Pressure and temperature dependence of the viscosity of a NaAlSi2O6 melt
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The viscosity of a silicate melt of composition NaAlSi2O6 was measured at pressures from 1.6 to 5.5 GPa and at temperatures from 1,350 to 1,880°C. We employed in situ falling sphere viscometry using X-ray radiography. We found that the viscosity of the NaAlSi2O6 melt decreased with increasing pressure up to 2 GPa. The pressure dependence of viscosity is diminished above 2 GPa. By using the relationship between the logarithm of viscosity and the reciprocal temperature, the activation energies for viscous flow were calculated to be 3.7 ± 0.4 × 102 and 3.7 ± 0.5 × 102 kJ/mol at 2.2 and 2.9 GPa, respectively.
KeywordsViscosity Silicate melt High pressure Radiography
The authors thank Dr. Ken-ichi Funakoshi at SPrign-8 for technical supports. The synchrotron radiation experiments were conducted at the Photon Factory, KEK (Proposal No. 2007S2–002). This work was partially supported by Grant-in-Aid for scientific research from the Japanese Ministry of Education, Culture, Sports, Science and Technology to A.S. (No. 17654102, 21684032 and 20103003) and to E.O. (No. 16075202 and 18104009).
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