Japan Geoscience Union Meeting 2014

Presentation information

Oral

Symbol S (Solid Earth Sciences) » S-MP Mineralogy & Petrology

[S-MP47_1PM2] Physics and Chemistry of Minerals

Thu. May 1, 2014 4:15 PM - 5:00 PM 422 (4F)

Convener:*Hiroki Okudera(School of Natural System, College of Science and Engineering), Atsushi Kyono(Graduate School of Life and Environmental Sciences, University of Tsukuba), Chair:Hiroshi Kojitani(Department of Chemistry, Faculty of Science, Gakushuin University)

4:30 PM - 4:45 PM

[SMP47-22] Temperature-dependent thermal expansivities of aluminum-free silicate melts and borosilicate melts

*Toru SUGAWARA1, Junki KATSUKI2, Satoshi YOSHIDA2, Jun MATSUOKA2, Kazuhiro MINAMI3, Eiji OCHI3 (1.Akita University, 2.The University of Shiga Prefecture, 3.Japan Nuclear Fuel Limited)

Keywords:silicate melt, thermal expansivity, densitometry

Thermal expansivities (dV/dT) of silicate melts are essential in a thermodynamic calculation of phase equilibira in magmatic system as a function of pressure and temperature and in a numerical simulation of flow and thermal structures in glass melting furnace. Previous studies have been suggested that the dV/dT of alumino-silicate melts (Lange, 1996; Potuzak et al., 2006) and magmatic silicate melts (Lange, 1997; Ghiorso and Kress, 2004) is a function of composition, but independent of temperature. On the other hand, it has been reported that the dV/dT of SiO2-TiO2-Na2O melt (Liu and Lange, 2001) and 50SiO2-25CaO-25MgO melt (Gottsmann and Dingwell, 2000) decrease with increasing temperature. Recently, we found that simulated-radioactive waste glass melt which has sodium-borosilicate composition also shows negative temperature-dependent dV/dT (Sugawara et al., 2013). We carried out density measurements for sodium-silicate melts ((100-x)SiO2-xNa2O, x=23 or 32.3 mol%), commercial soda-lime silicate melt (71SiO2-6MgO-9CaO-14Na2O, mol%) and borosilicate melts (66.6SiO2-yB2O3-(33.33-y)Na2O where y=8.3, 16.6, 25; 66.6SiO2-(12.5+z)B2O3-(4.2-z)Al2O3-zCaO-(16.7-z)Na2O where z=0 or 4.2 mol%). The temperature and compositional dependences of the dV/dT are discussed based on the new density data and the literature data. The high-temperature density (dHT) measurement has been made by double-bob Archimedean method between 1173K and 1665K. The glass samples were annealed around glass transition temperature (Tg) for 6-396 hours and quenched. Then the density of annealed glasses at 298K (d298) and linear thermal expansivity (dL/L) were determined by Archimedean method and TMA. respectively. The densities of supercooled melt around Tg (dTg) were calculated from the d298 and the dL/L of glasses. Then, molar volume as a function of temperature and the dV/dT of melts were obtained by combining the dTg and the dHT. The dV/dT values of all samples examined in this study show negative temperature dependence. In the sodium silicate melts, the temperature dependence of the dV/dT is remarkable when the SiO2 content increases from 50 to 67 mol%, while the dV/dT becomes close to zero as further increase in the SiO2 content. The negative temperature-dependent dV/dT observed in the 71SiO2-6MgO-9CaO-14Na2O melt can be reproduced by an additive sum of the dV/dT of 67.8SiO2-32.2Na2O, diopside (Gottsmann and Dingwell, 2000) and wollastonite (Potuzak et al., 2006) melts. High-temperature Raman spectroscopy for the SiO2-Na2O and SiO2-Na2O-MgO melts has been indicated that amount of Q4 species increases with increasing temperature and SiO2 and MgO contents (Maehara et al., 2004, 2005). Therefore, the temperature dependent dV/dT for the sodium-silicate, commercial soda-lime silicate and diopside melts can be rationalized by an increase of rigid Q4 species at high temperature. The temperature dependence of the dV/dT is most remarkable in the 66.6SiO2-8.3B2O3-25Na2O melt among the borosilicate melts. The dV/dT decreases with replacement of Na2O by B2O3 or CaO and of B2O3 by Al2O3, suggesting that partial molar dV/dT of B2O3 depends on temperature-induced coordination change of boron and their composition dependence (Wu and Stebbins, 2010). Acknowledgements: This work was a part of the research supported by Japan Nuclear Fuel Limited with Grant-in-Aid by the Ministry of Economy, Trade and Industry.