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PRODUCTION AND CHARACTERIZATION OF ZIRCONIA CERAMICS AND ZRO2-TIN COMPOSITES In this study, yttria and yttria-ceria stabilized tetragonal zirconia ceramics with varying stabiliser content and distributionand with Al2O3 were prepared and investigated by means of microstructural analysis, mechanical properties, and hydrothermal stability, and ZrO2-TiN composites with of electrical conductive TiN particles were developed by adding different stabilizers. Fully dense Y-TZP ceramics, were achieved by hot pressing at 1450°C for 1 hour and fully dense Y-Ce-TZP ceramics were achieved by pressureless sintering at 1450°C for 1 hour. For both yttria coating and co-precipitated tecniques, the toughness increased whereas the hardness decreased when decreasing the overall yttria content from 2.5 to 2.0 mol %. Hydrothermal testing revealed that the stability of the yttria-coated powder based grades is higher than that obtained by powder mixing. Moreover, the hydrothermal stability increased with increasing overall yttria content, what actually corresponds with a decreasing fracture toughness. Fully dense ZrO2-TiN composites with TiN content ranging from 40-70 vol % were achieved by hot pressing at 1550°C for 1 hour and spark plasma sintering for 4 minutes. The hardness and fracture toughness were influenced by TiN content, sintering techniques and stabilizer content. The decreasing hardness and strength was attributed to an increasing TiN grain size with increasing TiN content, whereas the decreasing toughness was attributed to the decreasing contribution of transformation toughening from the tetragonal to monoclinic ZrO2 phase transformation. The E modulus increased linearly with increasing TiN content, whereas the hydrothermal stability increased with addition of TiN content. |
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