• Corrosion Science and Technology
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• 제21권2호
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• pp.111-120
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• 2022

To solve the corrosion problem of industrial equipment and other constructions containing metals, corrosion protection can be performed by using coating which provides a barrier between the metal and its environment. Coatings play a significant role in protecting irons and steels in harsh marine and acid environments. This study was conducted to identify an anti-corrosive epoxy coating for carbon steel composite with 0.1, 0.3, and 0.5 wt% concentrations of nanoparticles of SiO₂ using the dip-coating method. The electrochemical behavior was analyzed with open circuit potential (OCP) technics and polarization curves (Tafle) in 3.5 wt% NaCl and 5 vol% H₂SO₄ media. The structure, composition, and morphology were characterized using different analytical techniques such as X-ray Diffraction (XRD), Fourier Transform Infrared spectrum (FT-IR), and Scanning Electron Microscopy (SEM). Results revealed that epoxynano SiO₂ coating demonstrated a lower corrosion rate of 2.51 × 10^-4 mm/year and the efficiency of corrosion protection was as high as 99.77%. The electrochemical measurement showed that the nano-SiO₂ / epoxy coating enhanced the anti-corrosive performance in both NaCl and H₂SO₄ media.

• 한국결정성장학회지
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• 제16권6호
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• pp.273-277
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• 2006

High velocity of oxy-fuel (HVOF) thermal spray coating is progressively replacing the other classical hard coatings such as chrome plating and ceramic coating by the classical methods, since the very toxic $Cr^{6+}$ ion is well known as carcinogen causing lung cancer, and the ceramic coatings are brittle. Co-alloy T800 powder is coated on the Inconel 718 substrates by the HVOF coating procesess developed by this laboratory. For the study of the possibility of replacing of chrome plating, the wear properties of HVOF Co-alloy T800 coatings are investigated using the reciprocating sliding tester with a counter sliding SUS 304 ball both at room and at an elevated temperature of $1000^{\circ}F\;(538^{\circ}C)$. The possibility as durability improvement coating is studied for the application to the high speed spindles vulnerable to frictional heat and wear. Wear mechanisms at the reciprocating sliding wear test are studied far the application to the systems similar to the sliding test such as high speed spindles. Wear debris and frictional coefficients of T800 coatings both at room and at an elevated temperature of $538^{\circ}C$ are drastically reduced compared to those of non-coated surface of Inconel 718 substrates. Wear traces and friction coefficients of both coated and non-coated surfaces are drastically reduced at a high temperature of $538^{\circ}C$ compared with those at room temperature. These show that the coating is highly recommendable far the durability Improvement coating on the surfaces vulnerable to frictional heat and wear.

• 한국재료학회지
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• 제20권8호
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• pp.418-422
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• 2010

As a starting material, BCP (biphasic calcium phosphate) nano powder was synthesized by a hydrothermal microwave-assisted process. A highly porous BCP scaffold was fabricated by the sponge replica method using 60 ppi (pore per inch) of polyurethane sponge. The BCP scaffold had interconnected pores ranging from $100\;{\mu}m$ to $1000\;{\mu}m$, which were similar to natural cancellous bone. To realize the antibacterial property, a microwave-assisted nano Ag spot coating process was used. The morphology and distribution of nano Ag particles were different depending on the coating conditions, such as concentration of the $AgNO_3$ solution, microwave irradiation times, etc. With an increased microwave irradiation time, the amount of coated nano Ag particles increased. The surface of the BCP scaffold was totally covered with nano Ag particles homogeneously at 20 seconds of microwave irradiation time when 0.6 g of $AgNO_3$ was used. With an increased amount of $AgNO_3$ and irradiation time, the size of the coated particles increased. Antibacterial activities of the solution extracted from the Ag-coated BCP scaffold were examined against gram-negative (Escherichia coli) and gram-positive bacteria (Staphylococcus aureus). When 0.6 g of $AgNO_3$ was used for coating the Ag-coated scaffold, it showed higher antibacterial activities than that of the Ag-coated scaffold using 0.8 g of $AgNO_3$.

• 전기화학회지
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• 제13권4호
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• pp.246-250
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• 2010

In this study, nano-crystallized $Al_2O_3$ was coated on the surface of $LiFePO_4$ powders via a novel dry coating method. The influence of coated $LiFePO_4$ upon electrochemical behavior was discussed. Surface morphology characterization was achieved by transmission electron microscopy (TEM), clearly showing nano-crystallized $Al_2O_3$ on $LiFePO_4$ surfaces. Furthermore, it revealed that the $Al_2O_3$-coated $LiFePO_4$ cathode exhibited a distinct surface morphology. It was also found that the $Al_2O_3$ coating reduces capacity fading especially at high charge/discharge rates. Results from the cyclic voltammogram measurements (2.5-4.2 V) showed a significant decrease in both interfacial resistance and cathode polarization. This behavior implies that $Al_2O_3$ can prevent structural change of $LiFePO_4$ or reaction with the electrolyte on cycling. In addition, the $Al_2O_3$ coated $LiFePO_4$ compound showed highly improved area-specific impedance (ASI), an important measure of battery performance. From the correlation between these characteristics of bare and coated $LiFePO_4$, the role of $Al_2O_3$ coating played on the electrochemical performance of $LiFePO_4$ was probed.

• 한국표면공학회지
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• 제41권4호
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• pp.163-168
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• 2008

The dental orthodontic bracket requires good mechanical properties, such as elastic strength and frictional resistance, combined with a high resistance to corrosion. The objective of this study was to investigate the effects of TiN and ZrN coating on corrosion resistance of orthodontic brackets using various electrochemical methods. Brackets manufactured by Ormco Co. were used, respectively, for experiment. Ion plating was carried out for coatings of bracket using Ti and Zr coating materials with nitrogen gas. Ion plated surface of each specimen was observed with field emission scanning electron microscopy(FE-SEM), energy dispersive Xray spectroscopy(EDS) and electrochemical tester. The corrosion potential of the TiN and ZrN coated bracket was comparatively high. The current density of TiN and ZrN coated bracket was smaller than that of non-coated bracket in 0.9% NaCl solution. Pit nucleated at angle of bracket slot.

• Corrosion Science and Technology
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• 제19권2호
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• pp.57-65
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• 2020

As competition among global automakers intensifies, demand for materials that are better in price and performance is increasing. While steel and plastic materials compete for automotive fuel tanks, plastic materials have advantages such as light weight for automobiles. However, they have high prices. Accordingly, in this paper, four types of Zn-X plated steel sheets, electroplating (X = none, Sn) and galvannealed (X = Fe, Fe-Mg), were manufactured and their applicability as a fuel tank material was evaluated. Nano-composite coating solution with good conductivity was treated on the surface of plated steels using a roll coater and then cured through induction furnace to improve corrosion resistance. Quality characteristics such as corrosion resistance, fuel resistance to diverse gasoline and diesel fuels, and seam weldability were evaluated for the above plated steels. Their properties were compared and analyzed with conventional Zn-Ni electroplating steels. Among the above plated steels, Zn-Fe-Mg galvannealed steels coated with nano-composite coating exhibited better properties than other steels. Detailed experimental results suggest that evenly distributed Mg elements on the coating layer play a key role in the enhanced quality performance.

• 한국표면공학회지
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• 제40권2호
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• pp.70-76
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• 2007

Ni-P-SiC composite coating layers were prepared by electroless plating method and their deposition rate, codeposition of SiC, morphology, surface roughness, hardness, wear and friction properties were investigated. The deposition rate was kept almost constant independent of the concentration of SiC in the plating solution and the codeposition of SiC in the composite coating layer increased with increased concentration of SiC in the plating solution except the early stage. Vickers microhardness increased with respect to the increased codeposition of SiC and the heat treatment at $300^{\circ}C$ in air for 1 hour. It was found that the wear volume decreased with increased up to 50 wt.% of SiC codeposition, and that friction coefficient increased gradually with increased codeposition of SiC. Considering the wear and the friction behaviors, the composite coating layer obtained by using 50 wt.% of SiC codeposition is desirable for the practical application for anti-wear and anti-friction coatings.

• 한국결정성장학회지
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• 제29권6호
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• pp.352-358
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• 2019

최근 인쇄용지는 단순히 정보 전달의 기능을 넘어서 미적, 예술적 가치가 부가면서 고품질의 인쇄가 가능한 도공지(coated paper)에 대한 시장의 수요가 증가하고 있다. 특히 실사급 고품질의 인쇄가 가능한 잉크젯 프린팅의 도공지는 잉크의 인쇄적성을 향상시키기 위하여 표면에 젖음성(wettability)과 다공성 구조(porous structure)를 갖는 도공층의 역할이 매우 중요하다. 본 연구에서는 나노 실리카 졸 입자에 실란 커플링제로 표면처리하고 수용성 결합제인 폴리비닐알콜(PVA)와 혼합하여 도공액(coating color)를 제조하고 원지(base paper)에 코팅하여 도공층을 제조하였다. 실란 커플링제로 표면처리한 나노 실리카 도공층은 표면처리하지 않은 도공층과 비교하여 균일한 기공 분포 및 평탄한 표면 거칠기를 가지며, 판매용 고급 인화지와 유사한 광택도를 갖는 것을 확인하였다. 특히 잉크의 망점(dot)에 대한 진원도로 평가하는 인쇄적성 평가 결과 실란 커플링제로 표면처리한 도공지는 다층 구조의 도공층을 갖는 판매용 고급 인화지보다 더 우수한 결과를 얻을 수 있었다. 이러한 결과는 실란 커플링제 표면처리를 통하여 나노 실리카 입자의 분산성이 향상되어 우수한 젖음성과 균일한 기공 분포를 갖는 도공층 형성이 가능하였기 때문으로 확인되었다.

• 한국표면공학회지
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• 제40권1호
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• pp.32-38
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• 2007

Ni coating layers were formed using a newly developed electroless Ni plating solution. The properties of Ni coating layer such as internal stress, hardness, surface roughness, crystallinity, solderability and surface morphology were investigated using various tools. Results revealed that internal stress decreased with plating time and reached $40N/mm^2$ at 20 minutes of the plating time. Hardness increased with increasing P content and thickness. Surface roughness of the pad decreased with Ni and Ni/Au plating. Crystallinity decreased with increasing P content. Solderability based on wettability decreased with Ni and Ni/Au plating. Based on surface morphology, it is expected that Ni coating layer formed using a newly developed electroless Ni plating solution is lower than that formed using a commercial electroless Ni plating solution in possibility of black pad occurrence.

• Transactions on Electrical and Electronic Materials
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• 제17권3호
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• pp.178-181
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• 2016

In this study a coating experiment was performed to fabricate blue light cut films, which represent a 390~430 nm cut off rate of more than 40% and a transmittance rate of more than 90%, using a roll-to-roll nano micro coating system. The study also analyzed the characteristics of the blue light cut films. Thus, the hardness, which is more than 3H, is ensured through fabricating films using a Sol-Gel process that will determine the proper hardness level. Also, the experiment shows excellent results by cutting blue light through a mixing blue light powder.