Processing and Properties of Porous Al₂O₃ by Slurry Foaming Combined with Gelcasting

Porous ceramics are essential for a variety of technical applications such as thermal insulators, filters, catalyst supports, gas sensors, bone graft substitutes, etc. Of numerous processing methods, the slurry foaming method is advantageous in producing porous ceramics with a cellular structure with high degrees of shape complexity and control of pore size and connectivity. It combines foaming and setting of a ceramic slurry. The gelcasting employing in situ polymerization of organic monomers is superior to other setting methods utilizing thermal gelation of agar, carrageenan, gelatine, starch, or egg white in green strength and machinability. Previously unusual acrylic (or acrylate) monomer was used to produce porous Al2O3 and hydroxyapatite. In the present work, porous Al2O3 was prepared by the slurry foaming method with acrylamide monomer, commonly used in gelcasting for producing dense ceramics. The foaming and gelation behavior was investigated with the parameters such as the type and concentration of surfactant (i.e. foaming agent), solid loading, and the concentrations of initiator and catalyst. The density, porosity, microstructure, and strength of the resulting samples were characterized.