Elastic moduli of wadsleyite (β-Mg2SiO4) to 7 gigapascals and 837 kelvin

Science

Volumn 281, Issue 5377, 1998, Pages 675-677

  Li, Baosheng ^a   Liebermann, Robert C ^a   Weidner, Donald J ^a  

^a STONY BROOK UNIVERSITY   (United States)

Author keywords

[No Author keywords available]

Indexed keywords

MAGNESIUM SILICATE;

ACOUSTICS; ARTICLE; PRIORITY JOURNAL; SHEAR RATE; SOUND TRANSMISSION; VELOCITY; YOUNG MODULUS;

EID: 0032584710     PISSN: 00368075     EISSN: None     Source Type: Journal    
DOI: None     Document Type: Article

References (33)

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16. 3, 41° X-cut for S wave and 36° Y-cut for P wave) on the back of a WC anvil. A glass buffer rod was inserted between the WC anvil and the specimen. Precompressed boron-epoxy (4:1 weight % ratio) cubes were used as the pressure medium. The specimen was surrounded by a mixture of NaCl and BN (10:1 weight % ratio) inside a BN sleeve. Outside the BN sleeve was a cylindrical graphite furnace with graphite rings on both ends. Gold foils (2-μm thickness) were inserted between the WC anvil and the glass buffer rod and between the glass buffer rod and the sample to enhance the mechanical coupling. The perturbation to the travel times introduced by the gold foil between the buffer rod and the sample was corrected following the procedures of Niesler and Jackson [H. Niesler and I. Jackson, J. Acoust. Soc. Am. 86, 1573 (1989)]. The uncertainties in the corrected travel times are less than 0.4% at all pressures and temperatures. The sample pressures were calculated from x-ray spectra of NaCl with the Decker scale [D. L. Decker, J. Appl. Phy. 42, 3239 (1971)]. The uncertainties in calculated pressures are about 0.7%. The low shear strength of NaCl also provides a pseudo-hydrostatic stress environment for the sample at low temperatures, which becomes progressively more hydrostatic at elevated temperatures (28). The sample temperatures were measured from the thermocouple adjacent to the center of the sample.
17. 3, 41° X-cut for S wave and 36° Y-cut for P wave) on the back of a WC anvil. A glass buffer rod was inserted between the WC anvil and the specimen. Precompressed boron-epoxy (4:1 weight % ratio) cubes were used as the pressure medium. The specimen was surrounded by a mixture of NaCl and BN (10:1 weight % ratio) inside a BN sleeve. Outside the BN sleeve was a cylindrical graphite furnace with graphite rings on both ends. Gold foils (2-μm thickness) were inserted between the WC anvil and the glass buffer rod and between the glass buffer rod and the sample to enhance the mechanical coupling. The perturbation to the travel times introduced by the gold foil between the buffer rod and the sample was corrected following the procedures of Niesler and Jackson [H. Niesler and I. Jackson, J. Acoust. Soc. Am. 86, 1573 (1989)]. The uncertainties in the corrected travel times are less than 0.4% at all pressures and temperatures. The sample pressures were calculated from x-ray spectra of NaCl with the Decker scale [D. L. Decker, J. Appl. Phy. 42, 3239 (1971)]. The uncertainties in calculated pressures are about 0.7%. The low shear strength of NaCl also provides a pseudo-hydrostatic stress environment for the sample at low temperatures, which becomes progressively more hydrostatic at elevated temperatures (28). The sample temperatures were measured from the thermocouple adjacent to the center of the sample.
18. 3, 41° X-cut for S wave and 36° Y-cut for P wave) on the back of a WC anvil. A glass buffer rod was inserted between the WC anvil and the specimen. Precompressed boron-epoxy (4:1 weight % ratio) cubes were used as the pressure medium. The specimen was surrounded by a mixture of NaCl and BN (10:1 weight % ratio) inside a BN sleeve. Outside the BN sleeve was a cylindrical graphite furnace with graphite rings on both ends. Gold foils (2-μm thickness) were inserted between the WC anvil and the glass buffer rod and between the glass buffer rod and the sample to enhance the mechanical coupling. The perturbation to the travel times introduced by the gold foil between the buffer rod and the sample was corrected following the procedures of Niesler and Jackson [H. Niesler and I. Jackson, J. Acoust. Soc. Am. 86, 1573 (1989)]. The uncertainties in the corrected travel times are less than 0.4% at all pressures and temperatures. The sample pressures were calculated from x-ray spectra of NaCl with the Decker scale [D. L. Decker, J. Appl. Phy. 42, 3239 (1971)]. The uncertainties in calculated pressures are about 0.7%. The low shear strength of NaCl also provides a pseudo-hydrostatic stress environment for the sample at low temperatures, which becomes progressively more hydrostatic at elevated temperatures (28). The sample temperatures were measured from the thermocouple adjacent to the center of the sample.
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20. According to (28), the yield strength of NaCl is less than 0.05 GPa above 300°C, which is about the error in pressure in our measurement. Beyond 300°C in heating as well as on subsequent cooling, the sample is under a hydrostatic stress environment; therefore, the length change at these pressure and temperature conditions can be obtained from the cube root of the volume change. The propagated errors in the lengths are about 0.4%.
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27. The seismic velocity-depth profiles we used for comparison are in the following references. GCA: M. C. Walck, Geophys. J. R. Astron. Soc. 76, 697 (1984); SNA and TNA: S. Grand, and D. Helmberger, ibid., p. 399; and SZ5: L. V. LeFevre and D. Helmberger, J. Geophy. Res. 94, 17749 (1989).
28. The seismic velocity-depth profiles we used for comparison are in the following references. GCA: M. C. Walck, Geophys. J. R. Astron. Soc. 76, 697 (1984); SNA and TNA: S. Grand, and D. Helmberger, ibid., p. 399; and SZ5: L. V. LeFevre and D. Helmberger, J. Geophy. Res. 94, 17749 (1989).
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33. We thank all those who contributed to the implementation of these ultrasonic experiments in SAM 85 on the X17B1 beamline of the NSLS at Brookhaven National Laboratory and J. B. Hastings and D. P. Siddons at the NSLS for their technical support. Support was from the State University of New York at Stony Brook and from the NSF Science and Technology Center for High Pressure Research (grant EAR89-20239 and NSF grants EAR93-04502 and EAR96-14612 to R.C.L). This is Mineral Physics Institute contribution number 229.