Structural investigations of CaO–CaF2–SiO2–Si3N4 based glasses by Raman spectroscopy and XPS considering its application to continuous casting of steels

•Degree of polymerization (DP) of CaO–CaF2–SiO2–Si3N4 glasses was investigated.•DP of CaO–CaF2–SiO2–Si3N4 based glass increased with increasing nitrogen.•Nitrogen is incorporated with non-bridging oxygen, leading to increasing DP.•Addition of nitrogen will bring enhanced shear thinning property.

Structural analysis of CaO–CaF2–SiO2–Si3N4 based glass was conducted in order to understand its viscoelastic properties. CaO–CaF2–SiO2–Si3N4 based glass has been adapted in various industries because a small amount of nitrogen incorporation leads to enhancing many properties such as fracture toughness, viscosity and chemical durability. Recently, few metallurgists have begun to use CaO–CaF2–SiO2–Si3N4 based glass as a lubricant of continuous casting process of steel in order to maximize its viscoelastic property by controlling degree of polymerization (DP). The present study provides structural understanding of CaO–CaF2–SiO2–Si3N4 based glass, specifically designed for the continuous casting process of steel by Raman spectroscopy and XPS. With Raman spectroscopy, the degree of polymerization (DP) was evaluated by the Q3/Q2 ratio. The qualitative analysis of nitrogen and non-bridging oxygen was conducted by XPS within a range between 0.1 and 6 wt.% of nitrogen. According to the results, the introduced nitrogen was incorporated with non-bridging oxygen of silicate network units, resulting in increase on degree polymerization (DP) of silicate network units. Such structural changes would potentially enhance shear thinning property of CaO–CaF2–SiO2–Si3N4 based glass, resulting in a positive influence on continuous casting process of steel.

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