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

Abstract

The modification of MgO•Al 2 O 3 spinel inclusions into less detrimental mixture phases of CaO-MgO-Al 2 O 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 2 O 3 spinel and calcium aluminate (CaO) x -(Al 2 O 3 ) y phases. Samples were synthesised from MgO•Al 2 O 3 spinel (MA), Al 2 O 3 and calcium aluminate phases to achieve binary samples of CA-MA, C3A-MA, C12A7-MA and Al 2 O 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 2 O 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 2 O 3 and its potential application in inclusion characterisation.

Application of Raman Spectroscopy for Characterizing Synthetic Non-Metallic Inclusions Consisting of Calcium Sulphide and Oxides

“…Additionally, phases such as Al 2 O 3 , MgO•Al 2 O 3 , C12A7, CA, C3A, and CaS have been measured and demonstrated to be Raman active [11][12][13][14][15]. Furthermore, Raman spectroscopy is found to be applicable in various research fields for quantitative and qualitative analysis [16], including some studies already done on synthetic [17,18] and actual [19] inclusion phase studies. However, spectroscopic techniques like Raman spectroscopy have not been used in detail to study duplex oxide-sulphide inclusions like C12A7-CaS, C3A-CaS, and CA-CaS.…”

“…where I k is the intensity for the Raman shift k, x c is the calibration feature candidate, and In represents the intensity corresponding to the Raman shift n. The use of relative intensities treats the signal similarly as does the unit normalization, and thus additional normalization was not carried out. The average mean absolute error (MAE) was calculated using 4N repetitions for the cross-validation and a detailed description of how the calibration model identification and the selection process were conducted can be found in [18]. These two analytical techniques were considered in this study as complementary methods, where XRD provided information concerning individual phase weight percentage in the sample, and XRF for estimating the elemental composition of the prepared samples [28].…”

“…The authors' previous studies focused on the use of Raman spectroscopy for characterizing calcium-aluminate (CaO-Al 2 O 3 ) inclusions [17] and calcium aluminate-spinel (MgAl 2 O 4 ) [18] in a binary system. However, these studies were limited to only oxides, and the application of Raman spectroscopy for characterizing potential detrimental sulphide inclusions such as CaS associated with oxides were not studied.…”

Characterization of Synthetic Non-Metallic Inclusions Consisting of TiN, Ti2O3, and Oxides of Al2O3 and MgO·Al2O3 Spinel Using Raman Spectroscopy

“…Previous studies have demonstrated the prospective application of Raman characterizing oxide mixtures from Al 2 O 3 , MgO•Al 2 O 3 spinel (MA), and calcium aluminates from synthetic inclusions phase [10]. In addition, the study conducted by S. Li and Hihara (2017) [11] has shown that individual phases of calcium-aluminate-based inclusions, such as CaO•Al 2 O 3 (CA), in steel samples could be identified in steel samples using Raman spectroscopy.…”

Quantification of Synthetic Nonmetallic Inclusion Multiphase Mixtures from a CaO–Al2O3–MgO–CaS System Using Raman Spectroscopy

“…Furthermore, Jing et al [21] have shown that the route of inclusion modification and also the calcium content in the steel melt might affect the final inclusion composition. However, previous studies concerning the application of Raman spectroscopy for synthetic, [14,17,19,23] or steel samples [20] and nonmetallic inclusion studies have been limited to characterizing only the binary system between (CaO-Al 2 O 3 ) and the (CaS, Al 2 O 3 or MgAl 2 O 4 ) or MgO-CaO-Al 2 O 3 systems. Consequently, further studies regarding the use of Raman spectroscopy for characterizing a mixture of phases found in CaO-Al 2 O 3 -CaS and CaO-Al 2 O 3 -MgO-CaS systems will contribute to expanding the potential use of this technique for nonmetallic inclusions analysis.…”