• Bulletin of the Korean Chemical Society
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• v.33 no.8
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• pp.2529-2534
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• 2012

Poly(3,4-ethylenedioxythiophene) coated Manganese Dioxide (PEDOT/$MnO_2$) composite electrode was fabricated by simply immersing the $MnO_2$ electrode in an acidic aqueous solution containing 3,4-ethylenedioxythiophene (EDOT) monomers. Analysis of open-circuit potential of the $MnO_2$ electrode in the solution indicates the reduction of outer surface of $MnO_2$ to dissolved $Mn^{2+}$ ions and simultaneously oxidation of EDOT monomer to PEDOT on the $MnO_2$ surface to form a PEDOT shell via a galvanic displacement reaction. Analysis of cyclic voltammograms and specific capacitance of the PEDOT/$MnO_2$, conductive carbon added $MnO_2$ and conductive carbon added PEDOT/$MnO_2$ electrodes suggests that the conductive carbon acted mainly to provide a continuous conducting path in the electrode to improve the rate capability and the PEDOT layer on $MnO_2$ acts to increase the active reaction site of $MnO_2$.

• Applied Chemistry for Engineering
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• v.27 no.4
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• pp.421-426
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• 2016

In this report, polyoxometalte (POM)-doped polypyrrole (Ppy) was deposited on surface of three-dimensional carbon cloth (CC) using an electrodeposition method and its pseudocapacitive behavior was investigated using cyclic voltammetry and galvanostatic charge-discharge. The POM-Ppy coating was thin and conformal which can be controlled by electrodeposition time. As-prepared POM-Ppy/CC was characterized using scanning electron microscope and energy-dispersive X-ray spectroscopy. The unique 3D nanocomposite structure of POM-Ppy/CC was capable of delivering excellent charge storage performances: a high areal capacitance ($561mF/cm^2$), a high rate capability (85%), and a good cycling performance (97% retention).

• Journal of Electrochemical Science and Technology
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• v.3 no.2
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• pp.72-79
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• 2012

$Li_2MnSiO_4$ was synthesized using the solid-state method under an Ar atmosphere at three different calcination temperatures (900, 950, and $1000^{\circ}C$). The optimization of the carbon coating was also carried out using various molar concentrations of adipic acid as the carbon source. The XRD pattern confirmed that the resulting $Li_2MnSiO_4$ particles exhibited an orthorhombic structure with a $Pmn2_1$ space group. Cyclic voltammetry was utilized to investigate the capacitive behavior of $Li_2MnSiO_4$ along with activated carbon (AC) in a hybrid supercapacitor with a two-electrode cell configuration. The $Li_2MnSiO_4$/AC cell exhibited a high discharge capacitance and energy density of $43.2Fg^{-1}$ and $54Whkg^{-1}$, respectively, at $1.0mAcm^{-2}$. The $Li_2MnSiO_4$/AC hybrid supercapacitor exhibited an excellent cycling stability over 1000 measured cycles with coulombic efficiency over > 99 %. Electrochemical impedance spectroscopy was conducted to corroborate the results that were obtained and described.

• Composites Research
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• v.29 no.4
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• pp.132-137
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• 2016

Based on mussel-inspired polydopamine (PDA), a novel technique to fabricate carbon nanowire (CNW) arrays is presented for a possible use of porous carbon electrode in electrochemical energy storage applications. PDA can give more porosity and nitrogen-doping effect to carbon electrodes, since it has high graphitic carbon yield characteristic and rich amine functionalities. Using such outstanding properties, the applicability of PDA for electrochemical energy storage devices was investigated. To achieve this, the decoration of the CNW arrays on carbon fiber surface was performed to increase the surface area for storage of electrical charge and the chemical active sites. Here, zinc oxide (ZnO) nanowire (NW) arrays were hydrothermally grown on the carbon fiber surface and then, PDA was coated on ZnO NWs. Finally, high temperature annealing was performed to carbonize PDA coating layers. For higher energy density, manganese oxide ($MnO_x$) nanoparticles (NPs), were deposited on the carbonized PDA NW arrays. The enlarged surface area induced by carbon nanowire arrays led to a 4.7-fold enhancement in areal capacitance compared to that of bare carbon fibers. The capacitance of nanowire-decorated electrodes reached up to $105.7mF/cm^2$, which is 59 times higher than that of pristine carbon fibers.

• Journal of Powder Materials
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• v.8 no.3
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• pp.201-206
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• 2001

$>LaMnO_3$$(La, Sr)MO_3$, and $(La, Sr)MO_3/YSZ$ gel films were deposited by spin-coating technique on scandium-doped zirconia (YSZ) substrate using the precursor solution prepared from $La(O-i-C_3H_7)_3$, $Co(CH_3COO)_2$or $Mn(O-i-C_3H_7)_2$,2-methoxyethanol, and polyethylene glycol. By heat-treating the gel films, the electrochemical cells, $(La, Sr)MnO_3{\mid}ScSZ{\mid}Pt$ were fabricated. The effect of polyethylene glycol on the microstructure evolution of $$LaCoO_3and $LaMnO_3$thin films was investigated, and NOx decomposition characteristics of the electrochemical cells were investigated at $500^{\circ}C$ to $600^{\circ}C$. By applying a direct current to the $(La, Sr)MnO_3{\mid}ScSZ{\mid}Pt$ electrochemical cell, good NOx conversion rate could be obtained relatively at low current value even if excess oxygen is included in the reaction gas mixture.

• Journal of Electrochemical Science and Technology
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• v.2 no.1
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• pp.51-56
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• 2011

We develop a new nonwoven composite separator for a safer lithium-ion battery, which is based on coating of silica ($SiO_2$) colloidal particles/styrene-butadiene rubber (SBR) binder to a poly(ethylene terephthalate) (PET) nonwoven support. The $SiO_2$ particles are interconnected by the SBR binder and closely packed in the nonwoven composite separator, which thus allows for the development of unusual porous structure, i.e. highly-connected interstitial voids formed between the $SiO_2$ particles. The PET nonwoven serves as a mechanical support that contributes to suppressing thermal shrinkage of the nonwoven composite separator. The $SiO_2$/SBR content in the nonwoven composite separators plays an important role in determining their separator properties. Porous structure, air permeability, and electrolyte wettability of the nonwoven composite separators, in comparison to a commercialized polyethylene (PE) separator, are elucidated as a function of the $SiO_2$/SBR content. Based on this understanding of the nonwoven composite separators, the effect of $SiO_2$/SBR content on the electrochemical performances such as self-discharge, discharge capacity, and discharge C-rate capability of cells assembled with the nonwoven composite separators is investigated.

• Corrosion Science and Technology
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• v.18 no.5
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• pp.155-167
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• 2019

In this study, two novel Schiff base compounds including (3-(4-Chlorophenyl isoxazole-5-yl) methanol and (3-(2,4 dichlorophenol isoxazole-5-yl) methanol as corrosion inhibitors for mild steel in 1 M hydrochloric acid solution were investigated by potentiodynamic polarization, electrochemical impedance spectroscopy (EIS), and density functional theory (DFT) computations. The results showed that the corrosion inhibition efficiency (IE) is remarkably enhanced with the growing concentration of the Schiff base inhibitors. The results from Tafel polarization and EIS methods showed that IE decreases with gradual increments of temperature. This process can be attributed to the displacement of the adsorption/desorption balance and hence to the diminution of the level of a surface coating. Also, the adsorption of two inhibitors over mild steel followed the Langmuir adsorption isotherm. Too, the results of the scanning electron microscope (SEM) images showed that the Schiff base inhibitors form an excellent protective film over mild steel and verified the results by electrochemical techniques. Additionally, the results from the experimental and those from DFT computations are in excellent accordance.

• Journal of the Korean Geotechnical Society
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• v.20 no.2
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• pp.27-36
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• 2004

The corrosion rate measurement procedure for the permanent ground anchors using polarization resistance measurements and electrochemical impedance spectroscopy is presented in this paper. The polarization resistance measurements were used to determine the correlation between corrosion rate in the steel and soil characteristics. The electrochemical impedance spectroscopy was used to predict the time dependent corrosion reaction and evaluate the different type of coating systems and the effect of cement grouting on the corrosion attack under various conditions. The results indicate that a low pH soil is a good indicator of a corrosive soil. The low pH soil condition (<5) in both clay and sand has a significant effect on the corrosion reaction of steel members in permanent found anchors. In the case of neutral and alkaline conditions beyond pH 6 in clay and sand, no consistent acceleration of corrosion was measured and the corrosion rate was constant regardless of variations of soil pH levels. Laboratory test data for porcelain clay indicate that the change of soil pH level has a small influence on the corrosion reaction in the steel member. The use of cement footing in the bonded length is sufficient to decrease the corrosion rate to a level close to 0.003∼0.01mm/y at the end of the given period. With epoxy and fusion bonded epoxy coating, the steel specimens remained unaffected and retained the original condition. It is suggested that epoxy and fusion bonded epoxy coating can provide effective protection against corrosion for a long time even in aggressive environment.

• Journal of the Korean Applied Science and Technology
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• v.30 no.1
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• pp.49-56
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• 2013

Excellent electron transport properties with enhanced light scattering ability for light harvesting have made well-ordered one dimensional $TiO_2$ nanotube(TNT) arrays an alternative candidate over $TiO_2$ nanoparticles in the area of solar energy conversion applications. The principal drawback of TNT arrays being activated only by UV light has been addressed by coupling the TNT with secondary materials which are visible light-triggered. As well as extending the absorption region of sunlight, the introduction of these foreign components is also found to influence the charge separation and electron lifetime of TNT. In this study, a novel method to fabricate the TNT-based composite photoelectrodes employing visible responsive $CuInS_2$ (CIS) nanoparticles is presented. The developed method is a square wave pulse-assisted electrochemical deposition approach to wrap the inner and outer walls of a TNT array with CIS nanoparticles. Instead of coating as a dense compact layer of CIS by a conventional non-pulsed-electrochemical deposition method, the nanoparticles pack relatively loosely to form a rough surface which increases the surface area of the composite and results in a higher degree of light scattering within the tubular channels and hence a greater chance of absorption. The excellence coverage of CIS on the tubular $TiO_2$ allows the construction of an effective heterojunction that exhibits enhanced photoelectrochemical performance.

• Journal of the Korean Society of Safety
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• v.13 no.4
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• pp.206-212
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• 1998

The water permeation in protective coatings, which may greatly influence the corrosion protective property of these coatings, was studied using the electrochemical impedance spectroscopy technique. During the absorption of water in protective coatings immersed in electrolyte solution, the change of coating capacitance with concentration of electrolyte was determined from impedance measurements. When water absorption or desorption of coatings occured by exposing the coatings to electrolyte solutions of different concentration, increase in impedance caused by desorption of water was found to be higher in the case of thicker film. The amount of water absorbed in coatings changed with concentration of electrolyte. The water taken up in coatings from the solution of lower electrolyte concentration was deserted by contact with the solution of higher concentration. The uptake of water in protective coatings varied depending on the type of coating ingredient especially binder.