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 volcanic systems, high crystal contents ($\phi_c$> 30 vol.%) may drastically increase the suspension viscosity, altering bubble dynamics severely enough to modify eruptive style. During industrial glass production, the presence of crystals can corrupt the process and the final product. In this present work, we investigate how a small crystal fraction of nano-sized RuO2 ($\phi_c$ ~ 2.0 vol.%, i.e. 5.0 wt.%) modifies bubble behavior in a molten glass, generating a cyclic gas-release phenomenon. We conduct a series of high-temperature, lab-scale, crucible tests, on a three-phase system composed of a Ce-bearing borosilicate melt, bubbles, and RuO2 crystals. Optical microscopic investigation is performed on the products of thermal treatment at 1000 °C (in air and without agitation) for different dwell times. Based on viscosity measurements on the crystal-bearing melt, contact angle measurements in the melt-RuO2-air system, and numerical simulations of bubblecrystal attachment, we propose a mechanism of entrainment of bubbles carrying crystals to the upper free surface accompanied by crystal aggregation, and followed by an increase in viscosity to explain the phenomenon of cyclic gas-release observed in this system.
Origine : Fichiers produits par l'(les) auteur(s)