Investigation of Glass Preparation using Processed Nepheline Syenite from Kaleybar, Iran

In this study, the change of the structure of Nepheline (Neph) (including two minerals, syenite and microcline) was studied, using hydrothermal and milling methods by the 2 % mol. soda (NaNeph) and 30 wt % lime (CaNeph), respectively. The X-ray diffraction and Raman spectra show that, the structure of the microcline phase in the (CaNeph) sample remained stable but the structure of Nepheline was somewhat degraded. The main characteristic XRD peaks of Nepheline in the NaNeph sample at 28º stayed compared to the CaNeph one. According to Raman spectroscopy the structural order of alumina-silicate rings in CaNeph sample was higher than Neph due to the 3 hs. milling and entering of the alkaline earth elements into the ring structure. Finally, Nepheline bearing glass samples with chemical composition of 6 wt % Al2O3-65.5 wt % SiO2-13 wt % Na2O-16 wt % CaO were used. The amounts of used Nepheline in the composition of glasses were 25 to 38 % by weight (depending on the final composition). The difference in thermal behavior of GCaNeph, GNaNeph and GNeph glasses was compared by means of thermal analysis (DTA/TG) and volumetric change (dilatometry). The glass transition temperatures were 25, 37 ºC increased in GCaNeph and GNaNeph compared to Neph samples (without processing) respectively. The chemical resistance of GCaNeph and GNaNeph glasses in the present work was 4 times higher than GNeph. The density of GCaNeph glass in the present work was 0.9 g/cm3 higher than GNeph.