Processing of porous ceramics by 'starch consolidation'

A new consolidation method for forming porous ceramics was developed using stal ch as both consolidator/binder and pore former. Simple and complex-shaped components of porous alumina were shaped and demoulded in wet state. After drying, burn-out and sintering, materials with ultimate porosities between 23 and 70% were obtained. The overall pore structures were dominated by the large spherically shaped pores (10-80 mu m) left by the starch particles. Furthermore, the average size of the small pores connecting the large por es, measured by Hg porosimetry, was controlled by the total solids lending and starch content in the originally prepared slips and varied between 0.5 and 9.5 mu m. Chemically modified starch was found to give better dimensional control and regularity regarding average size of the connecting pores than native starch owing to more stable properties during water processing. This new forming technique can be used in the manufacture of various porous ceramics for thermal insulation applications, as filters/membranes and gas burners, or as bioceramics. Major advantages are the simplicity of the process, the possibilities of forming complex shapes using various mould materials and the low-cost processing equipment/materials needed. (C) 1997 Elsevier Science Limited.