Fabrication of Highly Porous Mullite Materials

Porous mullite, formed by large spherical-shaped pores evenly distributed within a mullite matrix, was processed by a direct consolidation method based on the starch swelling properties. Materials with porosities up to 60 vol% and with an average pore size of ∼30 μm were prepared. Porosity matched the starch volume fraction for contents ≥45 vol%, while for lower contents the porosity was above the volume fraction of starch. Formation of crack like defects either surrounding or connecting pores occurred during the drying–sintering processes in the high starch content mullite.