• 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).

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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Microstructures and Densification Behaviors of $Al_2O_3-ZrO_2(ZTA)$ Composites Fabricated by a Surface-induced Coating (표면-유기 코팅에 의해 합성한 $Al_2O_3-ZrO_2(ZTA)$ 복합체의 미세구조와 소결거동)

  • 장현명;문종하;김광수
    • Journal of the Korean Ceramic Society
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    • v.31 no.1
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    • pp.17-24
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    • 1994
  • Al2O3-ZrO2(ZTA) composites were fabricated by a surface-induced coating of the precursor for the ZrO2 phase on the kinetically stable colloid particles of Al2O3. The fabricated composites were characterized by a uniform spatial distribution of the dispersed ZrO2 phase and by the absence of large ZrO2 grains throughout the Al2O3 matrix. The fracture toughness (KIC) and the bending strength of ZTA composites sintered at 1$600^{\circ}C$, respectively, were 5.6 MPa.m1/2 (for 20 wt% ZrO2) and 600 MPa (for 15wt% ZrO2). The fraction of tetragonal ZrO2 phase decreases as the total content of ZrO2, suggesting that both the stress-induced tlongrightarrowm transformation and the microcrack nucleation contribute to the toughening of the ZTA composites fabricated by the surface-induced coating.

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Preparation of $ZrO_2/Al_2O_3-Mullite$ Composites Using the Silica Sol Infiltration Method (실리카 졸 침투법을 이용한 $ZrO_2/Al_2O_3-Mullite$ 복합체의 제조)

  • 현상훈;최지영
    • Journal of the Korean Ceramic Society
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    • v.29 no.9
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    • pp.719-728
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    • 1992
  • ZrO2/Al2O3-Mullite composites were prepared by infiltration of the silica sol to the porous ZrO2/Al2O3 bodies. The porous ZrO2/Al2O3 bodies for infiltration were fabricated using ZrO2 (20wt%)/Al2O3 composite powders synthesized by the emulsion-hot kerosene drying method. The preparation of silica sols was conducted by the hydrolysis-peptization of an alcoholic TEOS solution. When ZrO2/Al2O3-Mullite and ZrO2/Al2O3 composites were sintered at 1$650^{\circ}C$ for 4 hrs, both of them showed an excellent sinterability. As the amount of mullite added in the composites increased, the ratio of the tetragonal phase of zirconia to the monoclinic phase at the room temperature became higher. It was known that values of the fracture toughness of the ZrO2/Al2O3-Mullite composites were about 5.48 MPa.m1/2 much larger than that of the ZrO2/Al2O3 system.

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Studies on the Spinnability of PP/Zr$O_{2}$ Mixture(I) (폴리프로필렌/지르코니아 혼합물의 방사성에 관한 연구(I)-방사조건에 따른 구조와 기계적 성질-)

  • Jeon, Jae-Wan;Ju, Chang-Hwan;Kim, Dong-Cheol
    • Textile Science and Engineering
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    • v.31 no.5
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    • pp.393-400
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    • 1994
  • The zirconiunl dioxide(ZrO2) has characterized as a far infrared radiator and can apply as the thermal storage material by mixing with various polymers. In the present work, PP chips were blended with ZrO2 particles by the banbury mixer and spun PP/ZrO2 composite fibers by using the melt spinning machine with different spinning conditions. Effect of the draw ratio and amount of ZrO2 on the morphological structure and mechanical properties of the produced PP/ZrO2 composite fibers has been investigated. The results obtained are as follows: (1) the good dispensability of ZrO2 particles in the PP fiber has been observed and the phase separation between PP and ZrO2 has an increasing trend with increasing draw ratio on PP/ZrO2 composite fibers. (2) the breaking stress has increased to a significant extent with increasing the draw ratio, but decreased with increasing the amount of ZrO2, (3) in the X-ray diffraction pattern, the peak intensities of PP/ZrO2 composite fibers have increased with increasing the draw ratio, and (4) the crystallinity of PP/ZrO2 composite fibers has slightly changed with increasing the amount of ZrO2 and considerably increased with increasing the draw ratio.

Studies on the Spinnability of PF/ZrO2 Mixture(II)-Effect of Spinning Condition on the Thermal and Viscoelastic Properties- (폴리프로필렌/지르코니아 혼합물의 방사성에 관한 연구(II)-방사조건에 따른 열적 및 점탄성 성질-)

  • Jeon, Jae-Wan;Ju, Chang-Hwan;Kim, Dong-Cheol
    • Textile Science and Engineering
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    • v.31 no.6
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    • pp.452-458
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    • 1994
  • In order to investigate the thermal and viscoelastic properties of Pp/ZrO2 composite fibers, polypropylene(PP) chips were mixed with the zirconium dioxide(ZrO2) powder characterized as a far infrared radiator and PP/ZrO2 composite fibers were spun by using the melt spinning machine with different spinning conditions (i. e.. draw ratio and the amount of ZrO2 Effects of spinning condition on the thermal and viscoelastic properties of the produced PP/ZrO2 composite fibers have investigated. The results obtained in this study are as follows: 1. The amount of ZrO2 on the composite fiber has scarecely influenced on the melting temperature and the melting temperature of iolo Pp/ZrO2 composite Hber is 161℃, but the crystallinity temperature has increased with increasing the amount of ZrO2 and the decomposition temperature of Pp/ZrO2 composite fiber has an decreasing trend with increasing the draw ratio. 2. The loss tangent(tan 6) has decreased with increasing the draw ratio in the ad absorption peak, but the absorption intensity of E' and E" has increased with increasing the draw ratio in the ac absorption temperature. Meanwhile, in the aa absorption region, the loss tangent of PP/ZrO2 composite fibers has decreased with increasing the amount of ZrO2.

A Study of Crystallization and Fracture Toughness of Glass Ceramics in the $ZrO_2.SiO_2$ Systems Prepared by the Sol-Gel Method (졸-겔법으로 제조한 $ZrO_2.SiO_2$계 결정화유리의 결정화 및 파괴인성에 관한 연구)

  • 신대용;한상목;강위수
    • Journal of the Korean Ceramic Society
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    • v.37 no.1
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    • pp.50-56
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    • 2000
  • Precursor gels with the composition of xZrO2·(100-x)SiO2 systems (x=10, 20 and 30 mol%) were prepared by the sol-gel method. Kinetic parameters, such as activation energy, Avrami's exponent, n, and dimensionality crystal growth value, m, have been simultaneously calculated from the DTA data using Kissinger and Matusita equations. The crystallite size dependence of tetragonal to monoclinic transformation of ZrO2 was investigated using XRD, in relation to the fracture toughness. The crystallization of tetragonal ZrO2 occurred through 3-dimensional diffusiion controlled growth(n=m=2) and the activation energy for crystallization was calculated using Kissinger and Matusita equations, as about 310∼325±10kJ/mol. The growth of t-ZrO2, in proportion to the cube of radius, increased with increasing heating temperature and hteat-treatment time. It was suggested that the diffusion of Zr4+ ions by Ostwald ripening was rate-limiting process for thegrowth of t-ZrO2 crystallite size. The fracture toughness of xZrO2·(100-x)SiO2 systems glass ceramics increased with increasing crystallite size of t-ZrO2. The fracture toughness of 30ZrO2·70SiO2 system glass ceramics heated at 1,100℃ for 5h was 4.84 MPam1/2 at a critical crystaliite size of 40 nm.

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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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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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용액 공정 기반 ZrO2 절연막을 사용한 IGZO 박막 트랜지스터의 전기적 특성 향상 연구

  • Lee, Na-Yeong;Choe, Byeong-Deok
    • Proceedings of the Korean Vacuum Society Conference
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    • pp.215.1-215.1
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    • 2015
  • 본 연구에서는 용액 공정 기반 ZrO2 절연막의 우수한 특성을 확인하기 위해 SiO2 절연막을 가지는 IGZO (Indium-Gallium-Zinc Oxide) 박막 트랜지스터와 비교했다. In:Ga:Zn=1:1:1의 비율의 0.3 M IGZO 용액과 0.2 M ZrO2용액을 사용하였다. ZrO2 박막 트랜지스터는 0.2M ZrO2 용액을 5번 반복 증착하며 140nm 두께의 ZrO2 절연막을 가지는 IGZO 박막 트랜지스터와 비교대상으로 동일한 두께의 SiO2의 절연막을 가지는 IGZO 박막 트랜지스터를 제작하였다. ZrO2 박막 트랜지스터의 문턱전압은 4.3V로 SiO2 박막 트랜지스터의 -6.1V보다 낮았고, 이동도는 $1.2356cm^2/V{\cdot}s$$0.0554cm^2/V{\cdot}s$ 보다 약 20배 높았다. 실험 결과를 통해 ZrO2를 절연막으로 사용한 박막 트랜지스터의 특성이 더 향상되었음을 확인하였다.

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