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The effect of the pore structure of a high surface area hydrated lime in a humid environment
Taimin Noh,신현규,전호환,Herbert Giesche,이희수 한양대학교 세라믹연구소 2012 Journal of Ceramic Processing Research Vol.13 No.3
The degradation behavior of hydrated lime sorbent exposed to a humid environment was investigated in terms of a change of the pore structure, phase transition, and particle aggregation. Di-ethylene glycol (DEG)-coated quicklime was hydrated to prepare a sorbent with a high surface area. The hydrated lime sorbent was maintained in a consistent chamber at 50 οC and 60% relative humidity for 168 h. As the degradation time of the sorbents exposed to the humid environment was increased,the calcite phase fraction was increased due to the carbonation process, whereas the reactivity for SO2 gas was reduced. A decrease in the specific surface area of the sorbents, from 45.8 m2/g to 7.6 m2/g, was also observed with elapsed degradation time. Also the clogging of small size pores having a size range of 30~40Å was observed due to the particle aggregation and the carbonation process by the humidity. Consequently, the degradation of hydrated lime sorbent in a humid environment was attributed to a collapse of the pore structure originating from the carbonation process and the particle aggregation.
Jungdae Kim,Jinseong Kim,Taimin Noh,Jeongwook Kim,이희수 한양대학교 세라믹연구소 2011 Journal of Ceramic Processing Research Vol.12 No.4
The effect of thulium oxide (Tm2O3) doping on the electrical properties of barium titanate (BaTiO3) ceramics was investigated in terms of the crystallinity and core-shell structure. The electrical properties of the Tm2O3 doped BaTiO3 were evaluated by measurements of the dielectric constant and temperature coefficient of capacitance (TCC) in addition to insulation resistance (IR). The dielectric constant and the IR of an undoped dielectric specimen were about 30% and 20%, respectively, lower than the values of a 1 mol% Tm2O3 doped specimen which met the reliability test condition in the range from -55 to 125 oC. The addition of Tm2O3 in BaTiO3 contributed to the enhanced electrical properties; however, an excessive addition had bad effects on the characteristics of BaTiO3 due to the formation of a second phase and the expansion of the shell region. This could be explained by the fact that the improved dielectric properties and IR according to the appropriate doping of Tm2O3, were revealed by an increase of the crystallinity and the reinforcement of the core-shell structure in BaTiO3.
Imdadullah Thaheem,조동우,Taimin Noh,임하니,이강택 한국공업화학회 2021 Journal of Industrial and Engineering Chemistry Vol.96 No.-
The application of ceramic coatings has been presented as an effective method to suppress the oxidationscale growth and Cr evaporation of ferritic stainless steels used in solid oxide fuel cell (SOFC)interconnects. In this work, Mn1.45-0.5xCo1.45-0.5xCuxY0.1O4 materials with various Cu contents (x = 0.1, 0.3,and 0.5) were synthesized through a facile glycine nitrate process as a protective coating on a metallicinterconnect (SUS 441). It was observed that the lattice parameter decreased from 8.31 Å (x = 0.1) to8.22 Å (x = 0.5) with increasing Cu content (x). The effects of Cu content (x) on the phase stability as wellas sintering, electrical, and thermal expansion were investigated. The results confirmed that theMn1.3Co1.3Cu0.3Y0.1O4 spinel had the highest electrical conductivity of 115 S cm 1 at 800 C and an averagethermal expansion value of 11.98 10 6 K 1 in the temperature range of 20–1000 C. The ASR ofMn1.3Co1.3Cu0.3Y0.1O4 coated SUS441 (7.7 10 5V-cm2 at 800 C) was 3 orders of magnitude lower thanthat of the uncoated sample. Moreover, the Mn1.3Co1.3Cu0.3Y0.1O4 coated interconnect exhibited excellentlong-term stability up to 1000 h at 800 C without any observable degradation, while the ASR of theuncoated sample increased by >850% for 1000 h (from 0.001 V-cm2 to 0.06 V-cm2) under the sameconditions. The oxidation kinetics obeying the parabolic law with a rate constant of Mn1.3Co1.3Cu0.3Y0.1O4(1.64 10 9mg2cm 4 s 1) was 4 orders of magnitude lower than that of bare SUS 411(7.4 10 5mg2cm 4 s 1) at 750 C for 2000 h. These results demonstrate that the Mn1.3Co1.3Cu0.3Y0.1O4is a promising coating material with high electrical conductivity and excellent durability for metallicinterconnects of intermediate-temperature SOFCs.
Thaheem, Imdadullah,Joh, Dong Woo,Noh, Taimin,Lee, Kang Taek Elsevier 2019 International journal of hydrogen energy Vol.44 No.8
<P><B>Abstract</B></P> <P>Chromia scale growth and Cr evaporation of ferritic stainless steel interconnects are known to be major causes of serious degradation of the solid oxide fuel cell (SOFC) stack. The development of suitable ceramic coating materials on the metallic interconnects has been demonstrated as an effective way to address these challenges. Herein, we developed a Mn<SUB>1.35</SUB>Co<SUB>1.35</SUB>Cu<SUB>0.2</SUB>Y<SUB>0.1</SUB>O<SUB>4</SUB> (MCCY) spinel material via a facile glycine-nitrate process as a protective coating on a metallic interconnect (SUS 441). Crystal structure and surface charge state analysis of the MCCY material revealed that co-doping of Y and Cu into the (Mn,Co)<SUB>3</SUB>O<SUB>4</SUB> spinel resulted in redistribution of the Mn ions (Mn<SUP>3+</SUP> and Mn<SUP>4+</SUP>) into the octahedral site, which increased the electrical conduction by enhanced small polaron hopping. Accordingly, the MCCuY-coated interconnect exhibited ∼8 times lower area specific resistance (ASR) than that of the undoped Mn<SUB>1.5</SUB>Co<SUB>1.5</SUB>O<SUB>4</SUB> (MCO) coated interconnect. Moreover, time-dependent ASR behavior of MCCuY-coated sample was monitored in-situ using electrochemical impedance spectroscopy at 650 °C, showing excellent stability with no observable change for >1000 h, while the ASR of the MCO-coated sample was raised by ∼71%. After 1000 h operation, we found strong adhesion between the MCCuY coating and the metallic interconnect as well as remarkably restricted Cr diffusion into the coating layer. Furthermore, the parabolic constant associated with the oxidation kinetics of the MCCuY-coated substrate (8.25 × 10<SUP>−11</SUP> mg<SUP>2</SUP> cm<SUP>−4</SUP> s<SUP>−1</SUP>) was ∼1 order of magnitude lower than that of the MCO-coated one (7.34× 10<SUP>−10</SUP> mg<SUP>2</SUP> cm<SUP>−4</SUP> s<SUP>−1</SUP>) at 650 °C after 1000 h measurement. These results demonstrate that the MCCuY is a highly promising coating material of metallic interconnects for intermediate-temperature SOFC applications.</P> <P><B>Highlights</B></P> <P> <UL> <LI> A MCCuY spinel material is developed as a metallic interconnect protective coating. </LI> <LI> The MCCuY-coating exhibits ∼8 times lower ASR compared to the undoped MCO-coating. </LI> <LI> The MCCuY-coated sample shows excellent stability without degradation for >1000 h. </LI> <LI> The oxidation kinetics of the MCCuY-coating is ∼1 order lower than MCO-coating. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>