• Korean Journal of Materials Research
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• v.17 no.8
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• pp.397-401
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• 2007

Fe based SOFC(Solid Oxide Fuel Cell) interconnector was fabricated by using the spark plasma sintering process and its microstructure and mechanical properties were investigated in this study. To fabricate the interconnector, the Fe-26Cr powder was mixed with the Ag (5, 10, 20wt.%) particles. In the Fe-26Cr-Ag sintered bodies, the Ag particles were almost dispersed at the grain boundary of the Fe-26Cr. The sintered bodies have the density of 87.2-97.5%, the density increases with increasing Ag content at sintering temperature of $850^{\circ}C$. Also, the compressive yield strength increases with increasing Ag content at the same sintering temperature.

• Journal of the Korean Ceramic Society
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• v.52 no.5
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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.

• Korean Journal of Metals and Materials
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• v.50 no.6
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• pp.463-468
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• 2012

A 71.5 wt%Mg-23.5 wt%Ni-5 wt%$Fe_2O_3$ (Mg-23.5Ni-$5Fe_2O_3$) sample was prepared by a quite simple process, reactive mechanical grinding, and its hydriding and dehydriding properties were then investigated. The reactive mechanical grinding of Mg with Ni and $Fe_2O_3$ is considered to facilitate nucleation and shorten the diffusion distances of the hydrogen atoms. After the hydriding-dehydriding cycling, the Mg-23.5Ni-$5Fe_2O_3$ sample contained $Mg_2Ni$ phase. Expansion and contraction of the hydride-forming materials (Mg and $Mg_2Ni$) with the hydriding and dehydriding reactions are also considered to increase the hydriding and dehydriding rates of the mixture by forming defects and cracks leading to the fragmentation of the particles. The temperature dependence of the hydriding rate of the sample is discussed.

• 한국신재생에너지학회:학술대회논문집
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• 2010.11a
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• pp.85.2-85.2
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• 2010

There is widespread effort to develop polymer membranes in place of Nafion for high temperature polymer electrolyte membrane fuel cell(PEMFC). In our study, SiO2 membranes are arranged by electrospinning method. For impregnation solution, the modified sulfonated poly(ether ether ketone)(SPEEK) polymer is prepared from sulfonation, sulfochlorination, partial reduction and lithiation reaction. The modified polymer is cross-linked with 1,4-diiodobetane in NMP solvent and then blended with Heteropoly acid(HPA). The characterization of membranes is confimed by FT-IR, Thermogravimetry(TGA), water uptake test and single cell performance test for PEMFC, etc. The composite membrane shows satisfactory thermal and mechanical properties. Beside, The membrane exhibits good ion exchange capacity and high proton conductivity. As a result, The composite membrane is promising as an alternative membrane in high temperature PEMFC.

• Journal of Hydrogen and New Energy
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• v.28 no.6
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• pp.657-662
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• 2017

This paper presents the reversible electrolysis characteristics of a solid oxide fuel cell (SOFC) using a $10{\times}10cm^2$ anode supported planar cell with an active area of $81cm^2$. In this work, current-voltage characteristic test and reversible electrolysis cycle test were carried out sequentially for 2,114 hours at a furnace temperature of $700^{\circ}C$. The current-voltage characteristics for reversible electrolysis mode was measured at a current of ${\pm}26.7A$ under various $H_2O$ utilization conditions. The reversible electrolysis cycle was performed 50 times at a current of ${\pm}32.4A$. As a result, The performance degradation of SOEC mode was larger than that of SOFC mode.

• Journal of Hydrogen and New Energy
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• v.31 no.2
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• pp.169-176
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• 2020

There is a growing interest in hydrogen energy utilization since an alternative energy development has been demanded due to the depletion of fossil fuels. Hydrogen is produced by the reforming reaction of natural gas and biogas, and the electrolysis of water. An solid oxide electrolyte cell (SOEC) is reversible system that generates hydrogen by electrolyzing the superheated steam or producing the electricity from a fuel cell by hydrogen. If the water can be converted into steam by waste heat from other processes it is more efficient for high-temperature electrolysis to convert steam directly. The reasons are based upon the more favorable thermodynamic and electrochemical kinetic conditions for the reaction. In the present study, steam at over 180℃ and 3.4 bars generated from a boiler were converted into superheated steam at over 700℃ and 3 bars using a cylindrical steam superheater as well as the waste heat of the exhaust gas at 900℃ from a solid refuse fuel combustor. Superheated steam at over 700℃ was then supplied to a high-temperature SOEC to increase the hydrogen production efficiency of water electrolysis. Computational fluid dynamics (CFD) analysis was conducted on the effects of the number of 90° elbow connector for piping, insulation types and insulation layers of pipe on the exit temperature using a commercial Fluent simulator. For two pre-heater injection method of steam inlet and ceramic wool insulation of 100 mm thickness, the highest inlet temperature of SOEC was 744℃ at 5.9 bar.

• Journal of computational fluids engineering
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• v.16 no.1
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• pp.42-47
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• 2011

In this paper, various operating parameters of stream reforming process from methane in stream reformer and preconverter for MCFC is studied by numerical method. Commercial code is used to simulated the porous catalyst with user subroutine to model three dominant chemical reactions which are Stream Reforming(SR), Water-Gas Shift(WGS), and Direct Stram Reforming(DSR). The hydrogen production is tested with different wall temperature and different reactor shapes. The calculated results of the concentration of hydrogen in stream reformer are very well consistent with experimental results. This numerical study gives the design reactor wall temperature condition and size of reactor to satisfy the required fuel conversion.

• Journal of the Korean Electrochemical Society
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• v.7 no.2
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• pp.69-79
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• 2004

To correctly simulate performance characteristics of fuel cells with a modeling method, various physical and chemical phenomena must be considered in fuel cells. In this study, performance characteristics of planar solid oxide fuel cells were simulated by a commercial CFD code, CFD-ACE+. Through simultaneous considerations for mass transfer, heat transfer and charge movement according to electrochemical reactions in the 3-dimensional planar SOFC unit stack, we could successfully predict performance characteristics of solid oxide fuel cells under operation for structural and progress variables. In other words, we solved mass fraction distribution of reactants and products for diffusion and movement, and investigated qualitative and quantitative analysis for performance characteristics in the SOFC unit stack through internal temperature distribution and polarization curve for electrical characteristics. Through this study, we could effectively predict performance characteristics with variables in the unit stack of planar SOFCs and present systematic approach for SOFCs under operation by computer simulation.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.33 no.12
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• pp.968-976
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• 2009

As the global warming becomes a serious environmental problem, studies of reducing $CO_2$ emission in power generation area are in progress all over the world. One of the carbon capture and storage(CCS) technologies is known as oxy-fuel combustion power generation system. In the oxy-fuel combustion system, the exhaust gas is mainly composed of $CO_2$ and $H_2O$. Thus, high-purity $CO_2$ can be obtained after a proper $H_2O$ removal process. In this paper, an oxy-fuel combustion cycle that recovers the waste heat of a high-temperature fuel cell is analyzed thermodynamically. Variations of characteristics of $CO_2$ and $H_2O$ mixture which is extracted from the condenser and power consumption required to obtain highly-pure $CO_2$ gas were examined according to the variation of the condensing pressure. The influence of the number of compression stages on the power consumption of the $CO_2$ capture process was analyzed, and the overall system performance was also investigated.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.31 no.5
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• pp.473-481
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• 2007

Compared to other types of fuel cells, SOFC has advantages like a wide output range and the direct use of hydrocarbon fuel without the process of external reforming. Particularly because the direct use of fuel without reforming reaction is closely linked to overall system efficiency, it is a very attractive advantage. We tried the operation with methane. However, although methane has a small number of carbons compared to other hydrocarbon fuels, our experiment found the deposition of carbon on the surface of the SOFC electrode. To overcome the problem, we tried the operation through activating internal reforming. The reason that internal reforming was possible was that SOFC runs at high temperature compared to other fuel cells and its electrode is made of Ni, which functions as a catalyst favorable for steam reforming.