• Journal of Electrochemical Science and Technology
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• 제9권1호
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• pp.69-77
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• 2018

Aluminum electrodeposition was carried out in dimethylsulfone ($DMSO_2$) baths containing 6.2-28.3 mol% $AlCl_3$ at 403 K. The electrochemically active species for Al electrodeposition in $DMSO_2$ baths were investigated. Electrochemical behavior of the electrolyte and the deposition mechanism were studied via cyclic voltammetry (CV). Properties of the deposits were assessed by scanning electron microscopy with energy-dispersive X-ray spectroscopy and X-ray diffraction. In addition, structures of the ionic complexes formed with aluminum in the bath were characterized by $^{27}Al$ nuclear magnetic resonance (NMR) spectroscopy. NMR spectra revealed that all baths contained two ionic species: $AlCl_4{^-}$ and $[Al(DMSO_2)_3]^{3+}$. Al electrodeposited when the $[Al(DMSO_2)_3]^{3+}$ concentration was the highest (23.3 mol% $AlCl_3$) exhibited fine grain sizes, relatively smooth surfaces, and high purities.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2006년도 제37회 하계학술대회 논문집 C
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• pp.1305-1306
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• 2006

A monolayer assembly of anthracene-viologen linked thiol ($AMVC_{8}SH$) was fabricated on a gold electrode by self-assembly method. Structural property of the self-assembled monolayers (SAMs) was carried out by optical and electrochemical method. Firstly, we investigated PL spectrum and UV/visible absorption for the optical properties in solution state. Secondly, we determined the characteristics of charge transfer in different electrolyte solutions by electrochemical quartz crystal microbalance (EQCM). From the data, the PL spectrum and UV/visible absorption were observed and the well-defined shape peaks were nearly equal charges during redox reactions and existed to an excellent linear relationship between the scan rates and existed to currents. The mass change was determined during redox reaction. The mass change behavior of SAMs was not only governed by the mobility of the ion in the viologen but the valence of the ion in the electrolyte solution.

• 한국재료학회지
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• 제9권6호
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• pp.622-629
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• 1999

Effects of the fluorination in the $K_2$TiF\ulcorner solution and in-situ KF+ KOH electrolyte on the electrochemical charge-discharge properties of CaNi\ulcorner and the Mg-CaNi\ulcorner electrodes were investigated. In-situ fluorination in the KF+ KOH electrolyte compared with pre-fluorination in the$ K_2$TiF\ulcorner solution could improve the electrochemical cycling durability of CaNi\ulcorner and MG-CaN\ulcorner electrodes. The fluorinated layer on the alloy surface by pre-fluorination to improve the activity and anti-corrosion of the electrodes was dissolved in the pure KOH electrolyte during the cycling. The fluorinated layer was formed continuously on the surface of the electrode by thee2N KF addition in the 6N KOH electrolyte. The excess F\ulcorner ion addition in KOH electrolyte could improve the electrochemical cycling durability of CaNi\ulcorner and Mg-CaNi\ulcorner electrode. But, in case of MG-CaNi\ulcorner electrode, the discharge capacity of the electrode was reduced and the poor cycling property was shown with increasing of the MG process times.

• 대한금속재료학회지
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• 제50권5호
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• pp.395-400
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• 2012

In this study, we have investigated the surface morphology of hydroxyapatite (HA) coated Ti alloy surface using pulsed laser plating. The HA (tooth ash) films were grown by pulsed KrF excimer laser, film surfaces were analyzed for topology, chemical composition, crystal structure and electrochemical behavior. The Ti-6Al-4V alloy showed ${\alpha}$ and ${\beta}$ phase, Cp-Ti showed ${\alpha}$ phase and the HA coated surface showed HA and Ti alloy peaks. The HA coating layer was formed with $1-2{\mu}m$ droplets and grain-like particles, particles which were smaller than the HA target particle, and the composition of the HA coatings were composed of Ca and P. From the electrochemical test, the pitting potential (1580 mV) of HA coated Ti-6Al-4V alloy was higher than those of Cp-Ti (1060 mV) and HA coated Cp-Ti (1350 mV). The HA coated samples showed a lower current density than non-HA coated samples, whereas, the polarization resistance of HA coated samples showed a high value compared to non-HA coated samples.

• 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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• 제20권6호
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• pp.466-474
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• 2021

A wet type scrubber for merchant vessel uses super austenitic stainless steels with pitting resistance equivalent number (PREN) of 40 or higher for operation in a harsh corrosive environment. However, it is expensive due to a high nickel content. Thus, electrochemical behavior and cavitation erosion characteristics of UNS S32750 as an alternative material were investigated. Microstructure analysis revealed fractions of ferritic and austenitic phases of 48% and 52%, respectively, confirming the existence of ferritic matrix and austenitic island. Potentiodynamic polarization test revealed damage at the interface of the two phases because of galvanic corrosion due to different chemical compositions of ferritic and austenitic phases. After a cavitation test, a compressive residual stress was formed on the material surface due to impact pressure of cavity. Surface hardness was improved by water cavitation peening effect. Hardness value was the highest at 30 ㎛ amplitude. Scanning electron microscopy revealed wave patterns due to plastic deformation caused by impact pressure of the cavity. The depth of surface damage increased with amplitude. Cavitation test revealed larger damage caused by erosion in the ferritic phase due to brittle fracture derived from different strain rate sensitivity index of FCC and BCC structures.

• 방사성폐기물학회지
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• 제20권1호
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• pp.33-41
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• 2022

Liquid Bi pool is a candidate electrode for an electrometallurgical process in the molten LiCl-KCl eutectic to treat the spent nuclear fuels from nuclear power plants. The electrochemical behavior of Bi³⁺ ions and the electrode reaction on liquid Bi pool were investigated with the cyclic voltammetry in an environment with or without BiCl₃ in the molten LiCl-KCl eutectic. Experimental results showed that two redox reactions of Bi³⁺ on inert W electrode and the shift of cathodic peak potentials of Li⁺ and Bi³⁺ on liquid Bi pool electrode in molten LiCl-KCl eutectic. It is confirmed that the redox reaction of lithium with respect to the liquid Bi pool electrode would occur in a wide range of potentials in molten LiCl-KCl eutectic. The obtained data will be used to design the electrometallurgical process for treating actinide and lanthanide from the spent nuclear fuels and to understand the electrochemical reactions of actinide and lanthanide at liquid Bi pool electrode in the molten LiCl-KCl eutectic.

• Journal of Electrochemical Science and Technology
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• 제13권1호
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• pp.138-147
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• 2022

The synergistic effect of 2-chloromethylbenzimidazole (2-CBI) and potassium iodide (KI) for mild steel in 1 M hydrochloric acid solution was investigated by potentiodynamic polarization curves and electrochemical impedance spectroscopy (EIS). The results showed that, with the addition of 100 ppm potassium iodide, the inhibition efficiecy (IE) of 100 ppm 2-CBI in 1 M hydrochloric acid had been improved from 91.14% to 96.15%. And synergistic parameter of 100 ppm 2-CBI with different amounts of potassium iodide is always greater than 1. The adsorption of potassium iodide combining with 100 ppm 2-CBI obeys to the Langmuir adsorption isotherm. Thermodynamic adsorption parameters, including ∆G⁰_ads, ∆H_a and ∆S_a of the adsorption of the combinned inhibitor, as well as the E_a of the mild steel corrosion in 1 M HCl with the combinned inhibitor, were calculated.

• Corrosion Science and Technology
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• 제8권2호
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• pp.62-67
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• 2009

Ti and Ti-alloys have good biocompatibility, appropriate mechanical properties and excellent corrosion resistance. However, the widely used Ti-6Al-4V is found to release toxic ions (Al and V) into the body, leading to undesirable long-term effects. Ti-6Al-4V has much higher elastic modulus (100 GPa) than cortical bone (20 GPa). Therefore, titanium alloys with low elastic modulus have been developed as biomaterials to minimize stress shielding. The electrochemical behavior of surface-modified and MC3T3-E1 cell-cultured Ti-30(Nb,Ta) alloys with low elastic modulus have been investigated using various electrochemical methods. Surfaces of test samples were treated as follows: $0.3{\mu}m$ polished; $25{\mu}m$, $50{\mu}m$ and $125{\mu}m$ sandblasted. Specimen surfaces were cultured with MC3T3-E1 cells for 2 days. Average surface roughness ($R_a$) and morphology of specimens were determined using a surface profilometer, OM, and FE-SEM. Corrosion behavior was investigated using a potentiostat(EG&G PARSTAT 2273), and electrochemical impedance spectroscopy was performed (10 mHz to 100 kHz) in 0.9% NaCl solution at $36.5{\pm}1^{\circ}C$. The microstructures of the Ti-30(Ta,Nb) alloys had a needle-like appearance. The $R_a$ of polished Ti-30Ta and Ti-30Nb alloys was lower than that of the sandblasted Ti alloy. Cultured cells displayed round shapes. For polished alloy samples, cells were well-cultured on all surfaces compared to sandblasted alloy samples. In sandblasted and cell-cultured Ti-30(Nb,Ta) alloy, the pitting potential decreased and passive current density increased as $R_a$ increased. Anodic polarization curves of cell-cultured Ti alloys showed unstable behavior in the passive region compared to non-cell-cultured alloys. From impedance tests of sandblasted and cell-cultured alloys, the polarization resistance decreased as $R_a$ increased, whereas, $R_a$ for cell-cultured Ti alloys increased compared to non-cell-cultured Ti alloys.

• 콘크리트학회논문집
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• 제29권1호
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• pp.109-116
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• 2017

본 연구에서는 콘크리트 중의 철근부식의 보수로 전기방식법을 적용할 경우의 탈염, 부식복원 및 구조거동을 효과적이고 정량적으로 평가하였다. $160{\times}160{\times}1000mm$의 콘크리트 시편을 제작하였으며 피복두께 20 mm의 원형철근 3본을 매립하였으며 콘크리트 타설 시 염소이온 5.0%를 혼입하여 철근부식을 가속한 뒤 전기방식을 인가하였다. 전기방식 전류는 직류 $750mA/m^2$를 2, 4, 8주간 인가하였다. 결과로서 탈염효과는 인가 기간에 따라 증가하였으며 최대 탈염비는 8주간의 인가 시 64.7-83.7%로 측정되었다. 이는 시멘트계에서 염소이온의 50-60%가 고정화됨을 고려할 때, 일정량의 고정화된 염소이온 역시 탈염된 것으로 판단된다. 또한 부식상태는 8주간의 전기방식 이후에도 $6.5mA/m^2$의 부식 전류 및 330 mV (vs. SCE)의 부식전위를 나타내 여전히 부식이 존재함을 확인하였다. 구조거동에 있어 부식의 증가로 인해 콘크리트의 최대하중은 증가하였으나, 전기방식을 적용함에 따라 오히려 최대하중은 감소하였으나 Control시편보다는 상회한 값을 나타내 전기방식이 구조적 악영향은 없음을 확인하였다.