• Title, Summary, Keyword: $ZrO_{2}$

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Fabrication and Physical Properties of ZrO2(m)-Al2O3ZrO2(t)-Al2O3 Structural Ceramics (ZrO2(m)-Al2O3ZrO2(t)-Al2O3 세라믹스의 제조와 물리적 특성)

  • Park, Jae-Sung;Park, Ju-Tae;Park, Jung-Rang
    • Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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    • v.24 no.4
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    • pp.140-148
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    • 2010
  • The effects of the addition of either monoclinic $ZrO_2(ZrO_2(m))$ or tetragonal $ZrO_2(ZrO_2(t))$ containing 5.35[wt%] $Y_2O_3$ on the physical properties and electrical conductivity of $Al_2O_3$ were investigated. The addition of $ZrO_2$(m) and $ZrO_2$(t) increased sintered density of $Al_2O_3$. The Vickers hardness also increased as addition of $ZrO_2$(t) increased going through a maximum at 20[wt%] and the hardness of the specimens was found to be dependent on the sintered density. The addition of $ZrO_2$(t) improved the hardness of $Al_2O_3-ZrO_2$ systems and the $ZrO_2$(m) addition showed the better effect on the thermal shock property of $Al_2O_3-ZrO_2$ systems than that of the $ZrO_2$(t) addition. Above 15[wt%] addition of $ZrO_2$(t), the electrical conductivity is gradually increased with increasing applied voltage but not effects by addition of $ZrO_2$(m).

(Effect of Monoclinic Zirconia and Tetragonal Zirconia Addition on Physical Properties and Electrical conductivity of $Al_2O_3$) ($Al_2O_3$의 물리적 성질 및 전기전도도에 미치는 단사정 지르코니아와 정방정 지르코니아의 첨가효과)

  • 박재성;어수해
    • Journal of the Institute of Electronics Engineers of Korea TE
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    • v.39 no.1
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    • pp.1-8
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    • 2002
  • The effects of the addition of either monoclinic $ZrO_2$($ZrO_2$(m)) or tetragonal $ZrO_2$($ZrO_2$(t)) containing 5.35wt% $Y_2O_3$ on the physical properties and electrical conductivity of TEX>$Al_2O_3$ were investigated. The addition of $ZrO_2$(m) and $ZrO_2$(t) increased sintered density of $Al_2O_3$. The Vickers hardness also increased as addition of >($ZrO_2$(t) increased going through a maximum at 20wt% and the hardness of the specimens was found to be dependent on the sintered density. The addition of $ZrO_2$(t) improved the hardness of $Al_2O_3$-$ZrO_2$ systems and the $ZrO_2$(m) addition showed the better effect on the thermal shock property of $Al_2O_3$-$ZrO_2$ systems than that of the $ZrO_2$(t) addition. Above 15wt% addition of $ZrO_2$(t), the electrical conductivity is gradually increased with increasing applied voltage but not effects by addition of $ZrO_2$(m).

Microstructures and Mechanical Properties of $Al_2O_3$-$ZrO_2$ Ceramics Prepared by a Precipitation Method (침전법으로 제조한 $Al_2O_3$-$ZrO_2$계 세라믹스의 미세구조 및 기계적 특성)

  • 홍기곤;이홍림
    • Journal of the Korean Ceramic Society
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    • v.27 no.8
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    • pp.991-1003
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    • 1990
  • A precipitation method, one of the most effective liquid phase reaction methods, was adopted in order to prepare high-tech Al2O3/ZrO2 composite ceramics. Al2(SO4)3.18H2O, ZrOCl2.8H2O and YCl3.6H2O were used as starting materials and NH4OH as a precipitation agent, various types of metal hydroxides were obtained by single precipitation(series A) and co-precipitation(series B) method at the pH condition between 7 and 11. Fine Al2O3-ZrO2 powders were prepared at optimum calcination condition and the effects of ZrO2 on microstructures and mechanical properties of Al2O3 were investigated. The composition of Al2O3/ZrO2 composites wax fixed as Al2O3-15 v/o ZrO2(+3m/o Y2O3). ZrO2 limited the grain growth of Al2O3 and increased grain size homogeneity of Al2O3 more effectively than MgO.Flexural strength values in Al2O3 and Al2O3/ZrO2 composites were 340-430 MPa and 540-820 MPa, respectively, and the effect of strength improvement showed 20-50% by adding ZrO2 to Al2O3. Fracture toughness of Al2O3/ZrO2 composites was improved by stress-induced phase transformation of tetragonal ZrO2 and toughening effect by microcrack was not observed. Also, ZrO2 particles located at Al2O3 grain junction contributed to toughening, while spherical ZrO2 particles located within Al2O3 grain did not contribute to toughening. Weibull moduli of Al2O3 ceramics and Al2O3/ZrO2 composites of series A and series B were 4.34, 5.17 and 9.06, respectively. Above 0.5 of failure probability, strength values in Al2O3 ceramics and Al2O3/ZrO3 composites of series A and series B were above 400 MPa, 700 MPa and 650 MPa, respectively.

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Microstructure and Mechanical Properties of $Al_2$O$_3$/t-ZrO$_2$ Particulate Composites (Al$_2$O$_3$/t-ZrO$_2$ 입자복합체의 미세구조 및 기계적 성질)

  • 심동훈;이윤복;김영우;오기동;박홍채
    • Journal of the Korean Ceramic Society
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    • v.36 no.7
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    • pp.734-741
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    • 1999
  • Al2O3/t-ZrO2 particulate composites were prepared by sintering at 150$0^{\circ}C$ and 1$600^{\circ}C$ for 2h in air and microstructure and mechanical properties of the composites were investigated. Although most ZrO2 particles existed at Al2O3 grain boundaries a few ZrO2 particles within Al2O3 grains. Al2O3 grain growth was depressed due to the pinning effect by ZrO2 particles. During sintering coarsening of intergranular ZrO2 particles occurred as a results of the elimination of ZrO2 intraagglomerate grain boundaries and the coalescence of dragged ZrO2 particles by migrating Al2O3 grain boundries. Changes in mechanical properties of Al2O3 composites were dependant on microstructure of Al2O3 matrix and on size and structure of dispersed ZrO2.

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Effect of ZrO2 Addition on the Microstructure and Electrical Properties of Ni-Mn Oxide NTC Thermistors (Ni-Mn 산화물 NTC 서미스터의 미세구조와 전기적 특성에 미치는 ZrO2첨가의 효과)

  • 박경순;방대영;윤성진;최병현
    • Journal of the Korean Ceramic Society
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    • v.40 no.1
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    • pp.11-17
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    • 2003
  • The effect of$ZrO_2$addition on the microstructure and electrical properties of Ni-Mn oxide NTC thermistors was studied. Major phases present in the sintered bodies of $Ni_{1.0}Mn_{2-x}Zr_xO_4$ were the solid solutions of Ni-Mn-Zr oxides with a cubic spinel structure and the $ZrO_2$ with a tetragonal structure. The $ZrO_2$ was formed by the partial decomposition or incomplete formation of the Ni-Mn-Zr oxides during sintering. With increasing the amount of added $ZrO_2$, the $ZrO_2$ phase increased. The relationship between log resistivity (log p) and the reciprocal of absolute temperature (1/T) of the NTC thermistors prepared was linear, indicative of NTC characteristics. The resistivity, B constant and activation energy of the thermistors increased with increasing $ZrO_2$ content.

Control of Microstructures and Properties of Composites of the Al2O3/ZrO2-ZrO2-Spinel System: I. Preparation and Sintering Behavior of Al2O3-ZrO2 Composite Powders (Al2O3/ZrO2-Spinel계 복합체의 미세구조 및 물성제어: I. Al2O3-ZrO2 복합분체의 제조 및 소결특성)

  • 현상훈;송원선
    • Journal of the Korean Ceramic Society
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    • v.29 no.10
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    • pp.797-805
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    • 1992
  • Al2O3-20 wt% ZrO2 composite powders to be used as the starting materials of the Al2O3/ZrO2-Spinel composite system were prepared by the use of the emulsion-hot kerosene drying method. The crystalline phase of ZrO2 in the synthesized Al2O3-ZrO2 composite powders was 100% tetragonal but the small amount of t-ZrO2 was transformed into m-ZrO2 after crushing. The hardness, fracture toughness, and flexural strength of the composite, which was sintered at 1650$^{\circ}C$ for 4 hrs after calcining at 1100$^{\circ}C$ for 2 hrs and had the relative density of 99%, were 15.7 GPa, 4.97 MN/m3/2, and 390 MPa, respectively. The fracture form in the sintered composites was found to be the intergranular fracture.

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Microstructure and Mechanical Properties of $Al_2O_3$-$ZrO_2$-Nb Composites Prepared by Reaction Sintering (반응소결로 얻어진 $Al_2O_3$-$ZrO_2$-Nb 복합체의 미세구조와 기계적 성질)

  • ;;;R.J. Brook
    • Journal of the Korean Ceramic Society
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    • v.28 no.5
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    • pp.422-428
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    • 1991
  • The reaction sintering of Al2O3-ZrO2-Nb composite has been investigated using Al2O3, and ZrAl2 powders. Two kinds of specimens, 78.3Al2O3-14.0Nb2O5-7.7ZrAl2 in wt.% (AZN-5) and 72.3Al2O3-13.8Nb2O5-7.5ZrAl2-6.4ZrO2(AZN-10), were prepared. Powder compacts were sintered at various temperatures between 1$600^{\circ}C$ and 1$700^{\circ}C$ for 30 min in Ar. DTA and X-ray analysis have showen that a reaction between Nb2O5 and ZrAl2 started at 149$0^{\circ}C$ to form Al2O3, ZrO2, and Nb. The sintered density increased with the sintering temperature. AZN-10 specimen showed higher density than AZN-5 specimen for almost all the experimental conditions. Al2O3-ZrO2-Nb composite hot pressed after reaction sintering showed higher toughness and lower hardness than hot pressed Al2O3-ZrO2. The crack propagated through many metallic Nb particles which showed plastic deformation, and this is the cause of the increase in toughness of Al2O3-ZrO2-Nb composite over Al2O3-ZrO2.

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Sintering Behavior of Al2O3-15v/o ZrO2(+3m/o Y2O3) Ceramics Prepared by Precipitation Method (침전법으로 제조한 Al2O3-15v/o ZrO2(+3m/o Y2O3)계 세라믹스의 소결거동)

  • 홍기곤;이홍림
    • Journal of the Korean Ceramic Society
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    • v.26 no.3
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    • pp.423-437
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    • 1989
  • Al2O3/ZrO2 composites were prepared by precipitation method using Al2(SO4)3.18H2O, ZrOCl2.8H2O and YCl3.6H2O as starting materials and NH4OH as a precipitation agent. Al2O3/ZrO2 composites(series A) were prepared by mixing Al2O3 powder obtained by single precipitation method with ZrO2(+3m/o Y2O3) powder obtained by co-predipitation method. Al2O3/ZrO2 composites (series B) were prepared by co-precipitation method using the three starting materials. In all cases, the composition was controlled as Al2O3-15v/o ZrO2(+3m/o Y2O3). The composites of series A showed higher final relative densities than those of series B and tetagonal ZrO2 in all cases was retained to about 95% at room temperature. ZrO2 particles were coalesced more rapidly in grain boundary of Al2O3 than within Al2O3 grain. ZrO2 particles were located at 3-and 4-grain junction of Al2O3 and limited the grain growth of Al2O3. It was observed that MgO contributed to densification of Al2O3 but limited grain growth of Al2O3 by MgO was not remarkable. In all Al2O3/ZrO2 composites, exaggerated grain growth of Al2O3 was not observed and Al2O3/ZrO2 composites were found to have homogeneous microstructures.

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Dispersion of ZrO2 by Coprecipitation in Al2O3/ZrO2Ceramics (Al2O3/ZrO2요업체에서 공침에 의한 ZrO2입자의 분산)

  • Cho, Myung-Je;Choi, Jung-Lim;Park, Jung-Kwon;Hwang, Kyu-Hong;Lee, Jong-Kook
    • Journal of the Korean Ceramic Society
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    • v.39 no.7
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    • pp.704-709
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    • 2002
  • To improve the mechanical properties of $Al_2$O$_3$/ZrO$_2$composites, the homogeneous dispersion of ultra low size ZrO$_2$ particles in $Al_2$O$_3$ceramics have been controlled by coprecipitation method. In case of mechanical mixing of ZrO$_2$ powders with $Al_2$O$_3$, homogeneous dispersion and controlling the ZrO$_2$ size were relatively difficult due to high sintering temperature. So nanosized Zr hydroxide was coprecipitated from ZrOCl$_2$/Y(NO$_3$)$_3$ solution with commercial sub-micron sized $\alpha$-alumina (Sumitomo : AES-11(0.4 ${\mu}{\textrm}{m}$)) and high purity ultra low sized $\alpha$-alumina (Taimei Chemical (0.22 ${\mu}{\textrm}{m}$)) for low temperature sintering. By this partial coprecipitation method, relatively low sized ZrO$_2$ dispersion in $Al_2$O$_3$/ZrO$_2$ composites was achieved at 150$0^{\circ}C$-1$600^{\circ}C$ of sintering temperature range and their mechanical properties were measured.

Fabrication of Al2O3/ZrO2Ceramics by the Polymerization Dispersion Process (ZrO2의 고분자화 분산법을 이용한 Al2O3/ZrO2요업체의 제조)

  • Cho, Myung-Je;Hwang, Kyu-Hong;Lee, Jong-Kook
    • Journal of the Korean Ceramic Society
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    • v.41 no.4
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    • pp.284-288
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    • 2004
  • To improve mechanical properties of $Al_2$O$_3$/ZrO$_2$composites have been controlled dispersion of ultra low size ZrO$_2$ particles in $Al_2$O$_3$ ceramics by polymeric precursor method (Pechini process). In case of coprecipitation or mechanical mixing of ZrO$_2$ powders with $Al_2$O$_3$, homogeneous dispersion and controlling the ZrO$_2$ size were relatively difficult due to high sintering temperature. So the polyesterization process of Zr/Y(NO$_3$)$_3$-citric acid solution in ethylene glycol with the commercial sub-micron sized o(-alumina powder (Sumitomo AES-11(0.4 ${\mu}{\textrm}{m}$)) was adopted in order to obtain homogeneous dispersion of ZrO$_2$ in A1203. By this partial polyesterization process, the homogeneous dispersion of relatively low sized ZrO$_2$in $Al_2$O$_3$/ZrO$_2$composites was achieved at 1450∼1$600^{\circ}C$ of sintering temperature range and their mechanical properties were measured.