• Proceedings of the Korean Magnestics Society Conference
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• 2008.12a
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• pp.155.2-155.2
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• 2008

• Proceedings of the Korean Magnestics Society Conference
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• 2008.12a
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• pp.160.1-160.1
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• 2008

• Environmental Sciences Bulletin of The Korean Environmental Sciences Society
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• v.4 no.2
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• pp.95-102
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• 2000

Methane combustion over perovskite-type oxides prepared using the malic acid method was investigated. To enhance the catalytic activity, the perovskite oxides were modified by the substitution of metal into their A or B site. In addition, the reaction conditions, such as the temperature, space velocity, and partial pressure of the methane were varied to understand their effect on the catalytic performance. With the LaCoO3-type catalyst, the partial substitution of Sr or Ba into site A enhanced the catalytic activity in the methane combustion. With the LaBO3(B=Co, Fe, Mn, Cu)-type catalyst, the catalytic activities were exhibited in the order of Co>Fe Mn>Cu. Futhermore, the partial substitution of Co into site B enhanced the catalytic activity, whereas an excess amount of Co decreased the activity. The surface area and catalytic activity of the perovskite catalysts prepared using the malic acid method showed higher values than those prepared using the solid reaction method. The catalytic activity was enhanced with decreased methane concentration and with a decrease in the space velocity.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.30 no.12 s.255
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• pp.1211-1217
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• 2006

This study is focused on oxidation prevention of STS430, which is generally used as solid oxide fuel cell(SOFC) interconnect at intermediate operating temperatures with oxidation-proof coatings. Inconel, $La_{0.6}Sr_{0.4}CoO_3(LSCo)$ and $La_{0.6}Sr_{0.4}CoO_3(LSCr)$ were chosen as coating materials. Using a radio frequency magnetron sputtering method, each target material was deposited as thin film on STS430 and was analyzed to find out favorable conditions. In this study, LSCr-coated STS430 can reduce electrical resistance to 1/3 level, compared with uncoated STS430. Also, long-term durability test at $700^{\circ}C$ for 1000 hours tells that LSCr thin layer performs an important role to prohibit serious degradations. Superior oxidation-resistant characteristic of LSCr-coated STS430 is attributed to the inhibition of spinel structure formation such as $MnCr_2O_4$.

• The Journal of the Petrological Society of Korea
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• v.18 no.2
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• pp.93-114
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• 2009

Lithological and petrochemical characteristics and tectonic setting of the Cretaceous volcanic rocks in Hampyeong area located in the southwestern part of Okchon Zone, were studied by field survey and petrochemistry of major, trace, and rare earth elements. The $SiO_2$contents of the volcanic rocks range from 50.8 to 77.2wt.%. With increasing $SiO_2$, $Al_2O_3$, $Fe_2O_3\;^T$, $TiO_2$, MnO, CaO and MgO contents decrease and $K_2O$content increase, but $Na_2O$content is scatter to the trend. According to TAS and AFM diagrams, the Cretaceous volcanic rocks are calc-alkaline series. On the discrimination diagram of $K_2O$versus $SiO_2$, the volcanic rocks belong to high-K rocks series. The trace element compositions and REE patterns of the volcanic rocks, characterized by a high LILE/HFSE ratio and enrichments in LREE, indicate that they are typical of continental margin arc calc-alkaline volcanic rocks associated with the subduction environment. The ratios of Ba/Ta and Ba/La indicate that they are associated with volcanic arc-related magmatism. The Cretaceous volcanic rocks in Hampyeong area might be located in the Eurasian continental margin, related to the Pacific type tectonic environment during the Cretaceous times.

• Journal of the Microelectronics and Packaging Society
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• v.15 no.1
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• pp.1-6
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• 2008

Thermoelectric properties of calcium cobalt layer structure oxide system, $Ca_3Co_2O_6$ and $Ca_3Co_4O_9$ were investigated at the temperature range of 300 to 1000K for the application of thermoelectric generation. In the composition, the Ca site was partially substituted with Bi, Sr, La, K and the Co site was partially substituted with Mn, Fe, Ni, Cu, Zn. The thermoelectric properties of Bi substituted $Ca_3Co_4O_9$. $Ca_{2.7}Bi_{0.3}Co_4O_9$ for electrical conductivity, Seebeck coefficient and power factor were $85.4({\Omega}$cm)^{-l}, $176.2{\mu}V/K$ and $265.2{\mu}W/K^m$, respectively. The unit thermoelectric couple was fabricated with the p-type of $Ca_{2.7}Bi_{0.3}Co_4O_9$ and n-type ($Zn_{0.98}Al_{0.02}$)O thermoelectrics whose figure-of-merit(Z) were $0.87{\times}10^{-4}/K$ and $0.41{\times}10^4/K$, respectively. The generated thermoelectric power was about 30mV at the temperature difference of 120K in the unit thermoelectric couple.

• Economic and Environmental Geology
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• v.25 no.1
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• pp.27-39
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• 1992

Several pyrophyllite deposits occur around the Milyang area where Cretaceous andesitic rocks and spatially related granitic rocks are widely distributed. Pyrophyllite ores consist mainly of pyrophyllite, and quartz with small amount of sericite, pyrite, dumortierite, and diaspore. The andesitic rocks and spatially related granitic rocks in this area suggest that they could be formed from the same series of a calc-alkaline magma series. The contents of $SiO_2$, $Al_2O_3$, LOI(loss on ignition) are enriched, and $K_2O$, $Na_2O$, CaO, MgO, $Fe_2O_3$ are depleted in altered andesitic rocks and ores. Enrichment of As, Cr, Sr, V, Sb and depletion of Ba, Cs, Ni, Rb, U, Y, Co, Sc, Zn are characteristic during mineralization. The pyrophyllite ores can be discriminated from the altered-and unaltered wall-rocks by an increasing of $(La/Lu)_{cn}$ from 4.18~22.13 to 8.98~55.05. In R-mode cluster analysis, Yb-Lu-Y, La-Ce-Hf-Th-U-Zr, $TiO_2-V-Al_2O_3$, Sm-Eu, $CaO-Na_2O-MnO$, Cu-Zn-Ag, $K_2O-Rb$ are closely correlated. In the discriminant analysis of multi-element data, $P_2O_5$, As, Cr and $Fe_2O_3$, Sr are helpful to identify the ores from the unaltered-and altered wall-rocks. In the factor analysis, the factors of alteration of andesitic rocks and ore mineralization were extracted. In the change of ions per unit volume, $SiO_2$, $Al^{3+}$ and LOI are enriched and $Na^+$, $K^+$, $Ca^{2+}$, $Mg^{2+}$, $Mn^{2+}$ and $Fe^{3+}$ are depleted during the alteration processes. The Milyang and the Sungjin pyrophyllite deposits could be mineralized by hydrothermal alteration in a geochemical condition of low activity ratio of alkaline ions to hydrogen ion with reference to spatially related granitic rocks.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.15 no.8
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• pp.671-677
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• 2002

In this study, the high frequency SMD ceramic resonators with the size of $3.7{\times}3.1{\times}0.385\textrm{mm}^3$ were fabricated using $Pb_{0.88}(La_{0.6}Nd_{0.4})_{0.08}(Mn_{1/3}Sb_{2/3})_{0.02}Ti_{0.98}O_3$ ceramics with the variations of electrode radius size. With increasing the electrode radius size, resonant resistance in third overtone mode was decreased and electromechanical coupling factor($k_{t3}$) in third overtone mode was showed constant values. Taking into consideration mechanical quality factor($Qm_{t3}$) of 5,552 and dynamic range(D.R) of 60.72dB in third overtone mode, the ceramic resonator with the electrode radius size of $\theta$1.13mm was suitable for 20MHz resonator application.

• Economic and Environmental Geology
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• v.22 no.2
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• pp.151-166
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• 1989

A study of rare-earth mineralization in Kyemyungsan metasedimentary formation of Precambrian Ogcheon Group was carried out in the Mt. Eore Area near Choongju City based on the thorium (Th) and uranium (U) count data of geophysical airborne survey. This rare-earth mineralization was found in the magnetite-bearing banded quartizite which contains diagnostically some amounts of the metamict allanite. The brown colored allanites are distributed as aggregates of fine grains and sometimes banded structures with magnetite (inter growth) along the banding. The ore bed is displaced by the small faults and granite intrusions, and separated 5 ore blocks. The dimensions of the outcrop are 50-80 m in width, 1,500 m in length with the strike of $N70-80^{\circ}E$ and dip of $50-80^{\circ}NW$. In the field, the values of total gamma ray count of GR-101A scintillometer were able to measure more than 400 cps and maximum 1,500 cps, which data are coincided with the values of GR-310 gamma ray spectrometer and the gamma ray count of well logging data. The chemical compositions of the allanites from EPMA data are ranged from$\sum^{TR_2O_3}$ 18.57% to 26.00%, and the cerium oxides ($Ce_2O_3$) of allanite are positive relation with $La_2O_3$, MgO, FeO, MnO and negative relation with $SiO_2$, $Al_2O_3$, $Nd_2O_3$. The result of Neutron Activation Analysis (N.A.A.), Multi-Channel Analysis (M.C.A.) and wet chemistry of 25 outcrop samples for the elements of REE, Zr, U, Th shows strong anomalies. The good correlation elements with the thorium (Th) are the elements of La, Ce, LREE, $TR_2O_3$, Pr, Sm, Yb, Lu by the increasing order.

• Journal of the Korean Ceramic Society
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• v.45 no.4
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• pp.232-237
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• 2008

As the single chamber SOFC(SC-SOFC) showed higher prospect on reducing the operation temperature as well as offering higher design flexibility of SOFCs, lots of concerns have been given to investigate the catalytic activity of perovskite-type oxide in mixed fuel and oxidant conditions. Hence we thoroughly investigated the catalytic property of various perovskite-type oxides such as $La_{0.8}Sr_{0.2}MnO_3(LSM),\;La_{0.6}Sr_{0.4}CoO_3(LSC),\;La_{0.6}Sr_{0.4}Co_{0.2}Fe_{0.8}O_3(LSCF),\;Sm_{0.5}Sr_{0.5}CoO_3(SSC),\;and\;Ba_{0.5}Sr_{0.5}Co_{0.8}Fe_{0.2}(BSCF)$ under the partial oxidation condition of methane which used to be given for SC-SOFC operation. In this study, powder form of each perovskite oxides whose surface areas were controlled to be equal, were investigated as functions of methane to oxygen ratios and reactor temperature. XRD, BET and SEM were employed to characterize the crystalline phase, surface area and microstructure of prepared powders before and after the catalytic oxidation. According to the gas phase analysis with flow-through type reactor and gas chromatography system, LSC, SSC, and LSCF showed higher catalytic activity at fairly lower temperature around $400^{\circ}C{\sim}450^{\circ}C$ whereas LSM and BSCF could be activated at much higher temperature above $600^{\circ}C$.