• Title/Summary/Keyword: Al2O3-ZrO2

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The Study of the Properties of $Pb(Mg_{0.15} W_{0.15})Ti_{0.35}-Zr_{0.35}O_3$ Ceramics Modified with $La_2O_3$, $Nb_2O_5$ and $Al_2O_3$ (첨가제에 따른 $Pb(Mg_{1/2} W_{1/2}) O_3-PbTiO_3-ObZrO_3$ 고용체의 특성에 대한 연구)

  • 안영필;황학인;홍진녕
    • Journal of the Korean Ceramic Society
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    • v.22 no.2
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    • pp.17-24
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    • 1985
  • In the composition of $Pb(Mg_{0.15} W_{0.15})Ti_{0.35}-Zr_{0.35}O_3$ the effect of particle size on PbO vaporization were measured, . The initial step of discontinuous vaporization of unreated PbO during the calcining process was depended on the particle size. All additives $La_2O_3Nb_2O_5$ and $Al_2O_3$ inhibited the grain growth of the composition $Pb(Mg_{0.15} W_{0.15})Ti_{0.35}-Zr_{0.35}O_3$ +2wt% excess PbO. The dielectric and piezoelectric properties of the composition $Pb(Mg_{0.15} W_{0.15})Ti_{0.35}-Zr_{0.35}O_3$ were improved by the addition of 2wt% excess PbO and proper additive. The electromechanical planar coupling factor of 0.65 and mechnical quality factor of 390 could be obtained by adding 5wt% $Nb_2O_5$ to the composition 2wt% excess PbO+$Pb(Mg_{0.15} W_{0.15})Ti_{0.35}-Zr_{0.35}O_3$.

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Sintering and Microstructure of $Ce-TZP/Al_2O_3$ Ceramic Composite ($Ce-TZP/Al_2O_3$ 세라믹 복합재료의 소결과 미세구조)

  • 박홍채;홍상희;이윤복;오기동
    • Journal of the Korean Ceramic Society
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    • v.31 no.7
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    • pp.703-714
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    • 1994
  • Sintering and microstructure of Ce-TZP/Al2O3 composite with $\alpha$-Al2O3 matrix containing dispersed 5~50 vol% ZrO2 were discussed. Sintered density was increased with elevating forming pressure in range of 6~300 MPa and about >99.2% of theoretical density was obtained at 1$600^{\circ}C$ for 2h in case of 300 MPa of 6~300 MPa uniaxially cold-pressed compacts containing 20 vol% ZrO2. All kinds of different batch composition exhibited nearly the same shrinkage behaviour with end-point shrinkage between 20 and 24%, and had the maximum shrinkage rate (0.41~0.54%/min) around 140$0^{\circ}C$. Grain growth was occurred faster in $\alpha$-Al2O3 than in {{{{ gamma }}-Al2O3 starting matrix during sintering at 1$600^{\circ}C$. Bimodal pore size distribution of interaglomerate pores with size of 0.03~0.2 ${\mu}{\textrm}{m}$ and of interaglomerate pores with size of around 60 ${\mu}{\textrm}{m}$ was obtained in Ce-TZP/$\alpha$-Al2O3 composite sintered at 130$0^{\circ}C$. But unimodal pore size distribution with around 0.1 ${\mu}{\textrm}{m}$ was observed in Ce-TZP/{{{{ gamma }}-Al2O3 composite sintered at the same temperature. Microcracks were occurred due to the tlongrightarrowm transformation of ZrO2 on cooling process.

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Fabrication of Functionally Gradient Porous Al2O3-(t-ZrO2)/HAp Composites and their In-Vitro Study (조성 경사구조를 갖는 다공질 Al2O3-(t-ZrO2)/HAp 복합체의 제조 및 In-Vitro 실험)

  • Kim, Ki-Ho;Kim, Young-Hee;Song, Ho-Yeon;Lee, Byong-Taek
    • Journal of the Korean Ceramic Society
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    • v.43 no.8 s.291
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    • pp.504-508
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    • 2006
  • Functionally gradient porous $Al_2O_3-(t-ZrO_2)/HAp$ composites consist of 3 layers were fabricated using the multi-pass extrusion process at the various temperatures. The continuous pores were homogeneously formed in the $2^{nd}$ passed samples and their size was about $180{\mu}m$ in diameter. In the porous composites sintered at $1200-1400^{\circ}C$, the relative density and bending strength increased with the sintering temperature. The maximum values of relative density and bending strength in the $2^{nd}$ passed $Al_2O_3-(t-ZrO_2)/HAp$ composites were 62.2% and 107.8 MPa, respectively. In order to investigate the growth behavior of osteogenic cells on the functionally gradient porous $Al_2O_3-(t-ZrO_2)/HAp$ composites, an in vitro test was performed, using human osteoblast-like MG-63 cells. The cells were well attached and grown on the rough surface of the inside of the functionally gradient porous body.

Geochemical Dispersion and Enrichment of Fluvial Sediments Depending on the Particla Size Distribution (입도분포에 따른 하상퇴적물의 지구화학적 분산 및 부화)

  • 이현구
    • Economic and Environmental Geology
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    • v.32 no.3
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    • pp.247-260
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    • 1999
  • Geochermical characteristics of the fluvial sediments deprnding on particle size distribution size were investigated in the respect of majir, minor and rare eath element chemisitry. Ratios of $Al_{2}O_{3}/Na_{2}O$ and $K_{2}O/Na_{2}O$ of the sediments show the homogeneous valus, and partly positive correlation with $SiO_{2}/Al_{2}O_{3}$, respecively. Characteristics of minor element ratios (V/Ni, Cr/V, Ni/Co and Zr/Hf)are within the lower and narrow range. Thesesuggested that sediment sources may be acidic to intermediate granitic rock, and may be explained by simple weathering and sedimentation. With increasing SiO2 contents, concentrations of $Al_{2}O_{3}$, $Fe_{2}O_{3}$, CaO and MgO decreased, but those of $K_{2}O$ and $Na_{2}O$ increased, Concentrations of Ba, Be, Cs, Cu, Li, Ni, Sr, V and Zr show comparatively normal negative and some positive trends. Compared with the mean composition of granite, concentrations of $Al_{2}O_{3}$, $Fe_{2}O_{3}$, MnO, CaO and MgO in the sediments of the study area were highly enriced. Among some minor and rare earth elements, concentrations of As, Cd, Cu, and V were enriched, but those of Be, Ce, Rb, Sc, Sr and Zn were depleted when compared with average composition of granite. By decreasing of particle size fractions, SiO2, Rb and Sr conterts decreased, but concentrations of $Al_{2}O_{3}$, $Fe_{2}O_{3}$, CaO, MgO, $TiO_{2}$, MgO, $P_{2}O_{5}$, Be, Cu, Hf, Pb, V and Zr increased. From the correlations between particle size fractions and element concenreations, some elements of $Fe_{2}O_{3}$, CaO, MgO, $P_{2}O_{5}$, Cu, Ni, Zn and Zr showed typical trends in the secondary contramination sediments. These trends are typically shown under 100 mesh fractions. It indicates that the fraction of minus 100 mesh is the optimum size fraction for geochemical and environmental survey.

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A Study on the joining of $Al_2O_3$ to STS 304 with using Cu-7.5wt% Zr Insert metal (Cu-7.5wt% Zr 삽입 금속을 이용한 $Al_2O_3$-STS 304 접합체 계면 조직에 관한 연구)

  • 김병무;한원진;강정윤;이상래
    • Journal of Welding and Joining
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    • v.11 no.1
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    • pp.62-72
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    • 1993
  • Recently there is an increased interest in joining of ceramics to metals and brazing now an accepted method of joining for a wide variety of ceramic to metal combination. The present research work is aimed at establishing the basis of the metal-ceramic joining of $Al_{2}$O$_{3}$ to STS 304 with using Cu-7.5wt% Zr insert metals. Also the microstructures of the brazed joints were observed by using optical microscope and SEM and the reaction products were analyzed by using EDX, WDX and XRD. As a result, the following findings were obtained. The reaction layers of the brazed joints of $Al_{2}$O$_{3}$ to STS 304 are composed of four layers at the bonded interlayer. Double reaction layers are formed at the interface of $Al_{2}$O$_{3}$ insert metal. Layer I was composed of ZrO$_{2}$ particles, Fe-Cr-Ni compounds in Cu matrix, while layer II ZrO$_{2}$ band phase containing Fe-Cr-Ni compounds.

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Synthesis of Mullite Powder from Alkoxides and the Properties of the Mullite-Zircocnia Composites (알콕사이드로부터 Mullite 분말의 합성 및 Mullite-Zirconia 복합체의 특성)

  • 함종근;이홍림
    • Journal of the Korean Ceramic Society
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    • v.27 no.2
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    • pp.201-210
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    • 1990
  • The mullite-15v/o ZrO2 composites were prepared by dispersing ZrO2-3m/o Y2O3 powders into the mullite matrix in order to improve the mechanical properties of the mullite. The densification and retention of t-ZrO2 in the matrix of synthetic mullite were also investigated. From IR spectroscopic analysis, the obtained amorphous SiO2-Al2O3 powder was observed to have Si-O-Al chemical bond in its structure which might result in the homogeneous mullite composition. The lattice parameter of the mullite powder calcined above 130$0^{\circ}C$ (a0=7.5468$\AA$) is nearly close to the value of stoichiometric mullite (71.8wt% Al2O3, a0=7.5456$\AA$). The sintering behavior, microstructure, flexural strength and fracture toughness of the mullite and mullite-15v/o ZrO2 composites have been studied. The mullite-15v/o ZrO2(+3m/o Y2O3) ceramics with relative densities of 96% were obtained when sintered at 1$600^{\circ}C$. The flexural strength and fractrue toughness of the composites sintered at 1$600^{\circ}C$(calcination temperature of mullite powders ; 125$0^{\circ}C$) had maximum values of 307MPa and 2.50MPa.m1/2, respectively. The fracture toughness improvement in the mullite-ZrO2 cmoposite is assumed to be resulted from the combined effect of the stress-induced phase transformation of tetragonal ZrO2 and the crack deflection due to microcracking by the monoclinic ZrO2 formation.

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Mechanical Behavior of Directionally Solicified (Y2O3)ZrO2/Al2O3 Eurtctic Fibers

  • Park, Deok-Yong;Yang, Jenn-Ming
    • Journal of the Korean Ceramic Society
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    • v.41 no.1
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    • pp.1-8
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    • 2004
  • The microstructural features and mechanical behavior of directionally solidified $(Y_2O_3)ZrO_2/Al_2O_3$ eutectic fibers after extended beat treatment in oxidizing environment were investigated. The fiber was grown continuously by an Edge-defined Film-fed Growth (EFG) technique. The microstructure was characterized using X-Ray Diffraction (XRD) and Scanning Electron Microscopy(SEM). The microstructure of the fiber in the as-fabricated state consists of highly oriented colonv and fine lamellar microstructure along the fiber axis. Tensile strength of the $(Y_2O_3)ZrO_2/Al_2O_3$ eutectic fiber remained unchanged with heat treatment at temperatures between $1200^{\circ}C$ and $1500^{\circ}C$ up to 300h. The weibulls modulus remained fairly constant after extended thermal exposure. The fracture toughness and crack propagation behavior were investigated. The fracture toughness ($K_{1C}$) of the $(Y_2O_3)ZrO_2/Al_2O_3$ eutectic fiber in the as-fabricated state were measured to be 3.6 ${\pm}$ 0.5 MPa${\cdot}m^{1/2}$ by an indentation technique and 2.2 ${\pm}$ 0.2 MPa${\cdot}m^{1/2}$ by assuming elliptical flaw of a semi-infinite solid, respectively. The $(Y_2O_3)ZrO_2/Al_2O_3$ eutectic fiber showed a radial (Palmqvist) crack type and exhibited an orthotropic crack growth behavior under 100 g load.

Electrical Resistivity and Fracture Toughness of SiC-ZrB2

  • Shin, Yong-Deok;Ju, Jin-Young;Kwon, Ju-Sung
    • The Korean Journal of Ceramics
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    • v.5 no.4
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    • pp.400-403
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    • 1999
  • The mechanical and electrical properties of hot-pressed and annelaed $\beta$-SiC+39vol.% $ZrB_2$ electroconductive ceramic composites were investigated as a function of the liquid forming additives of $Al_2O_3+Y_2O_3$(6:4 wt%). In this microstructures, no reactions and elongated $\alpha$-SiC grains with equiaxed $ZrB_2$ grains were observed between $\beta$-SiC and $ZrB_2$. The properties of the $\beta$-SiC+39vol.%$ZrB_2$ composites with 4wt% $Al_2O_3+Y_2O_3$ at R.T. are as follows: fracture toughness is 6.37 MPa.m1/2, electical resistivity is $1.51\times10^{-4}\Omega \cdot\textrm{cm}$ and the relative density is 98.6% of the theoretical density. The fracture toughness of the $\beta$-SiC+39 vol.% $ZrB_2$ composites were weakly decreased with increasing amount of $Al_2O_3+Y_2O_3$ additives. Internal stresses due to the difference of $\beta$-SiC and $ZrB_2$ thermal expansion coefficient and elastic modulus mismatch appeared to contribute to fracture toughening in $\beta$-SiC+39vol.%$ZrB_2$ electroconductive ceramic composites.

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Brazing characteristics of $ZrO_2$ and Ti-6Al-4V brazed joints with increasing temperature (브레이징 온도 변화에 따른 $ZrO_2$와 Ti-6Al-4V의 접합 특성)

  • Kee, Se-Ho;Park, Sang-Yoon;Heo, Young-Ku;Jung, Jae-Pil;Kim, Won-Joong
    • The Journal of Korean Academy of Prosthodontics
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    • v.50 no.3
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    • pp.169-175
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    • 2012
  • Purpose: In this study, brazing characteristics of $ZrO_2$ and Ti-6Al-4V brazed joints with increasing temperature were investigated. Materials and methods: The sample size of the $ZrO_2$ was $3mm{\times}3mm{\times}3mm$ (thickness), and Ti-6Al-4V was $10mm(diameter){\times}5mm(thickness)$. The filler metal consisted of Ag-Cu-Sn-Ti was prepared in powder form. The brazing sample was heated in a vacuum furnace under $5{\times}10^{-6}$ torr atmosphere, while the brazing temperature was changed from 700 to $800^{\circ}C$ for 30 min. Results: The experimental results shows that brazed joint of $ZrO_2$ and Ti-6Al-4V occurred at $700-800^{\circ}C$. Brazed joint consisted of Ag-rich matrix and Cu-rich phase. A Cu-Ti intermetallic compounds and a Ti-Sn-Cu-Ag alloy were produced along the Ti-6Al-4V bonded interface. Thickness of the reacted layer along the Ti-6Al-4V bonded interface was increased with brazing temperature. Defect ratios of $ZrO_2$ and Ti-6Al-4V bonded interfaces decreased with brazing temperature. Conclusion: Thickness and defect ratio of brazed joints were decreased with increasing temperature. Zirconia was not wetting with filler metal, because the reaction between $ZrO_2$ and Ti did not occur enough.