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  • 1
    Electronic Resource
    Electronic Resource
    Processing Aluminum Nitride-Silicon Carbide Composites via Polymer Infiltration and Pyrolysis of Polymethylsilane, a Precursor to Stoichiometric Silicon Carbide (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: AlN-SiC-particle-reinforced composites have been prepared at lessthan equal to1400°C using submicrometer AlN, -325 mesh alpha-SiC particles, and polymethylsilane (PMS; -(CH3SiH)n-) via a polymer infiltration and pyrolysis (PIP) process. PMS is an organometallic SiC polymer precursor that can be modified with 16 wt% cross-linking aid to provide mPMS. mPMS converts to nanocrystalline β-SiC with 〉80% ceramic yield (1000°C in argon) with some excess (〈5 wt%) graphitic carbon. mPMS has been used successfully as a nonfugitive binder for AlN-SiC compacts. Densities of 2.5 versus 2.1 g/cm3 have been obtained after nine PIP cycles for disk-shaped compacts formulated with and without mPMS binder, respectively. alpha-SiC seeds crystallization of β-SiC derived from mPMS at temperatures as low as 1000°C. Some evidence suggests that AlN-SiC solid solutions form at particle/matrix interfaces.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1151-2916.1999.tb01846.x
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  • 2
    Electronic Resource
    Electronic Resource
    A Processable Mullite Precursor Prepared by Reacting Silica and Aluminum Hydroxide with Triethanolamine in Ethylene Glycol: Structural Evolution on Pyrolysis (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: A simple, processable precursor to mullite can be synthesized in quantities of 100 g in a few hours by direct reaction of silica, aluminum hydroxide, and triethanolamine in ethylene glycol. To delineate a processing window whereby precursor shapes can be transformed into mullite, the chemical and phase microstructural evolution of this precursor on pyrolysis to selected temperatures in air is followed by thermal gravimetric analysis, differential thermal analysis, diffuse reflectance infrared Fourier transform spectroscopy, solid-state 27Al and 29Si nuclear magnetic resonance, X-ray diffractometry, and Brunauer-Emmett-Teller analytical methods. The precursor behaves as a single-phase, atomically mixed material that initially transforms to a porous, amorphous aluminosilicate when heated to temperatures as high as 950°C. Above 950°C, the precursor first transforms to tetragonal mullite, based on comparison with the literature, and, on continued heating above 1200°C, to orthorhombic mullite with coincident loss of porosity.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1151-2916.1997.tb03162.x
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  • 3
    Electronic Resource
    Electronic Resource
    Flame Spray Pyrolysis of Precursors as a Route to Nano-mullite Powder: Powder Characterization and Sintering Behavior (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 flame spray pyrolysis of alcohol-soluble precursors allows the synthesis of mullite-composition nanopowders (average size of ∼60–100 nm) that, when annealed carefully, provide processable nano-mullite powders. The powders have been characterized using several spectroscopic and microscopy methods, including thermal gravimetric analysis, differential thermal analysis, diffuse reflectance infrared Fourier transform spectroscopy, and transmission electron microscopy. Preliminary studies on the pressureless-sintering behavior of these powders are presented. Without additives or any efforts to optimize the process, powder compacts could be sintered to relative densities of 〉90%, with grain sizes of 〈500 nm at 1600°C.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1151-2916.2001.tb00774.x
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  • 4
    Electronic Resource
    Electronic Resource
    Yttrium Aluminum Garnet Fibers from Metalloorganic Precursors (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: Mixtures of yttrium acetate hydrate (Y(O2CCH3)34H2O) and aluminum formate hydrate (Al(O2CH)33H2O in H2O) or yttrium isobutyrate (Y[O2CCH(CH3)2]3) and aluminum isobutyrate (Al[O2CCH(CH3)2]3) in tetrahydrofuran were used as precursors to process yttrium aluminum garnet (YAG, Al5Y3O12) fibers. The pyrolytic decomposition patterns of Al(O2CH)33H2O, Y(O2CCH3)34H2O, and a [3Y(O2CCH3)34H2O/5Al(O2CH)33H2O] YAG stoichiometry mixture were assessed by heating samples to selected temperatures and characterizing the products by thermogravimetric analysis, differential thermal analysis, X-ray diffractometry, and Fourier transform infrared spectroscopy. The YAG acetate/formate precursor decomposes to an amorphous intermediate at temperatures 〉400°C and crystallizes (at ∼800°C) to phase-pure YAG with a ceramic yield of 40% at 1000°C. YAG isobutyrate precursor fibers were extruded or hand drawn. YAG acetate/formate precursor fibers were formed using a commercial extruder. The pyrolysis behavior of both precursor fibers was studied to identify the best pyrolysis conditions for producing dense, defect-free ceramic fibers. Only thin (diameter of 〈30 μm) precursor fibers could be processed to dense, defect-free, thin YAG fibers (diameter of 〈20 μm). For the YAG isobutyrate precursor, crack-free crystalline YAG fibers (diameter of ∼7 μm) were obtained at 1000°C. For YAG acetate/formate precursor fibers, dwell times of 2 h at temperatures of 400° and 900°C were necessary to process fully dense, defect-free ceramic fibers. Heating the resulting 900°C fibers (at a rate of 30°C/min) to 1570°-1650°C gave dense fibers with grain sizes of 0.7-3.2 μm and bend strengths of up to 1.7 ± 0.2 GPa (for fibers that had a diameter of ∼10 μm and had undergone sintering at 1600°C).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1151-2916.1998.tb02383.x
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  • 5
    Electronic Resource
    Electronic Resource
    Synthesis of Ultrafine β″-Alumina Powders via Flame Spray Pyrolysis of Polymeric Precursors (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: Flame spray pyrolysis of a polymeric precursor is used to prepare ultrafine powders that, when sintered, convert to essentially pure phase lithium-doped sodium β″-alumina. The precursor Na1.67 Al10.67 Li0.33 [N(CH2CH2O)3]10.67-[OCH2CH2O]·x(HOCH2CH2OH) has been synthesized from stoichiometric amounts of metal hydroxides and tri-ethanolamine (N(CH2CH2OH)3, TEA) in excess ethylene glycol. The precursor is dissolved in ethanol, and an atom-ized spray of the solution is combusted in a specially con-structed flame spray apparatus. Combustion occurs at ∼2000°C, followed by immediate quenching. This proce-dure provides for a measure of kinetic control over the process. The resulting nanopowder particles are 50–150 nm in diameter and exhibit powder X-ray diffractometry pat-terns similar to β″-alumina. Heating the nanopowder at 30°C/min to 1200°C with a 1 hisotherm converts it to pure β″-alumina. In preliminary sintering studies, green powder compacts (∼65% theoretical density) sintered at 1600°C for 12 min densify to 3.0 ± 0.1 g/cm 3 (∼92% theoretical density) with minimal loss of Na2O. This procedure offers several processing and cost advantages over conventional β″-alumina syntheses.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1151-2916.1998.tb02506.x
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  • 6
    Electronic Resource
    Electronic Resource
    Titanium Nitride/Carbon Coatings on Graphite Fibers (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: Titanium nitride (TiN) coatings were applied to graphite-fiber tows by dip coating desized (900°C in nitrogen) fibers in hexane solutions containing 0.5, 1, or 2 equivalent wt% TiN as the precursor, [Ti(NMe2)x(μ–NCHMe2)4−2x]n. The precursor was characterized by thermogravimetric analysis (TGA), chemical analysis, and nuclear magnetic resonance. Bulk samples of precursor were heated to selected temperatures in argon. Based on microstructural and chemical analyses, two pyrolysis temperatures— 900°C and 1200°C— were selected for more-detailed studies predicated on fiber oxidation-resistance behavior. At 900°C, the bulk material exhibited a powder X-ray diffractometry (XRD) pattern consistent with microcrystalline TiN, although some free carbon remained. XRD analysis of the samples pyrolyzed to 1200°C indicated a higher degree of crystallinity and some carbon incorporation in the TiN lattice; e.g., a TiCN solid solution forms, as supported by chemical and TGA analyses. Fibers coated with precursor were heated at a rate of 10°C/min in argon to selected temperatures, followed by a hold for 1 h, and the resulting coatings were characterized by scanning electron microscopy, X-ray photoemission spectroscopy, and oxidation resistance at 700°C for 2 h in air. Coated fibers pyrolyzed to 900° and 1200°C were studied in detail. Fibers heat treated at 900°C exhibited better oxidation resistance than fibers pretreated at 1200°C, as determined by mass loss. Uncoated fiber tows fully oxidized after 80 min. The oxidation-resistance studies on fiber tows pretreated at 900°C and coated with 0.5, 1, and 2 equivalent wt% TiN indicated that the sample with a coating of 1 wt%, with thicknesses of 0.1–0.2 μm, was the most stable. The coatings of 0.5 equivalent wt% TiN were irregular, whereas the coatings of 2 equivalent wt% TiN exhibited process-related cracking, leading to poor oxidation resistance.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1151-2916.1997.tb02888.x
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  • 7
    Electronic Resource
    Electronic Resource
    Preceramic Polymer Route to Amorphous and Crystalline Potassium Aluminosilicate Powders and Their Electrorheological Properties (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 oxide one-pot synthesis (OOPS) process was used to synthesize a polymer precursor to potassium aluminosilicate, KAlSiO4 (KASp). A KAlSiO4 gel (KASg) also was produced via a solgel route using the same precursor. The two routes to KAlSiO4 were explored to compare the effects of the two processing methods on powder properties. The KASp and KASg powders both transformed on heating (.500°C) to amorphous, high-surface-area powders with narrow pore-size distributions (4–24 nm). These anhydrous, amorphous powders were intrinsic electrorheological (ER) materials. Both materials crystallized at } 1070°C, and thermogravimetric analysis, differential thermal analysis, and X-ray diffractometry suggested that they were identical. Diffuse reflectance infrared Fourier transform spectroscopy and scanning electron microscopy proved that the KASp powders were homogeneous, whereas the KASg powders were heterogeneous and segregated. The KASg powders exhibited better ER properties that were associated with the segregated phases.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1151-2916.1997.tb03001.x
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