engleski

Preparation of Alumina Foams by the Polyurethane Sponge Replica Method

In this study, highly porous alumina ceramics with an open, three- dimensional network structure were prepared by a simple and low- cost replica method. This method involves the impregnation o a polymeric sponge (typically polyurethane) with a ceramic suspension followed by a heat treatment to burn out the polymeric template. Two different types of commercial polyurethane sponge with pore density of 18 ppi (pores per inch) and 30 ppi were used as the templates. These templates were repeatedly immersed in stable aqueous alumina suspension containing 60 wt. % solid with different additives to obtain uniform and sufficiently thick coating on the sponge struts and to prevent collapse of the ceramic structure during a two-stage sintering at 1600 °C. Factors that predominately affect the uniformity of the coating are the impregnating suspension rheological properties and its adhesion at the polymeric sponge. Therefore, the rheology of aqueous alumina suspension was analysed prior to impregnation. The resulting alumina foams were characterised on properties such as density, porosity, morphological features and compressive strength. It was found that total porosity of alumina foams decreased with increasing pore density of the polyurethane templates which consequently led to the increase of the compressive strength of ceramic foams. The results show that prepared stable ceramic suspension on behalf of above mentioned simple fabrication procedure are suitable for producing highly porous alumina foams.

alumina foam, porous alumina, replica method, ceramic suspension

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