Characterization of microstructure and properties of porous ceramics made by extrusion

Extrusion is a widely employed technique in industry to fabricate ceramic objects. Successful extrusion relies on proper formulation and processing conditions. In this work, the paste consists of dispersed alumina and kaolin particles in deionized water with hydroxypropyl methylcellulose (HPMC) and glycerol as processing aids. Extrusion was performed using a horizontal single screw extruder. The influence of the amount of binder and the volumetric ratio of alumina to kaolin, as well as sintering conditions on the microstructure and properties of the porous discs were investigated. The products were examined for its porosity, pore size distribution, specific permeability, and flexural strength, where the latter two properties were further related to their porous characteristics. Comparison was then made between extruded samples and dry pressed ones from our previous work for their similarities and differences. Our results indicated that the current extrusion process is very satisfactory in producing uniform microstructure and desirable properties for future application as support of membranes.