Microstructure of ceramic foams

Abstract

This paper describes the preparation of ceramic foams by expansion of a ceramic suspension based on a polyurethane system. The microstructure and degree of reticulation of the foamed ceramic were examined and analysed with the help of a simple geometrical model. Like the porous ceramics prepared by the replica processing method, these foamed ceramics possess open cells in a nearly equiaxed shape but the cell size is much ®ner. The ratio of the window size to the cell size is a useful parameter for characterising the geometry of the foam and is related to the qualitative concept of degree of reticulation. For a face centred cubic array of cells it is related geometrically to the volume fraction of porosity and this relationship is tested using microstructural measurements for a range of ceramic foams. #

Bi-continuous metal matrix composites

“…As claimed by the supplier, the ceramic foam possesses a uniform distribution of cells and the struts are sintered to full density. As observed in previous studies [20,22], these foams are prepared from finer powders which sinter well. fraction of 77.1% possesses small windows and that some cells are closed.…”

“…1b. As illustrated before [20], the ceramic foam prepared here possesses porous struts which allow the liquid phase to penetrate not just the foam cells, but the pores in the framework too. The cell size and window size were measured and are given in Table 1.…”

“…The details have been described elsewhere [20]. The ceramic powder selected was Alcan MA130 alumina with a mean diameter of 4 mm, donated by Alcan Chemicals, Gerrards Cross, UK.…”

“…The principal difficulty is controllably producing the desired connectivity and spatial distribution of the phases for a given volume fraction, especially on a fine scale. However, recent studies [20,22] of fine ceramic foams prepared from a polyurethane suspension of ceramic particles demonstrate that fine ceramic foam with controlled microstructure can be made.…”

Effects of ultrasound on polymeric foam porosity

“…Nearly all manufactured foams have homogeneous cellular structures to ensure uniform mechanical properties, so although the need for heterogeneous cellular materials has been widely recognised [4][5][6], there are few viable manufacturing processes for production of such materials [7].…”