Crystallization kinetics of mica glass-ceramic in the SiO2-Al2O3-MgO-K2O-B2O3 -F-2 System

Abstract

A mica glass-ceramic in the SiO2-Al2O3-MgO-K2O-B2O3-F-2 glass system was prepared by a melting method. The crystallization behaviour and crystallization kinetics of a sample with glass-ceramic composition were examined. DTA and XRD analysis revealed the crystallization of phlogopite, fluorphlogopite, clinohumite and spinel phases. The activation energies for the precipitation of crystalline phases have been evaluated, and the crystallization mechanisms have been studied by applying DTA measurements performed at various heating rates. The results indicate that the growth of mica is a two-dimensional process controlled by the crystal-glass interface reaction. The average calculated values of crystallization and viscous flow for the precipitation of crystal phases from the glass matrix were measured to be 289.9 +/- 8 kJ/mol and 348.7 +/- 14 kJ/mol, respectively. The mica glass-ceramics exhibited excellent performance in machinability tests without cracking or deforming.