Chemical durability and weathering resistance of canasite based glass and glass-ceramics

Classic composition 8.4Na₂O·5K₂O·10.8CaO·64SiO₂·10.5CaF₂·1.3Al₂O₃ (G1/GC1) and high silicon composition 7.6Na₂O·4K₂O·8.4CaO·71SiO₂·8CaF₂·1.0Al₂O₃ (G2/GC2) canasite-based glass and glass-ceramics were prepared, and the chemical durability and weathering of samples were studied with XRD, ICP-AES, SEM and optical microscopy. Interestingly, a kind of color fringe pattern caused by the acid leaching was directly observed on the glass ceramic surface under optical microscopy. The 20 day weight losses of glass and glass ceramic in acid (1 M HCl) and alkali (1 M NaOH/1 M Na₂CO₃) solution were measured. Accelerated weathering was used to demonstrate that increasing silicon content contributes to the weathering performance of glass and glass-ceramics. For different micro-structures and compositions, the weight loss of each glass and glass-ceramic is quite different. In general, through increasing the network interconnectivity of residual glass network and suppressing the crystallization of the less durable canasite phase, the addition of SiO₂ (from 60 mol% to 71 mol%) enhanced the chemical durability of canasite-based glass and glass ceramic relatively under acid, alkali and weathering conditions.