Abstract
This study presents microwave absorption of raw materials used in barium borosilicate, Fe-doped alumina phosphate and zinc borate glass. Microwave absorption was investigated for the raw materials SiO2, Na2CO3, BaCO3, BPO4, Al(PO3)3, Mg(PO3)2, Al(OH)3, TiO2. The study shows that SiO2 could be heated directly above 1000 °C within 30 min at 1.5 kW microwave output (MW) power and 0.8 kW MW power is necessary to initiate heating (from 260 °C). Microwave heating of material with low dielectric loss has been investigated by increasing MW power. Microwave absorption of above glass systems has also been investigated. Dielectric properties such as loss tangent of glass as a function of temperature are presented. Glass melting under direct microwave heating was demonstrated for the studied glass systems. Temperature-Microwave power-Time (T-P-t) profiles for the three glasses indicate maximum MW output power ~1 kW, 0.65 kW and ~1 kW for barium borosilicate, zinc borate glass and alumino-phosphate glass for 60 g glass melting.
Highlights
Microwave energy is being applied as a new method for high-temperature material processing apart from its different other applications
It can be identified that BPO4 absorbs microwaves at 0.8 kW microwave output (MW) power and temperature above 1000 °C can be raised under direct microwave heating with 1 kW MW power
Microwave output power plays an important role in microwave heating
Summary
Microwave energy is being applied as a new method for high-temperature material processing apart from its different other applications. Most of the raw materials of glasses are poor microwave absorbers at room temperature except some of the transition metal oxides, some of the compounds of metal, and a few other materials containing water molecules within the composition of those materials. A scope of work exists to study the absorption of glass and its raw materials at the higher output power at room temperature. The authors’ group is working to develop a glass melting process using microwave energy as an alternative heating route with several glass compositions (melting temperature range 1200–1500 °C) with or without microwave absorber as a constituent raw material in glass batch. The present study reports microwave absorption and thereby heating of raw materials and glasses for barium-borosilicate, alumina-phosphate and zinc-borate glass. Dielectric loss tangent of these three glasses is studied as a function of temperature (~1000 °C)
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