The stabilization of wet foam is very important to avoid the instability caused by the large interfacial area at gas-liquid interface of colloid suspension. Propionic acid, a short chain carboxylic acid is used as foam stabilizer, which acts by modifying the particle surface and increases the wet foam stability. The characterization of Al2O3-SiO2 foams, namely Laplace pressure, foam stability, air content and bubble size are explored by changing the concentration of the amphiphile. Macroporous Al2O3- SiO2 ceramics with open or closed cells, average pore size of less than 100 μm and porosities within 43 and 51% was prepared by direct foaming process. The sample sintered at 1300 oC for 1 hour showed an adsorption free energy of 0.9 × 107 to 2.0 × 108 kTs and a Laplace pressure of 0.63 to 0.85 mPa, highlighting good wet foam stability of approximately 80-90%.

Keywords: Porous ceramics, Direct foaming, Wet foam stability, Carboxylic acid, Laplace pressure, Adsorption free energy.