• 제목/요약/키워드: Yttria

검색결과 347건 처리시간 0.028초

반응소결된 물라이트-지르코니아(이트리아) 복합체의 상변태와 기계적 성질에 관한 연구 (Phase Transformation and Mechanical Properties of Reaction Sintered Mullite-Zirconia (Yttria) Composite)

  • 오경영;장성도
    • 한국세라믹학회지
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    • 제28권7호
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    • pp.549-555
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    • 1991
  • Mullite-zirconia (0∼4 mol% yttria) composites were obtained by In-situ sintering of zircon and alumina mixture, and their mechanical properties were studied in conjuction with microstructure observation. Martensitic transformation temperature (Ms) of zirconia dispersed in the mullite matrix decreased with Y2O3 contents and was about 600$^{\circ}C$ for ZrO2 containing 4 mol% Y2O3. On cooling of this composites, tetragonal to monoclinic phase transformation induced microcracks at the grain boundary of mullite matrix. The microcracks seemed to absorb the fracture energy in stress field during mechanical tests. Therefore, toughening mechanisms of this composite were considered to nucleation and extension of microcrack, and crack deflection mechanism due to the difference of thermal expansion coefficient between matrix and dispersed phase.

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공침법으로 제조한 아트리아 안정화 지르코니아-알루미나 분말의 특성 (Properties of Yttria Stabilized Zirconia-Alumina Powders Prepared by Coprecipitation Method)

  • 오경영
    • 한국세라믹학회지
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    • 제34권11호
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    • pp.1113-1120
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    • 1997
  • The 2, 4, 6 and 8mol% Y2O3 doped-ZrO2 powders (20 kinds) with the addedtion of Al2O3 upto 8wt% were prepared by coprecipitation method using the zirconium oxyacetate, yttrium chloride and aluminum nitrate as starting materials. The coprecipitated powders were characterized by XRD, TG-DTA, FT-IR and SEM. The sintering properties of zirconia-alumina composites prepared by 2YSZ and 8YSZ powders containing various Al2O3 contents were also investigated. With increasing the yttria stabilizer contents, the amount of exothermic heat for zirconia crystallization decreased. And it was confirmed that the crystallizing temperature of coprecipitated zirconia powders increased and the crystallization process occurred in a wide temperature range, as Al2O3 content increased in 8YSZ.

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변색효과 cubic zirconia의 단결정 성장과 특성평가 (Single crystal growth and characterization of changeable colored cubic zirconia)

  • 박병석;최종건
    • 한국결정성장학회지
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    • 제17권3호
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    • pp.108-112
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    • 2007
  • 광원에 따라 색상이 변화하는 cubic zirconia 단결정을 skull melting 법으로 성장하였다. Co와 Nd에 의해서 황색 영역의 강한 흡수가 일어나며, Fe에 의해 보라색 영역의 흡수가 일어남에 따라 광원이 형광등에서 백열등으로 변화할 때 청-녹색에서 적-자색으로 변화가 발생한다. 첨가물에 의해서 뿐만 아니라 yttria 함량과 열처리 조건 변화에 의해서도 결정의 색이 변화하였다.

지르코니아 인성강화 알루미나 분체의 제조 및 소결 (Preparation and Sintering of Zirconia-Toughnened Alumina Powder)

  • 이전;최상욱;한기성;김승태
    • 한국세라믹학회지
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    • 제29권3호
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    • pp.167-176
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    • 1992
  • Zirconia-toughnened alumina(ZTA) powders that were uniformly coated with zirconia and yttria on the surface of alumina particles were prepared in order to inhibit the grain growth of alumina. Alumina particles were ultrasonically dispersed in the ethanol solution of Zr-n-propoxide, and then the Zr-alkoxide was hydrolyzed. Hydrated zironia as thin film was stabilized to tetragonal crystalline form by doping yttria as a stabilizer. The prepared ZTA powders had the good sinterability even at the lower temperature. As a result, the sintered bodies showed the enhanced fracture toughness compared with pure alumina. The relative density and fracture toughness(KIC) of the ZTA bodies sintered at 1550$^{\circ}C$ were 98% and 5 MPa$.$m1/2 respectively.

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$^{18}O$을 함유하는 X-TZP의 저온열화거동 (Low Temperature Degradation Behavior of $^{18}O$-Containing Y-TZP)

  • 김병국
    • 한국세라믹학회지
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    • 제34권2호
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    • pp.171-174
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    • 1997
  • 산소포논(phonon)이 Yttiria안정화 정방정 지르코니아 소결체(Yttria Stabilized Tetragonal Zirconia Po-lycrystals, Y-TZP)의 저온열화에 큰 영향을 미치는 사실을 실험적으로 밝혔다. Y-TZP의 저온열화 (정방정$\longrightarrow$단사정 상전이) 현상은 Y-TZP의 16O을 18O으로 치환함으로써 급격히 저하되었다. 이는 16O이 보다 무거운 18O으로 치환됨에 따라 임계변위 이상에서 산소원자가 존재할 확률이 감소하는 데 기인하는 것으로 설명하였다.

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전기화학증착에 의한 이트리아 안정화 지르코니아 박막의 제조 (Preparation of Yttria Stabilized zirconia Films by the Electrochemical Vapor Deposition)

  • 정지원;박동원;전치훈;최병진;김대룡
    • 한국세라믹학회지
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    • 제31권5호
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    • pp.477-484
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    • 1994
  • The yttria stabilized zirconia(YSZ) thin films for solid oxide fuel cell (SOFC) were fabricated by an electrochemical vapor deposition(EVD) technique using YCl3+ZrCl4+H2O gas system. The YSZ films were deposited under reduced pressure at the temperature of 1000~120$0^{\circ}C$ on the porous alumina substrates. The deposition rate, chemical composition and growth morphology were investigated by SEM, XRD, EDS. The growth rates of the films obeyed a parabolic rate law, representing that the growing process is controlled by an electrochemical transport through the YSZ film. The Y2O3 content of the films was about 10 mol%, equal to the composition of metal chloride reactant gases, approximately. The YSZ films were highly dense, the growing features showed columnar structure and surface morphologies were changed with the EVD conditions.

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이트리아를 함유한 지르코니아 고체전해질의 물리적, 전기적 특성 (Some Physical and Electrical Properties of Zirconia Solid Electrolyte Contained Yttria)

  • 정형진;오영제
    • 한국세라믹학회지
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    • 제23권1호
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    • pp.13-20
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    • 1986
  • Zirconia soild electrolytes containing 4~10mol% of yttria were prepared by wet-blending of oxides and rea-ction-sintering, Sinterbility and degree of stabilization were optimized for the development of oxygen sensor. Fracture strength thermal expansion coefficient electrical conductivity and galvanic potential were measured and discussed with respect to the amount of ytria addition phase transformation microstructure and degree of stabilization. It was found that sintering and stabilization occurred when the composition was designed to be near the boundary region of $ZrO_2-Y_2O_3$ binary system. In such away a good zirconia solid electrolyte suitable for oxygen sensor could be developed.

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Use of High-Temperature Gas-Tight Electrochemical

  • Park, Jong-Hee;Beihai Ma;Park, Eun-Tae
    • The Korean Journal of Ceramics
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    • 제4권2호
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    • pp.103-113
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    • 1998
  • By using a gas-tight electrochemical cell, we can perform high-temperature coulometric titration and measure electronic transport properties to determine the elecronic defect structure of metal oxides. This technique reduces the time and expense required for conventional thermogravimetric measurements. The components of the gas-tight coulometric titration cell are an oxygen sensor, Pt/yttria stabilitized zirconia(YSZ)/Pt, and an encapsulated metal oxide sample. Based on cell design, both transport and thermodynamic measurements can be performed over a wide range of oxygen partial pressure ($pO_2=10^{-35}$ to 1 atm). This paper describes the high-temperature gas-tight electrochemical cells used to determine electronic defect structures and transport properties for pure and doped-oxide systems, such as YSZ, doped and pure ceria $(Ca-CeO_2 \;and\; CeO_2)$, copper oxides and copper-oxide-based ceramic superconductors, transition metal oxides, $SrFeCo_{0.5}O_x,\; and \;BaTiO_2$.

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졸-겔법에 의한 이트리안 안정화 지프코니아박막의 결정화 (Crystallization of Yttria-Stabilized-Zirconia Film by Sol-Gel Process)

  • 서원찬;조차제;윤영섭;황운석
    • 한국표면공학회지
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    • 제30권3호
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    • pp.183-190
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    • 1997
  • Fabrication and crystallization characteristics of yttria($T_2O_3$) stabilized zirconia(YSZ) thin film by sol-gel process were studied. YSZ sol was synthesized with zirconium n-propoxide($Zr(OC_3H_7)_4)$) and yttrium nitrate pentahydrate ($Y(NO_3)_3.5H_2O$). YSZ film was prepared by depositing the polymeric sol on porous $Al_2O_3$ substrate by spin-coating, and the film characteristics were investigated by FRIR, TG-DTA, XRD, DSC, optical microscopy and SEM. The film topology was uniform and cracks were not found. It was found that the annealing temperature and the concentration of stabilizer affect the crystallization of YSZ film. The YSZ film began to crystallize from amorphous to tetragonal phase at 40$0^{\circ}C$, and it was not converted to cubic structure until $1100^{\circ}C$. It seemed that the grains were formed over $700^{\circ}C$and the average grain size was obtained about 0.2$\mu\textrm{m}$.

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High-frequency Induction Heating Sintering of Hydroxyapatite-($ZrO_2+3%Mol\;Y_2O_3$) Bioceramics

  • Khalil, Khalil Abdel-razek;Kim, Sug-Won
    • 한국분말야금학회:학술대회논문집
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    • 한국분말야금학회 2006년도 Extended Abstracts of 2006 POWDER METALLURGY World Congress Part2
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    • pp.924-925
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    • 2006
  • In this study, hydroxyapatite (HAp) and hydroxyapatite-yttria stabilized zirconia (HAp-3YSZ) with 20 vol.%-($ZrO_2+3%mol\;Y_2O_3$) nanopowders were consolidated very rapidly to full density by High-frequency induction heat sintering (HFIHS). Effects of temperature and the addition of 3YSZ on the toughness, hardness and microstructure properties have been studied. 3YSZ second phase toughening HAp composites with higher toughness were successfully developed at relatively low temperatures through this technique. Compared with hardness and toughness obtained for pure HAp, the hardness and toughness for HAp-20vol. % 3YSZ were much higher.

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