A moditied model for alumina membranes formed by gel-casting followed by dip-coating

alpha-Al2O3 membrane coating (top layer) was formed by dip-coating and investigated based on full factorial design of experiments. Statistical analysis showed that the effects of two variables; dipping time and withdrawal speed of the substrate, were highly significant in determining the thickness of the top layers (alpha < 0.001). A modified model was developed to interpret quantitatively the formation process of the top layers onto the porous substrate during dip-coating. In this model, the effects of all variables affecting the top layer thickness were considered simultaneously. The experimental data corresponding to alpha-Al2O3 membranes obtained from suspensions with different volume fractions of ceramic powder showed good agreement with the model. The root mean square deviation was less than 0.02. (C) 2004 Elsevier Ltd. All rights reserved.