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 similar to 30 mu m 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.