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摘要
The sound velocities (nv(p), v(p), v(s)) and refractive index n of four haplogranitic glasses and melts have been measured as a function of temperature by Brillouin scattering spectroscopy. The measurements were conducted at GHz frequency, through the glass transition temperature (T-g), using both platelet and backscattering geometries. The compositions of the four haplogranites are based on the addition of similar to 5 wt% each of the components Li2O, F2O-1, Na2O, and K2O to a haplogranitic (HPG8) composition. Marked changes in slope and sign are observed in the temperature dependences of sound velocities (nv(p), v(p), v(s)) as a function of composition. The glass transition temperatures T-g of the haplogranite samples are determined from distinct slope changes of sound velocities (v(p) and v(s)) vs. temperature. The lithium-enriched glass has the lowest glass transition temperature (466 degrees C), while the potassic glass has the highest glass transition temperature (575 degrees C). The unrelaxed bulk moduli vary markedly with composition below the glass transition, as do their temperature dependencies: the bulk moduli of the F- and Na-rich glasses have positive shifts with temperature. For comparison, the shear moduli have relatively similar temperature dependences below T-g for different alkali contents. At temperatures above the glass transition, the temperature derivatives of the bulk moduli, which for these frequencies reflect the vibrational compressibilities of the liquids, shift to more negative values. However, the compositional range over which the bulk moduli undergo positive or small negative temperature shifts of the vibrational compressibility appears to extend to NBO/T ratios near 0.3-0.4, or spanning most haplogranite compositions.
- 出版日期2013-3
- 单位新疆大学
