Low-temperature preparation of alumina-mullite porous ceramic via gelation-assisted dual-phasic nanoparticle stabilized foams

Abstract

Preparation of ultralight ceramic foams via aqueous-based direct foaming method for practical application is a challenging task owing to Ostwald ripening of wet foam and unsatisfied mechanical strength of final products. To tackle these issues, the current work demonstrates the construction of alumina-mullite ceramic foams via gelation-assisted dual-phasic nanoparticle stabilized foams using boehmite sol and nanosilica as the raw materials. The gelation process of boehmite sol inhibits the Ostwald ripening and pore enlargement during drying. The highly active alumina powder derived from boehmite sol and nanosilica enables the reaction by forming mullite at 1200°C. Consequently, the resultant products demonstrate a compressive of 3.9 MPa at a porosity level of 95.9%, a bulk density of 0.18 g/cm3 and an ultralow thermal conductivity of 0.1043 W·m-1·K-1 after firing at 1200°C. The current strategy provides new insight for fabricating high-performance ceramic foams for multiple applications.