Estimation of viscosities in the CaO-SiO2 and CaO-Al2O3-SiO2 melt systems using high temperature hot stage microscopy

Research areas:

• Intérieurs planétaires (2011 - 2016)

Year:

2014

Authors:

• Yann Morizet
• Q. Alech

Journal:

PHYSICS AND CHEMISTRY OF GLASSES-EUROPEAN JOURNAL OF GLASS SCIENCE AND TECHNOLOGY PART B

Volume:

55

Number:

1

Pages:

41-48

Month:

February

ISSN:

1753-3562

BibTex:

@article{WOS:000333869100006, author = "Yann Morizet and Q. Alech", abstract = "Assessing the changes in melt viscosity as a function of temperature is an important topic for industrial processes and earth sciences. We present high temperature viscosity measurements for melts synthesised in the CaO-SiO2 and CaO-Al2O3-SiO2 systems. The range of covered compositions was chosen so as to investigate the possible structural (nonbridging oxygen/tetrahedra; NBO/T,) and chemical effects (various Al2O3 contents). We used an optical method developed in previous studies for determining the temperature corresponding to viscosities between log(eta/Pa s)=9 to 2. The range of measured temperature is between 1300 and 1900 K. We compared the obtained results to available viscosity models and previous viscosity measurements. The measured values are systematically higher than the predicted ones or previous results on similar compositions. The optical method although easy to use has limited accuracy explaining this difference. The observed viscosity changes are strongly correlated to the structural parameter NBO/T as suggested before. As the depolymerisation of the melt increases (NBO/T increases) the viscosity at a given temperature decreases. The introduction of Al2O3 (25 mol%) also produces a major decrease in the viscosity temperature suggesting an important structural role of Al atoms. We explain the effect of Al2O3 by two possible mechanisms: (1) a network modifying effect of Ca2+ in addition to the charge balancing effect in the surroundings of Al atoms and (2) a possible change in the Al coordination towards highly coordinated Al (Al-V or Al-VI) hence inducing a decrease in viscosity", extra = "PICL", issn = "1753-3562", journal = "PHYSICS AND CHEMISTRY OF GLASSES-EUROPEAN JOURNAL OF GLASS SCIENCE AND TECHNOLOGY PART B", month = "FEB", number = "1", pages = "41-48", title = "{E}stimation of viscosities in the {C}a{O}-{S}i{O}2 and {C}a{O}-{A}l2{O}3-{S}i{O}2 melt systems using high temperature hot stage microscopy", volume = "55", year = "2014", }

Abstract:

Assessing the changes in melt viscosity as a function of temperature is an important topic for industrial processes and earth sciences. We present high temperature viscosity measurements for melts synthesised in the CaO-SiO2 and CaO-Al2O3-SiO2 systems. The range of covered compositions was chosen so as to investigate the possible structural (nonbridging oxygen/tetrahedra; NBO/T,) and chemical effects (various Al2O3 contents). We used an optical method developed in previous studies for determining the temperature corresponding to viscosities between log(eta/Pa s)=9 to 2. The range of measured temperature is between 1300 and 1900 K. We compared the obtained results to available viscosity models and previous viscosity measurements. The measured values are systematically higher than the predicted ones or previous results on similar compositions. The optical method although easy to use has limited accuracy explaining this difference. The observed viscosity changes are strongly correlated to the structural parameter NBO/T as suggested before. As the depolymerisation of the melt increases (NBO/T increases) the viscosity at a given temperature decreases. The introduction of Al2O3 (25 mol%) also produces a major decrease in the viscosity temperature suggesting an important structural role of Al atoms. We explain the effect of Al2O3 by two possible mechanisms: (1) a network modifying effect of Ca2+ in addition to the charge balancing effect in the surroundings of Al atoms and (2) a possible change in the Al coordination towards highly coordinated Al (Al-V or Al-VI) hence inducing a decrease in viscosity