Investigations of reticulated porous alumina foam ceramics based on different coating techniques with the aid of μCT and statistical characteristics

Alumina foam ceramic filters were prepared due to 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 additives for the slurry for the impregnation (first coating) step were investigated with the aid of rheological measurements. For the second coating step spraying as well as centrifuging techniques with different processing parameters were studied. The sintered foam structure (strut diameter, pore size and porosity) was characterized with the aid of CT-images and described with an image analysis software and statistical tools. The mechanical properties depend strongly on the achieved 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 a pressure supported dipping as well as optimum processing parameters of the spraying step led to improved mechanical properties as well as homogenous macro-structures.