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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 379 records · Page 21
All sourcesNASA NTRSDOE OSTI
DOE OSTI2015

Dry (Mg,Fe)SiO 3 perovskite in the Earth's lower mantle

Combined synthesis experiments and first-principles calculations show that MgSiO 3 -perovskite with minor Al or Fe does not incorporate significant OH under lower mantle conditions. Perovskite, stishovite, and residual melt were synthesized from natural Bamble enstatite samples (Mg/(Fe+Mg) = 0.89 and 0.93; Al 2 O 3 < 0.1 wt% with 35 and 2065 ppm wt H 2 O, respectively) in the laser-heated diamond anvil cell at 1600-2000 K and 25-65 GPa. Combined Fourier transform infrared (FTIR) spectroscopy, x-ray diffraction, and ex-situ transmission electron microscopy (TEM) analysis demonstrates little difference in the resulting perovskite as a function of initial water content. Four distinct OH vibrational stretching bands are evident upon cooling below 100 K (3576, 3378, 3274, and 3078 cm -1 ), suggesting 4 potential bonding sites for OH in perovskite with a maximum water content of 220 ppm wt H 2 O, and likely no more than 10 ppm wt H 2 O. Complementary, Fe-free, first-principles calculations predict multiple potential bonding sites for hydrogen in perovskite, each with significant solution enthalpy (0.2 eV/defect). We calculate that perovskite can dissolve less than 37 ppm wt H 2 O (400 ppm H/Si) at the top of the lower mantle, decreasing to 31 ppm wt H 2 O (340 ppm H/Si) at 125 GPa and 3000 K in the absence of a melt or fluid phase. Here, we propose that these results resolve a long-standing debate of the perovskite melting curve and explain the order of magnitude increase in viscosity from upper to lower mantle.

58 GEOSCIENCES↗
DOE OSTI2016

Anomalous density and elastic properties of basalt at high pressure: Reevaluating of the effect of melt fraction on seismic velocity in the Earth's crust and upper mantle

Independent measurements of the volumetric and elastic properties of Columbia River basalt glass were made up to 5.5 GPa by high-pressure X-ray microtomography and GHz-ultrasonic interferometry, respectively. The Columbia River basalt displays P and S wave velocity minima at 4.5 and 5 GPa, respectively, violating Birch’s law. These data constrain the pressure dependence of the density and elastic moduli at high pressure, which cannot be modeled through usual equations of state nor determined by stepwise integrating the bulk sound velocity as is common practice. We propose a systematic variation in compression behavior of silicate glasses that is dependent on the degree of polymerization and arises from the flexibility of the aluminosilicate network. Likewise, this behavior likely persists into the liquid state for basaltic melts resulting in weak pressure dependence for P wave velocities perhaps to depths of the transition zone. By modeling the effect of partial melt on P wave velocity reductions it is suggested that melt fraction determined by seismic velocity variations may be significantly overestimated in the crust and upper mantle.

58 GEOSCIENCES↗
DOE OSTI2013

Earth System Grid Federation: Federated and Integrated Climate Data from Multiple Sources. IN: Earth System Modeling, Volume 6

In climate science, the quantity of data in use by 2020 is expected to be in the hundreds of exabytes (EB, where 1 exabyte = 1018 bytes). Current and future heterogeneous climate data will be distributed around the globe and must be harnessed to find solutions to mission-critical problems. Additionally, more requirements and more constraints are needed to expand and integrate new modeling capabilities and tasks, such as climate prediction, uncertainty quantification (UQ) of model performance, test-bed development, and assimilation of more diverse data sets. These data exploration tasks can be complex and time-consuming, and frequently involve numerous resources spread throughout the modeling and observational climate communities. Staff expertise and core competencies must therefore be flexibly applied to multiple projects and programs to accommodate more complex applications and state-of-the-art science analysis, while allowing resources to be adapted to address future areas of interest in climate research.

Climate Project↗