Crystallization process of a biomaterial, the lithium disilicate, obtained from rice husk silica

Abstract

In this work, the crystallization process of lithium disilicate glass-ceramic was investigated with SiO2 from rice husk silica replacing the high-purity SiO2 starting powder form commercial source. Glasses were developed at the stoichiometric composition of 66%.molSiO2:33%.molLiO2 using commercial SiO2 and the one obtained by thermochemical treatment of rice husk. To compare the SiO2 sources, the influence of the one from rice husk on crystallization process was measured using different granulometry, analyzing microstructure and the kinetic behavior. Investigations were carried out by means of differential thermal analysis (DTA), X-ray diffractometry (XRD) and scanning electron microscopy (SEM). Amorphous glasses were obtained after melting at 1550°C. The position of lithium disilicate glass-ceramic crystallization peaks (Tp) are between 550 to 660°C to different granulometry (<63mm, 63mm < × < 250mm and 1mm < × < 2mm) and DTA heat rates (5; 10; 15; and 20°C/min) in both glasses, and the relevant formed crystalline phase after DTA analysis (verified for XRD) was Li2Si2O5. SEM images showed the increase of glass substitution for crystalline phase to both glass-ceramics from different silica sources.