Rheological behaviour of CaO–MgO–SiO2–Al2O3–B2O3 system with varying B2O3 content up to 30 wt% at basicity of 0.4

Abstract

A comprehensive theoretical and experimental study describing the effect of B2O3 (0–30 wt%) on softening, liquidus, and crystallization temperatures, flow behaviour, and dynamic viscosity of the glass-based oxide system SiO2(64.64–43.21 wt%)-MgO(10 wt%)-CaO(15.86–7.29 wt%)-Al2O3(9.50 wt%)-B2O3 with a constant basicity of 0.4 was carried out. The experimental data was obtained up to 1550 °C using a high-temperature rheometer and were supported by the study of the internal structure by means of scanning electron microscopy with energy-dispersive X-ray spectroscopy, X-ray powder diffraction analysis, and Fourier transform infrared spectroscopy. The increasing addition of boron oxide caused a decrease in the start and end softening and liquidus temperatures. At 1550 °C, the systems exhibited Newtonian behaviour, with a dynamic viscosity increasing exponentially with a decreasing temperature and decreasing with increasing B2O3 content. The amorphous character of the samples and the formation of structural units [BO2O−] and [BO3] and [BO4], confirmed by complementary analyses, led to a decrease in the degree of polymerization of the silicate structure. The theoretical insight into the dependence of dynamic viscosity on the temperature and composition was realized based on molecular dynamics. Furthermore, the prediction of viscosity as a function of temperature (1230–1550 °C) and the change in chemical composition (0–30 wt% B2O3) was performed using artificial neural networks.