Search

The α−ɛ phase transition stresses of single-crystal iron under shock compression along the [100], [110], and [111] crystal orientations were measured to be ∼13.3 ± 0.5, 13.5 ± 0.4, and 12.8 ± 0.4 GPa, respectively. Within the uncertainty of the measurement, the phase transition stresses of single crystal iron do not show obvious orientational dependence. These results differ from the simulation studies of the nonequilibrium molecular dynamics. We suggest that single crystal iron loses most shear stress beyond the Hugoniot-elastic-limit and the phase transition happens under a nearly hydrostatic state.

An atomic-scale graded structure has been formed previously in a Bi70Sb30 (at. %) alloy that is miscible in all proportions, by sedimentation of substitutional solute atoms under an ultrastrong gravitational field up to 1×106 G at 220–240 °C [T. Mashimo, T. Ikeda, and I. Minato, J. Appl. Phys. 90, 741 (2001)]. In this study, additional megagravity field experiments were performed on the Bi70Sb30 alloy and pure Bi at different temperatures below their melting points, to investigate the change in crystalline state under the ultrastrong gravitational field. For the Bi70Sb30 alloy ultracentrifuged at 191–205 °C, no change in composition was observed, and the grain sizes of the crystals decreased from several millimeters to tens of micrometers, while no distinct change in grain size was observed for the pure Bi ultracentrifuged under the same experimental conditions. The Bi70Sb30 alloy ultracentrifuged at 220–240 °C consisted of two regions with different morphologies–fine-grained crystals with grain sizes in ...

An atomic-scale graded structure was formed by the sedimentation of component atoms in an all-proportional miscible alloy under a strong gravitational field of 1 million g in maximum acceleration at high temperature. Continuous composition gradients of Sb (about 20–0 wt. %) and Bi (about 80–100 wt. %) and the resultant continuous change in the lattice constants were observed in the ultracentrifuged Bi–Sb (70:30 in mol %) alloy bulk body. Crystal growth in the direction of acceleration field was also observed. It must be noted that the substitutional solute atoms with component level rate acted in the sedimentation of this system, while interstitial solutes (Au) at an impurity level rate acted in some elemental metals with low melting temperature in the previous studies. It is expected that the sedimentation of substitutional atoms can be used to control the compositions and structure of alloys or compounds.

Inclined-mirror Hugoniot measurements were performed on pure AlN polycrystals in the pressure range up to 150 GPa to study the yield properties, phase transition, and equation of state. The Hugoniot-elastic limit (HEL) stress was approximately 9.4 GPa. Above the HEL, the Hugoniot data converged to a static compression curve despite the high thermal conductivity, which indicated that the thermal property is not an important factor in determining the shock yield property. The phase transformation from wurtzite-type (B4) to rock salt-type (B1) structure took place at approximately 19.4 GPa, and was completed by about 75 GPa. The corrected transition pressure at 298 K was 19.2 GPa. Shock velocity (Us) versus particle velocity (Up) relation of the final phase was given by Us=3.27+1.81Up km/s. The Birch–Murnaghan fitting curve of the calculated isothermal compression curve of the B1-type phase roughly coincided with the recent static x-ray diffraction data up to over 100 GPa. The Gruneisen parameter, bulk moduli (K0), and the pressure derivative (K0′) at zero pressure of the B1-type phase were estimated to be 1.51±0.03, 304±4 GPa, and 3.9±0.2 (K0″=−0.02), respectively.

Fully dense Sm2Fe17Nx bulk bodies with porosities less than 5% were prepared by shock compression in a certain low‐pressure region, using the magnetically aligned powder pellets with an initial porosity of 46%–52% and without binder. Below a driving shock pressure (single shock wave using a copper standard capsule) of about 10 GPa, the recovered specimens did not consolidate well, and above about 20 GPa they began to decompose to α‐Fe and Sm nitride. The consolidated state and porosity depended on the driving shock pressure, the thickness and porosity of the starting powder pellet, and the thickness of the impact plate. It was found that the shock consolidated bulk bodies had a Curie temperature of approximately 475 °C, and that the magnetic properties were sensitive to shock pressure, porosity, alignment, etc. The largest values of coercivity and maximum energy product of the recovered bulk specimens prepared in this study were 7.1 kOe and 16.8 MGOe, respectively.

Inclined‐mirror Hugoniot measurements of yttria (Y2O3) ‐doped (9.6 and 8.0 mol %) cubic zirconia single crystal and polycrystal were performed in the pressure range up to 120 GPa to study yielding and phase transition. The Hugoniot‐elastic limit (HEL) stresses parallel to the 〈100〉 and 〈110〉 axes were approximately 14 and 25 GPa, respectively, while that of the polycrystal was approximately 13 GPa. Above the HELs the Hugoniot data parallel toward the 〈100〉 and 〈110〉 axes converged on each other, and showed large relief to an isotropic compression state, while those of the polycrystal preserved a considerably larger shear strength. A phase transformation took place at approximately 53 GPa (both 〈100〉 and 〈110〉 axis directions), and was completed by about 70 GPa. The phase transition pressure was much higher than those of the monoclinic‐ or tetragonal‐orthorhombic II phase transitions under static compression. The shock velocity Us versus particle velocity Up relation of the final phase of the single crysta...

The Hugoniot data for highly dense polycrystalline tungsten were obtained for pressures above 200 GPa, and the equation of state (EOS) was determined taking into account shear strength effects. For this study, we have made some improvements in measurement system and analyses of the shock wave data. Symmetric-impact Hugoniot measurements were performed using the high-time resolution streak camera system equipped on a one-stage powder gun and two-stage light gas gun, where the effects of tilting and bowing of flyer plate on the Hugoniot data were carefully considered. The shock velocity–particle velocity (US–UP) Hugoniot relation in the plastic regime was determined to be US = 4.137 + 1.242UP km/s (UP

Strong oxides at high shock pressures have broad crossovers from elastic solids at ambient to failure by plastic deformation, to heterogeneous deformation to weak solids, to fluid-like solids that equilibrate thermally in a few ns, to melting and, at sufficiently high shock pressures and temperatures, to metallic fluid oxides. This sequence of crossovers in single-crystal cubic Gd3Ga5O12 (Gd-Ga Garnet-GGG) has been diagnosed by fast emission spectroscopy using a 16-channel optical pyrometer in the spectral range 400–800 nm with bandwidths per channel of 10 nm, a writing time of ∼1000 ns and time resolution of 3 ns. Spectra were measured at shock pressures from 40 to 290 GPa (100 GPa = 1 Mbar) with corresponding gray-body temperatures from 3000 to 8000 K. Experimental lifetimes were a few 100 ns. Below 130 GPa, emission is heterogeneous and measured temperatures are indicative of melting temperatures in grain boundary regions rather than bulk temperatures. At 130 GPa and 2200 K, GGG equilibrates thermally ...

Sedimentation of atoms induced under strong gravitational field gives a tool for controlling elemental compositions in condensed matter. We performed a strong-gravity experiment (0.397 × 106 G at 400 °C for 24 h) on a V2O5 polycrystal using the high-temperature ultracentrifuge to examine the composition change and further the structure change. The graded composition structure of V and O was formed along gravity direction, where V increases and O decreases with gravity. It was found by the x-ray diffraction and Raman scattering method that VO2 and V2O3 phases appeared and the amounts increased, while one of the V2O5 phase decreased gradually along gravity direction. The X-ray absorption near edge structure spectra analysis identified the chemical valency decrease (+5 to +3). The UV-Vis absorption spectroscopy addressed the shifting in center of major absorption peak to longer wavelength (red shift) with the increase in gravitational field. The tail absorption peak (band gap 2.09 eV) at strong gravity regio...

To investigate diffusion phenomenon at the interface between Cu and brass under a strong gravitational field generated by ultracentrifuge apparatus, we performed gravity experiments on samples prepared by electroplating with interfaces normal and parallel to the direction of gravity. For the parallel-mode sample, for which sedimentation cannot occur thorough the interface, the concentration change was significant within the lower gravity region; many pores were observed in this region. Many vacancies arising from crystal strain due to the strong gravitational field moved into the lower gravity region, and enhanced the atoms mobilities. For the two normal-mode samples, which have interface normal to the direction of gravity, the composition gradient of the brass-on-Cu sample was steeper than that for Cu-on-brass. This showed that the atoms of denser Cu diffuse in the direction of gravity, whereas Zn atoms diffuse in the opposite direction by sedimentation. The interdiffusion coefficients became higher in the Cu-on-brass sample, and became lower in the brass-on-Cu sample. This rise may be related to the behavior of the vacancies.

The Hugoniot data for zinc oxide (ZnO) single crystals were measured up to 80 GPa along both the ⟨ 112¯0⟩ (a-axis) and ⟨0001⟩ (c-axis) directions using a velocity interferometer system for any reflector and inclined-mirror method combined with a powder gun and two-stage light gas gun. The Hugoniot-elastic limits of ZnO were determined to be 10.5 and 11.5 GPa along the a- and c-axes, respectively. The wurtzite (B4) to rocksalt (B1) phase transition pressures along the a- and c-axes are 12.3 and 14.4 GPa, respectively. Shock velocity (Us) versus particle velocity (Up) relation of the final phase is given by the following relationship: Us (km/s) = 2.76 + 1.51Up (km/s). Based on the Debye-Gruneisen model and Birch-Murnaghan equation of state (EOS), we discuss the EOS of the B1 phase ZnO. The bulk modulus (K0) and its pressure derivative (K0′) are estimated to be K0 = 174 GPa and K0′ = 3.9, respectively.

Cubic, single-crystal, transparent Gd{sub 3}Ga{sub 5}O{sub 12} has a density of 7.10 g/cm{sup 3}, a Hugoniot elastic limit (HEL) of 30 GPa, and undergoes a continuous phase transition from 65 GPa to a quasi-incompressible (QI) phase at 120 GPa. Only diamond has a larger HEL. The QI phase of Gd{sub 3}Ga{sub 5}O{sub 12} is more incompressible than diamond from 170 to 260 GPa. Electrical conductivity measurements indicate the QI phase has a bandgap of 3.1 eV. Gd{sub 3}Ga{sub 5}O{sub 12} can be used to obtain substantially higher pressures and lower temperatures in metallic fluid hydrogen than was achieved previously by shock reverberation between Al{sub 2}O{sub 3} disks. Dynamic compression achieves pressures, densities, and temperatures that enable investigation of ultracondensed matter at conditions yet to be achieved by any other technique. The prototypical example is observation of minimum metallic conductivity (MMC) of dense fluid hydrogen at 140 GPa, nine-fold compression of liquid density, and {approx}3000 K [1-3]. The high pressure and density and relatively low temperature are achieved by multiple-shock compression [2]. Temperature T is relatively low in the sense that T/TP{sub F} {approx} 0.01, where T{sub F} is the Fermi temperature. The time scale of compression is sufficiently long tomore » achieve thermal equilibrium and sufficiently short so the process is adiabatic. Similar results are obtained for oxygen [4] and nitrogen [5]. Fluid Cs and Rb undergo the same transition at 2000 K near their liquid-vapor critical points [6]. All five elemental fluids have essentially the same value of MMC and the density dependences of their semiconductivities scale with the quantum-mechanical charge-density distributions of the respective atoms [5]. Liquid H{sub 2} is one of the most compressible of all materials. In this paper, we report that the dielectric crystal Gd{sub 3}Ga{sub 5}O{sub 12} (GGG) transitions to a virtually incompressible phase at 120 GPa shock pressure.« less

Observations of the free-surface behavior under shock compression by the gapped-flat mirror method were performed on B4C and Si3N4 ceramics to study their shock-yielding properties. Jagged profiles of the moving free-surface in the plastic region, with a special scale of about one mm and a maximum local displacement of a few 10s of μm, were observed for B4C polycrystals. Similar profiles for Si3N4 polycrystals were smooth. Such profiles for B4C polycrystals were also observed in the elastic region. It is suggested that these observations reflect the heterogeneous nature of shock compression in solids, and further indicate that a macroscopic slip system plays an important role in the elastoplastic transition of B4C material under shock compression and decompression.

The particle velocity profiles of an MgO single crystal under shock compression were measured up to a pressure of 35 GPa by a velocity interferometer system for any reflector using a LiF window combined with a powder gun. The Hugoniot-elastic limit (HEL) of MgO along the ⟨100⟩ direction was 2.9–4.3 GPa and the initial elastic waves contain some oscillations. Along the ⟨110⟩ direction, the HEL was higher than along the ⟨100⟩ direction and anomalous, two-step-structure elastic waves were observed. These characteristics are discussed based on the slip system of the MgO crystal.

Iron oxide nanoparticles have attracted much attention over the last few years owing to their fundamental importance and technological applications. In this work, spherical ferromagnetic Fe3O4 nanoparticles with an average diameter of 19 nm were synthesized by a simple and one-step method, pulsed plasma in liquid. Pulsed plasma, induced by a low-voltage spark discharge, was submerged in a dielectric liquid at a voltage of 200 V, a current of 6 A, a frequency of 60 Hz, and a single discharge duration of 10 µs. Water with different concentrations of 1-hexadecylpyridinium bromide (CPyB) was applied as a liquid, and several experiments made evident that the surfactant concentration affects the phase compositions of the produced materials. The purity of the magnetite phase in the sample increased (from 65 to 98%) with increasing CPyB concentration (from 0.10 to 0.84 g) in 200 ml of water. The crystal structure of magnetite (Fe3O4) nanoparticles with the F d3̄m space group and a lattice parameter of a = 0.8393 nm was evident from X-ray diffraction results. Magnetite nanoparticles were investigated further by high-resolution transmission electron microscopy/energy-dispersive spectroscopy and thermogravimetrical analysis, and using a vibrating sample magnetometer.

Fe and Ni magnetic nanoparticles coated by carbon were synthesized between the Fe–Fe and Ni–Ni metal electrodes, submerged in ethanol using pulsed plasma in a liquid method. Iron coated carbon (Fe@C) nanoparticles have an average size of 32 nm, and Ni@C nanoparticles are 40 nm. Obtained samples exhibit a well-defined crystalline structure of the inner Fe and Ni cores, encapsulated in the graphitic carbon coatings. Cytotoxicity studies performed on the MCF-7 (breast cancer) cell line showed small toxicity about 88–74% at 50 µg/mL of Fe@C and Ni@C nanoparticles, which can be significant criteria for use them in medical cancer treatment. In addition, appropriate sizes, good magnetic properties and well-organized graphitic carbon coatings are highlight merits of Fe@C and Ni@C nanoparticles synthesized by pulsed plasma.

It is hard to generate twin defects in wurtzite-type ZnMS (M: metal element) crystals by static mechanical method, while it is important for the luminescence. It was found that many twin defects were formed in wurtzite-type ZnMgS crystals by shock compression of >15 GPa in stress, and the absorption and luminescence spectra changed.

Wurtzite-type ZnMgS (w-ZnMgS) nanoparticles were synthesized using the pulsed plasma in liquid method. By the pulsed plasma generated between two electrodes made of ZnMg alloy in liquid sulfur, we produced w-ZnMgS nanocrystals mixed with Zn2Mg and MgS. Higher purity w-ZnMgS sample was achieved by annealing at 773 K. The synthesized ZnMgS nanoparticles were of spherical shape and contained of many crystal defects (stacking faults). Ultraviolet–visible (UV–vis) absorption spectroscopy analysis of the synthesized w-ZnMgS showed absorption edge broadening and appearance of a small absorption band at around 400 nm even without doping.

Beginning with homogeneous samples of the superconducting phase Y1Ba2Cu3O7−x (Y123), we examined changes in structure and composition under a strong gravitational field and temperatures remarkably lower than the Y123 melting point. We observed essentially two-layers with different compositions caused by sedimentation of atoms. The layer exposed to the stronger gravitational field is composed of an Y123 phase that has a smaller unit cell volume compared with the initial sample, green, transparent, large single crystals of Y211, and a BaCuO2 phase. Despite the remarkably lower temperature, compositional and structural changes in addition to decomposition were found. The unit cell volume of the Y211 phase was larger than previously indicated by synchrotron x-ray diffraction (XRD) analysis. Refinement of the Y211 structure from the XRD data also showed that these crystals are very perfect due to a very high extinction coefficient 0.7(9)×10−6 and symmetrical arrangement compared with the superconducting phase ...

The high-time-resolution streak photographic system equipped with a powder gun and a two-stage light gas gun has been constructed for the Hugoniot measurement of solids at pressures up to >300 GPa. For this system, a compact rotating-mirror-type streak camera and a long-pulsed dye laser with no Q-switch were produced. A time resolution higher than 1 ns was achieved by using a 2-µm-wide slit of the camera formed using the laser. The shock velocity and particle velocity of steady shock waves of the materials with a shock velocity of ~6 km/s can be measured by the inclined-mirror method with the basic errors of 0.2 and 0.1–0.2%, and 0.2 and 0.35–0.45% for symmetrical and asymmetrical impact, respectively, depending on shock velocity and impact velocity.

Pure tin metals were centrifuged at 1 × 106g and at 220°C for 100 hours, at 0.40 × 106g at 220–230°C for 24 hours, and at 0.25 × 106g at 220°C for 24 hours. Their isotopic compositions were measured by a secondary ion mass spectrometer (SIMS). 116Sn/120Sn and 124Sn/120Sn ratios of the 1.02 × 106g sample were considerably different than the initial compositions, and the magnitude of isotopic fractionation reached 2.6 ± 0.1%. A three-isotope diagram of 116Sn/120Sn vs. 124Sn/120Sn shows conclusively that isotopic fractionation caused by a gravitational field depended only on the isotopic mass.

A strong gravitational field resulted in the gravity-induced diffusion (sedimentation) of isotope atoms in monoatomic solid Se. The layer crystalline morphology consisting of three zones of the fine-grained crystals, the long crystals and feather-shaped crystals grown parallel to gravity direction appeared in the specimen ultracentrifuged at (0.8–1)×106 G and at 190 °C. Change in the concentration ratio 82Se/76Se of >0.8% was observed in the grown crystalline region. These results show an evidence for the sedimentation of substitutional atoms in solids via self-diffusion, and suggest the possibility of application to the control of impurity and crystalline states as well as to isotope separation.

A large linearly graded structure on atomic scale up to 88 at. %/mm with oriented grown crystals was formed in selenium-tellurium (Se-Te) semiconductor using a strong gravitational field of one million G level at 260 °C. The lattice constants and the binding energies of Se and Te 3d electrons continuously changed along the direction of gravity accordingly, which indicated the formation of the graded band gap structure. The grown crystals showed the crystalline orientation with the c axis of hexagonal structure roughly perpendicular to the direction of gravity. It was found that the diffusion coefficient of sedimentation was larger than that of normal diffusion by more than 100 times, which suggested a different diffusion mechanism from the normal vacancy mechanism.

Molecular dynamics simulations of dislocations behavior in KCl crystal under uniaxial compression along the [100], [110], and [111] axis directions were performed to discuss the elastoplastic transition under shock compression. The simulation results showed that the dislocation moved along about 45 deg to the uniaxial compression direction through the displacements of atomic lines around the dislocation core. Under uniaxial compression along the [111] axis direction, two extra half-(011) planes were inserted as dislocations in KCl crystal. The minimum stress for dislocation motion under the uniaxial compression along the [111] axis direction was much larger than those under the uniaxial compressions along the [100] and [110] axis directions. It was suggested that the large minimum stress for dislocation motion along the [111] axis direction was caused by the existence of two edge dislocations which were inserted as extra half-(011) planes. This anisotropic behavior was consistent with the experimental measurement of Hugoniot-elastic limit.

Hugoniot measurements on the highly dense, pure B4C polycrystal were performed by the inclined-mirror method to study the elastoplastic transition and to search phase transition. In inclined-mirror streak photographs, the smoothly jagged structure was observed at the free-surface shape in the plastic region. The Hugoniot-elastic limit (HEL) has been determined to be approximately 19.5GPa. In the plastic region, a kink was observed at a particle velocity of around 1.26km∕s. The shock velocity (US)–particle velocity (UP) Hugoniot relations in the plastic region were given by US=3.7+5.4UPkm∕s in the Up range of 0.54–1.26km∕s and US=9.61+0.73UPkm∕s in the Up range of 1.26–4.3km∕s. The S value (0.73) in US=C0+SUP above UP=1.26km∕s is significantly small compared with the result of Vogler et al. [J. Appl. Phys. 95, 4173 (2004)], and was much smaller than those of many oxides and nitrides. This material behaved as an elastoisotropic solid above the HEL and showed a large and linear change in the pressure-density...

The behavior of atoms in a solid under a strong acceleration field of around 1 million (106) g at high temperature (mega-gravity field) was examined. The ultracentrifuge experiment was performed on an antimony (Sb)-bismuth (Bi) system solid alloy in a maximum acceleration field of (0.85–1.03)×106 g at 220–240° C for 85 hours. Large composition gradients of Sb (about 20–0 wt%) and Bi (80–100 wt%) and the continuous changes in lattice parameters were observed at that location where the external energy was comparable to or larger than the thermal energy. This result provides the first evidence of the sedimentation of component atoms in a solid.

A thin-type manganin piezoresistance gauge was calibrated for the highly time-resolved measurements of the stress histories under shock compression of solids in the several 10 s of GPa region. The final total gauge thickness can be reduced to 25-30 µm to improve time resolution. The calibration experiments were performed using alumina stress medium by means of the inclined-mirror method using a new high-speed streak camera combined with a powder gun. The stress histories in alumina polycrystal were measured, in which the elastoplastic transitions were detected at rise and release. The relationship between the resistance change and shock stress was closely described as ΔR/R 0=-0.0329+0.0276σ x (R 0: zero pressure resistance, ΔR: resistance change, and σ x : peak shock stress). It was confirmed that the present modified gauge was applicable in the pressure range up to over 40 GPa.

The explosive‐driven magnetic flux cumulation process by the convergence of high‐pressure shock waves in highly porous metal powders has been studied experimentally. The field‐multiplication ratio depends mainly on the initial density of powder, although the flux compression signal has been detected for all the powders tested. Extremely light aluminum powders of initial density, of about 0.41 g/cm3 is shown to be the most promising within this experiment. The time evolution of flux density, i.e., B(t) for the case of light metal powders (Al and Mg), can be well approximated by the inverse power law. The results are explained by the magnetohydrodynamic theory.

The electrical response of BaTiO3 ceramics to the strong shock compression well above the Hugoniot‐elastic limit or ferroelectric‐paraelectric transition pressure is studied to separate and identify the causes of shock‐induced electrical response of ferroelectric materials. Measurements of voltage and current histories under shock compression are performed by using poled and nonpoled specimens, assemblies of both parallel and normal modes, and explosive systems. In order to consider the effects due to elastic‐plastic deformation and shock‐induced conduction, the Hugoniot compression curve and electrical conductivities are also measured by using nonpoled specimens. The Hugoniot‐elastic limit stress is determined to be 4.8–6.4 GPa for porous specimens with 1.7–4.4% porosity, and the shock velocity (Us) and particle velocity (Up) Hugoniot can be closely described as Us =4.29+1.66Up km/s in the plastic region. The electrical conductivity values at 12‐ and 29‐GPa peak stresses are measured to be 2.1×10−3 and 4...

Anisotropic elastic limits and phase transitions of the rutile phase TiO2 under shock compression are studied, on the basis of the measurements of particle‐velocity histories and free‐surface motions along the [100], [110], and [001] axis directions in the stress range up to 38.6 GPa. The stresses of Hugoniot elastic limit (HEL) along the [100] and [001] axis directions are determined to be 7.8±0.5 and 4.1±0.3 GPa, respectively. These different HEL stresses are reasonably analyzed by an inherent yield stress of 3.0±0.3 GPa. A Hugoniot kink at 12.2±0.6 or 17.0±0.7 GPa along the [100] or [110] axis direction, respectively, and two kinks at 10.6±0.5 and 33.7±1.3 GPa along the [001] axis direction are observed. Considering the volume changes and the recovery experiments of α‐PbO2 phase, two former ones and the last one are suggested to correspond to the beginning of phase transitions to a α‐PbO2 phase and a hexagonal phase, respectively. These anisotropic behaviors clearly show the typical evidences of the un...

Elastoplastic properties of Al2O3 single crystal (14–38 GPa) and polycrystal (6–33 GPa) under shock compression were studied by the measurements of Hugoniot compression curves and stress histories. The Hugoniot‐elastic limit (HEL) stresses were determined to be 14.4–17.3 GPa for single crystals and 6.7–9.6 GPa for polycrystals with 2.7%–3.2% porosity. In the plastic region, the single‐crystal Hugoniot stresses, at a given density, exceed the isothermal x‐ray static data and its extrapolation by 6.5–8 GPa. And, the polycrystalline Hugoniot data exceeds, at a given density, the single‐crystal Hugoniot data by about 1 GPa. These Hugoniot offsets are not caused by temperature increase, but rather by the shear strength and the remaining porosity. The stress histories of a single crystal show very similar shapes to that of a perfect elastoplastic material. The apparent yield stresses of single crystal at the HEL and in the plastic region are estimated to be 9.5–12 GPa and 4–6 GPa, from the HEL data and the quasirarefaction shock in the stress histories, respectively. As a result, it is concluded that both Al2O3 single crystal and polycrystal behave as quasi‐elastoplastic material with some loss of shear strength, unlike many other brittle materials (elastoisotropic material with large catastrophic loss) such as Si, SiO2, etc. Furthermore, the present results suggest that the packing state and bonding state of crystal should be also ranked among the factors deciding the heterogeneous shock yielding of brittle materials, in addition to the thermophysical properties, which are related to the shear banding phenomenon or the other yielding mechanism.

The response of a copper‐Constantan sheet couple 50–60 μm thick to shock compression up to 81 GPa is studied. The results are consistent with the bulk junction results of Bloomquist et al. at pressures up to about 40 GPa, and with ones obtained from the calculated shock temperature above this pressure with an error of less than 15%.

An anomalously high Hugoniot‐elastic limit of 35–39 GPa in stress was measured by the inclined‐mirror method for the Y2O3‐doped partially stabilized zirconia ceramics. This value is much higher than for stabilized zirconia ceramics by over two, and is the second highest in these materials which have ever been measured. As a result, it is suggested that transformation toughening of the partially stabilized zirconia strongly influences the material strength even under shock compression, as under static conditions.

This system has been developed for the purpose of precise observations of shock-compression states at pressures higher than several 10s of GPa in solids. Plane impact experiments within an impact tilt-angle of 0.2 degrees, in which the impact velocity can be measured within an error of 0.5% by the X-ray beam cut-off method, are made practicable. Particle-velocity histories at two points were measured by the electromagnetic-gauge technique, within an error of 2% up to a pressure of 59.4 GPa in sapphire and stabilized zirconia.

A measurement system for both longitudinal and shear waves in solids under shock compression in several 10 s of GPa region has been developed. In this system, combined compression-shear waves in solids are generated by the oblique-parallel-plate impact method using the keyed-powder gun, which is capable of accelerating a projectile without rotation to velocities of over 2 km/s. The particle-velocity histories of both longitudinal and shear waves are measured by an electromagnetic gauge method using pulsive-oblique magnetic field and Faraday gauges.