article posted 02 Feb 2016
Toru Sugawara Toru Sugawara received his PhD in Earth and Planetary Science from Tokyo Institute of Technology in 2001.
He has worked as postdoctoral fellow at the Department of Chemistry, Gakushuin University (2001-2003) and Institute for Study of the Earth’s Interior,
Okayama University (2003-2006), as engineer at ULVAC-RIKO, Inc. (Yokohama, Japan) which is manufacturer of thermal analysis and calorimeter
instruments (2006-2007) and as assistant professor at the Center of Glass Science, University of Shiga Prefecture (2007-2011). He has been associate
professor at the Center for Engineering Science, Akita University (Japan) since 2011. His research interest ranges from earth science to metallurgy and
glass engineering. Current research activities include: magma generation in island arc volcano; calorimetry and thermodynamics of magmatic liquids,
commercial glass and glass melts; analysis of phase separation and crystallization of high-level radioactive waste glass; development of calorimeter apparatus for molten oxide.
Heat capacity of alkaline-earth alumino borosilicate glasses and liquids
Toru Sugawara*, Toshiaki Ohira
Center for Engineering Science, Akita University,1-1 Tegata Gakuenmachi, Akita 010-8502, Japan
Isobaric heat capacity (Cp
) of glass melts is required to simulate chemical equilibrium and flow and heat transfer process in glass melting furnace.
Alkaline-earth alumino borosilicate glasses have been widely used for glass-reinforced plastics (E-glass) and glass substrates of flat panel display (FPD glass),
whereas their heat capacity data is very limited. We carried out new calorimetric measurements for alkaline-earth alumino borosilicate glasses, and considered
the effect of temperature and composition on the Cp. The heat capacities for two commercial glasses and thirteen alkaline-earth borosilicate glasses were
determined by differential scanning calorimetry and drop calorimetry between 300 to 1877K. Chemical compositions of synthetic glasses range
, 12-4mol% B2
, 12-0mol% Al2
and 45-8mol% RO (R=Mg, Ca, Sr and Ba).
The results are shown in Figure 1. The heat capacity of all glasses approaches to Dulong-Petit limit (3R) at their glass transition temperatures (T
Configuration heat capacity (Cp(liquid)-Cp
(glass)) at mTg increases with deceasing SiO2 content.
Partial molar heat capacities of Al2O3 and B2O3 for glass and liquid (Cp(x,y), x=component, y=phase)
were determined by combining measured Cp and previously reported partial molar heat capacities of oxide components (Richet and Bottinga, 1985; Richet, 1987).
The Cp(Al2O3, liquid) increases with increasing field strength of alkaline-earth cation, R. The Cp(B2O3, liquid)
depends on temperature and SiO22 and Al2O3 contents at low temperature, while it approaches constant value (120-140 J/mol-K)
with increasing temperature. This value is close to Cp of pure B2O3 liquid (128 J/mol-K). These facts suggest that configurational
heat capacity of borosilicate liquid is related to the change in coordination number of boron. The Cp(B2O3, glass) determined by the analysis is consistent with Cp of pure
B2O3 glass, indicating that vibrational heat capacity of borosilicate glass can be expressed by additive function of Cp(x, glass).
The heat capacities for E-glass and FPD glass calculated by the partial molar Cp’s are in good agreement with their measured values (Figure 2).
The Cp(B2O3, liquid) and Cp(Al2O3, liquid) in conjunction
with Cp(x, liquid) for other oxide components (Richet and Bottinga, 1985) can be used to estimate heat capacity of alkaline-earth borosilicate liquids.