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  • 2000-2004  (20)
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Material
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Year
  • 1
    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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  • 2
    Electronic Resource
    Electronic Resource
    High-Surface-Area Alumina Ceramics Fabricated by the Decomposition of Al(OH)3 (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: Al2O3-based porous ceramics with high surface areas were fabricated by adding Al(OH)3 to the starting powder, followed by pressureless sintering at temperatures 〉1100°C. Three types of starting powders were used in the present study: pure α-Al2O3, α-Al2O3+ Al(OH)3, and α-Al2O3+ ZrO2+ Al(OH)3. The addition of Al(OH)3 considerably increased the surface area of the porous Al2O3, and the addition of ZrO2 further increased the surface area; a surface area as high as 36.39 m2/g was obtained, and the high surface area was retained at higher temperature. The pore size distribution of the specimens with high surface area was bimodal, with one peak at ∼100 nm and the other, which contributed most of the surface area, at ∼10 nm. X-ray analysis showed that in the sample with the fine pores and high surface area, there was θ-Al2O3 phase produced by the decomposition of Al(OH)3, presumably because the phase transformation of θ-Al2O3 to α-Al2O3 was incomplete after low-temperature sintering. Moreover, the porous Al2O3 with high surface area retained superior mechanical properties, attributed to the good sinterability of the fine α-Al2O3 powder used in the present study. The sintered specimens could be large and designed to any shape, because pressureless sintering was used for fabrication. The present approach provides a new way of fabricating porous Al2O3 ceramics that could be widely used as catalyst supports in industry, especially for high-temperature catalysis.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1151-2916.2001.tb00687.x
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  • 3
    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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  • 4
    Electronic Resource
    Electronic Resource
    Bioluminescent imaging of Cdk2 inhibition in vivo (2004)
    [s.l.] : Nature Publishing Group
    Nature medicine 10 (2004), S. 643-648 
    Details
    ISSN: 1546-170X
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Medicine
    Notes: [Auszug] Many proteins and pathways of pharmaceutical interest impinge on ubiquitin ligases or their substrates. The cyclin-dependent kinase (Cdk) inhibitor p27, for example, is polyubiquitylated in a cell cycle–dependent manner by a ubiquitin ligase complex containing the F-box protein Skp2. ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/nm1047
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  • 5
    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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  • 6
    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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  • 7
    Electronic Resource
    Electronic Resource
    Reaction Synthesis of Aluminum Nitride–Boron Nitride Composites Based on the Nitridation of Aluminum Boride (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–boron nitride (AlN–BN) composites were prepared based on the nitridation of aluminum boride (AlB2). AlN powder was added to change the BN volume fraction in the obtained composites. Thermogravimetry–differential thermal analysis (TG-DTA), X-ray diffractometry, and the nitridation ratio were used to investigate the nitridation process of AlB2. At ∼1000°C, a sharp exothermic peak occurred in the DTA curve, corresponding to the rapid nitridation of aluminum in AlB2. On the other hand, the nitridation of the transient phase, Al1.67B22, was very slow when the temperature was 〈1400°C. However, the nitridation speed obviously accelerated at temperatures 〉1600°C. The pressure of the nitrogen atmosphere was also an important factor; high nitrogen pressure remarkably promoted nitridation. Treatment at 2000°C was disadvantageous for nitridation, because of the rapid formation of a dense surface layer that inhibited nitrogen diffusion into the specimen interior. Three specimens, with 5 wt% Y2O3 additive and different BN contents, were prepared by pressureless reactive sintering, according to the determined sintering schedule. Electron microscopy (scanning and transmission) observations revealed that the in-situ-formed BN flakes were homogeneously and isotropically distributed in the AlN matrix. A schematic mechanism for microstructural formation was developed, based on the results of nitridation and the microstructural features of the obtained composites. The obtained composites, with a low BN content, exhibited a high bending strength, comparable to that of reported hot-pressed AlN–BN composites.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1151-2916.2002.tb00559.x
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  • 8
    Electronic Resource
    Electronic Resource
    Microstructure and Mechanical Properties of Porous Alumina Ceramics Fabricated by the Decomposition of Aluminum Hydroxide (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 mechanical properties of Al2O3-based porous ceramics fabricated from pure Al2O3 powder and the mixtures with Al(OH)3 were investigated. The fracture strength of the porous Al2O3 specimens sintered from the mixture was substantially higher than that of the pure Al2O3 sintered specimens because of strong grain bonding that resulted from the fine Al2O3 grains produced by the decomposition of Al(OH)3. However, the elastic modulus of the porous Al2O3 specimens did not increase with the incorporation of Al(OH)3, so that the strain to failure of the porous Al2O3 ceramics increased considerably, especially in the specimens with high porosity, because of the unique pore structures related to the large original Al(OH)3 particles. Fracture toughness also increased with the addition of Al(OH)3 in the specimens with higher porosity. However, fracture toughness did not improve in the specimens with lower porosity because of the fracture-mode transition from intergranular, at higher porosity, to transgranular, at lower porosity.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1151-2916.2001.tb01065.x
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  • 9
    Electronic Resource
    Electronic Resource
    In Situ Reaction Synthesis of Silicon Carbide–Boron Nitride 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: SiC–BN composites were prepared via the proposed in situ reaction, which used Si3N4, B4C, and carbon as reactants. Adding SiC powder to the reactants controlled the BN content in the composite. For comparison, SiC–BN composites with the same phase compositions were produced via conventional processing. The in situ process was advantageous for obtaining better composites with fine grain size and homogeneous microstructures. The in situ composite that had a BN content of 53.71 vol% exhibited considerably high strength (342 MPa) and a very low elastic modulus (107 GPa). The SiC–25-vol%-BN in situ composite had a peak strength of 588 MPa, which was 95% of that of monolithic SiC; however, the elastic modulus was as low as half that of monolithic SiC. These in situ SiC–BN composites can be expected to have excellent thermal shock resistance and mechanical strain tolerance.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1151-2916.2001.tb00863.x
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  • 10
    Electronic Resource
    Electronic Resource
    Fabrication of Low-Shrinkage, Porous Silicon Nitride Ceramics by Addition of a Small Amount of Carbon (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: Successful net-shape sintering offers a significant advantage for producing large or complicated products. Porous Si3N4 ceramics with very low shrinkage were developed, in the present investigation, by the addition of a small amount of carbon. Carbon powders (1–5 vol%) of two types, with different mean particle sizes (13 nm and 5 μm), were added to α-Si3N4−5 wt% Y2O3 powders. SiC nanoparticles formed through reaction of the added carbon with SiO2 on the Si3N4 surface or with the Si3N4 particles themselves. Such reaction-formed SiC nanoparticles apparently had an effective reinforcing effect, as in nanocomposites. Sintered Si3N4 porous ceramics with a high porosity of 50%–60%, a very small linear shrinkage of ∼2%–3%, and a strength of ∼100 MPa were obtained.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1151-2916.2001.tb00890.x
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