Processing of cellular ceramics by foaming and in situ polymerisation of organic monomers

This paper describes studies on a new processing route for fabricating high ly porous ceramics. The method is based on the generation of a foam from an aqueous suspension of ceramic powder and the subsequent stabilisation of t he structure by in situ polymerisation of organic monomers. The influence o f the slip viscosity on the foam volume and stability was determined wing c oncentrated alumina suspensions containing dispersing agents and two commer cial foaming agents. The in situ polymerisation of organic monomers led to fast solidification, resulting in strong, porous bodies which could withsta nd machining. The resulting ceramic foams consisted of a highly interconnec ted network of spherical cells with densities as low as 6% of theoretical. The distribution of cell size was dependent both on the density of the spec imen produced and on the time for polymerisation onset. The size ranged fro m approximately 30 to 600 mu m. Enlargement of cell size to achieve materia ls of higher permeability was possible through expansion of the foam via pr essure reduction before polymerisation. The creation of highly densified st ruts between the cells led to flexural strengths as high as 26 MPa. (C) 199 9 Elsevier Science Limited All rights reserved.