Crack‐Free Drying of Ceramic Foams by the Use of Viscous Cosolvents

Ceramic foams are being used in numerous industrial applications such as high-temperature thermal insulation, hot gas particulate filters, molten metal filters, catalyst support, and cores in high- temperature structural panels. The growing usage ceramic foams stems from the favorable properties such as low density, low thermal conductivity, and from their thermal and chemical stability. Recently Gauckler and colleagues developed a new method to produce ceramic foams. This method involves introducing gas bubbles into highly concentrated colloidal suspensions. The foam structure is stabilized by the suspended particles which align at the liquid/gas interface. Following the foaming stage, the wet green foams are dried and sintered. We have found that when making large foam bodies (i.e., > 100 mm), cracks formation during the drying stage became a major issue. Following the rational of Scherer and Brinker in the drying of gels, we propose a model that explains the cracks formation in the foams and suggest a different procedure for successful drying of this system. Our solution is based on the addition of miscible cosolvents with low volatility to the aqueous phase. In this paper, we present the effectivity of different cosolvents in solving the cracking problems of large objects.