• Proceedings of the KIEE Conference
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• 2000.07c
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• pp.1518-1520
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• 2000

Amorphous $MnO_{2}{\cdot}nH_{2}O$ in 1M KOH aqueous electrolyte proves to be an excellent electrode for a faradic electrochemical capacitor cycled between -0.5 and +1.0 versus Ag/AgCl. The effect of thermal treatment on the crystalinity, particle structure, and corresponding electrochemical properties of the resulting xerogel remained amorphous as Mn(OH)2 up to 160$^{\circ}C$. With an increase in the temperature above 200$^{\circ}C$, both the surface area and pore volume decreased sharply, because the amorphous Mn(OH)2 decomposed to form MnO that was subsequently oxidized to form crystalline Mn3O4. In addition, the changes in the crystallinity, and particle structure all had significant but coupled effects on the electrochemical properties of the xerogels. A maximum capacitance of 160.6F/g was obtained for an electrode prepared with the MnOx Xerogel calcined at 150$^{\circ}C$, which was consistent with the maxima exhibited in both the surface area and pore volume. This capacitance was attributed solely to a surface redox mechanism.

• Korean Journal of Materials Research
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• v.21 no.6
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• pp.309-313
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• 2011

The power capacitors used as vehicle inverters must have a small size, high capacitance, high voltage, fast response and wide operating temperature. Our thin film capacitor was fabricated by alumina layers as a dielectric material and a metal electrode instead of a liquid electrolyte in an aluminum electrolytic capacitor. We analyzed the micro structures and the electrical properties of the thin film capacitors fabricated by nano-channel alumina and metal electrodes. The metal electrode was filled into the alumina nano-channel by electroless nickel plating with polyethylene glycol and a palladium catalyst. The spherical metals were formed inside the alumina nano pores. The breakdown voltage and leakage current increased by the chemical reaction of the alumina layer and $PdCl_2$ solution. The thickness of the electroless plated nickel layer was 300 nm. We observed the nano pores in the interface between the alumina layer and the metal electrode. The alumina capacitors with nickel electrodes had a capacitance density of 100 $nF/cm^2$, dielectric loss of 0.01, breakdown voltage of 0.7MV/cm and leakage current of $10^4{\mu}A$.

• Membrane Journal
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• v.27 no.6
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• pp.477-486
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• 2017

Hydrogen is one of energy storage systems, which could be transfer from electric energy to chemical energy or from chemical energy to electric energy, and is as an energy carrier. Water electrolysis is being investigating as one of the hydrogen production methods. Recently, water electrolysis receive attention for the element technology in PTG (power to gas) and PTL (power to liquid) system. In this paper, it was explained the principle and type for the water electrolysis, and recent research review for the alkaline water electrolysis.

• Transactions of the Korean hydrogen and new energy society
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• v.23 no.5
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• pp.513-520
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• 2012

The electrochemical reaction of refuse derived fuel (RDF) and refuse plastic/paper fuel (RPF) was investigated in the direct carbon fuel cell (DCFC) system. The open circuit voltage (OCV) of RPF was higher than RDF and other coals because of its thermal reactive characteristic under carbon dioxide. The thermal reactivity of fuels was investigated by thermogravimetric analysis method. and the reaction rate of RPF was higher than other fuels. The behavior of all sample's potential was analogous in the beginning region of electrochemical reactions due to similar functional groups on the surface of fuels analyzed by X-ray Photoelectron Spectroscopy experiments. The potential level of RDF and RPF decreased rapidly comparing to coals in the next of the electrochemical reaction because the surface area and pore volume investigated by nitrogen gas adsorption tests were smaller than coals. This characteristic signifies the contact surface between electrolyte and fuel is restricted. The potential of fuels was maintained to the high current density region over 40 $mA/cm^2$ by total carbon component. The maximum power density of RDF and RPF reached up to 45~70% comparing to coal. The obvious improvement of maximum power density by increasing operating temperature was observed in both refuse fuels.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.12 no.1
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• pp.44-49
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• 1999

In this study, microstructure and electrical conductivity of {(G $d_2$ $O_3$)$_{0.75}$( $Y_2$ $O_3$)$_{0.25}$}$_{x}$ (Ce $O_2$)$_{1-x}$ (0.01$\leq$x$\leq$0.25) was investigated as a function of composition x. GYO addition(x) increased the bulk density and G $d_2$ $O_3$ was found to be monoclinic at x>0.15. From the change of the lattice parameter with the addition(x), GYO solution limit for ceria was exceeded in the range of x=0.05 to 0.09. Thermal expansion coefficient(15~17$\times$10$^{-6}$ $^{\circ}C$) of GYC samples at x=0.01 to 0.07 was higher in value than that of 8YSZ(10.8$\times$10$^{-6}$ $^{\circ}C$). The electrical conductivity of GYC samples at x=0.05 showed the maximum(0.01S/cm) in value at 1073K which was 2 times higher than that of 8YSZ. The activation energy for the electrical conduction was determined to be 0.60eV in the temperature range of 1073K.3K..3K.

• Journal of the Korean Electrochemical Society
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• v.2 no.4
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• pp.202-208
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• 1999

Composite cathodes of $50/50\;vol\%$ LSM-YSZ $(La_{-x}Sr_xMnO_3-yttria\;stabilized\;zirconia)$ were deposited onto dense YSZ electrolytes by colloidal deposition technique. The cathode characteristics were then examined by scanning electron microscopy (SEM) and studied by ac-impedance spectroscopy (IS). The conditioning effects on LSM-YSZ cathodes were seen and remedies for these effects were noted in order to improve the performance of a solid oxide fuel cell (SOFC). The effects of temperature on impedance, surface contamination on cathode bonding to YSZ electrolyte, changing Pt paste, aerosol spray technique applied to curved surface on microstructure and cell to cell variability were solved by testing at $900^{\circ}C$, sanding the YSZ surface, using only one batch of Pt paste, using flat YSZ plates and using consistent procedures and techniques, respectively. And then, reproducible impedance spectra were confirmed by using the improved cell and the typical spectra measured for an (air)LSM-YSZ/YSZ/LSM-YSZ(air) cell at $900^{\circ}C$ were composed of two depressed arcs. Impedance characteristics of the LSM-YSZ cathodes were also affected by experimental conditions such as catalytic interlayer, composite cathode compositions and applied current.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2000.11a
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• pp.1-2
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• 2000

In chip plating, several parameters must be taken into consideration. Current density, solution concentration, pH, solution temperature, components volume, chip and media ratio, barrel geometrical shape were most likely found to have an effect to the process yields. The 3 types of barrels utilized in chip plating industry are the onventional rotating barrel, vibrational barrel(vibarrel), and the centrifugal type. Conventional rotating barrel is a close type and is commonly used. The components inside the barrel are circulated by the barrel's rotation at a horizontal axis. Process yield has known to have higher thickness deviation. The vibrational barrel is an open type which offers a wide exposure to electrolyte resulting to a stable thickness deviation. It rotates in a vertical axis coupled with multi-vibration action to facilitate mixed up and easy transportation of components. The centrifugal barrel has its plated work centrifugally compacted against the cathode ring for superior electrical contact with simultaneous rotary motion. This experiment has determined the effect of barrel vibration intensity to the plating thickness distribution. The procedures carried out in the experiment involved the overall plating process., cleaning, rinse, Nickel plating, Tin-Lead plating. Plating time was adjusted to meet the required specification. All other parameters were maintained constant. Two trials were performed to confirm the consistency of the result. The thickness data of the experiment conducted showed thatbthe average mean value obtained from higher vibrational intensity is nearer to the standard mean. The distribution curve shown has a narrower specification limits and it has a reduced variation around the target value. Generally, intensity control in vi-barrel facilitates mixed up and easy transportation of components. However, it is desirable to maintain an optimum vibration intensity to prevent solution intrusion into the chips' internal electrode. A cathodic reaction can occur in the interface of the external and internal electrode. 2H20 + e $\rightarrow$M/TEX> 20H + H2.. Hydrogen can penetrate into the body and create pressure which can cause cracks. At high intensity, the chip's motion becomes stronger, its contact between each other is delayed and so plating action is being controlled. However, the strong impact created by its collision can damage the external electrode's structure there by resulting to bad plating condition.

• Journal of the Korean institute of surface engineering
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• v.49 no.2
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• pp.159-165
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• 2016

The hydrogen has been recognized as a clean, nonpolluting and unlimited energy source that can solve fossil fuel depletion and environmental pollution problems at the same time. Water electrolysis has been the most attractive technology in a way to produce hydrogen because it does not emit any pollutants compared to other method such as natural gas steam reforming and coal gasification etc. In order to improve efficiency and durability of the water electrolysis, comprehensive studies for highly active and stable electrocatalysts have been performed. The platinum group metal (PGM; Pt, Ru, Pd, Rh, etc.) electrocatalysts indicated a higher activity and stability compared with other transition metals in harsh condition such as acid solution. It is necessary to develop inexpensive non-noble metal catalysts such as transition metal oxides because the PGM catalysts is expensive materials with insufficient it's reserves. The optimization of operating parameter and the components is also important factor to develop an efficient water electrolysis cell. In this study, we optimized the operating parameter and components such as the type of AEM and density of gas diffusion layer (GDL) and the temperature/concentration of the electrolyte solution for the anion exchange membrane water electrolysis cell (AEMWEC) with the transition metal oxide alloy anode and cathode electrocatalysts. The maximum current density was $345.8mA/cm^2$ with parameter and component optimization.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.27 no.12
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• pp.866-870
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• 2014

In solid oxide fuel cell system, yttria-stabilized zirconia is generally adopted as the electrolyte, which has high strength and superior oxygen ion conductivity, and the air electrode and the fuel electrode are attached to this. Recently, new structure of 'layered planar SOFC module' was suggested to solve the reliability problem due to the high temperature stability of a sealing agent and a binding material. In this study to materialize the air electrode in a layered planar SOFC module, the LSM ink was coated to form homogeneous electrode in the channel after the ink preparation. As the porosity control agent, PMMA or active carbon powder was adopted with use of a commercial dispersant in ethanol. The optimal amounts of both the porosity control agents and the dispersant were determined. Four (4) vol% of the dispersant for the LSM-PMMA case and 15 vol% for LSM-carbon powder showed the lowest viscosities respectively to indicate the best dispersed states of the slurries. With PMMA and carbon powder, sintered LSM ink shows the relatively homogeneous distributions of pores and with increases of the agents, the porosities increased in both cases. From this, it can be thought that the amount of the PMMA or carbon powder could be used to control the porosity of the LSM ink.

• Macromolecular Research
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• v.16 no.6
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• pp.549-554
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• 2008

Proton conducting crosslinked membranes were prepared using polymer blends of polystyrene-b-poly(hydroxyethyl acrylate)-b-poly(styrene sulfonic acid) (PS-b-PHEA-b-PSSA) and poly(vinyl alcohol) (PVA). PS-b-PHEA-b-PSSA triblock copolymer at 28:21:51 wt% was synthesized sequentially using atom transfer radical polymerization (ATRP). FT-IR spectroscopy showed that after thermal ($120^{\circ}C$, 2 h) and chemical (sulfosuccinic acid, SA) treatments of the membranes, the middle PHEA block of the triblock copolymer was crosslinked with PVA through an esterification reaction between the -OH group of the membrane and the -COOH group of SA. The ion exchange capacity (IEC) decreased from 1.56 to 0.61 meq/g with increasing amount of PVA. Therefore, the proton conductivity at room temperature decreased from 0.044 to 0.018 S/cm. However, the introduction of PVA resulted in a decrease in water uptake from 87.0 to 44.3%, providing good mechanical properties applicable to the membrane electrode assembly (MEA) of fuel cells. Transmission electron microscopy (TEM) showed that the membrane was microphase-separated with a nanometer range with good connectivity of the $SO_3H$ ionic aggregates. The power density of a single $H_2/O_2$ fuel cell system using the membrane with 50 wt% PVA was $230\;mW/cm^2$ at $70^{\circ}C$ with a relative humidity of 100%. Thermogravimetric analysis (TGA) also showed a decrease in the thermal stability of the membranes with increasing PVA concentration.