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  • 1
    Electronic Resource
    Electronic Resource
    Diffusion Controlled Abnormal Grain Growth in Ceramics (2007)
    s.l. ; Stafa-Zurich, Switzerland
    Materials science forum Vol. 558-559 (Oct. 2007), p. 1227-1236 
    Details
    ISSN: 1662-9752
    Source: Scientific.Net: Materials Science & Technology / Trans Tech Publications Archiv 1984-2008
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: The grain growth kinetics of silica and calcia doped alumina at 1400oC and their grainboundary complexion is characterized. These data are compared to predictions of both diffusioncontrolled and nucleation limited interface controlled grain growth theory. It is deduced from theindicators that the mechanism for normal and abnormal grain growth in these aluminas is diffusioncontrolled
    Type of Medium: Electronic Resource
    URL: http://www.tib-hannover.de/fulltexts/2011/0528/02/17/transtech_doi~10.4028%252Fwww.scientific.net%252FMSF.558-559.1227.pdf
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  • 2
    Electronic Resource
    Electronic Resource
    Compositional control of ferroelectric fatigue in perovskite ferroelectric ceramics and thin films (1994)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 76 (1994), S. 5394-5398 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The mechanism and control of ferroelectric polarization fatigue (loss of polarization with cycling) in donor- and acceptor-doped BaTiO3 ceramics and Pb(Zr1−xTix)O3 (PZT) thin films has been investigated. Experimental results clearly demonstrate that fatigue behavior is related to the defects within the materials. Donor-doped BaTiO3 ceramics showed significantly improved fatigue characteristics when compared with acceptor-doped materials. A similar but reduced effect has been observed in donor-doped PZT thin films. The electric-field-assisted migration of charged species within ferroelectric materials may be responsible for the degradation/fatigue behavior. Results support the expectation that oxygen vacancies play an important role in fatigue that occurs as a result of polarization switching.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.357194
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  • 3
    Electronic Resource
    Electronic Resource
    Effect of Nd2O3 Doping on the Densification and Abnormal Grain Growth Behavior of High-Purity Alumina (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: The densification behavior and microstructural development of high-purity Al2O3 doped with different levels of Nd2O3 were investigated. Dopant levels ranged from 100–1000 ppm (Nd/Al atomic ratio). The densification behavior of the doped powders was studied using constant heating rate dilatometry. It was found that neodymium additions inhibited densification, with a corresponding increase in the apparent activation energy. The level of grain-boundary segregation was studied using high-resolution analytical electron microscopy. At dilute concentrations, the degree of neodymium grain-boundary excess was found to be consistent with a simple geometrical model relating this quantity to the overall dopant concentration and average grain size. For certain combinations of dopant level and heat treatment, supersaturation of the grain boundaries was observed, which was found to correlate with the onset of abnormal grain growth. Possible explanations for this behavior are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1551-2916.2004.00378.x
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  • 4
    Electronic Resource
    Electronic Resource
    Influence of Excess PbO Additions on {111} Single-Crystal Growth of Pb(Mg1/3Nb2/3)O3–35 mol% PbTiO3 by Seeded Polycrystal Conversion (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 influence of additions of excess PbO to Pb(Mg1/3Nb2/3)O3–35 mol% PbTiO3 (PMN–35PT) on {111} single-crystal growth by seeded polycrystal conversion was studied in the range of 0–5 vol% PbO. PbO volatilization and hence weight loss during annealing was controlled effectively by a double-crucible type of arrangement. PbO additions increased boundary mobility significantly in PMN–35PT, thus facilitating single-crystal growth by seeded polycrystal conversion (SPC). This is attributed to the formation of a boundary wetting PbO-based liquid phase. The growth process occurs very rapidly initially, after which it slows down. This is presumably due to both a decrease in the driving force for boundary migration because of an increase in matrix grain size, and a transition to lower mobility facets. It is also shown that for a given annealing time, the size of the grown crystal scales with the lateral dimensions of the seed crystal.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1151-2916.2003.tb03627.x
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  • 5
    Electronic Resource
    Electronic Resource
    Kinetics of {001} Pb(Mg1/3Nb2/3)O3–35 mol% PbTiO3 Single Crystals Grown by Seeded Polycrystal Conversion (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 kinetics of {001}-oriented Pb(Mg1/3Nb2/3)O3–35 mol% PbTiO3 (PMN–35PT) single crystals grown by seeded polycrystal conversion were systematically quantified as a function of excess PbO liquid phase. The coarsening behavior of the corresponding matrix grains was similarly quantified. Single-crystal seed plates were embedded in a matrix of PMN-35PT with varying amounts of liquid phase (PbO) content in the range of 0 to 5 vol% and annealed at 1150°C for 0–10 h. Apparent maxima in the growth rates were observed at a PbO content of ∼3 vol% for both the single crystal and matrix grains. In both cases, the growth data were found to most closely follow cubic growth kinetics. Implications regarding the effect of PbO volume fraction on the matrix and single-crystal growth mechanisms are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1151-2916.2003.tb03628.x
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  • 6
    Electronic Resource
    Electronic Resource
    Micromechanics of Deformation in Porous Liquid-Phase-Sintered Alumina under Hertzian Contact (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: A series of fine-grained porous alumina samples, with and without a liquid phase, were fabricated in compositions matched closely to commercially available alumina used as microelectronic substrates. Hertzian indentation on monolithic specimens of the glass-containing samples produced a greater quasi-ductile stress–strain response compared with that observed in the pure alumina. Maximum residual indentation depths, determined from surface profilometry, correlated with the stress–strain results. Moreover, microstructural observations from bonded interface specimens revealed significantly more damage in the form of microcracking and under extreme loading, pore collapse, in the glass-containing specimens. The absence of the typical twin faulting mechanism observed for larger-grained alumina suggests that the damage mechanism for quasi-ductility in these fine-grained porous aluminas was derived from the pores acting as a stress concentrator and the grain boundary glass phase providing a weak path for short crack propagation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1151-2916.2001.tb00925.x
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  • 7
    Electronic Resource
    Electronic Resource
    Alumina Agglomerate Effects on Toughness-Curve Behavior of Alumina–Mullite Composites (2000)
    Westerville, Ohio : American Ceramics Society
    Journal of the American Ceramic Society 83 (2000), 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: Toughness-curve (T-curve) behavior of composites of spherical, polycrystalline, coarse-grained, alumina agglomerates dispersed throughout a constant-toughness, fine-grained, 50–50 vol% alumina–mullite matrix has been evaluated as a function of agglomerate content for the range 15 to 45 vol%. T-curve behavior was evaluated using the indentation-strength method. Increasing alumina agglomerate content resulted in a progressive increase of large indentation load strengths with negligible change of plateau strength levels at small indentation loads. This behavior is consistent with underlying T-curves that rise to greater values and are shifted toward longer crack lengths with increasing agglomerate content, suggesting that both bridge spacing and bridge potency increase with increasing agglomerate content over the range tested. The proposed relationships between bridge spacing and agglomerate content, and bridge potency and agglomerate content, are rationalized in terms of residual stress considerations. The indentation-strength data also demonstrated that the composite containing the greatest alumina agglomerate content, 45 vol%, exhibited the greatest flaw tolerance.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1151-2916.2000.tb01687.x
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  • 8
    Electronic Resource
    Electronic Resource
    Effect of Annealing Environment on the Crack Healing and Mechanical Behavior of Silicon Carbide-Reinforced Alumina Nanocomposites (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: The crack healing and strength behavior of an alumina-silicon carbide (Al2O3-SiC) nanocomposite (Al2O3+ 5 vol% 0.2 μm SiC particles) has been studied, as a function of the crack size and the annealing environment. Results show that annealing treatments can significantly increase the indentation strength. The annealing atmosphere has a profound influence on the extent of crack healing and the degree of strength recovery. Annealing in argon results in a strength increase of 50%, whereas annealing in air yields a three-fold improvement in the indentation strength. Scanning electron microscopic observation has shown that healing of indentation cracks occurs in both environments, with the greater degree of healing occurring during annealing in air. Implications of the findings to the strengthening mechanism in Al2O3 (SiC) nanocomposites will be discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1151-2916.1998.tb02469.x
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  • 9
    Electronic Resource
    Electronic Resource
    Toughness-Curve Behavior of an Alumina-Mullite Composite (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: Toughness-curve (T- or R-curve) behavior of a composite of 30 vol%, polycrystalline, coarse-grained, spherical alumina agglomerates dispersed throughout a fine-grained, 50/50 vol% alumina-mullite matrix, and that of its microstructural end-members (100% matrix and 100% alumina), were studied using the indentation-strength-in-bending technique. T-curves were deconvoluted from indentation-strength data using an indentation fracture mechanics model. The monolithic matrix and alumina exhibited an invariant toughness and a moderate T-curve, respectively. In comparison, the composite exhibited a pronounced T-curve. The T-curve of the composite is best explained as deriving from the interaction of a propagating crack with the alumina agglomerates: crack propagation experiments revealing two possible toughening mechanisms-intra-agglomerate frictional grain bridging and elastic bridging ligaments in the matrix that appeared to be associated with alumina agglomerates. Rule-of-mixtures toughness calculations indicated that intra-agglomerate bridges could account for only a fraction of the toughening exhibited by the composite. It is suggested that the extra toughening arises from the elastic bridging ligaments.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1151-2916.1998.tb02668.x
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  • 10
    Electronic Resource
    Electronic Resource
    Controlled Firing of Reaction-Bonded Aluminum Oxide (RBAO) Ceramics: Part II, Experimental Results (1999)
    Westerville, Ohio : American Ceramics Society
    Journal of the American Ceramic Society 82 (1999), 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 reaction-bonded aluminum oxide (RBAO) process is an attractive alternative to conventional processing of ceramics, because of advantages such as lower costs, enhanced green machinability, near-net-shape forming, and broad microstructural variability. However, various problems are still encountered in the production of RBAO ceramics. Part I of the paper presented model predictions that may allow for the controlled firing of RBAO ceramics. The current work investigates the reaction behavior of RBAO ceramics under the model-predicted conditions (i.e., for varying oxygen content, heat loss, heating cycles, and scale) via thermogravimetry, differential thermal analysis, and analysis of samples that have been fired in a box furnace. By controlling the reaction, one can produce large, crack-free RBAO ceramics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1151-2916.1999.tb01852.x
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