키는 thin film을 제작하였다. 종래의 Polydopamine coating 방법으로 wet coating 이 사용되고 있다. 하지만 wet 방식의 경우 시간이 오래 걸릴 뿐만 아니라 in-line, roll to roll 방식을 적용하는 것이 어렵기 때문에 생산적이지 않다. 이에 본 연구에서는 Atmospheric Pressure Plasma(APP)를 이용 하여 Polydopamine-like film을 coating 하였다. APP의 경우 vacuum system, solution tank가 필요 없고 in-line, roll to roll 방식을 적용 할 수 있기 때문에 더 경제적이고 생산적인 공정이다. 또한 기존의 Plasma polymerization 방법은 Plasma energy가 높기 때문에 source의 분자구조가 바뀌거나 atom 단위로 분해된다. source의 분자구조가 바뀌는 "Atomic polymerization", Neiswender-Rosskamp Mechanism이 적용되면 wet 방식 coating한 film과는 다른 특성을 갖게 된다. 하지만 APP polymerization은 Plasma energy가 vacuum plasma 보다 매우 낮기 때문에 stile polymerization mechanism을 구현 하는데 적합 하다. stile polymerization mechanism은 Plasma 내부에서 polymer source를 분해 성장 시켜서 Polymer film 얻는 것이 아닌 source의 분자구조가 깨지지 않으면서 polymer growing 시키는 방법이다. dopamine source의 분자구조를 최대한 유지하려고 하는 이유는 metal absorption과 같은 특성이 dopamine chemical structure에 영향을 받기 때문이다. 많은 논문들에서 dopamine의 catechol group이 metal absorption, adhesion force에 영향을 주는 주요 인자라고 주장하고 있기 때문이다. 그래서 본 논문에서는 Dopamine source의 형태를 보존하면서 Polymerization 하는 방법으로 APP process를 사용 하여 낮은 전압에서 Polydopamine-like film을 제작 하였다. APP system 의 Plasma 방전부 에 Dopamine source를 유입하기 위하여 본 논문에서는 Piezo Spray 방식을 사용 하였다. Dopamine을 evaporator 하는 것이 어렵고 chemical composition이 유사한 monomer를 사용해서 Plasma Polymerization으로 Dopamine 분자 구조를 재현하는 것도 어렵다. 그래서 본 연구에서는 Dopamine을 water에 immerse 하고 Dopamine solution을 mist 상태로 만들어서 Plasma discharge area에 유입하였다. 이러한 방법으로 만들어진 film은 Polydopamine film은 아니지만 Polydopamine film과 유사한 Chemical composition, chemical structure, metal absorption을 갖는 것을 FT-IR, SEM, XPS을 이용 하여 확인 하였다. Dopamine source의 보존에 대하여 명확하게 확인하기 위하여 FT-IR을 측정 하였다. 전압에 따른 Benzene ring, hydroxyl group의 비율을 확인 하였다. 낮은 전압으로 coating 된 Polydopamine-like film 일수록 hydroxyl group peak($3400{\sim}3000cm^{-1}$)과 비교하여 Benzene ring peak($1600{\sim}1580cm^{-1}$ and $1510{\sim}500cm^{-1}$)이 흡수를 더 많이 하는 것을 확인 할 수 있다. 이것은 Benzene ring이 파괴되지 않고 보존되는 것을 보여준다. Dopamine에서 Benzene ring은 absorption main factor인 catechol에 있는 chemical structure이다. 즉 Benzene ring peak이 높을수록 Catechol이 잘 보존 되었다는 의미 이다. Catechol의 보존은 absorption main factor가 보존 된다는 의미 이다. 이러한 Polydopamine-like film으로 As, Cr, Mg, Cu 200ppm solution에 대한 filtration 능력을 확인 하였다. As, Cr, Cu, Mg 의 제거율이 각각 약25%, 35%, 45%, 65%인 것을 확인 하였다. 이 수치는 시중에 판매되는 제품들과 비교했을 때 300%~500% 향상된 수치 이다.

• 한국표면공학회지
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• 제34권2호
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• pp.161-168
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• 2001

A Thermal Barrier Coating (TBC) can play an important role in protecting parts from harmful environments at high temperatures such as oxidation, corrosion, and wear in order to improve the efficiency of aircraft engines by lowering the surface temperature of the turbine blade. The TBC can increase the life span of the product and improve the operating properties. Therefore, in this study the mechanical and thermal properties of the TBC such as oxidation, fatigue and shock at high temperatures were evaluated. A samples of a bond coat (CoNiCrAlY) produced by the High Velocity Oxygen Fuel (HVOF) and Low Pressure Plasma Spray (LPPS) method were used. The thickness of the HVOF coating layer was approximately $450\mu\textrm{m}$ to 500$\mu\textrm{m}$ and the hardness number of the coating layer was between 350Hv and 400Hv. The thickness of the LPPS coating was about 350$\mu\textrm{m}$ to 400$\mu\textrm{m}$ and the hardness number of the coating was about 370Hv to 420Hv. The X-ray diffraction analysis showed that CoNiCrAlY coating layer of the HVOF and LPPS was composed of the $\beta$and ${\gamma}$phase. After the high temperature oxidation test, the oxide scale with about l0$\mu\textrm{m}$ to 20$\mu\textrm{m}$ thickness appeared at the coating surface on the Al-depleted zone was observed under the oxide scale layer.

• 한국세라믹학회지
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• 제55권2호
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• pp.178-184
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• 2018

In the present study, $TiB_2-Co$ composite coatings were thermally sprayed onto the surface of a 304 stainless steel substrate using an atmospheric plasma spray (APS). The phase analysis of the powders and plasma-sprayed coatings was performed using X-ray diffractometry analysis. The microstructures of the coatings were studied by a scanning electron microscope (SEM). The average particle size and flowability of the feedstocks were also measured. Both $TiB_2-32Co$ and $TiB_2-45Co$ (wt.%) coatings possessed typical dense lamellar structures and high-quality adhesion to the substrate. The oxidation behaviors of the coatings were studied at $900^{\circ}C$ in an atmospheric environment. In addition, the cross-sectional images of the oxidized coatings were analyzed by SEM. A thin and well-adhered layer was formed on the surface of both $TiB_2-Co$ coatings, confirming satisfactory high-temperature oxidation resistance. The kinetic curves corresponding to the isothermal oxidation of the coatings illustrated a short transient stage from rapid to slow oxidation during the early portion of the oxidation experiment.

• 한국재료학회지
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• 제30권7호
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• pp.350-358
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• 2020

A variety of composite powders having different aluminum and carbon contents are prepared using various organic solvents having different amounts of carbon atoms in unit volume as ball milling agents for titanium and aluminum ball milling. The effects of substrate temperature and post-heat treatment on the texture and hardness of the coating are investigated by spraying with this reduced pressure plasma spray. The aluminum part of the composite powder evaporates during spraying, so that the film aluminum content is 30.9 mass%~37.4 mass% and the carbon content is 0.64 mass%~1.69 mass%. The main constituent phase of the coating formed on the water-cooled substrate is a non-planar α₂ phase, obtained by supersaturated carbon regardless of the alloy composition. When these films are heat-treated at 1123 K, the main constituent phase becomes γ phase, and fine Ti₂AlC precipitates to increase the film hardness. However, when heat treatment is performed at a higher temperature, the hardness is lowered. The main constitutional phase of the coating formed on the preheated substrate is an equilibrium gamma phase, and fine Ti₂AlC precipitates. The hardness of this coating is much higher than the hardness of the coating in the sprayed state formed on the water-cooled substrate. When hot pressing is applied to the coating, the porosity decreases but hardness also decreases because Ti₂AlC grows. The amount of Ti₂AlC in the hot-pressed film is 4.9 vol% to 15.3 vol%, depending on the carbon content of the film.

• Tribology and Lubricants
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• 제16권2호
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• pp.84-90
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• 2000

High Temperature wear behavior of plasma sprayed zirconia coatings containing up to 10 mol% of Fe$_2$O$_3$ were investigated. The wear test results showed that the addition of Fe$_2$O$_3$ particles to zirconia improved the wear resistance and lowered the coefficient of friction. Optimum concentration of Fe$_2$O$_3$ was about 5 mol%. Similar degradation behavior was observed at about 40$0^{\circ}C$ for both zirconia and Fe$_2$O$_3$ added zirconia coatings. The results indicated that stabilization of tetragonal phase and changes in mechanical properties such as hardness and toughness were responsible for tribological behavior of plasma sprayed zirconia contain Fe$_2$O$_3$.

• Journal of Welding and Joining
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• 제17권6호
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• pp.62-69
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• 1999

The advantages of Thermal sprayed coatings as a replacement for cast iron liners are reduced weight, better heat transfer and reduced cost. One of the most important performance attributes of a cylinder bore coating is its wear resistance, since it must survive the abrasive sliding of both the piston rings and the piston skirt. In this study, composite powders were prepared by ball milling of Al-13Si-3Mg(wt%) alloy with SiC particles. The concentrations of SiC were 40 and 60wt%. The composite powders were sprayed using Metco-9MB plasma torch. Plasma sprayed coatings were heat-treated at 500℃ for 3 hours. The wear resistances of the plasma sprayed coatings were found to improve with heat treatment and superior to the commercially available G.C.I.(gray cast iron). AlSiMg-40SiC heat-treated coatings showed the best wear resistance in this study.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2011년도 제37회 추계학술대회논문집
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• pp.694-696
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• 2011

전북대학교 고온플라즈마 응용연구센터 구축사업단에서는 0.4MW/2.4MW급 Huel type 플라즈마장치 및 60kW/200kW급 RF 플라즈마 장치 구축을 목표로 건축 및 장비 지원설비가 센터 부지에 설치되고 있으며 플라즈마 장치의 구축이 완료되면 분말합성, 용사코팅, 지구 재진입 환경 모사 등 일련의 과정을 모두 한자리에서 처리할 수 있을 것으로 예상된다.

• 한국표면공학회지
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• 제54권6호
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• pp.365-370
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• 2021

In this research, we proceeded with research on plasma resistance of the cleaning process of APS(Atmospheric Plasma Spray)-Y₂O₃ coated parts used for semiconductor and display plasma process equipment. CF₄, O₂, and Ar mixed gas were used for the plasma environment, and respective alconox, surfactant, and piranha solution was used for the cleaning process. After APS-Y₂O₃ was exposed to CF₄ plasma, the surface changed from Y₂O₃ to YF₃ and a large amount of carbon was deposited. For this reason, the plasma corrosion resistance was lowered and contamination particles were generated. We performed a cleaning process to remove the defect-inducing surface YF₃ layer and carbon layer. Among three cleaning solutions, the piranha cleaning process had the highest detergency and the alconox cleaning process had the lowest detergency. Such results could be confirmed through the etching amount, morphology, composition, and accumulated contamination particle analysis results. Piranha cleaning process showed the highest detergency, but due to the very large thickness reduction, the base metal was exposed and a large number of contaminated particles were generated. In contrast, the surfactant cleaning process exhibit excellent properties in terms of surface detergency, etching amount, and accumulated contamination particle analysis.

• Journal of Welding and Joining
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• 제14권6호
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• pp.109-118
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• 1996

Al$_2$O$_3$-TiO$_2$powders of six different compositions were plasma-sprayed on Ti substrate. The spray powders and the spray coated layers were analysed and compared using SEM and X-RD. The elastic properties (specific elastic constant and damping coefficient) of the coated specimens were measured in order to select the optimum composition range of ceramics for use in a speaker diaphragm. A correlation between the microstructure and elastic properties was also investigated. When $Al_2$O$_3$powders with 0- 13% TiO$_2$were plasma sprayed, the coated layers were composed of metastable y-Al$_2$O$_3$with small amount of $\alpha$-Al$_2$O$_3$and the content of $\alpha$-Al$_2$O$_3$was increased with TiO$_2$content. Specific elastic constant was rapidly increased with 2 and 13% TiO$_2$addition to $Al_2$O$_3$. The internal damping was nearly unchanged with TiO$_2$content The specific elastic constant seemed to be dependent on the content of $\alpha$-Al$_2$O$_3$in the coated layer.