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  • 2005-2009  (59)
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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
    Long Crack R-Curve of Aligned Porous Silicon Nitride (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: Long crack R-curve of a porous Si3N4 with aligned fibrous grains was investigated, using a chevron-notched beam technique. A crack was constrained to propagate normal to the grain alignment. The crack growth resistance of aligned porous Si3N4 was much larger compared with that of dense Si3N4 ceramics. Microstructure observations showed that pullouts of fibrous grains in aligned porous Si3N4 markedly increased during crack propagation relative to those of dense Si3N4, due to the existence of pores. The efficient grain pullouts in porous Si3N4 increased the bridging stress at the crack wake.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1551-2916.2005.00067.x
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  • 3
    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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  • 4
    Electronic Resource
    Electronic Resource
    Oxidation of Silicon Nitride in Wet Air and Effect of Lutetium Disilicate Coating (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: Oxidation behavior of silicon nitride (Si3N4) was investigated in flowing air (2.45 cm/s) containing 10%–50% H2O at a total pressure of 1.8–10 atm at 1300°–1500°C for 100 h. The oxidation of Si3N4 progressed with volatilization of the SiO2 scale; it was more enhanced at a high partial pressure of H2O rather than at high temperature. The total pressure had little effect on the oxidation. In order to avoid the oxidation, Si3N4 substrate was coated with lutetium disilicate (Lu2Si2O7) layer through the intermediate SiO2-rich phase. While the coating layer well suppressed the oxidation in case of small amount of water vapor, it was not sufficiently effective to suppress the oxidation when the water vapor was rich. SiO2 volatilization was observed between the layer and substrate. The flexural strength of the coated Si3N4 at room temperature was somewhat increased after the oxidation in wet air, while that of the uncoated one was almost unchanged. This increase was attributable to crack healing of the substrate during the oxidation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1551-2916.2005.00230.x
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  • 5
    Electronic Resource
    Electronic Resource
    Porous Silicon Nitride Ceramics Prepared by Reduction–Nitridation of Silica (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 new method for preparing porous silicon nitride ceramics with high porosity had been developed by carbothermal reduction of die-pressed green bodies composed of silicon dioxide, carbon, sintering additives, and seeds. The resultant porous silicon nitride ceramics showed fine microstructure and uniform pore structure. The influence of SiO2 particle size and sintering process (sintering temperature and retaining time) on the microstructure of sintering bodies was analyzed. X-ray diffractometry demonstrated the formation of single-phase β-Si3N4 via the reaction between silicon dioxide and carbon at high temperature. SEM analysis showed that pores were formed by the banding up of rod-like β-Si3N4 grains. Porous Si3N4 ceramics with a porosity of 70–75%, and a strength of 5–8 MPa, were obtained.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1551-2916.2005.00444.x
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  • 6
    Electronic Resource
    Electronic Resource
    Reactive Hot-Pressed Alumina–Boron Nitride Composites with Y2O3 Sintering Additive (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 effect of Y2O3 addition (0–5 wt%) on the densification and properties of reactive hot-pressed alumina (Al2O3)–boron nitride composites based on the reaction between aluminum borate (2Al2O3·B2O3) and aluminum nitride (AlN) was investigated. The densification process was very sensitive to the amount of Y2O3. Compared with a low relative density of 79.3 theoretical density (TD)% for material with no Y2O3 addition, the material density reached 98.6 TD% with 0.25% Y2O3 addition. High Y2O3 additions resulted in the formation of a new phase Al5Y3O12. The grain growth of the Al2O3 matrix was promoted by the Y2O3 addition. Owing to the high density and the small Al2O3 particle size the sample with 0.25% Y2O3 addition demonstrated the highest bending strength of 540 MPa.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1551-2916.2005.00437.x
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  • 7
    Electronic Resource
    Electronic Resource
    Synthesis of Porous Si3N4 Ceramics with Rod-Shaped Pore Structure (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: Porous Si3N4 ceramics were synthesized by pressureless sintering of green compacts prepared using slip casting of slurries containing Si3N4, 5 wt% Y2O3+2 wt% Al2O3, and 0–60% organic whiskers composed of phenol–formaldehyde resin with solids loading up to 60 wt%. Rheological properties of slurries were optimized to achieve a high degree of dispersion with a high solid-volume fraction. Samples were heated at 800°C in air and sintered at 1850°C in a N2 atmosphere. Porosities ranging from 0% to 45% were obtained by the whisker contents (corresponding to 0–60 vol% whisker). Samples exhibited a uniform pore distribution. Their rod-shaped pore morphology originated from burnout of whiskers, and an extremely dense Si3N4 matrix.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1551-2916.2005.00199.x
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  • 8
    Electronic Resource
    Electronic Resource
    Fabrication and Properties of the Tape-Cast Si〈sub〉3〈/sub〉N〈sub〉4〈/sub〉 with Rod-Like Si〈sub〉3〈/sub〉N〈sub〉4〈/sub〉 Seed Addition (2007)
    s.l. ; Stafa-Zurich, Switzerland
    Key engineering materials Vol. 280-283 (Feb. 2007), p. 1219-1222 
    Details
    ISSN: 1013-9826
    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: Silicon nitride ceramics with and without β-Si3N4 seed addition were prepared via tape casting nonaqueous ceramic slurries, laminating the green ceramic tapes, and gas pressure sintering the green bodies in nitrogen atmosphere. Lu2O3 and SiO2 were used as sintering additives. The results showed that the rod-like β-Si3N4 seed was helpful to enhance β-Si3N4 grain growth unidirectionally. The elongated grains grown from seeds were preferentially oriented parallel to the casting direction,resulting in anisotropic microstructure. When a stress was applied with along the grain alignment, the bending strength of the tape-cast Si3N4 with 3 wt% β-Si3N4 seed addition measured at 1500oC was 738 MPa, which was almost the same as the room temperature bending strength 739 MPa, and the fracture energy can be improved from 301 J/m2 at room temperature to 781 J/m2 at 1500oC. The largefracture energy and bending strength at 1500oC were attributable primarily to the unidirectional alignment fibrous grains and a high melting point grain boundary phase
    Type of Medium: Electronic Resource
    URL: http://www.tib-hannover.de/fulltexts/2011/0528/01/49/transtech_doi~10.4028%252Fwww.scientific.net%252FKEM.280-283.1219.pdf
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  • 9
    Electronic Resource
    Electronic Resource
    Reaction Synthesized Boron Nitride-Containing Composites (BNCC) (2007)
    s.l. ; Stafa-Zurich, Switzerland
    Key engineering materials Vol. 280-283 (Feb. 2007), p. 1385-1390 
    Details
    ISSN: 1013-9826
    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: Based on the proposed inorganic reactions a series of high performance hexagonal boron nitride-containing composites (BNCC), include SiC-BN, Si3N4-SiC-BN, SiAlON-BN, AlN-BN, Al2O3-BN, AlON-BN and mullite-BN, have been prepared via reactive hot pressing or pressureless reactive sintering. Various boron-bearing components such as B, B4C, AlB2, SiB4, SiB6, B2O3 or H3BO3, 9Al2O3×2B2O3 (9A2B) and 2Al2O3×B2O3 (2AB) are used as the boron source. On the other hand, nitrogen gas or solid state nitirgen-bearing metal nitrides such as Si3N4 and AlN can be used as the nitrogen source. The in situ synthesized composites demonstrated homogeneous and isotropical microstructures with very fine (nano-sized) BN platelets or their agglomerates distributed in the matrixes. These composites showed high strength, low elasticity and improved strain tolerance. In this article the reaction design, thermodynamics, reaction mechanisms, reactive hot pressing or pressureless reactive sintering, microstructures and mechanical properties will be discussed
    Type of Medium: Electronic Resource
    URL: http://www.tib-hannover.de/fulltexts/2011/0528/01/49/transtech_doi~10.4028%252Fwww.scientific.net%252FKEM.280-283.1385.pdf
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  • 10
    Electronic Resource
    Electronic Resource
    Measurement of Indentation Fracture Toughness of Silicon Nitride Ceramics: I, Effect of Microstructure of Materials (2007)
    s.l. ; Stafa-Zurich, Switzerland
    Key engineering materials Vol. 352 (Aug. 2007), p. 41-44 
    Details
    ISSN: 1013-9826
    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: Effect of microstructure of silicon nitride on the fracture toughness, KIc evaluated by the IFmethod was studied with various indentation loads ranging from 49 N to 490 N, since practicalassessment of fracture toughness of small Si3N4 parts is needed in the ceramic ball bearing market.The plot of KIc against the as-indented crack length revealed the rising R-curve behavior for the coarseSi3N4 and slight R-curve for the fine Si3N4. By comparing KIc estimated from the SEPB and IFmethods using 4 different equations, it was revealed that the IF equation which gave the nearest valueto KIc from SEPB was different depending on the microstructures. These results were discussed inconjunction with their R-curve behavior and the effective crack length in the SEPB specimens
    Type of Medium: Electronic Resource
    URL: http://www.tib-hannover.de/fulltexts/2011/0528/01/55/transtech_doi~10.4028%252Fwww.scientific.net%252FKEM.352.41.pdf
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