Amphoteric behavior of alumina in viscous flow and structure of CaO-SiO2 (-MgO)-Al2O3 slags

Joo Hyun Park, Dong Joon Min, Hyo Seok Song

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Abstract

The viscosity of CaO-SiO2 (-MgO)-Al2O3 slags was measured to clarify the effects of Al2O3 and MgO on the structure and viscous flow of molten slags at high temperatures. Furthermore, the infrared spectra of the quenched slags were analyzed to understand the structural role of Al2O3 in the polymerization or depolymerization of silicate network. The Al2O3 behaves as an amphoteric oxide with the composition of slags; that is, the alumina behaves as a network former up to about 10 mass pet Al2O3, while it acts as a network modifier, in parts, in the composition greater than 10 mass pet Al2O3. This amphoteric role of Al2O 3 in the viscous flow of molten slags at the Newtonian flow region was diminished by the coexistence of MgO. The effect of Al2O 3 on the viscosity increase can be understood based on an increase in the degree of polymerization (DOP) by the incorporation of the [AlO 4]-tetrahedra into the [SiO4]-tetrahedral units, and this was confirmed by the infrared (IR) spectra of the quenched slags. The influence of alumina on the viscosity decrease can be explained on the basis of a decrease in the DOP by the increase in the relative fraction of the [AlO 6]-octahedral units. The relative intensity of the IR bands for the [SiO4]-tetrahedra with low NBO/Si decreased, while that of the IR bands for [SiO4]-tetrahedra with high NBO/Si increased with increasing Al2O3 content greater than the critical point, i.e., about 10 mass pet in the present systems. The variations of the activity coefficient of slag components with composition indirectly supported those of viscosity and structure of the aluminosilicate melts.

Original languageEnglish
Pages (from-to)269-275
Number of pages7
JournalMetallurgical and Materials Transactions B: Process Metallurgy and Materials Processing Science
Volume35
Issue number2
DOIs
Publication statusPublished - 2004 Jan 1

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Aluminum Oxide
slags
viscous flow
Viscous flow
Slags
Alumina
aluminum oxides
tetrahedrons
Viscosity
viscosity
Infrared radiation
polymerization
Polymerization
Molten materials
infrared spectra
Chemical analysis
Newtonian flow
depolymerization
Silicates
Depolymerization

All Science Journal Classification (ASJC) codes

  • Condensed Matter Physics
  • Mechanics of Materials
  • Metals and Alloys
  • Materials Chemistry

Cite this

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title = "Amphoteric behavior of alumina in viscous flow and structure of CaO-SiO2 (-MgO)-Al2O3 slags",
abstract = "The viscosity of CaO-SiO2 (-MgO)-Al2O3 slags was measured to clarify the effects of Al2O3 and MgO on the structure and viscous flow of molten slags at high temperatures. Furthermore, the infrared spectra of the quenched slags were analyzed to understand the structural role of Al2O3 in the polymerization or depolymerization of silicate network. The Al2O3 behaves as an amphoteric oxide with the composition of slags; that is, the alumina behaves as a network former up to about 10 mass pet Al2O3, while it acts as a network modifier, in parts, in the composition greater than 10 mass pet Al2O3. This amphoteric role of Al2O 3 in the viscous flow of molten slags at the Newtonian flow region was diminished by the coexistence of MgO. The effect of Al2O 3 on the viscosity increase can be understood based on an increase in the degree of polymerization (DOP) by the incorporation of the [AlO 4]-tetrahedra into the [SiO4]-tetrahedral units, and this was confirmed by the infrared (IR) spectra of the quenched slags. The influence of alumina on the viscosity decrease can be explained on the basis of a decrease in the DOP by the increase in the relative fraction of the [AlO 6]-octahedral units. The relative intensity of the IR bands for the [SiO4]-tetrahedra with low NBO/Si decreased, while that of the IR bands for [SiO4]-tetrahedra with high NBO/Si increased with increasing Al2O3 content greater than the critical point, i.e., about 10 mass pet in the present systems. The variations of the activity coefficient of slag components with composition indirectly supported those of viscosity and structure of the aluminosilicate melts.",
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AU - Park, Joo Hyun

AU - Min, Dong Joon

AU - Song, Hyo Seok

PY - 2004/1/1

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N2 - The viscosity of CaO-SiO2 (-MgO)-Al2O3 slags was measured to clarify the effects of Al2O3 and MgO on the structure and viscous flow of molten slags at high temperatures. Furthermore, the infrared spectra of the quenched slags were analyzed to understand the structural role of Al2O3 in the polymerization or depolymerization of silicate network. The Al2O3 behaves as an amphoteric oxide with the composition of slags; that is, the alumina behaves as a network former up to about 10 mass pet Al2O3, while it acts as a network modifier, in parts, in the composition greater than 10 mass pet Al2O3. This amphoteric role of Al2O 3 in the viscous flow of molten slags at the Newtonian flow region was diminished by the coexistence of MgO. The effect of Al2O 3 on the viscosity increase can be understood based on an increase in the degree of polymerization (DOP) by the incorporation of the [AlO 4]-tetrahedra into the [SiO4]-tetrahedral units, and this was confirmed by the infrared (IR) spectra of the quenched slags. The influence of alumina on the viscosity decrease can be explained on the basis of a decrease in the DOP by the increase in the relative fraction of the [AlO 6]-octahedral units. The relative intensity of the IR bands for the [SiO4]-tetrahedra with low NBO/Si decreased, while that of the IR bands for [SiO4]-tetrahedra with high NBO/Si increased with increasing Al2O3 content greater than the critical point, i.e., about 10 mass pet in the present systems. The variations of the activity coefficient of slag components with composition indirectly supported those of viscosity and structure of the aluminosilicate melts.

AB - The viscosity of CaO-SiO2 (-MgO)-Al2O3 slags was measured to clarify the effects of Al2O3 and MgO on the structure and viscous flow of molten slags at high temperatures. Furthermore, the infrared spectra of the quenched slags were analyzed to understand the structural role of Al2O3 in the polymerization or depolymerization of silicate network. The Al2O3 behaves as an amphoteric oxide with the composition of slags; that is, the alumina behaves as a network former up to about 10 mass pet Al2O3, while it acts as a network modifier, in parts, in the composition greater than 10 mass pet Al2O3. This amphoteric role of Al2O 3 in the viscous flow of molten slags at the Newtonian flow region was diminished by the coexistence of MgO. The effect of Al2O 3 on the viscosity increase can be understood based on an increase in the degree of polymerization (DOP) by the incorporation of the [AlO 4]-tetrahedra into the [SiO4]-tetrahedral units, and this was confirmed by the infrared (IR) spectra of the quenched slags. The influence of alumina on the viscosity decrease can be explained on the basis of a decrease in the DOP by the increase in the relative fraction of the [AlO 6]-octahedral units. The relative intensity of the IR bands for the [SiO4]-tetrahedra with low NBO/Si decreased, while that of the IR bands for [SiO4]-tetrahedra with high NBO/Si increased with increasing Al2O3 content greater than the critical point, i.e., about 10 mass pet in the present systems. The variations of the activity coefficient of slag components with composition indirectly supported those of viscosity and structure of the aluminosilicate melts.

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