Thermogelling polysaccharides for aqueous gelcasting -: part III:: mechanical and microstructural characterization of green alumina bodies

The use of gelling additives, such as polysaccharides, in colloidal processing provides adequate mechanical properties to the green bodies to be handled. In this work, the green density and the mechanical behaviour (stress-strain relationships, elastic modulus, bend strength and fracture mechanism) at room temperature of gelcast alumina bodies are studied, in order to establish the influence of the type and the concentration of additive. Furthermore, the previous concentration of polysaccharide solutions is also taken into account as an important variable. Agar, agarose and carrageenan were used as gelling additives. Values of the bend strength up to 4 MPa are obtained, significantly higher than those corresponding to slip cast alumina without gelling additives, and they increase with the final concentration of polysaccharide, while Young's modulus values are mainly influenced by the concentration of additive in the precursor solution. For bodies with a large final concentration of additive, extensive plastic deformation during fracture is observed. (C) 2002 Elsevier Science Ltd. All rights reserved.