PROCESSING OF POROUS CERAMICS BY STARCH CONSOLIDATION

A new consolidation method for forming porous ceramics was developed u sing stal ch as both consolidator/binder and pore former. Simple and c omplex-shaped components of porous alumina were shaped and demoulded i n wet state. After drying, burn-out and sintering, materials with ulti mate porosities between 23 and 70% were obtained. The overall pore str uctures 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 o riginally prepared slips and varied between 0.5 and 9.5 mu m. Chemical ly modified starch was found to give better dimensional control and re gularity regarding average size of the connecting pores than native st arch owing to more stable properties during water processing. This new forming technique can be used in the manufacture of various porous ce ramics for thermal insulation applications, as filters/membranes and g as 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 neede d. (C) 1997 Elsevier Science Limited.