• Corrosion Science and Technology
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• 제9권1호
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• pp.34-38
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• 2010

Electrochemical study on cut edge corrosion of prepainted Zn coated (GI) and 55%Al-Zn coated (GL) steels has been performed in wet-dry cyclic conditions. Maximum width of delaminated polymer coating from the cut edge for GI and GL specimens was evaluated under wet-dry cyclic conditions. The cyclic tests were carried out for 1000 h by changing of relative humidity, where the salt of NaCl was deposited on the specimen every 48 h. The cut edge corrosion test under NaCl deposit indicated that the delamination of the GL specimen progresses at a higher rate than the GI. The electrochemical corrosion monitoring was also performed under condition of alternate exposure to immersion in NaCl solution and drying at 60%RH and $25^{\circ}C$. On the basis of the results of the delamination tests and electrochemical measurements, the mechanism of cut edge corrosion for GI and GL were discussed.

• Journal of Electrochemical Science and Technology
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• 제9권1호
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• pp.1-8
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• 2018

The effect of mixing ratio on the corrosion protection of carbon steel coated by a film composed of poly(vinylidene) fluoride (PVDF) and poly(methyl methacrylate) (PMMA) was examined using electrochemical impedance spectroscopy. Surface crystallization behavior and thermal properties of the PVDF/PMMA coated carbon steel were evaluated using polarized optical microscopy and differential scanning calorimetry, respectively. A Maltese cross-pattern spherulite crystal was observed in the PVDF/PMMA coating film, which became more apparent with increasing PVDF content. The highest corrosion protection performance was achieved with 60 wt.% PVDF-coated carbon steel, and delamination and corrosion reactions were observed for 20 wt.% PVDF-coated carbon steel. Further, corrosion protection performance with an amorphous/crystal mixture (PVDF/PMMA, 60/40 (w/w)) was better than those observed in the amorphous domain and the perfect-crystal domain of the PVDF/PMMA blended coating system.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2014년도 제46회 동계 정기학술대회 초록집
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• pp.385.2-385.2
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• 2014

그래핀은 전기적, 광학적, 역학적, 열적 특성 등이 아주 좋은 소재이다. Thermal Chemical Vapor Deposition (T-CVD) 장비를 이용 저 진공, 고온에서 CH4과 H2를 가스를 사용하여 그래핀을 합성을 하였다. 그래핀은 탄소만으로 이루어진 2차원 층상구조를 가지고 있다. 촉매 금속 위에서 합성이 이루어지기에 합성된 그래핀을 바로 다른 응용하기에는 어려움이 따른다. 따라서 촉매 금속에서 그래핀을 분리하여 원하는 곳으로 옮기는 과정이 필요한데, 이를 전사공정이라 한다. 최근 전기분해를 이용하여 발생되는 수소 버블을 사용하여 그래핀을 촉매로 사용되는 금속으로부터 분리해내는 Electrochemical Delamination(ED) 전사방식이 소개가 되었다. 이러한 전사 방식의 장점은 촉매기판을 제거하지 않음으로써, 다시 재활용이 가능하고, 공정에 필요한 시간이 짧다. 또한 표면에서 직접적으로 분리하는 방식이기에 촉매 금속의 양면을 사용이 가능하다. 이러한 ED방식의 장점이 있기에 공정의 최적 조건을 잡기 위하여 변수들을 바꾸어가면서 실험을 하였다. 전사된 그래핀은 표면을 광학현미경으로 확인하였고, 라만 분광기를 사용하여 라만 스펙트럼과 기본적인 전기특성을 확인하여 특성을 평가하면서, 기존의 전사방식을 사용한 그래핀 샘플과 비교분석 하였다.

• Corrosion Science and Technology
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• 제6권1호
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• pp.18-23
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• 2007

DLC coatings have been deposited onto substrate of STS 316L and Ti alloy using r.f. PACVD (plasma-assisted chemical vapor deposition) with a mixture of $C_{6}H_{6}$ and $SiH_{4}$ as the process gases. Corrosion performance of DLC coatings was investigated by electrochemical techniques (potentiodynamic polarization test and electrochemical impedance spectroscopy) and surface analysis (scanning electron microscopy). The electrolyte used in this test was a 0.89% NaCl solution of pH 7.4 at temperature $37^{\circ}C$. The porosity and protective efficiency of DLC coatings were obtained using potentiodynamic polarization test. Moreover, the delamination area and volume fraction of water uptake of DLC coatings as a function of immersion time were calculated using electrochemical impedance spectroscopy. This study provides the reliable and quantitative data for assessment of the effect of substrate on corrosion performance of Si-DLC coatings. The results showed that Si-DLC coating on Ti alloy could improve corrosion resistance more than that on STS 316L in the simulated body fluid environment. This could be attributed to the formation of a dense and low-porosity coating, which impedes the penetration of water and ions.

• Journal of Electrochemical Science and Technology
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• 제3권2호
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• pp.68-71
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• 2012

The electrospinning technique is a revolutionary template-catalyst-free method that can generate 1D nanostructure with the tunability and the potential for the mass production. This approach received a great deal of attention due to its ability to give direct pathways for electrical current and has been utilized in various electronic applications. However, the delamination of inorganic electrospun film has prevented the intense utilization due to the thermal expansion/contraction during the calcination. In this study, we propose an electrical grounding method for transparent conducting oxide and electrospun nanowires to enhance the adhesion after the calcination. Then, we examined the potential of the technique on ZnO based dye-sensitized solar cells.

• Journal of Electrochemical Science and Technology
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• 제12권2호
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• pp.246-256
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• 2021

Mo,Cu-doped CeO₂ (CMCuO) nanopowders were synthesized by the nitrate-fuel combustion method aiming to improve the electrical and electrochemical properties of its Mo-doped CeO₂ (CMO) parent by the addition of copper. An electrical conductivity of ca. 1.22·10^-2 S cm^-1 was measured in air at 800℃ for CMCuO, which is nearly 10 times higher than that reported for CMO. This increase was associated with the inclusion of copper into the crystal lattice of ceria and the presence of Cu and Cu₂O as secondary phases in the CMCuO structure, which also could explain the increase in the charge transfer activities of the CMCuO based anode for the hydrogen and carbon monoxide electro-oxidation processes compared to the CMO based anode. A maximum power density of ca. 120 mW cm^-2 was measured using a CMCuO based anode in a solid oxide fuel cell (SOFC) with YSZ electrolyte and LSM-YSZ cathode operating at 800℃ with humidified syngas as fuel, which is comparable to the power output reported for other SOFCs with anodes containing copper. An increase in the area specific resistance of the SOFC was observed after ca. 10 hours of operation under cycling open circuit voltage and polarization conditions, which was attributed to the anode delamination caused by the reduction of the Cu₂O secondary phase contained in its microstructure. Therefore, the addition of a more electroactive phase for hydrogen oxidation is suggested to confer long-term stability to the CMCuO based anode.

• 한국결정성장학회지
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• 제33권6호
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• pp.203-209
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• 2023

차세대 나트륨이온전지용 음극 소재로 유망한 코발트 황화물 나노복합체를 간단한 수열법을 통해 합성하였다. 본 연구에서는 배터리의 전기화학적 에너지 저장 성능 향상을 위해 코발트 황화물 나노입자와 환원된 산화그래핀과 복합화 된 코발트 황화물 나노복합체를 제조하여 비교해주었다. 제조된 나노복합체 전극은 가역적이고 안정적인 사이클 성능(전류밀도 200 mA g^-1에서 30 사이클 후 62 %)을 보였다. 개선된 전기화학적 특성은 수열합성 과정에서 코발트 황화물의 입자 크기가 작고 균일하게 분포되어 나트륨 이온의 확산 경로를 극대화함에서 기인하였다. 뿐만 아니라 전환 반응 중 음극재의 박리 및 부피 팽창을 효과적으로 억제함으로써 차세대 나트륨이온전지용 유망한 음극 소재로써의 가능성을 보여주었다.

• 접착 및 계면
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• 제19권2호
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• pp.84-94
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• 2018

Electrically debonding adhesives[EDA], one of the controlled delamination materials[CDM] is reviewed. CDM can be defined as the ability to separate adhesive bonded assemblies without causing damage to the substrates. Its application includes electronics, medical surgery, dentistry, building and general manufacturing where the opportunity to separate assemblies is important. There are several important mechanisms of EDAs; faradaic reaction, phase separation and anode detachment, cathodic debonding, gas emission mechanism, and mechanical stresses. These mechanisms are reviewed with various research results. Since the mechanism behind the electrochemical debonding of adhesives is not well understood, this review aims to help the research scientists in the industries. Finally, new applications of EDA are introduced as new business opportunity.

• 전기화학회지
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• 제21권3호
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• pp.47-54
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• 2018

동일 전극 로딩 조건(${\sim}15mg\;cm^{-2}$)에서 면적당 용량($mAh\;cm^{-2}$)을 극대화하기 위해, 고분자 바인더의 함량을 4, 2, 1 wt%로 줄인 $LiNi_{0.5}Co_{0.2}Mn_{0.3}O_2$ 전극을 제조하였다. 바인더 함량이 1 wt%로 낮춘 경우, 압연 후 펀칭 과정에서 전극 코팅층이 부분적으로 박리되는 문제가 발생하여 추가 분석은 진행되지 않았다. 전극 내 바인더 함량을 4 wt%에서 2 wt%로 줄이면, 계면 접착력은 0.4846에서 $0.2627kN\;m^{-1}$로 약 46% 감소하고, 전극 코팅층의 강도도 3.847에서 2.013 MPa로 약 48%가 떨어졌다. 그러나, 두 전극을 리튬 전극과 반쪽 전지로 구성하여 전기화학적 특성을 살펴보면, 초기 방전 용량과 충방전 효율은 유사하였다. 하지만, 단기 수명 평가에서 2 wt% 바인더 전극은 수명 특성이 떨어질 뿐만 아니라, 전지를 분해하는 과정에서 전극 코팅층이 집전체에서 박리되는 현상이 관찰되었다. 반면, 4 wt% 바인더 전극은 높은 전극 로딩조건에서도 전극 코팅층과 집전체 계면이 잘 유지되고 있음이 확인되었다.

• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2010년도 추계학술대회 초록집
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• pp.86.2-86.2
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• 2010

In order to improve polymer electrolyte membrane fuel cell (PEMFC) durability, the durability of membrane electrode assemblies (MEA), in which the electrochemical reactions actually occur, is one of the vital issues. Many articles have dealt with catalyst layer degradation of the durability-related factors on MEAs in relation to loss of catalyst surface area caused by agglomeration, dissolution, migration, formation of metal complexes and oxides, and/or instability of the carbon support. Degradation of catalyst layer during long-term operation includes cracking or delamination of the layer which result either from change in the catalyst microstructure or loss of electronic or ionic contact with the active surface, can result in apparent activity loss in the catalyst layer. Membrane degradation of the durability-related factors on MEAs can be caused by mechanical or thermal stress resulting in formation of pinholes and tears and/or by chemical attack of hydrogen peroxide radicals formed during the electrochemical reactions. All of these effects, the mechanical damage of membrane and degradation of catalyst layers are more facilitated by uneven stress or improper MEA fabrication process. In order to improve the PEMFC durability, therefore, it is most important to minimize the uneven stress or improper MEA fabrication process in the course of the fabrication of MEA. We analyzed the effects of the MEA fabrication condition on the PEMFC durability with MEA produced using CCM (catalyst coated membrane) method. This paper also investigated the effects of MEA fabrication condition on the PEMFC durability by adding additional treatment process, hot pressing and pressing, on the MEA produced using CCM method.