Shock Compression Studies Research Articles

Static and shock compression studies of eutectic high-entropy alloy AlCoCrFeNi2.1 to ultrahigh pressures

The high-entropy alloy with composition AlCoCrFeNi2.1, additively manufactured with the laser powder-bed fusion technique, has a far-from-equilibrium BCC/FCC eutectic nanolamellar structure. We studied the high-pressure response of this alloy under both static compression and high-strain rate shock compression. The response to static compression using a diamond anvil cell was studied at pressures up to 302 GPa with synchrotron x-ray diffraction at the advanced photon source. The high-pressure FCC-only phase of the EHEA previously observed by Pope et al. [AIP Adv. 13, 035124 (2023)] is found to be stable up to the highest pressure achieved in this study with a volume compression of V/V0 = 0.587 at ambient temperature. The shock experiments were performed by using GEKKO XII lasers at the Institute of Laser Engineering, Osaka University. The principal Hugoniot equation-of-state of the EHEA was measured up to a pressure of 515 GPa and a compression of V/V0 = 0.613. Additionally, the thermal equation of state of the EHEA was measured up to 6.2 GPa and 1623 K using a large-volume Paris–Edinburgh cell to obtain the temperature dependence of bulk modulus and thermal expansion coefficients. The melting temperature for EHEA AlCoCrFeNi2.1 at a pressure of 5.6 GPa was measured to be 1648 ± 25 K. These results can be used to refine stochastic (or special) quasi-random structure (SQS) models for high-pressure high-temperature behavior of high-entropy alloys.

Palladium at high pressure and high temperature: A combined experimental and theoretical study

Palladium is one of the most important technological materials, yet its phase diagram remains poorly understood. At ambient conditions, its solid phase is face-centered cubic (fcc). However, another solid phase of Pd, body-centered cubic (bcc), was very recently predicted in two independent theoretical studies to occur at high pressures and temperatures. In this work, we report an experimental study on the room-temperature equation of state (EOS) of Pd to a pressure of 80 GPa, as well as a theoretical study on the phase diagram of Pd including both fcc-Pd and bcc-Pd. Our theoretical approach consists in ab initio quantum molecular dynamics (QMD) simulations based on the Z methodology which combines both direct Z method for the simulation of melting curves and inverse Z method for the calculation of solid–solid phase transition boundaries. We obtain the melting curves of both fcc-Pd and bcc-Pd and an equation for the fcc–bcc solid–solid phase transition boundary as well as the thermal EOS of Pd which is in agreement with experimental data and QMD simulations. We uncover the presence of another solid phase of Pd on its phase diagram, namely, random hexagonal close-packed (rhcp), and estimate the location of the rhcp-bcc solid–solid phase transition boundary and the rhcp–fcc–bcc triple point. We also discuss the topological similarity of the phase diagrams of palladium and silver, the neighbor of Pd in the periodic table. We argue that Pd is a reliable standard for shock-compression studies and present the analytic model of its principal Hugoniot in a wide pressure range.

New frontiers in extreme conditions science at synchrotrons and free electron lasers

Synchrotrons and free electron lasers are unique facilities to probe the atomic structure and electronic properties of matter at extreme thermodynamical conditions. In this context, ‘matter at extreme pressures and temperatures’ was one of the science drivers for the construction of low emittance 4th generation synchrotron sources such as the Extremely Brilliant Source of the European Synchrotron Radiation Facility and hard x-ray free electron lasers, such as the European x-ray free electron laser. These new user facilities combine static high pressure and dynamic shock compression experiments to outstanding high brilliance and submicron beams. This combination not only increases the data-quality but also enlarges tremendously the accessible pressure, temperature and density space. At the same time, the large spectrum of available complementary x-ray diagnostics for static and shock compression studies opens unprecedented insights into the state of matter at extremes. The article aims at highlighting a new horizon of scientific opportunities based on the synergy between extremely brilliant synchrotrons and hard x-ray free electron lasers.

Shock physics mesoscale modeling of shock stage 5 and 6 in ordinary and enstatite chondrites

Shock-darkening, the melting of metals and iron sulfides into a network of veins within silicate grains, altering reflectance spectra of meteorites, was previously studied using shock physics mesoscale modeling. Melting of iron sulfides embedded in olivine was observed at pressures of 40–50 GPa. This pressure range is at the transition between shock stage 5 (CS5) and 6 (CS6) of the shock metamorphism classification in ordinary and enstatite chondrites. To better characterize CS5 and CS6 with a mesoscale modeling approach and assess post-shock heating and melting, we used multi-phase (i.e. olivine/enstatite, troilite, iron, pores, and plagioclase) meshes with realistic configurations of grains. We carried out a systematic study of shock compression in ordinary and enstatite chondrites at pressures between 30 and 70 GPa. To setup mesoscale sample meshes with realistic silicate, metal, iron sulfide, and open pore shapes, we converted backscattered electron microscope images of three chondrites. The resolved macroporosity in meshes was 3–6%. Transition from shock CS5 to CS6 was observed through (1) the melting of troilite above 40 GPa with melt fractions of ~0.7–0.9 at 70 GPa, (2) the melting of olivine and iron above 50 GPa with melt fraction of ~0.001 and 0.012, respectively, at 70 GPa, and (3) the melting of plagioclase above 30 GPa (melt fraction of 1, at 55 GPa). Post-shock temperatures varied from ~540 K at 30 GPa to ~1300 K at 70 GPa. We also constructed models with increased porosity up to 15% porosity, producing higher post-shock temperatures (~800 K increase) and melt fractions (~0.12 increase) in olivine. Additionally we constructed a pre-heated model to observe post-shock heating and melting during thermal metamorphism. This model presented similar results (melting) at pressures 10–15 GPa lower compared to the room temperature models. Finally, we demonstrated dependence of post-shock heating and melting on the orientation of open cracks relative to the shock wave front. In conclusion, the modeled melting and post-shock heating of individual phases were mostly consistent with the current shock classification scheme (Stöffler et al., 1991, 2018).

Laser shock compression induced crystallization of Ce3Al metallic glass

Laser shock compression studies on Ce3Al metallic glass performed using a 3 J Nd:YAG laser indicate shock-induced crystallization, evidenced by the presence of a two-wave/stepped particle velocity profile and structural changes observed via X-ray Diffraction (XRD) analysis of recovered material. A direct shock-compression setup was designed with 25 μm thick Ni driver foil, 40 μm thick Ce3Al metallic glass ribbon, and 3 mm thick poly(methyl methacrylate) (PMMA) backer window for use with input laser energies varying from 100 to 2000 mJ and corresponding estimated peak pressures of 1.4 to 4.1 GPa in Ce3Al. At shock pressures below ∼1.8 GPa (300 mJ laser input energy), samples were recovered showing no obvious deformation or structural changes evidenced via XRD analysis. At higher laser energies and shock pressures above the elastic limit, samples were recovered showing visible deformation and crystallization evidenced by Rietveld analysis of diffraction patterns. The corresponding velocity profiles also showed a stepped wave structure, increasing in magnitude with energy. The overall results reveal possible densification of the glass due to delocalization of 4f electrons in Ce at lower laser shock pressures and increased crystallization with preferred orientation and distortion of the nanocrystals at higher shock compression conditions.

Shock response of poly[methyl methacrylate] (PMMA) measured with embedded electromagnetic gauges

The shock response of poly[methyl methacrylate] (PMMA) acquired from two providers, Spartech and Rohm & Haas, has been measured to investigate the shock response variations related to material pedigree. These measurements have also been used to examine the effects of viscoelasticity on Spartech PMMA. Measurements of the Hugoniot curves, release wave speeds, and index of refraction have been acquired up to previously unexplored stresses, ∼10.7 GPa, for Spartech PMMA. In-situ, time-resolved particle velocity wave profiles, as a function of time and depth, were obtained using twelve separate electromagnetic gauge elements embedded at different depths in the PMMA. A comparison of the new data to the shock response data for Rohm and Haas PMMA, used as a “standard” material in shock compression studies, shows that there are no significant differences in shock response for the two materials. From the index of refraction measurements, the apparent particle velocity correction for a PMMA window exhibits an interesting oscillation, increasing at up = 0.3 km/s after decreasing up to that point. The results are generalized into guidelines for sourcing PMMA for use in shock studies.

Nanometer-scale characterization of laser-driven compression, shocks, and phase transitions, by x-ray scattering using free electron lasers

We study the feasibility of using small angle X-ray scattering (SAXS) as a new experimental diagnostic for intense laser-solid interactions. By using X-ray pulses from a hard X-ray free electron laser, we can simultaneously achieve nanometer and femtosecond resolution of laser-driven samples. This is an important new capability for the Helmholtz international beamline for extreme fields at the high energy density endstation currently built at the European X-ray free electron laser. We review the relevant SAXS theory and its application to transient processes in solid density plasmas and report on first experimental results that confirm the feasibility of the method. We present results of two test experiments where the first experiment employs ultra-short laser pulses for studying relativistic laser plasma interactions, and the second one focuses on shock compression studies with a nanosecond laser system.

Role of Magnetosonic Solitons in Perpendicular Collisionless Shock Reformation.

The nature of the magnetic structure arising from ion specular reflection in shock compression studies is examined by means of 1D particle-in-cell simulations. Propagation speed, field profiles, and supporting currents for this magnetic structure are shown to be consistent with a magnetosonic soliton. Coincidentally, this structure and its evolution are typical of foot structures observed in perpendicular shock reformation. To reconcile these two observations, we propose, for the first time, that shock reformation can be explained as the result of the formation, growth, and subsequent transition to a supercritical shock of a magnetosonic soliton. This argument is further supported by the remarkable agreement found between the period of the soliton evolution cycle and classical reformation results. This new result suggests that the unique properties of solitons can be used to shed new light on the long-standing issue of shock nonstationarity and its role on particle acceleration.

Molecular response of liquid nitrogen multiply shocked to 40 GPa.

Liquid nitrogen was subjected to multiple shock compression to examine its response to pressures (15-40 GPa) and temperatures (1800-4000 K) previously unexplored in static and shock compression studies. Raman spectroscopy measurements were used to characterize the molecular bond response and to determine temperatures in the peak state. By extending our analysis to include other Raman spectroscopy measurements, an empirical relation was developed that describes the pressure and temperature dependence of the Raman shift (of the 2330 cm(-1) mode) for both shock and static compression. Based on the P-T dependence of the Raman shifts, the liquid nitrogen molecular response is best understood by considering three temperature regimes: below 1500 K, 1500-4000 K, and above 4000 K. For the pressures and temperatures accessed in the present work, liquid nitrogen remains a molecular fluid, and becomes a grey-body emitter at the highest pressures.

A new target design for laser shock-compression studies of carbon reflectivity in the megabar regime

A new design for targets employed in laser induced shock-compression experiments is presented. Numerical simulations to optimize target parameters and to clarify shock dynamics are realized. The experiments proved the new scheme is reliable and appropriate for reflectivity measurements of thermodynamical states lying out of the standard graphite or diamond Hugoniot: the final state reached in compression can be varied tuning the carbon layer characteristics (initial density and thickness) and the laser intensity, with the possibility to determine the reflectivity of carbon and the position on the phase diagram. An increase of reflectivity in carbon has been observed at 260 GPa and 14 000 K while no increase in reflectivity is found at 200 GPa and 20 000 K.

Ultrafast Shock Compression and Shock-Induced Decomposition of 1,3,5-Triamino-2,4,6-trinitrobenzene Subjected to a Subnanosecond-Duration Shock: An Analysis of Decomposition Products

Shock compression studies of pressed and confined ultrafine 1,3,5-triamino-2,4,6-trinitrobenzene (TATB) powder were conducted using ultrashort ~300 ps, ~50 GPa shock waves. The recovered decomposition products were characterized using X-ray photoelectron spectroscopy, infrared spectroscopy, and Raman spectroscopy. A substantial amount of shock-related chemistry was observed. Approximately 75% of the nitrogen atoms were liberated as gas-phase species, along with ~33% of the oxygen atoms, as a result of the applied shock. Furthermore, we observe C 1s binding energies suggesting the formation of sp(3) hybridized amorphous carbon. For comparison, a carbon nitride material was also prepared and characterized by thermally pyrolizing TATB. The shock-compressed TATB and the thermally pyrolized TATB are qualitatively different, suggesting that, carbon nitrides, a possible indicator of nitrogen-rich heterocycles precursors, are not a major product class for strongly overdriven shock conditions. These experimental conditions were, however, not detonation conditions, and the possible formation of nitrogen-rich heterocycles in actual detonations still exists.

Use of the Z Accelerator for Condensed Matter Studies at Multi-Mbar Pressures

The ability to study material response during isentropic compression has been a grand challenge of the scientific community for several decades. However, development of precision techniques for producing isentropic compression at high pressures has been limited. The revolutionary advance for using planar magnetic loading on the Z accelerator accelerated this goal by enabling quasi-isentropic studies on macroscopically sized materials to over 5 Mbar. In addition, the accelerator is easily configured to launch flyer plates to velocities more than four times higher than possible with conventional launchers, thus allowing shock compression studies in the laboratory to pressures exceeding 20 Mbar.

An equation of state for silicate melts. IV. Calibration of a multicomponent mixing model to 40 GPa

Mixing relations for the “high-pressure” parameters of the equation of state of Ghiorso (2004a) are developed and compositional coefficients are optimized to permit calculation of melt density in portions of the system SiO₂-TiO₂-Al₂O₃-FeO-MgO-CaO-Na₂O-K₂O to pressures in excess of 40 GPa and temperatures up to 2500°C. Four data sets are analyzed and fitted to yield an internally consistent model: (1) density estimates made from measurements of the sinking/floating of reference mineral markers in silicate liquids at known temperatures and pressures, (2) density estimates obtained from shock compression studies on molten liquids, (3) liquid densities inferred from the temperature and pressure dependence of the slopes of mineral fusion curves, and (4) estimates of densities of molten silicate liquids obtained by molecular dynamics simulations. Calibration compositions include chemically complex liquids (komatiite, peridotite and MORB bulk compostions) as well as simple liquids with mineral-like stoichiometry. The model recovers density with an average error of ∼2 percent. The model is limited by <i>not</i> including the effects of volatiles or oxidized iron at elevated pressure.

Numerical study of shock compression of graphite and its conversion to diamond in conical targets

The shock compression of carbon placed into lead conical targets that are subjected to a blow from aluminum strikers moving at a velocity of 4 km/s is numerically studied. The statement of the problem includes the hydrodynamic equations for compressed media, semi-empirical wide-range equations of state, and a kinetic model of nonequilibrium graphite-to-diamond conversion that is calibrated with known experimental data. All stages of the process are analyzed, starting from the cumulative effect at the symmetry axis of the target to the release of the sample due to the rarefaction wave coming from the rear side of the striker with allowance for spalling.

Elasticity, shear‐mode softening and high‐pressure polymorphism of wüstite (Fe1‐xO)

Elastic wave travel times have been determined as functions of hydrostatic pressure to 3 GPa for five modes of propagation in synthetic single‐crystal wüstite Feo.943O by ultrasonic phase comparison. The measured travel times, corrected for transducer‐bond phase shifts, constrain very accurately the zero‐pressure elastic moduli (GPa) and, for the first time, their first pressure derivatives (dimensionless) as follows: C11∶218.4, dC11/dP∶9.65, C12∶123.0, dC12/dP∶2.77, C44∶45.5, dC44/dP∶−1.03. The zero‐pressure moduli are in good agreement with the results of previous determinations by ultrasonic wave propagation but not with all of the moduli determined by resonance techniques. The variation of bulk modulus with pressure calculated from the Cij (P) is extrapolated to much higher pressures via third‐order Eulerian isotherms and isentropes based on K0S = 154.9 GPa and (dKs/dP)0T = 4.90. The resulting isothermal and shock compression curves satisfactorily reproduce the experimental data to ∼70 GPa, thereby providing a unified description of essentially all data bearing on the compressibility of wüstite. At higher pressures, published shock compression studies provide clear evidence for the existence of a different phase of much greater density and incompressibility. Metallic values of electrical conductivity have been reported for pressures &gt;70 GPa under conditions of shock and high‐temperature static loading. Polyhedral face‐sharing in either the B8(NiAs) or B2(CsCl) (or derivative) structures would result in shorter Fe‐Fe distances, allowing greater 3d orbital overlap conducive to metallic conductivity. However, none of these possibilities satisfactorily accounts for the large inferred increase (14–20%) in zero‐pressure density unless the Fe‐O distance is also reduced by 3–5% by electron delocalization or spin‐pairing. The marked violation of the Cauchy condition associated with the very low value of C44 and its unusual temperature and pressure derivatives are attributable mainly to exchange coupling between nearest and next‐nearest neighbor spins.

High-pressure shock modification and synthesis of superconducting ceramic oxides

Our shock-compression efforts of high-temperature superconducting ceramic oxides are reviewed. These consist of: (i) shock-induced chemical synthesis on various mixtures of metal oxides of composition similar to those which yield known high-temperature superconductor oxides; and (ii) shock-modification studies on high quality YBa 2Cu 3O 6.9 (Y-123), Bi 2CaSr 2O 8 (Bi-2122) and Tl 2Ca 2Ba 2Cu 3O 10 (Tl-2223) powder compacts. Fundamentals of the Sandia shock-compression studies are reviewed here so as to present a more comprehensive view on processes influencing shock modification and/or synthesis. Various mixtures of metal oxides of compositions known to yield high-temperature superconducting oxides under conventional ceramic processing have been subjected to a range of shock-loading conditions to determine parameters leading to their shock-induced chemical synthesis. For La 1.85−Sr 0.15CuO 4 recovered samples show X-ray diffraction lines consistent with the formation of the K 2NiF 4 structure type crystallographic phase in high yields. Studies on the YBaCu system yielded diffraction lines consistent with those for a few percent yield of Y-123. In addition, studies on BaO and Y 2O 3 were carried out, since these oxides appeared to influence the reaction forming Y-123. Superconducting powders of Y-123 have been shock-modified at pressures of 20 and 27 GPa in the Sandia “Bear” gas-tight copper recovery capsules and subsequently characterized by static magnetization, electrical transport and X-ray diffraction. Magnetization data show considerable degradation in the superconducting properties of the shock-modified material which is attributed to a loss of oxygen during the shock process. This is confirmed by the X-ray studies which show partial conversion to the non-superconducting tetragonal phase. Subsequent oxygen annealing restores the magnetic response, and a field loop at 77 K demonstrates strongly endhanced flux pinning, presumably related to the presence of point, line and structural defects and/or impurities (ion substitution) introduced by the shock-modification process. No improvement in transport critical current is observed compared with our standard prepared materials, presumably because of the weak-link nature of the intergranular connections. Superconducting powders of Bi-2122 and Tl-2223 have been shock modified at pressures of 7.5 and 27 GPa, respectively. The Bi-2122 material contained a small amount (≈0.1%) of the so-called 100 K phase (Bi-2223), detectable only by its Meissner signature at such low concentration levels, which is not present following shock loading. The Tl-2223 sample showed a broadened transition and a decrease in expulsion, but the onset of superconductivity increased from 117 to 123 K. Although the potential for direct shock synthesis of superconductors has not been demonstrated, these studies suggest that superconducting material systems which are robust with respect to stoichiometry, particularly oxygen, may benefit from shock-modification processes which introduce defects serving as flux pinning sites in the superconductors. More detailed studies on flux motion in shock-modified materials remain to be carried out.

Study of shock-compression of halogen derivatives of methane

Study of shock-compression of halogen derivatives of methane

Study of higher‐order elastic and piezoelectric constants with shock‐wave loading techniques

Many solids remain elastic to strains of a few percent when subjected to uniaxial strain imposed by shock loading. Nonlinear contributions are enhanced by such large elastic strains and become accessible for relatively straightforward measurement and interpretation. Impact loading techniques have proven particularly effective for measurements of second‐, third‐ and fourth‐order longitudinal piezoelectric constants as well as third‐ and fourth‐order longitudinal elastic constants. Shock compression studies have provided independent measurements of constants, have uniquely determined certain constants and have extended ultrasonic measurements by several orders of magnitude in strain. Typical experimental investigations and their results will be summarized and compared to corresponding ultrasonic data. [This work sponsored by the U.S. Department of Energy under Contract DEAC04‐76‐DP00789 to Sandia Laboratories, a U.S. Department of Energy facility.]

Shock compression of dolomite

Shock compression studies on a dolomite rock (ρ0 = 2.84 g/cm3) have been conducted in the stress range 150–450 kbar. The entire loading and unloading history as well as the Hugoniot properties were investigated, using continuous recording piezoresistant stress gages. The following results were obtained: (1) The Hugoniot shock velocity-particle velocity curve shows deviation from linearity in a region corresponding to stresses between 100 and 250 kbar. (2) Comparison of the experimental Hugoniot with a Murnaghan pressure-volume relation extrapolated from low-pressure ultrasonic data indicates anomalous compressibility. (3) Unloading experiments from peak stresses between 180 and 300 kbar show excessive hysteresis in the stress-volume plane. (4) Shock compression to a peak stress in excess of 400 kbar is followed by immediate stress relaxation. (5) Overtaking relief wave velocities measured at the Hugoniot state are found to be considerably higher than extrapolated bulk sound velocities. Our interpretation of the results is a rate-dependent, low- to high-density phase transformation occurring in the stress range 100–500 kbar.

Shock Compression of Teflon from 2.5 to 25 kbar-Evidence for a Shock-Induced Transition

Uniaxial shock-compression studies were conducted on Teflon in the stress region between 2.5 and 25 kbar using a compressed-gas gun and quartz-gauge instrumentation. Measurements of stress and particle velocity at the impact surface show that a transition occurs at 5.0 ± 0.2 kbar with an associated volume change of approximately 2.2 ± 0.2%. Measurements of the stress wave profiles after transmission through the samples show an attenuation of peak stresses and suggest a visoelastic behavior of Teflon.