• Title/Summary/Keyword: Zirconia ceramics

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Phase Evolution and Thermo-physical Properties of Rare-earth Oxides for Thermal Barrier Systems (열차폐용 희토류 산화물의 상형성과 열물성)

  • Shim, Byung-Chul;Kwak, Kil-Ho;Lee, Sung-Min;Oh, Yoon-Suk;Kim, Hyung-Tae;Jang, Byung-Koog;Kim, Seong-Won
    • Journal of Powder Materials
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    • v.17 no.2
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    • pp.148-153
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    • 2010
  • Thermal barrier systems have been widely investigated over the past decades, in order to enhance reliability and efficiency of gas turbines at higher temperatures. Yttria-stabilized zirconia (YSZ) is one of the most leading materials as the thermal barriers due to its low thermal conductivity, thermodynamic stability, and thermal compatibility with metal substrates. In this work, rare-earth oxides with pyrochlore phases for thermal barrier systems were investigated. Pyrochlore phases were successfully formed via solid-state reactions started from rare-earth oxide powders. For the heat-treated samples, thermo-physical properties were examined. These rare-oxide oxides showed thermal expansion of $9{\sim}12{\times}10^{-6}/K$ and thermal conductivity of 1.2~2.4 W/mK, which is comparable with the thermal properties of YSZ.

Fabrication and Mechanical Properties of High-strength Porous Supports for High Temperature Oxygen Transport Membrane (고온 산소분리막용 고강도 다공성 지지체 제조 및 기계적 특성 연구)

  • Park, Geum Sook;Seong, Young-Hoon;Yu, Ji Haeng;Woo, Sang Kuk;Han, Moon Hee
    • Journal of the Korean Ceramic Society
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    • v.50 no.6
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    • pp.423-428
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    • 2013
  • Porous YSZ ceramics are fabricated using 3 mol% yittria-stabilized zirconia (3YSZ) and NiO with different particlesizes (0.6 and 7 ${\mu}m$). Nickel oxide (NiO) is added to the YSZ powder as a pore former with different amounts(40, 50, and 60 vol%) and at different sintering temperatures (1350 and $1400^{\circ}C$) are applied in order to evaluate the temperature effects on the pore and mechanical properties. Heat treatment is conducted after sintering at $700^{\circ}C$ in $H_2$ for the NiO reduction process; then, Ni is removed using a $HNO_3$ etchant solution. According to the NiO contentand sintering temperatures, 41-67% porous YSZ ceramic is obtained and the flexural strength increases, while the porosity decreases with an increasing sintering temperature. The optimum flexural strength ($136.5{\pm}13.4MPa$) and porosity (47%) for oxygen transport porous YSZ membrane can be obtained with 40 vol% of 7 ${\mu}m$ NiO particle at a sintering temperature of $1350^{\circ}C$.

A Study on the Alumina Ceramic Composite Dispersed With the Zirconia (지르코니아-알루미나 세라믹 복합재료에 관한 연구)

  • Park, Jae-Sung;Lee, Yeong-Sin
    • 전자공학회논문지 IE
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    • v.49 no.2
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    • pp.1-8
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    • 2012
  • The effects of the addition of either monoclinic $ZrO_2(pure)$ or tetragonal $ZrO_2$ containing 5.35wt% $Y_2O_3(Y-TZP)$ on the mechanical properties and thermal shock resistance of $Al_2O_3$ ceramics were investigated. The addition of $ZrO_2$(m) and Y-TZP increased sintered density of $Al_2O_3$. The Vickers hardness also increased as the volume fraction of Y-TZP increased going through a maximum at 20wt%. The hardness of the specimens was found to be dependent on the sintered density. The higher volume fraction of either $ZrO_2(m)$ or Y-TZP resulted in the higher fracture toughness of the composite was. This result may be taken as evidence that toughening of $Al_2O_3$ can be achieved by not only the transformation toughening but microcrack toughening of $ZrO_2$. The thermal shock property for $Al_2O_3-ZrO_2$ composites was improved by increasing the volume fraction of monoclinic $ZrO_2(pure)$. The grain size increased as the volume fraction of $ZrO_2$ did.

Experimental Study on the Application of Ceramic Friction Materials for Bridge Bearing (교량받침용 세라믹 마찰재 적용을 위한 실험적 연구)

  • Ji-Hun Park;Jung-Woo Lee;Jong-Won Kwark
    • Journal of the Korean Recycled Construction Resources Institute
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    • v.11 no.4
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    • pp.527-534
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    • 2023
  • This paper conducted a study on the application of ceramic materials for bridge bearing that can complement the durability of PTFE, a conventional bridge bearing friction material, and exhibit low coefficient of friction and friction behavior without lubricant. The ceramic material was zirconia (ZrO2), and the friction behavior was evaluated according to the roughness coefficient. The roughness coefficient was divided into 0.8 and 0.027, and the average coefficient of friction was calculated to be 0.16 under 15 MPa surface pressure. Afterward, ceramic was made into friction material and applied to the bridge bearing, and performance comparison with PTFE bridge bearing was conducted through compression test and friction test. In the compression test, the ceramic and PTFE bridge bearing showed ideal compression behavior depending on the load. No fractures or defects were observed in the ceramic bridg bearing, but lubricant loss was observed in the PTFE bridge bearing. The average coefficient of friction of the ceramic bridge bearing analyzed through friction behavior was 0.16. The inherent material properties of the physical and chemical properties of ceramics, the excellent mechanical properties derived from the performance evaluation, and the coefficient of friction of 0.16 suggest that it can be considered as a friction material.