engleski

Non-isothermal and isothermal crystallization kinetics of Li2O-ZnO-Al2O3-B2O3-SiO2 glass

The crystallization kinetics of a glass based on ZnO-Al2O3-SiO2 system with small additions of Li2O and B2O3, containing TiO2 and ZrO2 as nucleating agents have been studied by differential scanning calorimetry (DSC) and X-ray difraction (XRD). A single crystallization exotherm due to the formation of gahnite (ZnAl2O4) as a main crystalline phase and small amount of β -quartz solid solution is observed in the glass heat treated under non-isothermal conditions. By nucleation at 730°C for 2 h, the crystallization of β -quartz s.s. is suppressed and gahnite as a sole crystalline phase occurred. However, to obtain glass-ceramic with the highest amount of the smallest particle sizes of gahnite, the nucleation must be carried out at 750°C. An overlapping of nucleation and crystallization of this phase exists, which has been reflected on the activation energy evaluated under non-isothermal conditions.

crystallization; kinetics; gahnite; glass-ceramics

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