Shock Compression Method Research Articles

Formation of Novel Bimetal Oxide In2V2O7 through a Shock Compression Method.

Bimetal oxides with a chemical formula of A2B2O7 have received much attention from plenty of research groups owing to their outstanding properties, such as electronic, optical, and magnetic properties. Among the abundant element combinations of cations A and B, some theoretically predicted compounds have not successfully been synthesized in experiments, such as In2Zr2O7, In2V2O7, etc. In this study, a novel tetragonal pyrochlore-like In2V2O7 nanopowder has been reported for the first time. In2O3 and VO2 powders mixed through ball milling were reacted to form In2V2O7 by shockwave loading. The recovered sample is investigated to be nanocrystalline In2V2O7 powder through various techniques, such as X-ray diffraction, scanning electron microscopy, X-ray energy spectrum analysis, and transmission electron microscopy. The formed In2V2O7 is indexed as a tetragonal cell with a = b = 0.7417 nm and c = 2.1035 nm. Moreover, the formation mechanism of In2V2O7 through a shock synthesis process is carefully analyzed based on basic laws of shockwave. The experimental results also confirm that a high shock temperature and high shock pressure are the two key factors to synthesize the In2V2O7 nanopowder. Our investigation demonstrates the high potential application of a shock-induced reaction on the synthesis of novel materials, including the preparation of new bimetal oxides.

Preparation of Niobium Aluminium Alloy Based on Shock Compression Method

A new method based on a light-gas gun has been proposed to synthesize Nb-Al alloys, and a recovery capsule has been investigated. The copper-coated sample is accessible after shock wave loading. In this paper, we successfully synthesize Nb-Al alloys, which are high-temperature structural materials. X-ray diffraction is employed to clarify the structural characteristics of compounds after impact, and the simulation of X-ray diffractions is employed to clarify the structure. In detail, tetragonal NbAl3 alloys certainly appeared in the recovery capsule; this alloy is considered to be best candidate.

Review of Electrical Resistivity Measurements and Calculations of Fe and Fe-Alloys Relating to Planetary Cores

There is a considerable amount of literature on the electrical resistivity of iron at Earth’s core conditions, while only few studies have considered iron and iron-alloys at other planetary core conditions. Much of the total work has been carried out in the past decade and a review to collect data is timely. High pressures and temperatures can be achieved with direct measurements using a diamond-anvil cell, a multi-anvil press or shock compression methods. The results of direct measurements can be used in combination with first-principle calculations to extrapolate from laboratory temperature and pressure to the relevant planetary conditions. This review points out some discrepancies in the electrical resistivity values between theoretical and experimental studies, while highlighting the negligible differences arising from the selection of pressure and temperature values at planetary core conditions. Also, conversions of the reported electrical resistivity values to thermal conductivity via the Wiedemann-Franz law do not seem to vary significantly even when the Sommerfeld value of the Lorenz number is used in the conversion. A comparison of the rich literature of electrical resistivity values of pure Fe at Earth’s core-mantle boundary and inner-core boundary conditions with alloys of Fe and light elements (Si, S, O) does not reveal dramatic differences. The scarce literature on the electrical resistivity at the lunar core suggests the effect of P on a wt% basis is negligible when compared to that of Si and S. On the contrary, studies at Mercury’s core conditions suggest two distinct groups of electrical resistivity values but only a few studies apply to the inner-core boundary. The electrical resistivity values at the Martian core-mantle boundary conditions suggest a negligible contribution of Si, S and O. In contrast, Fe-S compositions at Ganymede’s core-mantle boundary conditions result in large deviations in electrical resistivity values compared to pure Fe. Contour maps of the reported values illustrate ρ(P, T) for pure Fe and its alloys with Ni, O and Si/S and allow for estimates of electrical resistivity at the core-mantle boundary and inner-core boundary conditions for the cores of terrestrial-like planetary bodies.

Tantalum sound velocity under shock compression

We used several variations of the shock compression method to measure the longitudinal sound velocity of shocked tantalum over the pressure range 37–363 GPa with a typical uncertainty of 1.0%. These data are consistent with Ta remaining in the bcc phase along the principal Hugoniot from ambient pressure to ≈300 GPa, at which pressure melting occurs. These data also do not support the putative melting phenomena reported below 100 GPa in some static compression experiments.

Sound velocity and density measurements of liquid iron up to 800 GPa: A universal relation between Birch's law coefficients for solid and liquid metals

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.

Quenching of High-Pressure Phases of Silicon Using Femtosecond Laser-driven Shock Wave

High-pressure phases which are Β-Sn, Imma and simple hexagonal structures of silicon are quenched using an intense femtosecond laser-driven shock wave. These high-pressure phases have never synthesized in ambient pressure by hydrostatic and conventional shock compression methods. Femtosecond laser was irradiated to single crystal-silicon with no-dopant. We confirmed the existence of these high pressure phases by analyzing the crystalline structure of the femtosecond laser irradiated silicon using grazing incidence synchrotron x-ray diffraction.

高強度レーザーによる高圧地球科学研究

We have been developing experiments on shock compression relevant to Earth core condition with intense laser irradiation. Multiple shock compression method is applied to create pressure and temperature (P, T) conditions of geophysical interest. We measured sound velocity of shock-compressed iron foils with two-stepped laser pulse irradiation by x-ray radiography technique. We have also developed nanosecond x-ray diffraction in order to measure the structure of shock-compressed materials.

Femtosecond Laser Synthesis of High-Pressure Phases of Si

The high pressure simple hexagonal structure of silicon, which has not been synthesized, is quenched using femtosecond laser-driven shock wave. Any high-pressure phases of silicon do not remain after the pressure release in the case of the hydrostatic and conventional shock compression methods. We found the existence of the simple hexagonal structure after the intense femtosecond laser irradiation to silicon by analyzing the crystalline structures using a synchrotron grazing-incidence XRD method. Femtosecond laser-driven shock wave is a useful tool for the synthesis of non-equilibrium high-pressure phases.

Explosion energy in the synthesis of superhard phases

This article reviews works of the Institute for Problems of Materials Science evoted to the application of explosion energy for the synthesis of superhard phases (SHPs) based on phase transformations of layered structures of carbon and boron nitride at high pressures. Major attention is given to the development and application of the high-temperature shock compression method, which made it possible to synthesize a new structural form of carbon and to attain, for the first time, a 70% yield of cubic BN under shock compression. The diagram of BN phase transformations by different mechanisms is discussed, which demonstrates the dependence of the phase composition of shock compression products on the ordering degree of the starting graphite-like structure.

Effect of shock compression method on the defect substructure in monocrystalline copper

Monocrystalline copper samples with orientations of [0 0 1] and [2 2 1] were shocked at pressures ranging from 20 to 60 GPa using two techniques: direct drive lasers and explosively driven flyer plates. The pulse duration for these techniques differed substantially: 40 ns for the laser experiments at 0.5 mm into the sample and 1.1∼1.4 μs for the flyer-plate experiments at 5 mm into the sample. The residual microstructures were dependent on orientation, pressure, and shocking method. The much shorter pulse duration in the laser driven shock yielded microstructures in recovery samples closer to those generated at the shock front. For the flyer-plate experiments, the longer pulse duration allows shock-generated defects to reorganize into lower energy configurations. Calculations show that the post-shock cooling for the laser driven shock is 10 3 ∼ 10 4 faster than that for plate-impact shock, increasing the amount of annealing and recrystallization in recovery samples for the latter. At the higher pressure level, extensive recrystallization was observed in the plate-impact samples, while it was absent in laser driven shock. An effect that is proposed to contribute significantly to the formation of recrystallized regions is the existence of micro-shear-bands, which increase the local temperature beyond the prediction from adiabatic compression.

The isotope effect of gaseous hydrogen under shock compression

The shock compression method has been used to measure the Hugoniot data and shock temperature for gaseous hydrogen samples, covering the pressure range of 55-140 MPa and the temperature range of 3400-4500 K and with the initial conditions of P 0 = 0.6 MPa, 1.2 MPa and T 0 at room temperature. Spectral radiance histories emitted from shocked D 2 and H 2 + D 2 (equimolar mixture) are monitored by a pyrometer system with seven wavelength channels. Theoretical calculations based on the Saha model with Debye-Huckel correction for the shock compression behavior of shocked gaseous samples are in good agreement with the measured Hugoniot data, but show slightly higher values for the shock temperature when comparing with experiments. An isotope effect relevant to these shocked hydrogen species has been found in the linear shock velocity vs particle velocity relation, in which the correlation factor between these hydrogen isotopes or hydrogen mixtures is simply of initial density dependence.

衝撃圧縮法により作製されたＣｒＷ合金の粒径依存性

Phase-separation process is essential phenomenon owing to influence on quality of alloy. Miscibility gap was found on phase diagram of Cr-W alloy, however other things of Cr-W alloy haven't been studied after that. Therefore the aim of this study is to prepare nonequilibrated alloy under the miscibility gap by shock compression method, and to study grain size dependence on it. W powder of average grain size between 1μm to 8μm mixed Cr powder of 10μm grain size is put pressure on 42GPa using a one-stage powder gun. As a result, the smaller W grain size is, the more Cr-W alloy. And in the case that W powder is small to 0.6μm and enough specific surface area in mixed powder, nearly homogeneous Cr-W alloy prepared. Fluid Cr alloy with W melted as high temperature concentrate on surface of grains.

Creation of superhard B–C–N heterodiamond using an advanced shock wave compression technology

Abstract A new hard material, the B–C–N heterodiamond, was synthesized by the shock-compression method. The heterodiamond is a polycrystalline material coagulated with nano-crystallites and the fine powder is tinged with deep bluish black. The heterodiamond was confirmed to have both the highest hardness of diamond and the excellent heat resistance of cubic BN. These characteristic properties are due to the diamond structure combined with the sp 3 σ -bonds among carbon and the hetero atoms.

Characterization of EuBa2Cu3Oy Synthesized in Shock Processes

We synthesized a homogeneous, tetragonal EuBa2Cu3Oy with c/a=3.00 by the shock compression method. The phase is considered to be similar to the tetragonal YBa2Cu3Oy metastably formed at relatively low temperature with the c/a ratio=3.00. Electron diffraction patterns indicate ordering of Eu and Ba atoms to some extent, but ordering is presumably not perfect. High resolution trasmission electron microscory images show that shock-synthesized EuBa2Cu3Oy consists of 60-80-Å-size domains, whose principal axes are perpendicular to each other. Perfect ordering of Eu and Ba atoms was achieved by annealing the shock-synthesized specimen above 900° C, resulting in the increase of the c/a ratio from 3.00 to 3.05 as well as superconduction upon O2 annealing. This result is explained by the shortness of the reaction time in shock processes.

New Complex Magnetic Material for Ericsson Magnetic Refrigerator

A complex magnetic material for use in the Ericsson magnetic refrigerator was investigated. In order to refrigerate effectively in the high temperature range above 10K, it is necessary to utilize the Ericsson cycle that includes two kinds of iso-magnetic field process, because lattice entropy for a magnetic refrigerant amounts to the same order of magnitude as that for magnetic entropy. Therefore in the Ericsson magnetic refrigerant, magnetic entropy change ΔSM is required to be constant in the refrigeration range. This property, however, cannot be satisfied by usual ferromagnetic material. In this paper, the complex RAl2 magnetic mixture (where R denotes heavy rare earth atoms) in grain size scale is prepared by shock compression method. Magnetic entropy changes are determined from the specific heat measurement. This magnetic mixture has high density, which is composed of several RAl2 compounds with different Curie temperatures, where each RAl2 is surrounded by gold. From these experimental results, it is concluded that the complex magnetic mixture with gold, such as (ErAl2)0.3 (HoAl2)0.2(Dy0.5Ho0.5Al2)0.5, shows an almost temperature independent magnetic entropy change ΔSM in some temperature range, which is suitable for the Ericsson cycle, satisfying the Carnot principle.

衝撃成形法による希土類‐アルミニウム系混合磁性多結晶体の作成と熱的・磁気的性質

A preparation method of a complex type RAl2 magnetic system (where R denotes rare earth ions) for Ericsson type magnetic refrigerator is investigated. Previously, the authors reported on the model complex magnetic refrigerant with layer structure and concluded that this complex magnetic refrigerant shows a temperature independent magnetic entropy change ΔSM in particular temperature range, which is suitable for the Ericsson cycle, satisfying the Carnot principle.In this paper, the preparation of a complex type RAl2 magnetic mixture by a shock compression method, which is a high density mixture of its components in grain size scale, is described and its thermal and magnetic properties are discussed in respect to application to the Ericsson type magnetic refrigerant.

Generation of Very High Pressures by Shock Compression Method and Their Use for Solid State Physics

Generation of Very High Pressures by Shock Compression Method and Their Use for Solid State Physics

Shock synthesis of superconducting intermetallic compounds

1. These experiment showed that the shock-compression method can be used to synthesize intermetallic compounds in the Nb−Sn, Nb−Ge, and Nb−Pb systems. 2. The transition temperature for the compound Nb3Sn synthesized by the shock-compression method is slightly lower than the maximum transition temperature known for this system.