Departamento de Ciencias Naturales

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https://hdl.handle.net/20.500.12590/17953

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Browsing Departamento de Ciencias Naturales by Author "Huamán Mamani, Fredy"

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    Compressive creep behavior of zirconia/nickel oxide composites
    (International Committee on Composite Materials, 2017) Huamán Mamani, Fredy; Jiménez Melendo, Manuel
    Nickel oxide/zirconia composites with different NiO contensts have been fabricated by mechanical mixing of nickel oxide and zirconia powders and sintering at 1500 ºC for 10 h in air. The resulting microstructures have been characterized by scanning and transmission electron microscopy. The mechanical behaviour of the composites has been characterized by compressive tests at high temperatures between 1100 and 1350 ºC. For NiO contents above the percolation limit, the softer phase was found to be rate-controlling in oxidizing atmospheres, achieving extended steady states of deformation without macroscopic failure. By contrast, the overall creep strength of the composites decreased severely in reducing conditions. © 2017 International Committee on Composite Materials. All rights reserved.
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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.