Preparation of hollow glass microspheres by flame synthesis from waste glasses

Hollow glass microspheres (HGMs) are a low cost but high performance material with a number of various
applications. HGMs are desirable in many industries for use as fillers for various organic and inorganic matrices, or
can find applications in the medical field, for fabrication of lightweight composite materials, buoyancy materials,
thermal insulation materials and for gas storage. The use of HGMs has expanded in last years for their excellent
properties. The combination of heat resistance, lightweight and favorable mechanical properties offered by these new
materials opens up application in aviation transport and the automotive industry. This paper illustrates the possibility
of using recycled glass to obtain hollow glass microspheres with Na2SO4 blowing agent. HGMs were prepared from
soda lime glasses (automotive glasses) by flame spheroidization process in oxygen-methane (O2/CH4) flame. We
investigated the influence of glass precursors (glass powders with blowing agent) preparation, Na2SO4 concentration,
melting temperature, holding time, diffusing or dissolving SO3 element into the glass of the glass powders, particle
size distribution of glass precursors, feed rate of precursors into the flame, on formation of hollow glass microspheres.
The amorphous nature of HGMs was confirmed by X-ray diffraction (XRD). The morphology of the hollow glass
microspheres was examined by scanning electron microscopy (SEM) and the composition of the waste glass powders
and produced HGMs were determined using SEM-EDS.