Drickamer Apparatus Research Articles

Erratum to: High-pressure and high-temperature deformation experiments on polycrystalline wadsleyite using the rotational Drickamer apparatus

Erratum to: High-pressure and high-temperature deformation experiments on polycrystalline wadsleyite using the rotational Drickamer apparatus

The effects of shear deformation on planetesimal core segregation: Results from in-situ X-ray micro-tomography

It is well accepted that the Earth formed by the accretion and collision of small (10–100 km), rocky bodies called planetesimals. W-Hf isotopic evidence from meteorites suggest that the cores of many planetesimals formed within a relatively short time frame of ~3 My. While a very hot, deep magma ocean is generally thought to have been the driving mechanism for core formation in large planetary bodies, it inadequately explains differentiation and core formation in small planetesimals due to temperatures potentially being insufficient for wide-scale silicate melting to occur. In order for these planetesimals to differentiate within such a relatively short time without a magma ocean, a critical melt volume of the metallic (core-forming) phase and sufficient melt connectivity and grain size must have existed to attain the required permeability and lead to efficient core formation. Shear deformation may increase the connectedness of melt and the permeability, and thus could have been a major contributing factor in the formation of planetesimal cores. This deformation may have been caused by large impacts and collisions experienced by the planetesimals in the early solar system. The purpose of this work is to test the hypothesis that shear deformation enhances the connectivity and permeability of Fe-S melt within a solid silicate (olivine) matrix, such that rapid core formation is plausible. A rotational Drickamer apparatus (RDA) was used to heat and torsionally deform a sample of solid olivine + FeS liquid through six steps of large-strain shear deformation. After each deformation step, X-ray microtomographs were collected in the RDA to obtain in situ three-dimensional images of the sample. The resulting digital volumes were processed and permeability simulations utilizing the lattice Boltzmann method were performed to determine the effect of shear deformation on connectivity and permeability within the sample. The resulting permeabilities of the sample at various steps of deformation are the same within uncertainty and do not exhibit a change with increasing deformation. Additionally, the migration velocity calculated from the permeability of the sample is not high enough for segregation to take place within the time frame of ~3 My. In addition to further constraining the mechanism of core formation in planetesimals, the image processing techniques developed in this study will be of great benefit to future studies utilizing similar methods.

High-pressure and high-temperature deformation experiments on polycrystalline wadsleyite using the rotational Drickamer apparatus

High-pressure, torsional deformation experiments on polycrystalline wadsleyite were carried out using the rotational Drickamer apparatus (RDA). The experimental conditions ranged between temperatures of ~2000–2200 K at pressures of ~20 ± 1 GPa. Prior to deformation, the fine-grained (1–5 µm) wadsleyite specimens were synthesized from San Carlos olivine in a Kawai-type multi-anvil apparatus. The samples were loaded in the RDA, pressurized and heated, and deformed at stepped strain rates of 5–60 × 10−6 s−1. The stress was determined through the analysis of the orientation dependence on changes in lattice spacing for the (141), (240) and (040) planes. The strain was determined from the orientation of a molybdenum strain marker. Most stepped strain-rate tests reveal the stress exponent n to be 4.7 ± 0.5, suggesting power-law dislocation creep operated. Various samples exhibit grain-size reduction (to 0.1–0.6 µm), possibly associated with dynamic recrystallization or with partial phase transformation to ringwoodite. Transmission electron microscopy and electron backscatter diffraction analyses provide information on the dominant slip system in wadsleyite as 1/2〈111〉 slip on {101} planes, as well as slip in the [100] direction. Dislocation density, even in recrystallized grains, is very high (likely >1014 m−2), reflecting the final high stresses in the samples during deformation. The results provide greater constraints on the regimes of various deformation mechanisms in wadsleyite at various experimental conditions.

Plastic anisotropy and slip systems in ringwoodite deformed to high shear strain in the Rotational Drickamer Apparatus

High shear strain deformation experiments up to equivalent strains of 180% were performed on ringwoodite at conditions of 23GPa and 1800K. At very large shear strains, deviation in the strengths of the (311) and (400) lattice planes is observed, indicating plastic anisotropy. Lattice strain theory was applied to calculate effective viscosities of the available slip systems from the observed plastic anisotropy. We find that the effective viscosities (unitless) are proportional to 0.43, 0.46, and 1.54 for the {111}〈11¯0〉, {11¯0}〈110〉 and {001}〈11¯0〉 slip systems respectively. This indicates that {111}〈11¯0〉 slip is slightly softer than {11¯0}〈11¯0〉 at these conditions. Additionally the {111}〈11¯0〉 slip system has significantly more symmetric variants than the slip systems involving other lattice planes, thus it is expected to dominate deformation. This is confirmed by polycrystal plasticity modeling using the viscoplastic self-consistent code (VPSC) which indicates that simulations with dominant {111}〈11¯0〉 slip provide the best match to experimental textures.

Plastic deformation experiments to high strain on mantle transition zone minerals wadsleyite and ringwoodite in the rotational Drickamer apparatus

We report the results of plastic deformation experiments on polycrystalline wadsleyite and ringwoodite performed at 15–23GPa and 1300–2100K conducted using the rotational Drickamer apparatus (RDA). Wadsleyite was synthesized from fine-grained (∼2μm) San Carlos olivine in a Kawai-type multianvil apparatus; the average grain size of the resulting wadsleyite was 1.2μm. The initial water content of the undeformed wadsleyite was 24,000–26,000H/106 Si but the final water content is variable and less than the initial water content. Ringwoodite was synthesized from wadsleyite in situ in the RDA. Both strain and stress were measured in situ using a synchrotron x-ray facility. Determinations of strains and strain rates were made from x-ray radiographs of the sample, using a Mo foil strain marker in the sample assembly. The state of stress was determined from the observed d-spacing of multiple lattice planes as a function of azimuth angle. Samples were deformed at various strain rates at around 10−4–10−5s−1. Deformation mechanisms were inferred from the stress exponent and the microstructures. We determined the stress exponent n for wadsleyite to be 6±3, suggesting dislocation creep was the dominant deformation mechanism in wadsleyite. At grain sizes of ∼1μm, our samples were still deforming primarily by dislocation creep. However, small dislocation-free grains are also observed suggesting that diffusion creep may operate in some parts of our samples.

Shear deformation of polycrystalline wadsleyite up to 2100 K at 14–17 GPa using a rotational Drickamer apparatus (RDA)

Shear deformation experiments on polycrystalline wadsleyite (water content, ∼200–2200 H/106 Si) have been conducted at 14.4–17.0 GPa, 1690–2100 K, and strain rates of 2.6–16 × 10−5 s−1 using a rotational Drickamer apparatus (RDA) at a synchrotron facility. The stress was measured from the orientation dependence of lattice spacing for the (013), (211), (141), (240) and (244) planes. On the basis of the mechanical and microstructural observations, we infer that deformation occurs by exponential creep through the Peierls mechanism at relatively low temperatures of 1690–2030 K. However, a sample deformed at the temperature of 2100 K showed significant grain‐size reduction, and most of small grains are dislocation‐free, although sub‐boundaries were observed in some grains in the sample. We interpret these observations as evidence for dynamic recrystallization and that diffusion creep (and grain boundary sliding) plays an important role after dynamic recrystallization caused by power law creep. Consequently, the strength observed in the high‐temperature conditions determined by the present study provides an important constraint on strength of diffusion creep and a lower limit for that of the power law dislocation creep. We conclude that the strength of wadsleyite in the power law dislocation creep is higher than or comparable to that of olivine and the strength of wadsleyite in the Peierls regime is similar to that of olivine.

In siturheological measurements at extreme pressure and temperature using synchrotron X-ray diffraction and radiography

Dramatic technical progress seen over the past decade now allows the plastic properties of materials to be investigated under extreme pressure and temperature conditions. Coupling of high-pressure apparatuses with synchrotron radiation significantly improves the quantification of differential stress and specimen textures from X-ray diffraction data, as well as specimen strains and strain rates by radiography. This contribution briefly reviews the recent developments in the field and describes state-of-the-art extreme-pressure deformation devices and analytical techniques available today. The focus here is on apparatuses promoting deformation at pressures largely in excess of 3 GPa, namely the diamond anvil cell, the deformation-DIA apparatus and the rotational Drickamer apparatus, as well as on the methods used to carry out controlled deformation experiments while quantifying X-ray data in terms of materials rheological parameters. It is shown that these new techniques open the new field of in situ investigation of materials rheology at extreme conditions, which already finds multiple fundamental applications in the understanding of the dynamics of Earth-like planet interior.

Shear deformation of dry polycrystalline olivine under deep upper mantle conditions using a rotational Drickamer apparatus (RDA)

Shear deformation experiments on dry hot-pressed polycrystalline San Carlos olivine have been conducted at 4.9–9.6 GPa, 1300–1870 K and strain rates of 0.6–7.4 × 10 −5 s −1 using a rotational Drickamer apparatus (RDA) at a synchrotron facility. The stress was measured from the orientational dependence of lattice spacing for the (1 3 0), (1 3 1), (1 1 2), (1 2 2), (1 4 0) and (2 4 1) planes, as well as from the dislocation densities. Based on the mechanical and microstructural observations, we infer that deformation occurs by power-law creep involving dislocation glide and climb under high temperature conditions, whereas deformation is due to exponential creep through the Peierls mechanism at relatively low temperatures. In both regimes the strength of olivine at steady-state deformation at these pressures is much larger than those at lower pressures. The activation volumes V* is estimated to be ∼15–20 × 10 −6 m 3/mol for the power-law creep. Combined with the previous results under wet conditions, we present the recommended values of flow law parameters on olivine for power-law creep constrained by high-pressure deformation experiments.

Plastic deformation of wadsleyite and olivine at high-pressure and high-temperature using a rotational Drickamer apparatus (RDA)

Large-strain plastic deformation experiments of wadsleyite and olivine were conducted using a rotational Drickamer apparatus (RDA) up to pressure and temperature conditions corresponding to the Earth's mantle transition zone. Sintered ring-shaped (Mg,Fe) 2SiO 4 wadsleyite and olivine samples were deformed at P ∼ 16 GPa and T = 1600 and 1800 K, and P ∼ 11 GPa and T = 1800 K, respectively, with equivalent strain rate of ε ˙ E ∼ 6 × 10 − 5 s − 1 . In situ observations of deforming samples were carried out using the synchrotron radiation facility at Brookhaven National Laboratory, NSLS, X17B2. Stress was measured by X-ray diffraction at six different angles with respect to the compression axis. The stress estimated by X-ray diffraction was in good agreement with the stress estimated from dislocation density (for olivine). Strain was determined using X-ray radiographs of a strain marker (Re or Mo foil). Deformation of samples with a RDA involves both uniaxial compression and simple shear. A new formulation is developed to analyze both components to determine the rheological properties of a sample. Stress–strain curves show strain-hardening up to the equivalent strain of ɛ E ∼ 0.2 followed by the quasi-steady state deformation. Wadsleyite is found to be stronger than olivine compared at similar conditions and the creep strength of olivine at P ∼ 11 GPa is much higher than those at lower pressures.

高温高圧下の変形実験の最新技術

In this article, recent technical developments in high-pressure deformation experiments especially in the field of Earth science are reviewed. The diamond anvil cell has an advantage in performing deformation experiments at very high pressures (up to 160 GPa) compared to other large-volume apparatuses. However, diamond anvil cell has severe limitation in quantitative strain measurements, deformation at high temperatures and deformation with large strain. On the other hand, quantitative rheological measurements at relatively high pressures (up to 10-20 GPa) and high temperatures (up to 1000-2000 K) are possible by using recently developed large-volume deformation apparatuses, rotational Drickamer apparatus, deformation-DIA and “big D-DIA”. Synchrotron X-ray is a powerful tool for in-situ strain and stress measurements in high-pressure deformation experiments using these apparatuses.

高温高圧鉱物物性 Ｄｒｃｋａｍｅｒ型高圧装置を用いたＸ線その場観察とその地球物理学への応用

In situ X-ray observation using Drickamer type high pressure apparatus and its application to geophysics are discussed in detail. At first, characteristics of Drickamer apparatus are introduced by comparing with diamond anvil cell and multi anvil apparatus. Then, two topics are discussed as its applications to geophysical problems: One is the mechanism of deep-focus earthquakes and the other is the phase relation of iron which thought to be dominant component of the Earth's inner core. Nature of deep-focus earthquakes has been enigmatic. Two models describing the mechanism of deep earthquakes are proposed recently based on high pressure experiments and seismological measurements of the structure of subduction zone. These two models, frictional instability caused by pore water pressure and transformational faulting, are briefly introduced, and discussed in relation to differential stress measured by the Drickamer apparatus. Recently, the existence of two new phases of iron is proposed. One is a high temperature phase with dhcp structure, which appears at pressures of above 30GPa. The other is a very high pressure and temperature phase above 200GPa and 4000K with bcc structure which is proposed theoretically. Whether the former new phases exist or not is discussed together with X-ray and electrical resistance data obtained by the Drickamer apparatus.

Studies of intermolecular interactions in transition metal complexes—VI[1]: The electrical properties of some quasi-one dimensional mixed valence complexes at ultra-high pressures

Electrical conductivity and conductivity activation energy measurements were carried out on the quasi-one dimensional (1-D) mixed valence complexes, Pd(NH 3) 2Br 3 and Au(DBS)X 2 (DBS = dibenzylsulfide, X = Cl, Br), at pressures up to 360 Kbar using a diamond compact-tipped Drickamer apparatus. The results indicate an enormous enhancement of the conductivity with values approaching 5 Ω −1 cm −1 for the palladium complex and 2 × 10 −3 Ω −1 cm −1 for Au(DBS)Br 2 in the range 100–250 Kbar pressure. The increase in conductivity and decrease in the activation energy is attributed to compression along the 1-D chains, leading to more nearly equivalent coordination environments for the intrachain metal atoms. A maximum in the conductivity and a minimum in the activation energy is observed for these complexes, indicating that the pressure induced reduction in metal site inequivalency reaches a limit and that conversion to the hypothetical uniform-valence (Pd(III) or Au(II)), 1-D metallic state is not attained at high pressures. These observations are discussed in the context of the interatomic distances changes anticipated at high pressure.