CONICET | Buscador de Institutos y Recursos Humanos

Two shaping routes alternative to conventional processing by starch direct consolidation, called Mixing Route (MR) and Soluble Route (SLR), were proposed to develop porous bodies with homogeneous microstructures and adequate mechanical properties. Both routes were proposed to increase the aqueous mullite/starch suspension viscosity, and thus, to prevent particles segregation observed in bodies prepared by conventional route. In MR, a mixture of ungelatinized native starch and 2.5 vol.% of the total solid loading of gelatinized native starch was used by preparing the aqueous mullite/starch suspension, while in SLR, 2.5 vol.% of the total solid loading of starch was a granular cold-water-soluble (GCWS was prepared by heating an aqueous native cassava starch suspension and a poliol). Stable aqueous mullite (Baikowski, MULS)/starch suspensions (0.25 starch volume fraction of 40 vol.% total solids) were prepared by mixing and homogenization. Shear flow properties of the MR and SLR suspensions were analyzed from viscosity measurements. Disks were formed by heating (80 °C, 2 h) the aqueous mullite/starch suspensions into metallic molds and by drying (40 °C, 24 h). Green bodies shaped by both routes and obtained before (MRbb and SLRbb) and after (MRab and SLRab) burning out the starch, were characterized by bulk density and apparent porosity measurements, and microstructural analysis by SEM. The use of both routes allowed the development of green bodies without defects and surface deformation, and with homogeneous porous microstructures, which indicated that the segregation of raw materials was resolved. Moreover, the forming of mullite bodies did not require the addition of others binders beside starch to increase the suspension viscosity. The problems that could arise due to the competition by superficial adsorption sites and rheological behaviour changes of suspensions that should be evaluated were avoided.