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  • 1
    Electronic Resource
    Electronic Resource
    Photoluminescence of Cerium-Doped α-SiAlON Materials (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: Cerium-doped α-SiAlON (MxSi12−(m+n)Alm+nOnN16–n) materials have been prepared by gas-pressure sintering and post-hot-isostatic-press (HIP) annealing, using four powder mixtures of α-Si3N4, AlN, and either (i) CeO2, (ii) CeO2+ Y-α-SiAlON seed, (iii) CeO2+ Y2O3, or (iv) CeO2+ CaO. Cerium-containing CeAl(Si6–zAlz)(N10–zOz) (JEM) phase, rather than Ce-α-SiAlON phase, forms in the sample with only CeO2, whereas a single-phase α-SiAlON generates in samples with dual doping (CeO2+ Y2O3 and CeO2+ CaO). On ultraviolet-light excitation, JEM gives one broad emission band with maximum at 465 nm and a shoulder at 498 nm; α-SiAlON shows an intense and broad emission band that peaks at 500 nm. The unusual long-wavelength emissions in JEM and α-SiAlON are due to increases in the nephelauxetic effect and the ligand-field splitting of the 5d band, because the coordination of Ce3+ in JEM and α-SiAlON is nitrogen enriched.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1151-2916.2004.tb07738.x
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  • 2
    Electronic Resource
    Electronic Resource
    Crystal Structure of Lu4Si2O7N2 Analyzed by the Rietveld Method Using the Time-of-Flight Neutron Powder Diffraction Pattern (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: The crystal structure of a lutetium silicon oxynitride (Lu4Si2O7N2) was analyzed by the Rietveld method using time-of-flight (TOF) neutron powder diffraction data. The compound crystallizes in a monoclinic cell, space group P21/c (No. 14-1) with a= 7.4243(1), b= 10.2728(1), c= 10.6628(1) Å, and β= 109.773(1)° at 297 K. One nitrogen atom in Lu4Si2O7N2 occupies the bridging site between the two Si atoms, and the other one is statistically situated at the terminal sites of Si2O5N2 ditetrahedra. In the local structure, Si2O5N2 ditetrahedra consist of SiO3N and SiO2N2 tetrahedral units sharing the N atom. Lu atoms are in sixfold, sevenfold (×2) and eightfold coordinations of O/N atoms. X-ray powder diffraction data were also analyzed with the model obtained by the neutron diffraction.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1151-2916.2002.tb00406.x
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  • 3
    Electronic Resource
    Electronic Resource
    Strength Retention in Hot-Pressed Si3N4 Ceramics with Lu2O3 Additives after Oxidation Exposure in Air at 1500°C (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: The effect of oxidation exposure on room-temperature flexural strength was examined in 3.33- and 12.51-wt%-Lu2O3-containing hot-pressed Si3N4 ceramics exposed to air at 1500°C for up to 1000 h. After oxidation exposure, the room-temperature strength of the ceramics was degraded, and strength retention decreased with time at temperature, dependent on the amount of additive. The retention in room-temperature strength displayed by the two compositions after 1000 h of oxidation exposure was 75%–80%. The degradation in strength was attributed to the formation of new defects at and/or near the interface between the oxide layer and the Si3N4 bulk during oxidation exposure.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1151-2916.2002.tb00319.x
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  • 4
    Electronic Resource
    Electronic Resource
    Effect of Dynamic Microstructural Change on Deformation Behavior in Liquid-Phase-Sintered Silicon Carbide with Al2O3–Y2O3–CaO Additions (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: Nanocrystalline β-SiC with additions of 7 wt% Al2O3, 2 wt% Y2O3, and 1 wt% CaO was subjected to tensile deformation to study its microstructural behavior under the dynamic process. The liquid-phase-sintered body had a relative density of 〉97% and an average grain size of 170 nm. Tension tests were conducted at initial strain rates ranging from 2 × 10−5 to 5 × 10−4 s−1, in the temperature range 1973–2023 K, in both argon and N2 atmospheres. Although grain-boundary liquids formed by the additions vaporized concurrently with the decomposition of SiC and extensive grain growth, the maximum tensile elongation of 48% was achieved in argon. Annealing experiments under the same conditions revealed that vaporization and grain growth were both dependent on experimental time. Therefore, high strain rates suffered less from the hardening effect when cavitation damage was more severe. Testing in an N2 atmosphere brought about crystallization of the grain-boundary phase and prevented severe vaporization; however, fracture occurred at only 8% elongation. Grain-boundary sliding was still the dominant mechanism for deformation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1151-2916.2001.tb00956.x
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  • 5
    Electronic Resource
    Electronic Resource
    Heat-Resistant Silicon Carbide with Aluminum Nitride and Erbium Oxide (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: Fully dense SiC ceramics with high strength at high temperature were obtained by hot-pressing and subsequent annealing under pressure, with AlN and Er2O3 as sintering additives. The ceramics had a self-reinforced microstructure consisting of elongated SiC grains and a grain-boundary glassy phase. The strength of these ceramics was ∼550 MPa at 1600°C, and the fracture toughness was ∼6 MPa·m1/2 at room temperature. The beneficial effect of the new additive composition on high-temperature strength might be attributable to the introduction of aluminum from the liquid composition into the SiC lattice, resulting in a refractive grain-boundary glassy phase.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1151-2916.2001.tb00958.x
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  • 6
    Electronic Resource
    Electronic Resource
    Relationship between Microstructure and Fracture Toughness of Toughened Silicon Carbide Ceramics (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: Different microstructures in SiC ceramics containing Al2O3, Y2O3, and CaO as sintering additives were prepared by hot-pressing and subsequent annealing. The microstructures obtained were analyzed by image analysis. Crack deflection was frequently observed as the toughening mechanism in samples having elongated α-SiC grains with aspect ratio 〉4, length 〉2 μm, and grain thickness (t) 〈3 μm (defined as key grains 1). Crack bridging was the dominant toughening mechanism observed in samples having grains with thickness of 1 μm 〈 t 〈 3 μm and length 〉2 μm (key grains 2). The values of fracture toughness varied from 5.4 to 8.7 MPa·m1/2 with respect to microstructural characteristics, characterized by mean grain thickness, mean aspect ratio, and total volume fraction of key grains. The difference in fracture toughness was mainly attributed to the amount of key grains participating in the toughening processes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1151-2916.2001.tb00840.x
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  • 7
    Electronic Resource
    Electronic Resource
    Synthesis of Cerium α-SiAlON with Nuclei Addition (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: Cerium α-SiAlON ceramics were made from a powder mixture of Si3N4-AlN-CeO2 that contained 1 wt% yttrium α-SiAlON powder. Plasma-activated sintering was used to examine the effect of the cooling rate on the formation of α-SiAlON. The formation of cerium α-SiAlON was suggested to be controlled by the nucleation at the surface of α-SiAlON nuclei, because α-phase formation could not occur without the addition of SiAlON powder. The solubility of cerium in the α-SiAlON was shown to be less than a previously predicted critical value.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1151-2916.2001.tb00847.x
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  • 8
    Electronic Resource
    Electronic Resource
    Effect of Atmosphere on Weight Loss in Sintered Silicon Carbide during Heat Treatment (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: Heat treatment was performed on β-SiC with different sintering additives in the temperature range 1873–2073 K, in both argon and nitrogen-gas atmospheres. In the case of the specimens heat-treated at 2073 K in argon, the weight loss was more than the total weight of the sintering additives, except for B,C-doped β-SiC. On the other hand, weight loss was suppressed by about one-third to one-half in nitrogen gas. Weight loss depended mainly on the reaction at the interface between the SiC grains and the grain-boundary phase.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1151-2916.2000.tb01631.x
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  • 9
    Electronic Resource
    Electronic Resource
    Microstructure and Mechanical Properties of alpha-Silicon Carbide Sintered with Yttrium-Aluminum Garnet and Silica (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 effect of glassy-phase chemistry, using Y3Al5O12 (YAG) and SiO2 as sintering additives, on the microstructure and mechanical properties of liquid-phase-sintered, and subsequently annealed, α-SiC materials was investigated. The microstructural development of annealed materials was insensitive to changes in glass chemistry. The mechanical properties vs SiO2/YAG ratio curve had a maximum; i.e., there was a small glass composition range at which optimum mechanical properties were realized. The best results were obtained when the ratio was ∼0.5. The flexural strength and fracture toughness of the material were 〉450 MPa and 〉6 MPa·m1/2, respectively.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1551-2916.1999.tb20082.x
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  • 10
    Electronic Resource
    Electronic Resource
    Hot-Pressed Silicon Nitride with Lu2O3 Additives: Oxidation and Its Effect on Strength (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 oxidation behavior and effect of oxidation on room-temperature flexural strength were investigated for hot-pressed Si3N4 ceramics, with 3.33 and 12.51 wt% Lu2O3 additives, exposed to air at 1400° and 1500°C for up to 200 h. Parabolic oxidation behavior was observed for both compositions. The oxidation products consisted of Lu2Si2O7 and SiO2. The Lu2Si2O7 grew out of the surface silicate in preferred orientations. The morphology of oxidized surfaces was dependent on the amount of additive; Lu2Si2O7 grains in the 3.33 wt% composition appeared partially in a needlelike type, compared with a more equiaxed type exhibited in the 12.51 wt% case. The high resistance to oxidation shown for both compositions was attributed to the extensive amounts of crystalline, refractory secondary phases formed during the sintering process. Moreover, after 200 h of oxidation at 1400° and 1500°C, the strength retention displayed by the two compositions was 93%–95% and 85%–87%, respectively. The strength decrease was associated with the formation of new defects at the interface between the oxide layer and the Si3N4 bulk.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1151-2916.2003.tb03579.x
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