Extrusion of alumina and cordierite-based tubes containing Al-rich anodising sludge

An Al-rich anodising sludge has been used as the feedstock to produce alumina and cordierite-based tubes produced by extrusion. The extrudability is strongly dependent on the materials composition and on the resultant plasticity of the pastes. For the process to be successful, the design and operating conditions need to be considered in detail.In this work, the effect of die design, ram speed and pressure was evaluated using the Benbow–Bridgwater model of paste extrusion. In general, predicted and measured values were in good agreement. This approach revealed differences in the flow between the two ceramic formulations and it was possible to relate the rheological observations during extrusion to the quality of the final product.