2.1 Replica Technique
The replica method is based on the impregnation of a cellular structure (sponge) with a
ceramic suspension. The organic structure is than removed by controlled thermal treatments
in order to produce a macroporous ceramic exhibiting the same morphology of the original
porous material. Many synthetic and natural sponges can be used as templates for this
method.
Porous ceramics obtained with the sponge replica method can generally reach total open
porosity levels within the range 40%–95% and are characterized by a reticulated structure of
highly interconnected pores with sizes between 200 μm and 3 mm. The minimum cell size of
replica-derived porous ceramics is however limited to approximately 200 μm, for the
difficulty of impregnating polymeric sponges with excessively narrow cells.
2.2 Sacrificial Template Method
The sacrificial template technique usually consists on the preparation of a biphasic
composite comprising a continuous matrix of ceramic particles and a dispersed sacrificial
phase. The latter is initially homogeneously distributed throughout the matrix and is
ultimately extracted to generate pores within the microstructure. Predominantly open pores
of various different morphologies can be produced with this method. The most crucial step
in this technique is the removal of the sacrificial phase that can be done by pyrolysis,
evaporation, or sublimation. These processes might involve the release of an excessive