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  • 1
    Electronic Resource
    Electronic Resource
    Comparison of Mechanical Properties of Silicon Nitrides with Controlled Porosities Produced by Different Fabrication Routes (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: Three different series of porous silicon nitride ceramics with volume fraction porosities in the range 0–0.5 were fabricated using different preparation routes: (i) partial sintering, (ii) the addition of fugitive inclusions, and (iii) partial hot pressing. The use of different sintering additives and firing conditions, depending on the preparation route, gives rise to different materials within a certain porosity range with variations in terms of microstructure and grain boundary phase. Mechanical properties, elastic moduli, and strength have been evaluated separately for each series of materials. Porosity dependences of Young's modulus, shear modulus, Poisson's ratio, and fracture strength have been assessed and a comparison of the different materials is made and discussed in relation to their microstructural features.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1551-2916.2005.00132.x
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  • 2
    Electronic Resource
    Electronic Resource
    Thermal Shock Behavior of Isotropic and Anisotropic Porous Silicon Nitride (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 thermal shock behavior of isotropic and anisotropic porous Si3N4 was evaluated using the water-quenching technique. The critical temperature difference for crack initiation was found to be strongly dependent on the ratio of fracture strength to elastic modulus. Because of a very high strain-to-failure, anisotropic porous Si3N4 showed no macroscopic cracks and was able to retain its strength even at a quenching-temperature difference of ∼1400°C.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1151-2916.2003.tb03367.x
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  • 3
    Electronic Resource
    Electronic Resource
    Synthesis and Properties of Porous Single-Phase β′-SiAlON Ceramics (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: Single-phase β′-SiAlON (Si6−zAlzOzN8−z, z= 0–4.2) ceramics with porous structure have been prepared by pressureless sintering of powder mixtures of á-Si3N4, AlN, and Al2O3 of the SiAlON compositions. A solution of AlN and Al2O3 into Si3N4 resulted in the β′-SiAlON, and full densification was prohibited because no other sintering additives were used. Relative densities ranging from 50%–90% were adjusted with the z-value and sintering temperature. The results of X-ray diffraction, scanning electron microscopy, and transmission electron microscopy analyses indicated that single-phase β′-SiAlON free from a grain boundary glassy phase could be obtained. Both grain and pore sizes increased with increasing z-value. Low z-value resulted in a relatively high flexural strength.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1151-2916.2002.tb00370.x
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  • 4
    Electronic Resource
    Electronic Resource
    Microstructure and Mechanical Properties of Silicon Nitride Ceramics with Controlled Porosity (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: Porous silicon nitride ceramic with a porosity from 0–0.3 was fabricated by partial hot-pressing of a powder mixture of α-Si3N4 and 5 wt% Yb2O3 as sintering additive. Irrespective of the porosity, the samples exhibited almost the same microstructural features including grain size, grain aspect ratio, and pore size. Porosity dependences of Young's modulus, flexural strength, and fracture toughness (KIC) were investigated. All these properties decreased with increasing porosity. However, because of the fibrous microstructure, the decreases of flexural strength and fracture toughness were moderate compared with the much greater decrease of Young's modulus. Thus, the strain tolerance (fracture strength/Young's modulus) increased with increasing porosity. The critical energy release rate also increased slightly with an increasing volume fraction of porosity to 0.166 and remained at the same level with that of the dense sample when the porosity was 0.233. They decreased as porosity increased further.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1151-2916.2002.tb00305.x
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  • 5
    Electronic Resource
    Electronic Resource
    Microstructure and Mechanical Properties of Sinter–Post-HIPed Si3N4–SiC Composites (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 microstructural evolution and mechanical properties of Si3N4–SiC composites obtained by the sinter–post-HIP process were investigated. SiC addition prohibited β-Si3N4 grain growth; however, the grain growth followed the empirical growth law, with exponents of 3 and 5 for the c- and the a-axis directions, respectively. Mechanical properties were strongly influenced by SiC addition and sintering conditions. Short-crack propagation behavior was measured and analyzed by the indentation-strength in-bending (ISB) method. The present composites had high short-crack toughness, compared with the values for monolithic Si3N4. The enhanced short-crack toughness was attributed to crack-tip bridging by the SiC particles.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1151-2916.2001.tb00669.x
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  • 6
    Electronic Resource
    Electronic Resource
    Reactive Hot Pressing of ZrB2–SiC 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: A ZrB2–SiC composite was prepared from a mixture of zirconium, silicon, and B4C via reactive hot pressing. The three-point bending strength was 506 ± 43 MPa, and the fracture toughness was 4.0 MPa·m1/2. The microstructure of the composite was observed via scanning electron microscopy; the in-situ-formed ZrB2 and SiC were found in agglomerates with a size that was in the particle-size ranges of the zirconium and silicon starting powders, respectively. A model of the microstructure formation mechanism of the composite was proposed, to explain the features of the phase distributions. It is considered that, in the reactive hot-pressing process, the B and C atoms in B4C will diffuse into the Zr and Si sites and form ZrB2 and SiC in situ, respectively. Because the diffusion of Zr and Si atoms is slow, the microstructure (phase distributions) of the obtained composite shows the features of the zirconium and silicon starting powders.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1151-2916.2000.tb01558.x
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  • 7
    Electronic Resource
    Electronic Resource
    Fracture Energies of Tape-Cast Silicon Nitride with β-Si3N4 Seed Addition (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: The fracture energies of the tape-cast silicon nitride with and without 3 wt% rod-like β-Si3N4 seed addition were investigated by a chevron-notched-beam technique. The material was doped with Lu2O3–SiO2 as sintering additives for giving rigid grain boundaries and good heat resistance. The seeded and tape-cast silicon nitride has anisotropic microstructure, where the fibrous grains grown from seeds were preferentially aligned parallel to the casting direction. When a stress was applied parallel to the fibrous grain alignment direction, the strength measured at 1500°C was 738 MPa, which was almost the same as room temperature strength 739 MPa. The fracture energy of the tape-cast Si3N4 without seed addition was 109 and 454 J/m2 at room temperature and 1500°C, respectively. On the contrary, the fracture energy of the seeded and tape-cast Si3N4 was 301 and 781 J/m2 at room temperature and 1500°C, respectively, when a stress was applied parallel to the fibrous gain alignment. The large fracture energies were attributable primarily to the unidirectional alignment fibrous Si3N4 grains.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1551-2916.2005.00242.x
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  • 8
    Electronic Resource
    Electronic Resource
    Strength of Silicon Nitride after Thermal Shock (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: A water-quenching technique was used to evaluate the thermal-shock strength behavior of silicon nitride (Si3N4) ceramics in an air atmosphere. When the tensile surface was shielded from air during the heating and soaking process, the quenched specimens showed a gradual decrease in strength at temperatures above 600°C. However, the specimens with the air-exposed surface exhibited a ∼16% and ∼29% increase in strength after quenching from 800° and 1000°C, respectively. This is because of the occurrence of surface oxidation, which may cause the healing of surface cracks and the generation of surface compressive stresses. As a result, some preoxidation of Si3N4 components before exposure to a thermal-shock environment is recommended in practical applications.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1151-2916.2003.tb03527.x
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  • 9
    Electronic Resource
    Electronic Resource
    Improvement of Mechanical Properties and Corrosion Resistance of Porous β-SiAlON Ceramics by Low Y2O3 Additions (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: Addition of Y2O3 as a sintering additive to porous β-SiAlON (Si6−zAlzOzN8−z, z= 0.5) ceramics has been investigated for improved mechanical properties. Porous SiAlON ceramics with 0.05–0.15 wt% (500–1500 wppm) Y2O3 were fabricated by pressureless sintering at temperatures of 1700°, 1800°, and 1850°C. The densification, microstructure, and mechanical properties were compared with those of Y2O3-free ceramics of the same chemical composition. Although this level of Y2O3 addition did not change the phase formation and grain size, the grain bonding appeared to be promoted, and the densification to be enhanced. There was a significant increase in the flexural strength of the SiAlON ceramics relative to the Y2O3-free counterpart. After exposure in 1M hydrochloric acid solution at 70°C for 120 h, no remarkable weight loss and degradation of the mechanical properties (flexural and compression strength) was observed, which was attributed to the limited grain boundary phase, and with the minor Y2O3 addition the supposed formation of Y-α-SiAlON.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1551-2916.2004.01714.x
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  • 10
    Electronic Resource
    Electronic Resource
    Porous 2H-Silicon Carbide Ceramics Fabricated by Carbothermal Reaction between Silicon Nitride and Carbon (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: Porous SiC ceramics were synthesized by sintering pressed and pressed/CIPed powder compacts of α-Si3N4, carbon (Si3N4:C = 1:3 mol as ratio), and sintering aids, at 1600°C for few hours to achieve a reaction, and subsequently sintering at a temperature range of 1750°–1900°C, in an argon atmosphere. High porosities from 45%–65% were achieved by low shrinkage with large weight loss. Formation of pure 2H-SiC phase via a reaction between Si3N4 and carbon can be demonstrated by X-ray diffractometry. The resultant porous SiC samples were characterized by SiC grain microstructures, pore-size distribution, and flexural strength. This method has the advantage of fabricating high-porous SiC ceramics with fine microstructure and good properties at a relatively low temperature.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1151-2916.2003.tb03396.x
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