Evaluation of SiC sintering via liquid phase using as additive the systems TiO2/Al2O3 and TiO2/Y2O3

Reference Presenter Authors
(Institution)
Abstract
14-044 Marcela Rego Oliveira Oliveira, M.R.(Escola de Engenharia de Lorena); Ribeiro, S.(Escola de Engenharia de Lorena); The objective of this work was to study SiC sintering via liquid phase using the TiO2 / Al2O3 and TiO2 / Y2O3 as additive systems, with 10% volume, called STA and STY, respectively. The powders were mixed, dried, deagglomerated and compacted in a uniaxial and isostatic press. The samples were sintered at 1850 and 1950ºC, with rates of 5 and 20ºC/min and times of 30 and 60 minutes. Analyzes of mercury porosimetry, X - ray diffraction, modulus of elasticity and fracture toughness were performed. For the STA system at 1950ºC, at a rate of 20ºC/min for 30 minutes, a maximum sample densification of 93% was obtained. For the STY system, more porous ceramics were obtained, with a maximum densification of 70%, also sintered at 1950 ºC, at 5ºC/min and 30 minutes. These results indicate a better interaction of SiC with the TiO2/Al2O3 additive, as a lower contact angle. In general, lower rate and longer time, generated more porous samples, in both systems of additives, by possible reactions, resulting in loss of mass during the sintering. In both systems of additives there was the phase transformation of the ?-SiC to the ?-SiC, and formation of the phase Al2TiO5 and Ti2Y2O7, for the systems STA and STY, respectively, in all the cycles of sintering. The denser samples of STA have modulus of elasticity of 330 GPa and KIc of 3.4 MPa.m1/2. For the STY system, values of 193 GPa and 1,5 MPa. m1/2 were obtained. The results showed that for obtaining a dense SiC ceramic, the TiO2/Al2O3 additives system, sintered at 1950ºC, should be used, where there is a good surface interaction between the SiC and the additive. The TiO2/Y2O3 additive system should be used for the production of more porous ceramics.
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