• 청정기술
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• 제26권4호
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• pp.286-292
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• 2020

본 연구는 Cu/CeO2-X 촉매의 저온 CO 산화 활성에 미치는 영향을 촉매의 구조적 특성, 반응 특성을 통해 확인하였다. 사용된 촉매는 습윤 함침법으로 제조되었으며, 각기 다른 소성온도(300~600 ℃)에서 형성된 CeO2 (지지체)를 이용하여 Cu (활성금속)를 담지함으로써 Cu/CeO2-X 촉매를 제조하였다. 제조된 Cu/CeO2-X 촉매는 저온 CO 산화 활성을 평가하였다. 125 ℃에서 Cu/CeO2_300 촉매는 90% 이상의 활성을 나타냈으며, CeO2의 소성온도가 증가됨에 따라 활성이 점차 감소하여, Cu/CeO2_600 촉매는 65%를 나타냈다. 다음으로 촉매의 물리/화학적 특성을 Raman, BET, XRD, H2-TPR, XPS 분석으로 확인하였다. XPS 분석 결과, CeO2-X의 소성온도가 낮을 수록 불안정한 Ce3+ 종(비 화학양론 종) 비율이 증가하였다. 증가된 Ce3+종은 Cu와 결합함으로 써 치환결합을 형성하였으며 Raman 분석의 CeO2 peak 변화와 H2-TPR 분석의 치환결합 구조의 환원 peak를 통해 확인하였다. 결과적으로 Cu와 CeO2의 치환 결합 형성은 촉매의 redox 특성 및 저온 CO 산화 활성을 증진시켰다고 판단된다.

• 한국세라믹학회지
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• 제34권2호
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• pp.139-144
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• 1997

결정학적으로 T' 구조인 Nd2-xCexCuO4-$\delta$ 회토류 구리산화물 초전도체는 지금까지 매우 복잡한 미세구조를 지닌 것으로써 잘 알려져 있다. 이 구리산화물 초전도체가 초전도 특성을 띠려면, Nd3+ 이온이 Ce4+ 이온에 의해 소량 치환되고 동시에 산소환원이 필요하다. 본 연구에서는 투과전자현미경의 수렴성 전자회절(CBED)패턴을 이용하여 Nd2-xCexCuO4-$\delta$ 의 Ce 미량 첨가와 미량의 산소환원에 따른 결정구조의 전이 발생 여부에 관하여 고찰하였다. 세 가지의 서로 다른 시편 Nd2CuO3,Nd1.85Ce0.15CuO4 와Nd1.85Ce0.15CuO3.965을 고상소결에 의하여 만들어 이들 각각 시편에 대한 CBED패턴을 주사투과전자현미경(STEM)으로 관찰하였다. 그리고 실험에 의하여 얻은 이들 HOLZ선들과 컴퓨터 계산에 의해 그려진 이론적인 HOLZ선들과 비교하는 방법에 의하여 Nd1.85Ce0.15CuO4의 격자상수를 구하였다.

• Progress in Superconductivity
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• 제11권1호
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• pp.67-71
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• 2009

The effect of Cu substitution on the structural and superconducting properties of the $(Ru_{1-x}Cu_x)Sr_2(Eu_{1.34{\cdot}}Ce_{0.66})Cu_2O_z$ system with x = 0, 0.25 and 0.5 prepared under ambient pressure have been investigated. The X-ray diffraction patterns indicated that the Ru ions are replaced by the Cu ions. It is found that the Cu substitution for Ru significantly reduces the ferromagnetic component of field-cooled magnetic susceptibility, but results in a small change in diamagnetic onset transition temperature of zero-field-cooled magnetic susceptibility. In contrast to the Ru $Sr_2(Eu_{1.34{\cdot}}Ce_{0.66})Cu_2O_z$, bulk Meissner effect is observed in the field-cooled magnetization measurements of the Cu doped samples. The experimental results are discussed in connection with the spontaneous vortex phase interpretation.

• 공업화학
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• 제23권3호
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• pp.348-351
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• 2012

본 연구에서는 NO의 저온 SCR 반응에서 구리 첨가가 $Mn/CeO_2-ZrO_2$ 촉매의 활성에 미치는 영향을 알아보았다. 이를 위하여 $Mn/CeO_2-ZrO_2$ 촉매에 구리가 각각 5, 10, 15 wt% 첨가된 세가지 촉매의 활성을 조사하였다. 촉매의 특성은 BET, XRD, XPS, $H_2-TPR$을 통해 분석하였다. 구리가 첨가된 촉매의 질소산화물 저감 효율을 측정한 결과 Cu 농도가 증가할수록 활성이 증가하였으며 Cu 15 wt%가 담지하였을 경우 질소산화물 저감효율이 99%까지 도달하는 등 가장 높은 저감효율을 나타내었다. 이는 표면의 망간과 구리의 interaction에 의한 환원의 향상이 촉매 효율 증가의 원인으로 여겨진다.

• Progress in Superconductivity
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• 제13권1호
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• pp.12-17
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• 2011

We investigated the effects of Ba and Cu co-substitution on the structural and superconducting properties of ($Ru_{1-y}Cu_y$)($Sr_{1.67-x}Ba_xEu_{0.33}$)($Eu_{1.34}Ce_{0.66}$)$Cu_2O_z$ samples. X-ray diffraction(XRD) reveals that single-phase samples can be obtained in the range from x = 0.1 to 0.2 for ($Ru_{0.5}Cu_{0.5}$)($Sr_{1.67-x}Ba_xEu_{0.33}$)($Eu_{1.34}Ce_{0.66}$)$Cu_2O_z$ and from y = 0.25 to 0.5 for ($Ru_{1-y}Cu_y$)($Sr_{1.47}Ba_{0.2}Eu_{0.33}$)($Eu_{1.34}Ce_{0.66}$)$Cu_2O_z$, respectively. All samples with compositions of ($Ru_{0.5}Cu_{0.5}$)($Sr_{1.67-x}Ba_xEu_{0.33}$) ($Eu_{1.34}Ce_{0.66}$)$Cu_2O_z$ (x = 0 - 0.33) show superconducting transition behavior and the onset transition temperature decreases slightly with increasing x in consistent with the change of hole concentration estimated from room temperature thermoelectric power measurements. The XRD and resistivity measurements for the ($Ru_{1-y}Cu_y$)($Sr_{1.47}Ba_{0.2}Eu_{0.33}$)($Eu_{1.34}Ce_{0.66}$) $Cu_2O_z$ system indicate that the partial substitution of Cu for Ru is necessary to form phase pure samples, but result in a small change in transition temperature in the single-phase region from x = 0.25 to 0.5.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2001년도 하계학술대회 논문집
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• pp.901-904
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• 2001

For the c-axis oriented epitaxial YBa$_2$Cu$_3$O$_{7-{\delta}}$ thin film on r-cut sapphire substrate it is necessary to deposit buffer layers. The CeO$_2$buffer layer was deposited on sapphire substrate using RF magnetron sputtering system. We investigated XRD pattern of CeO$_2$thin films at various sputtering conditions such as sputtering gas ratio, sputtering power, target to substrate distance, sputtering pressure and substrate temperature. The optimum condition was 15 mTorr with deposition pressure, 1:1.2 with $O_2$and Ar ratio and 9cm with target to substrate distance. The CeO$_2$(200) peak was notable for a deposition temperature above 75$0^{\circ}C$. The YBa$_2$Cu$_3$O$_{7-{\delta}}$ was deposited on CeO$_2$buffered r-cut sapphire substrate using pulsed laser ablation. The YBa$_2$Cu$_3$O$_{7-{\delta}}$CeO$_2$(200)/A1$_2$O$_3$thin film was exhibited a critical temperature of 89K.xhibited a critical temperature of 89K.

• 한국전기전자재료학회논문지
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• 제15권3호
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• pp.269-274
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• 2002

(Sm/Y)-Ba-Cu-O system high Tc composite superconductors with/without $CeO_2$ additive were directionally grown by zone-melting process, haying large temperature gradient, In air atmosphere. Cylindrical green rods of $({Sm/y})_{1.8}Ba_{2.4}Cu_{3.4}O_x$ [(Sm/Y)1.8] composite oxides by cold isostatic pressing(CIP) method using rubber mold were fabricated. The microstructure and superconducting properties were investigated by XRD, SEM, TEM and SQUID magnetometer. The size of nonsuperconducting $({Sm/y})_2BaCuO_5$ inclusions of the melt-textured (Sm/Y)1.8 sample with CeO$_2$ additive were remarkably reduced and uniformly distributed within the superconducting (Sm/Y)1.8 matrix. Both samples, with/without $CeO_2$ additive, showed an onset Tc $\geq$ 90 K and sharp superconducting transition. The critical current density Jc value of the $CeO_2$ addictive were $1{\times}10^5A/\textrm{cm}^2$ in 77 K, 0 Tesla.

• Progress in Superconductivity
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• 제13권3호
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• pp.163-168
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• 2012

The effects of Ta substitution on the superconducting and magnetic properties of the $(Ru_{1-x}Ta_x)Sr_2(Gd_{1.4}Ce_{0.6})Cu_2O_z(0{\leq}x{\leq}0.5)$ system have been investigated. The X-ray diffraction measurements indicate that the Ta ion replaces Ru sites up to x = 0.4. It is found that the Ta substitution for Ru significantly reduces the weak-ferromagnetic component of the field-cooled magnetic susceptibility without an appreciable change of room temperature thermopower at lower Ta doping level below x = 0.2. The resistive transition temperature tends to decrease monotonically from 27 K for the x = 0 sample to 16 K (9 K) for the x = 0.4 (x = 0.5) sample. These results suggest that superconductivity of the $(Ru_{1-x}Ta_x)Sr_2(Gd_{1.4}Ce_{0.6})Cu_2O_z$ compound is not significantly affected by the magnetic state of the Ru sublattice. The experimental results are discussed in connection with previous reports on the effects of Nb substitution.

• 한국전기전자재료학회논문지
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• 제29권2호
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• pp.110-113
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• 2016

(YNdSm)-Ba-Cu-O system high Tc composite superconductors were directionally grown by zone melting process, having large temperature gradient, in air atmosphere. Cylindrical green rods of $(YNdSm)_{1.8}Ba_{2.4}Cu_{3.4}O_x$ [(YNS)1.8]composite oxides by CIP (cold isostatic pressing) method using rubber mold were fabricated. The microstructure and superconducting properties were investigated by XRD, TEM and SQUID magnetometer. The size of nonsuperconducting $(YNdSm)_2BaCuO_5$ inclusions of the melt-textured (YNS)1.8 sample with $CeO_2$ additive were remarkably reduced and uniformly distributed within the superconducting (YNS)1.8 matrix. (YNS)1.8 samples, with / without $CeO_2$ additive, showed an onset $T_c{\geq}90K$ and sharp superconducting transition. The critical current density $J_c$ value of the (YNdSm)1.8 superconductor with $CeO_2$ additive were 840 A, $1.2{\times}104A/cm^2$ in 77 K, 0 Tesla by direct current transport method.

• 한국수소및신에너지학회논문집
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• 제31권1호
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• pp.57-64
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• 2020

The water-gas shift reaction for the compact reformer was carried out at a gas hourly space velocity of 72,152 h^-1 over the Cu-Nb-CeO₂ catalysts prepared by co-precipitation method. In order to investigate the effect of Nb₂O₅ promotion over a Cu-CeO₂ catalyst, the Nb₂O₅ loading amount was systematically changed from 0 to 5 wt.%. Among the prepared catalysts, the Cu-Nb-CeO₂ (1%) catalyst showed the highest catalytic activity (CO conversion=61% at 400℃) as well as 100% CO₂ selectivity. The high activity and stability of Cu-Nb-CeO₂ (1%) catalyst are correlated to high Brunauer-Emmett-Teller surface area, small metallic Cu crystallite size, and enhanced redox property.