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Schematics of the PEP setup at HPCAT 16BM-B. (a) White X-ray energy dispersive X-ray diffraction setup; (b) collimation depth defined by slit geometry (D 0. collimation depth at the beam center; D 1. collimation depth elongated due to the practical beam width; modified from Kono et al., 2014b).
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We review recent progress in studying silicate, carbonate, and metallic liquids of geological and geophysical importance at high pressure and temperature, using the large-volume high-pressure devices at the third-generation synchrotron facility of the Advanced Photon Source, Argonne National Laboratory. These integrated high-pressure facilities now...
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The effect of TiO2 and P2O5 on the ferric/ferrous ratio in silicate melts was investigated in model silicate melts at air conditions in the temperature range 1,400-1,550 degrees C at 1-atm total pressure. The base composition of the anorthite-diopside eutectic composition was modified with 10 wt % Fe2O3 and variable amounts of TiO2 (up to 30 wt %)...
Citations
... High pressure studies of carbonate glass were performed with energy dispersive diffraction at beamline 16BMB (HPCAT) at the Advanced Photon Source (APS). The configuration at this beamline enables the specially developed double-stage large volume (Paris-Edinburgh type) press to be integrated 11,28,[44][45][46] . The total X-ray structure factor, S(Q), for each pressure point was obtained using the multi-angle energy dispersive technique 28,47 (see SI Fig. S1) with spline-smoothed curves produced by correcting the data from each detector bank and normalising to the white X-ray beam 28,47 . ...
Carbonate liquids are an important class of molten salts, not just for industrial applications, but also in geological processes. Carbonates are generally expected to be simple liquids, in terms of ionic interactions between the molecular carbonate anions and metal cations, and therefore relatively structureless compared to more “polymerized” silicate melts. But there is increasing evidence from phase relations, metal solubility, glass spectroscopy and simulations to suggest the emergence of carbonate “networks” at length scales longer than the component molecular anions. The stability of these emergent structures are known to be sensitive to temperature, but are also predicted to be favoured by pressure. This is important as a recent study suggests that subducted surface carbonate may melt near the Earth’s transition zone (~44 km), representing a barrier to the deep carbon cycle depending on the buoyancy and viscosity of these liquids. In this study we demonstrate a major advance in our understanding of carbonate liquids by combining simulations and high pressure measurements on a carbonate glass, (K2CO3-MgCO3) to pressures in excess of 40 GPa, far higher than any previous in situ study. We show the clear formation of extended low-dimensional carbonate networks of close CO3²⁻ pairs and the emergence of a “three plus one” local coordination environment, producing an unexpected increase in viscosity with pressure. Although carbonate melts may still be buoyant in the lower mantle, an increased viscosity by at least three orders of magnitude will restrict the upward mobility, possibly resulting in entrainment by the down-going slab.
... amorphous boron oxide | extreme compression | megabar pressures | inelastic X-ray scattering W hen under extreme compression, amorphous oxides undergo structural transitions into more densely packed glassy networks that are significantly different from those at ambient pressure (e.g., refs. [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16]. The detailed structures of the glasses at high pressure are among the remaining fundamental mysteries in modern physical sciences. ...
Significance
When compressed above megabar pressures (100 GPa), glasses may undergo structural transitions into more densely packed networks that differ from those at ambient pressure. While inelastic X-ray scattering (IXS) provides a rare opportunity to probe the pressure-induced bonding transitions, a decade of efforts to collect an IXS signal from any matters beyond 100 GPa have not been successful. Here, IXS spectra for B 2 O 3 glasses up to ∼120 GPa revealed its unique densification paths characterized with the unexpected stability of four-coordinated boron ( [4] B). This is in contrast to other prototypical glasses where highly coordinated cations ( [4,5,6] Si and [4,5,6] Ge) form at much lower pressure, confirming that the cation with a smaller atomic radius undergoes coordination transformation at higher pressure.
... The mantle transition zone is a special and important mineral zone in the mantle (e.g. Weidner and Wang, 2000;Wang and Shen, 2014), with three important seismic discontinuities: (1) at 410-km discontinuity, olivine ( phase) transits into wadsleyite ( phase); (2) at 520-km discontinuity, wadsleyite transits into ringwoodite ( phase); (3) at the 660-km discontinuity, ringwoodite break down to bridgmanite Figure 1 The compositions of hydrous silicate minerals in the peridotite system (MgO-SiO 2 -Mg(OH) 2 ), taken from Ye et al. (2015) (Mg, Fe)O), which is also known as the post-spinel phase transition, and 660-km discontinuity also serves as the boundary between the upper mantle and lower mantle. Hence, wadsleyite and ringwoodite, as the high-pressure polymorphs of olivine, play important roles in the physics and chemistry of the MTZ and the storage of water in planetary interiors. ...
There are potentially huge amounts of water stored in Earth’s mantle, and the water solubilities in the silicate minerals range from tens to thousands of part per minion (ppm, part per million). Exploring water in the mantle has attracted much attention from the societies of mineralogy and geophysics in recent years. In the subducting slab, serpentine breaks down at high temperature, generating a series of dense hydrous magnesium silicate (DHMS) phases, such as phase A, chondrodite, clinohumite, etc. These phases may serve as carriers of water as hydroxyl into the upper mantle and the mantle transition zone (MTZ). On the other hand, wadsleyite and ringwoodite, polymorphs of olivine, are most the abundant minerals in the MTZ, and able to absorb significant amount of water (up to about 3 wt.% H2O). Hence, the MTZ becomes a very important layer for water storage in the mantle, and hydration plays important roles in physics and chemistry of the MTZ. In this paper, we will discuss two aspects of hydrous silicate minerals: (1) crystal structures and (2) equations of state (EoSs).
High pressure mineral physics is a field that has shaped our understanding of deep planetary interiors and revealed new material phenomena occurring at extreme conditions. Comprised of sixteen chapters written by well-established experts, this book covers recent advances in static and dynamic compression techniques and enhanced diagnostic capabilities, including synchrotron X-ray and neutron diffraction, spectroscopic measurements, in situ X-ray diffraction under dynamic loading, and multigrain crystallography at megabar pressures. Applications range from measuring equations of state, elasticity, and deformation of materials at high pressure, to high pressure synthesis, thermochemistry of high pressure phases, and new molecular compounds and superconductivity under extreme conditions. This book also introduces experimental geochemistry in the laser-heated diamond-anvil cell enabled by the focused ion beam technique for sample recovery and quantitative chemical analysis at submicron scale. Each chapter ends with an insightful perspective of future directions, making it an invaluable source for graduate students and researchers.
Silicate melts are very active in the interior of the Earth and other terrestrial planets, and are important carriers for the transport of material and energy. The determination of the equation of state (EOS) for silicate melts and the acquisition of a precise quantitative relationship between molar volume (or density) and temperature, pressure, and composition is essential for simulating the generation, migration, and eruption processes of magmas and the evolution of the magma ocean stage during the early formation of the Earth and other terrestrial planets, for calculating and modeling the phase equilibria involving silicate melts, and for revealing the variation of the microstructure of silicate melts with pressure. However, it is experimentally challenging to determine the volumetric properties of silicate melts and the accumulated density data at high pressure are still very limited due to a series of problems such as: the high liquidus temperature of silicate rocks; proneness for silicate melts to react with sample capsules to change the melt composition; and proneness for melts to flow and leak during the high pressure and high temperature experiments. In recent years, there is rapid progress in the high pressure and high temperature experimental techniques, in terms of not only the extension of temperature and pressure ranges but also the improvement on the accuracy of measurements, and the emergence of new methods for in-situ measurements. Here, we review the widely-used theoretical models of ambient-pressure and high-pressure EOS for silicate melts, and illustrate some problems that need to be solved urgently: (1) the room pressure EOS for iron- and titanium-bearing silicate melts needs to be improved; (2) the partial molar properties of the H2O and CO2 components in silicate melts containing volatile components may vary markedly with the melt composition, which need to be addressed in high-pressure EOS; (3) how the formulation and applicable range of EOS correspond to changes in melt structure and compression mechanism requires further study. We highlight the basic principle and applicable range of various methods for determining the EOS for silicate melts, and compare the advantages and disadvantages of doublebob Archimedes method, fusion curve analysis, shock compression experiments, sink-float method, X-ray absorption, X-ray diffraction and ultrasonic interferometry. Future trends in this field are to develop experimental techniques for in situ measurements on melt density or sound velocity at high temperature and high pressure and to accumulate more experimental data, and on the other hand, to improve the theoretical models of the EOS for silicate melts by a combination of research on the microstructure and compression mechanisms of silicate melts.
A theoretical effective thermal conductivity model for nanofluids is derived based on fractal distribution characteristics of nanoparticle aggregation. Considering two different mechanisms of heat conduction including particle aggregation and convention, the model is expressed as a function of the fractal dimension and concentration. In the model, the change of fractal dimension is related to the variation of aggregation shape. The theoretical computations of the developed model provide a good agreement with the experimental results, which may serve as an effective approach for quantitatively estimating the effective thermal conductivity of nanofluids.
