Effect of additives on the microstructure of porous alumina

Protein forming, a direct consolidation technique for shaping of powders into a rigid body, use globular protein as gelling agent, which makes the process environment friendly. The present paper combines foaming and gelling capabilities of globular protein (albumin) along with starch to consolidate the ceramic bodies to develop porous structure based on alumina. The effect of albumin and starch on the gel strength, rheological properties of alumina slurry as well as the microstructure of final structure were studied in detail. It has been observed, that albumin which gels by forming strong polymer network dominates the gel properties, and thereby the strength of the consolidated green bodies, whereas starch, being insoluble in water at room temperature, increases the viscosity of slurry, but increases stability of foamed slurry. Also starch acts as pore former to introduce connectivity between pores and hence increases open porosity. Hence, by controlling albumin and starch ratio in the slurry one can control the microstructural developments in the cast body to obtain the desired micro-structure.