Processamento e caracterização física e mecânica de cerâmicas de zircônia-ítria total e parcialmente nanoestruturadas / Physical and mechanical characterization of total and partially nanostructured zirconia-yttria ceramics

AUTOR(ES)
DATA DE PUBLICAÇÃO

2007

RESUMO

In this work the behavior of nanostructured and partially nanostructured zirconia-yttria ceramics is analyzed during the compacting and sintering processes. The evaluation of the mechanical properties (flexure strength, fracture toughness and hardness) also is presented. They were studied two groups: one composed by a microparticulate powder obtained through chemical chloride coprecipitation (MICRO-cloretos) that was mixed with a commercial nanoparticulate powder (ZYNC), and another one composed by the same MICRO-cloretos powder mixed with a powder synthesized by Pechini method (PECH). All of the powders were stabilized with 3 mol% of Y2O3 and the X-ray diffractions patterns showed the majority presence of the tetragonal phase of the zirconia. SEM analyses and particle size distribution showed that the MICRO-cloretos powder is formed by particles and agglomerates in the micrometric scale, while the ZYNC powder presented agglomerated particles with the majority sizes below 300 nm. The PECH powder presented particles with the equivalent diameters smaller than the ZYNC powder, in spite of their curves of particle size distributions be similar. The mixtures of the two powder groups were accomplished in a centrifugal ball mill with different mass concentrations of nano and microparticulate powder. The powder mixtures behavior of the ZYNC/MICRO-cloretos group in the compaction curves and in the dilatometry analysis showed to be dependent of the amount of nanoparticulate powder incorporate to the mixture, increasing the green density, and consequently the final density of the ceramic, as the content of the ZYNC powder is increased. The combination of 80 % of ZYNC nanoparticulate powder with 20 % of MICRO-cloretos powder resulted in the highest measurements in mechanical properties characterizations, with values of 404 MPa in the flexure strength, 12 GPa in the Vickers hardness and 4.29 MPa.m1/2 in the fracture toughness. The prepared mixtures starting from the PECH/MICRO-cloretos powders presented a small improvement during compaction in relation to the totally microparticulate powder, not being significant the difference among the behavior of the compaction curves of the mixtures, in spite of the different amount of PECH powder present in each mixture. The PECH powder presented a low sinterability, caused by the state of aggregation of their particles. The residual porosity observed in the microstructures of the PECH ceramic and of their mixtures determined the low values obtained in the characterization of their mechanical properties.

ASSUNTO(S)

nanopartículas yttria-stabilized zirconia cerâmicas processing mechanical properties compactação propriedades mecânicas ceramics compaction zircônia estabilizada com ítria nanoparticles

ACESSO AO ARTIGO

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