Structure and thermal properties of millimeter-scale alumina aerogel beads formed by a modified ball dropping method

We report the formation of millimeter-sized alumina aerogel beads with a modified ball dropping method, in which alumina alcogel beads are formed by extruding an alumina sol containing a small amount of polyvinyl alcohol (PVA) through nozzles into ammonia water, followed by supercritical drying. The resultant millimeter-sized alumina aerogel beads with the diameter ranging between 1-4 mm have an average pore size of 12-14 nm and specific surface area of 500-600 m 2 g −1 . They transform from γ-AlO 2 H phase to γ-Al 2 O 3 phase at 400 °C, which remains stable even when the temperature reaches 1200 °C. We report the formation of alumina aerogel beads with a modified ball dropping method, in which alumina alcogel beads are formed by extruding alumina sol containing a small amount of polyvinyl alcohol through nozzles into ammonia water.