# Micro-Raman Spectroscopy Investigation of Crystalline Phases in EAF Slag
## 4 Conclusions  
In this work, the crystalline phases, morphology and chemical composition of EAF black slag samples from five steel factories are studied. Samples characterised by well-developed crystalline phases were obtained. SEM-EDXS, 2D-XRD and \(\upmu\)-Raman analysis were performed on the three different grain types, which were identified by SEM. The EDXS elemental composition made it possible to predict that the three types of grains mainly correspond to the brownmillerite, larnite and magnesioferrite phases identified by XRD. In the same area, \(\upmu\)-Raman spectra were collected, and the results showed a good reproducibility in each grain and good agreement with the spectra of the phases reported in the literature.  
No amorphous phases were identified, probably because the reference sample had been slowly cooled to allow the crystalline phases to grow. However, the identification of amorphous phases of EAF slag is a perspective for Raman analysis, and amorphous silicates have been widely studied [34; 35; 36]. A Raman database devoted to crystalline phases of EAF slag identification has been created to be used by portable Raman instruments, allowing phase characterisation of the slag directly during the steel production. Indeed, we believe that in the near future, Raman spectroscopy will be introduced into steelworks to carry out on-line slag analysis, which could be valuable for optimising processes during the steel production.  
The following are available online at [[http://www.mdpi.com/2076-3417/10/12/4115/s1](http://www.mdpi.com/2076-3417/10/12/4115/s1)]([http://www.mdpi.com/2076-3417/10/12/4115/s1](http://www.mdpi.com/2076-3417/10/12/4115/s1)), Figure S1. SEM micrographs of samples B, C, D and E. Numbered purple squares represent the position were EDXS measurements are collected, Table S1. SEM micrographs of samples B, C, D and E. Numbered purple squares represent the position were EDXS measurements are collected, Figure S2. XRD patterns of samples B, C, D and E, with the corresponding phase identification, Figure S3. Raman spectra of sample A, B, C, D and E. Time measurement 50 s.  
Conceptualisation, A.R., L.B., I.V. and L.E.D.; methodology, A.R., L.B., L.E.D; software, A.R., I.V., G.C. and M.G.; investigation, A.R., I.V., G.C., M.G.; writing--original draft preparation, A.R.; writing--review and editing, L.B., I.V., A.C., M.V.B., G.C., M.G.; supervision, L.E.D.; project administration, L.E.D.; funding acquisition, L.E.D. Please refer to the CRediT taxonomy for the term explanation. All authors have read and agreed to the published version of the manuscript.  
This research was funded by Regione Lombardia Cariplo Foundation 19037, 18-12-2018 on B.U.R.L. n\({}^{\circ}\) 52, 27-12-2018, grant n\({}^{\circ}\) 2018-1733, project \"Development of novel slag-based glass ceramic for plasma spray coating and 3D printing--3D SLAG\", CUP E83D18000240009.  
Figure 4: \(\upmu\)-Raman and spectra example of magnesiochromite, wüstite and gehlenite identified phases in samples B, C, D and E. Time measurement 50 s.  
**Acknowledgments:** The authors acknowledge RAMET consortium (Environmental Research for Metallurgy) for providing the samples.  
**Conflicts of Interest:** The authors declare no conflict of interest. The funders had no role in the design of the study; in the collection, analyses, or interpretation of data; in the writing of the manuscript, or in the decision to publish the results.