Multi-anvil High-pressure Apparatus Research Articles

Peculiar high-pressure behavior in permanent densification of fluorozirconate glass

A 60ZrF 4·30BaF 2·10EuF 3 glass was densified under 1.5, 3.0, 4.5, 6.0, and 9.0 GPa at 250°C using a 6–8-type multi-anvil high-pressure apparatus. The densities of permanently densified glasses exhibit a maximum value at the 3.0 GPa treatment and then a marked decrease with increasing pressure. Such a peculiar permanent densification behavior, being reported for the first time to the best of our knowledge, is discussed based on the F − coordination environments around Zr 4+, Eu 3+, and Ba 2+. This behavior may be attributed to a spontaneous structure-relaxation.

Experimental investigation of the ?-? transformation of San Carlos olivine single crystal

Single crystalline San Carlos olivine (1 mm cube) was transformed to (Mg,Fe)2SiO4β-phase at 13.5–15 GPa, 1030–1330 °C for 0–600 min using a multi-anvil high pressure apparatus. The α-β transformation occurred by incoherent surface nucleation and interface-controlled growth and recovered partially transformed samples showed sharply defined reaction rim. The growth rate of the β-phase rim significantly decreased with time and the growth eventually ceased. TEM observations revealed that many dislocations were created in both the relict olivine just near the α-β interface and the β-phase in the rim, which show evidence for deformation caused by interfacial stresses associated with the misfit elastic strain of the transformation. The observed tangled dislocation texture in β-phase suggested that the β-phase rim was hardened and relaxation of the interfacial stress was retarded. This probably caused a localized pressure drop in the relict olivine and decreased the growth rate. Time-dependent growth rates of β-phase is possibly controlled by the rheology of β-phase, which must be considered for the prediction of the olivine metastability in the subducting slabs.

IN SITU STUDIES OF THE PROPERTIES OF MATERIALS UNDER HIGH-PRESSURE AND TEMPERATURE CONDITIONS USING MULTI-ANVIL APPARATUS AND SYNCHROTRON X-RAYS

▪ Abstract Increased access to multi-anvil high-pressure devices interfaced to synchrotron X-ray radiation sources has led to a new class of experiments. These new capabilities include (a) high-precision crystal structure determination and refinement from powder X-ray diffraction data; (b) the determination of kinetic parameters and structure from time-resolved diffraction data; (c) the determination of absolute pressures by the combined use of ultrasonic techniques at high pressures and temperatures with simultaneous monitoring of X-ray diffraction; and (d) the determination of the strength and rheological properties of materials through the monitoring of the relaxation of broadened diffraction peak widths in the presence of a well-characterized deviatoric stress field generated in the multi-anvil high-pressure apparatus.

Melting relations of hydrous and dry mantle compositions and the genesis of komatiites

The hydrous phase relations of primitive upper mantle model compositions in the CaO‐MgO‐Al2O3‐SiO2‐H2O system with 1, 2 and 5 wt.% H2O have been investigated with a multianvil high pressure apparatus at 6.5 GPa and temperatures from 1550°C to 2050°C. Liquidus temperatures decrease by about 100°C and the temperature interval to produce about 60% partial melting reduces to less than 50°C in the 1–2 wt.% H2O‐bearing systems. At an H2O content of about 5 wt.%, garnet is the first dissolved phase and the stability field of orthopyroxene expands. Aluminum undepleted komatiite magmas can be formed by melting at 200 km depth in a hydrous mantle at significantly lower temperatures than under dry conditions. Thus, komatiite magmas cannot constrain temperatures in the Archean mantle. In addition, cratonic peridotites may have formed as residues of partial melting under various H2O contents.

The postspinel phase boundary in Mg2SiO4 determined by in situ X-ray diffraction

The phase boundary between spinel (gamma phase) and MgSiO3 perovskite + MgO periclase in Mg2SiO4 was determined by in situ x-ray measurements by a combination of the synchrotron radiation source (SPring-8) and a large multianvil high-pressure apparatus. The boundary was determined at temperatures between 1400 degrees to 1800 degreesC, demonstrating that the postspinel phase boundary has a negative Clapeyron slope as estimated by quench experiments and thermodynamic analyses. The boundary was located at 21.1 (+/-0.2) gigapascals, at 1600 degreesC, which is approximately 2 gigapascals lower than earlier estimates based on other high-pressure studies.

Electrical Conductivity Measurement of Minerals at High Pressures and Temperatures.

The method is described which utilizes slow (10-100 mHz) AC current to determine the electrical conductivity of ferromagnesian minerals at pressures up to 23 GPa and temperatures of 300-2000 K in the 6-8 type multi-anvil high-pressure apparatus. The oxidation state of the sample is controlled just below IW buffer. The range of electrical conductivity which can be measured using the present method is 100Ω-5MΩ. An example of measurement was conducted for Mg0. 93Fe0. 07SiO3 ilmenite.

Sound Velocity Measurements in Oxides and Silicates at Simultaneous High Pressures and Temperatures using Ultrasonic Techniques in Multi-Anvil Apparatus in Conjunction with Synchrotron X-radiation Determination of Equation of State.

Ultrasonic techniques for multi-anvil high-pressure apparatus are adapted for use in a DIA-type cubic-anvil apparatus (SAM 85) and installed on the superconducing wiggler beamline (X17B) at the National Synchrotron Light Source of the Brookhaven National Laboratory. Sound wave velocities and lattice parameters have been measured on samples of polycrystalline alumina (GE Lucalox and Coors 998) to simultaneous pressures of 9 GPa and 800 K

Phase equilibria for the Fe 2 SiO 4 -Fe 3 O 4 system under high pressure

High pressure phase relation of the system Fe2SiO4–Fe3O4 was investigated by synthesis experiments using multi-anvil high pressure apparatus. A complete solid solution with spinel structure along Fe2SiO4–Fe3O4 join occurs above 9 GPa at 1200 °C. Lattice constants of the solid solution show almost linear variation with composition. A spinelloid phase is stable for intermediate compositions in the pressure range from 3 to 9 GPa. the synthesized spinelloid phase is successfully indexed assuming nickel aluminosilicate V type structure.

Evaluation of the non-hydrostatic stress produced in a multi-anvil high pressure apparatus

Olivine single crystals have been deformed under high confining pressure (P=5 GPa) and temperature (T=1400 °C) conditions in a multi-anvil high pressure apparatus. NaCl, diamond and NaCl+diamond (2:1 by volume) powders were encapsulated along with the olivine single crystals in order to produce a range of stress states. The change of the non-hydrostatic stress transmitted to the olivine samples, enclosed within these three different media, during heating has been evaluated by observation of dislocation microstructure and density. A higher differential stress can be generated with diamond powder (0.1 GPa) than with NaCl powder (0.02 GPa). Although an intermediate differential stress between 0.1 GPa and 0.02 GPa had been expected to be generated using NaCl+diamond powder, the generation of non-hydrostatic stress in the olivine sample was unsuccessful. This may be caused by the fact that compaction (or sintering) proceeded in the capsule throughout the experiments. The most important finding of these experiments is that a constant non-hydrostatic stress can be applied to a sample under very high pressure and temperature conditions within the multi-anvil high pressure apparatus for the duration of the experiment. This approach is therefore suitable for investigating the steady-state rheological properties of mantle minerals at near-mantle conditions.

鉱物―マグマ間の元素分配に対する圧力の影響 その構造との関連性

Element partitioning between minerals and silicate melt has been investigated at pressures 1-17 GPa, by using 6-8 type multi anvil high pressure apparatus. The observed partition coefficients, D, were plotted on partition coefficient - ionic radius (PC-IR) diagram. In the case of olivine/silicate-melt system, partition coefficient of most of the elements gradually decreased with increasing pressure. However, partition coefficient of Al increased with increase in pressure, and this result may be suggesting that partition coefficient of Al may depend on the composition and structure of the coexisting silicate melt. It was difficult to identify peaks of partition coefficient profile in majorite / silicate-melt system. There was a bottom of the partition coefficient profile of Ca-perovskite / silicate-liquid at around 70-80 pm, and the existence of peaks at around 50 and 100 pm is expected from the observed profile of partition coefficient.

Pressure dependence of Ni, Co and Mn partitioning between iron hydride and olivine, magnesiowüstite and pyroxene

The partitioning of Mn, Co and Ni between iron hydride and mantle minerals (olivine, pyroxene and magnesiowüstite) was experimentally investigated at 1400 °C and 3–11 GPa using a cubic-anvil and 6–8 multi-anvil high-pressure apparatus. At atmospheric pressure (0.1 MPa), it is well known that Co and Ni concentrate in the metallic phase and Mn concentrates in oxide phases. However, the present experimental results show that the siderophile nature of Co and Ni, and the lithophile nature of Mn decrease at high pressures. The observed exchange partition coefficient, K D = ( X M X Fe ) Metal ( X M X Fe ) Mineral , for the pure-metal-mineral system without hydrogen are a little lower than those for the metal-hydride-mineral system, but the difference in K D between these systems is very small. It has been pointed out that the abundance of siderophile and chalcophile elements in the Earth's upper mantle cannot be explained by metal-silicate equilibrium when partition coefficients determined at atmospheric pressure are used. From the present experimental results, however, it is expected that partition coefficients of Mn increase, and those of Co and Ni decrease in the Earth's deep interior, and that observed upper-mantle elemental abundances of these elements may be explained by equilibrium partitioning between metal and silicates at extremely high pressure. When we compare the geochemical characters of Earth, Moon, Shergottite parent body and Eucrite parent body, it is found that the apparent partition coefficients of these terrestrial bodies systematically change with change in size of the planet. This observation suggests that the pressure effect on K D values played an important role in the chemical evolution of the terrestrial planets.

Origin of Cratonic Peridotite and Komatiite: Evidence for Melting in the Wet Archean Mantle.

We have conducted melting experiments of pyrolite containing 1 and 2wt.% of water at 6.5GPa by a multianvil high pressure apparatus. We observed melting at temperatures above 1550°C and 1700°C for pyrolite+2%H2O and pyrolite+1%H2O respectively at 6.5GPa. A small amount of water reduces the solidus temperature by 250-100°C. Another important observation is expansion of the stability field of orthopyroxene above the solidus, and reduction of the stability field of olivine+liquid. The present observation of expansion of the orthopyroxene stability field above the solidus at 6.5GPa implies that the harzburgite residue can be formed by partial melting of the primitive mantle under the hydrous conditions at the depth of around 200km. Hydrous melting is a key process to fill the missing link between the cratonic peridotite and komatiite; i.e., cratonic peridotite was formed as a residue of the komatiite extraction in a wet Archean mantle.

Element partitioning between olivine and silicate melt under high pressure

Element partitioning between olivine and silicate melt has been investigated at pressures 1–14 GPa, by using a 6–8 type multi-anvil high pressure apparatus. In order to observe systematics in the partitioning of trivalent ions, Li was added to the starting materials in order to increase the concentration of trivalent ions in olivine. With increasing pressure, it was found that partition coefficients of most of the elements gradually decreased. Trivalent ions generally showed parabolic pattern on partition coefficient — ionic radius diagram. When pyrolite-like material was used as the starting material, partition coefficient of Al, DAl, gradually increased with increase in pressure while the partition coefficients of the other elements decreased, and the DAl deviated from the parabolic pattern of other trivalent ions. The deviation of DAl from the D pattern of the other trivalent ions was also found when olivine was employed as main component of the starting material. This result may be ascribed to the compositional change of coexisting silicate melt with increase in pressure.

Use of a New Diamond Composite for Multianvil High-pressure Apparatus.

A newly developed diamond composite (Advanced Diamond Composite, ADC) was tested as the anvil material for a double-stage multianvil (MA6-8) apparatus. Pressures over 30GPa at room temperature were produced at relatively small press loads without any significant damages on the ADC anvils. The ADC anvil was found to be more transparent to X-ray beams of a wide range of energy as compared with a competitive sintered polycrystalline diamond (SYNDIE), and is accordingly suitable for an X-ray window under pressure. Electrical resistivity of ADC, however, is higher by about one order of magnitude than that of SYNDIE, which would restrict its use as a lead for electric power supply to the furnace. A hybrid anvil system with four ADC anvils plus four tungsten carbide anvils, the latter being used as the electric leads, was introduced for high temperature runs. This system has enabled to generate temperatures to 1500°C at pressures of 25-33GPa and to synthesize high-pressure phases relevant to the lower mantle mineralogy.

Dehydration of brucite (Mg(OH)2) at high pressures detected by differential thermal analysis

The differential thermal analysis (DTA) technique has been applied in a multi‐anvil high‐pressure apparatus to study the dehydration reaction of brucite (Mg(OH)2) to periclase (MgO) plus H2O at 4 to 6 GPa. At 4 GPa and 1030°C, endothermic and exothermic peaks due to dehydration and rehydration were observed during heating and cooling cycles, respectively. These peaks were shifted to higher temperature with increasing pressure (1080°C at 5 GPa; 1120°C at 6 GPa), suggesting that the reaction has a positive dT/dP slope within this pressure range. The stability of brucite under deep mantle condition is discussed.

A new high-pressure form of MgAl2O4

MAGNESIUM aluminium spinel (MgAl2O4) is a common constituent of low-pressure peridotite xenoliths, and is an important host mineral for aluminium and other trivalent cations in the shallow upper mantle. Shock-wave compression data for MgAl2O4 demonstrated1 that spinel would transform to denser phases at pressures greater than 40 GPa, although there was much uncertainty in the pressure estimation. Later, spinel was found to transform under static compression to the denser oxide mixture (MgO periclase + A12O3 corundum2,3) at pressures above 15 GPa (ref. 4). Detailed analyses of the shock-compression data, however, suggested the presence of a still denser phase of MgAl2O4 spinel at much higher pressures5,6. Here we report the transformation of MgAl2O4 spinel to a new high-pressure form at pressures above 25 GPa in a multi-anvil high-pressure apparatus. The new MgAl2O4 phase has a structure similar to that of CaFe2O4(calcium ferrite) and its zero-pressure density is 3.937(3) g cm-3, which is ∼2% denser than the lower-pressure assemblage of periclase + corundum. We suggest that this high-pressure form of MgAl2O4 may be an important host of aluminium in the Earth's lower mantle.

Development and Practical Performance of Enlarged, Multi-Anvil Link-Type Cubic High-Pressure Apparatus

Development and Practical Performance of Enlarged, Multi-Anvil Link-Type Cubic High-Pressure Apparatus

High-pressure X-ray diffraction studies on β- and γ-Mg 2SiO 4

Pressure effects on the lattice parameters of β- and γ-Mg 2SiO 4 have been measured at room temperature and at pressures up to 100 kbar using a multi-anvil high-pressure X-ray diffraction apparatus. The volume changes ( ΔV/ V 0) at 90 kbar are 5.4 · 10 −2 and 4.2 · 10 −2 for β- and γ-Mg 2SiO 4, respectively. Isothermal bulk moduli at zero pressure have been calculated from least-square fits of the data to straight lines. They turn out to be 1.66 ± 0.4 and 2.13 ± 0.1 Mbar for β- and γ-Mg 2SiO 4, respectively. The α → γ transition obeys Wang's linear V φ − ρ relation but the α → β transition does not.

Pressure distribution in a multianvil high-pressure device

Pressure distribution in an octahedral pressure medium (pyrophyllite) placed in a multianvil (eight-anvil) high-pressure apparatus was measured by applying phase transitions in the calibrated metal (bismuth). It has been shown that the pressure at the edge of the octahedral medium is about 14% lower than that at the centre, where the pressure is 25.2 kbar. Confirmation is presented, showing that the distribution is improved when the pressure generated in the medium is increased, and a reasonable uniform pressure distribution is found at the pressure of 77.0 kbar.

Effect of Pressure on the Decay Constant ofTc99m

An experimental investigation of the influence of high hydrostatic pressure on the decay constant of $^{99m}\mathrm{Tc}$ has been performed. By the use of a multianvil high-pressure apparatus, a carrier-free source of $^{99m}\mathrm{Tc}$ was compressed at a pressure of 100 kbar. The observed decay rate of the compressed $^{99m}\mathrm{Tc}$ source was compared with that of a standard $^{99m}\mathrm{Tc}$ source in the normal uncompressed state. The fractional increase in the decay constant, $\frac{\ensuremath{\Delta}\ensuremath{\lambda}}{\ensuremath{\lambda}}$, of the compressed $^{99m}\mathrm{Tc}$ under that pressure was found to be (4.6 \ifmmode\pm\else\textpm\fi{} 2.3) \ifmmode\times\else\texttimes\fi{} ${10}^{\ensuremath{-}4}$. Our result agrees with that observed by Bainbridge, $\frac{\ensuremath{\Delta}\ensuremath{\lambda}}{\ensuremath{\lambda}}=(2.3\ifmmode\pm\else\textpm\fi{}0.5)\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}4}$, to within a factor of about 2. Comparison with theoretical studies by other workers is also discussed.