Substitutional effect of Na 2 O with K 2 O on the viscosity and structure of CaO-SiO 2 -CaF 2 -based mold flux systems

Min Seok Seo, Il Sohn

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Abstract

The effect of the substitution of Na 2 O with K 2 O on the viscosity and structure of molten CaO-SiO 2 -CaF 2 -based mold fluxes containing alkali-oxides at high temperatures has been studied. The CaO/SiO 2 mass ratio (C/S) and CaF 2 were fixed at 0.8 and 10 mass pct., respectively. The total alkali-oxide was fixed at 20 mass pct. By systematically substituting the Na 2 O with K 2 O, the K 2 O/(Na 2 O + K 2 O) mass ratio was modified between 0.0 and 1.0. Using the rotating spindle method to measure the viscosity at high temperatures, the viscosity was found to increase with higher K 2 O/(Na 2 O + K 2 O). From the slope of the temperature dependence of the viscosity, an apparent activation energy was calculated and increased with higher K 2 O/(Na 2 O + K 2 O), from 96 to 154 kJ/mol, due to the cation size effect on the resistance to shearing. Using Raman spectroscopy of as-quenched fluxes, the mole fraction of Q 3 was found to increase, while the mole fractions of Q 2 and Q 0 decreased with higher K 2 O/(Na 2 O + K 2 O). The nonbridged oxygen per silicon cation (NBO/Si) decreased from 1.97 to 1.58 with increasing K 2 O/(Na 2 O + K 2 O), suggesting greater complexity of the flux structure with higher K 2 O/(Na 2 O + K 2 O), resulting in a higher viscosity.

Original languageEnglish
JournalJournal of the American Ceramic Society
DOIs
Publication statusPublished - 2019 Jan 1

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Viscosity
Fluxes
Alkalies
Oxides
Cations
Positive ions
Silicon
Shearing
Temperature
Raman spectroscopy
Molten materials
Substitution reactions
Activation energy
Oxygen

All Science Journal Classification (ASJC) codes

  • Ceramics and Composites
  • Materials Chemistry

Cite this

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title = "Substitutional effect of Na 2 O with K 2 O on the viscosity and structure of CaO-SiO 2 -CaF 2 -based mold flux systems",
abstract = "The effect of the substitution of Na 2 O with K 2 O on the viscosity and structure of molten CaO-SiO 2 -CaF 2 -based mold fluxes containing alkali-oxides at high temperatures has been studied. The CaO/SiO 2 mass ratio (C/S) and CaF 2 were fixed at 0.8 and 10 mass pct., respectively. The total alkali-oxide was fixed at 20 mass pct. By systematically substituting the Na 2 O with K 2 O, the K 2 O/(Na 2 O + K 2 O) mass ratio was modified between 0.0 and 1.0. Using the rotating spindle method to measure the viscosity at high temperatures, the viscosity was found to increase with higher K 2 O/(Na 2 O + K 2 O). From the slope of the temperature dependence of the viscosity, an apparent activation energy was calculated and increased with higher K 2 O/(Na 2 O + K 2 O), from 96 to 154 kJ/mol, due to the cation size effect on the resistance to shearing. Using Raman spectroscopy of as-quenched fluxes, the mole fraction of Q 3 was found to increase, while the mole fractions of Q 2 and Q 0 decreased with higher K 2 O/(Na 2 O + K 2 O). The nonbridged oxygen per silicon cation (NBO/Si) decreased from 1.97 to 1.58 with increasing K 2 O/(Na 2 O + K 2 O), suggesting greater complexity of the flux structure with higher K 2 O/(Na 2 O + K 2 O), resulting in a higher viscosity.",
author = "Seo, {Min Seok} and Il Sohn",
year = "2019",
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AU - Seo, Min Seok

AU - Sohn, Il

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N2 - The effect of the substitution of Na 2 O with K 2 O on the viscosity and structure of molten CaO-SiO 2 -CaF 2 -based mold fluxes containing alkali-oxides at high temperatures has been studied. The CaO/SiO 2 mass ratio (C/S) and CaF 2 were fixed at 0.8 and 10 mass pct., respectively. The total alkali-oxide was fixed at 20 mass pct. By systematically substituting the Na 2 O with K 2 O, the K 2 O/(Na 2 O + K 2 O) mass ratio was modified between 0.0 and 1.0. Using the rotating spindle method to measure the viscosity at high temperatures, the viscosity was found to increase with higher K 2 O/(Na 2 O + K 2 O). From the slope of the temperature dependence of the viscosity, an apparent activation energy was calculated and increased with higher K 2 O/(Na 2 O + K 2 O), from 96 to 154 kJ/mol, due to the cation size effect on the resistance to shearing. Using Raman spectroscopy of as-quenched fluxes, the mole fraction of Q 3 was found to increase, while the mole fractions of Q 2 and Q 0 decreased with higher K 2 O/(Na 2 O + K 2 O). The nonbridged oxygen per silicon cation (NBO/Si) decreased from 1.97 to 1.58 with increasing K 2 O/(Na 2 O + K 2 O), suggesting greater complexity of the flux structure with higher K 2 O/(Na 2 O + K 2 O), resulting in a higher viscosity.

AB - The effect of the substitution of Na 2 O with K 2 O on the viscosity and structure of molten CaO-SiO 2 -CaF 2 -based mold fluxes containing alkali-oxides at high temperatures has been studied. The CaO/SiO 2 mass ratio (C/S) and CaF 2 were fixed at 0.8 and 10 mass pct., respectively. The total alkali-oxide was fixed at 20 mass pct. By systematically substituting the Na 2 O with K 2 O, the K 2 O/(Na 2 O + K 2 O) mass ratio was modified between 0.0 and 1.0. Using the rotating spindle method to measure the viscosity at high temperatures, the viscosity was found to increase with higher K 2 O/(Na 2 O + K 2 O). From the slope of the temperature dependence of the viscosity, an apparent activation energy was calculated and increased with higher K 2 O/(Na 2 O + K 2 O), from 96 to 154 kJ/mol, due to the cation size effect on the resistance to shearing. Using Raman spectroscopy of as-quenched fluxes, the mole fraction of Q 3 was found to increase, while the mole fractions of Q 2 and Q 0 decreased with higher K 2 O/(Na 2 O + K 2 O). The nonbridged oxygen per silicon cation (NBO/Si) decreased from 1.97 to 1.58 with increasing K 2 O/(Na 2 O + K 2 O), suggesting greater complexity of the flux structure with higher K 2 O/(Na 2 O + K 2 O), resulting in a higher viscosity.

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