Investigación - Departamento de Ciencias Naturales

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Browsing Investigación - Departamento de Ciencias Naturales by Subject "Alumina"

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    Creep properties of polycrystalline Al2O3 – Based ceramic composites
    (International Committee on Composite Materials, 2017) Huamán Mamani, Fredy; Jiménez Melendo, Manuel
    Three-phase Al2O3 - ZrO2 - Er2O3 composites with the ternary eutectic composition were fabricated by a conventional solid-state reaction route starting from commercial powders of alumina, erbia and monoclinic zirconia. Bulk composites with relative densities higher than 98% were obtained after calcining at 1400 ºC for 10 h in air and sintering at 1500 °C in air for 10 h. X-ray diffraction and energy-dispersive X-ray spectroscopy showed the presence of the three expected phases: alumina, EAG and zirconia. The composites exhibit a homogeneous microstructure with equiaxed grains of about 1 µm in size. Mechanical tests were carried out in compression at temperatures between 1300 – 1450 °C in air. Extended steady states of deformation were attained without macroscopic damage. The stress exponent in such experimental conditions was close to 2, suggesting that grain boundary sliding is the main deformation mechanism, as found in other fine-grained ceramics. © 2017 International Committee on Composite Materials. All rights reserved.
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    Fabrication and creep properties of eutectic-composition Al2O3/YAG/YSZ sintered composites
    (Elsevier Ltd, 2021) Huamán-Mamani, F.A.; Jiménez-Holgado, C.; Jiménez-Melendo, M.
    "Three-phase alumina/YAG/yttria-stabilized cubic zirconia (YSZ) composites were fabricated by a solid-state reaction route starting from commercial powders of Al2O3, Y2O3 and monoclinic ZrO2. The final phases Al2O3, YAG and YSZ were obtained after calcination of the powder mixtures at 1400 °C. Dense bulk composites were obtained after sintering, with a homogeneous microstructure of fine and equiaxed grains with sizes of 1 μm. Compressive mechanical tests were performed at 1300–1450 °C in air at constant load and at constant initial strain rate. A brittle-to-ductile transition was found with increasing temperature. Grain boundary sliding is the main deformation mechanism in the ductile regime, characterized by a stress exponent of 2 and by the absence of dislocation activity and changes in grain morphology. Alumina seems to be the rate-controlling phase owing to the improvement in creep resistance by the presence of yttrium and zirconium of the other two phases."