• Title/Summary/Keyword: $CeO_2$ powder

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Effect of Ce$O_2$ Addition and Powder Treatment on the Sintering of U$O_2$ Powder (Ce$O_2$첨가 및 분말처리가 U$O_2$ 분말의 소결에 미치는 영향)

  • Kim, Hyeong-Su;Lee, Yeong-U;Choe, Chang-Beom;Yang, Myeong-Seung;Jeon, Pung-Il
    • Korean Journal of Materials Research
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    • v.3 no.3
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    • pp.245-252
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    • 1993
  • We investigated the changes of (U, Ce)$O_2$ powder characteristics with $CeO_2$ contents and ball-milling time and then studied on the sintering properties with those (U, Ce)$O_2$ powder characteristics. From the results of this study, it was concluded that the longer ball-milling time of (U, Ce)$O_2$ powder was, the finer its particle size was. Green and sintered densities were decreased with $CeO_2$ contensts increase. And also $CeO_2$ was recongized deteriorating oxide on the $UO_2$ sintering. In case of the lOwt. % $CeO_2$ contents, (U, Ce)$O_2$ sintered pellet which was made of ball-milled powder for 4 hours had few pores and its pores got near to the sphere. And its sintered density had the highest. Because its powder had higher surface area and its packing ratio was appropriated much better than others.

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Preparation of Ce0.8Gd0.2O1.9 Powder by Milling of CeO2 Slurry and Oxalate Precipitation (CeO2 슬러리 분쇄와 옥살산 침전을 이용한 Ce0.8Gd0.2O1.9 분말의 합성)

  • Sim, Soo-Man
    • Journal of the Korean Ceramic Society
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    • v.47 no.2
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    • pp.183-188
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    • 2010
  • $Ce_{0.8}Gd_{0.2}O_{1.9}$(GDC20) powder was synthesized by milling of $CeO_2$ slurry and Gd oxalate precipitation. The mixture of $CeO_2$ powder and Gd precipitates calcined at $600^{\circ}C$ for 2 h showed the particle size distribution similar to that of $CeO_2$ powder, which had been milled during the synthesis process. Attrition milling of the calcined powder with an average particle size of $0.36\;{\mu}m$ for 2 h resulted in a decrease in the particle size to $0.24\;{\mu}m$. Although the milled powder consisted of small particles(<$1\;{\mu}m$), a small amount of fine platy $Gd_2O_3$ particles, which had been survived in the milling process, was observed. Sintering of the powder compacts for 4 h showed relative densities of 80.7% at $1300^{\circ}C$ and 97% at $1400^{\circ}C$, respectively. Densification was found to almost complete at $1500^{\circ}C$, resulting in a dense and homogeneous microstructure with a relative density of 99.5%.

Synthesis of Nano Size $BaCeO_3$ as an Effective Flux Pining Center for YBCO Superconductor (YBCO 초전도체의 효과적인 플럭스 피닝 센터로서의 나노 크기 $BaCeO_3$ 합성)

  • Youn, J.S.;No, K.S.;Kim, Y.H.;Jun, B.H.;Lee, J.P.;Jung, S.Y.;Kim, C.J.
    • Progress in Superconductivity
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    • v.10 no.1
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    • pp.12-16
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    • 2008
  • In this work, nano size $BaCeO_3$, which is a possible flux pinning medium of melt processed $YBa_{2}Cu_{3}O_x$ superconductor, was synthesized by the conventional solid state reaction method using powders. $BaCeO_3$ and $CeO_2$ were mixed thoroughly using a ball milling for 24 hours and calcined at $1200^{\circ}C$ for 5 hours for the formation $BaCeO_3$ powder. The obtained $BaCeO_3$ powder was attrition milled at various milling times of 60 min, 120 min and 240 min. The $BaCeO_3$ powders of various milling times were mixed with $YBa_{2}Cu_{3}O_x$ powder. Seed melt processed $YBa_{2}Cu_{3}O_x$-$BaCeO_3$ (15wt.%) superconductors were prepared and the superconducting properties were investigated. It was found that $T_c$ of $Y_{1.5}Ba_{2}Cu_{3}O_x$ samples was not significantly affected by $BaCeO_3$ addition, but $J_c$ of samples was increased by $BaCeO_3$ addition. The $J_c$ improvement by fine $BaCeO_3$ powder (120 min attrition-milled) was effective at low magnetic fields less than 2 T.

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Preparation of Ce0.8Gd0.2O1.9 Powder Using CeO2 Powder and Gd Precipitation and Effect of CoO doping on Sintering

  • Sim, Soo-Man
    • Journal of the Korean Ceramic Society
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    • v.52 no.6
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    • pp.521-526
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    • 2015
  • $Ce_{0.8}Gd_{0.2}O_{1.9}$(GDC20) powder was prepared from a mixture of submicron-sized $CeO_2$ powder and Gd precipitates using ammonium carbonate $((NH_4)_2CO_3)$ as a precipitant. The mixture was calcined at $700^{\circ}C$ for 4 h followed by ball-milling that resulted in the GDC powder with an average particle size of $0.46{\mu}m$. The powder had a very uniform particle size distribution with particle sizes ranging from $0.3{\mu}m$ to $1{\mu}m$. Sintering of undoped GDC samples did not show a relative density of 99.2% until the temperature was increased to $1500^{\circ}C$, whereas GDC samples doped with 5 mol% CoO exhibited a significant densification at lower temperature reaching a relative density of 97.6% at $1100^{\circ}C$ and of 98.8% at $1200^{\circ}C$.

Synthesis and Characterization of Cordierite Glass-Ceramics for Low Firing Temperature Substrate: (I) Crystallization and Shrinkage Behavior of $MgO-Al_2O_3-SiO_2$ Glass Powders (저온소결 세라믹 기판용 Cordierite계 결정화유리의 합성 및 특성조사에 관한 연구: (I) $MgO-Al_2O_3-SiO_2$계 유리분말의 결정화 및 수축거동)

  • 이근헌;김병호;임대순
    • Journal of the Korean Ceramic Society
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    • v.29 no.6
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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.

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The Characteristics of YAG:Ce Phosphor Powder Prepared Using a NO3--Malonic Acid-NH4NO3-NH3·H2O System

  • Jeong, Jin-An;Park, Kyung-Hwan;Lee, Dong-Hoon;Kim, Hong-Gun;Kim, Yoo-Young
    • Bulletin of the Korean Chemical Society
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    • v.33 no.4
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    • pp.1141-1146
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    • 2012
  • Ce-doped $Y_3Al_5O_{12}$ (YAG:Ce) phosphor powder was prepared using a ${NO_3}^-$-malonic acid-$NH_4NO_3-NH_3{\cdot}H_2O$ system. The YAG:Ce precursor was ignited at $240^{\circ}C$ and the resulting powder contained YAG:Ce crystallites (42%) - active in the visible region at 460 nm - amorphous particles (53%) - inactive at visible wavelengths - and less than 3% oxide (3%) crystallite impurities. The impurities transformed to acitive YAG:Ce crystallites at above $800^{\circ}C$. At above $1000^{\circ}C$, the amorphous phase became YAG phase and isolated $Ce_2O$ crystallites emerged. The powder particles comprised < $4{\mu}m$ secondary aggregates of 20 nm primary particles. The thermal dusting of the secondary particles coincided with the aggregation of the secondary particles at above $900^{\circ}C$.

Enhancement of critical current density in $BaCeO_3$ doped $YBa_2Cu_3O_{7-\delta}$ thin Films deposited by TFA-MOD process (TFA-MOD공정에서 $BaCeO_3$ 첨가에 의한 $YBa_2Cu_3O_{7-\delta}$ 박막의 임계전류밀도 증가)

  • Lee, Jong-Beom;Kim, Byeong-Joo;Lee, Hee-Gyoun;Hong, Gye-Won
    • Progress in Superconductivity and Cryogenics
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    • v.10 no.1
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    • pp.1-5
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    • 2008
  • The effect of $BaCeO_3$ doping on the critical current density of YBCO film by TFA-MOD method was studied. $BaCeO_3$ doping was made by two method; one is direct addition of $BaCeO_3$ nano-sized powder prepared by citrate process followed by grinding with planetary ball mill for 10 hours. Another is addition of Ba-Ce precursor solution prepared with Ba-acetate and Ce acetate dissolved in TFA to the YBCO-TFA precursor solution. The film was made by standard dip coating and heat treatment process with conversion temperature of $790^{\circ}C$ in 1000 ppm oxygen containing moisturized Ar gas atmosphere. The direct addition of $BaCeO_3$ powder resulted in YBCO film with good epitaxial growth and no evidence of second phase formation. The addition through precursor solution resulted in the increase of critical current density upto 30 at% doping and uniform dispersion of $BaCeO_3$ fine inclusion was confirmed by SEM-EDX.

Powder Synthesis and Membrane Deposition of BaCe0.9Y0.1O2.95 and SrCe0.9Y0.1O2.95 System for Hydrogen Separation Application (수소분리용 BaCe0.9Y0.1O2.95 및 SrCe0.9Y0.1O2.95 분말 합성 및 분리막 증착)

  • Kang, Kyung-Min;Yun, Young-Hoon
    • Transactions of the Korean hydrogen and new energy society
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    • v.22 no.6
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    • pp.759-764
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    • 2011
  • Mixed-conducting oxide powders, $BaCe_{0.9}Y_{0.1}O_{2.95}$ (BCY) and $SrCe_{0.9}Y_{0.1}O_{2.95}$ (SCY) powders have been prepared by a solid-state reaction method. Xray diffraction patterns of the prepared powders showed the sharp peaks of the $BaCe_{0.9}Y_{0.1}O_{2.95}$ and $SrCe_{0.9}Y_{0.1}O_{2.95}$ phases. The oxide powders that were prepared by attrition milling showed rather large particles and severe necking between particles in FE-SEM images as well as residual reactant ($BaCO_3$) and secondary phases ($SrCeO_3$ and $CeO_2$) in XRD patterns. The oxide powders prepared using ball milling showed particles under approximately 500 nm and typical XRD patterns of the $BaCe_{0.9}Y_{0.1}O_{2.95}$ and $SrCe_{0.9}Y_{0.1}O_{2.95}$ phases. Ceramic membranes of the $BaCe_{0.9}Y_{0.1}O_{2.95}$ and $SrCe_{0.9}Y_{0.1}O_{2.95}$ phases were fabricated by the aerosol deposition method using the oxide powders synthesized.

Hydrothermal Synthesis of $CeO_2$ Powder (수열법에 의한 $CeO_2$ 분말 합성)

  • Lee, K.J.;Park, B.K.;Lee, T.K.;Hwang, Y.;Kim, C.J.;Choi, S.C.
    • Korean Journal of Crystallography
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    • v.11 no.1
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    • pp.52-57
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    • 2000
  • Hydrothermal synthesis of find CeO₂ powder has been investigated. Synthesis was performed with Ce(NO₃)₃·6H₂O, in ethanol and water solution. Mineralizer were NH₄OH and KOH and reaction for the powder synthesis has performed at 130℃. The morphology of CeO₂ was nearly spherical in using NH₄OH and cubic form in KOH. Particle size increased with addition of NH₄OH. Ethanol solution was effective to reduced the agglomeration.

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