Effect of phase change on shock wave attenuation in GeO2

Abstract

Stress-wave profiles in vitreous GeO 2 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 GeO 2 . This response can be divided into three regimes: ͑1͒ An elastic shock regime with ramp 4 GPa Hugoniot elastic limit ͑HEL͒ precursor. Shock propagation velocity decreases from an initial longitudinal elastic wave speed of 3.5 to 2.8 km/s at 4 GPa. ͑2͒ 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 HEL͒. ͑3͒ A shock wave achieving the final shock state forms when peak pressure is Ͼ6 GPa specified by linear shock-particle velocity relation D ϭ0.917ϩ1.71 u ͑km/s͒ over the 6 -40 GPa range for an initial density of 3.655 g/cm 3 . The Hugoniots of GeO 2 and SiO 2 , both initially vitreous, are found to be virtually coincident if pressure in SiO 2 is calculated by multiplying the GeO 2 pressure by the ratio of the initial densities of vitreous GeO 2 to fused SiO 2 . 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 ͑1͒ The supported elastic shock in fused SiO 2 decays less rapidly than a linear elastic wave when elastic wave stress amplitude is higher than 4 GPa. A supported elastic precursor in vitreous GeO 2 decays faster with radius than a linear elastic wave; ͑2͒ in GeO 2 ͑vitreous͒ unsupported shock waves decay with peak pressure in a phase transition range ͑4 -15 GPa͒ with propagation radius ͑r͒ as ϰr Ϫ3.35 .

Equation of state of theα−PbO2andPa3¯-type phases ofDutta1, White2, Greenberg3 et al. 2018Phys. Rev. B

“…The crystalline and vitreous forms of germania, GeO 2 have been extensively studied using a wide range of static and dynamic compression techniques [1][2][3] . The structure of amorphous germania at high pressure has been examined using x-ray absorption spectroscopy [4][5][6][7] , Raman 8 and Infrared spectroscopy 9 as well as x-ray [10][11][12][13] and neutron diffraction [14][15][16] .…”

“…Static compression experiments on crystalline GeO 2 have concentrated on the high-pressure crystal structure [17][18][19] and phase transitions [20][21][22] . Dynamic compression experiments 1,2,[23][24][25] have also been carried out on germania crystals and glass. There have also been a number of theoretical studies [26][27][28][29] investigating the high-pressure behavior of the different phases of this material.…”

Impact cratering in H2O‐bearing targets on Mars: Thermal field under craters as starting conditions for hydrothermal activity

“…During release from shock, the frozen phase transition forces the material to expand along the frozen isentrope, which is steeper than the Hugonit curve. The effect has been investigated in special cases (Swegle 1990;Chen 1999;Liu et al 2002), but is yet to be implemented in the hydrocode used here. This problem is not unique to complex rocks; even in the classic case of quartz, where the frozen states and the mixed phase regions are well defined, some experimental data clearly show the shock wave splitting in the quartz-stishovite like transition zone (Zhugin 1996).…”

Effect of Material Phase Change on Penetration and Shock Waves

“…Over the past several years there has been speculation that materials exhibiting a phase change may make effective armor material due to their ability to absorb energy [1][2][3]. It is difficult to determine experimentally the effect a phase change may have on ballistic performance because of the combined effects of strength, density, failure and Equation of State (EOS).…”