Effects of nano silica on synthesis and properties of glass ceramics in SiO2–Al2O3–CaO–CaF2 glass system: A comparison

Glass ceramics of composition 34SiO2–29Al2O3–25CaO–12CaF2 (wt.%) was made by conventional melting and quenching process using either normal or nano-SiO2 respectively. The glasses were characterized by differential thermal analysis (TG/DTA), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM). The crystallization, microstructure, mechanical and chemical properties were compared for the two systems. With nano-SiO2 addition, the crystallization peak temperature (Tp) decreases, activation energy (E) and Avrami parameter (n) have very little change, and the mechanism of crystallization of the glass ceramics changed from surface crystallization to two-dimensional crystallization. The crystallite size of nano-SiO2 containing glass is lower than the normal SiO2 containing glass. Introduction of nano-SiO2 particles in glass ceramics gives higher Vickers hardness, shrinkage, lower water absorption, and higher acid resistance than the normal silica containing glass ceramics, thus making it more useful for industrial building, internal and external wall facing and tiles applications.