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  • 1
    Electronic Resource
    Electronic Resource
    The structure of special grain boundaries in α-Al"2O"3
    Amsterdam : Elsevier
    Journal of Physics and Chemistry of Solids 55 (1994), S. 1067-1082 
    Details
    ISSN: 0022-3697
    Keywords: A. ceramics ; A. interfaces ; C. electron microscopy ; D. crystal structure
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
    URL: http://linkinghub.elsevier.com/retrieve/pii/0022-3697(94)90125-2
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  • 2
    Electronic Resource
    Electronic Resource
    Chemistry of grain boundaries in calcia doped silicon nitride studied by spatially resolved electron energy-loss spectroscopy
    Amsterdam : Elsevier
    Analytica Chimica Acta 297 (1994), S. 97-108 
    Details
    ISSN: 0003-2670
    Keywords: Calcia ; Ceramics ; Electron energy-loss spectroscopy ; Grain boundaries ; Silicon nitride
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://linkinghub.elsevier.com/retrieve/pii/0003-2670(94)00058-1
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  • 3
    Electronic Resource
    Electronic Resource
    Characterization of Nanodomains in Polymer-Derived SiCN Ceramics Employing Multiple Techniques (2005)
    Oxford, UK : Blackwell Science Inc
    Journal of the American Ceramic Society 88 (2005), 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 combination of methods, Bragg diffraction, small-angle X-ray scattering (SAXS), and transmission electron microscopy, is applied to the characterization of nanodomains and nanocrystals in polymer-derived ceramics (PDCs). Detailed study of two materials, silicon carbonitride (SiCN) and a SiCN–zirconia nanocomposite, is presented. The first contains domains which can be measured only by SAXS. However, the nanocrystallites of zirconia in the second material can be quantatively studied by all three techniques. In both instances, we find the SAXS to be particularly useful because these data provide detailed information regarding the size distribution of the domains and the crystallites. This information can be valuable in understanding the materials science of PDCs: e,g., the change in the distribution and the average size of the nanoclusters can be modeled to understand the kinetic mechanisms of coarsening at high temperatures.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1551-2916.2004.00034.x
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  • 4
    Electronic Resource
    Electronic Resource
    High resolution electron microscopy study of amorphous calcium phosphate
    Amsterdam : Elsevier
    Journal of Crystal Growth 129 (1993), S. 149-162 
    Details
    ISSN: 0022-0248
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Type of Medium: Electronic Resource
    URL: http://linkinghub.elsevier.com/retrieve/pii/0022-0248(93)90444-2
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  • 5
    Electronic Resource
    Electronic Resource
    Extended X-ray absorption fine structure (EXAFS) study of secondary phases in Yb2O3-doped Si3N4 ceramics (1997)
    Springer
    Journal of materials science 32 (1997), S. 369-374 
    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 Liquid-phase sintered Si3N4 doped with Yb2O3 as a sintering aid was characterized by both transmission electron microscopy and extended X-ray absorption fine structure (EXAFS) measurements. Structural information about the secondary phases was obtained with an emphasis being placed on the evaluation of EXAFS data. Two Si3N4 samples were processed which contained either 5 vol% or 10 vol% Yb2O3 as sintering additive. After sintering, only an amorphous secondary phase was observed in the material doped with 5 vol% Yb2O3. The material with the higher Yb2O3 volume fraction underwent a further heat treatment after the densification, in order to crystallize pockets of the secondary phase. This heat treatment resulted in the formation of Yb2Si2O7 at multi-grain junctions, with however, amorphous phases remaining along the grain and phase boundaries. The EXAFS data obtained from the two doped Si3N4 materials were compared with reference spectra obtained on pure Yb2O3 and synthetic Yb2Si2O7. No residual Yb2O3 was determined in the doped Si3N4 materials, independent of the Yb2O3 volume fraction. Compared to synthetic Yb2Si2O7, the secondary phase formed in the 10 vol% Yb2O3 containing material showed only subtle changes in the EXAFS data. A clear distinction between purely amorphous and a combination of crystalline plus amorphous Yb secondary phases was possible, when both doped Si3N4 materials were compared. However, no distinction between the glass phase present at triple junctions and the amorphous residue along grain/phase boundaries was feasible, since a full numerical data evaluation could not be performed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1018501316195
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  • 6
    Electronic Resource
    Electronic Resource
    Densification studies of SRBSN with unstabilized zirconia by means of dilatometry and electron microscopy (1994)
    Springer
    Journal of materials science 29 (1994), S. 1265-1275 
    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 correlation of densification behaviour and microstructural development of ZrO2-fluxed sintered reaction-bonded Si3N4 (SRBSN) is reported in the light of dilatometry and both high-resolution electron microscopy (HREM) and analytical electron microscopy (AEM). Two distinct dilatometer maxima were observed using a modified dilatometer with improved sensitivity. The relatively small first dilatometer maximum, at approximately 1750
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00975074
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  • 7
    Electronic Resource
    Electronic Resource
    Yb2O3-fluxed sintered silicon nitride (1993)
    Springer
    Journal of materials science 28 (1993), S. 3529-3538 
    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 Microstructural development and crystallization behaviour of Yb2O3-fluxed sintered silicon nitride materials was investigated using CTEM and HREM. The materials contained 5 and 10 vol% Yb2O3 as sintering additives. After densification, both compositions were subsequently heat treated to crystallize the residual amorphous secondary phases present at triple-grain regions. In the material doped with 5 vol% Yb2O3, only an amorphous secondary phase was observed after sintering, which was about 80% crystalline (Yb2Si2O7) after the post-sintering heat treatment. A metastable phase was formed in the material with 10 vol% additives after sintering, with about 70% crystallinity in the triple-point pockets. Upon postsintering heat treatment, the material could be completely crystallized. During heat treating, the metastable phase combined with the remaining glass to form Yb2SiO5 plus Yb2Si2O7 and a small amount of Si3N4 which deposited epitaxially on pre-existing Si3N4 grains in areas of low-energy within the triple-point pockets. All materials contained thin amorphous films separating the grains. The amorphous intergranular films along grain boundaries (homophase boundaries) revealed excess ytterbium and oxygen. The thickness of the intergranular films was about 1.0 and 2.5 nm for the grain boundaries and the phase boundaries, respectively, independent of additive content and heat-treatment history.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01159834
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  • 8
    Electronic Resource
    Electronic Resource
    Effects of oxidation on intergranular phases in silicon nitride ceramics (1993)
    Springer
    Journal of materials science 28 (1993), S. 5775-5782 
    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 effects of oxidation on changes in the secondary phases of two Si3N4 ceramics were investigated by transmission electron microscopy. The Si3N4 materials were oxidized at 1400 °C for 168 h in laboratory air. One material, sintered with 5 vol% Yb2O3+0.5 vol% Al2O3, containing a Yb2Si2O7 crystalline secondary phase, displayed no gross changes following oxidation. However, the thickness of the amorphous intergranular film was observed to have decreased by ∼ 20% from its initial thickness of 1.0 nm. The second Si3N4 material, sintered with 5 wt% Y2O3+1 wt% MgO, had a completely amorphous secondary phase. Devitrification of the secondary phase at multiple-grain junctions to β-Y2Si2O7 accompanied the outward diffusion of additive and impurity cations occurring in the residual amorphous intergranulàr films during oxidation. Substantial cavitation and intergranular phase depletion was observed at both multiple-grain junctions and two-grain boundaries. The equilibrium thickness of the amorphous intergranular film consequently decreased from 1.2 to 0.9 nm following oxidation. Purification of the amorphous intergranular films by diffusion of cations to the surface led to a reduction in impurity concentration, resulting in the observed thinning of grain-boundary films.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00365181
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  • 9
    Electronic Resource
    Electronic Resource
    Effect of interface chemistry on the mechanical properties of Si3N4-matrix composites (1999)
    Springer
    Journal of materials science 34 (1999), S. 1667-1680 
    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 systematic modifications in the chemistry of the phase-boundary film on the macroscopic mechanical properties of Si3N4-matrix composites was investigated. Model composite materials, containing SiC or WC platelets, were prepared and only the bulk anion composition of the glassy-SiO2 intergranular phase was varied by adding increasing amounts of fluorine to the material. Detailed material characterizations by high-resolution electron microscopy (HREM) and Raman spectroscopy on both undoped and F-doped composites allowed to derive a structural model of the phase-boundary film as well as to evaluate the average microscopic stresses acting on it. In addition, high-temperature internal friction measurements provided an estimate of the grain-boundary relaxation temperature as a function of the F content. Noticeable variations of both elastic modulus and fracture energy of the composite were detected upon F addition, which were related to a spontaneous process of phase-boundary microcracking upon cooling. A threshold of the F-content was found for microcrack formation and its existence is theoretically explained according to a percolation process of non-bridged SiO4-tetrahedra, which arises from the incorporation of F into the intergranular film network.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1004597120686
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  • 10
    Electronic Resource
    Electronic Resource
    Epitaxial deposition of silicon nitride during post-sintering heat treatment (1992)
    Springer
    Journal of materials science 11 (1992), S. 1249-1252 
    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/BF00729782
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