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

L. SANDOVAL ; M.A. CAMERUCCI; A.G. TOMBA MARTINEZ

JOURNAL OF MATERIALS SCIENCE

SPRINGER

Lugar: Berlin; Año: 2012 vol. 47 p. 8013 - 8021

0022-2461

In this study, the high-temperature mechanical response of a cordierite-based porous material prepared bydirect starch consolidation was evaluated. Disks were prepared by the thermogelation (85 C, 4 h) of an aqueoussuspension (29.6 vol. %) of a cordierite precursor mixture (talc, kaolin, and alumina) with the addition of a commercial modified cassava starch (11.7 vol.%), drying (50 C, 24 h), firing (650 C, 2 h), and reaction sintering (1330 C, 4 h). The porous microstructures were characterized by Archimedes method (bulk density and apparent porosity measurements), SEM with image analysis (pore cavity sizes), and mercury porosimetry (pore throat sizes). Mechanical behavior was evaluated in diametral compression using a servohydraulic testing machine at room temperature, 800, 1000, and 1100 C. Apparent stress?strain relationships were obtained from load?displacement curves, and mechanical parameters, such as fracture strength (rF), fracture strain (eF), and apparent Young modulus (Ea) were determined. Moreover, crack patterns and fracture surface were also evaluated. The obtained results were analyzed as a function of the developed microstructures, considering the presence of a silicate glassy phase and a complex porosity, and the testing temperature. From these results, the operative fracture mechanism was proposed. Finally, the obtained results were compared with those reported by the authors for cordierite porous materials prepared using other types of native starches, determining that the best mechanical response, in particular at high temperature, was obtained using modified cassava starch.C, 4 h) of an aqueoussuspension (29.6 vol. %) of a cordierite precursor mixture (talc, kaolin, and alumina) with the addition of a commercial modified cassava starch (11.7 vol.%), drying (50 C, 24 h), firing (650 C, 2 h), and reaction sintering (1330 C, 4 h). The porous microstructures were characterized by Archimedes method (bulk density and apparent porosity measurements), SEM with image analysis (pore cavity sizes), and mercury porosimetry (pore throat sizes). Mechanical behavior was evaluated in diametral compression using a servohydraulic testing machine at room temperature, 800, 1000, and 1100 C. Apparent stress?strain relationships were obtained from load?displacement curves, and mechanical parameters, such as fracture strength (rF), fracture strain (eF), and apparent Young modulus (Ea) were determined. Moreover, crack patterns and fracture surface were also evaluated. The obtained results were analyzed as a function of the developed microstructures, considering the presence of a silicate glassy phase and a complex porosity, and the testing temperature. From these results, the operative fracture mechanism was proposed. Finally, the obtained results were compared with those reported by the authors for cordierite porous materials prepared using other types of native starches, determining that the best mechanical response, in particular at high temperature, was obtained using modified cassava starch.