CHARACTERIZATION AND CRYSTALLIZATION KINETICS OF A DIOPSIDE-BASED GLASS-CERAMIC DEVELOPED FROM GLASS INDUSTRY RAW-MATERIALS

Glass industry raw materials blended with 10 wt% technical grade TiO2 powders were used to develop a glass-ceramic of the SiO2-MgO-Al2O3-CaO -(Na2O,K2O) system. On the basis of the DTA analysis, nucleation and c rystallization experiments were carried out at 735 and 870 degrees C, respectively. X-ray diffraction studies performed on the glass-ceramic system revealed the presence of the diopside as the major crystallizi ng phase comprising about 74 vol%. SEM investigations showed that the diopside crystals were formed as a result of surface nucleation and we re conical in shape, between 15 and 40 mu m in length and between 5 an d 13 mu m in width. DTA analyses were conducted at different heating r ates and an activation energy for surface crystallization value of 150 kJ/mole was determined graphically from a Kissinger-type plot using t he analysis of Matusita and Sakka. This value is about half of that fo r the same glass composition without the TiO, content. (C) 1997 Elsevi er Science Limited.