Synthesis of porous ceramics by spray-dried granules sintering

The aim of this research is to develop a new route for manufacturing macroporous ceramics characterized by a highly interconnected porosity. Such porous materials could find applications in the fields of fluid transfer / mixing, catalysis or filtration. The process must be sufficiently versatile in order to tailor on purpose: i)- the porosity fraction within a large range (typically 30 to 80 %); ii)- the pore size and distribution (single or multimode)
The originality of this work is to consolidate, by sintering, package of ceramics granules obtained by spray drying. The sintering must promote the bridging of granules (at the points of contact between them) by neck growth with a limited densification for leaving high porosity. The porous structure that may result of this process is the negative image than that resulting of sacrificial methods using organic beads.
The investigation of the feasibility was performed with an alumina spray dried powder. At first, the pressure effect on the compact of granules density was studied. The consolidation of the compact is possible at temperature of 1200°C during the sintering via the applied low pressure (about 1-2 MPa). The final porous structure can be tailored by modifying the temperature / pressure cycle. According to this cycle a single mode (intergranular) or dual mode (intergranular + transgranular) porosity with significantly different surface areas is obtained.