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Effect of phase change on shock wave attenuation in GeO2

Liu, C. and Ahrens, T. J. and Brar, N. S. (2002) Effect of phase change on shock wave attenuation in GeO2. Journal of Applied Physics, 91 (11). pp. 9136-9146. ISSN 0021-8979. doi:10.1063/1.1469663.

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Stress-wave profiles in vitreous GeO2 induced by planar and spherical projectile impact were measured using piezoresistance gauges in the 4 to 18 GPa shock pressure range. The planar experiments demonstrate the response of vitreous GeO2. This response can be divided into three regimes: (1) An elastic shock regime with ramp 4 GPa Hugoniot elastic limit (HEL) precursor. Shock propagation velocity decreases from an initial longitudinal elastic wave speed of 3.5 to 2.8 km/s at 4 GPa. (2) A transition wave regime where the ramp wave is superimposed on the precursor with an additional amplitude of 0 to 2 GPa followed by a sharp increase in shock pressure achieving peak loading pressures of 8 to 14 GPa. Above 4 GPa the ramp wave velocity decreases to a value below 2.5 km/s (the speed of the bulk wave, at the HEL). (3) A shock wave achieving the final shock state forms when peak pressure is >6 GPa specified by linear shock-particle velocity relation D=0.917+1.71 u (km/s) over the 6-40 GPa range for an initial density of 3.655 g/cm(3). The Hugoniots of GeO2 and SiO2, both initially vitreous, are found to be virtually coincident if pressure in SiO2 is calculated by multiplying the GeO2 pressure by the ratio of the initial densities of vitreous GeO2 to fused SiO2. The volume axes are translated by aligning the specific volumes for onset and completion of the four- to six-fold coordination phase change. Although only limited spherical impactor spherically diverging shock experiments were conducted, our present results demonstrate (1) The supported elastic shock in fused SiO2 decays less rapidly than a linear elastic wave when elastic wave stress amplitude is higher than 4 GPa. A supported elastic precursor in vitreous GeO2 decays faster with radius than a linear elastic wave; (2) in GeO2 (vitreous) unsupported shock waves decay with peak pressure in a phase transition range (4-15 GPa) with propagation radius (r) as proportional tor(-3.35).

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Additional Information:© 2002 American Institute of Physics. Received 22 October 2001; accepted 22 February 2002. Research was supported by NSF, NASA, and ARO. We appreciate the experimental support for E. Gelle and M. Long. Contribution No. 8843, Division of Geological and Planetary Science, California Institute of Technology, Pasadena, California.
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Army Research Office (ARO)UNSPECIFIED
Subject Keywords:germanium compounds; germanate glasses; shock wave effects; elastic waves; high-pressure solid-state phase transformations; equations of state; glass
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Division og Geological and Planetary Sciences8843
Issue or Number:11
Record Number:CaltechAUTHORS:LIUjap02
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Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:2087
Deposited By: Tony Diaz
Deposited On:07 Mar 2006
Last Modified:08 Nov 2021 19:45

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