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  • 1
    Electronic Resource
    Electronic Resource
    s.l. ; Stafa-Zurich, Switzerland
    Materials science forum Vol. 510-511 (Mar. 2006), p. 350-353 
    ISSN: 1662-9752
    Source: Scientific.Net: Materials Science & Technology / Trans Tech Publications Archiv 1984-2008
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: The effects of B addition up to 0.4 wt% (i.e., 1.61 at%) to Fe-40Al alloy onmicrostructures and tensile properties were investigated. The vacancy-annealed specimens following casting and extrusion were examined by optical and scanning electron microscopy and thermal neutron-induced microradiography. The addition of a large amount of B resulted in grain refinement and changed the fracture mode from intergranular to transgranular to increase the tensile elongation. Especially, the alloy containing 0.3wt% B exhibited the elongation of 16.4% under the strain rate of 1x100s-1 at room temperature. The increase in elongation with increasing strain ratewas discussed in terms of suppression of hydrogen embrittlement
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Science Inc
    Journal of the American Ceramic Society 88 (2005), S. 0 
    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 facile chemical route to prepare a well-defined Ni powder on a mass-production scale without external heating was suggested. A highly concentrated Ni complex was formed between NiCl2 and N2H4 solution, and subsequent addition of NaOH solution triggered serial reactions from the Ni complex decomposition via Ni(OH)2 formation to the reduction of a Ni(OH)2 gel into well-defined Ni spheres. The high temperature necessary for the reaction was attained not by external heating but by exothermic reactions such as complex formation and reduction. The preparation of monodisperse and spherical Ni powder was attributed to uniform distribution of the reducing agent (N2H4) within the Ni(OH)2 gel.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Westerville, Ohio : American Ceramics Society
    Journal of the American Ceramic Society 87 (2004), S. 0 
    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 present contribution reports some interesting and new results obtained while developing yttria-stabilized tetragonal zirconia (Y-TZP) using spark plasma sintering (SPS). The experimental results clearly showed that ZrO2-nanoceramics with high hardness(∼14.5 GPa) can be processed at a lower sintering temperature of 1200°C in a short time (5 min). Another important result is that the newly developed Y-TZP nanoceramics, compared with the conventional sintered TZP, exhibit better fretting wear resistance against bearing steel. The intergranular fracture and the grain pullout were observed as the major wear mechanisms of the zirconia nanoceramics.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Westerville, Ohio : American Ceramics Society
    Journal of the American Ceramic Society 85 (2002), S. 0 
    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: Impedance spectroscopy with millimeter-scale electrodes was used to determine the local grain-boundary resistivity (ρgb) of a 1-mol%-Al2O3-doped CaO-stabilized ZrO2 (CSZ) specimen. A much higher ρgb at the specimen surface was observed compared with that of the specimen interior. The result was mainly due to the difference in the dihedral angle of the intergranular phase, which was ∼20° at the surface and ∼100° at the interior.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Westerville, Ohio : American Ceramics Society
    Journal of the American Ceramic Society 87 (2004), S. 0 
    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: In the present work, we report the processing of ultrahard tungsten carbide (WC) nanocomposites with 6 wt% zirconia additions. The densification is conducted by the spark plasma sintering (SPS) technique in a vacuum. Fully dense materials are obtained after SPS at 1300°C for 5 min. The sinterability and mechanical properties of the WC–6 wt% ZrO2 materials are compared with the conventional WC–6 wt% Co materials. Because of the high heating rate, lower sintering temperature, and short holding time involved in SPS, extremely fine zirconia particles (∼100 nm) and submicrometer WC grains are retained in the WC–ZrO2 nanostructured composites. Independent of the processing route (SPS or pressureless sintering in a vacuum), superior hardness (21–24 GPa) is obtained with the newly developed WC–ZrO2 materials compared with that of the WC–Co materials (15–17 GPa). This extremely high hardness of the novel WC–ZrO2 composites is expected to lead to significantly higher abrasive-wear resistance.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Westerville, Ohio : American Ceramics Society
    Journal of the American Ceramic Society 86 (2003), S. 0 
    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: In a 15-mol%-CaO-stabilized zirconia (CSZ) specimen, the grain boundaries at the surface region exhibited a lower electrical resistance than those at the inner region. However, when up to 1.5 mol% Al2O3 was added, the grain boundaries at the surface showed a higher resistance. These results were explained in terms of redistribution of the intergranular-liquid phase during CSZ sintering.
    Type of Medium: Electronic Resource
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  • 7
    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 scavenging of a resistive siliceous phase via the addition of Al2O3 was studied, using imaging secondary-ion mass spectroscopy (SIMS), given the improved grain-boundary conductivity in 8-mol%-yttria-stabilized zirconia (8YSZ). The grain-boundary resistivity in 8YSZ decreased noticeably with the addition of 1 mol% of Al2O3. Strong SiO2 segregation at the grain boundaries was observed in a SIMS map of pure 8YSZ that contained 120 ppm of SiO2 (by weight). The addition of 1 mol% of Al2O3 caused the SiO2 to gather around the Al2O3 particles. The present observations provided direct and visual evidence of SiO2 segregation at the grain boundaries (which had a deleterious effect on grain-boundary conductivity) and the scavenging of SiO2 via Al2O3 addition.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    Westerville, Ohio : American Ceramics Society
    Journal of the American Ceramic Society 83 (2000), S. 0 
    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 carbonate precursor of yttrium aluminum garnet (YAG) with an approximate composition of NH4AlY0.6(CO3)1.9(OH)2·0.9H2O was synthesized via a coprecipitation method from a mixed solution of ammonium aluminum sulfate and yttrium nitrate, using ammonium hydrogen carbonate as the precipitant. The precursor precipitate was characterized using chemical analysis, differential thermal analysis/thermogravimetry, X-ray diffractometry, and scanning electron microscopy. The sinterability of the YAG powders was evaluated by sintering at a constant rate of heating in air and vacuum sintering. The results showed that the precursor completely transforms to YAG at ∼1000°C via the formation of a yttrium aluminate perovskite (YAP) phase. YAG powders obtained by calcining the precursor at temperatures of ≤1200°C were highly sinterable and could be densified to transparency under vacuum at 1700°C in 1 h without additives.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    Westerville, Ohio : American Ceramics Society
    Journal of the American Ceramic Society 84 (2001), S. 0 
    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: Positive temperature coefficient of resistivity (PTCR) was attained in heavily niobium-doped BaTiO3 through the addition of BaTiO3 seed particles. The seed particles containing a double twin grew during heat treatment, and a uniform microstructure composed of large, coarse grains was obtained. The incorporation of niobium into the grain via grain growth probably caused the semiconducting and PTCR character of the niobium-doped BaTiO3.
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    Westerville, Ohio : American Ceramics Society
    Journal of the American Ceramic Society 84 (2001), S. 0 
    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 grain-boundary conductivity (ςgb) of 8-mol%-ytterbia-stabilized zirconia increased markedly with heat treatment between 1000° and 1300°C with a slow heating rate (0.1°C/min) before sintering. The extent of the ςgb improvement was the same or larger than that via Al2O3 addition. The heat treatment did not affect the grain-interior conduction when sintered at 1600°C, while Al2O3-derived scavenging significantly did, given the larger increment of total conductivity in the heat-treated sample. The formation of a silicon-containing phase in a discrete form was suggested as a possible route of scavenging the resistive phase from the correlation between average grain size and ςgb.
    Type of Medium: Electronic Resource
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