Glass microspheres are microscopic spheres of glass manufactured for a wide variety of uses in research, medicine, consumer goods and various industries. Glass microspheres are usually between 1 to 1000 micrometers in diameter, although the sizes can range from 100 nanometers to 5 millimeters in diameter. Hollow glass microspheres, sometimes termed microballoons, or glass bubbles have diameters ranging from 10 to 300 micrometers.
Hollow spheres are used as a lightweight filler in composite materials such as syntactic foam and lightweight concrete.[1] Microballoons give syntactic foam its light weight, low thermal conductivity, and a resistance to compressive stress that far exceeds that of other foams.[2] These properties are exploited in the hulls of submersibles and deep-sea oil drilling equipment, where other types of foam would implode. Hollow spheres of other materials create syntactic foams with different properties, for example ceramic balloons can make a light syntactic aluminium foam.[3]