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

The present paper shows the results of a nucleation and crystallisation study of a Nafluorrichterite glass carried out by dynamic scanning calorimetry (DSC). The kinetic study was performed using different procedures (Kissinger, Matusita-Sakka and Kissinger-AkahiraSunose (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.