Characterisation of Binary Phase Mixtures of Magnesium-Aluminate Spinel and Calcium-Aluminates Using Time-Gated Raman Spectroscopy

摘要

The modification of MgO·Al_2O_3 spinel inclusions into less detrimental mixture phases of CaO-MgO-Al_2O_3 plays an essential role in refining calcium-treated aluminium killed steels. This study uses Raman spectroscopy for the characterisation of binary phase samples that contain MgO·Al_2O_3 spinel and calcium aluminate (CaO)_x-(Al_2O_3)_y phases. Samples were synthesised from MgO·Al_2O_3 spinel (MA), Al_2O_3 and calcium aluminate phases to achieve binary samples of CA-MA, C3A-MA, C12A7-MA and Al_2O_3-MA with varying phase fractions. The study also examined the possibility of a slight variation for non-stoichiometric spinel samples below the 1 600°C region in an MgO-Al_2O_3 binary system. The relative intensities of the Raman band were used for the quantification of the phase fractions. For a quantitative prediction, linear regression calibration models were identified for each of the studied systems. This work demonstrates the use of Raman spectroscopy for the characterisation of calcium aluminate phases of CA, C3A, C12A7 and magnesium aluminate spinel phases along with Al_2O_3 and its potential application in inclusion characterisation.