Glass microspheres or microballoons are hollow spheres of glass, with a diameter of the order of one micrometer. They are used as a lightweight filler in composite materials such as syntactic foam. Microballoons give syntactic foam its light weight, low thermal conductivity, and a resistance to compressive stress that far exceeds that of other foams [1]. These properties are exploited in the hulls of submersibles and deep-sea oil drilling equipment, where other types of foam would implode.
Glass microspheres can be made by heating tiny droplets of dissolved water glass in a process known as ultrasonic spray pyrolysis, and properties can be improved somewhat by using an acid treatment to remove some of the sodium [2].
References
- Syntactic foam properties & applications
- Microballoon synthesis & thermal properties.
