Predicting processing-sintering-related properties of mullite–alumina ceramic bodies based on Al-rich anodising sludge by impedance spectroscopy

Al-rich sludge produced from industrial anodising and surface treatment processes has been tested in the fabrication of mullite/alumina-based refractory/electrical insulating materials, by dry pressing and extrusion. Different compositions were prepared by using sub-products or common natural silica-containing materials, like ball clay, kaolin and/or diatomite. Ultimate properties are dependent on the shaping method and sintering schedule, since both steps strongly affect the microstructural evolution and crystalline phase formation, which in turn determine the performance of the sintered bodies. The response of sintered bodies to impedance spectroscopy was studied and revealed interesting microstructure–electrical relationships, enabling the use of this technique to predict the processing-sintering-related properties.