Continuous slurry foaming: a new method for manufacturing ceramic foams

Ceramic foams can be produced with different methods, where every method exhibits typical benefits and characteristic foam morphologies. The authors have been developing a new continuous direct foaming method that produces foam in a simple and continuous way. Thereby the foam is produced during the flow of the prepared slurry through static mixing elements, where the slurry is mixed with gas that is pressed through a porous membrane surrounding the static mixing elements. The wet foam is filled into molds, dried and sintered. The manufacturing as well as disproportionation processes of the foam in its wet state determine the resulting foam morphology that can exhibit closed or open cells with pore sizes between 50 micron and 5 mm and porosities up to 90 %. As a benefit in opposition to other foaming methods, this method allows the combination of the wet foam within another foam structure on a macroscopic level. These foams are termed hybrid foams.