• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.18 no.12
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• pp.1133-1138
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• 2005

In this study, we have prepared, as the pluse power source, a commercially supplied Li-ion battery with a capacity of 700 mAh and AC resistivity of 60 md at 1 kHz and nonaqeous asymmetric hybrid capacitor composed of an activated carbon cathode and MCMB anode, and have examined the electrochemical characteristics of hybrid capacitor and the pulse performances of parallel connected hybrid capacitor/Li-ion battery source. The nonaqueous asymmetric hybrid capacitors constituted with each stack number of pairs composed of the cathode, the porous separator and the anode electrode were housed in Al-laminated film cell. The 10 stacked hybrid capacitor, which was charged and discharged at a constant current at 0.25 $mA/cm^2$ between 3 and 4.3 V, has exhibited the capacitance of 108F and the lowest equivalent series resistance was 32 $m{\Omega}$ at 1 kHz. On the other hand, the enhanced run time of Li-ion battery assisted by the hybrid capacitor was obtained with increasing of current density and pulse width in Pulse mode. The best improvement, $84\;\%$ for hybrid capacitor/Li-ion battery was obtained in the condition of a 7C-rate pulse (100 msec)/0.5C-rate standby/$10\;\%$ duty cycle.

• Journal of the Korean Ceramic Society
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• v.48 no.6
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• pp.520-524
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• 2011

The properties of manufactured SOFC unit cell using decalcomania method were investigated. The decalcomania method that used in ceramics, dish, vessel and etc. was the very simple process. The SOFC unit cell manufacturer using decalcomania method is very simple process. Especially, the decalcomania method was the most suitable manufacturing method for the segmented type SOFC. The cathode, prevent diffusion layer (PDL), anode functional layer (AFL) and electrolyte were manufactured using decalcomania method on porous anode support. The sintered electrolyte at 1450$^{\circ}C$ for 2 h using decalcomania method was very dense, and the thickness was about 10 ${\mu}m$. The cathode, the PDL and the AFL were manufactured using decalcomania method and was sintered at 1250$^{\circ}C$ for 2 h, and the sintered electrodes were the porous. As a result, with humidified hydrogen used as fuel, the cell with an 15 ${\mu}m$-thick AFL exhibited maximum power densities of 0.246, 0.364, 0.504W/$cm^2$ at 700, 750, 800$^{\circ}C$, respectively.

• Proceedings of the KIEE Conference
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• 1996.07c
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• pp.1682-1684
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• 1996

Recently, because diffusion of cordless machine and smart card and so on, and concern of unpolluted materials, one are concerned with Li secondary batteries. Li secondary batteries have high voltage, high energy density and high power density, and heavy metal pollution problems are little. Mn is low price and is distributed much quantity. Therefore, we investigated $MnO_2$. In this study, we worked the electrochemical properties and charge/discharge characteristics of $MnO_2/Li$ cells. In results, the more heating temperature is high, the more ${\gamma}-phase$ varied ${\beta}-phase$, and when $MnO_2$ is heated at $320^{\circ}C$ and super-s-black 20wt% is mixed, characteristics are the best.

• Journal of the Korean Electrochemical Society
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• v.9 no.4
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• pp.170-177
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• 2006

Optimum design of flow channel in the separation plate of Proton Exchange Membrane Fuel Cell is very prerequisite to reduce concentration over potential at high current region and remove the water generated in cathode effectively. In this paper, fully 3 dimensional computational model which solves anode and cathode flow fields simultaneously is developed in order to compare the performance of fuel cell with parallel and interdigitated flow channels. Oxygen and water concentration and pressure drop are calculated and i-V performance characteristics are compared between flows with two flow channels. Results show that performance of fuel cell with interdigitated flow channel is hi민or than that with parallel flow channel at high current region because hydrogen and oxygen in interdigitated flow channel are transported to catalyst layer effectively due to strong convective transport through gas diffusion layer but pressure drop is larger than that in parallel flow channel. Therefore Trade-off between power gain and pressure loss should be considered in design of fuel cell with interdigitated flow channel.

• 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 Microscopy
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• v.34 no.1
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• pp.51-59
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• 2004

The high acceleration voltage system used in scanning electron microscope were designed and manufactured to test its stability. The Cockcroft-Walton circuits are used both in the cathode voltage up to -30 kV and in the Wehnelt cylinder of -2 kV. The operating voltage of 6 V was applied to the heating of the filament. The wave forms which are formed in the second leg of the high voltage transformer were observed in the oscilloscope with 2 V of DC input. When the high voltages were in the range between 5 kV and 12 kV, the highest value of the stabilities of the generated voltages was obtained as 0.002%.

• Journal of the Korean Ceramic Society
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• v.56 no.5
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• pp.497-505
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• 2019

Lanthanum-based transition metal cations containing perovskites have emerged as potential catalysts for the intermediate-temperature (600-800℃) oxygen reduction reaction (ORR). Here, we report a facile acetylacetone-assisted combustion route for the synthesis of nanostructured La_0.6Sr_0.4Co_0.2Fe_0.8O_3-δ (LSCF6428) cathodes for intermediate-temperature solid-oxide fuel cells (IT-SOFCs). The as-prepared powder was analyzed by thermogravimetry analysis-differential scanning calorimetry. The powder calcined at 800℃ was characterized by X-ray diffraction, scanning electrode microscopy, energy dispersive X-ray spectroscopy, and Brunauer-Emmett-Teller surface area measurements. It was found that the porosity of the air electrode significantly increased by utilizing the nanostructured LSCF6428 instead of commercial powder. The performance of a single cell fabricated with the nanostructured LSCF6428 cathode increased by 112%, from 0.4 to 0.85 W cm^-2, at 700℃. Electrochemical impedance spectroscopy showed a considerable reduction in the area-specific resistance and activation energy from 133.5 to 61.5 kJ/mol, resulting in enhanced electrocatalytic activity toward ORR and overall cell performance.

• Transactions on Electrical and Electronic Materials
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• v.16 no.3
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• pp.124-129
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• 2015

Organic electronics are the domain in which the components and circuits are made of organic materials. This new electronics help to realize electronic and optoelectronic devices on flexible substrates. In recent years, organic materials have replaced conventional semiconductors in many electronic components such as, organic light-emitting diodes (OLEDs), organic field-effect transistors (OFETs) and organic photovoltaic (OPVs). It is well known that organic light emitting diodes (OLEDs) have many advantages in comparison with inorganic light-emitting diodes LEDs. These advantages include the low price of manufacturing, large area of electroluminescent display, uniform emission and lower the requirement for power. The aim of this paper is to model polymer LEDs and OLEDs made with small molecules for studying the electrical and optical characteristics. The purpose of this modeling process is, to obtain information about the running of OLEDs, as well as, the injection and charge transport mechanisms. The first simulation structure used in this paper is a mono layer device; typically consisting of the poly (2-methoxy-5(2'-ethyl) hexoxy-phenylenevinylene) (MEH-PPV) polymer sandwiched between an anode with a high work function, usually an indium tin oxide (ITO) substrate, and a cathode with a relatively low work function, such as Al. Electrons will then be injected from the cathode and recombine with electron holes injected from the anode, emitting light. In the second structure, we replaced MEH-PPV by tris (8-hydroxyquinolinato) aluminum (Alq₃). This simulation uses, the Poole-Frenkel -like mobility model and the Langevin bimolecular recombination model as the transport and recombination mechanism. These models are enabled in ATLAS- SILVACO. To optimize OLED performance, we propose to change some parameters in this device, such as doping concentration, thickness and electrode materials.

• Proceedings of the Korean Vacuum Society Conference
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• 2000.02a
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• pp.211-211
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• 2000

Carbon nanotubes (CNTs) have been spotlighted as one of promising field emission displays(FEDs). For the first time, to authors knowledge, we have developed the 9" color CNT-FEDs with the resolution of 240x576 lines. The 9" CNT-FEDs with diode-type and triode-type structures are presented. The well-dispersed CNT paste was squeezed onto the metal-patterned cathode glass. For the anode plate, the Y2O2S:Eu, ZnS:Ag,Cl low-voltage phosphors were printed for red, green, and blue colors, respectively. The vacuum-packaged panel maintained the vacuum level of 1x10-7 Torr. The uniform moving images vacuum-packaged panel maintained the vacuum level of 1x10-7 Torr. The uniform moving images were demonstrated at 2 V/um. High brightness of 800, 200, and 150cd/m2 was observed on the green, red, and blue phosphors at V/um, respectively. Field emission characteristics of a triode-type CNT-FED were simulated using a finite element method. the resultant field strength on the cathode was modulated by gate bias and emitted electrons were focused on the anode. A relatively uniform emission image was experimentally achieved at the 800V anode. A relatively uniform emission image was experimentally achieved at the 800V anode and the 50-180 V gate biases. Energy distribution of electrons emitted from CNTs was measured using an energy analyzer. The maximum peak of energy curve corresponded to the Fermi energy level of CNTs. The whole fabrication processed of CNT-FEDs were fully scalable and reproducible. Our CNT-FEDs has demonstrated the high potential of large-area and full-color applications with very low cost fabrication and low power consumption.

• Korean Journal of Materials Research
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• v.9 no.6
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• pp.551-555
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• 1999

The deposition condition to obtain stoichiometric $Ta_2$O\ulcorner films, which is still controversial, using magnetron reactive sputtering was studied. The films were deposited by varying $O_2$gas flow rate with sputtering power and Ar gas flow rate of 200W and 60 sccm fixed. At the conditions of $O_2$ gas flow rate over 20 sccm, amorphous Tantalum oxide films with the refractive index of 2.1 and dielectric constant of 25 were deposited. Among those films, the capacitors dielectric properties of the film deposited at the condition of $O_2$ gas flow rate 50 sccm was best, the leakage current was 1$\times$10\ulcornerA/$\textrm{cm}^2$ at the electric field strength of 0.5 MC/cm and the breakdown field strength was over 2.0 MV/cm. This result could be explained from the analysis comparing with a standard sample using RBS because the composition of the film deposited at this condition was closest to the stoichiometric $Ta_2$O\ulcorner. The result of XPS analysis convinced that this film was stoichiometric $Ta_2$O\ulcorner film. A maximum cathode voltage was observed when $O_2$gas flow rate was 30 sccm. This shows that the Schiller's proposition that one can obtain stoichiometric films at the condition of maximum cathode voltage is not correct and more oxygen than that of the maximum voltage condition is necessary to deposit the stoichiometric Ta$_2$O\ulcorner films.