High-porosity replica foams with additional strut porosity were manufactured by a combination of sponge template coating and freeze casting processing. Several green foam series were obtained under variation of the type of thickening agent, concentration and/or the solid load of alumina within the coating slurry.
The total porosity was controlled with solid load: a decrease in alumina powder amount in the slurry lead to an increase in porosity. The lower limit of alumina load is ~ 20 vol. %; foams processed at this low amount were no more manageable.
Variations of the freeze casting parameters lead to a strut porosity of up to 40 % and the pores were in the range between 35 µm and 60 µm. Foams with a total porosity of 90 % were found to have a compression strength of at least 1.4 MPa.