Thermodynamic Investigation of Crystallization Behaviour of Pyroxenic Basalt-Based Glasses

For a series of pyroxenic basalt-based glasses, DTA was used to elucidate the changes occurring on including specified oxidizing agents and rectifying oxides Na 2 O and/or CaO, or CaO+MgO to modify one or more of the ratios FeO:Fe 2 O 3 , CaO:Na 2 O and CaO:MgO that affect the monominerality and crystallization behaviour. From comparisons of the positions, characters and intensities of the DTA peaks, the effects of the rectifying component on the crystallization processes were readily demonstrated. The higher crystallizabilities exhibited when MnO 2 was used as oxidizing agent and Na 2 O and/or MgO as rectifying oxides were related to their effects in reducing the viscosity of the glass and in enhancing the nucleation rate of the glass.