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  • 1
    Electronic Resource
    Electronic Resource
    Phase distribution studies using energy dispersive X-ray spectral analysis (1985)
    Springer
    Journal of materials science 4 (1985), S. 1437-1441 
    Details
    ISSN: 1573-4811
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00721357
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  • 2
    Electronic Resource
    Electronic Resource
    Transformation toughening (1982)
    Springer
    Journal of materials science 17 (1982), S. 255-263 
    Details
    ISSN: 1573-4803
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The critical stress-intensity factor,K c, of materials containing tetragonal ZrO2 was found to decrease with increasing temperature and CeO2 alloying additions, as predicted by theory. The temperature dependence ofK c was related to the temperature dependence of the chemical free-energy change associated with tetragonal-monoclinic transformation. Good agreement with thermodynamic data available for pure ZrO2 was obtained when the size of the transformation zone associated with the crack was equated to the size of the ZrO2 grains. TheK c against CeO2 addition data was used to estimate the tetragonal, monoclinic, cubic eutectoid temperature of 270° C in the ZrO2-CeO2 binary system.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00809061
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  • 3
    Electronic Resource
    Electronic Resource
    Cracking in particulate composites due to thermalmechanical stress (1981)
    Springer
    International journal of fracture 17 (1981), S. 483-491 
    Details
    ISSN: 1573-2673
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Description / Table of Contents: Résumé Des calculs numériques de la relaxation d'énergie de déformation dans le cas de fissure se propageant au voisinage de l'interface entre une particule sphérique et une matrice ont été utilisés en vue de déterminer la fonction de relaxation de vitesse d'énergie de déformation dans le cas où les contraintes sont créées par une contraction thermique différentielle. Cette fonction a été trouvée telle qu'elle présente un maximum suivant la longueur de fissure et que ce maximum est compatible avec les conditions théoriques d'extension de fissure et d'arrêt de fissure proposées par Lange. Les calculs montrent qu'il existe une dimension critique de particule en-dessous de laquelle l'extension de fissure ne se produit pas pour en système donné de contrainte thermomécanique. La dimension critique de particule que l'on peut prédire est en bonne corrélation avec les résultats expérimentaux.
    Notes: Abstract Numerical computations of the strain energy release rate for cracks propagating around the interface between a spherical particle and a matrix have been used to determine the strain energy release rate function for the case where stresses arise due to differential thermal contraction. The strain-energy release rate function was found to exhibit a maximum as a function of crack length consistent with the theoretical conditions for crack extension and arrest proposed by Lange. The calculations show that a critical particle size exists below which crack extention does not occur for a given thermalmechanical stress. The predicted critical particle size correlates well with experimental results.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00033343
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  • 4
    Electronic Resource
    Electronic Resource
    Compressive creep of Si3N4/MgO alloys (1982)
    Springer
    Journal of materials science 17 (1982), S. 3637-3640 
    Details
    ISSN: 1573-4803
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The activation energy of two Si3N4/MgO materials, fabricated in the Si3N4-Si2N2O-Mg2SiO4 compatibility triangle of the Si-Mg-O-N system, was determined between 1300 and 1400° C under a compressive stress of 275 MPa. The activation energy of the material previously shown to exhibit pure diffusional creep was determined to be 660 kJ mol−1, whereas the material shown to exhibit extensive cavitational creep had an activation energy of 1080 kJ mol−1. These results are compared with results obtained by others for densification and slow crack growth.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00752208
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  • 5
    Electronic Resource
    Electronic Resource
    Stengthening of polyphase Si3N4 materials through oxidation (1983)
    Springer
    Journal of materials science 18 (1983), S. 1497-1505 
    Details
    ISSN: 1573-4803
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Specimens of various polyphase Si3N4 materials fabricated in the Si-Mg-O-N system, and a commercial Si3N4 material were subjected to oxidation treatments prior to flexural strength determinations at 1400° C. It was demonstrated that a pre-oxidation treatment could significantly improve the high-temperature strength. The compositional change induced by oxidation which can decrease the volume fraction of the viscous phase present in these materials at high temperatures is believed to be responsible for the observed strengthening.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01111970
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  • 6
    Electronic Resource
    Electronic Resource
    Effects of attrition milling and post-sintering heat treatment on fabrication, microstructure and properties of transformation toughened ZrO2 (1986)
    Springer
    Journal of materials science 21 (1986), S. 768-774 
    Details
    ISSN: 1573-4803
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The effect of attrition milling and post-sintering heat treatment on the fabrication, phase relations, microstructure and properties of ZrO2 (+2.3vol% Y2O3) powder used to produce a transformation toughened material was examined. Powder used to fabricate the unmilled material was treated and consolidated by a colloidal method. The same powder, treated and consolidated by the same method, but ball milled in a commercial alumina mill before consolidation, was used to fabricate the milled material. Both materials were sintered at 1400° C for 1 h and then heat treated at higher temperatures. Milling introduced Al2O3 inclusions (〈 1 vol%) and a glass phase (7 to 10 vol%). The milled powder was more difficult to sinter and exhibited more bloating (density decrease) during subsequent heat treatment. Transmission electron microscopy observations indicated that the larger glass content of the milled material beneficially reduced residual stresses that arose due to thermal contraction anistropy. Post-sintering heat treatment at temperatures 〉 1450° C produced detectable amounts of cubic ZrO2 consistent with previously reported phase studies of the ZrO2-Y2O3 system. The development of a bimodal grain structure was concurrent with the formation of detectable cubic phase. The larger grains in this bimodal distribution were primarily observed on the external surface and co-ordinating pores produced during the post-sintering heat treatments which were responsible for the bloating phenomenon. It is hypothesized that the pores were produced by the release of high pressure oxygen during cubic phase formation. Both fracture toughness (K c) and hardness of the as-sintered materials were unaffected by milling. Hardness decreased with bloating and the decrease was more pronounced for the milled material which exhibited more bloating.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01117352
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  • 7
    Electronic Resource
    Electronic Resource
    Diffusion limited crystallization and phase partitioning in ZrO2-metal oxide binary systems (1994)
    Springer
    Journal of sol gel science and technology 2 (1994), S. 317-321 
    Details
    ISSN: 1573-4846
    Keywords: diffusion-limited crystallization ; phase diagrams ; metastability ; ZrO2-metal oxide
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Chemical routes to synthesize inorganics can start with solutions where multiple elements remain well mixed during liquid evaporation, precursor decomposition and crystallization. Because crystallization generally occurs at temperatures where diffusion is very limited, a single phase can crystallize with a greatly extended solid-solution that does not achieve its equilibrium phase assemblage until much higher temperatures where diffusion is no longer constrained. Partitioning at these higher temperatures can lead to unique microstructures such as the nano-composite illustrated here for a metastable Zr(1−x)Al x O2−x/2 (x≤0.57) phase that partitions into a composite containing t-ZrO2 grains and α-Al2O3 plates.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00486263
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  • 8
    Electronic Resource
    Electronic Resource
    Compressive creep of Si3N4/MgO alloys (1980)
    Springer
    Journal of materials science 15 (1980), S. 601-610 
    Details
    ISSN: 1573-4803
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The compressive creep behaviour of four compositions within the Si3N4-Mg2SiO4-Si2N2O compatibility triangle were studied in air at 1400° C. Strain rate ( $$\dot \varepsilon $$ ) versus stress (σ) was analysed to determine the stress exponent, n ( $$\dot \varepsilon = A\sigma ^n $$ ). Cavitation during creep was determined by precise (sink-float) density measurements. Compositions close to the Si3N4-Si2N2O tie line exhibited no cavitation and had n≃1, whereas compositions close to the Si3N4-Mg2SiO2 tie line exhibited extensive cavitation and had n≃2. Test results are interpreted in terms of the volume fraction of the viscous phase present.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00551722
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  • 9
    Electronic Resource
    Electronic Resource
    Compressive creep of Si3N4/MgO alloys (1980)
    Springer
    Journal of materials science 15 (1980), S. 616-618 
    Details
    ISSN: 1573-4803
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract A comparison of “creep” resistance in as-fabricated and pre-oxidized specimens of different Si3N4/MgO alloys shows that pre-oxidation not only significantly reduces the apparent steady-state creep rate, but can also change the stress dependence from a non-linear to a linear behaviour. This phenomenon is discussed in terms of compositional changes induced by oxidation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00551724
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  • 10
    Electronic Resource
    Electronic Resource
    Compressive creep of Si3N4/MgO alloys (1980)
    Springer
    Journal of materials science 15 (1980), S. 611-615 
    Details
    ISSN: 1573-4803
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Highly localized strain fields are observed at grain boundaries in crept specimens of Si3N4/MgO alloys which were frozen under stress. These fields disappear upon annealing. Unresolved asperities between the grain pairs appear to give rise to the strain field during deformation. Viscoelastic effects responsible for primary creep and strain recovery are explained in terms of grain-boundary sliding on the glassy interphase which is accommodated by the elastic strain arising at the asperities. Each boundary containing an asperity can be modelled as a simple Kelvin element. The spectrum of these boundaries within the bulk gives rise to a spectrum of relaxation times that is observed for the strain recovery effect. The highly stressed region at the asperity also gives rise to the higher chemical potential required to drive diffusional creep. Although the source of the asperities was not observed, the possibility of opposing ledges of either single or multiple interplanar height is discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00551723
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