| Abstract: | The influence of fluorine on the structure of CaO-SiO_2-Al_2O_3-Na_2O-CaF_2 continuous-casting-type slag was measured by Raman spectroscopy,and the degree of polymerization of mould flux and the structural behavior of F-in the melt were investigated by classifying and quantifying the structural species of F-ions.The results exhibit that the main structural units of Si-O tetrahedra are Q~0,Q~1 and Q~2,and the actual measured number of non-bridging oxygen ions in theSiO_4]-tetrahedra(denoted by NBO/T)increases from 2.73 to 3.44 with increasing the molar ratio of F to(F+O)(denoted by X_F/X_((F+O)) from 0.06 to 0.19.It means that the degree of polymerization of melt structure decreases with an increase in X_F/X_((F+O)).In addition,most of F-ions were distributed in Si-O tetrahedra and Al-O tetrahedra.With increasing X_F/X_((F+O)),the complex structural units Al-O tetrahedra are gradually replaced by discrete structural units AlF4-because of the breakage of Al-O bonds in Al-O tetrahedra by F-ions,and the SiO(bridging oxygen)bonds of Si-O tetrahedra are broken to form SiO_nF_(4-n)]-tetrahedra by F-ions coordinating with Si~(4+). |
