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  • 1
    Electronic Resource
    Electronic Resource
    Electrically Conductive CNT-Dispersed Silicon Nitride Ceramics (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: Carbon nanotube (CNT)-dispersed Si3N4 ceramics with electrical conductivity were developed based on the lower temperature densification technique, in which the key point is the addition of both TiO2 and AlN as well as Y2O3 and Al2O3 as sintering aids. This new ceramic with a small amount of CNTs exhibits very high electrical conductivity in addition to high strength and toughness. Since Si3N4 ceramics with Y2O3–Al2O3–TiO2–AlN were originally used as a wear material, electrically conductive Si3N4 ceramics are expected to be applied for high-performance static-electricity-free bearings for aerospace and other high-performance components.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1551-2916.2005.00539.x
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  • 2
    Electronic Resource
    Electronic Resource
    Synthesis of Aluminum Nitride Nanopowder by Gas-Reduction–Nitridation Method (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: Aluminum nitride (AlN) nanopowder was successfully synthesized from transition alumina nanopowder using an NH3–C3H8 gas mixture as a reduction–nitridation agent. Phase-pure, nanocrystalline AlN powder with a specific surface area of 36.4 m2/g and a mean particle size of 51 nm was prepared under typical reaction conditions. The resulting AlN nanopowders possessed excellent sinterability, allowing full densification in conventional processing, even without the addition of sintering aids.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1151-2916.2003.tb03420.x
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  • 3
    Electronic Resource
    Electronic Resource
    Hollow Beads Composed of Nanosize Ca α-SiAlON Grains (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: Carbothermal reduction—nitridation (CRN) of SiO2 is an attractive method to manufacture Si3N4 powders with controlled grain morphology. Moreover, β-SiAlON powders could also be synthesized from either pure powder mixture or some inexpensive raw minerals by CRN and the resulting powders favored the sintering of SiAlON product. However, there have been few works on preparing α-SiAlON powders so far. In this work, Ca α-SiAlON powder was synthesized by CRN of a SiO2—Al2O3—CaCO3 mixture. An unusual morphology of hollow beads 200 to 500 nm in diameter with a great deal of nanosize α-SiAlON particles around 10 to 30 nm in diameter was observed from the resultant Ca α-SiAlON powders, which has not been reported for SiAlON ceramics before.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1151-2916.2000.tb01316.x
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  • 4
    Electronic Resource
    Electronic Resource
    Aluminum Nitride Fibers Synthesized from Alumina Fibers Using Gas-Reduction–Nitridation Method (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: Aluminum nitride fibers were successfully synthesized from alumina fibers using an NH3–C3H8gas mixture as a reduction–nitridation agent. Observation using SEM clearly demonstrated that the morphology of the nitrided fibers was exactly the same as that of the raw alumina fibers, retaining the original regular shape and smooth surface. Up to 95% of the starting alumina was converted to aluminum nitride at 1400°C within 0.5 h via a single-step synthesis process.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1151-2916.2002.tb00159.x
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  • 5
    Electronic Resource
    Electronic Resource
    Microstructural Evolution during Sintering of Aluminum Nitride Ceramics Doped with Alumina and Yttria (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 of AlN sintered at 〉1950°C was studied in a specimen doped with 10 wt% Al2O3 and 5 wt% Y2O3. The constituent phases of the specimen were AlN, YAG, γ-AlON, and AlON polytypoids (compositional polytypes). Transmission and scanning electron microscopy revealed the microstructural characters: platelike 7AlN·Al2O3 first crystallized with concurrent formation of a residual liquid, then spherical AlN crystals formed. The liquid itself changed composition with the progress of the crystallization and reached the eutectic composition in the pseudobinary system AlN–YAG, and crystallized to an aggregate of AlN and YAG during cooling. As a product of the reaction of 7AlN·Al2O3, γ-AlON was formed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1151-2916.2001.tb00711.x
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  • 6
    Electronic Resource
    Electronic Resource
    Synthesis of AlN Powder by Carbothermal Reduction-Nitridation of Various Al2O3 Powders with CaF2 (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: We investigated the effect of characteristics of raw Al2O3 powder on the synthesis of AlN by the carbothermal reduction-nitridation method, in which CaF2 was added as a catalytic material. Four types of Al2O3 powders were selected. An Al2O3/C molar ratio of 0.29 was fixed, and the amount of CaF2 was varied from 3 to 30 wt%. The carbothermal reduction-nitridation was conducted from 1350° to 1450°C in N2 flow. The nitridation rate tended to increase with decreasing particle size of raw Al2O3 and was found to depend on the Al2O3 synthesizing method. The particle sizes of the synthesized AlN increased somewhat with increasing reaction temperatures. However, even though different particle sizes of Al2O3 powders were used, AlN powders synthesized under the same conditions exhibited almost the same particle size, round shape, and narrow size distribution. From XRD analysis, CaO·6Al2O3 and CaO·2Al2O3 were identified as intermediate compounds during these reactions. The above phenomena suggest that the synthesis mechanism of AlN powder by carbothermal reduction-nitridation of Al2O3 with CaF2 addition was the nitridation of the intermediate compounds through the liquid phase of the system CaF2-CaO·6Al2O3-CaO·2Al2O3.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1151-2916.1999.tb02193.x
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  • 7
    Electronic Resource
    Electronic Resource
    Effect of Diluents on Post-Reaction Sintering of Silicon Nitride Ceramics (2007)
    s.l. ; Stafa-Zurich, Switzerland
    Key engineering materials Vol. 352 (Aug. 2007), p. 185-188 
    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: Post-reaction sintering as a technique for the fabrication of Si3N4 ceramics has receivedmuch attention as a cost-effective process due to the use of cheap Si powder as a raw material. In thismethod, the rapid exothermic nitridation of Si results in local melting of Si to cause its agglomeration,which is expected to be a flaw after densification. Therefore, control of the exothermic reaction isneeded to improve the reliability of post-reaction sintered Si3N4 ceramics. In this study, Si3N4ceramics were fabricated by post-reaction sintering with Si3N4 or SiO2 powders in order to control theexothermic reaction. As a result, the microstructure and bending strength of Si3N4 ceramics waschanged by adding these additives. In particular, the addition of SiO2 resulted in the high strength ofSi3N4 ceramics. Consequently, it was found that Si3N4 and SiO2 particles played the role of diluents,and SiO2 was effective in post-reaction sintering as an oxygen donor
    Type of Medium: Electronic Resource
    URL: http://www.tib-hannover.de/fulltexts/2011/0528/01/55/transtech_doi~10.4028%252Fwww.scientific.net%252FKEM.352.185.pdf
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  • 8
    Electronic Resource
    Electronic Resource
    Improving the Microstructure of Si〈sub〉3〈/sub〉N〈sub〉4〈/sub〉-TiN Composites Using Ammonium Citrate to Disperse Raw TiO〈sub〉2〈/sub〉 Powders (2007)
    s.l. ; Stafa-Zurich, Switzerland
    Key engineering materials Vol. 352 (Aug. 2007), p. 115-118 
    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: Dense and homogenous Si3N4-TiN composites (5 vol% TiN) were prepared by using in situsynthesis method from Si3N4, AlN and TiO2 mixtures, containing Y2O3 and Al2O3 as sintering aids. Inthe prepared Si3N4-TiN composites, TiN grains were formed from TiO2 and AlN powders during thesintering process, in which ammonium citrate was used as a dispersant for raw TiO2 powders. Themicrostructures of the Si3N4-TiN composites with the increase of ammonium citrate wereinvestigated by scanning electron microscopy (SEM). Citrate ions modified on the surface of TiO2particles and protected the TiO2 particles in the mixed slurry to reduce the aggregations of TiO2powders, and homogenous Si3N4-TiO2-AlN composite powder was prepared for sintering. Themicrostuctures of Si3N4-TiN were developed after sintering with the uniform distribution of TiNgrains in the Si3N4 ceramics. It was found that the microstructure of Si3N4-TiN composite wasimproved significantly with 0.20 g ammonium citrate in the system, TiN grains with 0.2-0.3 μm indiameter distributed throughout Si3N4 matrix. It was a practical and useful way to improve themicrostructure of Si3N4-TiN composite without the alteration of the preparation procedure
    Type of Medium: Electronic Resource
    URL: http://www.tib-hannover.de/fulltexts/2011/0528/01/55/transtech_doi~10.4028%252Fwww.scientific.net%252FKEM.352.115.pdf
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  • 9
    Electronic Resource
    Electronic Resource
    Electrical Properties of Mn-Co-Ni Oxides Prepared at Low Temperatures (2007)
    s.l. ; Stafa-Zurich, Switzerland
    Advanced materials research Vol. 29-30 (Nov. 2007), p. 359-362 
    Details
    ISSN: 1662-8985
    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: Changes in crystal phase and electrical properties of oxides composed of Mn, Co, and Niwith the molar ratios of 5:2:1 and 3:3:1 were investigated. Starting oxides were fired from 250°C to800°C, then maintained at prescribed temperatures for 3 h in air. In the 5:2:1 specimen, a monophaseconsisting of a cubic spinel oxide that is important to electrical conductivity was obtained at firingtemperature of 800°C. In the 3:3:1 specimen, the monophase was obtained at temperatures rangingfrom 600°C to 800°C. Electrical resistance decreased exponentially with increasing temperature forall specimens fired at temperatures ranging from 250°C to 800°C, indicating that the oxides haveintrinsic thermistor characteristics with negative temperature coefficient (NTC). The temperaturedependence of the thermistor constant (B value) necessary for practical application was considered tobe related to the existence ratio of cubic spinel-type and ilmenite-type structures and the latticeconstant of the cubic spinel-type structure. The electrical conduction was stabilized by annealing atprescribed temperatures for more than 720 minutes
    Type of Medium: Electronic Resource
    URL: http://www.tib-hannover.de/fulltexts/2011/0528/01/40/transtech_doi~10.4028%252Fwww.scientific.net%252FAMR.29-30.359.pdf
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  • 10
    Electronic Resource
    Electronic Resource
    Sintering Shrinkage Behavior and Mechanical Properties of HfO〈sub〉2〈/sub〉-Added Si〈sub〉3〈/sub〉N〈sub〉4〈/sub〉 Ceramics (2008)
    s.l. ; Stafa-Zurich, Switzerland
    Key engineering materials Vol. 403 (Dec. 2008), p. 35-38 
    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: HfO2-added Si3N4 ceramics are known to exhibit excellent high-temperature strength and excellent damage characteristics because HfO2 assists the crystallization of the grain boundary phase. However, the sintering shrinkage behavior and mechanical properties of HfO2-added Si3N4 have not been well clarified so far, although it has been reported that TiO2, in which Ti is from the same group as Hf in the periodic table, enhances the densification of the Si3N4-Y2O3-Al2O3-AlN system and wear resistance due to TiN formed from TiO2 and AlN in the grain boundary. In the present study, we focus on HfO2 as the sintering aid to investigate the sintering shrinkage behavior and mechanical properties of HfO2-added Si3N4. The powder mixtures are prepared by the addition of HfO2 to the Si3N4-Y2O3-Al2O3 or Si3N4-Y2O3-Al2O3-AlN system. The sintering shrinkage curves of HfO2-added Si3N4 ceramics show rapid shrinkage at 1600°C as compared with those of the Si3N4 ceramics without HfO2.The shrinkage can be explained by the formation of SiO2-Y2O3-HfO2 derived liquid phases. Furthermore, the mechanical properties of HfO2-added Si3N4 were as excellent as those of the Si3N4 ceramics without HfO2
    Type of Medium: Electronic Resource
    URL: http://www.tib-hannover.de/fulltexts/2011/0528/01/58/transtech_doi~10.4028%252Fwww.scientific.net%252FKEM.403.35.pdf
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