Yoshinori Tange

Pressure generation to 80 GPa using multianvil apparatus with sintered diamond anvils

Experimental techniques for high-pressure generation have been developed using a multianvil apparatus with sintered diamond (SD) anvils. High-pressure cell assemblies have been optimized for SD anvils using a new Al2O3 pressure medium and baked pyrophyllite gaskets, which has enabled generation of pressures up to 80 GPa at room temperature. High-temperature experiments were also performed using cylindrical and graphite-windowed LaCrO3 furnaces in the Al2O3 pressure medium to be suitable for in situ observations. Temperatures were generated up to 1600 K and stably maintained for more than 1 h at pressures up to 60 GPa. Present techniques using SD anvils can now reproduce the middle region of the Earths lower mantle without sacrificing the great advantage of multianvil apparatus in stable and reproducible high-pressure and high-temperature generation.

The P‐V‐T equation of state and thermodynamic properties of liquid iron

The equation of state (EoS) and thermodynamic properties of non-magnetic liquid iron were investigated from energy (E)-pressure (P)-volume (V)-temperature (T) relationships calculated by means of ab initio molecular dynamics simulations at 60–420 GPa and 4000–7000 K. Its internally consistent thermodynamic and elastic properties, in particular, density, adiabatic bulk modulus, and P wave velocity, were then analyzed. Compared to the seismological data of the Earths outer core, pure liquid iron is found to have an 8–10% larger density and 3–10% larger bulk modulus than the Earths values. Results also show that the P wave velocity of liquid iron has marginal temperature dependence as the bulk sound velocity of solid iron. The new EoS model and thermodynamic properties of liquid iron may serve as fundamental data for the thermochemical modeling of the Earths core.

Temperature-pressure-volume equation of state of the B2 phase of sodium chloride

The temperature-pressure-volume (T-P-V) data of the B2 phase of sodium chloride (NaCl) were measured at high temperatures between 1023 and 1973K, and high pressures between 22.9 and 26.3GPa, using synchrotron powder x-ray diffraction experiments with a Kawai-type multianvil high pressure apparatus. The Mie–Gruneisen-type thermal pressure analysis was made to obtain the high temperature and high pressure T-P-V equation of state (EOS) of the B2 phase based on the present measured T-P-V data together with the 300K volume compression data previously reported using diamond-anvil-cell experiments. Some molecular dynamics calculations using a breathing shell model interionic potential, recently developed for the NaCl system, were also carried out to investigate the behavior of thermal pressure of the B2 phase at high temperatures and high pressures. The resulting T-P-V EOS agrees very well with recently measured volume compression data at 1000K. Here we present the T-P-V EOS of the B2 phase up to 3000K and more ...

Icosahedral AlCuFe quasicrystal at high pressure and temperature and its implications for the stability of icosahedrite.

The first natural-occurring quasicrystal, icosahedrite, was recently discovered in the Khatyrka meteorite, a new CV3 carbonaceous chondrite. Its finding raised fundamental questions regarding the effects of pressure and temperature on the kinetic and thermodynamic stability of the quasicrystal structure relative to possible isochemical crystalline or amorphous phases. Although several studies showed the stability at ambient temperature of synthetic icosahedral AlCuFe up to ~35 GPa, the simultaneous effect of temperature and pressure relevant for the formation of icosahedrite has been never investigated so far. Here we present in situ synchrotron X-ray diffraction experiments on synthetic icosahedral AlCuFe using multianvil device to explore possible temperature-induced phase transformations at pressures of 5 GPa and temperature up to 1773 K. Results show the structural stability of i-AlCuFe phase with a negligible effect of pressure on the volumetric thermal expansion properties. In addition, the structural analysis of the recovered sample excludes the transformation of AlCuFe quasicrystalline phase to possible approximant phases, which is in contrast with previous predictions at ambient pressure. Results from this study extend our knowledge on the stability of icosahedral AlCuFe at higher temperature and pressure than previously examined, and provide a new constraint on the stability of icosahedrite.

Phase boundary between perovskite and post-perovskite structures in MnGeO3 determined by in situ X-ray diffraction measurements using sintered diamond anvils

Abstract To determine the phase boundary between the perovskite and post-perovskite structures in MnGeO3, in situ X-ray observations were carried out at pressures of 57-68 GPa and temperatures of 1000-1900 K using the Kawai-type high-pressure apparatus equipped with sintered diamond anvils interfaced with synchrotron radiation. The phase boundary was determined to be P (GPa) = 39.2 + 0.013T (K) based on Tsuchiya’s (2003) gold pressure scale. The Clapeyron slope, dP/dT, of 13(+12/-5) MPa/K, determined in the present study is larger that of MgGeO3 and MgSiO3.

Ultrafast observation of lattice dynamics in laser-irradiated gold foils

We have observed the lattice expansion before the onset of compression in an optical-laser-driven target, using diffraction of femtosecond X-ray beams generated by the SPring-8 Angstrom Compact Free-electron Laser. The change in diffraction angle provides a direct measure of the lattice spacing, allowing the density to be calculated with a precision of ±1%. From the known equation of state relations, this allows an estimation of the temperature responsible for the expansion as <1000 K. The subsequent ablation-driven compression was observed with a clear rise in density at later times. This demonstrates the feasibility of studying the dynamics of preheating and shock formation with unprecedented detail.

Dynamic fracture of tantalum under extreme tensile stress

The dynamic fracture of tantalum is observed at the atomic scale using an x-ray monitoring technique at the SACLA XFEL facility. The understanding of fracture phenomena of a material at extremely high strain rates is a key issue for a wide variety of scientific research ranging from applied science and technological developments to fundamental science such as laser-matter interaction and geology. Despite its interest, its study relies on a fine multiscale description, in between the atomic scale and macroscopic processes, so far only achievable by large-scale atomic simulations. Direct ultrafast real-time monitoring of dynamic fracture (spallation) at the atomic lattice scale with picosecond time resolution was beyond the reach of experimental techniques. We show that the coupling between a high-power optical laser pump pulse and a femtosecond x-ray probe pulse generated by an x-ray free electron laser allows detection of the lattice dynamics in a tantalum foil at an ultrahigh strain rate of ε. ~2 × 108 to 3.5 × 108 s−1. A maximal density drop of 8 to 10%, associated with the onset of spallation at a spall strength of ~17 GPa, was directly measured using x-ray diffraction. The experimental results of density evolution agree well with large-scale atomistic simulations of shock wave propagation and fracture of the sample. Our experimental technique opens a new pathway to the investigation of ultrahigh strain-rate phenomena in materials at the atomic scale, including high-speed crack dynamics and stress-induced solid-solid phase transitions.

Generation of pressures over 40 GPa using Kawai-type multi-anvil press with tungsten carbide anvils

We have generated over 40 GPa pressures, namely, 43 and 44 GPa, at ambient temperature and 2000 K, respectively, using Kawai-type multi-anvil presses (KMAP) with tungsten carbide anvils for the first time. These high-pressure generations were achieved by combining the following pressure-generation techniques: (1) precisely aligned guide block systems, (2) high hardness of tungsten carbide, (3) tapering of second-stage anvil faces, (4) materials with high bulk modulus in a high-pressure cell, and (5) high heating efficiency.

Pressure generation to 50 GPa in Kawai-type multianvil apparatus using newly developed tungsten carbide anvils

ABSTRACT A pressure generation test for Kawai-type multianvil apparatus (KMA) has been made using second-stage anvils of a newly developed ultra-hard tungsten carbide composite. Superb performance of the new anvil with significantly less plastic deformation was confirmed as compared to those commonly used for the KMA experiments. A maximum pressure of ∼48 GPa was achieved using the new anvils with a truncation edge length (TEL) of 1.5 mm, based on in situ X-ray diffraction measurements. Further optimization of materials and sizes of the pressure medium/gasket should lead to pressures even higher than 50 GPa in KMA using this novel tungsten carbide composite, which may also be used for expansion of the pressure ranges in other types of high pressure apparatus operated in large volume press.

Correction to “Unified analyses for P‐V‐T equation of state of MgO: A solution for pressure‐scale problems in high P‐T experiments”

[1] In the paper “Unified analyses for P‐V‐T equation of state of MgO: A solution for pressure‐scale problems in high P‐T experiments” by Yoshinori Tange, Yu Nishihara, and Taku Tsuchiya (Journal of Geophysical Research, 114, B03208, doi:10.1029/2008JB005813, 2009), a postspinel phase boundary in Mg2SiO4 [Fei et al., 2004b] and a postperovskite boundary in MgSiO3 [Hirose et al., 2006] were reassessed by using a P‐V‐T EOS of MgO proposed in this study based on the Scale‐Free Unified Analysis (SFUA). However, we found that in Figure 11, the postperovskite boundary by Tsuchiya et al. [2004] was plotted incorrectly. Here the corrected Figure 11 is represented. [2] Also in Figure 11, data points and the phase boundaries of Fei et al. [2004b] and Hirose et al. [2006] were recalculated by using Speziale et al.’s [2001] EOS of MgO. In the modified Figure 11, we replace them with their original boundaries for easier and more direct comparison. Moreover, the postspinel and postperovskite boundaries were plotted within the different pressure and temperature scales. We also modify this to the same scales with more appropriate (geophysically relevant) pressure and temperature ranges.