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Effect of fluorine and CaO/Al 2 O 3 mass ratio on the viscosity and structure of CaO–Al 2 O 3 ‐based mold fluxes
Author(s) -
Shao Hanqing,
Gao Erzhuo,
Wang Wanlin,
Zhang Lei
Publication year - 2019
Publication title -
journal of the american ceramic society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.9
H-Index - 196
eISSN - 1551-2916
pISSN - 0002-7820
DOI - 10.1111/jace.16322
Subject(s) - fluorine , viscosity , depolymerization , magic angle spinning , raman spectroscopy , chemistry , analytical chemistry (journal) , slag (welding) , ionic bonding , ion , materials science , mineralogy , nuclear magnetic resonance spectroscopy , metallurgy , stereochemistry , organic chemistry , composite material , optics , physics
The effect of CaO/Al 2 O 3 mass ratio (C/A) and fluorine content on the viscosity and structure of CaO–Al 2 O 3 ‐based mold fluxes has been researched in this paper. The viscosity results indicated that increasing fluorine only slightly decreases the viscosity of the slag melt, and higher C/A is also observed to decrease the viscosity of molten slag when the C/A changes from 1.3 to 1.7. Structural analysis of the as‐quenched fluxes using the Raman spectroscopy showed that the amounts of Al–O 0 and Si–O–Al structural units all decrease with higher fluorine content and C/A, indicating that a depolymerization of the molten structure is occurring. The results of 27 Al and 19 F magic angle spinning nuclear magnetic resonance showed that fluorine tends to participate in the network structure and coordinate with Al 3+ ions to form complex ionic clusters. The results suggested that the role of fluorine in the CaO–Al 2 O 3 ‐based slag system is different from the traditional slag system in which fluorine only acts as a diluent, thus reducing the effect of fluorine on lowering the viscosity. In addition, the coordination environment of Al 3+ ions can be simplified by higher C/A through promoting the generation of [AlO 4 ] − tetrahedral structures. Besides, the free O 2− ions provided by excess CaO would break the Al–O 0 bonds and further depolymerize the network structure, thereby decrease the viscosity.