CRYSTALLISATION AND MICROSTRUCTURE OF NEPHELINE FORSTERITE GLASS-CERAMICS

This work presents the results of a study focused on the development of forsterite-nepheline glass-ceramic with the use of rice husk ash (RHA) as a silica source. The glass-ceramics were produced by a sintering process of a glassy frit formulated in the MgO-Al2O3-SiO2 base system with the addition of B2O3 and Na2O to facilitate the melting and pouring processes. The crystallisation study was carried out by depicting the TTT curve (Time-Temperature-Transformation). The mineralogical characterisation of the glass-ceramic materials was carried out using X-ray diffraction (XRD). The crystallisation activation energies were calculated by the Kissinger method. The results obtained show that nepheline (Na2O•Al2O3•SiO2) is the major crystalline phase in the temperature interval 700-950ºC and forsterite (2MgO•SiO2) predominates at temperatures above 950ºC. A study of the microstructure by scanning electron microscopy (SEM) allowed to establish the morphological evolution in both shape and spatial arrangement of the nepheline and forsterite crystals on heating.