A system was designed to produce hollow silica aerogel spheres by combining a droplet generation method with sol–gel processing. Simultaneous passage of an alkoxide solution and a fill gas, through a dual-nozzle system, formed a continuous stream of hollow droplets in the fluid state. The spherical droplets were levitated in a basic atmosphere containing ammonia which converted the sol into a rigid gel state. Supercritical drying was used for the elimination of residual solvents without shrinkage and cracking.

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