Manufacture of microporous ceramic layer by suspension-sedimentation for filtration applications

Microporous layers of 0.3mm a-alumina powder were deposited on the surface of porous zirconia substrates (average pore size of about 1mm) using suspension-sedimentation method. The characteristics of the deposited alumina microporous layer was evaluated using different types of dispersants, namely, citric acid, sodium dodecyl sulfate and Triton X-100. The effect of these dispersants on the stability and settling characteristics of alumina suspension was evaluated by sedimentation tests. Scanning electron microscopy analysis of the microporous layers (prior to sintering) revealed that sodium dodecyl sulfate dispersant produced uniform layers with least agglomeration of alumina particles, whereas citric acid showed more agglomeration of alumina particles and the use of Triton X-100 developed holes on the surface of alumina layer. The layers deposited using sodium dodecyl sulfate dispersant were then sintered at 1400 °C in air. Scanning electron microscopy observations revealed that a uniform porous alumina layer with average pore size in the range of 0.5-1.0 μm was produced with this method. The results of sedimentation tests indicated that alumina powder suspension prepared with sodium dodecyl sulfate dispersant yielded very good stability with lowest particle settling rate, whereas citric acid exhibited the highest particle settling rate.