Red clay-based porous ceramic with pores created by yeast-based foaming technique

Red clay-based porous ceramic has been fabricated by using a biological foaming technique through reaction of yeast with starch in aqueous ceramic suspension. The starch plays a dual role as a growth substrate for gas bubble generation and a binder for ceramic particles. Starch-loaded ceramic slurries (55 wt% ceramic solid) were prepared, consisting of red clay, quartz, feldspar, and starch. Three types of starches were used, namely, cassava starch, corn starch, and rice flour. The rheological characterization of starch-loaded ceramic slurries showed shear thinning behavior. This resulted into a high foaming factor depending on the types of starches loaded and increased addition of yeast. Total fired porosities obtained were between 17 and 70%. These correspond to open porosities between 15% and 50%, and close porosities range from 6% to 35%. Microstructural investigation of the fired porous compacts showed irregular pore morphologies equipped with interconnecting channels that represent the open porosity.