• Corrosion Science and Technology
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• 제16권3호
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• pp.141-150
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• 2017

Impregnating with quality silicone water repellent on the concrete surface is an effective method of protecting concrete. Quality silicone water repellent has been widely used in the engineering profession because of its desirable properties such as hydrophobicity, keeping concrete breathable and preserving the original appearance of the concrete. The companies in China that produce silicone water repellent are listed. Test methods in the specifications or standards about silicone water repellent in China are summed. The test methods relative to durability of concrete impregnated with silicone water repellent (such as resistant to chloride ion penetration, resistant to alkali, resistance to freezing and thawing and weatherability etc.) and the constructive quality (such as water absorption rate, impregnating depth and the dry velocity coefficient etc.) are compared and analyzed. The results indicate that there are differences among test methods relative to different specifications with the same index and therefore, confusion has ensued when selecting test methods. All test methods with the exception of the method of water absorption rate by using a Karsten flask are not non-destructive methods or conducted in a laboratory. Finally, further research on silicone water repellent during application is proposed.

• Journal of Electrochemical Science and Technology
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• 제7권4호
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• pp.251-262
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• 2016

The corrosion protection of mild steel in 1M HCl and 0.5M $H_2SO_4$ solutions by ethanol extract of Vernonia amygdalina (VA) was studied using a combination of experimental and computational methods. The obtained results revealed that VA reduced the corrosion of mild steel in both environments and inhibition efficiency increased with VA concentration but decreased with prolonged exposure. Electrochemical results showed that the extract functioned via mixed corrosion inhibiting mechanism by adsorption of some organic constituents of the extract on the metal/acid interface. Findings from infrared spectroscopy and electron microscopy all confirmed that VA retarded mild steel corrosion in both 1M HCl and 0.5M $H_2SO_4$ through an adsorption process. The adsorption behavior of selected constituents of the extract was modeled using density functional theory computations.

• 한국표면공학회:학술대회논문집
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• 한국표면공학회 2015년도 춘계학술대회 논문집
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• pp.77-77
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• 2015

Metallic glass alloys having dense packing structure have short range ordered structure with long range homogeneity. Therefore, they can provide complete corrosion protection and unique electrical properties. Recently, metallic glass thin films have received much attention to extend its application fields combining with PVC coating technologies. The metallic glass thin films can change the surface properties of the conventional bulk materials which need anticorrosion properties. However, multi-component alloying targets are required to fabricate the metallic glass thin films because metallic glass alloys contain more than three elements. Recently, many researchers have been reported the properties of the metallic glass thin films synthesized with multi-cathode systems or amorphous target. But, it is difficult to fabricate the large sized sputtering targets for mass production equipment with high toughness and thermal stability. In this study, newly developed sputtering target with glass forming ability and the properties of the metallic glass thin films will be introduced with respect to the various application fields such as bipolar plate in PEM fuel cell and decorative coatings for electric device and construction fields.

• Journal of Electrochemical Science and Technology
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• 제10권2호
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• pp.231-243
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• 2019

The methanolic extracts of the leaves and stem of the plant Lepidagathis keralensis were evaluated for anticorrosion behavior against mild steel in 1M HCl. Corrosion inhibition studies were done by gravimetric method, electrochemical impedance spectroscopy and potentiodynamic polarization methods. Surface morphology of mild steel in the presence and absence of inhibitors were studied using SEM analysis. UV-Vis studies were also done to evaluate the mechanism of inhibition. Both the extracts showed good inhibition efficiency which increased with increase in concentration of the inhibitor and decreased with increase in temperature. The mechanism of inhibition was explained by adsorption which obeyed Langmuir adsorption isotherm. Thermodynamic calculations revealed a combination of both physisorption and chemisorption of the inhibitor on the surface of mild steel. The extracts behaved as mixed type inhibitors as determined by polarization studies. Quantum chemical studies on Phenoxyethene, one of the major components in the leaf extract of the plant was also carried out to support the experimental results.

• Corrosion Science and Technology
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• 제6권4호
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• pp.206-210
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• 2007

Aerospace aluminum alloys such as Al alloy 2024-T3 and 7075-T6 are subject to localized corrosion due the existence of intermetallics containing Cu, Mg or Zn. Chromate is currently widely used in the aerospace industry as the corrosion inhibitor for these alloys. However, chromate needs to be replaced due to its strong carcinogenicity. In this study, an extensive pigment screening has been performed to find replacements for chromates. Different categories of inhibitors were evaluated by immersion tests, DC polarization tests and other methods. Phosphates, zinc salts, cerium salts, vanadates and benzotriazole were found to be effective inhibitors for AA7075. Among those inhibitors, zinc phosphate was found to be the most effective in our novel, silane-based, one-step aqueous primer system. The performance of this primer is comparable to that of currently used chromate primers in accelerated corrosion tests, while it is completely chromate-free and its VOC is about 80% less than that of current primers. Studies by SEM/EDS showed that the unique structure of the superprimer accounts for the strong anti-corrosion performance of the zinc phosphate pigment. The self-assembled stratified double-layer structure of the superprimer is characterized by a less-penetrable hydrophobic layer at the top and a hydrophilic layer accommodating the inhibitors underneath. The top layer functions as the physical barrier against water ingress, while the lower layer functions as a reservoirfor the inhibitor, which is leached out only if the coating is damaged by a scratch or scribe. The presence of a silane in the primer further improves the adhesion and anti-corrosion performance of the primer.

• Smart Structures and Systems
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• 제11권5호
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• pp.555-567
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• 2013

An Remote Corrosion Monitoring (RCM) system consists of an anode with low potential, the metallic structures against corrosion, an electrode to provide reference potential, and a data-acquisition system to ensure the potential difference for anticorrosion. In more detail, the data-acquisition (DAQ) system monitors the potential difference between the metallic structures and a reference electrode to identify the correct potential level against the corrosion of the infrastructures. Then, the measured data are transmitted to a central office to remotely keep track of the status of the corrosion monitoring (CM) system. To date, the RCM system is designed to achieve low power consumption, so that it can be simply powered by batteries. However, due to memory effect and the limited number of recharge cycles, it can entail the maintenance fee or sometimes cause failure to protect the metallic structures. To address this issue, the low-overhead energy harvesting circuitry for the RCM systems has designed to replenish energy storage elements (ESEs) along with redeeming the leakage of supercapacitors. Our developed energy harvester can scavenge the ambient energy from the corrosion monitoring environments and store it as useful electrical energy for powering local data-acquisition systems. In particular, this paper considers the energy harvesting from potential difference due to galvanic corrosion between a metallic infrastructure and a permanent copper/copper sulfate reference electrode. In addition, supercapacitors are adopted as an ESE to compensate for or overcome the limitations of batteries. Experimental results show that our proposed harvesting schemes significantly reduce the overhead of the charging circuitry, which enable fully charging up to a 350-F supercapacitor under the low corrosion power of 3 mW (i.e., 1 V/3 mA).

• 한국재료학회지
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• 제22권12호
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• pp.701-705
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• 2012

The effects of clay, aluminum hydroxide, and carbon powder on the sintering of a Si/SiC mixture from photovoltaic silicon-wafer production were investigated. Sintering temperature was fixed at $1,350^{\circ}C$ and the sintered bodies were characterized by SEM and XRD to analyze the microstructure and to measure the apparent porosity, absorptivity, and apparent density. The XRD peak intensity of SiC in the sintered body was increased by adding 5% carbon to the Si/SiC mixture. From this result, it is confirmed that Si in the Si/SiC mixture had reacted with the added carbon. Addition of aluminum hydroxide decreased the cristobalite phase and increased the stable mullite phase. The measurement of the physical properties indicates that adding carbon to the Si/SiC mixture enables us to obtain a dense sintered body that has high apparent density and low absorptivity. The sintered body produced from the Si/SiC mixture with aluminum hydroxide and carbon powder as sintering additives can be applied to diesel particulate filters or to heat storage materials, etc., since it possesses high thermal conductivity, and anticorrosion and antioxidation properties.

• 플랜트 저널
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• 제16권3호
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• pp.47-52
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• 2020

본 연구에서는 알루미늄으로 제작된 심해 장비의 부식 저항 능력 향상시키기 위해 알루미늄 부식 방지 방법과 측정방법을 조사하였다. 조사된 부식 방지 방법은 Cathodic Protection(음극화 보호), Conversion Coating, Anodizing, 및 Organic Coating이었다. 그리고 간단하게 조사된 측정 방법은 Scanning Electron Microscope (SEM), Electrochemical Impedance Spectroscopy (EIS), Glow discharge optical emission spectrum spectroscopy (GD-OES), Fourier Transform Infrared Spectroscopy (FT-IR), Transmission Electron Microscopy (TEM), X-ray Photoelectron Spectroscopy (XPS), Scanning Vibrating Electrode Technique (SVET), Contact Angle(접촉각), Interfacial Tension (경계면 장력)이었다. 알루미늄 부식을 방지하기 위해 널리 사용되는 방법은 Anodizing과 Organic Coating이었으며, 부식 측정을 위해서는 여러 방법들이 골고루 사용되었다. 그 중 많이 사용되는 방법은 표면의 구조를 관찰하 위한 SEM과 부식 저항 능력을 측정하기 위한 접촉각 측정이었다.

• 대한기계학회논문집A
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• 제34권10호
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• pp.1549-1554
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• 2010

플라스틱 나사는 경량성, 내식성, 열 및 전기절연성이 우수하여 최근 금속나사 대체용도로 사용 되고 있다. 플라스틱 나사는 사출성형에 의해 제작되며 성형과정에서 수축이 발생하여 형상정밀도가 저하된다. 특히 소형 정밀나사의 경우 마이크로미터 단위의 정밀도를 요구하는 관계로 소성가공에 의해 제작되는 금속나사를 대체하기 위해서는 많은 어려움이 따른다. 본 연구에서는 사출성형 공정의 수치해석을 통해 금형설계 인자를 결정하였고, 실험계획법을 적용하여 변형량을 최소화하기 위한 성형조건을 도출함으로써 플라스틱 나사의 형상정밀도 향상을 위한 연구를 수행하였다.

• 보존과학회지
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• 제32권3호
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• pp.365-375
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• 2016

이 논문에서는 원각사지 십층석탑 표면에 발생한 오염물의 형성과정을 연구하였다. 연구결과, 흑색오염물은 석탑의 화학적인 풍화로 인해 석고가 일차적으로 형성되고 공기 중의 탄소화합물이 석탑표면에 고착되면서 생성된 흑연에 의해 발생한 것으로 판단되며, 발생시기는 1933년 이전으로 확인되었다. 백색오염물은 보호각 상부 마감재의 노후화 및 구조물의 훼손으로 발생한 방해석이 석탑표면에 재결정화 되면서 형성되었으며, 발생시기는 보호각이 설치된 1998년에서 2013년 사이에 발생한 것으로 판단된다. 원각사지 십층석탑의 장기적인 보존을 위해서는 보호각 상부에 형성된 오염물의 제거, 구조물의 방청처리 및 지속적인 모니터링이 요구된다.