Effects of fluoride content on structure and properties of steel slag glass-ceramics

The hot steel slag were utilized for preparing the glass-ceramics by melting method with different fluoride contents. The crystallization behaviors of the glass-ceramic were characterized by Differential Scanning Calorimeter (DSC), X-ray Diffraction (XRD), Fourier Transform Infrared Spectrometer (FTIR), Raman, and the Field Emission Scanning Electron Microscope (FESEM).The results established that the transition from Nepheline to Cuspidine, and then to Kalsilite, and finally became Combeite in glass-ceramics occurred with the decrease of fluoride content. Besides, a comprehensive analysis of FTIR and Raman revealed that the addition of fluoride contributed to the formation of the Si–O bridge oxygen in the glass structure, which improved the degree of polymerization of the glass structure and further affected the crystal phase of the glass-ceramics. In addition, when Nepheline and Cuspidine constituted as the major crystalline phases for the prepared glass-ceramics, a higher flexural strength and a smaller volume shrinkage were achieved. SEM depicted that the above mentioned results were ascribed to from the changes in the crystal type and the degree of crystallization, in which the size of the crystal phase had a greater influence on the performance of the glass-ceramic. It was worth noting that the highest flexural strength was 177.76 MPa with the lowest volume shrinkage of 0.06%. •Fluoride affected the type of crystal phase and crystallization process.•Fluoride contributed to the formation of the Si–O bridge oxygen bonds.•Fluoride had abnormal effect in high alkalinity glass.•The glass-ceramics with flexural strength of 177.76 MPa can be obtained.