Structure and viscosity of CaO-Al2O3-B2O3 based mould fluxes with varying CaO/Al2O3 mass ratios

Abstract

The effect of CaO/Al2O3 ratio on the structure of CaO-Al2O3-B2O3 based glassy mould fluxes was investigated by employing 27Al and 11B Triple Quantum Magic-angle spinning nuclear magnetic resonance (3QMAS-NMR) and Raman spectroscopy. 27Al and 11B 3QMAS-NMR spectrums showed that Al3+ mainly forms [AlO4] as a network former and B3+ mainly forms [BO3] groups in CaO-Al2O3-B2O3 based glasses. Raman spectrum showed existences of different [AlO4] structure units and BO3 pyro-borate units. In addition, deconvolution results on Raman spectrums indicate that the degree of polymerization of aluminate network in CaO-Al2O3-B2O3 based glasses decreases with the increase of CaO/Al2O3 ratio. The effect of CaO/Al2O3 ratio on viscosity of CaO-Al2O3-B2O3 based glassy mould fluxes was investigated by employing the rotating-cylinder method. The viscosity decreases with increasing CaO/Al2O3 ratio in CaO-Al2O3-B2O3 based mould flux. Correlation between viscosity and structural information of investigated mould fluxes was explored.