Control of pore and window size of ceramic foams with tri-modal pore structure: Influence of agar concentration

• Ceramic foams with tri-modal pores are prepared via foaming and agar gelation.
• Agar concentration significantly influences gelation rate of slurry.
• Control of pore structure of ceramic foams is feasible by agar concentration.

The present study relates to manufacturing of highly porous ceramics having a hierarchical tri-modal pore structure via foaming and agar gelation. Formations of macropores caused by foaming, window pores that pores are connected each other, and micropores caused by agar were confirmed through the present study. The amount of agar addition significantly influenced the rheological behavior of slurry, which consequently affected physical properties of final products. Though total, open, and closed porosity was not sensitive to agar contents added, microporosity and specific surface area increased and average pore and window (i.e., a pore generated by contact of macropores) size decreased with increasing agar contents, respectively. Additionally, ceramic foams prepared with higher agar contents exhibited more uniform pore size (i.e., lower uniformity factor). Gelation rate, which was sensitive to the amount of agar and controlling bubble stabilization rate, was found to be a critical factor affecting physical properties of ceramic foams. The results suggest that the control of pore structure of ceramic foams is feasible by adjusting the level of agar contents.