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Evaluating Composition Dependence in Surface Tension of Si–Ca–Na–O–F Reciprocal Oxide–fluoride Melts

2016; The Iron and Steel Institute of Japan; Volume: 56; Issue: 1 Linguagem: Inglês

10.2355/isijinternational.isijint-2015-472

1347-5460

Masanori Suzuki, Shota Tanaka, Masahito Hanao, Toshihiro Tanaka,

Advanced ceramic materials synthesis

Surface tension of molten ionic mixtures such as slag is an important physical property related directly to various surface or interfacial phenomena in high-temperature industrial processes. In particular, surface tension of oxide–fluoride melts is of interest to understand interfacial phenomena in continuous casting in steelmaking. However, the composition dependence of surface tension in reciprocal ionic melts has not been well understood because of its complexity related to the reciprocal reaction between input components in the melt. In this study, we measured the surface tension of reciprocal oxide–fluoride melts in a Si–Ca–Na–O–F multicomponent system, to evaluate its composition dependence. We used a maximum bubble pressure method to determine the surface tension of these melts with high accuracy. Our results indicate that (1) the surface tension of the SiO2–CaO melt decreases by NaF addition more steeply than by Na2O addition, and (2) the surface tension of the SiO2–CaO–CaF2 melt decreases with Na2O addition but depends on NaF formation because of the reciprocal reaction CaF2 + Na2O = CaO + 2 NaF. When this reaction is taken into account, the surface tension of the SiO2–CaO–CaF2–Na2O melt matches that of the SiO2–CaO–NaF melt with increased CaO concentration from the above melt composition.