Influence of preformed nuclei on crystal nucleation kinetics in soda-lime-silica glass

An unusual form of the time-dependence of the number N(t, T-n) of nucleated at a temperature T-n crystals was obtained for a soda-lime-silica glass of the composition 22.4Na(2)O-28.0CaO center dot 49.6SiO(2) (mol.%). The crystals are solid solutions based on the Na2O center dot 2CaO center dot 3SiO(2) compound. The analysis of the nucleation kinetics was performed for a nucleation temperature T-n located well below the temperature of the maximum of the steady-state crystal nucleation rate. Following to the development method, supercritical clusters formed at the temperature T-n have been developed at a temperature T-d > T-n in order to reach measurable sizes. A large number of crystals, N(t, T-n, T-d) = N-o, was detected by this method already at t = 0. With an increasing nucleation time, the number of developed crystals gradually increases with a temporary tendency towards saturation. After this transient stage, the crystal number gradually increases again and a linear N(t, T-n, T-d)-dependence corresponding to the steady state nucleation rate is established. These uncommon features are the consequence of the growth at the nucleation temperature of the nuclei preformed in the course of glass preparation with sizes between critical sizes corresponding to the nucleation T-n and development T-d temperatures. (C) 2015 Elsevier B.V. All rights reserved.