Microspheres are spherical particles that can be distinguished into two categories; solid or hollow glass microspheres typical ranges from 1 to 200 μm in diameter. Both solid and hollow glass microspheres can be produced from glass, ceramic, carbon or plastic. Solid glass microspheres are usually made from soda-lime glass due to the low melting point and chemical inertness of soda-lime glass. The conventional method in producing solid glass microspheres is by the In-Flame Spheroidisation Method where a continuous controlled flow of powdered glass is feed to a gas flame. In contrast, hollow glass microspheres are produced by adding a blowing agent to glass powder.
Blowing agent such as sodium silicate decomposes to multiple gases when burned, causing the microsphere to form with a hollow structure. Hollow glass microspheres applications as fillers in syntactic foams resulting in reduction of material density, compaction and heat conductivity. Developed Vertical Thermal Flame (VTF) process has potential to produce cenosphere from fly ash with high yields.
In the VTF process, the raw materials are fed into a vertical tube via a funnel and the raw material will come in contact with the flame located at the bottom of the vertical tube. The burned particles are collected and cooled in a beaker via a collector plate before proceeding to the particle characterization study.
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