• Title/Summary/Keyword: Zirconia monolith

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Chiral Separation of Basic Compounds on Sulfated β-Cyclodextrin-Coated Zirconia Monolith by Capillary Electrochromatography

  • Hong, Jong-Seong;Park, Jung Hag
    • Bulletin of the Korean Chemical Society
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    • v.34 no.6
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    • pp.1809-1813
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    • 2013
  • Sulfated ${\beta}$-cyclodextrin (SCD)-coated zirconia monolith was used as the chiral stationary phase in capillary electrochromatography for enantiomeric separation of basic chiral compounds. SCD adsorbed on the zirconia surface provided a stable chiral stationary phase in reversed-phase eluents. Retention, chiral selectivity and resolution of a set of six basic chiral compounds were measured in eluents of varying pH, composition of methanol and buffer. Optimum mobile phase condition for the separation of the compounds was found to be methanol content of 30%, buffer concentration of 30 mM and pH of 4.0.

Chiral Separation on Sulfonated Cellulose Tris(3,5-dimethylphenylcarbamate)-coated Zirconia Monolith by Capillary Electrochromatography

  • Lee, Jeong-Mi;Jang, Myung-Duk;Park, Jung-Hag
    • Bulletin of the Korean Chemical Society
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    • v.33 no.8
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    • pp.2651-2656
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    • 2012
  • Sulfonated cellulose tris(3,5-dimethylphenylcarbamate) (SCDMPC)-coated zirconia monolith (ZM) was used as the chiral stationary phase in capillary electrochromatography for separation of enantiomers of ten chiral compounds in acetonitrile (ACN)-phosphate buffer mixtures as the eluent. Influences of the ACN content, buffer concentration and pH on chiral separation have been investigated. Separation data on SCDMPC-ZM have been compared with those on CDMPC-ZM. Resolution factors were better on SCDMPC-ZM than CDMPC-ZM while retention factors were in general shorter on the former than the latter. Best chiral resolutions on SCDMPC-ZM were obtained with the eluent of 50% ACN containing 50 mM phosphate at pH around 4.

A Study on Zirconia/Metal Functionally Gradient Materials by Sintering Method (III) (소결법에 의한 $ZrO_2/Metal$계 경사기능재료에 관한 연구(III))

  • 정연길;최성철;박철원
    • Journal of the Korean Ceramic Society
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    • v.32 no.12
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    • pp.1337-1348
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    • 1995
  • TZP/SUS- and ZT/SUS-functionally gradient materials (FGM) were fabricated by pressureless sintering in Ar-atmosphere. The sintering defects such as warping, frustrum formation, splitting and cracking which originated from shrinkage and sintering behaviors of metal and ceramics different from each other could be controlled by the adjustment with respect to the particle size and phase type of zirconia. The residual stresses generated on the metal and ceramic regions in FGM were characterized with X-ray diffraction method, and relaxed as the thickness and number of compositional gradient layer were increased. The residual stress states in TZP/SUS-FGM have irregular patterns by means of the different sintering behavior and cracking at ceramic-monolith. While in ZT/SUS-FGM, compressive stress is induced on ceramic-monolith by the volume expansion of monoclinic ZrO2 at phase transformation. Also, compressive stress is induced on metal-monolith by the constraint of warping which may be created to the metal direction by the difference of coefficient of thermal expansions. As a consequence, it has been verified that the residual stress generated on FGM is dominantly influenced by the thickness and number of compositional gradient layer, and the sintering defects and residual stress can be controlled by the constraint of the difference of shrinkage and sintering behaviors of each component.

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Fabrication and characteristics of limit-current type oxygen sensor with monolith aperture structure (일체화된 Aperture 구조의 한계전류형 산소센서의 제작 및 특성)

  • Oh, Young-Jei;Lee, Deuk Yong
    • Journal of Sensor Science and Technology
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    • v.17 no.4
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    • pp.273-280
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    • 2008
  • Monolith aperture-type oxygen sensors with simple structure of YSZ(pin-hole)/Pt/ YSZ(solid electrolyte)/Pt were fabricated by co-firing technique. To enhance the yield of productivity, a couple of YSZ green sheets for diffused barrier and solid electrolyte were prepared by tape-casting and co-firing method. The limit current characteristics of the oxygen sensors were measured between 500 and $650^{\circ}C$ The heating temperature of $600^{\circ}C$ was optimum as a portable oxygen sensor in the range of oxygen concentration from 0 to 75 vol%. Linear proficiency of limit current behavior as a function of oxygen concentration was controlled by the variation of aperture dimension. The fabricated oxygen sensors showed the stable sensing output for 30 days. Gas leakage in bonding area due to warping, cracking and thermal cycling was not found in the period.

Phase Stability and Physical Properties of $ZrO_2$ doped with $Y_2O_3$ and $Nb_2O_5$ ($Y_2O_3$$Nb_2O_5$가 첨가된 $ZrO_2$의 상 안정성 및 물리적 성질)

  • 이득용;김대준;조경식;장주웅
    • Journal of the Korean Ceramic Society
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    • v.34 no.6
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    • pp.645-651
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    • 1997
  • Tetragonal zirconia polycrystals (TZPs) doped with $Y_{2}O_{3}$ and $Nb_{2}O_{5}$ were prepared by the conventional sintering to enhance fracture toughness and phase stability of TZPs without controlling the grain size. TZP composites were obtained by adding the transformable TZP to the non-transformable TZP in wt%. The monolithic tetragonal $ZrO_2$, same as the composite composition containing 15 wt% transformable TZP, sintered at $1550^{\circ}C$ for 10h in air, exhibited the fracture toughness of 9$MPam^{1/2}$ and no low-and high-temperature degradation at temperatures in the range of 220 to $1000^{\circ}C$ for 100h in air. The corresponding single composition was 90.24 mol% $ZrO_2$-5.31 mol% $Y_{2}O_{3}$-4.75 mol% $Nb_{2}O_{5}$. The microstructure observation revealed that the t-$ZrO_2$ grains grew grandually with sintering time and no microcraking and twinning were observed.

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