• Journal of the Korean Society for Precision Engineering
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• v.29 no.3
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• pp.302-306
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• 2012

Bacterial cellulose based actuator with large displacement was developed for biomimetic robots. Bacterial cellulose has 3D nanostructure with high porosity which was composed of the nanofibers. Freeze dried bacterial cellulose was dipped into ionic liquid solution such as 1-butyl-3-methylimidazolium(BMIMCl) to enhance the actuation performance due to increase the ionexchange capacity and ionic conductivity. And Poly(3,4-ethylenedioxythiophene)-poly (styrnenesulfonate)(PEDOT:PSS) was used for the electrodes of both side of bacterial cellulose actuator by dipping and drying method. The FT-IR and XRD were conducted to examine the electrochemical changes of developed bacterial cellulose actuator. The biomimetic caudal fin was designed using bacterial cellulose actuator and PDMS to verify the possibility for biomimetic robot. The step and harmonic response were conducted to evaluate the performance of developed biomimetic actuator.

• Transactions of the Korean hydrogen and new energy society
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• v.27 no.5
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• pp.471-477
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• 2016

In this research, the Ir supported $TiO_2$ (P25) catalyst was prepared by precipitation method for oxygen evolution reaction. The $Ir/TiO_2$ catalyst was synthesised by reduction reaction using reducing agent. Physiochemical characterizations of synthesized $Ir/TiO_2$ catalyst was studied by means of SEM, EDS mapping, TEM and XRD. The Electrochemical characterizations were tested by using the technique of CV and LSV by RDE and Potentiostat. Physicochemical properties were characterized with XRD where Iridium metal morphology and Ir(111) and Ir(222) peaks were founded. $Ir0.2Ru0.8O_2$ exhibited higher OER activity than $Ir0.5Ru0.5O_2$ followed by $Ir/TiO_2$ and $IrO_2$.

• Journal of the Korean institute of surface engineering
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• v.46 no.5
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• pp.229-233
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• 2013

The small punch(SP) tests that can be applied to high strength sheet steel in automobile were carried out to evaluate the behavior of hydrogen embrittlement of DP sheet steels. In order to charge hydrogen at DP sheet steels, DP sheet steels were treated by the electrochemical hydrogen charging method under the charging conditions of current densities of 100, 150 and 200 $mA/cm^2$ for charging times of 5, 10, 25 and 50 hrs. Respectively, After hydrogen charging with experimental conditions, SP tests were performed. From the SP results, the correlations between the variation of bulb diameters and bulb heights with the hydrogen charging conditions were analysed. It was shown that the variation of bulb diameters were not significant with the hydrogen embrittlement due to the amounts of hydrogen charging. On the other hand, the bulb heights were observed to decrease with increasing hydrogen contents. It was thought that these results of the variation of bulb shapes after SP tests would be estimated as the index of evaluation of hydrogen embrittlement.

• Korean Journal of Metals and Materials
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• v.47 no.7
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• pp.454-459
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• 2009

In order to commercialize Polymer Electrolyte Fuel Cell (PEFC), the cathode catalyst such as Platinum supported Carbon (Pt/C) need to have a high activity of Oxygen Reduction Reaction (ORR). In this study, the 20% Pt/C was synthesized using the chemical reduction method while the crystallinity of Platinum (Pt) particles were controlled under heat treatment conditions. The activity of synthesized Pt catalysts was evaluated using electrochemical measurement. Compared with the $i_{ORR}$ at 0.8 V of 20% Pt/C heat-treated at $500^{\circ}C$ and the 20% Pt/C that were not heated and commercial 20% Pt/C, the $i_{ORR}$ at 0.8 V of 20% Pt/C heattreated at $500^{\circ}C$ was 9.5 and 1.7 times higher than those of the 20% Pt/C and commercial 20% Pt/C that were not heated. It was considered that the crystallinity and particle size affect the ORR activity of the Pt/C catalysts.

• Journal of Powder Materials
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• v.30 no.4
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• pp.310-317
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• 2023

Small-film-type ion sensors are garnering considerable interest in the fields of wearable healthcare and home-based monitoring systems. The performance of these sensors primarily relies on electrode capacitance, often employing nanocomposite materials composed of nano- and sub-micrometer particles. Traditional techniques for enhancing capacitance involve the creation of nanoparticles on film electrodes, which require cost-intensive and complex chemical synthesis processes, followed by additional coating optimization. In this study, we introduce a simple one-step electrochemical method for fabricating gold nanoparticles on a carbon nanotube (Au NP-CNT) electrode surface through cyclic voltammetry deposition. Furthermore, we assess the improvement in capacitance by distinguishing between the electrical double-layer capacitance and diffusion-controlled capacitance, thereby clarifying the principles underpinning the material design. The Au NP-CNT electrode maintains its stability and sensitivity for up to 50 d, signifying its potential for advanced ion sensing. Additionally, integration with a mobile wireless data system highlights the versatility of the sensor for health applications.

• Corrosion Science and Technology
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• v.22 no.2
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• pp.99-107
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• 2023

Layered silicate clay montmorillonite (MMT) has been used in nanocomposite coating to improve corrosion protection by reinforcing the barrier property. The better dispersion of MMT in the coating produces a higher barrier effect. Pretreatment with MMT could favor the delamination of clay platelets, facilitating MMT dispersion in the coating. In the present work, a montmorillonite/silica (MMT/Si) composite was prepared by the in situ sol-gel method. x-ray diffraction measurements and field-emission scanning electron microscopy observations showed silica crystal formation and increased basal spacing between the MMT platelets. Composite MMT/Si particles were introduced in an epoxy resin to reinforce the corrosion protection of the coating applied on the AA2024 surface. Electrochemical impedance spectroscopy (EIS) was performed to characterize the protective property of the coating. The results demonstrated the high barrier effect of the coating containing 5 wt% of MMT/Si. Adhesion evaluation after a salt spray test exhibited a high adherence to the epoxy coating containing MMT/Si.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.36 no.2
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• pp.164-169
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• 2023

Nano Pt particles were dispersed on carbon-based supports by a polyol process for a catalyst application in a polymer electrolyte fuel cell. We tried to optimize the effect of pH on the electrostatic forces between the support and the Pt colloids. We investigated the relationship among the surface charges on the carbon support, the solution pH, and the concentration of a glycolate, and the Pt particle size. The produced catalyst with nano Pt particles on the support was evaluated by the long-term cyclic voltammetry (CV) performance test and compared with the results from a commercial catalyst. Our experimental results reveal that the pH-control can modify the particle size distribution and the dispersion of the nano Pt particles. This resulted in a cost-effective method for the synthesis of highly Pt loaded Pt/C catalysts for fuel cells better than a commercial catalyst system.

• Nuclear Engineering and Technology
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• v.55 no.4
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• pp.1518-1527
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• 2023

A method was proposed for in-situ evaluating the thickness and resistivity of the oxide/hydroxide film formed on the surface of aluminum alloy exposed to sump water formed in the containment after a loss-of-coolant accident. The evaluation entailed fitting a model for the film impedance, which has film thickness and other variables describing the resistivity profile of the film along its thickness direction as fitting parameters, to the practically measured electrochemical impedance data. The obtained resistivity profiles implied that the films formed at pHs_25℃ 7, 8, 9, 10, and 11 all had a duplex structure; compared to the outer layer in contact with the solution, the inner layer of the film had a much higher resistivity and was inferred to be denser and provide most of the protectiveness of the film. Both the thickness and the total resistance of the film decreased with the increasing solution pH_25℃, suggesting that the films formed in more alkaline solutions had less protectiveness against corrosion, consistent with the increasing aluminum alloy corrosion rates previously identified.

• Journal of the Microelectronics and Packaging Society
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• v.29 no.4
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• pp.77-82
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• 2022

During etching process of PCB, the electroplated copper line and seed layer copper have different etching rates and it caused the over etching of copper line as well as undercut of lines. In this research, the effects of etchants composition on copper etching characteristics were investigated. The optimum concentration of hydrogen peroxide and sulfuric acid of etchants were obtained using polarization and OCV (open circuit voltage) analysis for both rolled copper and electroplated copper. The inhibiting effects of different inhibitors were investigated using OCV and ZRA (zero resistance ammeter) analysis. The galvanic current between electroplated copper and seed layer copper were measured using ZRA method. Inhibitors for least galvanic current could be chosen based on galvanic coupling in ZRA analysis.

• Korean Chemical Engineering Research
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• v.57 no.3
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• pp.344-350
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• 2019

Durability is very important for the commercialization of membranes and electrode assemblies (MEA) developed for proton exchange membrane fuel cells (PEMFC). Durability evaluation of stationary PEMFC MEA has a problem that the voltage change rate should be measured for a long time over 1000 hours under constant current conditions. In this study, the electrochemical durability evaluation protocol of membranes (OCV holding method) using to vehicle MEAs was applied to the stationary MEA for the purpose of shortening the durability evaluation time. After operation of the stationary and automobile MEA for 168 hours under conditions of OCV, cathode oxygen, $90^{\circ}C$ and relative humidity of 30%, I-V, LSV, CV, impedance and FER were measured and compared. When the hydrogen permeability, OCV change, ionic conductivity, and fluorine flow rate, which represent the durability of the membrane after degradation, were all examined, it was shown that durability of stationary MEA membrane was better than that of vehicles MEA membrane. In addition, the electrode degradation of stationary MEA was smaller than that of vehicles MEA after degradation operation. It was possible to evaluate in a short time using automotive protocol that the durability of stationary MEA was superior that of vehicle MEA in terms of membrane and the electrode.