• Transactions of Materials Processing
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• v.7 no.5
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• pp.481-488
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• 1998

The active metal brazing was applied to bond Alumina and Ni-Cr steel by Ag-Cu-Zr-Sn alloy and the interfacial microstructure and reaction mechanism were investigated. Polycrystalline monoclinic $ZrO_2$ with a very fine grain of 100-150 nm formed at the alumina grain boundary contacted with Zr segregation layer at the interface. The $ZrO_2$ layer containing the inclusions and cracks were developed at the boundary of inclusion/$ZrO_2$ due to the difference in specific volume. The development of $ZrO_2$ at the interface was successfully explained by the preferential penetration of $ZrO_2$ at the interface was successfully explained by the preferential penetration of Zr atoms a higher concentration of oxygen and a high diffusion rate of Al ions into molten brazing alloy.

• Proceedings of the Materials Research Society of Korea Conference
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• 2003.03a
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• pp.221-221
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• 2003

• Bulletin of the Korean Chemical Society
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• v.34 no.7
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• pp.2073-2080
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• 2013

In this study the effects of adding alkaline-earth (IIA) metal oxides to NiZr-loaded Zeolite Y catalysts were investigated on hydrogen rich production by ethanol steam reforming (ESR). Four kinds of alkaline-earth metal (Mg, Ca, Sr, or Ba) oxides of 3.0% by weight were loaded between the $Ni_6Zr_4O_{14}$ main catalytic species and the microporous Zeolite Y support. The characterizations of these catalysts were examined by XRD, TEM, $H_2$-TPR, $NH_3$-TPD, and XPS. Catalytic performances during ESR were found to depend on the basicity of the added alkaline-earth metal oxides and $H_2$ production and ethanol conversion were maximized to 82% and 98% respectively in 27($Ni_6Zr_4O_{14}$)3MgO/70Zeolite Y catalyst at $600^{\circ}C$. Many carbon deposits and carbon nano fibers were seen on the surface of $30Ni_6Zr_4O_{14}$/70Zeolite Y catalyst but lesser amounts were observed on alkaline-earth metal oxide-loaded 27($Ni_6Zr_4O_{14}$)3MO/70Zeolite Y catalysts in TEM photos after ESR. This study demonstrates that hydrogen yields from ESR are closely related to the acidities of catalysts and that alkaline-earth metal oxides reduce the acidities of 27($Ni_6Zr_4O_{14}$)3MO/70Zeolite Y catalysts and promote hydrogen evolution by preventing progression to hydrocarbons.

• Korean Chemical Engineering Research
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• v.51 no.1
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• pp.47-52
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• 2013

In this study, the catalytic performance and characterization of $Ni/Ce_xZr_{1-x}O_2$ were investigated using an autothermal reforming (ATR) process for hydrogen production. The $Ni/Ce_xZr_{1-x}O_2$ catalysts were prepared using the following methods: the water method (CZ-W), urea water method (CZ-UW) and urea, water and ethanol method (CZ-UWA). The performance of $Ni/Ce_xZr_{1-x}O_2$ catalysts in autothermal reforming of propane for hydrogen production was studied in a fixed-bed flow reactor. Reaction tests were conducted by using a feed of $H_2O/C_3H_8/O_2$=3/1/0.37 and $300{\sim}700^{\circ}C$. The CZ-UW and CZ-UWA catalysts showed higher propane conversion and hydrogen yield than the CZ-W catalyst. The activity test confirmed that the improvement in the water-ethanol catalyst was due to the low level of carbon deposition. SEM showed that the surface carbon consisted of clusters on the used CZ-UW catalyst, which is incontrast to the nano-fiber morphology observed on the used CZ-UWA catalyst. It was found that the amount of carbon deposition depends on the preparation method. Especially the $Ni/Ce_{0.75}Zr_{0.25}O_2$ was showed higher propane conversion and hydrogen yield than the other catalysts. Also TGA showed that the resistance of carbon deposition increase to Co addition.

• Transactions of the Korean hydrogen and new energy society
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• v.25 no.2
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• pp.105-113
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• 2014

Performance tests on $Ni/Ce-ZrO_2/Al_2O_3$ catalysts with additives (MgO, $La_2O_3$) were investigated in the combined reforming processes (SCR, ATR, TRM) in order to produce hydrogen and carbon monoxide (it is called "syngas".). The catalyst characterization was conducted using the BET surface analyzer, X-ray diffraction (XRD), SEM, TPR and TGA. The combined reforming process was developed to adjust the syngas ratio depending on the synthetic fuel (methanol, DME and GTL) manufacturing processes. Ni-based catalysts supported on alumina has been generally recommended as a combined reforming reaction catalyst. It was found that both free NiO and complexed NiO species were responsible for the catalytic activity in the combined reforming of methane conversion, and the $Ce-ZrO_2$ binary support employed had improved the oxygen storage capacity and thermal stability. The additives, MgO and $La_2O_3$, also seemed to play an important role to prevent the formation of the carbon deposition over the catalysts. The experimental results were compared with the equilibrium data using a commercial simulation tool (PRO/II).

• Transactions of the Korean hydrogen and new energy society
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• v.14 no.1
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• pp.1-7
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• 2003

In this study, activity changes of $Ni/Ce-ZrO_2$ catalyst for steam reforming reaction in the various steam treatment condition were investigated and BET, XRD and XPS analysis were introduced to characterize the catalyst before and after treatment. Activity test showed that $Ni/Ce-ZrO_2$ catalyst had good activity after reduction in steam reforming reaction but deactivated rapidly after steam treatment at high temperature. Activities of deactivated catalyst by steam was recovered to die previous activity level after reduction using hydrogen rich gas. It was observed that catalytic activity was preserved after repeated steam treatment, too. It showed that change of catalytic activity due to steam treatment is perfectly reversible. From the BET, XRD and XPS analysis, deactivation of $Ni/Ce-ZrO_2$ catalyst was due to the transition from Ni, that is activity site for steam reforming reaction, to $NiAl_2O_4$ in steam treatment at high temperature.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2005.11a
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• pp.169-170
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• 2005

본 연구에서는 초음파 센서에 응용 가능한 $0.4Pb(Ni_{1/3}Nb_{2/3})O_3-0.6Pb(Zr_xTi_{1-x})O_3+0.5Wt%$ $MnO_2$ 세라믹스에 Zr/(Ti+Zr)비를 0.37에서 0.41로 변화시킨 조성을 1175 $\sim$ 1200$^{\circ}C$ 온도에서 소결하여 이의 결정구조 및 미세조직을 분석하였고, 압전, 유전 특성을 고찰하였다. 본조성에서 x=0.385 조성에서 최대 유전상수 값 3490 이 나타났으며, 그 이상의 첨가에서는 감소하였다. 상경계 영역인 x=0.385 조성에서 $\varepsilon$r, $K_p$, $d_{33}$ 값이 최대값을 나타내었다. $0.4Pb(Ni_{1/3}Nb_{2/3})O_3-0.6Pb(Zr_xTi_{1-x})O_3+0.5Wt%$ $MnO_2$, 세라믹스에서는 kp 와 $d_{33}$ 는 Zr/(Ti+Zr)비 0.385조성까지 증가하였다가 그 이상 조성에서 감소하였다. $1175^{\circ}C$에서 2시간 소결한 x=0.385조성에서 $\varepsilon$r=3490, kp=0.71, Qm=476의 우수한 압전 특성을 나타내었다.

• Journal of the Korean Ceramic Society
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• v.31 no.10
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• pp.1197-1201
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• 1994

The fracture strength and fracture modes were studied in 3Y-TZP/NiNi bonding which change their interfacial structure with bonding condition. Average 4-point bending strength of 200 MPa to 400 MPa were achieved. The formation of Ti-oxide phase at the interface critically influenced the bonding strength and fracture mode. The fracture surface of Ti-oxide free interface contained multiphase in some case including ZrO2. From the result it was confirmed that in order to maximize the bonding strength crack deflection from interface to ceramic was required.

• Bulletin of the Korean Chemical Society
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• v.26 no.5
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• pp.755-762
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• 2005

A series of catalysts, NiO/$CeO_2-ZrO_2/WO_3$, for ethylene dimerization was prepared by the precipitation and impregnation methods. For NiO/$CeO_2-ZrO_2/WO_3$ sample, no diffraction line of nickel oxide was observed up to 40 wt%, indicating good dispersion of nickel oxide on the surface of catalyst. The hexagonal and monoclinic phases of $WO_3$ up to the calcination temperature of 500 ${^{\circ}C}$ were observed, whereas the hexagonal phase of WO3 completely was transformed into monoclinic phase of $WO_3$ at 600 ${^{\circ}C}$ and above. The role of $CeO_2$ in the catalysts was to form a thermally stable solid solution with zirconia and consequently to give high surface area and acidity. The catalytic activities for ethylene dimerization were correlated with the acidity of catalysts measured by the ammonia chemisorption method. 25-NiO/5-$CeO_2-ZrO_2/15-WO_3$ containing 25 wt% NiO, 15 wt% $WO_3$ and 5 mol% $CeO_2$, and calcined at 400 ${^{\circ}C}$ exhibited a maximum catalytic activity due to the effects of $WO_3$ modifying and $CeO_2$ doping.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2005.07a
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• pp.338-339
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• 2005

본 연구에서는 $Fe_2O_3$를 첨가한 $Pb(Ni_{1/3}Nb_{2/3})O_3-Pb(Zr_xTi_{1-x})O_3$ 세라믹스에서 Zr/Ti 비 변화에 따른 소결 및 압전, 유전특성을 조사하였다. $0.4Pb(Ni_{1/3}Nb_{2/3})O_3-0.6Pb(Zr_xTi_{1-x})O_3$+0.25Wt% $Fe_2O_3$ 계에서 Zr/(Ti+Zr)비(x)를 0.39에서 0.42까지 변화시킨 조성을 1100 - $1250^{\circ}C$ 온도에서 2시간 소결하여 이의 결정구조 및 미세조직을 분석하였고, 압전, 유전 특성 및 RAINBOW 액츄에이터로의 응용을 조사하였다. $1150^{\circ}C$에서 소결한 0.405 조성(x)에서 유전상수(${\varepsilon}r$) = 4669, 전기기계결합계수(kp) = 0.75, 압전상수($d_{33}$) = 810 pC/N의 우수한 특성 값을 나타내었으며, 닥터블레이드법에 의해 RAINBOW 액츄에이터를 제작하여 변위특성을 조사하였다.