Nucleation and crystallisation kinetics of a Na-fluorrichterite based glass by differential scanning calorimetry (DSC)

Abstract

The present paper shows the results of a nucleation and crystallisation study of a Na-fluorrichterite glass carried out by dynamic scanning calorimetry (DSC). The kinetic study was performed using different procedures (Kissinger, Matusita-Sakka and Kissinger-Akahira-Sunose (KAS) methods), and the Avrami parameter was determined from the Ozawa and Malek approximations and the Malek equation. The results have indicated the coexistence of surface and bulk crystallisation in the devitrification process of the studied glass. The kinetic study has shown that the activation energy of the crystallisation process is over 400 kJ/mol and that the mechanism proposed is a Johnson-Mehl-Avrami mechanism with n equal to 3, which implies that the crystallisation develops through the three-dimensional growth of crystals. The study of the variation of the activation energy with crystallisation using the KAS method has shown that the crystallisation process undergoes a multiple step mechanism, where the main part of the whole process corresponds to the three-dimensional growth of crystals. The mechanism proposed was confirmed by applying the Pérez-Maqueda et al. criterion.

Surface and volume crystallization in fluorrichterite based glasses

“…However, limited papers report on the progress of crystals at the earliest stage of the devitrification of fluorrichterite. In previous papers, we stated the concurrence of surface and bulk crystallization in the devitrification process of Na-fluorrichterite glasses [17]. Surface crystallization mechanism predominates at the beginning of the crystallization process; however, volume crystallization attains significance with increasing fluorine content in glass composition [18].…”

Crystallization Kinetics and Mechanism of CaO–Al2O3-Based Mold Flux for Casting High-Aluminum TRIP Steels

“…[4] has been extensively employed to determine the Avrami exponent for non-isothermal crystallization. [30][31][32][33] The relative degree of crystallinity x at a given temperature T can be calculated from DSC curve with respect to temperature using the following equation…”