• 한국재료학회지
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• 제25권9호
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• pp.442-449
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• 2015

The effects of coating parameters were investigated in wear resistance coatings of Diamalloy-406 on Inconel 718 to obtain an optimum coating condition by high velocity oxy-fuel spraying. The coating parameters, the flow rates of source gases (hydrogen and oxygen), the powder feed rate, and the spray distance, were designed by the Taguchi method. The optimal conditions were determined: oxygen flow rate 34 FRM, hydrogen flow rate 57 FRM, powder feed rate 35 g/min, and spray distance 7 inch. Friction coefficients of the coating and the substrate decreased with an increasing sliding surface temperature from $25^{\circ}C$ to $450^{\circ}C$. The friction coefficient of Diamalloy-4006 coating decreased as the sliding surface temperature increased from $0.43{\pm}0.01$ at $25^{\circ}C$ to $0.29{\pm}0.01$ at $450^{\circ}C$. The wear trace and wear depth of the coating were smaller than the substrate at all temperatures tested. The relationship between spray parameters and wear resistance was discussed extensively, based on the measured roughness, hardness, and porosity in each coating.

• 한국분말재료학회지
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• 제25권5호
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• pp.408-414
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• 2018

This study investigates the microstructure and wear properties of cermet (ceramic + metal) coating materials manufactured using high velocity oxygen fuel (HVOF) process. Three types of HVOF coating layers are formed by depositing WC-12Co, WC-20Cr-7Ni, and Cr3C2-20NiCr (wt.%) powders on S45C steel substrate. The porosities of the coating layers are $1{\pm}0.5%$ for all three specimens. Microstructural analysis confirms the formation of second carbide phases of $W_2C$, $Co_6W_6C$, and $Cr_7C_3$ owing to decarburizing of WC phases on WC-based coating layers. In the case of WC-12Co coating, which has a high ratio of $W_2C$ phase with high brittleness, the interface property between the carbide and the metal binder slightly decreases. In the $Cr_3C_2-20CrNi$ coating layer, decarburizing almost does not occur, but fine cavities exist between the splats. The wear loss occurs in the descending order of $Cr_3C_2-20NiCr$, WC-12Co, and WC-20Cr-7Ni, where WC-20Cr-7Ni achieves the highest wear resistance property. It can be inferred that the ratio of the carbide and the binding properties between carbide-binder and binder-binder in a cermet coating material manufactured with HVOF as the primary factors determine the wear properties of the cermet coating material.

• 한국마린엔지니어링학회:학술대회논문집
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• 한국마린엔지니어링학회 2006년도 전기학술대회논문집
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• pp.271-272
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• 2006

Zinc confers high corrosion resistance by acting as a sacrificial anode, and a zinc coating improves the appearance of steel. Chromate conversion coating (CCC) films are still one of the most efficient surface treatments for steel. Although such films can self-repair via the dissolution of Cr(VI), dissolved Cr(VI) have adverse effects on humans, and the environment. Therefore, we examined the corrosion protection property and morphology of colloidal silica conversion films as an alternative to CCC films. The corrosion behavior was investigated in 3% NaCl solution using electrochemical techniques, including electrochemical impedance spectroscopy, open circuit potential, and the salt spray test(SST). Corrosion was implied by the appearance of red rust on the specimen surface. In corrosion resistance at 3% NaCl solution, red rust appeared at 15-20, 55-70, and 83-98 days on Zn-electroplated steel, colloidal silica conversion-coated specimens, and CCC-coated specimens, respectively. In the salt spray test, the colloidal silica film provided better corrosion protection than CCC films, i.e., red rust appeared at 96 hours on the Zn-electroplated steel sheet, at 432 hours with the CCC films, and at 888 hours with silica conversion coating.

• 폴리머
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• 제35권2호
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• pp.141-145
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• 2011

In-mold decoration 포일의 경질 코팅 층에 사용하는 수지를 대상으로 전자빔(electron beam, EB) 경화에 관한 연구를 수행하였다. 시료에 다른 양의 EB를 조사하고 경화 반응 정도를 Fourier transform infrared(FTIR) spectroscopy를 사용하여 관찰하였다. EB 조사선량 증가에 따른 코팅 물성의 변화를 표면 경도와 내마모성을 중심으로 알아보았다. 또한 나노 입자 첨가가 코팅 물성에 미치는 영향을 조사하였다. 본 연구로부터 얻은 실험적 결과는 자외선(ultraviolet, UV) 경화 시스템과 유사한 EB 경화 시스템의 상업적 개발에 이용될 수 있을 것으로 기대된다.

• 한국태양에너지학회 논문집
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• 제33권4호
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• pp.31-38
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• 2013

The chemical composition of the black Cr solar selective coatings electrodeposited were investigated for property analysis by using a XPS(X-ray photoelectron spectroscopy) before and after annealing in air at $300^{\circ}C{\sim}500^{\circ}C$ for 120 hours. Black Cr selective coating exposed by solar radiation for 5 months was compared with annealed sample. In addition, The Cu solar selective coatings were prepared by thermal oxidation method for low temperature application. The samples obtained were characterized by using the optical reflectance measurements by using a spectrometer. Optical properties of oxidized Cu solar coatings were solar absorptance $({\alpha}){\simeq}0.62$ and thermal emittance $({\epsilon}){\simeq}0.41(100^{\circ}C)$. In the as-prepared Cr black selective coating, the surface of the coating was found to have Cr hydroxide and Cr. The Cr hydroxide of the major component was converted to $Cr_2O_3$ or $CrO_3$ form after annealing at $500^{\circ}C$ with the desorption of water molecules. The black Cr selective coating was degraded significantly at temperature of $500^{\circ}C$. The main optical degradation modes of this coating were diffusion of Cu substrate materials.

• 한국전기전자재료학회논문지
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• 제27권11호
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• pp.736-739
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• 2014

In this paper, we propose a enhanced anti-corrosion property of the ground system by coating the CNT/PVDF composite film on it. Polymer material used for preventing the corrosion of ground system is polyvinylidene fluoride (PVDF), and conducting filler for obtaining conductivity of the composite film is multi-walled carbon nanotubes (MWCNTs). The MWCNTs were dispersed in the organic solvent of methyl ethyl ketone 2-butanone (MEK) with different concentration ratios, and the PVDF was solved in the MEK solvent with constant concentration ratio of 1 wt%. The CNT/PVDF composite solution was perpared by mixing and re-dispersing the CNT solution and the PVDF solution. Finally, the CNT/PVDF composite films were fabricated by the spray coating method using the above composite solution. Electrical conductivity, surface states, and anti-corrosion property of the CNT/PVDF composite films coated on the Cu substrate were evaluated. We found that the CNT/PVDF composite film showed relatively low resistance, hydrophobic surface state, and chemical stability. Consequently, we could improve the anti-corrosion property and maintain the electrical conductivity of the ground system by coating the CNT/PVDF composite film on it.

• 한국응용과학기술학회지
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• 제29권1호
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• pp.141-148
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• 2012

본 연구에서는 초소수성 실리카 에어로겔을 이용하여 단열 성능을 갖는 투명 필름용 유/무기 복합 코팅물질을 제조하였다. 바인더 물질로 사용된 자외선 경화형 우레탄 아크릴레이트 수지와 에어로겔과의 상용성을 위해 계면활성제(Brij 56)를 이용하여 에어로겔의 표면을 개질하였다. 개질된 에어로겔을 고분자 수지와 복합화한 코팅 용액을 폴리카보네이트 기지재에 코팅한 후 자외선경화를 통해 코팅필름을 제조하였다. 에어로겔이 10 vol% 함량으로 첨가되었을 때, 코팅필름의 단열성능은 측정된 열전도도 기준으로 순수 기지재 대비 28% 정도로 향상되었다. 또한, 코팅필름의 광투과율은 에어로겔이 50 vol%로 과량 첨가된 경우에도 80% 이상 높은 수준을 유지하였으며, 우수한 접착성(5B) 및 연필 경도(4H)를 보여주었다.

• Computers and Concrete
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• 제10권1호
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• pp.35-47
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• 2012

The ideal gradating curve is used in this study to estimate densified aggregate blended ratio and total surface area of aggregate, there by under assigned paste amount of concrete, and coating paste thickness can then be deduced. Four groups of concrete mixtures were prepared and the corresponding concrete properties, such as workability, compression strength, ultrasonic velocity, surface resistivity and chloride ion penetration, were measured and finally the results are interpreted in terms of "coating thickness". The result shows as the coating thickness of the concrete is higher than critical one, the coating thickness on aggregate does affect the workability, and whatever workability is required the superplasticizer can be adjusted to achieve the demand workability. Under a fixed paste quality at the same age, coating paste thickness is inversely proportional to the concrete properties, especially as the coating thickness gets thinner.

• 한국응용과학기술학회지
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• 제33권3호
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• pp.483-491
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• 2016

나노실리카가 코팅된 유리 표면은 나노실리카 표면에 존재하는 친수성 수산기로 인해 방담성이 매우 증가하나, 실외에 설치된 유리에 코팅된 경우는 비에 의해 씻겨 나가 방담 특성의 내구성이 급격히 감소한다. 또한 나노실리카가 코팅된 유리 표면의 토폴로지는 광투과율 또는 반사방지 특성을 좌우하는 매우 중요한 인자이다. 이러한 나노실리카 코팅의 특성에 관한 내구성을 향상시키기 위하여 가교제로 테트라에틸오르소실리케이트 (TEOS)를 사용하여 나노실리카 (Ludox) 현탁액으로 친수성 나노실리카피막을 제조하였다. 산성 또는 염기성 수용액 중에서의 TEOS의 가수 분해 최적 조건도 물에 대한 접촉각 측정을 통하여 조사하였다. pH=4의 산성 조건에서 1.5 wt% 나노실리카-TEOS 코팅액으로 얻은 최종 투명한 친수성 코팅층은 매우 향상된 친수성에 대한 내구성뿐만 아니라, 코팅하지 않은 유리에 비해 약 2 % 포인트 정도 높은 가시광투과율을 나타내었다.

• 해양환경안전학회지
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• 제12권1호
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• pp.9-14
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• 2006

유기도막의 방식성능은 도막의 수지성분과 안료의 화학적 특성에 의존한다 전자는 부식인자의 침투를 차단 및 지연시키는 역할을 하며, 후자는 침투된 부식인자들에 의해 일어나는 부식반응을 억제하는 기능을 갖고 있다. 또한 도막 자체의 영향 외에, 외부 환경에 의해서 다르게 나타난다. 본 연구에서는 교류 임피던스 법을 이용하여 유속과 그에 따른 유동 전단응력에 의한 도막의 열화거동을 조사하였다. 실험기 사용된 도막의 두께는 $70{\mu}m$에서 $140{\mu}m$까지 변화시켰다. 두꺼운 도막($140{\mu}m$) 에서는 유속이 증가함에 따라 물 흡수량의 감소와 높은 임피던스 특성을 나타내었다. 그러나 얇은 도막($90{\mu}m$) 에서는 유속이 증가함에 따라 도막의 파괴가 진행되고 있음을 확인할 수 있었다. 도막에 가해지는 전단응력이 증가할수록, 즉 선박의 운항속도가 증대될수록 도막의 열화에 의하여 방식성능이 떨어짐을 확인할 수 있었다.