Effect of melting time on volatility, OH in glass in microwave processing

ABSTRACT

Glass comprising of SiO₂-B₂O₃-Na₂O-CaO-K₂O is melted at 1523 K in the microwave (MW) and conventional heating. Evaporation loss was studied with varying melting time (30 min to 3 h). Assessment of B₂O₃, a more volatile component in the studied composition, is carried out by adopting wet chemical method like volumetric titrimetry. The rate of evaporation loss (of B₂O₃) is found ~ 20% less in MW heating. The density of glass increases slightly with increasing melting time. Chemical analysis for other volatile ingredient, K₂O using ICP-AES suggests higher yield in glass signifying less loss of K₂O in MW heating. A study adopting X-ray photoelectron spectroscopy (XPS) indicates that the ratio of nonbridging oxygen (NBO) to the total oxygen in glass increases with melting time. This signifies a higher loss of glass network former like B₂O₃. OH content in conventional glass decreases with increasing soaking time at melting temperature whereas it initially increases with time and reduces beyond 120 min of soaking at melting temperature in MW furnace. A significant reduction in energy consumption and time savings in MW heating has been recorded.

KEYWORDS:

• Glass
• melting
• microwave
• heating
• evaporation
• loss
• B₂O₃

Acknowledgments

This work was supported by Focus basic research of the Council of Scientific and Industrial Research, India. The authors would like to thank the Council of Scientific and Industrial Research, India for Focus basic research program. We acknowledge the Director of CSIR-CGCRI, for his kind encouragement and support to pursue this work. We also acknowledge Mr. Kaustav Roy, Department of Chemical Engineering, Heritage Institute of Technology, to initiate this work during the summer internship program at CSIR-CGCRI. The work is also supported by the Board of Research in Nuclear Sciences (BRNS). Mr. Yudhisthir Mandal likes to acknowledge BRNS Grant (BRNS OM: 51/14/08/2019-BRNS/36141 Dated 24/09/2019) for his fellowship.

Additional information

Funding

This work was supported by the BRNS [51/14/08/2019-BRNS/36141 Dated 24/09/2019 and CSIR, FBR MLP 106].