A Feedback Mechanism Between Crystals and Bubbles in a RuO2-Bearing Melt
Résumé
Crystals are known to affect bubble behavior in both natural and industrial glass melts. In volcanological systems, high crystal contents (> 30 vol.%) may drastically increase the suspension viscosity, altering bubble dynamics sufficiently to modify the eruptive styles. During industrial glass production, the presence of crystals may affect both the process itself and the final product. In this present work, we investigate how a small crystal fraction of nano-sized RuO2 (~ 2.0 vol.%, i.e. 5.0 wt.%) could be enough to modify the bubble behavior in a molten glass, generating a cyclic gas-releasing phenomenon. We apply a series of lab-scale crucible tests, at high-temperature, on a three-phase system composed of a Ce-bearing borosilicate melt, bubbles, and RuO2 crystals. A postmortem optical microscope approach is applied to investigate the solidified samples after thermal treatment at 1000 °C (in air and without agitation) for different dwell times. Viscosity measurements on the crystal-bearing melt, contact angle measurements on melt-RuO2-air system, and some simulations on bubble-crystal attachment are carried out to support the findings. Herein, we propose a mechanism based on crystal entrainment to the top surface by the bubbles as well as crystal aggregation, followed by an increase in viscosity to explain the observed cyclic gas-releasing phenomenon.
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