• Bulletin of the Korean Chemical Society
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• 제34권6호
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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.

• Bulletin of the Korean Chemical Society
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• 제33권8호
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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.

• 한국세라믹학회지
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• 제32권12호
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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.

• 센서학회지
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• 제17권4호
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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.

• 한국세라믹학회지
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• 제34권6호
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• pp.645-651
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• 1997

입성장 제어없이 정방정 니르코니아의 파괴인성과 상 안정성을 증진시키기 위해 $Y_{2}O_{3}$와 $Nb_{2}O_{5}$가 첨가된 정방정 지르코니아를 상압소결방법으로 제조하였다. 지르코니아 복합체는 상 안정성이 뛰어난 조성에 상변화가 우수한 조성을 중량비로 혼합 합성하였다. 상변화가 우수한 조성을 15 wt% 첨가한 복합체와 동일한 단일조성의 경우 공기중에 $1500^{\circ}C$ 10시간 소결후 9$MPam^{1/2}$의 파괴인성값과 $220^{\circ}C$에서 $1000^{\circ}C$/까지 100시간이상 agmg을 한 뒤에도 우수한 저온 및 고온 상 안정성이 관찰되었다. 복합체와 상응하는 단일조성은 90.24 mol% $ZrO_2$-5.31 mol% $Y_{2}O_{3}$ mol% $Nb_{2}O_{5}$이었다. 조직관찰 결과 결정립은 소결시간에 따라 증가하였으며 미세균열이나 twinning은 발견되지 않았다.