Effect of fluorspar and alumina on the viscous flow of calcium silicate melts containing MgO

For the investigation of the effect of fluorspar and alumina on the viscous flow and the crystallization behavior of the silicate melts, the viscosity of the CaO-SiO2-10 Wt%MgO-CaF2 (or -Al2O3) system was measured. The addition of CaF2 decreased the crystallization temperature (T-CR) of the CaO-SiO2-MgO-CaF2 system, while the TCR of the CaO-SiO2-MgO-Al2O3 (wt%CaO/ Wt%SiO2 = 1.0) system exhibited a minimum value at 10 wt% Al2O3. The activation energy was decreased in the CSMF system and vice versa in the CSMA system by addition of CaF2 or Al2O3 in each system. From the relationship between the activation energy and the composition of the glasses, the following equation could be obtained. E (kJ/mol) = 293.2-90.9B(total) where the B-total is the ratio of (wt%CaO + wt%CaF2 + wt%MgO)/(wt%SiO2 + wt%Al2O3). This means that CaO, CaF2, and MgO would behave as a network modifier, while SiO2 and A(2)O(3) behave as a network former in the glasses investigated. (C) 2004 Published by Elsevier B.V.