• Journal of the Korea institute for structural maintenance and inspection
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• v.26 no.6
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• pp.82-92
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• 2022

This study aims to investigate the effect of total electrochemical cell resistance (TECR) on electrochemical impedance (EI) measurements of reinforced concrete (RC) by electrochemical impedance spectroscopy (EIS) using a three-electrode system. A series of experimental study is performed to measure electrochemical behavior of a steel bar embedded in a concrete cube specimen, with a side length of 200 mm, in various experimental conditions. Main variables include concrete dry conditions, coupling resistance between sensing electrodes and concrete surface, and area of the counter electrode. It is demonstrated that EI values remains stable when the compliant voltage of a measuring device is sufficiently great compared to the potential drop caused by TECR of concrete specimens. It is confirmed that the effect of the coupling resistance of TECR is far more influential than other two factors (concrete dry conditions and area of the counter electrode). The results in this study can be used as a fundamental basis for development of a surface-mount sensor for corrosion monitoring of reinforced concrete structures exposed to wet-and-dry cycles under marine environment.

• Journal of the Korean Applied Science and Technology
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• v.32 no.2
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• pp.275-280
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• 2015

In this study, the current-voltage curves for stainless steel in the triethanolamine(TEA) solution was measured using the conventional three electrodes of cyclic voltammetry. Stainless steel as working electrode, Ag/AgCl electrode as reference electrode and Pt wire as counter electrode were used respectively. As a result, the C-V characteristics of stainless steel were to be for an irreversible process due to the oxidation current from cyclic voltammogram, using triethanolamine solutions. Effective diffusivity of corrosion inhibitors was decreased with increasing concentration. And the concentration of 0.5 N $NaClO_4$, $2.5{\times}10^{-3}M$ TEA solution when the corrosion inhibition effect is most great, and 1.5 N $NaClO_4$, $1.0{\times}10^{-3}M$ TEA solution, the lowest corrosion inhibition effect.

• Advances in materials Research
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• v.1 no.4
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• pp.299-310
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• 2012

This article describes the synthesis of a novel N-substituted pyrrole monomer containing an azobenzene group. The 2-[N-ethyl-N-[4-[(4-nitrophenyl) azo]-phenyl] amino] ethyl-3-chloropropionate (RedII) compound was synthesized via reaction of 4-nitro-4'-[N-ethyl-N-(2-hydroxyethyl)-amino] azobenzene (RedI) and 3-chloropropionic acid. RedII was reacted with the potassium salt of pyrrole then 2-[N-ethyl-N-[4-[(nitro phenyl) azo] phenyl] amino] ethyl-N-pyrrolyl propionate (Py-RedII) was prepared. Chemical polymerization of Py-RedII and copolymerization of Py-RedII with pyrrole carried out using $FeCl_3$. Poly (2-[N-ethyl-N-[4-[(nitro phenyl) azo] phenyl] amino] ethyl-N-pyrrolyl propionate) (PPy-RedII) was characterized by UV, IR, $^1HNMR$, $^{13}CNMR$ spectroscopies. Electropolymerization of Py-RedII and electroco-polymerization of Py-RedII and pyrrole were studied using conventional three electrodes system, Ag/AgCl reference electrode, platinum counter electrode and GC disk working electrode. Scanning electron microscopy (SEM), thermogravimetry analysis (TGA) and differential scanning calorimetry (DSC) were used for thermal and rheological studies. The TGA curve of PPy-RedII demonstrated a high thermal stability up to 200°C and its DSC thermogram showed two endothermic peaks at 88 and $122^{\circ}C$. The glass transition temperature of the polymer was found to be above the room temperature. Electrical conductivities of PPy-RedII and it's copolymer with pyrrole (PPy-RedII-co-Py) were studied by the four-probe method and produced conductivities of $7.5{\times}10^{-4}$ and $6.5{\times}10^{-3}Scm^{-1}$, respectively.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.18 no.6
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• pp.571-575
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• 2005

In order to improve the efficiency of dye-sensitized solar cell (DSSC), $TiO_2$ electrode screen-printed on transparent conducting oxide (TCO) substrate was sintered in variation with different temperature$(350\;to\;550^{\circ}C)$. $TiO_2$ electrode on fluorine doped tin oxide (FTO) glass was assembled with Pt counter electrode on FTO glass. I-V properties of DSSCs were measured under solar simulator. Also, effect of sintering temperature on surface morphology of $TiO_2$ films was investigated to understand correlation between its surface morphology and sintering temperature. Such surface morphology was observed by atomic force microscopy (AFM). Below sintering temperature of $500^{\circ}C$, efficiency of DSSCs was relatively lower due to lower open circuit voltage. Oppositely, above sintering temperature of $500^{\circ}C$, efficiency of DSSCs was relatively higher due to higher open circuit voltage. In both cases, lower fill factor (FF) was observed. However, at sintering temperature of $500^{\circ}C$, both efficiency and fill factor of DSSCs were mutually complementary, enhancing highest fill factor and efficiency. Such results can be explained in comparison of surface morphology with schematic diagram of energy states on the $TiO_2$ electrode surface. Consequently, it was considered that optimum sintering temperature of a-terpinol included $TiO_2$ paste is at $500^{\circ}C$.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2018.06a
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• pp.67-67
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• 2018

The 5xxx series aluminum alloys are recently used in not only marine system but also automotive area because of a low density material, good mechanical properties and better resistance to corrosion. However, Aluminum alloys are less resistant than the purest aluminum such as 1xxx aluminum alloy. Electrochemical anodization technique has attracted in the area of surface treatment because of a simple procedure, a low-cost efficiency than other techniques such as lithography and a large volume of productivity, and so on. Here, The relationship between the corrosion behavior and the thickness of aluminum anodic oxide have been studied. Prior to anodization, The 5052 aluminum sheets ($30{\times}20{\times}1mm$) were degreased by ultra-sonication in acetone and ethanol for 10 minutes and eletropolished in a mixture of perchloric acid and ethanol (1:4, volume ratio) under an applied potential of 20V for 60 seconds to obtain a regular surface. During anodization process, Aluminum alloy was used as a working electrode and a platinum was used as a counter electrode. The two electrodes were separated at a distance of 5cm. The applied voltage of anodization is conducted at 40V in a 0.3M oxalic acid solution at $0^{\circ}C$ with appropriate magnetic stirring. The surface morphology and the thickness of AAO films was observed with a Scanning Electron Microscopy (SEM). The corrosion behavior of all samples was evaluated by an open-circuit potential and potentio-dynamic polarization test in 3.5wt% NaCl solution. Thus, The corrosion resistance of 5052 aluminum alloy is improved by the formation of an anodized oxide film as function of increase anodization time which artificially develops on the metal surface. The detailed electrochemical behavior of aluminum 5052 alloy will be discussed in view of the surface structures modified by anodization conditions such as applied voltages, concentration of electrolyte, and temperature of electrolyte.

• Korean Journal of Materials Research
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• v.15 no.8
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• pp.528-535
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• 2005

It is inclined to increase that use of hazardous substances such as lead(Pb), mercury (Hg), cadmium(Cd) etc. are prohibited in the electronics according to environmental friendly policies of an advanced nation for protecting environment of earth. As this reasons, many researches for ensuring the reliability were proceeding in Pb free soldering process. n the flux remains on the PCB(printed circuit board) in the soldering process or the electronics exposed to corrosive environment, it becomes the reasons of breakdown or malfunction of the electronics caused by corrosion. Therefore in this studies we researched the polarization and Tafel properties of Sn40Pb and SnCu system solders based on the electrochemical theory. The experimental polarization curves were measured in distilled ionized water and 1 mole $3.5 wt\%$ NaCl electrolyte of $40^{\circ}C$, pH 7.5. Ag/AgCl and graphite were utilized by reference and counter electrodes, respectively. To observe the electrochemical reaction, polarization test was conducted from -250mV to +250mV. From the polarization curves composed of anodic and cathodic curves, we obtained Tafel slop, reversible electrode potential(Ecorr) and exchange current density((cow). In these results, we compared the corrosion rate of SnPb and SnCu solders.

• Journal of the Korean Applied Science and Technology
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• v.31 no.1
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• pp.66-73
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• 2014

In this work, the current-voltage curves for stainless steel in the ethanolamine solution containing alkyl group were measured using the conventional three electrodes of cyclic voltammetry. Stainless steel as working electrode, Ag/AgCl electrode as reference electrode and Pt wire as counter electrode were used respectively. As a result, the C-V characteristics of stainless steel were to be for an irreversible process due to the oxidation current from cyclic voltammogram, using N-ethylethanolamine and N,N-dimethylethanolamine solutions. Effective diffusivity of corrosion inhibitors was decreased with increasing concentration. It was found from SEM images of the metal that the electrolyte (specific name ?)(0.5 N) as corrosion inhibitor was added into a N, N-diethylethanolamine solution ($1.0{\times}10^{-3}M$) containing copper and nickel, the corrosion inhibiting effect was enhanced.

• Journal of Industrial and Engineering Chemistry
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• v.68
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• pp.161-167
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• 2018

In this study, transition metal coated carbon nanofibers (CNFs) were synthesized and applied as anode materials of Li secondary batteries. CNFs/Ni foam was immersed into 0.01 M transition metal solutions after growing CNFs on Ni foam via chemical vapor deposition (CVD) method. Transition metal coated CNFs/Ni foam was dried in an oven at $80^{\circ}C$. Morphologies, compositions, and crystal quality of CNFs-transition metal composites were characterized by scanning electron microscopy (SEM), Raman spectroscopy (Raman), and X-ray photoelectron spectroscopy (XPS), respectively. Electrochemical characteristics of CNFs-transition metal composites as anodes of Li secondary batteries were investigated using a three-electrode cell. Transition metal/CNFs/Ni foam was directly employed as a working electrode without any binder. Lithium foil was used as both counter and reference electrodes while 1 M $LiClO_4$ was employed as the electrolyte after it was dissolved in a mixture of propylene carbonate:ethylene carbonate (PC:EC) at 1:1 volume ratio. Galvanostatic charge/discharge cycling and cyclic voltammetry measurements were taken at room temperature using a battery tester. In particular, the capacity of the synthesized CNFs-Fe was improved compared to that of CNFs. After 30 cycles, the capacity of CNFs-Fe was increased by 78%. Among four transition metals of Fe, Cu, Co and Ni coated on carbon nanofibers, the retention rate of CNFs-Fe was the highest at 41%. The initial capacity of CNFs-Fe with 670 mAh/g was reduced to 275 mAh/g after 30 cycles.

• Journal of Korean Society on Water Environment
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• v.35 no.5
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• pp.418-424
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• 2019

In this study, $TiO_2$ nanotubes with different morphologies were prepared in the electrolyte consisting of ethylene glycol, ammonium fluoride($NH_4F$), and deionized water($H_2O$) by controlling the voltage and time in the anodization method. Thicknesses and pore sizes of these $TiO_2$ nanotubes were measured to interpret the relationship between anodization conditions and $TiO_2$ nanotube morphologies. Element contents in the $TiO_2$ nanotubes were detected for further analysis of $TiO_2$ nanotube characteristics. Photoelectrolyticdecolorization efficiencies of the $TiO_2$ nanotube plates with various morphologies were tested to clarify the morphology that a highly active $TiO_2$ nanotube plate should have. Influences of applied voltage in photoelectrolysis processes and sodium sulfate($Na_2SO_4$) concentration in wastewater on the decolorization efficiency were also studied. To save the equipment investment cost in photoelectrolysis methods, a two-photoelectrode system that uses the $TiO_2$ nanotube plates as photoanode and photocathode instead of adding other counter electrodes was studied. Compared with single-photoelectrode system that uses the $TiO_2$ nanotube plate as photoanode and titanium plate as cathode on the view of the treatment of dye wastewater containing different amounts of salt. As a result, a considerably suitable voltage was strictly needed for enhancing the photoelectrolyticdecolorization effect of the two-photoelectrode system but if salts exist in wastewater, an excellent increase in the decolorization efficiency can be obtained.

• Journal of Sensor Science and Technology
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• v.6 no.1
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• pp.24-34
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• 1997

In this study, two different types of complementary electrochromic devices using amorphous $WO_{3}$ films as a working electrode, $V_{2}O_{5}$ film and NiO film as counter electrodes respectively were investigated. For the devices using amorphous and crystalline $V_{2}O_{5}$ films of $100{\sim}150nm$ thickness with $ITO/WO_{3}/LiClO_{4}-PC/V_{2}O_{5}/ITO$ structure, an optical modulation of $50{\sim}60%$ were obtained at a potential range of $1{\sim}2V$. It has been shown that transmittance and reflectance of light could be electrically controlled by low applied voltage. For the devices with $ITO/WO_{3}/LiClO_{4}-PC/NiO/ITO$ structure in which NiO film was deposited by a RF reactive sputtering, the optical modulation in visible light region (${\lambda}=550nm$) and in near infrared light region (${\lambda}=850nm$) were 25% and 30%, respectively.