• Bulletin of the Korean Chemical Society
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• 제34권11호
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• pp.3387-3390
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• 2013

Catalytic gasification of mandarin waste residue was carried out using direct and indirect catalyst-contact methods for the first time. In the indirect method, non-catalytic reaction in a reactor was followed by catalytic upgrading of vapor product in another reactor. Two different catalysts, $Ni/{\gamma}-Al_2O_3$ and $Ni/CeO_2-ZrO_2$, were employed. $CeO_2-ZrO_2$ support was prepared using hydrothermal synthesis in supercritical water. The catalysts were characterized by $H_2$-temperature programmed reduction and Brunauer-Emmett-Teller analyses. Under the condition of equivalent ratio (ER) = 0, the indirect catalyst-contact method led to a higher gas yield than the direct method. Under ER = 0.2, the yield of biogas obtained over $Ni/CeO_2-ZrO_2$ was higher than that obtained over $Ni/{\gamma}-Al_2O_3$. Also, the coke formation of $Ni/CeO_2-ZrO_2$ was lower than that of $Ni/{\gamma}-Al_2O_3$. Such results were attributed to the higher reducibility and better lattice oxygen mobility of $Ni/CeO_2-ZrO_2$, which were advantageous for partial oxidation reaction.

• 한국세라믹학회:학술대회논문집
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• 한국세라믹학회 2000년도 추계총회,초청강연,특별강연,연구발표회
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• pp.98.2-98
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• 2000

• 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.

• 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.

• 한국세라믹학회지
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• 제38권9호
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• pp.853-859
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• 2001

나노 $Y_2O_3-CeO_2$ 시스템의 분산안정성을 콜로이드 계면화학을 이용하여 조사하였다. 수계 슬립캐스팅으로 $Y_2O_3$가 첨가된 $CeO_2$의 성형체를 제조하였다. 분말과 유기첨가물 사이의 서스펜션의 분산안정성은 ESA를 이용한 서스펜션의 전기영동학적인 거동을 통하여 구하였다. 입자들의 이동도는 음이온계 분산제 1wt% 첨가 시 가장 크게 향상되었다. 산성영역에서의 $Y^{3+}$ 이온의 해리로 인해 슬러리의 수소이온 농도는 pH 7.0 이하로 내려가지 않았다. $Y_2O_3-CeO_2$ 시스템에서 서스펜션의 최적 조건은 음이온계 분산제를 1wt% 첨가하고 pH를 11.0으로 고정하는 것이고, 슬립캐스팅하여 1400$^{\circ}$C에서 2시간 소결하였다. 소결체는 98% 이상의 상대밀도를 나타내었으며, 표면 미세구조에서뿐만 아니라 단면의 깊이 방향에서도 Y원소의 분포가 균일하였다.

• 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.

• Current Applied Physics
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• 제18권12호
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• pp.1465-1472
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• 2018

The magnetic and optical properties of Ce-doped ZnO systems have been widely demonstrated, but the effects of different strains of Ce-doped ZnO systems remain unclear. To solve these problems, this study identified the effects of biaxial strain on the electronic structure, absorption spectrum, and magnetic properties of Ce-doped ZnO systems by using a generalized gradient approximation + U (GGA + U) method with plane wave pseudopotential. Under unstrained conditions, the formation energy decreased, the system became stable, and the doping process became easy with the increase in the distances between two Ce atoms. The band gap of the systems with different strains became narrower than that of undoped ZnO without strain, and the absorption spectra showed a red shift. The band gap narrowed, and the red shift became weak with the increase of compressive strain. By contrast, the band gap widened, and the red shift became significant with the increase of tensile strain. The red shift was significant when the tensile strain was 3%. The systems with -1%, 0%, and 1% strains were ferromagnetic. For the first time, the magnetic moment of the system with -1% strain was found to be the largest, and the system showed the greatest beneficial value for diluted magnetic semiconductors. The systems with -3%, -2%, 2%, and 3% strains were non-magnetic, and they had no value for diluted magnetic semiconductors. The ferromagnetism of the system with -1% strain was mainly caused by the hybrid coupling of Ce-4f, Ce-5d, and O-2p orbits. This finding was consistent with Zener's Ruderman-Kittel-Kasuya-Yosida theory. The results can serve as a reference for the design and preparation of new diluted magnetic semiconductors and optical functional materials.

• 한국세라믹학회지
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• 제29권6호
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• pp.451-458
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• 1992

Dense glass-ceramics for low firing temperature substrate were prepared by addition of CeO2 flux to the glass of MgO-Al2O3-SiO2 system. Glass powders were fabricated by melting at 150$0^{\circ}C$ and ball milling. Glass powder compacts were sintered at 800~100$0^{\circ}C$ for 3h. The crystallization and the shrinkage behaviors of glass powder compacts were analyzed by XRD, DTA and TMA. The shrinkage of glass powder compact increased with increasing the amount of CeO2. Because the softening temperature decreased and the crystallization temperature increased with increasing the amount of CeO2. Apparently, addition of CeO2 prevented formation of $\mu$-cordierite phase from the glass-ceramics and improved formation of $\alpha$-cordierite phase. Therefore crystallization properties were enhanced.

• 한국세라믹학회:학술대회논문집
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• 한국세라믹학회 2003년도 추계총회 및 연구발표회 초록집
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• pp.133.2-133
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• 2003

• 한국세라믹학회지
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• 제36권1호
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• pp.69-76
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• 1999

BaCeO3 페롭스카이트 구조의 Ce4+ 자리에 3가의 양이온 (La3+, Yb3+, Al3+)을 10 mol% 첨가하여 열처리한 후 전기적 특성을 관찰하였다. 전기전도도 측정 결과 모든 조성에서 질소분위기에서 측정한 경우보다 대기 중에서 측정한 경우의 전기전도도가 높게 측정되었으며 이러한 경향은 온도가 높아질수록 두드러졌다. 전기전도도는 BaCe0.9Yb0.1O3-$\delta$조성에서 가장 높았고 BaCe0.9Al0.9O3-$\delta$ 조성에서 가장 낮았다. proton의 수송율(transference number)을 기전력 측정법을 통해 비교한 결과 Al을 첨가한 조성에서 모든 온도에 걸쳐 가장 높은 proton의 수송율을 얻을 수 있었다.