• Title/Summary/Keyword: Porous YSZ

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Microstructure Control of Porous Ceramics by Freeze-Drying of Aqueous Slurry (동결건조공정을 이용한 다공성 세라믹스의 미세구조 제어)

  • 황해진;문지웅
    • Journal of the Korean Ceramic Society
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    • v.41 no.3
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    • pp.229-234
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    • 2004
  • In this study, we proposed new forming process for a porous ceramic body with unique pore structure. h tubular-type porous NiO-YSZ body with radially aligned pore channels was prepared by freeze-drying of aqueous slurry. A NiO-YSZ slurry was poured into the mold, which was designed to control the crystallization direction of the ice, followed by freezing. Thereafter the ice was sublimated at a reduced pressure. SEM observations revealed that the NiO-YSZ porous body showed aligned large pore channels parallel to the ice growth direction, and fine pores are formed around the outer surface of the tube. It was considered that the difference in the ice growth rate during the freezing process resulted in such a characteristic microstructure. Bilayer consisting of dense thin electrolyte film of YSZ onto the tubular type porous body has been successfully fabricated using a slurry-coating process followed by co-firing. It was regarded that the obtained bilayer structure is suitable for constructing electrode-support type electrochemical devices such as solid oxide fuel cells.

Limit-current type zirconia oxygen sensor with porous diffusion layer (다공성 확산층을 이용한 한계전류형 지르코니아 산소센서)

  • Oh, Young-Jei;Lee, Chil-Hyoung
    • Journal of Sensor Science and Technology
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    • v.17 no.5
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    • pp.329-337
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    • 2008
  • Simple, small and portable oxygen sensors were fabricated by tape casting technique. Yttria stabilized zirconia containing cordierite ceramics (YSZC) were used as a porous diffused layer of oxygen in pumping cell. Yttria stabilized zirconia (YSZ) solid electrolyte, YSZC porous diffusion layer and heater-patterned ceramic sheets were prepared by co- firing method. Limit current characteristics and the linear relationship of current to oxygen concentration were observed. Viscosity variation of the slurries both YSZ and YSZC showed a similar behavior, but micro pores in the fired sheet were increased with increasing of the cordierite amount. Molecular diffusion was dominated due to the formation of large pores in porous diffusion layer. The plateau range of limit current in porous-type oxygen sensor was narrow than the one of aperture-type oxygen sensor. However limit current curve was appeared in porous-type oxygen sensor even at the lower applied voltage. The plateau range of limit-current was widen as increasing the thickness of porous diffusion layer of the YSZ containing cordierite. Measuring temperature of $600{\sim}650^{\circ}C$ was recommended for limit-current oxygen sensor. Porous diffusion layer-type oxygen sensor showed faster response than the aperture-type one and was stable up to 30 days running without any crack at interface between the layers.

A Study on the Grinding Characteristics of Surgical Implant Zirconia (임플란트 시술용 지르코니아 소재의 연삭가공 성능 평가에 관한 연구)

  • Lee, Sang-Min;Chae, Seung-Su;Lee, Choong-Seok;Kim, Tack-Su;Lee, Jae-Kun;Lee, Jong-Chan
    • Journal of the Korean Society of Manufacturing Process Engineers
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    • v.13 no.1
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    • pp.72-77
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    • 2014
  • 3.2YSZ melted by the 'skull melting' method has good physical properties and does not undergo low-temperature degradation. Due to its excellent physical and mechanical properties, skull-melted 3.2YSZ has been developed as a dental implant material. In this study, a porous, resin-bonded diamond wheel was created and its grinding characteristics were compared with those of traditional nonporous wheels using skull-melted 3.2YSZ. The experimental results indicate that the porous, resin-bonded diamond wheel requires less grinding force and power. In addition, the porous, resin-bonded diamond wheel requires a greater degree of roughness.

Dense Ceramic-metal Composite Inorganic Membranes for Oxygen Separation (산소 분리를 위한 무공성 세라믹- 금속 복합 무기막)

  • 김진수
    • Proceedings of the Membrane Society of Korea Conference
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    • 2002.05a
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    • pp.35-41
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    • 2002
  • Dense oxygen ionic conducting materials can be used for oxygen separation membranes at high temperatures. However, they show relatively low permeation flux because of their large resistances. To reduce resistances and improve the oxygen permeation flux, thin dense yttria-stabilized-zirconia (YSZ)/Pd composite dual-phase membranes were fabricated by a new approach that combines the reservoir method and chemical vapor deposition (CVD). A thin porous YSZ layer was coated on a porous alumina support by dip-coating the YSZ suspension. A continuous Pd phase was formed inside pores of the YSZ layer by the reservoir method. The residual pores of the YSZ/Pd layer were plugged with yttria/zirconia by CVD to ensure the gas tightness of the membranes. The oxygen permeation fluxes through these composite membrane were 2.0$\times$10$^{-8}$ mol/cm$^2$.s and 4.8$\times$10$^{-8}$ mol/cm$^2$.s at 105$0^{\circ}C$ when air and oxygen were used as the permeate gases, respectively. These oxygen permeation values are about 1 order of magnitude higher than those of pure YSZ membranes prepared under similar conditions.

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A Study on the Reaction Characteristics of Steam Reforming Reaction over Catalyzed Porous Membrane (다공성 촉매 분리막을 이용한 수증기 개질 반응 특성 연구)

  • Hong, Sung Chang;Lee, Sang Moon
    • Applied Chemistry for Engineering
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    • v.25 no.2
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    • pp.198-203
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    • 2014
  • In this study, steam reforming reaction and surface characteristics of Ni metal foam plate were investigated. Valence state of Ni could be changed by pretreatment, and metallic Ni species exposed on surface as a active site play important role in steam reforming reaction. Porous catalytic membrane also was prepared by mixing of Ni metal foam plate and Ni-YSZ catalyst to control the pore size and assign the catalytic function in Ni metal foam plate. In SEM analysis results, Pore size of Ni metal foam plate could be controlled and Ni-YSZ catalyst well dispersed on surface. Ni based porous catalytic membrane had a similar steam reforming activity regardless of space velocity.

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 $1350^{\circ}C$.

Synthesis of Ni-YSZ cermets for SOFC by glycine nitrate process (Glycine nitrate process에 의한 SOFC용 Ni-YSZ cermets 제조)

  • Lee, Tae-Suk;Ko, Jung-Hoon;Kim, Bok-Hee
    • Journal of the Korean Crystal Growth and Crystal Technology
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    • v.20 no.6
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    • pp.289-294
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    • 2010
  • Ni-YSZ (Yttria Stabilized Zirconia) composite powders for SOFC were fabricated by glycine nitrate process. $ZrO(NO_3)_2{\cdot}2H_2O$, $Y(NO_3)_3{\cdot}6H_2O$, $Ni(NO_3)_2{\cdot}6H_2O$ and glycine were chosen as the starting materials. The structural properties of the sintered Ni-YSZ cermets have been investigated with respect to the volume contents of Ni. A porous microstructure consisting of homogeneously distributed Ni and YSZ phases together with well-connected grains was observed. The sintered Ni-YSZ cermets showed a porous microstructure consists of homogeneously distributed Ni and YSZ phases and the grains were well-connected. It was found that the open porosity is sensitive to the volume content of Ni. The Ni-YSZ cermet containing 35 vol% Ni seems to be suitable for the electrode material of SOFC since it provides sufficient open porosity higher than 30%.

Effect of the multilayer structure on electrical and mechanical properties fo thin film yttria stabilized zirconia electrolyte

  • Jung, In-Ho;Lee, You-Kee;Park, Jong-Wan
    • Journal of Korean Vacuum Science & Technology
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    • v.2 no.1
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    • pp.43-48
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    • 1998
  • The effect of mcirostructure on the electrical properties of yttria stabilized zirconia (YSZ) was analyzed by modeling layer arrangements and mixed phase structure. The YSZ thin films were deposited by RF magnetron sputtering using 30mol% YSZ and 8 mol% YSZ targets with yttrium pellets on porous alumina substrates. The structure, composition and electricla properties of the YSZ films were investigated as functions of sputtering conditons and layer arrangements by XRD, TEM, XPS and acimpedance spectroscopy. The results showed that the triple palyered YSZ films had highermicrohardness, lower compressive stress state and higher ionic conductivity by one order than single and double layered YSZ films. However, sputtered YSZ films have low conductivity compared to YSZ pellets or doctor bladed YSZ thin plates. These results were probably due to the influence of insulating alumina substrates, impractical for most stacking geometries and inductance induced by relatively long platinum, lead wire on YSZ conductivity.