Structural behavior of F- in mould flux melt of CaO-SiO2-Al2O3-Na2O-CaF2 system

摘要

The influence of fluorine on the structure of CaO-SiO 2 -Al2 O 3 -Na2 O-CaF2 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 m elt 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 Q0 , Q1 and Q2 , and the actual measured number of non-bridging oxygen ions in the [SiO 4 ]-tetrahedra (denoted by NBO/T) in-creases 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 Si-O (bridging oxygen) bonds of Si-O tetrahedra are broken to form [SiO n F4-n ]-tetrahedra by F- ions co-ordinating with Si4+ .