• Applied Chemistry for Engineering
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• v.7 no.2
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• pp.228-236
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• 1996

An electrolysis system with a vertically circulating mercury capillary bundle electrode was developed with a very large electrode area in a minimum space. This system was operated by forcedly feeding mercury and aqueous solution containing metal ion into a fiber bundle packed densely within a small porous glass tube. In order to test the characteristics and stability of the electrolysis system, the reduction voltammograms of uranyl and ferric ions were measured with changes of the mercury flow rate and the aqueous flow rate. The aqueous flow rate had a large effect on the electrochemical reaction of metal ion occurring at the interface between the mercury and the aqueous solution and had to be regulated as an appropriate value to have a good limiting current shape. The limiting current was linearly proportional to the aqueous flow rate, and complete reductions of uranyl and ferric ions were rapidly and continuously accomplished at the potential showing limiting current. With a mercury flow rate high enough to keep a capillary continuum of mercury in the fiber bundle, the mercury flow rate had almost no effect on the electrochemical reaction. This system was confirmed to be effective and stable enough to control rapidly and continuously the oxidation state of metal ions fed into the system under an appropriate aqueous flow rate.

• Applied Chemistry for Engineering
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• v.23 no.5
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• pp.505-509
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• 2012

In this study, we investigate the use of new carbon nanotube paste electrode (CNPE) for promoting the detection of lead (Pb) heavy metal in the a drinkable water, which negatively affects human brain and nerve system. For the evaluations, CNPE is served as a working electrode, while sensitivity and limit of detection (LOD) of Pb are measured in DI and tap water based electrolytes using squarewave anodic stripping voltammetry (SWASV). As a result of that, in the 25~150 ppb range of $Pb^{2+}$ ions, its sensitivity and calculated LOD are $12.85\;{\mu}A/{\mu}M$ and 26 ppb in DI water based 0.1 M $H_{2}SO_{4}$ electrolyte while they are $10.36\;{\mu}A/{\mu}M$ and 38 ppb electrolytes respectively. In addition, experimentally measured LOD values of Pb are 4 ppb and 10 ppb in the two water electrolytes. The stripping of $Pb^{2+}$ ion is also controlled by surface reaction. Our experimental data are then compared with those of other already published references. With the comparison, it is proved that our electrode outperforms other electrodes in terms of the sensitivity and LOD of trace Pb metal.

• Proceedings of the Korean Vacuum Society Conference
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• 2012.02a
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• pp.430-430
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• 2012

Modulated pulsed power (MPP) 스퍼터링은 펄스 전압 shape, amplitude, duration의 modulation을 통해 증착율 손실을 극복하는 고출력 펄스 마그네트론 스퍼터링의 한 종류이다. Micro second 범위에서 on/off 시간을 다중 세트 형태로 자유롭게 프로그램 할 수 있어서 아킹 없이 고전류 영역의 마그네트론 동작을 할 수 있으므로, 고주파 유도 결합 플라즈마원이나 마이크로웨이브 투입 등의 부가적인 플라즈마 없이도 스퍼터링 재료의 이온화 정도를 획기적으로 높일 수 있는 장점을 가지고 있다. 본 연구에서는 $2{\times}1{\times}0.2$의 sputtering system에서 기판 캐리어를 이용해서 $400{\times}400mm$ 기판을 $272{\times}500mm$ 크기의 AZO target (Al 2 wt%)이 설치되어 있는 moving magnet cathode (MMC)을 이용하여 MPP로 증착했다. 두 종류의 micro pulse set을 하나의 macro pulse에 사용함으로서 weakly ionized plasma와 strongly ionized plasma를 만들 수 있다. 다양한 micro pulse set을 이용하여 평균 전력 2 kW에서 peak 전력을 4 kW에서 45 kW까지 상승 시킬 수 있으며, 이 때 타겟-기판 거리 80 mm에서 이온전류밀도는 $5mA/cm^2$에서 $20mA/cm^2$까지 상승했다. MPP는 같은 평균 전력에서 repetition frequency가 증가할 때, 증착 속도가 증가했으며, 같은 repetition frequency에서 macro pulse length가 증가할 때도, 증착 속도가 증가했다. 최적화된 marco, micro pulse set에서 증착 속도는 평균 전력 2 kW에서 110 nm/min이었고, 700 nm의 박막에서 비저항은 $1-2{\times}10^{-3}ohm{\cdot}cm$였다. 표면거칠기 Rrms는 약 3 nm였고, 400-700 nm 영역의 평균 투과도는 72-76%였다.

• Journal of the Korean Electrochemical Society
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• v.13 no.3
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• pp.186-192
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• 2010

In situ electrochemical atomic force microscopy (ECAFM) observations of the surface of highly oriented pyrolytic graphite (HOPG) was performed before and after cyclic voltammetry in lithium bis(fluorosulfonyl)imide (LiTFSI) dissolved in 1-buthyl-2,3-dimethylimidazolium (BDMI)-TFSI to understand the interfacial reactions between graphite and BDMI-based ionic liquids. The formation of blisters and the exfoliation of graphene layers by the intercalation of $BDMI^+$ cations within HOPG were observed instead of reversible lithium intercalation and de-intercalation. On the other hand, lithium ions are reversibly intercalated into the HOPG and de-intercalatied from the HOPG without intercalation of the $BDMI^+$ cations in the presence of 15 wt% of 4.90 mol/$kg^{-1}$ LiTFSI dissolved in propylene carbonate (PC). ECAFM results revealed that the concentrated PC-based solution is a very effective additive for preventing $BDMI^+$ intercalation through the formation of solid electrolyte interface (SEI).

• Journal of the Korean Electrochemical Society
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• v.14 no.1
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• pp.38-43
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• 2011

Because the ionic liquid added with Propylene carbonate(PC) at room temperature has lower viscosity than original, we considered electrochemical behavior of it in EDLC. The ionic liquid without PC which does not have ions has no problem in capacity since it has enough ions. The electrolyte resistance was decreased with decreasing viscosity. As a result of identifying high current discharge capacity, we observed that the ionic liquid had capacity of 73.12% at current density of $80\;mA/cm^{-2}$, but it increased to 81.94% at PC content of 40 vol%.

• Journal of the Korean Electrochemical Society
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• v.19 no.3
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• pp.95-100
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• 2016

A method for electrochemical degradation of the perchlorate anion ($ClO_4{^-}$) using mercury film electrode has been studied. Electrochemical method has relatively simple pre-treatment. However, electrochemical method should avoid interference from hydrogen evolution at the applied potential to degradation of perchlorate ion, and thus applied electrode should have large hydrogen overvoltage which suppressed the hydrogen evolution at the working reduction potential to prevent hydrogen evolution. In this study, we used mercury film electrode as a working electrode which has a large overvoltage. Ag / AgCl (sat. NaCl) was used as a reference electrode, and platinum was used as a counter electrode. Mercury film electrode was made by cyclic voltammetry (CV) method. The deposition time was decided as 10 minute, and the stability of the mercury electrode in perchlorate solution was confirmed by CV. The reduction potential of perchlorate was checked by using CV method, and decomposition of perchlorate was performed by using chronoamperometric (CA) method. Also, ion chromatography (IC) was used to confirm the degradation rates of perchlorate.

• Journal of the Korea Concrete Institute
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• v.29 no.1
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• pp.109-116
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• 2017

The present study concerns quantitative assessment of chloride extraction, repassivation and structural behavior of concrete. Concrete specimen ($160{\times}160{\times}1000mm$) was fabricated with 3 steel bar located in the middle with 20 mm of the cover depth, containing 5.0% of chloride to accelerate corrosion process, then to be subjected to electrochemical treatment. The current density accounted for $750mA/m^2$ at 2, 4 and 8 weeks. As a result, it was found that an increase in the duration of the treatment resulted in an increase in the chloride extraction, accounting for 64.7-83.7% for the specimen at 8 weeks treatment. It implies that a portion of bound chlorides would turn free to be removed, considering the binding capacity of cement about 50-60% to total ones. Even after the treatment, the corrosion was still active; the corrosion rate was $6.5mA/m^2$ and 330 mV vs. SCE in the potential. For structural behavior, the maximum load was increased by corrosion on the steel bars, which was subsequently lowered by the treatment, but still higher than for control.

• Applied Chemistry for Engineering
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• v.9 no.7
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• pp.998-1003
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• 1998

$BaTiO_3$ thin film was electrochemically deposited on Ti electrode in a 0.4 M $Ba(OH)_2$ solution of $85^{\circ}C$ using a current pulse waveform. Both $BaTiO_3$ crystallinity and faradaic efficiency for the film formation were enhanced with the increase of cathodic current density and pulse time. Based on the surface analysis and electrochemical studies, it was suggested that, during cathodic pulsed, the surface pH increase due to the reduction of $H_2O$ accelerates the structural changes of Ti oxides which were formed during anodic cycle. Prior to experiments, Ti oxides were intentionally grown in 0.1 M $H_2SO_4$ solution and the effect of initial oxide film thickness on the $BaTiO_3$ film formation was investigated. The migration of $Ti^{+4}$ ions through the oxide film was retarded with the increase of film thickness and it was observed that the crystallization of $BaTiO_3$ was only limited to the defect area of surface oxides.

• Polymer(Korea)
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• v.34 no.6
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• pp.540-546
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• 2010

In this manuscript, in order to reduce methanol permeability and, at the same time, to increase proton conductivity THS-PSA containing silica compound, responsible for methanol permeability reduction, and sulfonic acid, responsible for proton conductivity enhancement, was applied onto PVA/PSSA-MA membranes. And in order to improve durability, the resulting membranes, PVA/PSSAMA/THS-PSA, were exposed to 500ppm F2 gas at varying reaction times. The surface-fluorinated membranes were characterized through the measurement of contact angles, thermo-gravimetric analysis, and X-ray photoelectron spectroscopy to observe the physico-chemical changes. For the evaluation of the electro-chemical changes in the resulting membranes, its water contents, ion exchange capacity, proton conductivity, and methanol permeability were measured and then compared with the commercial membrane, Nafion 115. Finally, the membran electrode assembly(MEA) was prepared and the cell voltage against the current density was measured. As fluorination time increased, the contents of F2 increased up to maximum 4.3% and to depth of 50 nm. At 60 min of fluorination, the proton conductivity was 0.036 S/cm, larger than Nafion 115 at 0.024 S/cm, and the methanol permeability was $9.26E-08cm^2/s$, less than Nafion 115 at $1.17E-06cm^2/s$.

• Progress in Medical Physics
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• v.14 no.1
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• pp.54-67
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• 2003

The voltage-dependence of N-type calcium current inactivation is U-shaped with the degree of inactivation roughly mirroring inward current. This voltage-dependence has been reported to result from a purely voltage-dependent mechanism. However, $Ca^{2＋}$-dependent inactivation of N-channels has also been reported. We have investigated the role of $Ca^{2＋}$ in N-channel inactivation by comparing the effects of $Ba^{2＋}$and $Ca^{2＋}$ on whole-cell N-current in rat superior cervical ganglion neurons. For individual cells in-activation was always larger in $Ca^{2＋}$ than in $Ba^{2＋}$ even when internal EGTA (11 mM) was replaced with BAPTA (20 mM). The inactivation vs. voltage relationship was U-shaped in both divalent cations. The enhancement of inactivation by $Ca^{2＋}$ was inversely related with the magnitude of inactivation in $Ba^{2＋}$ as if the mechanisms of inactivation were the same in both $Ba^{2＋}$ and $Ca^{2＋}$. In support of this idea we could separate fast ( ${\gamma}$ ～150 ms) and slow ( ${\gamma}$ ～ 2500 ms) components of inactivation in both $Ba^{2＋}$and $Ca^{2＋}$ using 5 sec voltage steps. Differential effects were observed on each component with $Ca^{2＋}$ enhancing the magnitude of the fast component and the speed of the slow component. The larger amplitude of fast component indicates that the more channels inactivate via this pathway with $Ca^{2＋}$ than with $Ba^{2＋}$, but the stable time constants support the idea the fast inactivation mechanism is identical in $Ba^{2＋}$and $Ca^{2＋}$. The results do not support a $Ca^{2＋}$-dependent mechanism for fast inactivation. However, the $Ca^{2＋}$-induced acceleration of the slowly inactivating component could result from a $Ca^{2＋}$-dependent process.