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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 163 records · Page 9
All sourcesNASA NTRSDOE OSTI
NASA NTRS1984

Experimental determination of the partitioning of gallium between solid iron metal and synthetic basaltic melt Electron and ion microprobe study

The distribution of Ga between solid Fe metal and synthetic basaltic melt is investigated experimentally at temperatures of 1190 and 1330 C, and over a narrow range of oxygen fugacities. Metal-silicate reversal experiments were conducted, indicating a close approach to equilibrium. The analysis of the partitioned products was performed using electron and ion microprobes. At one bar total pressure, the solid metal/silicate melt partition coefficient D(Ga) is used to evaluate metal-silicate fractionation processes in the earth, moon, and Eucrite Parent Body (EPB). It is found that the depletion of Ga abundances in the EPB is due to the extraction of Ga into a metallic core. Likewise, the depletion of Ga in the lunar mantle is consistent with the extraction of Ga into a smaller lunar core if Ga was originally present in a subchondritic concentration. The relatively high Ga abundances in the earth's mantle are discussed, with reference to several theoretical models.

Drake, M. J.↗
NASA NTRS1992

Thermal and dynamical regimes of single- and two-phase magmatic flow in dikes

The coupling between thermal and dynamical regimes of single- and two-phase magmatic flow in dikes, due to temperature-dependent viscosity and dissipation, was investigated using finite element calculations of magma flow in dikelike channels with length-to-width ratios of 1000:1 or more. Solutions of the steady state equations governing magma flow are obtained for a variety of conditions ranging from idealized plane-parallel models to cases involving nonparallel geometry and two-phase flows. The implications of the numerical simulations for the dynamics of flow in a dike-reservoir system and the consequences of dike entrance conditions on magmatic storage are discussed. Consideration is also given to an unmixing/self-lubrication mechanism which may be important for the lubrication of silicic magmas rising to the earth's surface in mixed magma ascent scenarios, which naturally segregates magma mixtures of two components with differing viscosities to minimize the driving pressure gradient.

Carrigan, Charles R.↗
NASA NTRS1994

Cosmic acceleration of Earth and the Moon by dark matter

In order to test the hypothesis that the gravitational interaction between our Galaxy's dark matter and the ordinary matter in Earth and the Moon might not fulfill the equivalence principle (universality of free fall), we consider the pertinent perturbation of the lunar orbit -- a sidereal month period range oscillation resulting from a spatially fixed polarization of the orbit. Lunar laser ranging (LLR) data can measure this sidereal perturbation to an accuracy equal to or better than its existing measurement of the synodic month period range oscillation amplitude (+/- 3 cm) which has been used for testing whether Earth and the Moon accelerate at equal rates toward the Sun. Because of the slow precession rate of the Moon's perigree (8.9 yr period), the lunar orbit is particularly sensitive to a cosmic acceleration; the LLR fit of the orbit places an upper limit of 10(exp -13) cm/sq. s for any cosmic differential acceleration between Earth (Fe) and the Moon (silicates). This is 10(exp -5) of the total galactic acceleration of the solar system, of which, it has been suggested, a large portion is produced by dark matter.

Nordtvedt, Kenneth L.↗
NASA NTRS2011

HyTES: Thermal Imaging Spectrometer Development

The Jet Propulsion Laboratory has developed the Hyperspectral Thermal Emission Spectrometer (HyTES). It is an airborne pushbroom imaging spectrometer based on the Dyson optical configuration. First low altitude test flights are scheduled for later this year. HyTES uses a compact 7.5-12 micrometer m hyperspectral grating spectrometer in combination with a Quantum Well Infrared Photodetector (QWIP) and grating based spectrometer. The Dyson design allows for a very compact and optically fast system (F/1.6). Cooling requirements are minimized due to the single monolithic prism-like grating design. The configuration has the potential to be the optimal science-grade imaging spectroscopy solution for high altitude, lighter-than-air (HAA, LTA) vehicles and unmanned aerial vehicles (UAV) due to its small form factor and relatively low power requirements. The QWIP sensor allows for optimum spatial and spectral uniformity and provides adequate responsivity which allows for near 100mK noise equivalent temperature difference (NEDT) operation across the LWIR passband. The QWIP's repeatability and uniformity will be helpful for data integrity since currently an onboard calibrator is not planned. A calibration will be done before and after eight hour flights to gage any inconsistencies. This has been demonstrated with lab testing. Further test results show adequate NEDT, linearity as well as applicable earth science emissivity target results (Silicates, water) measured in direct sunlight.

remote sensing↗
NASA NTRS2002

Constraining the Material that Formed the Moon: The Origin of Lunar V, CR, and MN Depletions

The mantles of the Earth and Moon are similarly depleted in V, Cr, and Mn relative to chondritic values. Core formation deep within the Earth was suggested by as the origin of the depletions. Following Earth's core formation, the Moon was proposed to have inherited its mantle from the depleted mantle of the Earth by a giant impact event. This theory implied the Moon was primarily composed of material from the Earth's mantle. Recent systematic metal-silicate experiments of V, Cr, and Mn evaluated the behavior of these elements during different core formation scenarios. The study found that the V, Cr, and Mn depletions in the Earth could indeed be explained by core formation. The conditions of core formation necessary to deplete V, Cr, and Mn in the Earth's mantle were consistent with the deep magma ocean proposed to account for the Earth's mantle abundances of Ni and Co. Using the parameterizations of for the metal-silicate partition coefficients (D) of V, Cr, and Mn, we investigate here the conditions needed to match the depletions in the silicate Moon and determine if such conditions could have been present on the giant impactor.

Chabot, N. L.↗
NASA NTRS1992

Pressure-induced coordination changes in alkali-germanate melts - An in situ spectroscopic investigation

The structure of liquid Na2Ge2O5-H2O, a silicate melt analog, has been studied with Raman spectroscopy to pressures of 2.2 gigapascals. Upon compression, a peak near more than 240 wavenumbers associated with octahedral GeO6 groups grows relative to a peak near 500 wavenumbers associated with tetrahedral GeO4 groups. This change corresponds to an increase in octahedral germanium in the liquid from near 0 percent at ambient pressures to more than 50 percent at a pressure of 2.2 gigapascals. Silicate liquids pausibly undergo similar coordination changes at depth in the earth. Such structural changes may generate decreases in the fusion slopes of silicates at high pressures as well as neutrally buoyant magmas within the transition zone of the earth's mantle.

Farber, Danial L.↗
DOE OSTI2026

High Entropy Rare-earth Oxide (HERO) Coatings for Refractory Alloys

The HERO coating was developed to protect refractory alloys for application in the harsh hot section of the turbine engine environment addressing ARPA-E ULTIMATE Project Topic 2: Coating Development. The effort was both innovative in its utilization of high entropy rare earth oxides as well as transformational in our approach: holistic design of a single layer thermal/environmental barrier coating (T/EBC) for refractory alloys, with an excellent coefficient of thermal expansion (CTE) match to the alloy substrate, chemical compatibility with the underlying alloy, low oxidant permeability, stability in combustion environments, low thermal conductivity, thermal shock resistance, and resistance to degradation by siliceous debris (calcium magnesium alumino-silicates-CMAS). The high entropy rare earth oxide approach enables two critical coating properties: tailoring CTE match to the substrate and, most significantly, substantially reduced thermal conductivity. The summation of these proposed coating capabilities goes well beyond the technical requirements specified in the ULTIMATE program objectives, and additionally is essential for a successful first stage turbine blade application.

36 MATERIALS SCIENCE↗
NASA NTRS2018

Core-Mantle Fractionation of Carbon in Earth and Mars: the Effects of Sulfur

Constraining carbon (C) fractionation between silicate magma ocean (MO) and core-forming alloy liquid during early differentiation is essential to understand the origin and early distribution of C between reservoirs such as the crust-atmosphere, mantle, and core of Earth and other terrestrial planets. Yet experimental data at high pressure (P)-temperature (T) on the effect of other light elements such as sulfur (S) in alloy liquid on alloy-silicate partitioning of C and C solubility in Fe-alloy compositions relevant for core formation is lacking. Here we have performed multi-anvil experiments at 6–13 GPa and 1800–2000 °C to examine the effects of S and Ni on the solubility limit of C in Fe-rich alloy liquid as well as partitioning behavior of C between alloy liquid and silicate melt (𝐷𝐷(sub C)(sup alloy/silicate)). The results show that C solubility in the alloy liquid as well as 𝐷𝐷(sub C)(sup alloy/silicate) decreases with increasing in S content in the alloy liquid. Empirical regression on C solubility in alloy liquid using our new experimental data and previous experiments demonstrates that C solubility significantly increases with increasing temperature, whereas unlike in S-poor or S-free alloy compositions, there is no discernible effect of Ni on C solubility in S-rich alloy liquid. Our modelling results confirm previous findings that in order to satisfy the C budget of BSE, the bulk Earth C undergoing alloy-silicate fractionation needs to be as high as those of CI-type carbonaceous chondrite, i.e., not leaving any room for volatility-induced loss of carbon during accretion. For Mars, on the other hand, an average single-stage core formation at relatively oxidized conditions (1.0 log unit below IW buffer) with 10-16 wt.% S in the core could yield a Martian mantle with a C budget similar to that of Earth’s BSE for a bulk C content of ~0.25-0.9 wt.%. For the scenario where C was delivered to the proto-Earth by a S-rich differentiated impactor at a later stage, our model calculations predict that bulk C content in the impactor can be as low as ~0.5 wt.% for an impactor mass that lies between 9-20% of present day Earth’s mass. This value is much higher than 0.05-0.1 wt.% bulk C in the impactor predicted by Li et al. (2016) because C-solubility limit of 0.3 wt.% in a S-rich alloy predicted by their models is significantly lower than the experimentally derived C-solubility of ~1.6 wt. % for the relevant S-content in the core of the impactor.

Carbon↗
DOE OSTI2020

High-Pressure Sound Velocity Measurements of Liquids Using In Situ Ultrasonic Techniques in a Multianvil Apparatus

Sound velocity and equation of state of liquids provide important constraints on the generation, presence, and transport of silicate and metallic melts in the Earth’s interior. Unlike their solid counterparts, these properties of liquids pose great technical challenges to high-pressure measurements and are poorly constrained. Here we present the technical developments that have been made at the GSECARS beamline 13-ID-D of the Advanced Photon Source for the past several years for determination of sound velocity of liquids using the ultrasonic techniques in a 1000-ton Kawai-type multianvil apparatus. Temperature of the sound velocity measurements has been extended to ~2400 K at 4 GPa and ~2000 K at 8 GPa to enable studies of liquids with very high melting temperatures, such as the silicate liquids.

58 GEOSCIENCES↗
DOE OSTI2020

Structural evolution of two-dimensional silicates using a “bond-switching” algorithm

Silicates are the most abundant materials in the earth's crust. In recent years, two-dimensional (2D) versions of them grown on metal supports (known as bilayer silicates) have allowed their study in detail down to the atomic scale. These structures are self-containing. Furthermore, they are not covalently bound to the metal support but interact with it through van der Waals forces. Like their three-dimensional counterparts, the 2D-silicates can form both crystalline and vitreous structures. Furthermore, the interconversion between vitreous to crystalline structures has been experimentally observed at the nanoscale. While theoretical work has been carried out to try to understand these transformations, a limitation for ab initio methods, and even molecular dynamics methods, is the computational cost of studying large systems and long timescales. In this work, we present a simple and computationally inexpensive approach, that can be used to represent the evolution of bilayer silicates using a bond-switching algorithm. This approach allows reaching equilibrium ring size distributions as a function of a parameter that can be related to the ratio between temperature and the energy required for the bond-switching event. The ring size distributions are compared to experimental data available in the literature.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2022

Synthesis and Stability of an Eight‐Coordinated Fe 3 O 4 High‐Pressure Phase: Implications for the Mantle Structure of Super‐Earths

Abstract Super‐Earths ranging up to 10 Earth masses (M E ) with Earth‐like density are common among the observed exoplanets thus far, but their measured masses and radii do not uniquely elucidate their internal structure. Exploring the phase transitions in the Mg‐silicates that define the mantle‐structure of super‐Earths is critical to characterizing their interiors, yet the relevant terapascal conditions are experimentally challenging for direct structural analysis. Here we investigated the crystal chemistry of Fe 3 O 4 as a low‐pressure analog to Mg 2 SiO 4 between 45–115 GPa and up to 3000 K using powder and single crystal X‐ray diffraction in the laser‐heated diamond anvil cell. Between 60–115 GPa and above 2000 K, Fe 3 O 4 adopts an 8‐fold coordinated Th 3 P 4 ‐type structure ( I ‐43d, Z = 4) with disordered Fe 2+ and Fe 3+ into one metal site. This Fe‐oxide phase is isostructural with that predicted for Mg 2 SiO 4 above 500 GPa in super‐Earth mantles and suggests that Mg 2 SiO 4 can incorporate both ferric and ferrous iron at these conditions. The pressure‐volume behavior observed in this 8‐fold coordinated Fe 3 O 4 indicates a maximum 4% density increase across the 6‐ to 8‐fold coordination transition in the analog Mg‐silicate. Reassessment of the FeO—Fe 3 O 4 fugacity buffer considering the Fe 3 O 4 phase relationships identified in this study reveals that increasing pressure and temperature to 120 GPa and 3000 K in Earth and planetary mantles drives iron toward oxidation.

Zurkowski, C. C.↗
DOE OSTI2020

Thermal and magnetic evolution of a crystallizing basal magma ocean in Earth's mantle

We present the thermochemical evolution of a downward crystallizing basal magma ocean (BMO) overlying the liquid outer core and probe its capability to dissipate enough power to generate and sustain an early dynamo. Furthermore, a total of 61 out of 112 scenarios for a BMO with imposed, present-day heat flux, Q BMO , values of 15, 18, and 21 TW and radiogenic heat, Q r , values of 4, 8, and 12 TW fully crystallized during the age of the Earth. Most of these models are energetically capable of inducing magnetic activity for the first 1.5 Gyrs, at least, with durations extending to 2.5 Gyrs; with final core-mantle boundary (CMB) temperatures of 4400 ±500 K-well within current best estimates for inferred temperatures. None of the models with Q BMO = 12 TW achieved a fully crystallized state, which may reflect a lower bound on the present-day heat flux across the CMB. BMO-powered dynamos exhibit strong dependence on the partition coefficient of iron into the liquid layer and its associated melting-point depression for a lower mantle composition at near-CMB conditions-parameters which are poorly constrained to date. Nonetheless, we show that a crystallizing BMO is a plausible mechanism to sustain an early magnetic field.

58 GEOSCIENCES↗
NASA NTRS1994

The evolution of enstatite and chondrules in unequilibrated enstatite chondrites: Evidence from iron-rich pyroxene

FeO-rich (Fs(sub 6)-34) pyroxene lacking cathodoluminescence (CL), hereafter black pyroxene, is a major constituent of some of the chondrules and fragments in unequilibrated (type 3) enstatite chondrites (UECs). It contains structurally oriented zones of Cr-, Mn-, V-rich, FeO-poor enstatite with red CL, associated with mm-sized blebs of low-Ni, Fe-metal and, in some cases, silica. These occurrences represent clear evidence of pyroxene reduction. The black pyroxene is nearly always rimmed by minor element (Cr, Mn, V)-poor enstatite having a blue CL. More commonly, red and blue enstatites, unassociated with black pyroxene, occur as larger grains in chondrules and fragments, and these constitute the major silicate phases in UECs. The rare earth element (REE) abundance patterns of the black pyroxene are LREE-depleted. The blue enstatite rims, however, have a near-flat to LREE-enriched pattern, approx. 0.5-4x chondritic. The petrologic and trace element data indicate that the black pyroxene is from an earlier generation of chondrules that formed in a nebular region that was more oxidizing than that of the enstatite chondrites. Following solidification, these chondrules experienced a more reducing nebular environment and underwent reduction. Some, perhaps most, of the red enstatite that is common throughout the UECs may be the product of solid-state reduction of black pyroxene. The blue enstatite rims grew onto the surfaces of the black pyroxene and red enstatite as a result of condensation from a nebular gas. The evolutionary history of some of the enstatite and chondrules in enstatite chondrites can be expressed in a four-stage model that includes: Stage 1. Formation of chondrules in an oxidizing nebular environment. Stage 2. Solid-state reduction of the more oxidized chondrules and fragments to red enstatite in a more reducing nebular environment. Stage 3. Formation of blue enstatite rims on the black pyroxene as well as on the red enstatite. Stage 4. Reprocessing, by various degrees of melting, of many of the earlier-formed materials.

Weisberg, Michael K.↗
NASA NTRS1998

Technologies for Non-Destructive Evaluation of Surfaces and Thin Coating

A study was made on two commercially available terbium-doped silicate glasses. There is an increased interest in silicate glasses doped with rare-earth ions for use in high-energy particle detection and radiographic applications. These glasses are of interest due to the fact that they can be formed into small fiber sensors; a property that can be used to increase the spatial resolution of a detection system. Following absorption of radiation, the terbium ions become excited and then emit photons via 4f-4f electronic transitions as they relax back to the ground state. The lifetime of these transitions is on the order of milliseconds. A longer decay component lasting on the order of minutes has also been observed. While radiative transitions in the 4f shell of rare-earth ions are generally well understood by the Judd-Olfelt theory, the presence of a longer luminescence decay component is not. Experimental evidence that the long decay component is due, in part, to the thermal release of trapped charge carriers will be presented. In addition, a theoretical model describing the time evolution of the radiation-induced luminescence will be presented.

Manos, Dennis M.↗
NASA NTRS1996

Time Evolution of Radiation-Induced Luminescence in Terbium-Doped Silicate Glass

A study was made on two commercially available terbium-doped silicate glasses. There is an increased interest in silicate glasses doped with rare-earth ions for use in high-energy particle detection and radiographic applications. These glasses are of interest due to the fact that they can be formed into small fiber sensors; a property that can be used to increase the spatial resolution of a detection system. Following absorption of radiation, the terbium ions become excited and then emit photons via 4f-4f electronic transitions as they relax back to the ground state. The lifetime of these transitions is on the order of milliseconds. A longer decay component lasting on the order of minutes has also been observed. While radiative transitions in the 4f shell of rare-earth ions are generally well understood by the Judd-Olfelt theory, the pr'esence of a longer luminescence decay component is not. Experimental evidence that the long decay component is due, in part, to the thermal release of trapped charge carriers will be presented. In addition, a theoretical model describing the time evolution of the radiation-induced luminescence will be presented.

West, Michael S.↗
NASA NTRS2010

High C/O Chemistry and Weak Thermal Inversion in the Extremely Irradiated Atmosphere of Exoplanet WASP-12b

The carbon-to-oxygen ratio (C/O) in a planet provides critical information about its primordial origins and subsequent evolution. A primordial C/O greater than 0.8 causes a carbide-dominated interior as opposed to the silicate-dominated composition as found on Earth; the solar C/O is 0.54. Theory, shows that high C/O leads to a diversity of carbon-rich planets that can have very different interiors and atmospheres from those in the solar system. Here we report the detection of C/O greater than or equal to 1 in a planetary atmosphere. The transiting hot Jupiter WASP-12b has a dayside atmosphere depleted in water vapour and enhanced in methane by over two orders of magnitude compared to a solar-abundance chemical equilibrium model at the expected temperatures. The observed concentrations of the prominent molecules CO, CH4, and H2O are consistent with theoretical expectations for an atmosphere with the observed C/O = 1. The C/O ratios are not known for giant planets in the solar system, although they are expected to equal the solar value. If high C/O ratios are common, then extrasolar planets are likely very different in interior composition, and formed very differently, from expectations based on solar composition, potentially explaining the large diversity in observed radii. We also find that the extremely irradiated atmosphere (greater than 2500 K) of WASP-12b lacks a prominent thermal inversion, or a stratosphere, and has very efficient day-night energy circulation. The absence of a strong thermal inversion is in stark contrast to theoretical predictions for the most highly irradiated hot-Jupiter atmospheres.

Madhusudhan, Nikku↗
NASA NTRSDate not supplied

Machine Learning Applications to Metal-Silicate Equilibria and their Insights into Core Formation

An extensive number of studies have experimentally investigated how elements distribute between metal and silicate phases, to better constrain core-mantle chemical equilibrium. Here, we present a new database compiling all (to our knowledge) experimental data on liquid metal-silicate partitioning from 118 peer-reviewed publications. We applied various machine learning techniques to gain further insights into these partitioning equilibria and their dependencies. We performed a network analysis to investigate the relationship between experiments and partition coefficients, which enables visualizing gaps in the experimental dataset and biases related to varying experimental conditions and analytical setup. In addition, semi-empirical thermodynamic models are commonly used to extrapolate these chemical reactions to the wide range of pressure, temperature and compositional conditions of planetary differentiation. These models are based on linear regressions that assume continuous relationship between partition coefficients and experimental variables. Here, we considered random forest regressions, which are algorithms based on ensembles of decision trees and does not consider continuous effects of each variable. The application of this regression significantly improves the prediction of metal-silicate partitioning for several elements including Ni, Si and Cr. We will show how this new approach improves our understanding of elemental exchange between metal and silicate and their implications for the Earth’s core formation.

siderophile element↗
NASA NTRS2017

Effect of Silicon on Activity Coefficients of P, Bl, CD, SN, and AG in Liquid Fe-Si, and Implications for Differentiation and Core Formation

Cores of differentiated bodies (Earth, Mars, Mercury, Moon, Vesta) contain light elements such as S, C, Si, and O. We have previously measured small effects of Si on metal-silicate partitioning of Ni and Co [1,2], and larger effects for Mo, Ge, Sb, As [2]. The effect of Si on many siderophile elements could be an important, and as yet unquantified, influence on the core-mantle partitioning of SE. Here we report new experiments designed to quantify the effect of Si on the partitioning of Bi, Cd, Sn, Ag, and P between metal and silicate melt. The results will be applied to Earth, Mars, Mercury, Moon, and Vesta, for which we have excellent constraints on the mantle Bi, Cd, Sn, Ag, and P concentrations from mantle and/or basalt samples.

Righter, K.↗