THERMODYNAMIC INVESTIGATION OF CRYSTALLIZATION BEHAVIOR OF PYROXENIC BASALT-BASED GLASSES

For a series of pyroxenic basalt-based glasses, DTA was used to elucid ate the changes occurring on including specified oxidizing agents and rectifying oxides Na2O and/or CaO, or CaO+MgO to modify one or more of the ratios FeO:Fe2O3, CaO:Na2O and CaO:MgO that affect the monominera lity and crystallization behaviour. From comparisons of the positions, characters and intensities of the DTA peaks, the effects of the recti fying component on the crystallization processes were readily demonstr ated. The higher crystallizabilities exhibited when MnO2 was used as o xidizing agent and Na2O and/or MgO as rectifying oxides were related t o their effects in reducing the viscosity of the glass and in enhancin g the nucleation rate of the glass.