• Proceedings of the Materials Research Society of Korea Conference
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• 1996.11a
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• pp.170-170
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• 1996

• Progress in Superconductivity
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• v.10 no.2
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• pp.128-132
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• 2009

Polycrystalline samples of $(Ru_{0.8}Nb_{0.2})Sr_2(Gd_{1.5-x}Nd_xCe_{0.5})Cu_2O_z$($ 0{\leq}x{\leq}1.25$) have been synthesized by a solid-state reaction route. The X-ray diffraction data revealed that the Nd solubility limit can be placed between x=0.5 and x=0.75. The superconducting transition temperature decreased with increasing Nd content, confirming that Nd entered the lattice. Room-temperature thermoelectric power measurements showed that all the samples are in the underdoped state and the partial substitution of Nd for Gd resulted in a decrease in the carrier density on the superconducting layers.

• Applied Chemistry for Engineering
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• v.30 no.5
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• pp.620-626
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• 2019

In this study, the effects of the structural properties of the catalyst on CO oxidation reaction by controlling the $Cu/CeO_2$ catalyst amount and calcination temperature were studied, and also the CO conversion rate of the catalyst at the temperature range of $100{\sim}300^{\circ}C$ was evaluated. XRD, Raman, BET, $H_2-TPR$, and XPS analyses were performed to confirm the effect of changes in the structural properties on the chemical properties of the catalyst. The result confirmed that a substitution bond between Cu and Ce was formed and a lot of Cu and Ce bonds were formed when the catalyst carrying 5 wt.%. Of Cu was calcined at $400^{\circ}C$. The Cu-Ce binding was confirmed by peak shifts in Raman analysis and also peaks appeared in $H_2-TPR$. In addition, the balance state analysis demonstrated that a lot of surface labile oxygen molecules are formed, which can be more easily contributed to the reaction with $Ce^{3+}$ species known to form a substitution bond easily. It was found that CO conversion rate of the catalyst used in this study was close to 100% at $150^{\circ}C$.

• 한국태양에너지학회:학술대회논문집
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• 2012.03a
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• pp.260-266
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• 2012

Syngas and hydrogen from the $CeO_2/ZrO_2$ coated foam devices were investigated under simulated solar radiation. The $CeO_2/ZrO_2$ coated SiC, Ni and Cu foam device were prepared using drop-coating method. Syngas production step was performed at $900^{\circ}C$, and hydrogen production process was performed for ten repeated cycles to compare the CeO2 conversion in syngas production step, $H_2$ yield in hydrogen production step and cycle reproducibility. The produced syngas had the $H_2$/CO ratio of 2, which was suitable for methanol synthesis or Fischer-Tropsch synthesis process. In addition, syngas and hydrogen production process is one of the promising chemical pathway for storage and transportation of solar heat by converting solar energy to chemical energy. After ten cycles of redox reaction, the $CeO_2/ZrO_2$ was analyzed using XRD pattern and SEM image in order to characterize the physical and chemical change of metal oxide at the high temperature.

• Journal of Powder Materials
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• v.8 no.3
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• pp.197-200
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• 2001

Modified inert gas condensation method was used to produce the nanocluster composites of $CuO/CeO_2$. High-resolution TEM, SEM and catalytic measurements have been used to characterize the samples and study the synergistic effect between the CuO phase and $CeO_2$(ceria) support. By varying the He pressure, the heating temperature and configuration of the heating boats inside the modified gas condensation chamber, nanoclusters of varying sizes, shapes and composition can be produced. The composition and nanostructured morphology were shown to influence the catalytic properties of the system. A copper content around 10 at% with a morphology that favors high-energy surfaces of ceria is shown to be beneficial for a high catalytic activity.

• Proceedings of the Korea Crystallographic Association Conference
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• 2003.05a
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• pp.12-12
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• 2003

초전도 선재로의 응용을 위하여 Pulsed laser deposition(PLD)법으로 고온 초전도 체 YBa₂Cu₃O/sub 7-δ/(YBCO) coated conductor를 제조하였다. coated conductor는 금속기판/완충층/초전도층의 구조를 이루고 있는데 완충층은 금속 기판의 집합조직을 초전도층까지 전달하는 역할과 금속기판의 금속이 초전도층으로 확산되어 초전도층의 전기적 특성을 열화시키는 것을 막아주는 확산장벽으로의 역할 등을 수행한다. 완충층의 박막 성장이 제대로 이루어지지 않으면 우수한 초전도 특성을 가지는 초전도층을 얻을 수 없다. 완충층은 금속기판과의 lattice match, thermal match등이 요구되고, 화학적으로 금속기판 및 초전도층과 반응하지 않아야 하며, 긍속기판의 산화없이 epitaxial하게 박막증착이 이루어질 수 있는 재료이어야 한다. 이러한 조건을 만족하는 YBCO, CeO₂, YSZ 등이 주로 사용되고 있다. 전기연구원에서 YBCO coated conductor 선재를 제조하기 위하여 사용하고 있는 다층 박막의 구조는 YBCO/CeO₂/YSZ/CeO₂/Ni(002)과 YBCO/CeO₂/YSZ/Y₂O₃/Ni(002)이며, 최적의 증착조건을 찾기 위하여 성장시 챔버의 산소분압, 완충층의 두께, 기판 온도 등을 변화시켰다. 증착된 완충층 및 초전도층의 집합 조직은 D8-Discover with GADDS(General Area Detector Diffraction System)로 XRD분석을 했고, 미세구조는 SEM으로 관찰하였으며 4단자법을 이용하여 초전도 특성을 측정하였다.

• Carbon letters
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• v.9 no.4
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• pp.303-307
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• 2008

The studies on integrated operation of fuel cell with fuel processor are very essential prior to its commercialization. In this study, Polymer Electrolyte Membrane Fuel Cell (PEMFC) was operated with a fuel processor, which is mainly composed of two parts, methanol steam reforming reaction and preferential oxidation (PROX). In fuel processor, ICI 33-5 (CuO 50%, ZnO 33%, $Al_2O_3$ 8%, BET surface area: $66\;m^2g^{-1}$) catalyst and CuO-$CeO_2$ catalyst were used for methanol steam reforming, preferential oxidation (PROX) respectively. PEMFC was operated by hydrogen fuel generated from fuel processor. The resulting gas from PROX reactor is used to operate PEMFC equipped with our prepared anode and cathode catalyst. PtRu/C catalyst gives more tolerance to CO.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2005.11a
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• pp.178-180
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• 2005

In this study, in order to develop multilayer low temperature sintering piezoelectric transformer, $Pb_{0.97}Sr_{0.03}[(Mn_{1/3}Nb_{2/3})x(Zr_{0.48}Ti_{0.52})_{1-x}O_3]+$ 0.25wt% $CeO_2$+0.3 wt% $Nb_2O_5$ system ceramics were fabricated using $Li_2CO_3-CaCO_3$ and CuO as sintering aids and their piezoelectric and dielectric characteristics were investigated with the amount of PMN substitution. With increasing PMN substitution, electromechanical coupling factor kp and dielectric constant were increased.

• Journal of Korean Society of Environmental Engineers
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• v.28 no.4
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• pp.368-375
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• 2006

Single and complex metal oxide catalysts supported onto a commercial DT51D $TiO_2$ have been investigated for gas-phase TCE oxidation in a continuous flow type fixed-bed reaction system to develop a better design approach to catalysts for this reaction. Among the $TiO_2$-supported single metal oxides used, i.e., $CrO_x,\;FeO_x,\;MnO_x,\;LaO_x,\;CoO_x,\;NiO_x,\;CeO_x\;and\;CuO_x$, with the respective metal contents of 5 wt.%, the $CrO_x/TiO_2$ catalyst was shown to be most active for the oxidative TCE decomposition, depending significantly on amounts of $CrO_x\;on\;TiO_2$. The use of high $CrO_x$ loadings greater than 10 wt.% caused lower activity in the catalytic TCE oxidation, which is probably due to production of $Cr_2O_3$ crystallites on the surface of $TiO_2$. $CrO_x/TiO_2$-supported $CrO_x$-based bimetallic oxide catalysts were of particular interest in removal efficiency for this TCE oxidation reaction at reaction temperatures above $200^{\circ}C$, compared to that obtained with $CrO_x$-free complex metal oxides and a 10 wt.% $CrO_x/TiO_2$ catalyst. Catalytic activity of 5 wt.% $CrO_x-5$ wt.% $LaO_x$ in the removal reaction was similar to or slightly higher than that acquired for the $CrO_x$-only catalyst. Similar observation was revealed for 5 wt.% $CrO_x$-based bimetallic oxides consisting of either 5 wt.% $MnO_x,\;CoO_x,\;NiO_x\;or\;FeO_x$. These results represent that such $CrO_x$-based bimetallic systems for the catalytic TCE oxidation on significantly minimize the usage of $CrO_x$ that is well known to be one of very toxic heavy metals, and offer a very useful technique to design new type catalysts for reducing chlorinated volatile organic substances.

• Journal of Surface Science and Engineering
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• v.29 no.5
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• pp.430-436
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• 1996

We have grown superconducting thin films on various substrates using a pulsed laser deposition (PLD) method. $YBa_2Cu_3O_7-\delta$ (YBCO) superconducting thin films with the superconducting transition temperature ($T_{c. offset}$) of 87K were grown on Si substrates using yittria-stabilized zirconia (YSZ) and $CeO_2$ double buffer layers. We have developed a large area pulsed laser deposition system. The system was designed to deposit up to 6 different materials on a large area substrate up to 7.5cm in diameter without breaking a vacuum. The preliminary runs of the deposition of YBCO superconducting thin films on $SrTiO_3$ substrate using this system showed a very uniform thickness profile over the entire substrate holder area. $T_{c}$ of the deposited YBCO thin film, however, was scattered depending on the position and the highest value was 85K.