Sound velocity measurements by x-ray shadowgraph technique for melting phenomena at ultrahigh-pressure regime (original) (raw)
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Measurements of Sound Velocity of Diamond at the Pressure Around the Melt
2011
We have measured the sound velocity of the diamond foils at around the melting pressures (500-1500 GPa). Experiments were done on GEKKO-XII glass laser system with HIPER irradiation facility. Single crystal diamond foils (Ia) of 30∼40 µm thickness were irradiated at intensities of 0.2-1.5 × 10 14 W/cm 2. We measured the sound velocity by side-on x-ray backlighting technique. Trajectories of foil surfaces were observed by x-ray streak camera. We also measured the shock velocity by two VISARs (velocity interferometer system for any reflector), and shocked temperature by an SOP (streaked optical pyrometer) in order to determine the pressure and the temperature at around the melting. Experimental data were compared with the previous theoretical studies and the percolation theory.
Russian Geology and Geophysics, 2015
We determined the compressional velocity of hcp-Fe in a wide pressure and temperature range using high-resolution inelastic X-ray scattering (IXS) combined with in situ X-ray powder diffraction (XRD) on samples in resistively heated diamond anvil cells: our measurements extend up to 174 GPa at room temperature, to 88 GPa at 700 K, and to 62.5 GPa at 1000 K. Our data obtained at room temperature and high temperature are well described by a linear relation to density, extending the range of verification of Birch’s law beyond previous work and suggesting only a small temperature dependence up to 1000 K. When we compare the present results with the preliminary reference Earth model (PREM), we can conclude that there is either a strong temperature effect on Birch’s law at temperatures above 1000 K, or the composition of the core is rather different from that commonly expected, i.e., containing heavy elements.
Ultrasonics, 2014
Based on the original combination of picosecond acoustics and diamond anvils cell, recent improvements to accurately measure hypersonic sound velocities of liquids and solids under extreme conditions are described. To illustrate the capability of this technique, results are given on the pressure and temperature dependence of acoustic properties for three prototypical cases: polycrystal (iron), single-crystal (silicon) and liquid (mercury) samples. It is shown that such technique also enables the determination of the density as a function of pressure for liquids, of the complete set of elastic constants for single crystals, and of the melting curve for any kind of material. High pressure ultrafast acoustic spectroscopy technique clearly opens opportunities to measure thermodynamical properties under previously unattainable extreme conditions. Beyond physics, this state-of-the-art experiment would thus be useful in many other fields such as nonlinear acoustics, oceanography, petrology, in of view. A brief description of new developments and future directions of works conclude the article.
Determination of indium melting curve at high pressure by picosecond acoustics
Physical Review Materials
Picosecond acoustics combined with diamond anvil cell is used to study liquid indium and to determine with high accuracy both the sound velocity and the melting curve over an extended pressure and temperature range. The sound velocities, determined by phonon surface imaging, complement previous inelastic X-ray scattering determinations and are in good agreement with estimations according to a thermodynamic model. Based on exact thermodynamic relations, the equation of state of the liquid phase is obtained using the isothermal bulk modulus BT,0 and its first pressure derivative B ′ T. These quantities are derived from the precise experimental determination of the variation of the sound velocity as a function of pressure. Melting is determined via the detection of abrupt changes in the elastic properties between solid and liquid phases and through the monitoring of the solid-liquid coexistence. The melting curve constrained up to 6 GPa and 673 K is shown to be well described by the Simon-Glatzel equation in the full (p,T) range explored.
Earth and Planetary Science Letters, 2014
ABSTRACT We performed compressional sound velocity and density measurements on liquid iron at pressures up to 800 GPa with a newly refined shock-compression method using a high-power laser. We found that sound velocity as a function of density can be fitted to a linear relation following Birch's law for hot dense liquid as well as for the solid phase of iron, with a slope ratio between the solid and liquid of approximately 1.5. A comparison of Birch's law for solid and liquid metals indicates that the sound velocity in the liquid phase is about 10% lower than that in the solid phase at melting point density, which is about 1.5 times larger than the initial density. We suggest that these relations between Birch's law coefficients for solid and liquid phases along the Hugoniot are universal for metals.
Minerals
We describe here a time resolved pump-probe laser technique—picosecond interferometry—which has been combined with diamond anvil cells (DAC). This method enables the measurement of the longitudinal sound velocity up to Mbar pressure for any kind of material (solids, liquids, metals, insulators). We also provide a description of picosecond acoustics data analysis in order to determine the complete set of elastic constants for single crystals. To illustrate such capabilities, results are given on the pressure dependence of the acoustic properties for prototypical cases: polycrystal (hcp-Fe-5 wt% Si up to 115 GPa) and single-crystal (Si up to 10 GPa).
American Mineralogist
The sound velocity of hcp Fe 0.89 Si 0.11 (Fe-6wt. % Si) alloy was measured at pressures from 45 to 84 GPa and temperatures of 300 and 1800 K using inelastic X-ray scattering (IXS) from laser-heated samples in diamond anvil cells (DACs). The compressional velocity (VP) and density () of the Fe-Si alloy are observed to follow a linear relationship at a given temperature. For hcp Fe 0.89 Si 0.11 alloy we found VP = 1.030 (± 0.008) ×ρ-1.45 (±0.08) + [3.8×10-5 (T-300)×(-15.37)], including non-negligible temperature dependence. The present results of sound velocity and density of hcp Fe 0.89 Si 0.11 alloy indicates that 3~6 wt. % of silicon in the inner core with additional amount of Ni can explain the compressional velocity (VP) and density () of the "Preliminary Earth reference model" (PREM), assuming a temperature of 5500 K and that silicon is the only light element in the inner core
Metallurgical and Materials Transactions A, 2015
The highly dynamic behavior of ultrasonic bubble implosion in liquid metal, the multiphase liquid metal flow containing bubbles and particles, and the interaction between ultrasonic waves and semisolid phases during solidification of metal were studied in situ using the complementary ultrafast and high-speed synchrotron X-ray imaging facilities housed, respectively, at the Advanced Photon Source, Argonne National Laboratory, US, and Diamond Light Source, UK. Real-time ultrafast X-ray imaging of 135,780 frames per second revealed that ultrasonic bubble implosion in a liquid Bi-8 wt pctZn alloy can occur in a single wave period (30 kHz), and the effective region affected by the shockwave at implosion was 3.5 times the original bubble diameter. Furthermore, ultrasound bubbles in liquid metal move faster than the primary particles, and the velocity of bubbles is 70~100 pct higher than that of the primary particles present in the same locations close to the sonotrode. Ultrasound waves can very effectively create a strong swirling flow in a semisolid melt in less than one second. The energetic flow can detach solid particles from the liquid-solid interface and redistribute them back into the bulk liquid very effectively.