Coarsening kinetics in demixed lead borate melts

Abstract

Lead borate melts have been demixed at temperatures in range from 723 to 773 K for times up to 20 h. It is found that increasing time and temperature lead to characteristic changes in the size distribution of boron trioxide drops in the lead-rich glassy matrix (<80.7 mol. % B2O3). The increase of the mean drop size with annealing time followed the cube root time dependence of diffusion controlled coarsening. The diffusivity of the coarsening process was determined using liquid-liquid interfacial energy associated with drop deformation in glass specimens subjected to uniaxial compression. Diffusion coefficients of coarsening were found to match with those of (207)Pb and (18)O tracer ions in the lead borate system but differ up to four orders of magnitude from the Eyring diffusivity and by a factor of ≈7 from the activation energy of viscous flow. The results indicate that coarsening in demixed lead borate melts is most likely controlled by the short range dynamics of the interaction between lead cations and BO4 units, which are decoupled from the time scales of cooperative rearrangements of the glassy network at T < 1.1 Tg.

Hydrodynamic coarsening in phase-separated silicate melts

“…The numerical method is described in the Appendix. The order of magnitude is consistent with the scarce literature on measurements of interfacial tension between glassy melts [45,46], albeit at the lower end of reported values.…”

Microalloy Precipitation at the Glass–Steel Interface Enabling Adherence of Porcelain Enamel

“…On the other hand, we assume that the time scales of the observed microalloy precipitation will not differ from those of viscous flow at the nominal temperature of 1073 K, which is ca. 350 K above glass transition, while for demixing oxide glasses at temperatures close to T S and T SE a decoupling of the times scales of ion diffusivity from those of cooperative rearrangements of the glassy network has been observed . Thus, the precipitation kinetics is predicted to be faster for the network modifier‐rich ferrous melt close to the interface than in a distance from the steel substrate where the concentration of Fe 2+ in the enamel glass is lower.…”