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  • 1
    Electronic Resource
    Electronic Resource
    Abnormal Grain Growth Occurring at the Surface of a Sintered BaTiO3 Specimen (2004)
    Westerville, Ohio : American Ceramics Society
    Journal of the American Ceramic Society 87 (2004), S. 0 
    Details
    ISSN: 1551-2916
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: When a BaTiO3 powder compact was sintered in air, the abnormal grain growth (AGG) was observed to occur at the surface of the specimen. The BaO evaporation from the surface and consequent formation of eutectic liquid is suggested to be the cause of AGG. When the evaporation of BaO during sintering was prevented by embedding the specimen in the same powder, no AGG was observed to occur.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1551-2916.2004.01779.x
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  • 2
    Electronic Resource
    Electronic Resource
    Effect of the Liquid-Forming Additive Content on the Kinetics of Abnormal Grain Growth in Alumina (2003)
    Westerville, Ohio : American Ceramics Society
    Journal of the American Ceramic Society 86 (2003), S. 0 
    Details
    ISSN: 1551-2916
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Alumina specimens with various amounts of CaO and SiO2 (1:2 ratio) were prepared, and their abnormal grain growth (AGG) kinetics were investigated. A plot of the area fraction covered by abnormal grains versus log (sintering time) had a sigmoidal shape with an apparent incubation period before the onset of AGG. The overall kinetics of AGG was similar to that of a phase transformation controlled by nucleation and growth. The incubation time and the end point of AGG were strongly dependent on the amount of liquid-forming additives. Correspondingly, the final microstructure was affected by the liquid content: a large grain size and a high aspect ratio at low liquid content and a small grain size and a low aspect ratio at high liquid content.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1151-2916.2003.tb03486.x
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  • 3
    Electronic Resource
    Electronic Resource
    Effect of Titania and Lithia Doping on the Boundary Migration of Alumina under an Electric Field (2003)
    Westerville, Ohio : American Ceramics Society
    Journal of the American Ceramic Society 86 (2003), S. 0 
    Details
    ISSN: 1551-2916
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Boundary migration under an electric field was investigated for pure, TiO2-doped, and Li2O-doped Al2O3 specimens. Boundary migration rates in TiO2-doped and Li2O-doped Al2O3 specimens were much faster compared with that of pure Al2O3. In all specimens, the migration rate was observed to depend on the applied bias direction. Compared with pure Al2O3, the dependence of boundary migration on bias direction became more pronounced in TiO2-doped Al2O3 but less pronounced in Li2O-doped Al2O3. The results were explained in terms of the variation of grain sizes, mobility, and electrostatic potential of boundaries because of doping.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1151-2916.2003.tb03352.x
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  • 4
    Electronic Resource
    Electronic Resource
    Alternative Explanation for the Role of Magnesia in the Sintering of Alumina Containing Small Amounts of a Liquid Phase (2003)
    Westerville, Ohio : American Ceramics Society
    Journal of the American Ceramic Society 86 (2003), S. 0 
    Details
    ISSN: 1551-2916
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: The microstructural evolution during sintering of Al2O3 was investigated to determine the role of MgO additive, particularly when its concentration is very low (〈200 ppm). Compared with specimens without MgO, a few Al2O3 grains were observed to grow enormously after the addition of 50 or 100 ppm MgO. When MgO content was increased to 200 ppm, on the other hand, the overall grain growth process was accelerated and many growing grains impinged on each other. In this case, therefore, a fine and unimodal grained microstructure was obtained. Sintering of Al2O3 in a MgO atmosphere further supported the promotion of grain growth by MgO. It is proposed that MgO promotes the grain growth of Al2O3 either by lowering the edge energy or by roughening the interface structure.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1151-2916.2003.tb03351.x
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  • 5
    Electronic Resource
    Electronic Resource
    Equilibrium Shape of Internal Cavities in Ruby and the Effect of Surface Energy Anisotropy on the Equilibrium Shape (2002)
    Westerville, Ohio : American Ceramics Society
    Journal of the American Ceramic Society 85 (2002), S. 0 
    Details
    ISSN: 1551-2916
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Cavities formed in ruby (99.46Al2O3·0.54Cr2O3) by the healing and annealing of indentation cracks at 1600°C are more equiaxed than similar cavities in sapphire. Surface energies for the observed facet planes (R, S, and A) relative to the surface energy of the basal plane, C, were γA/C= 1.00 ± 0.03, γR/C= 1.05 ± 0.07, and γS/C= 1.02 ± 0.04, with the uncertainty representing 95% confidence limits. Thus, the surface energies of all observed facets were statistically indistinguishable. Unlike sapphire, P-plane facets were not observed. The substantial rounding of the cavities in ruby indicated that portions of the Wulff shape were above the roughening transition temperature. Thus, even though Cr2O3 and Al2O3 form ideal solutions, Cr3+ ions are sufficiently surface active to modify the relative free energy of the surfaces.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1151-2916.2002.tb00362.x
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  • 6
    Electronic Resource
    Electronic Resource
    Inhomogeneity of Grain-Boundary Resistivity in Calcia-Stabilized Zirconia (2002)
    Westerville, Ohio : American Ceramics Society
    Journal of the American Ceramic Society 85 (2002), S. 0 
    Details
    ISSN: 1551-2916
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Impedance spectroscopy with millimeter-scale electrodes was used to determine the local grain-boundary resistivity (ρgb) of a 1-mol%-Al2O3-doped CaO-stabilized ZrO2 (CSZ) specimen. A much higher ρgb at the specimen surface was observed compared with that of the specimen interior. The result was mainly due to the difference in the dihedral angle of the intergranular phase, which was ∼20° at the surface and ∼100° at the interior.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1151-2916.2002.tb00324.x
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  • 7
    Electronic Resource
    Electronic Resource
    Scavenging of Siliceous Grain-Boundary Phase of 8-mol%-Ytterbia-Stabilized Zirconia without Additive (2001)
    Westerville, Ohio : American Ceramics Society
    Journal of the American Ceramic Society 84 (2001), S. 0 
    Details
    ISSN: 1551-2916
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: The grain-boundary conductivity (ςgb) of 8-mol%-ytterbia-stabilized zirconia increased markedly with heat treatment between 1000° and 1300°C with a slow heating rate (0.1°C/min) before sintering. The extent of the ςgb improvement was the same or larger than that via Al2O3 addition. The heat treatment did not affect the grain-interior conduction when sintered at 1600°C, while Al2O3-derived scavenging significantly did, given the larger increment of total conductivity in the heat-treated sample. The formation of a silicon-containing phase in a discrete form was suggested as a possible route of scavenging the resistive phase from the correlation between average grain size and ςgb.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1151-2916.2001.tb01086.x
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  • 8
    Electronic Resource
    Electronic Resource
    Effect of Surface Impurities on the Microstructure Development during Sintering of Alumina (2001)
    Westerville, Ohio : American Ceramics Society
    Journal of the American Ceramic Society 84 (2001), S. 0 
    Details
    ISSN: 1551-2916
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Microstructural evolution during sintering of alumina powder compacts prepared by cold isostatic pressing (CIP) was monitored. For CIP, rubber molds lubricated with silicone oil were used so that a very small amount of impurity was introduced to the surface of the powder compacts. During sintering at 1600°C, grain growth in the surface region was inhibited up to sintering for 1 h, but subsequently abnormal grain growth occurred. In the inner region, however, the grains grew uniformly without abnormal grain growth. Impurities that initially drag the boundary migration but form liquid at the end are suggested to cause abnormal grain growth.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1151-2916.2001.tb00846.x
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  • 9
    Electronic Resource
    Electronic Resource
    Morphology and Phase Stability of Nitrogen–Partially Stabilized Zirconia (N-PSZ) (2001)
    Westerville, Ohio : American Ceramics Society
    Journal of the American Ceramic Society 84 (2001), S. 0 
    Details
    ISSN: 1551-2916
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: The surface layer of yttria-doped tetragonal zirconia materials that have been heat-treated with zirconium nitride was observed to consist of a nitrogen-rich cubic matrix with nitrogen-poor tetragonal precipitates. The precipitates had a thin, oblate-lens shape, similar to those observed in magnesia–partially stabilized zirconia. Because of the fast diffusion of N4− ions, the precipitates grew rather large, up to ∼5 μm in length, and remained stabilized in the tetragonal form at room temperature. Because the nitrided layer grew in the two-phase field, the size and distribution of the precipitates each was very irregular. The nitrogen content was observed to determine the proportion of cubic and tetragonal phases in the same way as in conventional cation-stabilized partially stabilized zirconia. A ternary phase diagram for the zirconium(yttrium)–nitrogen–oxygen system was suggested to explain the concentration gradient in the cubic matrix and the phase distribution of the nitrided layer.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1151-2916.2001.tb00626.x
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  • 10
    Electronic Resource
    Electronic Resource
    Enhanced Densification of In2O3 Ceramics by Presintering with Low Pressure (5 MPa) (1998)
    Westerville, Ohio : American Ceramics Society
    Journal of the American Ceramic Society 81 (1998), S. 0 
    Details
    ISSN: 1551-2916
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Sintering of In2O3 has been carried out in air to full density. Because of the difference in densification between the agglomerates and the matrix, large interagglomerate pores were observed to form at the initial stage of sintering. Such pore formation could be prevented by applying a small external pressure which resulted in the beneficial rearrangement of agglomerates.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1151-2916.1998.tb02650.x
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