The viscosity effect of TiO
2
on
soda‐lime‐silicate bearing glass
Stefan Karlsson
1
1
RISE Research Institutes of Sweden, Glass section, SE‐351 96 Växjö, Sweden
Fig. 2: Experimental setup for the high temperature rotational viscometer.
Fig. 3: Viscosity‐temperature curve as determined from the Angell‐Rao equation,
shown as an inset in the figure. Fig. 4: The Angell‐plot giving the liquid fragility.
Introduction
TiO2 is an interesting component for glassy materials, perhaps in particular for its effect on the optical properties [1] but also for its effect on the mechanical properties [2]. Its effect on the viscosity has previously been studied by Bouhifd et al. [3] in the ternary alkali‐titanosilicate glass system, showing it has a slight suppressing effect on the viscosity. Here the TiO2 and its effect in the quaternary titania‐soda‐lime‐silicate glass system is studied, which can be used as a model for a wide range of technical glasses. Two series were studied, denoted 2nd (triangles) and 3rd series (circles) in [1, 2], the 2nd series is TiO
2 replacing SiO2 and in the 3rd CaO is
being replaced by TiO2. It is know from previous studies [1, 2] that a structural change of TiO2 in these glass series occurs with increasing TiO2 content where TiO5 polyhedra are also formed in addition to the TiO4 polyhedra [2].
Acknowledgement
Contact
RISE Research Institutes of Sweden
Built Environment Division, Glass Section
Stefan.Karlsson@ri.se
+46 10 516 63 574
Conclusions
As TiO2 is replacing SiO2 it has a slight suppressing effect on the viscosity until the limit when Na2O/TiO2 ratio is less than 2, indicating a transformation of the structure of TiO2, a remarkable increase in the fragility and viscosity is observed for the calculated low temperature region. The change is not as evident for the high‐ temperature region. CaO replaced by TiO2 gives almost no effect on the viscosity, however, as it approaches Na2O/TiO2≈2 it tends to crystallize at temperatures of 1000‐1050 °C.
Experimental
High temperature viscosity was measured using a rotational viscometer manufactured by Bohlin Reologi AB. The apparatus and measurement procedure is described in ASTM C965‐96. The viscometer was calibrated using a soda‐lime‐ silicate type container glass with viscosities in the range of η = log 2‐5 dPa∙s. Repeated control measurements of a non‐lead crystal glass throughout the previous decade have shown that the viscometer system has an error of ±30 °C at η = log 2 dPa∙s and ±10 °C at η = log 5 dPa∙s. The entire viscosity‐temperature curve were fitted to the Angell‐Rao equation [4]. The fragility index was calculated according to the method of Angell and thermodynamic data were extracted using the method of Ojovan [5].
References
1. Karlsson, S., et al., Opt. Mater. Express, 2016. 6(4): p. 1198‐1216. DOI: 10.1364/ome.6.001198.
2. Limbach, R., et al., J. Non‐Cryst. Solids, 2017. 471: p. 6‐18. DOI: 10.1016/j.jnoncrysol.2017.04.013.
3. Ali Bouhifd, M., et al., Geochim. Cosmochim. acta, 1999. 63(16): p. 2429‐2437. DOI: 10.1016/S0016‐7037(99)00145‐3.
4. Angell, C.A. and K.J. Rao,. J. Chem. Phys., 1972. 57(1): p. 470‐481. DOI: 10.1063/1.1677987. 5. Ojovan, M.I., Int. J. Appl. Glass Sci., 2014. 5(1): p. 22‐25. DOI: 10.1111/ijag.12045.
Grant No.: 2018‐00707
Liquid fragility
0
log
log
A
exp
B
C
T
log
/
g g T Td
m
d T T
Thermodynamic properties
Spec. Hm Hd Sd Ti11 179.9 283.6 418.1 Ti22 181.9 286.5 425.7 Ti23 178.9 282.1 426.3 Ti24 180.2 283.1 432.9 Ti25 178.9 265.6 419.1 Ti26 181.3 721.5 868.9 Ti27 186.4 669.3 830.4 Ti33 177.1 319.2 452.7 Ti34 175.4 312.3 446.2 Ti35 173.9 261.4 395.5 Ti37 169.8 325.9 460.4 Using the Ojovan method [5] thermodynamicproperties were extracted from the viscosity‐ temperature curves. The enthalpy of motion (Hm) and the entalphy of formation (Hd) as well as the entropy of formation (Sd) were determined. Hm was determined from the tangent line between lg η = 2 and 3, it showed a relatively constant trend for the 2nd series while it is linearly
decreasing in the 3rd series. Hd and Sd, were determined from the tangent line between lg η = 14 and 15 and these show a relatively constant trend for 2nd series apart from the samples Ti26 and Ti27 which are significantly higher. The 3rd
series show an increase and then minimum for the sample Ti35. The results harmonize well with the liquid fragility data determined according to Angell.
Tab. 1: Thermodynamic properties, enthalpy of motion (Hm), enthalpy of formation (Hd) and entropy of formation (Sd).
