期刊
JOURNAL OF APPLIED PHYSICS
卷 107, 期 12, 页码 -出版社
AMER INST PHYSICS
DOI: 10.1063/1.3452382
关键词
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资金
- Ministry of Education, Culture, Sports, Science and Technology [19204054]
- Grants-in-Aid for Scientific Research [19204054] Funding Source: KAKEN
The elastic compressional (P) and shear (S) wave velocities of silica glass at simultaneous high pressures and high temperatures were measured using a combination of ultrasonic interferometry, in situ synchrotron x-ray diffraction, and radiographic techniques in a large-volume Kawai-type multianvil apparatus. We found no first-order amorphous-amorphous transformation throughout the pressure and temperature conditions between 2 and 5 GPa and up to 1173 K, contrary to previous studies suggested by piston cylinder experiments or molecular dynamics simulations. For each of the 650 and 800 K isothermal runs, the P and S wave velocities initially decreased with increasing pressure, reaching minimum values at around 3-4 GPa, followed by increases with pressure up to 6.1 GPa; on successive decompression to ambient pressure, both velocities changed irreversibly due to permanent densification, and no minima were observed in both velocities. We also found that, in a second compression-decompression cycle at 800 K, the densified silica glass was compressed reversibly (elastically) within errors without further irreversible densification. Using the measured P and S wave velocities in such reversible (elastic) compression regions as a function of pressure, we found the density of silica glass increases with temperature from 300 to 800 K at all the measured pressure range up to 6.1 GPa, providing a direct evidence of a negative thermal expansion of silica glass at high pressures. (C) 2010 American Institute of Physics. [doi:10.1063/1.3452382]
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