• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2006년도 추계학술대회
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• pp.368-371
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• 2006

[ $La_{0.8}Sr_{0.2}Co_{1-x}Mn_xO_3$ ] cathode as a high performance cathode on YSZ electrolyte was studied by analyzing impedance spectra. It was shown that cathode property of $La_{0.8}Sr_{0.2}Co_{1-x}Mn_xO_3$ is bet ter than that of$La_{0.8}Sr_{0.2}CoO_3$. At $700^{\circ}C$ in air environment, $La_{0.8}Sr_{0.2}Co_{0.4}Mn_{0.6}O_3$ cathode on CGO- layered YSZ electrolyte showed very low area specific resistance of $0.14{\Omega}cm^2$, which is low enough for intermediate-temperature sol id oxide fuel cells. This is because material properties of ionic conductivity and thermal expansion compatibility with electrolyte were optimized. Judging from activation energy and oxygen part i al pressure dependance of cathode property, it was noted that oxygen surface exchange kinetics is dominantly influential on cathode property in higher temperature region than $700^{\circ}C$ and oxygen self-diffusion in cathode material is more influential in lower temperature region.

• 한국항공우주학회지
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• 제39권7호
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• pp.627-633
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• 2011

연료전지 무인기 탑재용 수소발생기의 온도환경변화에 따른 성능평가를 수행하였다. 수소 저장 및 발생을 위해 화학수소화물 중 수소함량이 높고 저장성이 우수한 수소화붕소나트륨($NaBH_4$)을 연료로 사용하였으며, 촉매를 이용한 가수분해반응을 통해 수소를 발생하였다. 수소발생기의 온도환경변화를 위한 저온 및 고온 챔버를 각각 준비하였으며, 온도범위는 $-20^{\circ}C$에서 $60^{\circ}C$까지 $20^{\circ}C$의 간격으로 설정하였다. 20과 25wt.%의 $NaBH_4$ 용액 농도에서 수소발생기의 수소발생률과 반응기와 분리기의 온도변화를 측정하였다. 수소 발생률은 반응주기가 반복될수록 감소하였으며, 저온 환경에서는 높은 수소발생률을 보였지만, 고온 환경에서는 수소발생률이 급격히 감소하였다. 수소발생률의 감소는 촉매유실과 촉매표면의 $NaBO_2$ 도포가 원인으로 확인되었다.

• Carbon letters
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• 제6권3호
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• pp.181-187
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• 2005

Bipolar plates require some specific properties such as electrical conductivity, mechanical strength, chemical stability, and low permeability for the fuel cell application. This study investigated the effects of carbon nanotube (CNT) contents and process conditions of hot press molding on the electrical and physical properties using CNT 3~7 wt% added graphite nano-composites in the curing temperatures range of 140~$200^{\circ}C$ and pressure of 200~300 kg/$cm^2$. Bulk density, hardness and flexural strength increased with increasing CNT contents, curing pressure and temperature. With the 7 wt% CNT added noncomposite, the electrical resistance improved by 30% and the flexural strength increased by 25% as compared to that without CNT at the temperature of $160^{\circ}C$ and pressure of 300 kg/$cm^2$. These properties were close to the DOE reference criteria as bulk resistance of 13 $m{\Omega}cm$ and tensile strength of 515 kg/$cm^2$.

• 한국세라믹학회지
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• 제42권12호
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• pp.816-820
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• 2005

The doped-ceria is a strong candidate material for an intermediate temperature SOFC. However, the mechanical strength and the magnitude of electrical conductivity need to be increased at low sintering temperature. In this study, to improve both properties, $1at\% $ of Mg, Ca, Cr, Fe, Co, Ni, Cu, Ga, and Zr were added to the GDC20 ($20at\%$ Gd-doped Ceria) and sintered at $1350^{\circ}C$ that is $250^{\circ}C$ lower than $1600^{\circ}C$. With addition, the relative density of the sintered sample increased. Fe, Co, Ni, Cu, Ga doped-GDC20 showed high relative density over $92\%$. Among them, Ga doped-GDC20 showed the most improved sinterability. The conductivity of doped­GDC20 increased by $\~10$ times at $300\~700^{\circ}C$.

• 한국수소및신에너지학회논문집
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• 제15권2호
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• pp.137-143
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• 2004

For hydrogen generation from aqueous alkilne $NaBH_4$ solution, Co-B catalyst was prepared by chemical reduction method using $NaBH_4$ as a reduction chemical. Effects of solution temperature, amount of catalyst loading, $NaBH_4$ concentration, and NaOH (a base-stabilizer) concentration on the hydrogen generation rate were exmanined. Compared to Ru catalyst generally used, the low-cost Co-B catalyst exhibited almost comparable activity to the hydrogen generation reaction.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2007년도 춘계학술대회A
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• pp.1433-1438
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• 2007

Characteristics of a phase change type micro actuator have been studied. The micro actuator has been designed for a micro-pump in an active direct methanol fuel cell(DMFC), consisting of an actuating chamber, a membrane, an electric heater, and a sensor of resistance temperature detector (RTD). In the present study, researches have been focused on the response of the actuator to control algorithm of the heater. The experiments demonstrated that the displacement of the membrane increase with temperature variation which is a function of applied voltage, duty ratio, and operating frequency of heating. The results also showed that operation of the actuator with high voltage at small duty of heating is more efficient than the same power consumption of heating with low voltage at large duty.

• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2009년도 춘계학술대회 논문집
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• pp.328-330
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• 2009

1 kW class Polymer Electrolyte Fuel Cell(PEFC) co-generation systems have been developed from 2001 and evaluated for improvement of efficiency, durability and reliability of the system. This paper introduce new version system including with excellent reliability, durability and user friendly applications. Its electrical and overall efficiency showed 35 % and 80 %, respectively, and noise level of the system was less than 45 dB. In addition, this system have various functions such as load change, $N_2$ less purge, low emission and low temperature operation ($-15^{\circ}C$) through development of operation logic. This system was designed for convenient installation in indoor and outdoor due to the compactness of size and the separation of electrical and heat recovery units, which means a user can select the size of heat recovery unit.

• Korean Chemical Engineering Research
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• 제50권4호
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• pp.627-631
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• 2012

휴대용 고분자전해질 연료전지의 수소발생용으로써 $NaBH_4$는 많은 장점을 갖고 있다. 본 연구에서는 $NaBH_4$ 가수분해 반응용 Co-P-B/Cu 촉매의 내구성에 대해 연구하였다. Co-P-B/Cu 촉매의 내구성 미치는 반응 온도, $NaBH_4$ 농도, NaOH 농도, 촉매 소성온도 등의 영향에 대해 실험하였다. 촉매의 내구성은 가수분해 반응 중에 발생하는 gel 형성에 영향을 받았다. 즉 gel 형성에 의해 촉매 손실률이 증가하였다. $NaBH_4$ 농도가 고농도일 때는 $60^{\circ}C$ 이상에서는 gel 형성이 안 되어 촉매 손실률이 낮았다. 그러나 $40^{\circ}C$ 이하에서는 gel이 형성되어 촉매 손실률이 증가했다. $NaBH_4$ 20 wt%, $40^{\circ}C$에서 NaOH 농도증가에 따라 겔이 형성되어 촉매 손실률이 증가함을 보였다. Co-P-B/Cu 촉매의 높은 온도에서 소성은 내구성을 향상시켰지만 촉매 활성을 감소시켰다.

• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2008년도 추계학술대회 논문집
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• pp.37-39
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• 2008

본 연구에서는 저온 데칼 전사법을 이용하여 막 전극 접합체(Membrane Electrode Assembly, MEA)를 제조하였다. 제조된 MEA는 직접 메탄올 연료 전지(Direct Methanol Fuel Cell, DMFC)를 이용하여 성능 테스트를 하였다. 저온 데칼 전사법은 $140^{\circ}C$의 낮은 온도에서 촉매 층을 데칼 기판에서 멤브레인으로 전사시키고, 전사된 촉매 층의 표면에 형성되는 것으로 알려진 이오노머 스킨 층의 형성을 막기 위해 이오노머/촉매/카본/기판의 구조로 되어 있는 데칼 기판을 사용한다. 저온 데칼 전사법으로 제조 된 카본 층이 있는 MEA의 DMFC 성능이 카본 층이 없이 데칼 전사법으로 제조된 MEA나 전통적인 고온 데칼 전사법으로 제조된 MEA, 또는 직접 스프레이 코팅법으로 제조된 MEA의 성능보다 높게 나온 것을 알 수 있다. 저온 데칼 전사법으로 제조된 MEA의 DMFC 성능이 향상된 것은 촉매 층 위에 이오노머 스킨이 형성되지 않아 반응물의 확산이 원활하게 이루어지기 때문이다. 이를 위한 특성 분석으로 EIS, CV를 측정하였다.

• 한국세라믹학회지
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• 제52권5호
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• pp.331-337
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• 2015

$LaBO_3$ (B = Cr, Mn, Fe, Co, and Ni) perovskites, the most common perovskite-type mixed ionic-electronic conductors (MIECs), are promising candidates for intermediate-temperature solid oxide fuel cell (IT-SOFC) cathodes. The catalytic activity on MIEC-based cathodes is closely related to the bulk ionic conductivity. Doping B-site cations with other metals may be one way to enhance the ionic conductivity, which would also be sensitively influenced by the chemical composition of the dopants. Here, using density functional theory (DFT) calculations, we quantitatively assess the activation energies of bulk oxide ion diffusion in $LaBO_3$ perovskites with a wide range of combinations of B-site cations by calculating the oxygen vacancy formation and migration energies. Our results show that bulk oxide ion diffusion dominantly depends on oxygen vacancy formation energy rather than on the migration energy. As a result, we suggest that the late transition metal-based perovskites have relatively low oxygen vacancy formation energies, and thereby exhibit low activation energy barriers. Our results will provide useful insight into the design of new cathode materials with better performance.