Published online by Cambridge University Press: 15 February 2011
Sol-gel derived ceramic bubbles include shaped and fired, porous or impermeable nonvitreous ceramic microcapsules of metal oxide and non-oxide, are made by non-melt process involving the equilibrium boiling point method with controlled thermal gelation. Discrete, free-flowing, ceramic microbubbles consist of a non-oxide component and/or an oxide component having diameters in the range of I to 300 micrometers and each having a wall thickness of less than 10 percent of the diameter of the bubble. In this process, a sol precursor and a bloating agent, when added to a bubble promoting medium under proper conditions, provide green gelled microbubbles which after firing are strong, well formed, ceramic microbubbles. The microbubbles are non-vitreous, sol-gel derived, fine microstructured, uniform, hollow, smooth, and are essentially all oxide or non-oxide or combinations of both. The microbubbles can be used as fillers for metal, glass, ceramic, and polymer or filled with a selected solid, liquid or gas for purpose of storing, transporting, or facilitating the use of the same.