• 한국구조물진단유지관리공학회 논문집
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• 제15권6호
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• pp.201-211
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• 2011

우리나라는 삼면이 바다로 이루어져 있으며 많은 철근콘크리트 구조물이 위치해 있다. 만약 철근콘크리트 구조물이 염해의 노출이 장기화 된다면 철근의 부식으로 인하여 철근-콘크리트 부착성능이 감소될 뿐만 아니라, RC 구조물의 성능저하가 우려되고 있다. 따라서 본 연구에서는 부착성능이 상실된 RC 보-기둥 접합부에 대한 기초자료를 확보하기 위해 연구를 수행하였다. 철근-콘크리트 부착이 상실된 보-기둥 접합부를 제작하여 부착 및 비부착 특성 여부에 따라 반복 횡하중 실험 및 해석적 연구를 수행하여 접합부의 성능을 평가 및 고찰하였다.

• 한국표면공학회지
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• 제52권4호
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• pp.233-238
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• 2019

The formation behavior of zinc phosphate conversion coating (ZPCC) on SCM430 alloy was investigated in 25 vol.% of 1M ZnO + 170 ml/L solution containing various $Fe(NO_3)_2$ concentrations, using open-circuit potential(OCP), electrochemical impedance spectroscopy(EIS), cyclic polarization(CP) curve and tape peel test. OCP of SCM430 alloy and corrosion current density increased with increasing $Fe(NO_3)_3$ concentration. Resistance of films formed on SCM430 alloy by chemical conversion treatment decreased with increasing $Fe(NO_3)_3$ concentration. Color and adhesion of chemical conversion coatings became darker and worse, respectively, with increasing $Fe(NO_3)_3$ concentration. It is concluded that addition of $Fe(NO_3)_3$ into a zinc phosphating bath leads to faster reaction to form porous surface coatings with poor adhesion and corrosion resistance.

• 대한금속재료학회지
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• 제47권2호
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• pp.129-137
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• 2009

Corrosion behaviors of TiN coated dental casting alloys have been researched by using various electrochemical methods. Three casting alloys (Alloy 1: 63Co-27Cr-5.5Mo, Alloy 2: 63Ni-16Cr-5Mo, Alloy 3: 63Co-30Cr-5Mo) were prepared for fabricating partial denture frameworks with various casting methods; centrifugal casting(CF), high frequency induction casting(HFI) and vacuum pressure casting(VP). The specimens were coated with TiN film by RF-magnetron sputtering method. The corrosion behaviors were investigated using potentiostat (EG&G Co, 263A. USA) in 0.9% NaCl solution at $36.5{\pm}1^{\circ}C$. The corrosion morphologies were analyzed using FE-SEM and EDX. Alloy 1 and Alloy 2 showed the ${\alpha}-Co$ and ${\varepsilon}-Co$ phase on the matrix, and it was disappeared in case of TiN coated Alloy 1 and 2. In the Alloy 3, $Ni_2Cr$ second phases were appeared at matrix. Corrosion potentials of TiN coated alloy were higher than that of non-coated alloy, but current density at passive region of TiN coated alloy was lower than that of non-coated alloy. Pitting corrosion resistances were increased in the order of centrifugal casting, high frequency induction casting and vacuum pressure casting method from cyclic potentiodynamic polarization test.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2008년도 춘계 학술발표회 제20권1호
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• pp.101-104
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• 2008

염해에 노출이 심한 구조물이나 교량의 상판의 보강철근 부식으로 인한 콘크리트 구조물의 구조성능 및 내구성능의 저하가 큰 문제로 대두되고 있다. 이에 최근 활발히 연구가 진행 중인 섬유보강근(Fiber Reinforced Polymer Bar, 이하 FRP 보강근)은 높은 화학적 내구성, 고강도, 경량성 등에 의하여 철근을 대체할 콘크리트 보강재로 그 가치를 인정받아 미국, 유럽, 캐나다 등에서는 이미 FRP 보강근의 설계지침서가 발표되었다. 하지만 아직 FRP 보강근을 이형철근과 같이 높은 신뢰성을 가지는 보강재로 사용하기에는 파악해야할 구조적 문제가 많이 있는데 그 중 하나가 콘크리트와의 부착성능이다. FRP 보강근의 부착성능은 콘크리트 압축강도에 크게 영향을 받는 이형철근과 달리 섬유종류, 외피 표면 상태 등 여러 가지 요소에 의한 복합적 영향을 받는 부착특성을 보인다. 이에 본 연구에서는 외피 표면 상태, 콘크리트 압축강도, 반복하중 작용 등을 변수로 하는 GFRP 보강근으로 보강된일 방향 인장-인발 시편의 부착실험을 통하여 GFRP 보강근의 부착특성을 관찰하고자 하였다. 실험 결과 콘크리트 압축강도의 증가에 따라 GFRP 보강근의 부착강도는 증가하였으며 반복하중의 작용에 의하여 단조하중에서의 부착강도에 비하여 GFRP 보강근의 부착강도는 감소하는 결과를 보였다.

• 한국산학기술학회논문지
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• 제14권12호
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• pp.6098-6105
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• 2013

본 연구에서는 해수용 열교환기 적용을 위한 열분사코팅의 종류에 따른 부식특성 및 열전도 성능을 조사하기 위해 실험이 수행되었다. 코팅은 아연과 알루미늄을 열분사코팅한 뒤 실리콘 및 에폭시 수지를 추가 도포한 시편을 선정하였다. 코팅의 부식특성 변화를 관찰하기 위하여 사이클릭 선도변화 측정 및 SEM촬영을 이용하였다. 시편의 열전도 성능을 측정하기 위해서 레이저 확산법을 이용하여 열전도도를 비교하였으며 추가도포를 실리콘으로 한 경우 3 ~ 4% 에폭시로 한 경우 70 ~ 75%의 열전도도 하락이 발생하였다.

• 한국건축시공학회지
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• 제19권6호
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• pp.495-501
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• 2019

최근 철근의 대체재로서 인장강도나 내부식성이 좋은 CFRP(carbon fiber reinforced polymer)를 이용한 연구가 활발히 진행되고 있다. 그러나 현재 피로 파괴에 대한 연구는 미비한 상태이다. 따라서 본 연구에서는 CFRP보강 콘크리트 보를 제작하여 정적 및 반복 하중에 따른 역학적 거동과 파괴형태를 분석하고 철근의 대체 재료로서 CFRP 보강근 사용에 대한 안전성과 타당성을 평가하도록 하였다. 반복하중의 범위는 극한하중의 10~70%를 취하고 3점 재하방식으로 sine파를 이용한 3Hz의 속도로 재하 하였다. 정적 실험결과 보강량의 증가에 따라 보의 최대하중이나 강성은 현저하게 증가하였지만 피로 실험결과 보강량의 증가에 따라 반복 횟수는 감소하고 처짐량은 증가하여 안전성은 다소 감소됨을 알 수 있었다.

• 한국정밀공학회지
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• 제29권4호
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• pp.409-416
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• 2012

Recently, surface modification technology is of importance to improve the wear resistance and the corrosive resistance for high accurate mechanical parts such as LM guide, Ball Screw and Roller Bearing etc., Those has generally featured on rolling contact mechanism to improve not only the wear and the friction, but also the accuracy and the corrosion performances. For surface modifications of high accurate mechanical parts, normally thermal spray, PVD, CVD and E.P. processes have been used with many materials such as DLC, raydent, W, Ni, Ti etc. Diamondlike carbon (DLC) films possess a combination of attractive properties and have been largely employed to modify the tribological behaviors such as friction, wear, corrosion, fretting fatigue, biocompatibility, etc. However, for rolling contact mechanism mechanical parts DLC films are needed to study for commercial benefit. Rolling contact mechanism has features on effects of cyclic motions and stresses, and also not simply sliding motions. The papers focused on the performance test of wear and corrosive resistance according to Me-DLC film thickness. And also, its thickness effect of wear analysis was carried out through the simulation of the maximum shear stress under the rolling contact surface. As the results, Me-DLC films have more potential to improve the wear resistance for high precision mechanical parts than raydent films.

• Journal of Electrochemical Science and Technology
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• 제9권1호
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• pp.9-19
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• 2018

The anodic behavior of aluminum (Al) foils with varying purity, capacitance, and withstand voltage in organic electrolytes was examined for EDLC. The results of cyclic voltammetry (CV) and chronoamperometry (CA) experiments showed that the electrochemical stability improves when Al foil has higher purity, lower capacitance, and higher withstand voltage. To improve the electrochemical stability of EDLC current collectors made of low-purity foil (99.4% Al foil), the foil was modified by chemical etching to reduce its capacitance to $60{\mu}F/cm^2$ and forming to have withstand a voltage of 3 Vf. EDLC cells using the modified Al foil as a current collector were made to 2.7 V with 360 F, and a constant voltage load test was subsequently performed for 2500 hours at high temperature under a rated voltage of 2.7 V. The reliability and stability of the EDLC cell improved when the modified Al foil was used as a current collector. To understand the deterioration process of the Al current collector, standard cells made of conventional Al foil under a constant voltage load test were disassembled, and the surface changes of the foil were measured every 500 hours. The Al foil became increasingly corroded, causing the adhesion between the AC coating layer and the Al foil to weaken, and it was confirmed that partial AC coating layer peeling occurred.

• 전기화학회지
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• 제16권1호
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• pp.30-38
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• 2013

In this study, a catalyst slurry was prepared with a Pt/C catalyst, Nafion ionomer solution as a binder, an ionic liquid (IL) (1-butyl-3-methylimidazolium tetrafluoroborate), deionized water and ethanol as a solvent for the application to polymer electrolyte fuel cells (PEFCs) at high-temperatures. The effect of the IL in the electrode of each design was investigated by performing a cyclic voltammetry (CV) measurement. Electrodes with different IL distributions inside and on the surface of the catalyst electrode were examined. During the CV test, the electrochemical surface area (ESA) obtained for the Pt/C electrode without ILs gradually decreased owing to three mechanisms: Pt dissolution/redeposition, carbon corrosion, and place exchange. As the IL content increased in the electrode, an ESA decrement was observed because ILs leaked from the Nafion polymer in the electrode. In addition, the CVs under conditions simulating leakage of ILs from the electrode and electrolyte were evaluated. When the ILs leaked from the electrode, minor significant changes in the CV were observed. On the other hand, when the leakage of ILs originated from the electrolyte, the CVs showed different features. It was also observed that the ESA decreased significantly. Thus, leakage of ILs from the polymer electrolyte caused a performance loss for the PEFCs by reducing the ESA. As a result, greater entrapment stability of ILs in the polymer matrix is needed to improve electrode performance.

• Advances in concrete construction
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• 제9권3호
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• pp.313-326
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• 2020

Glass fiber-reinforced polymer (GFRP) bars have been introduced as an effective alternative for the conventional steel reinforcement in concrete structures to mitigate the costly consequences of steel corrosion. However, despite the superior performance of these composite materials in terms of corrosion, the effect of replacing steel reinforcement with GFRP on the seismic performance of concrete structures is not fully covered yet. To address some of the key parameters in the seismic behavior of GFRP-reinforced concrete (RC) structures, two full-scale beam-column joints reinforced with GFRP bars and stirrups were constructed and tested under two phases of loading, each simulating a severe ground motion. The objective was to investigate the effect of damage due to earthquakes on the service and ultimate behavior of GFRP-RC moment-resisting frames. The main parameters under investigation were geometrical configuration (interior or exterior beam-column joint) and joint shear stress. The performance of the specimens was measured in terms of lateral load-drift response, energy dissipation, mode of failure and stress distribution. Moreover, the effect of concrete damage due to earthquake loading on the performance of beam-column joints under service loading was investigated and a modified damage index was proposed to quantify the magnitude of damage in GFRP-RC beam-column joints under dynamic loading. Test results indicated that the geometrical configuration significantly affects the level of concrete damage and energy dissipation. Moreover, the level of residual damage in GFRP-RC beam-column joints after undergoing lateral displacements was related to reinforcement ratio of the main beams.