Viscosity and related structure transformation of fluorine bearing silicate melt under ultrasonic field

The fluorine bearing and free silicate melts of Na₂O-K₂O-SiO₂-CaF₂ system were treated under ultrasonic field, and the melt structure and viscosity were measured. The results showed that the fluorine bearing silicate melt can be depolymerized and the polymerization decreased with the ultrasonic intensity. The viscosity of the fluorine bearing silicate melt decreased more quickly to the dynamic balance point between the dissociation and reconnection of the species, and reverted more slowly to the natural state than the fluorine free silicate melt, because fluorine ions join the silicate network via the formation of new Si-F bonds. The formation of SiF bonds can intensify the reduction of the viscosity, but the consumption of fluorine ions may lead to an increasing of the viscosity, which resulted in the weak decreasing trend in the viscosity as the ultrasonic intensity increased. The method may be helpful in assisting the synthesis of fluorine bearing bioactive glass.