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

Abstract

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 m² g⁻¹. They transform from γ-AlO₂H phase to γ-Al₂O₃ phase at 400 °C, which remains stable even when the temperature reaches 1200 °C.