Shaping of mullite green foams by protein thermogelling process

M.L. SANDOVAL; M.A. CAMERUCCI

Portland

Conferencia; 12th International Conference on Ceramic Processing Science; 2013

The direct thermal consolidation by gelling of aqueous ceramic suspensions foamed with globular proteins is an innovative colloidal processing, non-contaminant, used to fabricate porous ceramics. Stable aqueous mullite-albumin (5, 10, 15vol.%) suspensions were foamed by mechanical stirring at 2300 rpm, 10min at room temperature (conventional route, Rc). In order to increase the suspension viscosity, decrease the foam desestabilization before gelling process and minimize the particle segregation, the adding of methylcellulose (2wt.%) as an additional binder on the foaming of the suspensions was evaluated (MC route, RcMC). Rheological behavior of suspensions, foamed and without foamed, as a function of temperature was also analyzed. Mullite green disks were prepared by pouring the foamed suspensions into warm metallic molds, heating at 80°C, 2h and drying at 50°C, 24h. Green foams were characterized by relative density and porosity measurements, and microstructural analysis by SEM on the fracture surface. Cell size distributions and cell morphology were analyzed in relation to wet foam properties. Disks prepared by Rc achieved the highest porosities (72%) and lowest relative densities (0.28). The porous homogeneity and size (85-130µm) depended on the protein content. Disks prepared by RcMC showed microstructures more homogeneous independently of the albumin amount with smaller cells (30-45µm) and denser struts