• Journal of Electrochemical Science and Technology
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• v.8 no.1
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• pp.43-52
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• 2017

In this paper, for the first time, the electroanalytical study of Triethylenediamine, TEDA was done on a typically graphene modified carbon paste electrode (Gr/CPE) in pH=10.5 of phosphate buffer solutions (PBS). The surface morphology of the bare and modified electrodes was characterized by scanning electron microscopy (SEM), electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV). The electro-oxidation of TEDA was investigated at the surface of modified electrode. The results revealed that the oxidation peak current of TEDA at the surface of Gr/CPE is 2.70 times than that shown at bare-CPE. A linear calibration plot was observed in the range of 1.0 to 202.0 ppm. In this way, the detection limit was found to be 0.18 ppm. The method was then successfully applied to determination of TEDA in aqueous samples obtained from two kinds of activated carbon from the masks of war. On the other hand, density functional theory (DFT) method at B3LYP/6-311++G** level of theory and a conductor-like Polarizable Continuum Model (CPCM) was used to calculate the $pK_a$ values of TEDA. The energies of lowest unoccupied molecular orbital ($E_{LUMO}$) and highest occupied molecular orbital ($E_{HOMO}$), gap energy (${\Delta}E$) and some thermodynamic parameters such as Gibbs free energy of TEDA and its conjugate acid ($HT^+$) were calculated. The results of calculated $pK_a$ were found to be in good agreement with the experimental values.

• Journal of Ocean Engineering and Technology
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• v.22 no.3
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• pp.82-88
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• 2008

The diesel engine of the merchant ship has been aperated in severe environments more and more, because the temperature of the exhaust gas of a combustion chamber is getting higher and higher with increasing use of heavy oil of law quality, due to the significant increase in the price of oil in recent some years. As a result, the degree of wear and corrosion between exhaust valve and seat ring is more serious compared to other engine parts. Thus the repair welding of exhaust valve and seat ring is a unique method to prolong the life of the exhaust valve, from an economical point of view. In this study, the corrosion property of both weld metal and base metal was investigated using electrochemical methods such as measurement of corrosion potential, cathodic and anodic polarization curves, cyclic voltammogram, and polarization resistance in 5% H2SO4 solution. The test specimen was a part of an exhaust valve stem being welded as the base metal, using various welding methods. In all cases, the corrosion resistance as well as hardness of the weld metal zone was superior to the base metal. In particular, plasma welding showed relatively good properties for both corrosion resistance and hardness, compared to other welding methods. In the case of DC SMAW (Shielded metal arc welding), corrosion resistance of the weld metal zone was better than that of the base metal, although its hardness was almost same as the base metal.

• Bulletin of the Korean Chemical Society
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• v.28 no.1
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• pp.33-40
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• 2007

We have designed and synthesized three Zn(II)-porphyrin derivatives, such as Zn(II) porphyrin ([G-0]Zn-P1) and aryl ether-typed dendron substituted Zn(II)-porphyrin derivatives ([G-1]Zn-P1 and [G-1]Zn-P-CN1). Their chemical structures were characterized by 1H-NMR, FT-IR, UV-vis absorption, EI-mass, and MALDI-TOF mass spectroscopies. Their electrochemical properties were studied by cyclic voltammetry measurement. These Zn(II)-porphyrin derivatives have been used to fabricate dye-sensitized solar cells (DSSCs) based on solid polymeric electrolytes as dye sensitizers and their device performances were evaluated by comparing with that of a standard Ru(II) complex dye. [G-1]Zn-P-CN1 showed the enhanced power conversion efficiency than those of other porphyrin derivatives, as expected. Short-circuit photocurrent density (Jsc), open-circuit voltage (Voc), fill factor (FF), and power conversion efficiency (η) of solid-typed DSSC for [G-1]Zn-P-CN1 were evaluated to be Jsc = 11.67 mA/cm2, Voc = 0.51 V, FF = 0.46, and η = 2.76%, respectively.

• Corrosion Science and Technology
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• v.9 no.6
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• pp.310-316
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• 2010

Recently a fuel oil of the diesel engine of the marine ship is being changed with heavy oil of low quality as the oil price is higher more and more. Therefore the wear and corrosion in all parts of the engine such as cylinder liner, piston crown, spindle and seat ring of exhaust valves are predominantly increased. In particular the degree of wear and corrosion of piston crown is more seriously compared to the other parts of the engine due to operating in severe environment such as the high temperature of exhaust gas and repeating impact. Thus the repair weldment of the piston crown is a unique method to prolong the its life in a economical point of view. In this case, filler metals having a high corrosion and wear resistance such as stellite 6, Inconel 625 and Inconel 718 are mainly being used for repair welding. However it has been often happened that piston crown on the ship,s job site is being actually inevitably welded with mild filler metals. Therefore in this study, filler metals such as E4301, E4313 and E4316 were welded at SS401 steel as the base metal, and corrosion property of their weld metals in the case of post weld heat treatment or not was investigated with some electrochemical methods such as measurement of corrosion potential, cathodic and anodic polarization curves, cyclic voltammogram and polarization resistance etc. in 0.1% $H_2SO_4$ solution. Corrosion resistance of the weld metal of E4301 was better than the other weld metals in the case of no heat treatment, however, its resistance was considerably decreased with post weld heat treatment(annealing:$625^{\circ}C$, 2 hr) compared to other weld metals. The weld metals of E4313 and E4316 showed a relatively good corrosion resistance by post weld heat treatment.

• Corrosion Science and Technology
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• v.19 no.3
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• pp.109-114
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• 2020

The photo-reflectance of aluminum and AISI 304 stainless steel during cyclic immersion test in 3 wt% NaCl solution was examined in this study. Overall, corrosion was not recognized by a visual inspection or weight measurement up to 310 h. When evaluated, it was noted that the roughness of the specimens did not change significantly. However, localized corrosion, which is located at the vicinity of intermetallic precipitation of aluminum or at the grain boundary of stainless steel, was confirmed by the use of an optical microscope and scanning electron microscopy after tens of hours of utilizing the corrosion test. In this respect, an increase of the peak intensity for metallic Al after 90 h of test, and for metallic Fe after 153 h was detected from the X-ray photoelectron spectra. In this context, it was shown that from the photo-reflectance spectra, the reflection of the visible light from the tested samples was changed noticeably over the test duration. As a result, the intensity of reflected light was decreased up to 90 h ~ 153 h, and thereafter was shown to increase higher than the initial intensity before the corrosion test.

• Journal of the Korean Electrochemical Society
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• v.16 no.3
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• pp.123-128
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• 2013

Organic carbons such as methanol, ethanol, iso-propanol, methoxy ethanol, glucose are added(1, 2, 3%) in the 2000 ppm $NH_3$ and $H_3PO_4$. As vol.%. cyclic voltammetry measurement of the capacity with the addition of organic carbon, the results of $NH_3$ + 3 vol.% Methanol Addition, $H_3PO_4$ + 2 vol.% iso-propanol addition of the increase in capacity was observed. Applying to the CDI Module cell with an addiction of organic carbon is confirm that remove $NH_4$-N and $PO_4$-P in sewage. Namely, the removal efficiency of $NH_3$ was increase of 16.4% during adsorption, 30.4% during desorption and the removal efficiency of $H_3PO_4$ was increase of 63% during adsorption, 54.7% during desorption. Therefore, the result of this research is confirm that effect of the N, P removal and considered that reduction of the operating costs without removing the organic matter in the influent wastewater.

• Explosives and Blasting
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• v.32 no.3
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• pp.18-25
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• 2014

Ground vibration and noise from blasting operation are known to be the most representative constituents which can cause human and material damage. In this study, the effect of delay time on ground vibration is investigated by adopting seven different delay times in bench blasting. For each delay time, three blasting operations were performed. The prediction equations for blasting vibration are derived from 50 sets of measurement and the time theory of Langefors is evoked in the analysis of the blasting vibrations and frequencies. For the delay times of 8 ms and 28 ms, the average values of ground vibration are 5.76 cm/sec and 5.75 cm/sec, respectively, which are considerably low. Also the cyclic variation in the vibration measurements with the delay time confirms the interference effect. From the application of the measurements of blasting vibration and frequency to the time theory of Langefors, it is concluded that the optimum delay times are 8 ms and 24 ms for the test site.

• Korean Journal of Environmental Biology
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• v.22 no.3
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• pp.394-399
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• 2004

A BOD sensor was prepared with S. marcescens LSY4 and was applied for measurement of BOD values of a solution containing the standard organic pollutants. The sensor sensitivity was nearly independent of the culture time in the range of 9-16 hours. It was also affected little by the cell mass in the range of 0.22-0.75 mg $cm^{-2}$. A cyclic change in the solution pH in the range of 4-9 was accompanied by a reversible variation in the sensor sensitivity. However, the reversibility was lost when the solution pH became more acidic or more basic. Heavy metal ions lowered the sensor sensitivity, which took place more precipitously in the presence of $Cu^{2+}$ and $Ag^+$ rather than in the presence of $Zn^{2+}$ and $Cd^{2+}$. The reduction of the sensor sensitivity was significantly attenuated by loading heavy metal ion tolerance induced strain. The $Cu^{2+}$tolerance induced strain was more efficient for the attenuation than $Zn^{2+}$ and $Cd^{2+}$ tolerance induced strain.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2007.11a
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• pp.275-275
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• 2007

Two sorts of electrode composed of Sulpur/CNT/PVDF and Silver/CNT/PVDF were prepared by in situ chemical method and their electrochemical performance were evaluated by using cyclic voltammetry, impedance measurement and constant-current charge/discharge cycling technique. Also, composite electrodes were characterized by FE-SEM and BET. Raw materials such as CNT/Silver and CNT/Sulfur were mixed in ethanol, dried. These mixed materials were heated at 900 and $320^{\circ}C$ for 2hr, respectively in order to enhance contact among CNT electrodes. Electric double layer capacitor cells were fabricated using these mixed powder with polymer of PVDF. For the charging and discharging characteristics measured at scan rate of 1 mA/s, Supercapacitor of Sulphur-CNT-PVDF electrode showed a better performance than that of Ag-CNT-PVDF, which seems to be related with lower contact resistance of Sulphur-CNT-PVDF electrode.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2000.07a
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• pp.444-447
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• 2000

The spinel L $i_{1-x}$ M $n_2$ $O_4$has been synthesized by the solid-state reaction. L $i_{l-x}$M $n_2$ $O_4$which includes a mixture of LiOH . $H_2O$ and Mn $O_2$prepared by preliminary heating at 35$0^{\circ}C$ for 12hr. L $i_{l-x}$M $n_2$ $O_4$fired at temperature range from 75$0^{\circ}C$ for 48hr. The structure and the electrochemical characteristics of spinel to L $i_{1-x}$ M $n_2$ $O_4$which is fabricated by changing sintering condition from starting materials are investigated. The cyclic voltammetric measurement was performed using 3 electrode cells. Electrode specific capacity and cycle life behavior were tested in a 3.0~4.2V range at a constant current density of 0.45mA/c $m^2$. To improve the cycle performance of spinel L $i_{l-x}$M $n_2$ $O_4$as the cathode of 4V class lithium secondary batteries, spinel phases L $i_{1-x}$ M $n_2$ $O_4$were Prepared at various lithium. The results showed that discharge capacity of L $i_{l-x}$M $n_2$ $O_4$varied at lithium quantity decrease with increasing lithium add quantity. The discharge capacities of L $i_{0.925}$M $n_2$ $O_4$and LiM $n_2$ $O_4$revealed 108 and 117mAh/g, respectively.spectively.y.