High-temperature mechanical behavior of cordierite-based porous ceramics prepared by modified cassava starch thermogelation

Abstract

In this work, the high temperature mechanical response of a cordierite-basedporous material prepared by direct starch consolidation was evaluated. Disks wereprepared by the thermogelation (85 ¢XC, 4h) of an aqueous suspension (29.6 vol.%) of acordierite precursor mixture (talc, kaolin and alumina) with the addition of acommercial modified cassava starch (11.7 vol.%), drying (50 ¢XC, 24h), firing (650 ¢XC,2h) and reaction-sintering (1330 ¢XC, 4h). The porous microstructures were characterizedby Archimedes method (bulk density and apparent porosity measurements), SEM withimage analysis (pore cavity sizes) and mercury porosimetry (pore throat sizes).Mechanical behavior was evaluated in diametral compression using aservohydraulic testing machine at room temperature, 800, 1000 and 1100 ¢XC. Apparentstress-strain relationships were obtained from load-displacement curves, and mechanicalparameters, such as fracture strength (?ãF), fracture strain (?ÕF) and apparent Youngmodulus (Ea) were determined. Moreover, crack patterns and fracture surface were alsoevaluated. The obtained results were analyzed as a function of the developedmicrostructures, considering the presence of a silicate glassy phase and a complexporosity, and the testing temperature. From these results, the operative fracture mechanism was proposed. Finally, the obtained results were compared with thosereported by the authors for cordierite porous materials prepared using other types ofnative starches, determining that the best mechanical response, in particular at hightemperature, was obtained using modified cassava starch.