• Journal of the Korean institute of surface engineering
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• v.30 no.5
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• pp.333-346
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• 1997

Plasma spray processes for functional coatings of tubular SOFC ( Soild oxide Fuel Cell).consisting of air electrode, oxide electrolyte, an fuel electrode, are optimized by fully saturated fractional factorial testing. Material and electric characteristics of each coating are analtsed by the implementation of SEM and optical microscope for evaluating microstructure and porosity, X-ray diffraction method for investigating compositional change between raw powder and sprayed coating, and Van der Pauw method for measuring electrical conductivity. LSM ($La_{0.65}Sr_{0.35}MnO_3$air electrode and Ni-YSL fuel electrode coatings have porosities of around 23~30% sufficient for effective fuel and oxidant gas supply to electrochemical reaction interfaces and electrical conductivities of around 90 S/cm and 1000 S/cm, respectively, enough for acting as current collecting electrodes. YSZ($ZrO_2-8mol%Y_2O_3$) electrolyte film has a high ionic conductivities of 0.05~0.07 S/cm at $1000^{\circ}C$ in air atmosphere, but appears to be somewhat too porous to reduce the thickness. for enhancing the cell efficiency. A unit tubular SOFC has beem fabricated by the optimized plasma spray processes for each functional coating and the cell. Its electrochemical chracteristics are investigated by measuring voltage-current and power density with variation of operationg temperature, radio of fuel to air gas flowrates, and total gas flowrate of reactants.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.39 no.6
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• pp.505-511
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• 2015

Solid oxide fuel cell operate at high temperature ($800{\sim}1000^{\circ}C$). High temperature have an advantage of system efficiency, but a weak durability. In this study, linear state space controller is designed to handle the temperature of solid oxide fuel cell system for proper thermal management. System model is developed under simulink environment with Thermolib$^{(R)}$. Since the thermally optimal system integration improves efficiency, very complicated thermal integration approach is selected for system integration. It shows that temperature response of fuel cell stack and catalytic burner are operated at severe non-linearity. To control non-linear temperature response of SOFC system, gain scheduled linear quadratic regulator is designed. Results shows that the temperature response of stack and catalytic burner follows the command over whole ranges of operations.

• Journal of the Korean Ceramic Society
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• v.44 no.5 s.300
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• pp.148-150
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• 2007

A process to synthesize $La_{0.8}Sr_{0.2}CrO_3$ (LSC), which is a promising material for use as a separator in a soild oxide fuel cell, is investigated in this study. LSC powders without secondary Phases could be synthesized with ultrasonic spray pyrolysis and a heat treatment at $1200^{\circ}C$ for 20 h; however, it showed an average diameter of $0.6{\mu}m$ with a wide particle size distribution. On the other hand, LSC powders synthesized with spray pyrolysis at $800^{\circ}C$, heat-treated at $900^{\circ}C$ for 5 h, ball-milled and finally heat-treated again at $1200^{\circ}C$ for 20 h showed a smaller average diameter of $0.3{\mu}m$ and narrower size distribution. Very few particles above $0.5{\mu}m$ were found. Thus, a proper combination of the heat treatment and milling process after spray pyrolysis it determined to be very important in synthesizing fine and uniform LSC perovskite powders.

• Journal of Korean Society of Environmental Engineers
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• v.28 no.12
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• pp.1347-1351
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• 2006

It was tried to utilize organic waste sludge from wastewater treatment plant as a starting material to produce a solid fuel by vacuum flying. The effects of decompression levels, frying time and temperature on the calorific value and moisture of vacuum fried sludge were systematically investigated. Dewatered raw sludge used in this study had a moisture of 81.1% and calorific value of 2,930 kcal/kg. Based on the experimental observation, it was identified that the decompression level and frying time have the greatest influence on the calorific value of vacuum fried sludge. Moistures of the fried sludge at $180^{\circ}C$ for 25 min in 760 mmHg, 684 mmHg and 630 mmHg were 32.4%, 14.2% and 11.6%, respectively. Calorific values of the vacuum fried sludge at $140^{\circ}C$ for 15 min and 25 min were 5,400 kcal/kg and 5,540 kcal/kg in 684 mmHg and 5,520 kcal/kg and 5,660 kcal/kg in 630 mmHg, respectively.

• Nuclear Engineering and Technology
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• v.23 no.4
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• pp.444-455
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• 1991

An accurate and fast running NEDAR model for calculating radial power profile throughout fuel life in both solid and annular pellets for existing and advanced CANDU-PHWR-fuel was developed in this work. This model contains resultant flux depression equations and neutron depression data tables which have been developed for CANDU-PHWR fuel of pellet with the diameter 8.0 to 19.5 mm and enrichment 0.71-6.0 wt % U-235, over a bumup range of 0 to 840 MWh /kgU (35000 MWD/T). In order to obtain the neutron flux distribution in the fuel pellet, the CE-HAMMER physics code was run for a neutron flux spectrum appropriate to a CANDU-PHWR to give predictions of radial power profile for several ranges of fuel design parameters. The results, which were calculated by the CE-HAMMER physics code, were fitted to an equation which is solved in terms of Bessel and exponential functions in order to obtain the parameters, $textsc{k}$, $\beta$ and λ in the resultant equation. The present NEDAR model produce a radial profile which, when normalized to unity at the pellet surface, is slightly higher than the profile of the original ELESIM data table. The predictions of the fission gas release by KAFEPA-NEDAR are in slightly better agreement with the experiments than those of ELESIM. The NEDAR model described in this study has been shown to provide an effective, reliable, and accurate method for determining radial power profiles in CANDU-PHWR fuel rods without incurring a significant increase in computing time.

• Journal of the Korean Ceramic Society
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• v.35 no.9
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• pp.981-987
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• 1998

$La_{0.5}Sr_{0.5}MnO_{3-\delta}$ as air electrode for soild oxide fuel cell was synthesized by a citrate process and its cathodic polarization was determinated by the current interruption method on the Gd-doped ceria as electrolyte. The addition of citric acid increased the exothermic heat for the formation of $La_{0.5}Sr_{0.5}MnO_{3-\delta}$ perovskite oxide. The degree of the initial particle agglomeration was affected by the exothermic heat. Also the increase of cal-cination temperature enlarged the particle size and the higher sintering temperature accelerated the den-sification of $La_{0.5}Sr_{0.5}MnO_{3-\delta}$ layer after its being painted on $Ce_{0.8}Gd_{0.2}O_{1.9}$ electrolyte. In this study $La_{0.5}Sr_{0.5}MnO_{3-\delta}$ synthesized by citrate process of which the molar ratio of citric acid to metal nitrate was 2 calcined at $650^{\circ}C$ for 2hr and sintered at 1100 at $1200^{\circ}C$ for 4 hrs after slurry coating on Ce0.8Gd0.2O1.9 electrlyte showed the lowest cathodic polarization.

• Korean Chemical Engineering Research
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• v.48 no.3
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• pp.365-374
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• 2010

The ash reduction effects and fuel property changes of spent mushroom substrates by acid solution extraction, and the production possibilities of wood pellet fuel using them were studied. The ash weight of spent Pleurotus eryngii substrates was reduced from 8.81%(w/w) to 3.33%(w/w), and calorific value was increased from 3,958.3 kcal/kg to 4219.2 kcal/kg when extracted with a mixture of Acetic acid 2%(w/w) and Anhydrous citric acid 1%(w/w) in condition of liquid ratio 1:8, extraction temperature $55^{\circ}C$ and extraction time 180 min. The ash weight of spent Flammulina velutipes substrates was reduced from 14.91%(w/w) to 4.07%(w/w), and calorific value was increased from 4,190.3 kcal/kg to 4,219.2 kcal/kg when extracted with a mixture of Acetic acid 3%(w/w) and Anhydrous citric acid 1%(w/w) in condition of liquid ratio 1:8, extraction temperature $65^{\circ}C$ and extraction time 180 min. The ash weight of spent Pleurotus osteratus substrates was reduced from 3.31%(w/w) to 0.59%(w/w), and the smallest reduction was in calorific value from 4,558.6 kcal/kg to 4,216.2 kcal/kg when extracted with a mixture of Acetic acid 1%(w/w) and Anhydrous citric acid 1%(w/w) in condition of liquid ratio 1:8, extraction temperature $65^{\circ}C$ and extraction time 180 min.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2009.06a
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• pp.462-462
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• 2009

$CeO_2$는 고체 산화물 연료전지 (SOFC, soild oxide fuel cell)의 전해질 재료와 CMP(Chemical Mechanical Polishing) 슬러리 재료, 자동차의 3원 촉매, gas sensor, UV absorbent등 여러 분야에서 사용되고 있다. 본 연구에서는 위의 활용범위 외에 $CeO_2$의 구조적 안정성과 빠른 $Ce^{3+}/Ce^{4+}$의 전환 특성을 이용하여 lithium ion battery의 anode 재료로서 전기화학적 특성을 알아보고자 실험을 실시하였다. $CeO_2$ 합성에 사용되는 전구체인 cerium carbonate의 형상 및 크기, 비표면적과 같은 물리화학적 특성이 $CeO_2$ 분말의 특성에 직접적인 영향을 주기 때문에 전구체의 합성 단계에서 입자의 특성을 조절하였다. 전구체 합성의 출발원료로 cerium nitrate hexahydrate 와 ammonium carbonate를 사용하였고 반응온도 및 농도 등을 변화시켜 입자의 형상 및 결정상을 fiber형태의 orthorombic $Ce_2O(CO_3)_2{\cdot}H_2O$와 구형의 hexagonal $CeCO_3OH$의 세리아 전구체를 합성하였다. 이를 $300^{\circ}C$에서 30분 동안 하소하여 전구체의 입자형상을 유지하는 cubic $CeO_2$를 합성하고 X-ray diffraction, FE-SEM, micropore physisorption analyzer 분석을 통하여 입자의 결정상과 형상, 비표면적 등을 비교 분석하고 $Li/CeO_2$ couple의 충,방전 용량과 수명특성을 비교 분석하여 $CeO_2$의 전기화학적 특성을 알아보았다.

• Journal of Hydrogen and New Energy
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• v.28 no.1
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• pp.40-46
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• 2017

We reviewed the electrical properties of SOFC anode manufactured using spherical Ni and nano YSZ powder. When core-shell is fabricated by using submicron Ni as core and nano-sized YSZ as shell for SOFC anode, the electrical conductivity of the $0.2{\mu}m$ Ni-YSZ core-shell was 3 times higher than that of $1.0{\mu}m$ NiO or $1.0{\mu}m$ Ni-YSZ. Hydrogen selectivity was similar at $800^{\circ}C$, but hydrogen selectivity and methane conversion rate under $750^{\circ}C$ was 10~25% higher, Power density was more than 2 times, ASR was about 1/3, when exposed to $H_2$ atmosphere at $750^{\circ}C$ for a long time, Ni particles did not have any growth or cut off conduction path.

• Journal of the Korean Electrochemical Society
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• v.6 no.1
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• pp.59-64
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• 2003

We fabricated mixed ionic-electronic conducting membranes, $CH_4\;Using\;{0.7}Sr_{0.3}Ga_{0.6}Fe_{0.4}O_{3-\delta}$, by solid state reaction method for solid oxide fuel cell. The membranes consisted of single perovskite phase and exhibited high relative density, $>95\%$. We coated $La_{0.6}Sr_{0.4}CoO_{3-\delta}$ layer using screen printing method in order to improve surface reactivity of the $La_{0.7}Sr_{0.3}Ga_{0.6}Fe_{0.4}O_{3-\delta}$. As a result, the oxygen permeation flux of the coated $La_{0.7}Sr_{0.3}Ga_{0.6}Fe_{0.4}O_{3-\delta}$ showed higher value, $0.5ml/min{\cdot}cm^2\;at\;950^{\circ}C$ than the uncoated one. Higher oxygen permeation was observed in the porously coated Lao $La_{0.7}Sr_{0.3}Ga_{0.6}Fe_{0.4}O_{3-\delta}$membranes with larger grain sizes. Syngas, $CO+H_2$, was successfully obtained from methane gas, $CH_4$, using the $La_{0.6}Sr_{0.4}CoO_{3-\delta}$ coated $La_{0.7}Sr_{0.3}Ga_{0.6}Fe_{0.4}O_{3-\delta}$, with over $40\%\;of\;CH_4$ conversion and syngas yield. $La_{0.7}Sr_{0.3}Ga_{0.6}Fe_{0.4}O_{3-\delta}$ membrane was stable even when it was exposed to the reducing environment, methane, for 600 hrs at $950^{\circ}C$.