• Korean Journal of Materials Research
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• v.11 no.1
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• pp.44-47
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• 2001

Effects of $Er_2O_3$ addition on the dielectric properties of non-reducible $BaTi_3$-based X7R dielectrics with Ni electrode have been studied in reducing atmosphere. X7R with moderate temperature-dependence was developed after addition of $Er_2O_3$ with $MnO_2-MgO$; room-temperature dielectric constant and dissipation factor were >2900 and < 1.0%, respectively. The addition of $Er_2O_3$ greater than 3.0 mol% improved the temperature dependence of dielectric properties, but a significant decrease of the dielectric constant at room-temperature was observed. The TCC curves rebated clockwise with increasing MnO$_2$ content at a given additive system, 1.5 mol% $Er_2O_3$ and 2.0 mol% MgO.

• Bulletin of the Korean Chemical Society
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• v.26 no.10
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• pp.1512-1514
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• 2005

Catalytic properties of Ni-Zr$O_2$ catalysts prepared by coprecipitation have been studied for the gas-phase hydrogenation of 1,3-butadiene to butenes. The coprecipitation method led to the solid solution of Ni-Zr$O_2$, which contains highly resistant Ni species to thermal reduction with H2. Nickel species of the solid solution were highly dispersed in the ZrO2 lattice, so that the reduced catalysts were selective for hydrogenation of 1,3-butadiene to butenes (99.9%) even in the presence of 1-butene.

• Journal of Hydrogen and New Energy
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• v.23 no.6
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• pp.670-677
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• 2012

Perovskite-type oxides such as doped barium zirconate ($BaZrO_3$) show high proton conductivity and chemical stability when they are exposed to hydrogen and water vapour containing atmospheres, thus it can be applicable to the hydrogen separation and the fuel cell electrolyte membranes. However the high temperature ($1700-1800^{\circ}C$) and long sintering times (24h) are generally required to prepare the fully densified $BaZrO_3$ pellets. These sintering conditions lead to the limitation of the grain size growth and the degradation of conductivity due to the acceleration of BaO evaporation at $1200^{\circ}C$. Here we demonstrate NiO-doped $BaZr_{0.85}Y_{0.15}O_{3-{\delta}}$ with lower calcination and sintering temperature, less experimental procedure and lower process cost than the conventional mixing method. The stoichiometry of $BaZr_{0.85}Y_{0.15}O_{3-{\delta}}$ was optimized by the control of excess amount of Ba (5mol%) to minimized BaO evaporation. We found that the crystal size of NiO-doped $BaZr_{0.85}Y_{0.15}O_{3-{\delta}}$ was increased with increase of calcination temperature from XRD analysis. NiO-doped $BaZr_{0.85}Y_{0.15}O_{3-{\delta}}$ powder was calcined at $1000^{\circ}C$ for 12h when its showed the highest conductivity of $3.3{\times}10^{-2}s/cm$.

• Journal of Hydrogen and New Energy
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• v.23 no.3
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• pp.213-218
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• 2012

Steam reforming of methane (SRM) is the primary method to produce hydrogen. Commercial Ni-based catalysts have been optimized for SRM with excess steam ($H_2O/CH_4$ > 2.5) at high temperatures (> $700^{\circ}C$). However, commercial catalysts are not suitable under severe conditions such as stoichiometric steam over methane ratio ($H_2O/CH_4$ = 1.0) and low temperature ($600^{\circ}C$). In this study, 15wt.% Ni catalysts supported on $Ce_{0.8}Zr_{0.2}O_2$ were prepared at various calcination temperatures for SRM at a very high gas hourly space velocity (GHSV) of $621,704h^{-1}$. The calcination temperature was systematically varied to optimize 15wt.% $Ni-Ce_{0.8}Zr_{0.2}O_2$ catalyst at a $H_2O/CH_4$ ratio of 1.0 and at $600^{\circ}C$. 15wt.% $Ni-Ce_{0.8}Zr_{0.2}O_2$ catalyst calcined at $500^{\circ}C$ exhibited the highest $CH_4$ conversion as well as stability with time on stream. Also, 15wt.% $Ni-Ce_{0.8}Zr_{0.2}O_2$ catalyst calcined at $500^{\circ}C$ showed the highest $H_2$ yield (58%) and CO yield (21%) among the catalysts. This is due to complex NiO species, which have relatively strong metal to support interaction (SMSI).

• 한국전기화학회:학술대회논문집
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• 2002.04a
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• pp.46-46
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• 2002

• 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.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1996.11a
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• pp.59-62
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• 1996

The effect of NiO addition on the microstructure and microwave dielectric properties of (Zr$_{0.8}$Sn$_{0.2}$)TiO$_4$(ZST) was investigated. With the NiO addition, a dense ZST body of density higher than 95% has been achieved in the sintering temperature range of 1400 to 150$0^{\circ}C$. Energy dispersive X-ray spectrometry (EDS) analysis of sintered specimen shows the presence of second phase at grain boundaries, which is considered to be NiTiO$_3$. Dielectric constant of the specimen is found to increase linearly with density. Q-values and TC$_{f}$decrease with increasing NiO content. The variation of dielectric properties with NiO content is discussed in term of the second phase. The ZST ceramics with small amount of additive gave $\varepsilon$$_{r}$=38, Q=7000 at 7 GHz and TC$_{f}$=-0.5 ppm/$^{\circ}C$, comparable with the values obtained by previous investigation.stigation.

• Proceedings of the Materials Research Society of Korea Conference
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• 2001.05a
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• pp.23-23
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• 2001

• Proceedings of the Materials Research Society of Korea Conference
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• 2001.11a
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• pp.18-18
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• 2001

• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 1994.04c
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• pp.16-17
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• 1994