Crystallinity and density of glass-ceramics obtained from basalt

Reference	Presenter	Authors (Institution)	Abstract
16-022	Luiza Felippi Lima	Lima, L.F.(Universidade de Caxias do Sul); Cruz, R.C.(Universidade de Caxias do Sul);	Glass-ceramic materials obtained from basaltic rocks are of great economic, scientific and technological importance. However, they are not manufactured in Brazil. The basalts can be melted at temperatures close to 1400 °C and if cooled quickly form glasses. When heated, these glasses can form glass-ceramics if the Fe2O3/FeO ratio of the rock is greater than 0.5. Therefore, the control of the temperature and the times of heat treatment are also fundamental for the adjustment of the desired microstructure, which defines the properties of the obtained glass ceramic. In this work the glass-ceramic microstructures obtained from a basaltic glass of Serra Geral Formation were evaluated, as a function of different cycles of thermal treatments of sinter crystallization in an inert atmosphere. Cycles were applied at temperatures of 800, 838 and 1032 °C according to the crystallization peaks identified by thermal analysis (STA). The characterization of the microstructure was performed by optical microscopy, SEM and XRD techniques. The apparent density of the samples was also evaluated as a function of the heat treatment cycle applied. The results of optical microscopy and SEM showed that sintering and crystallization of phases increased with increasing temperature. From the XRD results an increase in the crystallinity index was observed from 46% to 74%, which were accompanied by the increase in the apparent density of the glass-ceramic, from 2,22 g.cm-3 to 2,35 g.cm-3 when heat treated at 800 and 1032 °C, respectively.
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