ALBERT

All Library Books, journals and Electronic Records Telegrafenberg

X
feed icon rss

Your email was sent successfully. Check your inbox.

An error occurred while sending the email. Please try again.

Proceed reservation?

Export
  • 11
    Electronic Resource
    Electronic Resource
    Distribution of Cerium Ions in Cerium-Doped α′-SiAlON and Its Effect on Grain Morphology (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: Cerium-doped α′-SiAlON material was prepared by spark plasma sintering at 1750°C under 30 MPa pressure for 10 min. Yttrium α′-SiAlON seeds (1 wt%) were added to the starting powder mixture. Recent work showed that up to 45 wt% of α′-SiAlON phases are formed in the present sintered ceramics. The material presented a microstructure, containing rodlike cerium-doped α′-SiAlON crystals. In this paper, transmission electron microscopy and energy dispersive spectroscopy examinations of the α′-SiAlON grains are reported. The structural analyses revealed a high density of domain boundaries, within which larger amounts of cerium ions were segregated than in the matrix. The density of the domain boundaries was proportional to the amount of incorporated cerium ions. These structural defects eventually dominated the growth habits of the α′-SiAlON crystals, by modifying the structure of the interstices at the boundary sites. The role of yttrium α′-SiAlON seeds also is discussed in this paper.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1151-2916.2002.tb00112.x
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 12
    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
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 13
    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
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 14
    Electronic Resource
    Electronic Resource
    High-Temperature Strength of Liquid-Phase-Sintered SiC with AlN and Re2O3 (RE = Y, Yb) (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: Using AlN and RE2O3 (RE = Y, Yb) as sintering additives, two different SiC ceramics with high strength at 1500°C were fabricated by hot-pressing and subsequent annealing under pressure. The ceramics had a self-reinforced microstructure consisting of elongated α-SiC grains and a grain-boundary glassy phase. High-temperature strength up to 1600°C was measured and compared with that of the SiC ceramics fabricated with AlN and Er2O3. SiC ceramics with AlN and Y2O3 showed the best strength (∼630 MPa) at 1500°C, while SiC ceramics with AlN and Er2O3 the best strength (∼550 MPa) at 1600°C.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1151-2916.2002.tb00211.x
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 15
    Electronic Resource
    Electronic Resource
    Phase Transformation and Texture in Hot-Forged or Annealed Liquid-Phase-Sintered Silicon Carbide 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: Starting from three powder mixtures of 80 vol% SiC (100α, 50α/50β, 100β) and 20 vol% YAG, liquid-phase-sintered silicon carbide ceramics were prepared by hot pressing at 1800°C for 1 h under 25 MPa, and then by hot forging or annealing at 1900°C for 4 h under an applied stress of 25 MPa in argon. The phase transformation and texture development in the as-hot-pressed, hot-forged, and annealed SiC ceramics were investigated via X-ray diffraction (XRD) and the pole figure measurements. The 6H → 4H polytypic transformation was observed in samples consisting of both α- and β-SiC phases when subjected to compressive deformation but absent in the case of annealing, suggesting the deformation-enhanced solubility of aluminum in SiC. Deformation was also found to enhance the 3C → 4H transformation in the sample containing entirely β-phase, which is due to the accelerated solution-precipitation process assisted by grain boundary sliding. The current study showed that the β- →α-phase transformation had little effect on texture development in SiC. Hot forging generally produced the strongest texture, with the calculated maximum of 2.2 times random in samples started with pure α-SiC phase. The mechanism for texture development was explained based on the microstructural observations.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1151-2916.2002.tb00111.x
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 16
    Electronic Resource
    Electronic Resource
    Microstructural Analysis of Liquid-Phase-Sintered β-Silicon Carbide (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 microstructures of fine-grained β-SiC materials with α-SiC seeds annealed either with or without uniaxial pressure at 1900°C for 4 h in an argon atmosphere were investigated using analytical electron microscopy and high-resolution electron microscopy (HREM). An applied annealing pressure can greatly retard phase transformation and grain growth. The material annealed with pressure consisted of fine grains with β-SiC as a major phase. In contrast, the microstructure in the material annealed without pressure consisted of elongated grains with half α-SiC. Energy-dispersive X-ray analysis showed no differences in the amount of segregation of aluminum and oxygen atoms at grain boundaries, but did show a significant difference in the segregation of yttrium atoms at grain boundaries along SiC grains for the two materials. The increased segregation of yttrium ions at grain boundaries caused by the applied pressure might be the reason for the retarded phase transformation and grain growth. HREM showed a thin secondary phase of 1 nm at the grain boundary interface for both materials. The development of a composite grain consisting of a mixture of β/α polytypes during annealing was a feature common to both materials. The possible mechanisms for grain growth and phase transformation are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1151-2916.2002.tb00107.x
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 17
    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
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 18
    Electronic Resource
    Electronic Resource
    Synthesis and Sintering of Cerium(II) Monosulfide (2004)
    Oxford, UK : Blackwell Publishing Ltd
    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 monosulfide (CeS) powder was synthesized by the reduction of Ce2S3 powder with metallic Ce, which was obtained from ceria (CeO2) powder using carbon disulfide (CS2) gas. To obtain the maximum amount of CeS from a mixture of Ce2S3 and Ce, an excess amount of metallic Ce, a stoichiometric composition, was necessary in the synthesis at 1273 K for 10.8 ks. The preliminary sintering experiments also were performed using a synthetic CeS powder containing a small amount of Ce, Ce2O2S, and β-Ce2S3 as impurities. It was found that the oxygen content in the sintered compact decreases gradually as the sintering temperature increases, because of the removal of the impurities due to the evaporation of the volatile CeO. Single-phase CeS was formed by sintering at 2173 K. To evaluate the activation energy for densification of single-phase CeS, a CeS powder was prepared by milling an initial sintered compact and was used as an ingredient for hot-press experiments. Densification data during hot-press sintering were analyzed using a kinetic equation, showing that boundary diffusion is a rate-limiting process. The results suggest that this boundary diffusion model can explain well the densification data, with an apparent activation energy of 479 kJ·mol-1.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1151-2916.2004.tb19939.x
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 19
    Electronic Resource
    Electronic Resource
    Dynamic Evolution of Grain-Boundary Films in Liquid-Phase-Sintered Ultrafine Silicon Carbide Material (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: Spatially resolved electron energy-loss spectroscopy (EELS) analysis revealed a dynamic evolution of grain-boundary (GB) films in a liquid phase (Al2O3–Y2O3–CaO) sintered β-SiC, which had been deformed both in tension and in compression. An effective chemical width was measured from the oxygen segregation to GBs. Significant increase of Al content in GB films was correlated to devitrification of amorphous pockets to form YAG during both deformations. This brought Y into and expelled Al from the pockets. The extra Al was pushed into GBs to form alumina-based films. Al-Y interdiffusion between GB films and pockets is related to deformation time, indicating a constant and limited interdiffusion rate. This evolution of GB films demonstrated that the dynamic process equilibrated these intergranular regions and phases. GB sliding and interdiffusion among intergranular regions were common mechanisms for both deformation modes. Fracture was mainly caused by YAG formation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1151-2916.2003.tb03550.x
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 20
    Electronic Resource
    Electronic Resource
    Fabrication of Dense Nanostructured Silicon Carbide Ceramics through Two-Step Sintering (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: SiC powder compacts were prepared with Al2O3, Y2O3, and CaO powders. By two-step sintering, fully dense nanostructured SiC ceramics with a grain sizes of ∼40 nm were obtained. The grain size–density trajectories are compared with those of conventional sintering processes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1151-2916.2003.tb03560.x
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
Close ⊗
This website uses cookies and the analysis tool Matomo. More information can be found here...