Effect of Na2O on the sintering and melting behavior of CaO-SiO2-CaF2 slag

In this study, the effect of Na2O on the sintering and melting behavior of representative CaO-SiO2-CaF2 slag were synthetically investigated by TG-DSC, DIL, XRD, SEM, XPS, and BET. As expected, most shrinkage of CaO-SiO2-CaF2 slags with and without Na2O during the sintering process originated from solid-phase sintering, and the formation temperature of cuspidine as the sintering phase was reduced by Na2O to 550 degrees C. While Na2O also transformed Ca4Si2O7F2 to Ca2NaSiO4F at 650 degrees C-880 degrees C and caused unexpected volume expansion, owing to increased cell volume and corresponding pore expansion. Moreover, Na2O reduced the melting point of CaO-SiO2-CaF2 slag and promoted the volatilization of fluoride by changing the final phase before melting. (C) 2022 The Author(s). Published by Elsevier B.V.

Automated summary

In this study, the effect of Na2O on the sintering and melting behavior of CaO-SiO2-CaF2 slag was investigated. The results showed that Na2O reduced the formation temperature of cuspidine and caused volume expansion. Additionally, Na2O lowered the melting point of the slag and promoted fluoride volatilization.