INVESTIGATIONS OF RETICULATED POROUS ALUMINA FOAM CERAMICS BASED ON DIFFERENT COATING TECHNIQUES WITH THE AID OF MICRO-CT AND STATISTICAL CHARACTERISTICS

Alumina foam filters were prepared by the "replica technique". The parameters of the two coating steps were varied to find the optimal processing route to prepare ceramic foam filters with a good homogeneous distribution of the strut thickness. Different slurry additives for the impregnation (first coating) step were investigated with the aid of rheological measurements. For the second coating step, spraying and centrifuging techniques with different processing parameters were studied. The sintered foam structures (strut diameter, pore size and porosity) were characterised with the aid of computed tomography images and described using image analysis software and statistical tools. The mechanical properties depended on the structure of the filter and especially on the distribution of the strut thickness in the inner volume side of the filter. A centrifuging technique with pressure-supported dipping and optimum processing parameters of the spraying step led to improved mechanical properties and homogenous macro-structures.