• 한국세라믹학회지
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• 제44권4호
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• pp.214-218
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• 2007

The decrease of polarization resistance in cathode is the key point for operating at intermediate temperature SOFC (solid oxide fuel cell). In this study, the influence of Co substitution in B-site at complex perovskite on the electronic conductivity of PSCM ($Pr_{0.3}Sr_{0.7}Co_xMn_{(1-x)}$) was investigated. The PSCM series exhibits excellent MIEC (mixed ionic electronic conductor) properties. The ASR (area specific resistance) of PSCM3773 was $0.174{\Omega}{\cdot}cm^2\;at\;700^{\circ}C$. The activation energy of PSCM3773 was also lower than other compositions of PSCM. The TEC(thermal expansion coefficient) was decreased by addition of Mn. The ASR values were increased gradually during the thermal cycling test of PSCM37773 due to the delamination between electrolyte and cathode materials. The delamination was caused by the difference of TEC.

• 한국세라믹학회지
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• 제45권12호
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• pp.777-781
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• 2008

Experiments were conducted using SUS430 and Crofer 22 APU steels coated by LSM using plasma spray and slurry spray methods, respectively. High-temperature conductivity and oxidation resistance were investigated. For comparison, SUS430 and Crofer 22 APU without LSM coating were also investigated and coefficient of thermal expansion (CTE) was measured. The results show that the materials without LSM coating exhibit almost the same CTE as YSZ electrolyte in a range of temperatures of $550{\sim}850^{\circ}C$. When coated with LSM, the oxidation rate of the steels decreases by $30{\sim}40%$ using slurry spray and by $10{\sim}30%$ using plasma spray whereas the steels using plasma spray have a better high-temperature conductivity than the steels using slurry spray. It is thus concluded that the LSM coating has a limited effect on increasing high-temperature conductivity while it can effectively reduce the oxidation of the steels.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1997년도 추계학술대회 논문집 학회본부
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• pp.305-307
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• 1997

Gd-doped $CeO_2$, ultrafine powders were synthesized by the glycine-nitrate process and then their sintering and electrical characteristics were analysed using the dilatometric and AC impedance measurements. In the dilatometric measurements green bodies from the synthesized powders after milling shrinked to about $1470^{\circ}C$ in appearance and then expanded thermally with the increase of the heating temperature, whereas those from the synthesized powders before milling continuously shrinked to the temperatures of $1600^{\circ}C$. It may be due to the change of the packing density of the synthesized powders by milling. In the AC impedance measurements, the electrical resistivity of the Gd-doped $CeO_2$ bodies from the as-milled powders, sintered at $1500^{\circ}C$ with the increase of the sintering time, showed the minimum value at the sintering time of 10h. The minimum total resistivity of the Gd-doped $CeO_2$ bodies sintered at $1500^{\circ}C$ for 10h seems to result from the lowest activation energy by the combination between the activation energies for the resistivities at the grain interior and grain boundary.

• 한국연소학회:학술대회논문집
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• 대한연소학회 2003년도 제27회 KOSCO SYMPOSIUM 논문집
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• pp.109-113
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• 2003

Low pressure or vacuum carburizing(LPC) has undergone major further developments since 1980 and now it has achieved industrial maturity. The advantage of low pressure vacuum carburizing over gas carburizing is not only the creation of surface entirely free of oxide and environmentally friendly but also a reduction in batch times, lower gas and energy consumption and the prevention of soot. In this study the experiment was carried out to investigate the effects of vacuum atmosphere in the heating furnace. Heat transfer rate and uniformity of temperatures of test samples in the pressure range of a few 0.1torr was examined on a test charge of 100kg. It is found that the fuel saving rate due to decreasing heating time reach to 20% in the vacuum heating mode as compared with atmospheric heating mode. Also the uniformity of temperatures in the samples was improved significantly in the vacuum heating mode. Also the effects of the RC fan for stirring atmosphere inside furnace was examined. Results shows RC fan appears to provide a reasonable tool for improving uniformity of temperature in the atmospheric heating mode.

• 한국연소학회:학술대회논문집
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• 한국연소학회 2002년도 제25회 KOSCI SYMPOSIUM 논문집
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• pp.129-139
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• 2002

From the view of the environmental protection against the use of fossil fuels, a great of efforts have been exerted to find an alternative energy source. Hydrogen may become an alternative. However the product species of the hydrogen flame is only $H_2O$, which emits only non-luminous radiation so the radiation from it is much smaller than that for a hydrocarbon flame. In this study, the authors designed and fabricated a laboratory scale test furnace to study thermal characteristics of hydrogen-air diffusion flame. In addition, the effects of addition of reacting as well as non-reacting solid particles were experimentally investigated. Among the total heat flux to the wall, about 75% was occupied by radiation while 25 % by convection. When the aluminum oxide ($Al_2O_3$) particles were added, the radiative heat flux was reduced due to heat blockage effects. On the other hand, the total as well as the radiative heat flux was increased when the carbon particles were seeded, since the overall temperature increased. The effects of swirl and excess air ratio were also examined.

• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2009년도 추계학술대회 논문집
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• pp.187-190
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• 2009

$LaCrO_3$ series are the most common candidate materials for a ceramic interconnect for SOFC and the thermal expansion coefficient of these matches very well with that of YSZ electrolyte. In this study, characteristics of the coated films on the anode-support, which were formed by using $La_{0.8}Ca_{0.2}CrO_3$, $La_{0.8}Sr_{0.2}CrO_3$, $La_{0.8}Ca_{0.2}Co_{0.1}Cr_{0.9}O_3$ for ceramic interconnet for SOFC, were investigated. All powders showed single perovskite phase and the precursors had spherical shapes of $2{\mu}m{\sim}30{\mu}m$. According to SEM analysis, coated film of LCC on pretreated anode-support was more thicker, whereas the coated film on untreated anode-support was densely formed. As the results of electrical conductivity of anode-support coated with the ceramic interconnects, LCCC exhibited the most excellent electrical conductivity of 0.15S/cm at $750^{\circ}C$.

• 한국재료학회지
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• 제27권3호
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• pp.155-160
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• 2017

Doped-$LaCrO_3$ perovskites, because of their good electrical conductivity and thermal stability in oxidizing and/or reducing environments, are used in high temperature solid oxide fuel cells as a gas-tight and electrically conductive interconnection layer. In this study, perovskite $(La_{0.8}Ca_{0.2})(Cr_{0.9}Co_{0.1})O_3$ (LCCC) coatings manufactured by atmospheric plasma spraying followed by heat treatment at $1200^{\circ}C$ have been investigated in terms of microstructural defects, gas tightness and electrical conductivity. The plasma-sprayed LCCC coating formed an inhomogeneous layered structure after the successive deposition of fully-melted liquid droplets and/or partially-melted droplets. Micro-sized defects including unfilled pores, intersplat pores and micro-cracks in the plasma-sprayed LCCC coating were connected together and allowed substantial amounts gas to pass through the coating. Subsequent heat treatment at $1200^{\circ}C$ formed a homogeneous granule microstructure with a small number of isolated pores, providing a substantial improvement in the gas-tightness of the LCCC coating. The electrical conductivity of the LCCC coating was consequently enhanced due to the complete elimination of inter-splat pores and micro-cracks, and reached 53 S/cm at $900^{\circ}C$.

• 공업화학
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• 제4권1호
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• pp.153-161
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• 1993

$700-900^{\circ}C$의 온도범위와 여러 산소분압 조건에서 고체전해질 연료전지의 양극인 $La_{0.9}Sr_{0.1}MnO_3$에서 산소의 환원반응특성을 조사하였다. AC 임피던스법과 전류중단법에 의해 산소환원반응의 전하전달저항을 측정하였는데 두 방법으로 구한 간이 서로 잘 일치하였다. 전기화학적 산소환원반응의 활성화에너지는 대기압 조건에서 174kJ/mol의 값을 보였고, 산소분압에 따른 전하전달저항의 측정결과로 부터 이 전극에서 전기화학적 산소환원반응의 율속단계는 전하전달과정임을 알 수 있었다.

• 한국수소및신에너지학회논문집
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• 제28권5호
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• pp.512-520
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• 2017

This paper is a numerical study of various methods of applying SOFC hot BOP insulation. The application methods are four cases from case 1 to case 4, and the performance difference between the result of applying powdered insulation and the result of zoning using composite multi-layer insulation was examined. Numerical results show that the thermal stability of composite multi-layer insulation is better than that of powder insulation when the thermal conductivity is 0.04 W/mK. In the future, we will increase the thermal conductivity of the composite multi-layer thermal insulation material and find the greatest value of thermal conductivity with a similar result to that of the powder insulation.

• The Korean Journal of Ceramics
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• 제4권4호
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• pp.382-386
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• 1998

titanate and a silicon carbide/zirconium diboride particulate composite have each been blended with thermoplastic of aqueous binders and extruded. The green extrudates have diameters ranging between 50 and 150 ㎛ and polyethylene-base 150 ${\mu}m$ diameter fibers can be drawn down at elevated temperature to approximately 40 ${\mu}m$ diameter. Hollow fibers with 150${\mu}m$ outer and 90 ${\mu}m$ inner diameter can also be fabricated. Green fibers have been processed into chopped fiber felts for use as gas distributors/current collectors in an experimental solid oxide fuel cell (SOFC) and the first attempts at producing simple textile structures have been successful. The fibers, tubes and felts have been successfully debound and sintered and characterization of the sintered PSZ fibers, for example, has revealed a density in excess of 99% and tensile failure stresses up to 1.0 GPa for 78 ${\mu}m$ diameter fibers.