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  • 1
    Electronic Resource
    Electronic Resource
    Structures of Filled α-Si3N4-Type Ca0.27La0.03Si11.38Al0.62N16 and LiSi9Al3O2N14 (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: Single crystals of the nitridosilicate Ca0.27La0.03Si11.38Al0.62N16 with a filled α-Si3N4-type structure were obtained when preparing lanthanum nitridosilicates in a graphite furnace accidentally containing calcium residues. The lithium α-SiAlON LiSi9Al3O2N14 was prepared using spark plasma sintering, with the sample containing in addition a β-SiAlON, LiAlSiO4, and a glass phase. The structure of Ca0.27La0.03Si11.38Al0.62N16 was refined using MoKα single-crystal data, in space group P31c with a= 7.838(1), c= 5.703(1) Å, V= 303.4 Å3, to a weighted R(Fobs2) = 6.0% for 475 unique reflections. The isotypic structure of LiSi9Al3O2N14 was refined with anisotropic thermal parameters and a= 7.8277(2), c= 5.6909(2) Å to RF= 0.63% for 849 reflections for d≥ 0.5 Å using time-of-flight (TOF) neutron powder diffraction (NPD) data. The SiX4 (X = N or N/O) tetrahedra are regular in both structures, with Si-N distances of 1.745(1) − 1.785(3) Å for the calcium-lanthanum compound and 1.741(1) − 1.765(1) Å for the lithium compound. The Ca/La and lithium atoms are located on the 2b position, (1/3, 2/3, z), coordinated by seven anions with the shortest metal-anion distances of 2.38(1) and 2.05(2) Å, respectively. The lithium atoms are displaced ∼0.28 Å relative to the position of the Ca/La atoms, and the lithium atoms can alternatively be described as tetrahedrally coordinated.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1151-2916.2003.tb03364.x
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  • 2
    Electronic Resource
    Electronic Resource
    Preparation of Titanium Nitride/Alumina Laminate Composites (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: A preparation route for TiN/Al2O3 laminate composites has been described. A water-based process using Al2O3 and TiN slurries with solids contents of 40 and 35 vol%, respectively, was used to make TiN and Al2O3 tapes. The removal of the binder was monitored by weight-loss measurements in a thermogravimetry unit. Bodies composed of Al2O3 and TiN tapes were densified at temperatures of 1400° and 1500°C using the Spark Plasma Sintering® (SPS) technique. Densities of 〉98% of the theoretical densities were approached. Crack-free and almost fully densified TiN/Al2O3 compacts were prepared by heating the burned-out green bodies to the final sintering temperature (1500°C) at a rate of 100°C/min, and with a holding time of 5–10 min, under a pressure of 75 MPa. The microstructures of the obtained compacts were studied using scanning electron microscopy. Grain sizes in the sintered Al2O3 and TiN compacts were similar to those of the precursor powders. Hardness and indentation fracture toughness were measured at room temperature, and the monolithic compacts as well as the laminate composites exhibited anisotropic mechanical behavior; i.e., the cracks propagated much more easily in a direction parallel to the laminas than perpendicular to them.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1151-2916.2002.tb00234.x
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  • 3
    Electronic Resource
    Electronic Resource
    Spark Plasma Sintering of Alumina (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: A systematic study of various spark plasma sintering (SPS) parameters, namely temperature, holding time, heating rate, pressure, and pulse sequence, was conducted to investigate their effect on the densification, grain-growth kinetics, hardness, and fracture toughness of a commercially available submicrometer-sized Al2O3 powder. The obtained experimental data clearly show that the SPS process enhances both densification and grain growth. Thus, Al2O3 could be fully densified at a much lower temperature (1150°C), within a much shorter time (minutes), than in more conventional sintering processes. It is suggested that the densification is enhanced in the initial part of the sintering cycle by a local spark-discharge process in the vicinity of contacting particles, and that both grain-boundary diffusion and grain-boundary migration are enhanced by the electrical field originating from the pulsed direct current used for heating the sample. Both the diffusion and the migration that promote the grain growth were found to be strongly dependent on temperature, implying that it is possible to retain the original fine-grained structure in fully densified bodies by avoiding a too high sintering temperature. Hardness values in the range 21–22 GPa and fracture toughness values of 3.5 ± 0.5 MPa·m1/2 were found for the compacts containing submicrometer-sized Al2O3 grains.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1151-2916.2002.tb00381.x
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  • 4
    Electronic Resource
    Electronic Resource
    Superfast Densification of Oxide/Oxide Ceramic Composites (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: Superfast densification of ceramic composites in the pseudobinary system Al2O3-Y3Al5O12 was carried out by using a new technique called spark plasma sintering (SPS). Dense ceramic composites were obtained by heating appropriate powder mixtures to 1573 K in an SPS unit at a rate of 600 K/min. No holding time at 1573 K was applied. Scanning electron microscopy studies showed the compacted materials to contain submicrometer-sized grains of the same sizes as the precursor powder mixtures; i.e., no significant grain growth had occurred.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1151-2916.1999.tb01874.x
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  • 5
    Electronic Resource
    Electronic Resource
    Stability and Oxidation Properties of RE-α-Sialon Ceramics (RE = Y, Nd, Sm, Yb) (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: Oxidation studies of hot-pressed RE-α-sialons, REx-Si12-4.5xAl4.5xO1.5xN16-1.5x (with x= 0.40 for RE = Nd, Sm, Yb; and x= 0.48 for RE = Y) were carried out in oxygen in a TG apparatus for ca. 20 h. Very good oxidation resistance was found for the Yb-doped samples, with parabolic rate constants Kp similar/congruent 0.09 10-6-3 10-6 mg2cm-4s-1 in the temperature range 1250-1350°C. The promising performance of this material was corroborated by long-term oxidation experiments (5 days) in air at 1350°C. Although the oxidation kinetics can be described by simple equations related to the parabolic rate law (e.g., the arctan equation, ΔW/A0=α arctan bt+ct), the oxidation process in these materials is likely to be complex. The significantly lower oxidation resistance of the RE = Nd, Sm doped α-sialons, especially at higher temperatures, is related to the formation of melilite, RE2Si3−yAlyO3+yN4−y (y∼ 1), in these systems. The melilite phase is also responsible for the thermal instability of the Nd- and Sm-α-sialons.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1151-2916.1998.tb02504.x
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  • 6
    Electronic Resource
    Electronic Resource
    Melilite Formation in a Samarium-Stabilized α-Sialon Ceramic during Postsintering Heat Treatments (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 formation of the melilite solid solution phase (M'), Sm2Si3−xAlxO3+xN4−x, in an α-sialon sample of overall composition Sm0.6Si9.28Al2.69O1.36N14.76, was studied as a function of time in the temperature interval 1375–1525°C. The alpha-sialon ceramic contained only minor amounts of the 21R sialon polytype and some residual grain-boundary glass before heat treatment. In situ studies by high-temperature X-ray diffraction were combined with postsintering heat treatment followed by quenching. The M'-phase was found to be formed by two different mechanisms: either crystallization of the residual grain-boundary liquid or a direct decomposition of the α-sialon phase. The liquid crystallized during the first 10–15 min of heat treatment, yielding a rapid M'-phase formation, and further formation of M'-phase continued at a much slower rate, related to the decomposition of α-sialon.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1151-2916.1997.tb02909.x
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  • 7
    Electronic Resource
    Electronic Resource
    Spark Plasma Sintering of Bismuth Titanate 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: Spark plasma sintering (SPS) was used to fabricate bismuth titanate (Bi4Ti3O12) ceramics. The densification, microstructure development and dielectric properties were investigated. It was found that the densification process was greatly enhanced during SPS. The sintering temperature was 200°C lower and the microstructure was much finer than that of the pressureless sintered ceramics, and dense compacts with a high density of over 99% were obtained at a wide temperature range of 800°–1100°C. Dielectric property measurement indicated that the volatilization of Bi3+ was greatly restrained during SPS, resulting in an unprecedented low dielectric loss for pure Bi4Ti3O12 ceramics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1551-2916.2005.00256.x
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  • 8
    Electronic Resource
    Electronic Resource
    Preparation of Ca3Co4O9 and Improvement of its Thermoelectric Properties by Spark Plasma Sintering (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 precursor powders of Ca3Co4O9 were synthesized by a sol–gel method. The results of X-ray diffraction and thermogravimetric and differential thermal analyses patterns indicate that pure Ca3Co4O9 powders could be obtained by calcining the precursor at 800°C for 2 h. High dense Ca3Co4O9 ceramic samples (∼99% of theoretical density) were prepared by the spark plasma sintering (SPS) method. Compared with the conventional sintering (CS), the SPS samples exhibit much higher electrical conductivity and power factor which are respectively about 118 S/cm and 3.51 × 10−4 W·(m·K2)−1. The SPS method is greatly effective for improving the thermoelectric properties of Ca3Co4O9 oxide ceramics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1551-2916.2005.00284.x
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  • 9
    Electronic Resource
    Electronic Resource
    Fabrication of Nanostructured Hydroxyapatite via Hydrothermal Synthesis and Spark Plasma Sintering (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: Hydrothermal synthesis has been used to produce hydroxyapatite (HA) particles with high crystallinity. Such particles of nanorods were used to fabricate HA ceramic by using spark plasma sintering. X-ray diffraction, transmission electron microscope, scanning electron microscope, and the BET method have been used to examine crystallite size, crystallite shape, and the surface area of particles, and grain size of sintered HA ceramics. It was found that the morphology of the nanorods in the HA particles changed to a more equiaxed shape during sintering.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1551-2916.2005.00198.x
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  • 10
    Electronic Resource
    Electronic Resource
    Rapid Densification and Deformation of Li-Doped Sialon Ceramics (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: Two lithium-doped sialon ceramics were densified and superplastically deformed by spark plasma sintering (SPS). Rapid densification with linear shrinkage rates of approximately 5 × 10−3 s−1 were observed for samples heated at a rate of 100°C/min up to ∼1400°C under a uniaxial pressure of 40 MPa. Isothermal deformation by SPS-preprepared, fully densified ceramics performed at T≥ 1450°C yielded strain rates in the order of 10−2 s−2. It is suggested that a high heating rate promotes material transport via formation of a nonequilibrated oxygen-rich liquid of low viscosity. This finding most likely holds true for other liquid-phase sintered ceramics as well and has implications for cost-effective manufacturing of ceramic components.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1551-2916.2004.00727.x
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