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
  • 1
    Electronic Resource
    Electronic Resource
    High Temperature Microhardness of Single Crystal Mullite (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: The microhardness (H) of single crystal, orthorhombic mullite was measured on (010) and (001) faces from room temperature up to 1400°C. The microhardness versus temperature curves display sigmoidal shapes. The mean microhardness at room temperature is ∼16 Gpa and it decreases with temperature to H is ∼ 13 GPa at 300°C. At 〉300°C, the microhardness is only slightly reduced with temperature to H is ∼10 GPa at 1000°C. Above this temperature limit, it markedly decreases again, to a mean value of ≈6 GPa at 1400°C. Up to ∼1000°C the (010) and (001) microhardnesses are very similar. Above ∼1000°C, however, the hardness gradually becomes anisotropic, with H(010) being twice as high as H(001) at 1400°C (H(010)∼ 8 GPa, H(001)∼ 4 GPa).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1551-2916.2004.00970.x
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 2
    Electronic Resource
    Electronic Resource
    AlO4/SiO4 Distribution in Tetrahedral Double Chains of Mullite (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 order–disorder of the tetrahedrally coordinated aluminum and silicon atoms in mullite has been investigated by means of 29Si nuclear magnetic resonance (NMR) spectroscopy. Sinter (3/2) and fused (2/1) mullites in the as-received state and reheated at 1750°C, and a reference sillimanite were used for this study. All mullites display similar 29Si NMR spectra: The strongest peak occurs at about −88 ppm, with two subpeaks close to −92 and −96 ppm. The −88 ppm signal is assigned to a sillimanite-type environment with three aluminum oxygen tetrahedra as next nearest neighbors of the silicon oxygen tetrahedra. The two 29Si NMR signals near −92 and −96 ppm are assigned to silicon oxygen tetrahedra surrounded by two aluminum oxygen and one silicon oxygen tetrahedra, and one aluminum oxygen and two silicon oxygen tetrahedra, respectively. 29Si NMR spectra with different short-range-order parameters were simulated by an array of 2 × 10 000 tetrahedral positions by means of an adapted random generator. The comparison between measured and simulated mullite and sillimanite 29Si NMR spectra yields a moderate degree of tetrahedral aluminum–silicon order, with no tendency toward cation demixing.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1551-2916.2005.00500.x
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 3
    Electronic Resource
    Electronic Resource
    Indentation-Induced Amorphization in Mullite Single Crystals (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: Hardness indentations with a Vickers pyramid under a load as low as 0.1 N applied at room temperature induce amorphization in single-crystal mullite when applied to the (001) crystallographic face. Different zones of damage were identified via TEM. Directly under the indenter, in the region of high-compressive stress, mullite becomes amorphous. Further out toward the matrix material, there exists a region of high plastic deformation in the form of dislocation networks, radial microcracks, and bend contours. The Vickers-induced damage is comparable to that produced by dynamic shock or intense ball milling of mullite.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1151-2916.2003.tb03566.x
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 4
    Electronic Resource
    Electronic Resource
    Secondary Ion Mass Spectroscopy Study of Oxygen-18 Tracer Diffusion in 2/1-Mullite Single Crystals (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: Oxygen 18O tracer diffusion in Czochralski-grown mullite single crystals is investigated along [010] and [001]. Oxygen diffusion coefficients range between ∼5 × 10−20 m2/s (1250°C) and ∼9 × 10−18 m2/s (1525°C). The data does not show any significant anisotropy. The values of the activation enthalpy (4.5 eV) and of the activation entropy ((3.4 ± 1.6)kB, where kB is the Boltzmann constant) suggest that the atomic transport occurs via thermally activated vacancies.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1151-2916.2001.tb01103.x
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 5
    Electronic Resource
    Electronic Resource
    Transformation of X-Phase SiAlON to Mullite (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 transformation of X-phase SiAlON (a composition of approximately Si3Al6O12N2) to 3/2 mullite (3Al2O3·2SiO2) plus vitreous silica (SiO2) at temperatures 〉1200°C has been studied in polycrystalline ceramics via transmission electron microscopy. The transformation of X-phase SiAlON to mullite is observed to be topotactical. Analyses of electron-diffraction patterns and lattice-fringe images reveal the following orientation relationship between X-phase SiAlON (X) and mullite (Mu): (110)Mu∥ (100)X and [001]Mu∥ [010]X. The observed orientation relationship between mullite and X-phase SiAlON and the close similarities between both structures-especially the occurrence of the same type of octahedral chains-suggest that these types of structural units are preserved during the transformation process. Excess noncrystalline SiO2 is exsolved between the mullite crystallites and is transported to the sample surface in later transformation stages.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1151-2916.1999.tb02021.x
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 6
    Electronic Resource
    Electronic Resource
    Reaction Sequence and Microstructrual Development of CeO2-Doped Reaction-Bonded Mullite (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: A promising technique for the fabrication of mullite ceramics and mullite-matrix composites with low dimensional changes (“near-net-shape processing”) is reaction bonding using Si metal and α-Al2O3 as starting materials, because sintering-induced shrinkage is compensated by Si-oxidation-induced volume expansion. A mullite reaction bonding (RBM) route which proceeds at much lower temperatures (lessthan equal to1350°C) than in conventional RBM systems (greaterthan equal to1500°C) is based on Ce doping which provides accelerated Si oxidation and mullite formation due to the formation of transient, low-viscosity Ce-Al-Si-O liquids. The present study shows that the required Ce-Al-Si-O liquids form in a reducing environment with Ce occurring as Ce3+. In an oxidizing environment, Ce is present as Ce4+, giving rise to precipitation of crystalline CeO2. Ce3+ left and right arrow Ce4+ redox reactions in the temperature range under consideration appear to be controlled by the presence of nonoxidized Si in the samples. According to the present investigation the amount of CeO2 added to the starting powders must be tailored carefully: Exaggerated CeO2 content produces large amounts of low-viscosity Ce-Al-Si-O liquids which may have the disadvantage of excessive sealing of the open porosity. This slows the oxygen diffusion velocity into the specimen considerably, with the consequence that nonoxidized Si and a residual Ce-Al-Si-O glass coexist in the ceramics after processing. A solution to this problem is to simultaneously enhance mullite crystal growth through seeding which works against excessive liquid-phase-induced shrinkage of the samples. This in turn enables complete oxidation and recrystallization of all liquid phases.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1151-2916.1999.tb02113.x
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 7
    Electronic Resource
    Electronic Resource
    Novel Low-Temperature Processing Route of Dense Mullite Ceramics by Reaction Sintering of Amorphous SiO2-Coated γ-Al2O3 Particle Nanocomposites (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: Dense mullite ceramics were successfully produced at temperatures below 1300°C from amorphous SiO2-coated gamma-Al2O3 particle nanocomposites (AS-gammaA). This method reduces processing temperatures by similar/congruent300°C or more with respect to amorphous SiO2-coated alpha-Al2O3 particle microcomposites (AS-alphaA) and to other Al2O3-SiO2 reaction couples. The good densification behavior and the relatively low mullite formation temperature make AS-gammaA nanocomposites an excellent matrix raw material for polycrystalline aluminosilicate fiber-reinforced mullite composites.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1151-2916.1999.tb01928.x
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 8
    Electronic Resource
    Electronic Resource
    Accelerated Reaction Bonding of Mullite (1998)
    Westerville, Ohio : American Ceramics Society
    Journal of the American Ceramic Society 81 (1998), 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 suitable way to process mullite ceramics and mullite-matrix composites with low dimensional changes (“near-net-shape processing”) is reaction bonding, using silicon metal and corundum (α-Al2O3) as starting materials, be-cause sintering-induced shrinkage is compensated by vol-ume expansion caused by the silicon-oxidation-induced vol-ume expansion. This work describes a new reaction-bonded mullite (RBM) processing route that proceeds at much lower temperatures (≤1350°C) than in “normal” RBM systems (≥1550°C). Accelerated silicon oxidation and mullite formation are effected by adding low amounts of yttria (Y2O3) or ceria (CeO2) to the green powder mixtures, which causes the formation of transient, metastable, and low-viscosity Y-Al-Si-O and Ce-Al-Si-O partial melts. After long-term heat treatments at ≤1350°C, however, the intermediate liquids recrystallize and leave behind RBM ceramics that are homogeneous, substantially glass-free, and relatively dense. These two RBM materials consist of mullite, α-Al2O3, and Y2Si2O7 or CeO2, respectively.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1151-2916.1998.tb02569.x
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 9
    Electronic Resource
    Electronic Resource
    Thermal Degradation of Fiber Coatings in Mullite-Fiber-Reinforced Mullite Composites (1997)
    Westerville, Ohio : American Ceramics Society
    Journal of the American Ceramic Society 80 (1997), 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 thermal degradation behavior of single-layer BN and of double-layer BN/SiC chemically vapor-deposited fiber coatings in mullite-fiber-reinforced mullite composites was investigated by means of transmission electron microscopy after processing and heat treatment of the composites at 1000°, 1200°, and 1300°C for 6 h in air. The single-layer BN coatings were ˜0.7 mu m thick and consisted of turbostratic BN with (0001) basal planes lying parallel to the surfaces of the fibers plus nanosized areas that had no preferential orientation. This microstructure remained unchanged up to 1000°C; however, distinct coarsening of the randomly oriented BN crystallites occurred in the temperature range of 1000°-1200°C. The single-layer BN coatings were stable against oxidation, up to 1200°C. At higher temperatures, degradation of the coatings via oxidation occurred. Double-layer BN/SiC coating systems consisted of BN that was 0.08 mu m thick and SiC layers that were 0.16 mu m thick and deposited onto the mullite fibers. The turbostratic BN was highly anisotropic and did not undergo any microstructural change, up to 1300°C. The outer SiC layer of the double-layer coating system improved the oxidation resistance of BN in the 1200°-1300°C temperature range, despite a partial oxidation of SiC to SiO2.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1151-2916.1997.tb03099.x
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 10
    Electronic Resource
    Electronic Resource
    Yttrium Silicate Coatings on Chemical Vapor Deposition-SiC-Precoated C/C–SiC: Thermodynamic Assessment and High-Temperature Investigation (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: Yttrium silicates are promising materials for improved oxidation and erosion protection for carbon fiber-reinforced composites. A two-layer coating system of low-pressure plasma-sprayed yttrium silicate on chemical vapor deposition-SiC-precoated C/C–SiC was tested under atmospheric re-entry conditions simulated within a plasma wind tunnel test facility. The thermal expansion behavior of Y2SiO5 and Y2Si2O7 was investigated. The chemical compatibility with and without increasing oxygen partial pressure at the interface of the two-layer system was calculated by the CALPHAD method. The calculations were compared with experimental results. Furthermore, a thermodynamic explanation is presented to understand and predict the observed coating failure mechanism, identified as blister formation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1551-2916.2005.00077.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...