Devitrification Behavior of A Glass Obtained From Porphyric Sands With Addition of Tio2 (4-percent) and Mgo (8-percent)

The non-isothermal devitrification of a glass obtained from porphyric sands with addition of TiO2 (4%) and MgO (8%) has been studied. Scanning electron micrography observations suggest that the glass demixes on quenching. After prolonged heat treatment at temperatures in the glass transformation range an evolution of the glass texture is observed, with formation of non-spherical particles of a separated phase. This does not seem to influence greatly the crystal growth activation energy, which has been evaluated as being E = 105 ± 5 kcal mol−1. The maximum nucleation rate temperature has been estimated to be T = 710°C. Evidence has been found that the glass-glass interfaces produced by demixting provide alternative sites of nuclei formation.