In-flight-melted soda-lime-silica glass by RF induction thermal plasma

Granulated raw materials with a particle size of 20-80 μm were prepared from a slurry of Na₂CO₃, CaCO₃, and SiO ₂ (quartz) by the spray-dry method, and injected with carrier gas into a radio-frequency induction thermal plasma. Spherical particles 5-60 μm in size were obtained and analyzed. Thermo-gravimetric analysis and X-ray diffraction analysis showed that during the short flight of the order of milliseconds, all carbonates were decomposed and >95% quartz was reacted into a noncrystalline state. Glass transition was clearly observed by differential thermal analysis. Increase of the carrier gas from 3 to 6 L/min led to a decrease in the volatilization ratio of Na₂O from 46% to 18% with a slight decrease of the reaction ratio of quartz in trade balance. Electron probe microanalysis showed that the volatilization could be attributed to an excess heating of small particles <30 μm, and suppression by the increase of carrier gas.