Crystal Growth in the System PbO‐B₂O₃

Abstract

The temperature dependence of the rate of growth of PbO/2B2O3 from lead borate melts with PbO/B2O3 mole ratios of 1/3,1/2, 2/3, and 1 was determined. The maximum growth rates occurred from those melts which contained a slight excess of PbO. The results are explained on the basis of a modification in the structure of the melt in the interfacial zone as the PbO content is changed. Such changes markedly affect the fluidity of the melt, alter the concentration of crystallizable species, and may reduce the driving force for crystallization.

Effects of super-gravity field on precipitation and growth kinetics of perovskite crystals in CaO–TiO2–SiO2–Al2O3–MgO melt

“…Moreover, with the decrease of cooling rate, the fine perovskite crystals with characteristic of dispersing spicule gradually changed to the larger dendrites and equiaxed crystals, and the precipitation amount of perovskite crystals also increased significantly, which was consistent with the results of Zhang et al 12 and Eagan. 18 This indicated that with decreasing of the cooling rate, the reaction time of Ca 2+ and TiO 3 2− extended, and thus both the self-growth and the grain coarsening of perovskite crystals were promoted.…”

“…12 and Eagan. 18 This indicated that with decreasing of the cooling rate, the reaction time of Ca 2+ and TiO 3 2− extended, and thus both the self-growth and the grain coarsening of perovskite crystals were promoted.

2 Vertical section of the sample obtained in a normal-gravity field at a cooling rate of 1 K min −1

3 Micrographs of the samples obtained in a normal-gravity field at different cooling rates: a α = 6 K min −1 , b α = 3 K min −1 , c α = 2 K min −1 , d α = 1 K min −1

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“…With respect to the precipitation mechanism of crystals from the slag melt in normal condition according to the studies of Sui et al . 7 and Eagan et al ., 18 the Ca 2+ reacted with TiO 3 2− to form perovskite crystals in the titanium-bearing slag. Nevertheless, with the precipitation of perovskite, the concentrations of Ca 2+ and TiO 3 2− around the first precipitated crystals decreased gradually, and thus the nucleation of perovskite crystals were blocked.…”