The Crystallization and Characterization of Calcium-Magnesium- Aluminosilicate Glass-Ceramics

Abstract

Calcium-magnesium-aluminosilicate (CaO.MgO.Al3O3.SiO2) glass-ceramics was developed from the base glass system of the composition 52.00 wt% SiO2, 16.00 wt% Al2O3, 12.00 wt% CaO, 8.00 wt% MgO, 2.00 wt% K2O, 6.00 wt% TiO2, 0.30 wt% NaCl and 3.70 wt% in this study. The study focused attention on the crystallization of CaO.MgO.Al3O3.SiO2 base glass system using 363℃ & 663℃ as nucleation and crystal growth temperatures respectively, and 1 – 4 hours as soaking time. The composition was melted at 1600℃ for 3 hours in a muffle furnace and the molten glass was cast into rods, annealed at 600℃ for 1 hour and finally cooled to room temperature. Due to the presence of impurities in the starting materials, the glasses produced have a brownish physical appearance. Base glasses were crystallized into glass-ceramics using double-stage heat treatment schedule, and XRD and SEM were used to characterize the produced samples. The XRD identified the crystalline phases precipitated in the residual glass matrix of the sample soaked for 4 hours as albite, quartz, wollastonite and witherite. The SEM result revealed that the microstructure of the sample is characterized by dense, circular-like and needle-like clusters alongside micro-sized voids dispersed in the residual glassy phase matrix. The density and hardness values were found to increase while weight loss decreased with increase in soaking time across the samples. The sample soaked for 4 hours has the lowest weight loss but with the highest density and hardness values making it suitable for use for abrasion due to its excellent properties.