Viscosity model for aluminosilicate melt

Abstract

The structurally based viscosity model proposed in our previous study is extended to include more components, e.g. SiO2, Al2O3, FeO, MnO, MgO, CaO, Na2O and K2O. A simple method is proposed to calculate the numbers of different types of oxygen ions classified by the different cations they bonded with, which is used to characterize the influence of composition on viscosity. When dealing with the aluminosilicate melts containing several basic oxides, the priority order is established for different cations for charge compensating Al3+ ions, according to the coulombic force between cation and oxygen anion. It is indicated that basic oxides have two paradox influences on viscosity: basic oxide with a higher basicity decreases viscosity more greatly by forming weaker non-bridging oxygen bond; while it increases viscosity more greatly by forming stronger bridging oxygen bond in tetrahedron after charge compensating Al3+ ion. The present model can extrapolate its application range to the system without SiO2. Furthermore, it could also give a satisfy interpretation to the abnormal phenomenon that viscosity increases when adding K2O to CaO-Al2O3-SiO2 melt within a certain composition range

Measuring and Modeling Viscosity of CaO-Al2O3-SiO2(-K2O) Melt

“…Therefore, as adding K 2 O, K + ion will substitute the position of Ca 2+ ion to compensate Al 3+ ion because of the high priority of K + ion. [6] The addition of K 2 O may lead to the following two changes: more nonbridging oxygen will be formed because of the increase of the total content of basic oxides, which decreases viscosity; bridging oxygen O Al;Ca is gradually changed to O Al;K (schematic diagram is shown in Figure 10), which increases viscosity because the chemical bonds around O Al;K are stronger than those around O Al;Ca (a Al;Ca ¼ 4:996>a Al;K ¼ 4:156). When the content of K 2 O is low, the latter factor may be dominated; thus, the viscosity exhibits increasing tendency with the addition of K 2 O.…”

“…Therefore, the viscosity first increases and then decreases with the addition of K 2 (where Q is the valence of cation and r is the radii). [6] The smaller the value of ions. [6] The substitution reaction of K + ion for Ca 2+ ion is infinite.…”

“…[6] The smaller the value of ions. [6] The substitution reaction of K + ion for Ca 2+ ion is infinite. At K 2 O/Al 2 O 3 = 1, all the Al 3+ ions are compensated by K + ions, and the number of O Al;K achieves the maximum, so does the viscosity.…”

“…Therefore, viscosity increases with increasing content of K 2 O. The viscosity model developed in our previous papers [3][4][5][6] will be used to estimate the viscosity of the compositions studied in this work and compare with the measured values. The detailed descriptions of the model can be found in the early publication, and only a brief introduction about the application to CaO-SiO 2 -Al 2 O 3 -K 2 O system will be given.…”

“…Furthermore, the measured viscosity data are compared with the estimated values calculated by the viscosity model proposed in our previous paper. [3][4][5][6] …”