• Journal of Korean Society on Water Environment
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• v.33 no.1
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• pp.34-39
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• 2017

Under a corrosive environment, electrodes that are applied in the water-treatment system need not only very high electrochemical activity for fast reactions, but also high durability for cost saving. Therefore, the fabrication condition of iridium electrodes was examined to produce a more durable iridium electrode in this study. Tantalum was selected as a binder to enhance the durability of the iridium electrode. Investigation of the weight ratio between the catalyst and the binder to improve electrochemical activity was performed. Also, to compare the effect of the different coating amounts of the catalyst, the results of CV (Cyclic Voltammetry) and EIS (Electrochemical Impedance Spectroscopy) were discussed. Furthermore, an ALT(Accelerated Lifetime Test) was designed and applied to the electrodes to determine the conditions for highly durable electrode fabrication.

• Journal of Electrochemical Science and Technology
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• v.12 no.1
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• pp.21-32
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• 2021

This study reports for the first time the application of electrocoagulation (EC) from laboratory to pilot scales for the treatment of printing wastewater, a hazardous waste whose treatment and disposal are strictly regulated. The wastewater was taken from three real printing companies with strongly varying characteristics. The treatment process was performed in the laboratory for operational optimization and then applied in the pilot scale. The weight loss of the electrode and the generation of sludge at both scales were compared. The results show that the raw wastewater should be diluted before EC treatment if its COD is higher than about 10,000 mg/L. Pilot scale removal efficiencies of COD and color were slightly lower compared to those obtained from the laboratory scale. At pilot scale, the effluent CODs removal efficiency was 81.9 - 88.9% (final concentration of 448 - 992 mg/L) and color removal efficiency was 95.8 - 98.6% (final level of 89 - 202 Pt-Co) which proved the feasibility of EC treatment as an effective pre-treatment method for printing wastewater as well as other high colored and hard-biodegradable wastewaters.

• Journal of Electrochemical Science and Technology
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• v.7 no.3
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• pp.206-213
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• 2016

Transition metal oxide-based electrodes for lithium ion batteries have recently attracted much attention because of their high theoretical capacity. Here we report the electrochemical behavior of cobalt oxide nanorods as anodes, prepared by a template-free, one-step electrochemical deposition of cobalt nanorods, followed by an oxidation process. The as-deposited cobalt has a slightly convex columnar structure, and controlled thermal oxidation produces cobalt oxides of different Co/O ratios, while the original shape is largely preserved. As an anode in a rechargeable lithium battery, the Co/O ratio has a strong effect on initial capacity and cycling stability. In particular, the one-dimensional Co@Co_xO_y core shell structure obtained from a mild heat-treatment results in superior cycling stability.

• Carbon letters
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• v.8 no.3
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• pp.207-213
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• 2007

The properties and electrochemical characteristics of anode material using pitch-coated graphite residue compounds by heat-treatment at $600^{\circ}C$ for 1 hour were investigated. The distance of layers of pitch-coated graphite residual compounds was 3.3539 ${\AA}$, which was as same as that of graphite. Its electrochemical and charge discharge characteristics were tested according to different four types of carbon material, natural graphite, pitch-coated graphite, amorphous graphite and pitch-coated graphite residual compounds, respectively. So it was shown the best charge-discharge characteristics in all of the samples. For the electrochemical and charge-discharge characteristics, although pitch-coated graphite residual compounds had different carbon contents 70% and 80%, these two samples were shown good electrochemical and charge-discharge characteristics.

• Journal of Electrochemical Science and Technology
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• v.13 no.2
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• pp.213-226
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• 2022

In the present study, the corrosion behavior of aluminum Al-7075 tempered (T-6 condition) alloy was evaluated by immersion testing and electrochemical testing in 1.75% and 3.5% NaCl environment at acidic, neutral and basic pH. The data obtained by both immersion tests and electrochemical corrosion tests (potentiodynamic polarization and electrochemical impedance spectroscopy tests) present that the corrosion rate of the alloy specimens is minimum for the pH=7 condition of the solution due to the formation of dense and well adherent thin protective oxide layer. Whereas the solutions with acidic and alkaline pH cause shift in the corrosion behavior of aluminum alloy to more active domains aggravated by the constant flux of acidic and alkaline ions (Cl^- and OH^-) in the media which anodically dissolve the Al matrix in comparison to precipitated intermetallic phases (cathodic in nature) formed due to T6 treatment. Consequently, the pitting behavior of the alloy, as observed by cyclic polarization tests, shifts to more active regions when pH of the solutions changes from neutral to alkaline environment due to localized dissolution of the matrix in alkaline environment that ingress by diffusion through the pores in the oxide film. Microscopic analysis also strengthens the results obtained by immersion corrosion testing and electrochemical corrosion testing as the study examines the corrosion behavior of this alloy under a systematic evaluation in marine environment.

• Journal of the Korean Society of Safety
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• v.13 no.2
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• pp.96-103
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• 1998

The treatment of the wastewater of Carmine-6B Process was studied using an electrochemical batch reactor with Pt-electrodes. The concentration of azo dye was exponentially decreased unto 6-37% residuum during 50 hr operations. The fractional conversion was not influenced by the initial pH value, but it was increased with increasing the rotating speed and/or temperature of the electrolyte. It was observed by the differential method of rate analysis that the rate of the oxidation reaction at anode was exponentially increased with increasing the cell voltage. The pH of the wastewater was changed from acid or alkali to neutral. The COD of the solution was increased at the beginning of the treatment, but it was decreased soon.

• Journal of Powder Materials
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• v.22 no.5
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• pp.309-314
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• 2015

Tungsten trioxide thin films are successfully synthesized by a sol-gel method using tungsten hexachloride as precursors. The structural, chemical, and optical properties of the prepared films are characterized by scanning electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, and UV-Vis spectrophotometry. The electrochemical and electrochromic properties of the films before and after heat treatment are also investigated by cyclic voltammetry, chronoamperometry, and in situ transmittance measurement system. Compared to as-prepared films, heat-treated tungsten trioxide thin films exhibit a higher electrochemical reversibility of 0.81 and superior coloration efficiency of $65.7cm^2/C$, which implies that heat treatment at an appropriate temperature is a crucial process in a sol-gel method for having a better electrochromic performance.

• Corrosion Science and Technology
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• v.7 no.3
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• pp.158-161
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• 2008

It is well known that iron is one of the most common impurity elements found in aluminum and its alloys. Iron in the aluminum forms an intermetallic compounds such as $FeAl_3$. The $FeAl_3$ particles on the aluminum surface are one of the most detrimental phases to the corrosion process and anodizing procedure for aluminum and its alloys. Trial and error surface treatment will be carried out to find the preferential and effective removal of $FeAl_3$ particles on the surfaces without dissolution of aluminum matrix around the particles. One of the preferable surface treatments for the aim of getting $FeAl_3$ free surface was an electrochemical treatment such as cathodic current density of $-2kAm^{-2}$ in a 20-30 mass% $HNO_3$ solution for the period of 300s. The corrosion characteristics of aluminum surface with $FeAl_3$ free particles are examined in a $0.1kmol/m^3$ NaCl solution. It is found that aluminum with free $FeAl_3$ particles shows higher corrosion resistance than aluminum with $FeAl_3$ particles.

• Journal of the Korean Society for Heat Treatment
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• v.35 no.6
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• pp.337-342
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• 2022

In metal cutting, water-soluble cutting oil is used for cooling the surface of the workpiece and improving the surface roughness. However, waste cutting oil contains preservatives and surfactants, and if it is discarded as it is, it has an great influence on environmental pollution. For this reason, regulations on the use of cutting oil are being stricter. Hence, the development of eco-friendly treatment technologies is required. In this study, a diamond electrode doped with boron on a niobium substrate was deposited by thermal filament chemical vapor deposition and waste cutting oil was treated using an electrochemical method. Compared to the total amount of organic carbon contained in the waste cutting oil, it was confirmed that the boron-doped diamonds developed from this study showed much better performance than electrodes that has been widely used before.

• Korean Journal of Materials Research
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• v.24 no.6
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• pp.285-292
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• 2014

Commercial activated-carbon used as the electrode material of an electric double-layer capacitor (EDLC) was posttreated with various acids and alkalis to increase its capacitance. The carbon samples prepared were then heat-treated in order to control the amount of acidic functional groups formed by the acid treatments. Coin-type EDLC cells with two symmetric carbon electrodes were assembled using the prepared carbon materials and an organic electrolyte. The electrochemical performance of the EDLC was measured by galvanostatic charge-discharge, cyclic voltammetry, and electrochemical impedance spectroscopy. Among the various activated carbons, the carbon electrodes (CSsb800) prepared by the treatments of coconutshell-based carbon activated with NaOH and $H_3BO_5$, and then heat treated at $800^{\circ}C$ under a flow of nitrogen gas, showed relatively good electrochemical performance. Although the specific-surface-area of the carbon-electrode material ($1,096m^2/g$) was less than that of pristine activated-carbon ($1,122m^2/g$), the meso-pore volume increased after the combined chemical and heat treatments. The specific capacitance of the EDLC increased from 59.6 to 74.8 F/g (26%) after those post treatments. The equivalent series resistance of EDLC using CSsb800 as electrode was much lower than that of EDLC using pristine activated carbon. Therefore, CSsb800 exhibited superior electrochemical performance at high scan rates due to its low internal resistance.