• Journal of the Korean Ceramic Society
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• v.45 no.12
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• pp.760-765
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• 2008

In this study, the effects of small amounts (${\leq}3\;mol%$) of Li doping on the sintering characteristics and electrochemical performance of $(ZrO_2)_{0.89}(ScO_{1.5})_{0.1}(CeO_2)_{0.01}$ (ScSZ) were investigated. By adding 3 mol% lithium, the densification temperature of ScSZ was reduced from the conventional temperature of $1400^{\circ}C$ to $1200^{\circ}C$. It was found that Li doping also led to changes in the Zr:Sc ratio at the grain boundaries. Correspondingly, the dispersion of lithium zirconia at the grain boundaries accelerated the growth of ScSZ grains and increased the grain boundary resistance at temperatures below $450^{\circ}C$. At elevated temperatures of $450{\sim}750^{\circ}C$, the electrical conductivity of the ScSZ after doping remained almost unchanged under air and reducing atmospheres. These results suggest that the addition of lithium is promising for use in low temperature co-firing of ScSZ-based components for intermediate temperature solid oxide fuel cells.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2006.05a
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• pp.547-548
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• 2006

This study focuses on a determination of amount of Pt in the Pt/C for catalysts of polymer electrolyte membrane fuel cells (PEMFC). PEMFC offer low weight and high power density and being considered fur automotive and stationary power applications. The PEMFC behavior is quite complex is influenced by several factors, including catalysts and structure of electrode and membrane type. Catalyst of electrode is important factor for PEMFC. One of the obstacles preventing polymer electrolyte membrane fuel cells from commercialization is the high cost of noble metals to be used as catalyst, such as platinum. To effectively use these metals, they have to be will dispersed to small particles on conductive carbon supports. The optimal amount of Pt in Pt/C was investigated by using polarization curves in single cell with $H_2/O_2$ operation.

• Journal of the Korean Solar Energy Society
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• v.32 no.spc3
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• pp.289-294
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• 2012

In recent years, understanding the dynamics of DC distribution system has become critically important due mainly to the increasing needs for the interconnection of DC distributed generators and the (DC-based) electric vehicle (EV) charging systems. In this paper, the characteristics of the DC grid system connected to the compact proton exchange membrane fuel cell (PEMFC) has been studied. In particular, the voltage and current transient phenomena were measured by varying the load of the DC grid system. Also, the voltage and current ripple were measured at the different load conditions. Our experimental results clearly manifested that the study contributes to the establishment of fundamental method to characterize the small DC grid system including distributed generation.

• 한국태양에너지학회:학술대회논문집
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• 2012.03a
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• pp.414-418
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• 2012

In recent years, understanding the dynamics of DC distribution system has become critically important due mainly to the increasing needs for the interconnection of DC distributed generators and the (DC-based) electric vehicle (EV) charging systems. In this paper, the characteristics of the DC grid system connected to the compact proton exchange membrane fuel cell (PEMFC) has been studied. In particular, the voltage and current transient phenomena were measured by varying the load of the DC grid system. Also, the voltage and current ripple were measured at the different load conditions. Our experimental results clearly manifested that the study contributes to the establishment of fundamental method to characterize the small DC grid system including distributed generation.

• Korean journal of food and cookery science
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• v.22 no.4 s.94
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• pp.419-427
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• 2006

The purpose of this study is to promote the substitution of rice flour for wheat flour in making bread and thus the consumption of rice by examining the effect of particle size of rice flour on leavening rice bread. For this purpose, several experiments were carried out. With regard to particle size distribution, 59.45% of wheat flour had passed 200 mesh and 3 kinds of rice flour milled to penetrate into 20, 35, and 45 mesh (S1, S2 and S3) had passed 21.88%, 33.1% and 36.38% of those for 200 mesh, respectively. To leaven the rice flour dough to bread, 25% of vital gluten was needed. To determine the optimal water quantity for rice bread dough, the hardness of wheat and rice flour dough was measured by rheometer. The appropriate water quantity for S1, S2 and S3 was set at 285 ml , 295 ml and 335${\sim}$340m1, respectively. The loaf volume index of the wheat flour bread was 6.24, while that of and rice flour bread S1, S2 and S3 was 5.38, 5.50 and 5.75, respectively. These results indicated that the loaf volume index of rice flour bread is lower than that of wheat flour bread, but that the volume of rice flour bread was increased with fuel particle size of rice flour. Scanning electron microscopy (SEM), image of the wheat bread tissue at a magnification of 35 times showed long, large, oval-shaped, air cells and thin cell membrane, as well as small air cells, whereas the images of rice flour showed angular, circular, air cells and rough and thick cell membrane. The size and number of air cells in the rice bread were larger in S2 and S3 with fuel particle flours than in S1. In particular, the bread made with S3 contained many air cells that were as large as those in the wheat bread were. In addition, when the inner cell wall was magnified 1500 times, almost no small air cell was observed in C and S3, whereas many fine air cells were observed in the cell wall of S1 and S2.

• Transactions of the Korean hydrogen and new energy society
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• v.14 no.1
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• pp.35-45
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• 2003

Polymer electrolyte fuel cells(PEFC) have been considered to be a suitable candidate for residential, portable and mobile applications, due to their high efficiency and power density, even at low operating temperature. KIER developed a 5kW class PEFC system for residential application and operated the system for over 1,000 hours. To develop a 5kW PEFC system, performance of a cell was improved through successive tests of single cell of small and large area. Fabrication of three 2,5 kW class stacks, design and fabrication of natural gas reformer, design of auxiliary equipments such as DC/DC converter, DC/AC inverter and humidifying units were carried out along with integration of components, operation and evaluation of total system. During the development period from 1999 to 2001, MEA(membrane electrode assembly) fabrication technologies, design and fabrication technologies for separators, stacking technologies and so on were developed, thereby providing basis for developing stacks of higher efficiency and power density in the future. Experience of development of natural gas reformer opened possibilities to use various kinds of fuels. Main results obtained from the development of a 5kW class PEFC system for residential application are summarized.

• Journal of the Korea Institute of Military Science and Technology
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• v.20 no.4
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• pp.528-535
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• 2017

Fuel cells have been spotlighted in the world for being highly efficient and environmentally friendly. A hydrogen which is the fuel of fuel cell can be obtained from a number of sources. Hydrogen source for operating the polymer electrolyte membrane fuel cell(PEMFC) in the current underwater environment, such as a submarine and unmanned underwater vehicles are currently from the metal hydride cylinder. However, metal hydride has many limitations for using hydrogen carrier, such as large volume, long charging time, limited storage capacity. To solve these problems, we suggest diesel reformer for hydrogen supply source. Diesel fuel has many advantages, such as high hydrogen storage density, easy to transport and also well-infra structure. However, conventional diesel reforming system for PEMFC requires a large volume and complex CO removal system for lowering the CO level to less than 10 ppm. In addition, because the preferential oxidation(PROX) reaction is the strong exothermic reaction, cooling load is required. By changing this PROX reactor to hydrogen separation membrane, the problem from PROX reactor can be solved. This is because hydrogen separation membranes are small and permeable to pure hydrogen. In this study, we conducted the pressurized diesel reforming and water-gas shift reaction experiment for the hydrogen separation membrane application. Then, the hydrogen permeation experiments were performed using a Pd alloy membrane for the reformate gas.

• Journal of the Korean Electrochemical Society
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• v.13 no.4
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• pp.223-234
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• 2010

In this review, the theory and applications of the complex capacitance analysis, which can be utilized in analyzing capacitor-like electrochemical systems, were summarized. Theoretically, it was suggested that the imaginary capacitance plots (Cim vs. log f) can provide a simple way to analyze electrochemical characteristics of capacitive systems, without complicated mathematical calculations. The usefulness of the complex capacitance analysis has been demonstrated by applying it to analyze EDLC characteristics of practical porous carbon electrodes, ionic conductivities inside small pores, and ionic resistances in the catalyst layers of polymer electrolyte membrane fuel cells.

• Journal of Korean Society of Water and Wastewater
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• v.27 no.4
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• pp.503-509
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• 2013

Electrochemical redox capacity of a microbial fuel cell (MFC) electrode is an important factor in the power density. This study was conducted to investigate the redox capacity of surface modified anode and cathode electrodes by measuring their conductivities. An anode electrode was modified with nitric acid and a cathode electrode was modified with heat treatment. The anode electrode modified with 20 % of the nitric acid concentration showed the highest conductivity of $6.2{\mu}S/cm/g$ and the maximum power density of $306.0mW/m^2$ when used in a MFC. The cathode electrode modified at $472^{\circ}C$ for 18 min showed the highest conductivity of $5.2{\mu}S/cm/g$ and the maximum power density of $276.20mW/m^2$ when used in a MFC. On the other hand, an MFC using both the electrodes showed the highest maximum power density of $408.2mW/m^2$. Meanwhile, a control MFC without modified electrodes generated very small voltage (0.014 mV), so the power density could not be measured.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2008.05a
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• pp.247-251
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• 2008

This paper presents a micro air pump actuated by PZT actuator (synthetic jet actuator) for air supply for micro fuel cells. The synthetic jet actuators are usually created by a traditional PZT-driven actuator, which consists of a small cylindrical cavity, in/outlet channel and PZT diaphragms. To design the micro air pump, a numerical analysis has been conducted for flow characteristics with respect to various geometries. A prototype of the micro air pump, with a size of $mm{\times}mm{\times}mm$, was fabricated by PDMS replication process and was conducted performance test. To control the PZT actuator, we used the SP4423 micro chips that can be amplified input voltage to reduce the controller size and the power consumption. With a voltage of 3V at 100Hz, the air pump's pumping pressure is 600pa and its power consumption is only 0.1mW.