• Korean Journal of Materials Research
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• v.17 no.6
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• pp.313-317
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• 2007

In-situ micro-channeled multi tubular solid oxide fuel cell(SOFC) was fabricated using multi-pass extrusion process with out side diameter of 2.7 mm and active length of 5 mm that contained 61 individual cells. Cell materials used in this work were NiO-YSZ (50 : 50 vol.%), 8 mol% yttria-stabilized zirconia(8YSZ), $La_{0.8}Sr_{0.2}MnO_3(LSM)$ as anode, electrolyte, and cathode, respectively. The arrangement of each electrode and electrolyte layer in green bodies showed uniformity and integrity after extrusion and sintering. The XRD analysis confirmed that no reaction phases appeared and the microstructure of the electrolyte was fairly dense (relative density > 96%) after sintering.

• Journal of the Korean Ceramic Society
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• v.44 no.12
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• pp.727-732
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• 2007

In order to fabricate a highly performing cathode for low-temperature type solid oxide fuel cells working at below $700^{\circ}C$, electrode microstructure control and electrode polarization measurement were performed with an electronic conductor, $La_{0.8}Sr_{0.2}MnO_3$ (LSM) and a mixed conductor, $La_{0.6}Sr_{0.4}Co_{0.2}Fe_{0.8}O_3$(LSCF). For both cathode materials, when $Sm_{0.2}Ce_{0.8}O_2$ (SDC) buffer layer was formed between the cathode and yttria-stabilized zirconia (YSZ) electrolyte, interfacial reaction products were effectively prevented at the high temperature of cathode sintering and the electrode polarization was also reduced. Moreover, cathode polarization was greatly reduced by applying the SDC sol-gel coating on the cathode pore surface, which can increase triple phase boundary from the electrolyte interface to the electrode surface. For the LSCF cathode with the SDC buffer layer and modified by the SDC sol-gel coating on the cathode pore surface, the cathode resistance was as low as 0.11 ${\Omega}{\cdot}cm^2$ measured at $700^{\circ}C$ in air atmosphere.

• Journal of the Korean Ceramic Society
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• v.45 no.2
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• pp.90-93
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• 2008

The oxygen gas behavior in PDP (plasma Display Panel) glass melts doped with sulfate ($SO_4^{-2}$) or blast furnace slag (BFS, $S^{2-}$) or both by means of yttria-stabilized zirconia (YSZ) electrodes was observed after the first fining. The temperature dependence of oxygen equilibrium pressure ($P_{O2}$) in each melt showed typical behavior, namely $P_{O2}$ decreased as temperature decreased. This suggests that an oxidation of $S^{4+}$ to $S^{6+}$ took place. However, the $P_{O2}$-value at constant temperature increased in the following order: BFS$P_{O2}$ of the melt doped with sulfate+BFS was much lower than that of the melt with only sulfate, although only 10% of sulfur was added by the BFS. This behavior can be explained by the redox reaction between sulfide ions in the BFS and dissolved oxygen ions in the melt during the first fining.

• Journal of the Korean Ceramic Society
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• v.44 no.8
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• pp.419-423
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• 2007

The behavior of oxygen gas participating in fining was observed in CRT (Cathode Ray Tube) glass melts doped with $Sb_2O_5\;or\;CeO_2$ by means of a yttria-stabilized zirconia (YSZ) electrode. The temperature dependence of the oxygen equilibrium pressure ($P_{o2}$) or the activity in both melts showed typical behavior corresponding to a theoretical redox reaction. In other words, the $P_{o2}$ value of melts with $CeO_2$ was lower than that of melts with $Sb_2O_5$ above $1250^{\circ}C$. The result implies that $Sb_2O_5$, is more efficient as a fining agent compared to $CeO_2$. On the other hand, melts from a batch containing $Sb_2O_5\;and\;KNO_3$ showed much higher $P_{o2}$ values compared to melts without $KNO_3$ above $1350^{\circ}C$. It is suggested that the addition of $KNO_3$ to CRT glass batch contributes partly to the first fining of the melts.

• Journal of the Korean Ceramic Society
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• v.47 no.2
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• pp.195-198
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• 2010

It has been considered to apply GDC ($Gd_{0.1}Ce_{0.9}O_{1-X}$) for low-temperature SOFC electrolytes because it has higher ionic conductivity than YSZ at low temperature. However, open circuit voltage with using GDC ($Gd_{0.1}Ce_{0.9}O_{1-X}$) electrolyte in SOFCs, becomes lower than using YSZ (8 mol% Yttria stabilized Zirconia) electrolyte because GDC has electronic conductivity. In this work, the effect of changing GDC electrolyte thickness on the open circuit voltage has been investigated. Ni-GDC anode-supported unit cells were fabricated as follows. Mixed NiO-GDC powders were pressed and pre-sintered at $1200^{\circ}C$. And then, GDC electrolyte material was dip-coated on the anode and sintered at $1400^{\circ}C$. Finally the LSCF-GDC cathode material was screen-printed on the electrolyte and sintered at $1000^{\circ}C$. Electrolyte thickness was controlled by the number of dip-coating times. Open circuit voltage was measured depending on electrolyte thickness at $650^{\circ}C$ and found that the thicker GDC electrolyte was, the better OCV was.

• Journal of the Korean Ceramic Society
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• v.56 no.2
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• pp.160-166
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• 2019

In this study, we investigated the long-term stability of Nd₂NiO₄ solid oxide fuel cell (SOFC) cathodes to evaluate their chromium poisoning tolerance. Symmetrical cells consisting of Nd2NiO4 electrodes and a yttria-stabilized zirconia electrolyte were fabricated and the cell potential and polarization resistance were measured at 850 ℃ in the presence of gaseous chromium species for 800 h. Up to 500 h of operation, the cell potential remained constant at 500 mA/㎠. However, it increased slightly over the operation duration of 550-800 h. No appreciable increase was observed in the polarization resistance of the Nd₂NiO₄ cathode during the entire operation of 800 h. Physicochemical examinations revealed that the gaseous chromium species did not form chromium-related contamination not only in the Nd₂NiO₄ cathode but also at the cathode/electrolyte interface. The results demonstrated that Nd₂NiO₄ is resistant to chromium poisoning, and hence is a potential alternative to standard perovskite cathodes.

• Journal of the Korean Ceramic Society
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• v.48 no.1
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• pp.106-109
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• 2011

In order to fabricate 8YSZ thick film by silk screen printing, YSZ(yttria-stabilized zirconia) commercial powder was used as starting materials. Paste for screen printing was made by mixing 8YSZ powder and organic vehicles. 8YSZ thick film was formed on $Al_2O_3$ substrate. The crystal structure, and microstructure were investigated. Grain size of 8YSZ was increased with increasing calcination temperature and rapid grain growth was shown after calcination at $1300^{\circ}C$. Microstructure showed the mixture of large and small grain size after $1400^{\circ}C$ sintering. Shrinkage rate of 8YSZ thick film sintered at $1400^{\circ}C$ was more than 40%.

• Journal of Electrochemical Science and Technology
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• v.7 no.1
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• pp.33-40
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• 2016

Sr_0.92Y_0.08TiO_3-δ (SYT) was investigated as an alternative anode in humidified CH₄ fuel for SOFCs at low temperatures (650 ℃-750 ℃) and compared with the conventional Ni/yttria-stabilized zirconia (Ni/YSZ) anode. The goal of the study was to directly use a hydrocarbon fuel in a SOFC without a reforming process. The cell performance of the SYT anode was relatively low compared with that of the Ni/YSZ anode because of the poor electrochemical catalytic activity of SYT. In the presence of CH₄ fuel, however, the cell performance with the SYT anode decreased by 20%, in contrast to the 58% decrease in the case of the Ni/YSZ anode. The severe degradation of cell performance observed with the Ni/YSZ anode was caused by carbon deposition that resulted from methane thermal cracking. Carbon was much less detected in the SYT anode due to the catalytic oxidation. Otherwise, a significant amount of bulk carbon was detected in the Ni/YSZ anode.

• Korean Journal of Materials Research
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• v.15 no.6
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• pp.375-381
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• 2005

High temperature oxidation behavior of thermal barrier coating (TBC) system (IN738 substrate + NiCoCrAlY or NiAl bond coat with or without Pt + yttria stabilized zirconia) prepared by air plasma spray (APS) process has been studied in order to understand the effect of Pt addition to bond coat on the stability of TBC system. Specimens were oxidized in thermal cycling and isothermal oxidation test at $1100^{\circ}C$. The Pt addition in TBC system with NiCoCrAlY bond coat showed a longer life time compared to that without addition of Pt. Pt addition to TBC system is believed to help the formation of more stable thermally grown oxide, $Al_2O_3$, at the TBC/bond coat interface, leading to a longer lifetime of TBC system.

• Journal of Sensor Science and Technology
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• v.24 no.1
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• pp.6-9
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• 2015

Conventional leak detectors are widely based on helium gas sensors. However, the usage of hydrogen sensors in leak detectors has increased because of the high prices of helium leak detectors and the dearth in the supply of helium gas. In this study, a hydrogen leak detector was developed using solid-state hydrogen sensors. The hydrogen sensors are based on Park-Rapp probes with heterojunctions made by oxygen-ion conducting Yttria-stabilized zirconia and proton-conducting In-doped $CaZrO_3$. The hydrogen sensors were used for determining the potential difference between air and air balanced 5 ppm of $H_2$. Even though the Park-Rapp probe shows an excellent selectivity for hydrogen, the sensitivity of the sensor was low because of the low concentration of hydrogen, and the oxygen on the surface of the sensor. In order to increase the sensitivity of the sensor, the sensors were connected in series by Pt wires to increase the potential difference. The sensors were tested at temperatures ranging from $500-600^{\circ}C$.