Processing of porous alumina substrate for multilayered ceramic filter

The present paper reports results of an initial study related to the fabrication of multilayered ceramic filters with a gradient in porosity for efficient cleaning of liquid medium containing undesired particles/impurities. This study involves the fabrication of a porous ceramic substrate to support the intermediate and top layers. The choice of the support material and its properties in terms of porosity, pore distribution and structural quality are critical for effective performance of the multilayered filter. These properties need to be optimized to achieve proper integration of intermediate layer onto the support structure and to eliminate disturbances in the flow at the interface of the support and intermediate layer. Different ceramic materials including a-alumina, zirconia, and SiO₂ or a combination of these materials with a range of initial particle sizes are being studied for their suitability as support structures, although only results related to a-alumina are presented in this work. Disc shaped ceramic supports were fabricated by uni-axial compaction of powders followed by sintering in a tube furnace in air atmosphere. The effect of compacting pressure on the green density of the ceramic compacts was evaluated. After sintering at 1400°C for 2 h, the fabricated a-alumina ceramic support was characterized using X-ray diffraction, scanning electron microscopy and mercury porosimetry techniques to determine the nature of phases formed, crystallinity, morphology, pore size and pore size distribution. The structural integrity/strength of the substrate was measured using diametral compression test.