• Corrosion Science and Technology
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• 제14권5호
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• pp.226-231
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• 2015

In spite of highly advanced paint coating techniques, corrosion damage of marine metal and alloys increase more and more due to inherent micro-cracks and porosities in coatings formed during the coating process. Furthermore, flowing seawater conditions promote the breakdown of the protective oxide of the materials introducing more oxygen into marine environments, leading to the acceleration of corrosion. Various corrosion protection methods are available to prevent steel from marine corrosion. Cathodic protection is one of the useful corrosion protection methods by which the potential of the corroded metal is intentionally lowered to an immune state having the advantage of providing additional protection barriers to steel exposed to aqueous corrosion or soil corrosion, in addition to the coating. In the present investigation, the effect of flow velocity was examined for the determination of the optimum corrosion protection current density in cathodic protection as well as the corrosion rate of the steel. It is demonstrated from the result that the material corrosion under dynamic flowing conditions seems more prone to corrosion than under static conditions.

• Bulletin of the Korean Chemical Society
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• 제31권2호
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• pp.355-359
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• 2010

A $Li[Co_{1/3}Ni_{1/3}Mn_{1/3}]O_2$ cathode was modified by applying a $ZrF_x$ coating. The surface-modified cathodes were characterized by XRD, SEM, EDS, TEM techniques. XRD patterns of $ZrF_x$-coated $Li[Co_{1/3}Ni_{1/3}Mn_{1/3}]O_2$ revealed that the coating did not affect the crystal structure of the parent powder. SEM and TEM images showed that $ZrF_x$ nano-particles were formed as a coating layer, and EDS data confirmed that $ZrF_x$ distributed uniformly on the surface the powder. Capacity retention of coated samples at high C rates was superior to that of pristine sample. However, as the coating concentration increases beyond the optimum concentration, the rate capability was deteriorated. Whereas, as the increase of coating concentration to 2.0 wt %, the cyclic performances of the electrodes under the severe conditions (high cut-off voltage, 4.8 V, and high measurement temperature, $55^{\circ}C$) were improved considerably.

• 한국세라믹학회지
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• 제31권8호
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• pp.911-919
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• 1994

As the study for preparation of single-layer anti-reflective coating on glass, the conditions of synthesis of sol for coating and of reproducible coating procedure were investigated. In case of water-based sol, coating was impossible because of poor wettability of sol. The Substitution of solvent with ethanol improved the wettability of sol on the glass surface, and optimum amount of ethanol for substitution was 70 vol%. Maximum specific surface area and total pore volume of water-based sol were 268.7$m^2$/g and 0.315 cc/g, but after substitution, those values increased to 404.1 $m^2$/g and 0.376 cc/g, respectively. The upper limit withdrawl speed of coating in order to get clean coated films without aggregations or stains was 7 cm/min. In case of addition of 0.1 mol HNO3 and substitution with 70 vol% ethanol and heat-treatment at 40$0^{\circ}C$ for 1 hour, thin film with thickness of 94 nm was obtained at withdrawl speed of 4 cm/min. The thickness of thin film was independent of drying time.

• Design & Manufacturing
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• 제13권3호
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• pp.1-11
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• 2019

Recently, studies on the development of flexible electronic devices by combining flexible materials and a conductor have been actively performed as interest in wearable devices. Especially, carbon nanotubes (CNT) or graphene coating have been used to construct a circuit to induce improvement in flexibility and rigidity. Various technologies have been developed in the surface coating of conductive materials, which are key to the manufacture of flexible electronic devices. Surface coating products with 3D coating and micro-patterns have been proposed through electrospinning, electrification, and 3D printing technologies. As a result of this advanced surface coating technology, there is a growing interest in manufacturing gradient conductive surfaces. Gradient surfaces have the advantage that they are adapted to apply a gentle change or to inspect optimum conditions in a particular region by imparting continuously changing properties. In this study, we propose a manufacturing technique to produce a continuous gradient conductive surface by combining a partial stretching of elastomer and a conductive material coating, and introduce experimental results to confirm its performance.

• 대한금속재료학회지
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• 제47권10호
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• pp.652-659
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• 2009

Many ancient and historical artifacts were made by copper and its alloys. In the case of outdoor exposure artifacts, the surface could be suffered from corrosion and tarnish by the reaction with its environment. In order to preserve the artifacts, surface treatment would be needed and BTA coating has been usually applied to tin-bronze. This paper dealt with the evaluation of the properties of BTA coated film using a linear polarization method and AC impedance measurement. On the base of corrosion rate and film resistance for the specimen formed by coating process, optimum coating conditions are as follows; 3 cycles brushing or 3 cycles spraying coatings for natural dried process and 1 cycle brushing coating or 5 cycles spraying coating for hot-air dried process.

• 대한기계학회논문집A
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• 제39권9호
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• pp.937-945
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• 2015

본 연구에서는 코팅 공정에 사용되는 슬롯다이(slot-die)에 대해 조건에 따른 코팅 성능을 연구하였다. 슬롯다이 코팅은 코팅 되는 필름의 속도, 코팅액의 점도 그리고 슬롯다이로 주입 되는 압력에 따라 코팅 품질이 많이 달라진다. 따라서 본 논문에서는 CFD 코드를 이용하여 안정적인 코팅을 위한 최적의 조건을 찾았다. 다양한 코팅액의 점도와 슬롯다이 입구의 압력 그리고 코팅 필름의 속도에 대해서 해석을 수행하였다. 그 결과로 $5kgf/cm^2$의 압력과 100cps 의 점도 그리고 20m/min 의 속도 조합에서 가장 안정적으로 코팅액이 잘 도포되었다.

• 한국식품과학회지
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• 제38권6호
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• pp.762-766
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• 2006

골판지 상자의 수분저항성을 증진시키기 위해 골판지 상자 제조에 사용되는 라이너지의 표면을 알긴산으로 표면코팅을 하기 위한 최적 조건을 결정하기 위하여 농도, 가소제의 종류와 사용량, 알긴산의 불용화를 위한 다가 금속이온의 종류와 최적농도 및 침지시간 등을 결정하였다. 라이너지의 표면코팅을 위한 알긴산의 농도는 2.5%(w/w)가 적합하였으며, 가소제인 글리세롤은 알긴산 대비 35%의 농도로 사용하는 것이 적합하였고, 알긴산 필름의 불용화를 위해서는 2% $CaCl_2$ 용약을 사용하여 3분간 처리하는 것이 라이너지의 수분에 대한 저항성 증진에 최적조건을 결정되었다. 다가 금속이온으로 $CA^{2+}＄ 이외에 $Cu^{2+}＄를 사용했을 때 낮은 투습계수와 수분용해도를 나타냈다. 가소재의 종류에 따라서는 수분 흡습에 대한 저항성이 큰 솔비톨을 첨가 했을 때 라이너지의 수분저항성이 유의적인 차이를 보이며 증가하였다.

• Journal of Advanced Marine Engineering and Technology
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• 제30권1호
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• pp.157-168
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• 2006

Recently, interest in using Al alloys in ship construction instead of fiber-reinforced plastic (FRP) has increased because of the advantages of A) alloy ships over FRP ships, including high speed, increased load capacity. and ease of recycling. This paper investigated the mechanical and electrochemical properties of Al alloys in a slow strain rate test under various potential conditions. These results will provide reference data for ship design by determining the optimum protection potential regarding hydrogen embrittlement and stress corrosion cracking. In general, Al and Al alloys do not corrode on formation of a film that has resistance to corrosion in neutral solutions. In seawater, however, $Cl^-$ ions lead to the formation and destruction of a Passive film. In a potentiostatic experiment. the current density after 1200 sec in the Potential range of $-0.68\~-1.5\;V$ was low. This low current density indicates the protection potential range. Elongation at an applied potential of 0 V was high in this SSRT. However, corrosion protection under these conditions is impossible because the mechanical properties are worse owing to decreased strength resulting from the active dissolution reaction in parallel parts of the specimen. A film composed of $CaCO_3\;and\;Mg(OH)_2$ confers corrosion resistance. However, at potentials below -1.6 V forms non-uniform electrodeposition coating, since there is too little time to form a coating. Therefore, we concluded that the mechanical properties are poor because the effect of hydrogen gas generation exceeds that of electrodeposition. Comparison of the maximum tensile strength, elongation, and time to fracture indicated that the optimum protection potential range was from -1.45 to -0.9 V (SSCE).

• Environmental Engineering Research
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• 제13권4호
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• pp.197-202
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• 2008

This study evaluated the photocatalytic oxidation of BPA using the RPOD reactor under various conditions. This study found that the RPOD was effective for BPA degradation. It could reduce 1 mg/L of BPA by half within 5 min under the optimum conditions. According to the study results, $TiO_2$ coating was important for the BPA oxidation. As the coating thickness increased, the removal efficiency improved. The light source, the light intensity and the drum rotating speed were important for the oxidation. The UV light was more effective for the BPA degradation than the visible light. The removal efficiency improved with increasing intensity. As the drum speed increased, the removal efficiency improved. The maximum speed was 240 rpm in this study. Addition of air and nitrogen was not beneficial for the BPA degradation in this study probably due to enough oxygen in the water.

• 한국정밀공학회지
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• 제27권1호
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• pp.84-90
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• 2010

The cold forging Process applies surface lubricant coating in order to smooth the friction during the cold forging process. Currently, most of the lubrication processes apply the zinc phosphate coating, which requires 11 steps and disposes sludge. But the water based lubrication process, which has been newly developed, takes 3 steps only and does not cause sludge. In this study, we present the optimal condition of water based lubrication for the cold forging of axle shaft by an experimental design method. Experimental results with minitab shall be able to predict the optimum water based lubricating conditions for the cold forging processes.