• Analytical Science and Technology
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• v.15 no.4
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• pp.388-391
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• 2002

Rancidity of a soybean oil is investigated by an electrochmical method. The redox process of the soybean oil is totally irreversible and diffusion-controlled reaction. As scan rates are faster, the anodic peak potential of the soybean oil is shifted to the positive potential and the anodic current is increased. The anodic peak potentials of the soybean oil is not rarely changed up to open-42 days in the both atmosphere and room temperature. After the open times, the anodic peak potential is largely shifted to a negative direction. This indicates the oxidation of the soybean oil becomes easier. The anodic peak current of the soybean oil is decreased gradually up to open-42 days. But after the open times, the anodic peak current increases suddenly. It must be due to the formation of a carbonyl group owing to rancidity of the soybean oil.

• Applied Chemistry for Engineering
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• v.3 no.2
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• pp.230-239
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• 1992

Nickel was used as a catalyst for the hydrogen electrode in alkaline fuel cell. The optimum electrolyte concentration and recommendable operating temperature identified from polarization curves were 6N KOH and $80^{\circ}C$, respectively. Comparing the conductivity, apparent porosity and current density at porous hydrogen electrode manufactured with various PTFE additions, the proper content of PTFE was 10wt%. Chemisorption was carried out to define the appropriate surface area. The electrode produced with 10wt% of PTFE and sintered at $340^{\circ}C$ showed more than $200mA/cm^2$ of current density. The morphology of electrode surface was investigated with SEM. Cold pressing, hot pressing, rolling and calendering methods were carried out for manufacturing the electrode, and electrochemical characteristics for each method was studied.

• Applied Chemistry for Engineering
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• v.8 no.2
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• pp.161-171
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• 1997

Anodic regeneration of PCB enchant and cathodic deposition of copper using electrochemical method has been studied. Cu(I)/Cu(II) concentration ratio as a function of Cu(I) oxidation at the anode was measured from the potential difference between platinum and Ag/AgCl/4M KCl electrodes. Chlorine gas evolution was minimized by maintaining Cu(I) concentration above a specific concentration and using non-porous graphite electrode. Dendritic copper deposition was observed at the cathode and the optimum conditions for Cu deposition was identified as the current density of $360mA/cm^2$, and copper concentration of 12 g/l. Titanium was the most effective cathode material which showed a higher current efficiency and copper recovery. The current efficiency decreased with increasing temperature, but the highest power efficiency was achieved at $50^{\circ}C$.

• Applied Chemistry for Engineering
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• v.4 no.2
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• pp.373-380
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• 1993

The preparation method of Raney nickel catalyst and the effect of promotor for the hydrogen electrode in alkaline fuel cell were investigated with electrochemical methods. The best electrode performance was observed with the Raney nickel which was obtained at $700^{\circ}C$ of sintering temperature and 60:40 of nickel:aluminum. As titanium was added for promotor, the activity of catalyst and characteristic of electrode was improved. Especially, the electrode containing 2w/o of titanium showed the maximum mass activity of 2.4A/g and its mean particle size was $5.7{\mu}m$. The resistance and capacitance of the electrode containing 2w/o of titanium, measured with AC impedance spectroscopy, were calculated to the $0.3{\Omega}cm^2$ and $0.42F/cm^2$, respectively.

• Applied Chemistry for Engineering
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• v.23 no.5
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• pp.501-504
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• 2012

In this study, etched Al electrodes with ordered arrays of pits and high aspect ratios were successively obtained using a patterned protect layer on the Al surface prepared with soft lithography method. Various methods were applied to fabricate a well ordered protect layer on the Al surface and the difference of etched Al surfaces with and without a protect layer was investigated by using SEM. It was found that the etched Al surfaces were affected by using either a protect layer or a non protect layer. As a result, the Al surface with the well ordered pits could be achieved by protect layer. However, the etched Al with nonuniform pits can be obtained without any protect layers.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2018.06a
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• pp.74-74
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• 2018

Ti-6Al-4V alloys have been widely used as orthopedic materials because of their excellent corrosion resistance and mechanical properties. However, it does not bind directly to the bone, so it requires a surface modification. This problem can be solved by nanotube and micropore formation. Plasma electrolytic oxidation (PEO) treatment for micropore, which combines high-voltage spark and electrochemical oxidation, is a new way of forming a ceramic coating on light metals such as titanium and its alloys. This method has excellent reproducibility and can easily control the shape and size of the Ti alloy. In this study, formation of bioactive surface by PEO-treatment after $2^{nd}$ ATO technique of Ti-6Al-4V alloy was invesgated by various instrument. Nanotube oxide surface structure was formed on the surface by anodic oxidation treatment in 0.8 wt.% NaF and 1M $H_3PO_4$ electrolytes. After nanotube formation, nanotube layer was removed by ultrasonic cleaning. PEO-treatment was carried out at 280V for 3 minutes in the electrolytic solution containing the bioactive substance (Mg, Zn, Mn, Sr, and Si). The surface of Ti-6Al-4V alloy was observed by field emission scanning electron microscopy (FE-SEM, S-4800 Hitachi, Japan). An energy dispersive X-ray spectrometer (EDS, Inca program, Oxford, UK) was used to analyze the spectra of physiologically active Si, Mn, Mg, Zn, and Sr ions. The PEO film formed on the Ti-6Al-4V alloy surface was characterized using an X-ray diffractometer (TF-XRD, X'pert Philips, Netherlands). It is confirmed that bioactive ions play an essential role in the normal bone growth and metabolism of the human skeletal tissues.

• Analytical Science and Technology
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• v.23 no.2
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• pp.165-171
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• 2010

Glucose oxidase ($GOD_{ox}$) immobilized biosensor was fabricated by two methods. In one of the methods, gold nanoparticles (Au-NPs) prepared by ${\gamma}$-irradiation were loaded into the poly(maleic anhydride)-grafted multi-walled carbon nanotube, PMAn-g-MWCNT electrode via physical entrapment. In the other method, the Au-NPs were prepared by electrochemical reduction of Au ions on the surface of PMAn-g-MWCNT electrode and then GODox was immobilized into the Au-NPs. The $GOD_{ox}$ immobilized biosensors were tested for electrocatalytic activities to sense glucose. The sensing range of the biosensor based on the Au-NPs physically modified PMAn-g-MWCNT electrode was from $30\;{\mu}M$ to $100\;{\mu}M$ for the glucose concentration, and the detection limit was $15\;{\mu}M$. Interferences of ascorbic acid and uric acid were below 7.6%. The physically Au deposited PMAn-g-MWCNT paste electrodes appear to be good sensor in detecting glucose.

• Journal of Hydrogen and New Energy
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• v.19 no.5
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• pp.423-429
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• 2008

This work was carried out to improve the performance of anodic electrocatalysts in direct ethanol fuel cell(DEFC). PtRu and $Pt_5Ru_4M$(M= Ni, Sn, Mo and W) electrocatalysts were prepared by using a $NaBH_4$ reduction method. Alloy crystal structure and particle size of electrocatalysts were characterized by X-ray diffraction(XRD) and transmission electron microscopy(TEM). The XRD analysis of the electrocatalysts revealed that the face-centered cubic(fcc) peaks shifted to slightly higher diffraction angles when third metals were added. Average size of the uniform particles was observed to be approximately $3{\sim}3.5\;nm$ from the TEM image. The electrochemical measurements were carried out in the solution 1M $H_2SO_4$ and 1M $C_2H_5OH$ at room temperature. Cyclic-voltammogram results showed that $Pt_5Ru_4W$ electrocatalyst exhibited much higher current density for ethanol oxidation of $2.73\;mA/cm^2$ than PtRu electrocatalyst of $0.73\;mA/cm^2$.

• Korean Chemical Engineering Research
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• v.58 no.1
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• pp.59-63
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• 2020

Radical scavenger is used to improve the durability of PEMFC polymer membrane. In this study, we investigated whether fucoidan extracted from seaweed as a radical scavenger prevents electrochemical degradation through Fenton and OCV Holding experiments. Fucoidan has an antioxidant effect, protecting the polymer membrane from hydrogen peroxide and oxygen radicals, reducing the degradation rate to 1/10. Fucoidan has been shown to be more effective than MnO₂, which is used as a radical scavenger. In the PEMFC cell, the accelerated durability evaluation method (OCV Holding) showed that fucoidan reduced the hydrogen permeability of the polymer membrane by 12% and enhanced the performance by 29.1% compared to without radical scavenger. And fucoidan was found to be more effective in the cathode side ionomer than the anode side.

• Transactions on Electrical and Electronic Materials
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• v.5 no.5
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• pp.204-207
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• 2004

In this work, we present the electrochemical properties of Al bipolar plate, which can be re-searched for the application of PEMFC system. Bulk resistance of the plate was measured with a four-point probe method. The electrical conductivity of noble metal coated Al plate was 4.40 x 10$^4$ S/cm. On the other hand, the electrical interfacial resistance of the noble metal coated Al plate valued at 0.15 mΩ-$\textrm{cm}^2$ and that of graphite was 0.26 mΩ-$\textrm{cm}^2$ under the holding pressure of 140 N/$\textrm{cm}^2$ at the applied current of 5 A. And the performance of Al bipolar plate for PEMFC was evaluated at various conditions. The single cell performance was more than 0.43 W/$\textrm{cm}^2$ (0.47 Wig) for noble metal coated Al bipolar plate at 5$0^{\circ}C$ under atmospheric pressure in external humidified hydrogen and oxygen condition. As the present results, we could show the results that the noble metal coated Al bipolar plates were favorable in the aspect of electrical properties compared with those of the commercialized resin-impregnated graphite plates.