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Effect of CaF 2 , B 2 O 3 and the CaO/SiO 2 mass ratio on the viscosity and structure of B 2 O 3 ‐containing calcium‐silicate‐based melts
Author(s) -
Kim Gi Hyun,
Sohn Il
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.16526
Subject(s) - depolymerization , activation energy , viscosity , analytical chemistry (journal) , raman spectroscopy , chemistry , crystallization , reduced viscosity , mineralogy , materials science , polymer chemistry , chromatography , composite material , physics , organic chemistry , optics
The relationship between the viscosity and structure of B 2 O 3 ‐containing calcium‐silicate‐based mold fluxes and the effects of fluidizers including CaF 2 , CaO, and B 2 O 3 on the viscosity and their correlation with the structural aspects were studied using a rheometer with Fourier transformation infrared and Raman spectroscopy. The viscosity decreased with increasing CaF 2 addition up to 28 wt% at a fixed CaO/SiO 2 ratio of 0.3, which was related to depolymerization. Furthermore, CaF 2 addition also affected the apparent activation energy for viscous flow, which decreased with increasing CaF 2 content to 105.1 from 151.1 kJ/mol. At higher C/S ratios, the viscosity decreased in the presence of greater Ca 2+ and O 2− supplied from CaO, which subsequently increased the activation energy to 149.7 from 122.0 kJ/mol. With regard to the B 2 O 3 ‐melt, polymerization of the network structure was observed by comparing the B 2 O 3 ‐free to 4.4 wt% B 2 O 3 content. However, the viscosity was relatively constant with increasing B 2 O 3 addition. However, the viscosity decreased due to greater simplification of the network structure above 4.4 wt% B 2 O 3 . The break temperature decreased with greater B 2 O 3 addition as the crystallization was inhibited. Furthermore, the apparent activation energy decreased as depolymerization of the network structures occurred above 4.4 wt% B 2 O 3 .