Abstract
Glasses based on the SiO2–Al2O3–MgO–BaO–MgF2 system added with B2O3 were synthesized and characterized by differential thermal analysis (DTA), X-ray powder Diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM) techniques. The glass transition temperature (Tg) and first crystallization peak temperature (Tp1) decreased, whilst the second crystallization peak temperature (Tp2) increased with increasing B2O3 content. The crystallization kinetics of amorphous glass specimens have been studied through DTA. The increase in B2O3 content has little influence on the value of Avrami exponent (n), keeping three-dimensional crystals growth mechanism. An interlocking blocky microstructure with a house-of-cards crystals structure was observed with high B2O3 content and at heat treated temperature from 800°C to 1050°C for 5h. As the B2O3 content and heat treated temperature increased the Vickers hardness decreased slightly on formation of the interconnected barium fluorophlogopite phase, which contributes to the improvement of machinability of glass-ceramics.
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