The influence of local raw materials on phase crystallization of nepheline-pyroxene glass-ceramics

A series of local raw materials using different nucleating agents like TiO2, LiF, and Cr-2,O-3, have been studied to examine the crystallization phases of Nepheline-Pyroxene glass-ceramic. The DTA traces of the glasses showed that the crystallization reactions occurred at a temperature range of 559-715degreesC. TiO2 rapidly crystallized the glass sample and the nepheline (K AlSi3O8) and titanite (CaTiSiO5) phases. The nucleation of LiF in glass samples revealed the formation of wollastonite (CaSiO3) akermanite (Ca2MgSi2O7) and diopside Ca(MgFeAl)Si. Cr2O3 helped in the formation of diopside Ca(Mg Fe Al)Si and nepheline (K Na)AlSiO4 phases. The effect of batch composition on the crystallization of the glass showed the crystallization of nepheline (KNa)AlSiO4, diopside Ca(MgFeAl)Si, akermanite (Ca2MgSi2O7), and gehlenite (Ca2Al2SiO7) phases. The thermal coefficient values of sample heat treated at 1000degreesC/30 h progressively increased from 50.7 x 10(-7)/degreesC (nucleating free glass) up to 80 x 10(-7)/degreesC when different nucleating agents were added. It is found that different type of the nucleating agents, CaO/MgO content, and heat treatment affected the mineral constitution of the crystalline materials formed and their thermal coefficients.