Mechanical evaluation of cordierite precursor green bodies obtained by starch thermogelling

Abstract

The mechanical behavior of green bodies (porous cordierite precursors) obtained from suspensions of kaolin, talc and alumina powders consolidated by starch thermogelling was studied. Different starches were employed as consolidator/binders: potato, cassava, corn or modified cassava. Aqueous suspensions of the powders (29.6 vol.%) with 11.7 vol.% of starches were prepared by intensive mechanical mixing, homogenization and vacuum degasification. Disks were prepared by thermogelling the suspensions for 4 h at 75–85 °C and additional drying. Green bodies were characterized by bulk density and apparent porosity measurements and microstructural analysis by SEM/EDAX. The mechanical evaluation was carried out by diametral compression in displacement control. Apparent stress–strain relations were obtained from load–displacement curves and several mechanical parameters were determined: mechanical strength, apparent Young modulus and yield stress. Crack patterns were analyzed together with fractographic analysis by SEM. Mechanical results were related to the behavior of the starches in aqueous suspension and the properties of the formed gels.