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At least 1,117 records · Page 62
All sourcesNASA NTRSDOE OSTI
NASA NTRS1981

Search for optical coronal line emission from the X-ray sources Epsilon Orionis /B0 Ia/ and Kappa Orionis /B0.5 Ia/

A search was conducted for evidence of a coronal region at the base of the winds of Epsilon Ori and Kappa Ori, by means of high signal-to-noise observations at the forbidden lines of Fe X, at 6574 A, and Fe XIV, 5303 A. Both stars have been detected as soft X-ray sources, and show anomalously strong O VI lines in their UV spectra. Large coronal emission measures were expected from the total X-ray flux and Auger-enhanced ionization, but the fact that the iron coronal lines were not detected places new limits on the emission measure if the total temperature is in the range of 700,000-3,000,000 or more than 1,000,000 for Kappa Ori and 2,000,000 for Epsilon Ori. It is suggested that at least some of the X-rays arise, not from the base corona, but from source features farther out in the wind.

Nordsieck, K. H.↗
DOE OSTI2025

Spin‐State and Clustering Effects in Fe‐Complex Negolytes for Near‐Neutral Aqueous Redox Flow Batteries

Cost-effective redox-active materials are essential for advancing redox flow batteries (RFBs). Iron, with its abundance and suitability as a redox couple, is a promising candidate; however, achieving stable and fast redox reactions in aqueous RFBs remains a challenge. Here, this study presents an Fe-based negolyte stabilized by a hexadentate ligand, where Fe–ligand bonds are enhanced through intermolecular interactions. The sulfonate-substituted Fe complex exhibits a formal potential of −0.44 V versus Ag/AgCl and an exceptionally high rate constant of 0.69 cm s −1 . Near-neutral RFBs incorporating 0.5 M Fe complex show excellent cycling stability, with no discernible capacity fading over 300 cycles. This performance is attributed to intermolecular hydrogen bonds that reinforce Fe–ligand coordination and promote the formation of stable trimeric clusters. Operando electrochemical Raman spectroscopy and density functional theory reveal that π-backdonation from Fe(II) to the imino-phenolate moiety further stabilizes the complex after reduction. In contrast, the hydroxyl-substituted complex exhibits inferior stability due to weaker hydrogen bonding and less pronounced π-backdonation. These findings underscore the importance of ligand design and intermolecular interactions in developing cost-effective, high-performance redox-active materials for aqueous RFBs.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Ferromagnetism in a Semiconductor with Mobile Carriers via Low-Level Nonmagnetic Doping

We show that doped cubic iron pyrite, which is a diamagnetic semiconductor, becomes ferromagnetic when p-type doped. We furthermore find that this material can exhibit high spin polarization both for tunneling and transport devices. These results are based on first-principles electronic structure and transport calculations. This illustrates the use of p-type doping without magnetic impurities as a strategy for obtaining ferromagnetic semiconducting behavior, with implications for spintronic applications that require both magnetic ordering and good mobility. This is a combination that has been difficult to achieve by doping semiconductors with magnetic impurities. We show that phosphorus and arsenic may be effective dopants for achieving this behavior.

36 MATERIALS SCIENCE↗
DOE OSTI2024

Monitoring of In Situ Remediation Technologies with SIP

Deconvoluting the spectral induced polarization (SIP) signal is critical to developing SIP as a robust technology to monitor delivery and subsurface geochemical reactions. Therefore, the primary goal of this project is to elucidate the sensitivity of SIP to geochemical reactions occurring during subsurface remediation. This document presents progress for fiscal year (FY) 2024 toward field-scale SIP monitoring of amendment delivery and reactivity for subsurface remediation. An interdisciplinary critical review team was assembled to review historical SIP data collected under the Deep Vadose Zone program. Based on feedback from the team additional experiments were designed and initiated for the calcium citrate phosphate technology for in situ formation of apatite and additional analysis was conducted with data from sulfur modified iron experiments to consider the potential for scaling monitoring with SIP to the field. In addition, the team outlined a proposed framework for future evaluation of SIP for environmental remediation monitoring to be implemented over the next 2-3 years.

47 OTHER INSTRUMENTATION↗
NASA NTRS1954

Comparison of Performance of Experimental and Conventional Cage Designs and Materials for 75-millimeter-bore Cylindrical Roller Bearings at High Speed

The results of two investigations, one to determine the relative merits of four experimental and two conventional design 75-millimeter-bore (size 215) cylindrical roller bearings and one to determine the relative merits of nodular iron and bronze as cage materials for this size and type of bearing, are presented in this report. Nine test bearings were operated over a range of dn values (product of bearing bore in mm and shaft speed in r.p.m) from 0.3 x 10(6) to 2.3 x 20(6), radial loads for 7 to 1613 pounds, and oil flows from 2 to 8 pounds per minute with a single-jet circulatory oil feed. Of the six bearings used to evaluate designs, four were experimental types with outer-race-riding cages and inner-race-guided rollers, and two were conventional types, one with outer-race-guided rollers and cage and one with inner-race-guided rollers and cage. Each of these six test bearings was equipped with a different design cage made of nodular iron. The experimental combination of an outer-race-riding cage with a straight-through outer race and inner-race-guided rollers was found to give the best over-all performance based on limiting dn values and bearing temperatures.

Anderson, William J↗
NASA NTRS1993

Micro-zoning in minerals of a Landes silicate inclusion

There is an increasing number of meteorites with chondritic bulk composition but completely different textures than the conventional chondrite groups. Winonaites, Acapulcoites and silicate inclusions in IAB-iron meteorites have in common coarse grain size, highly equilibrated mineralogy with frequent 120 deg triple junctions and they record a significantly lower degree of oxidation than ordinary chondrites. They all have equilibration temperatures, based on Ca-exchange among pyroxenes, of around 900 to 1100 deg C. However, on cooling disequilibrium features may develop: (1) Olivine in IAB-inclusions has lower Fa-content than equilibrium Fs-content of pyroxenes requires; (2) CaO-zoning in olivine was established at temperatures of around 500 deg C, several hundred degrees below pyroxene equilibration temperatures. Obviously, olivine responded faster to changes in fO2 (Fa in olivine) and temperature (Ca-zoning) than pyroxenes. Differences in diffusion coefficients can readily explain the observed trends. Here we report on much more subtle zoning features in pyroxenes. TEM-observations reveal large compositional gradients in Ca, Na, Cr, Ti and Fe within the first micrometer of cpx and opx crystals. In summary, the data reflect the complicated subsolidus history of a chondritic mineral assemblage that was in thermodynamic equilibrium at about 900 deg C and cooled slowly from this temperature whereby oxidation reactions and different closure temperatures for various minerals and elements played an important role. The oxidation of P dissolved in metal and formation of phosphate, which is thermodynamically stable at low temperatures, is suggested to be responsible for most of the observed zoning.

Eisenhour, D. D.↗
NASA NTRS1993

A mineralized zone in Western Candor Chasma, Mars

Spectral evidence from Viking and Phobos orbiting spacecraft suggests the local development of crystalline ferric oxides in a small region within Mars' equatorial Valles Marineris canyon system. This is the same area noted for its anomalous coloration in Viking Orbiter image 583 A by McEwen. The unique hue of the region in Viking color data is due to a reduced green filter reflectance, relative to violet and red, in comparison to surrounding materials of similar albedo or average reflectance. For this reason, the region does not appear spectrally distinctive in later Survey Mission images which were acquired without the green filter. In high resolution, the spectral unit can be seen to correspond to two 20 km long depressions on the margins of Candor Mensa, a heavily eroded plateau-forming deposit on the canyon floor. Laminae are conspicuous in several places on the plateau, particularly where 15 to 20 cycles of alternating bright and dark laminae are exposed at approximately 200 meter vertical intervals. Laminae are also visible on the steep, vertically fluted cliffs to the south of this depression. Concentric laminae indicate a basis in the depression on the southeastern margin of Candor Mensa at the location of the less pronounced hue anomaly. A distinct lineation at the base of the scarp at the western end of the canyon transects mottled canyon floor deposits believed to be among the youngest in the Valles marineris. Water is implicated in the formation of the iron oxides, since the steep surfaces of layered sediments elsewhere on Candor Mensa show no evidence of unusual coloration despite the fact that these materials were deposited concurrently with the strata exposed in the depressions. This suggests that the mineralization is secondary in nature and developed locally in association with the depressions, which could have ponded surface runoff or groundwater seepage.

Geissler, P. E.↗
NASA NTRS2007

Aqueous Alteration on Mars

Aqueous alteration is the change in composition of a rock, produced in response to interactions with H2O-bearing ices, liquids, and vapors by chemical weathering. A variety of mineralogical and geochemical indicators for aqueous alteration on Mars have been identified by a combination of surface and orbital robotic missions, telescopic observations, characterization of Martian meteorites, and laboratory and terrestrial analog studies. Mineralogical indicators for aqueous alteration include goethite (lander), jarosite (lander), kieserite (orbiter), gypsum (orbiter) and other Fe-, Mg-, and Ca-sulfates (landers), halides (meteorites, lander), phyllosilicates (orbiter, meteorites), hematite and nanophase iron oxides (telescopic, orbiter, lander), and Fe-, Mg-, and Ca-carbonates (meteorites). Geochemical indicators (landers only) for aqueous alteration include Mg-, Ca-, and Fe-sulfates, halides, and secondary aluminosilicates such as smectite. Based upon these indicators, several styles of aqueous alteration have been suggested on Mars. Acid-sulfate weathering (e.g., formation of jarosite, gypsum, hematite, and goethite), may occur during (1) the oxidative weathering of ultramafic igneous rocks containing sulfides, (2) sulfuric acid weathering of basaltic materials, and (3) acid fog (i.e., vapors rich in H2SO4) weathering of basaltic or basaltic-derived materials. Near-neutral or alkaline alteration occurs when solutions with pH near or above 7 move through basaltic materials and form phases such as phyllosilicates and carbonates. Very low water:rock ratios appear to have been prominent at most of the sites visited by landed missions because there is very little alteration (leaching) of the original basaltic composition (i.e., the alteration is isochemical or in a closed hydrologic system). Most of the aqueous alteration appears to have occurred early in the history of the planet (3 to 4.5 billion years ago); however, minor aqueous alteration may be occurring at the surface even today (e.g., in thin films of water or by acid fog).

Ming, Douglas W.↗
NASA NTRS2007

The Use of Tribocharging in the Electrostatic Beneficiation of Lunar Simulant

Any future lunar base and habitat must be constructed from strong dense materials in order to provide for thermal and radiation protection. Lunar soil may meet this need. Lunar regolith has high concentrations of aluminum, silicon, calcium, iron, sodium, and titanium oxides. Refinement or enrichment of specific minerals in the soil before it is chemically processed may be more desirable as it would reduce the size and energy requirements required to produce the virgin material and it may significantly reduce the process' complexity. Also, investigations into the potential production of breathable oxygen from oxidized mineral components are a major research initiative by NASA. In this study. the objective was to investigate the use of tribocharging to charge lunar simulants and pass them through a parallel plate separator to enrich different mineral fractions. This technique takes advantage of the high Lunar vacuum in which much higher voltages can be used on the separation plates than in air. Additionally, the Lunar g1avity, only being 1/6 that of Earth, allows the particles more separation time between the plates and therefore enhances separation. For the separation studies, two lunar stimulants were used. The first simulant was created in-house, labeled KSC-1. using commercially supplied (sieved to 325 mesh) materials, and was composed of 40 wt. % feldspar ((Na,K,Ca)AlSi3O8;SiO2), 40 wt. % olivine ((Mg,Fe)2SiO4), 10 wt. % ilmenite (FeTiO3). and 10 wt. % spodumene (LiAlSi2O6) (pyroxene). The advantage of the in-house mixture is that the composition can he varied to simulate different soil compositions from different areas on the moon. This simulant was used to show proof-of-concept using the designed separator in air. The second stimulant was JSC-1. used for the vacuum experiments. JSC-1 is principally basalts, containing phases of plagioclase. pyroxene. olivine, and ilmenite. The JSC-1 was sieved to provide a 50-75 micron size range to correlate with the mean grain size found on the moon's surface [1]. Four different materials were investigated for the triboelectrification process; aluminum, copper. stainless steel, and PTFE. These materials were selected because they offer a wide variation in work functions (aluminum 4.28 eV, copper 4.65 eV. stainless steel 5.04 eV, and PTFE 5.75 eV). The difference between the work function of each material and the simulant influences the charge obtained by the grains. Each simulant was analyzed before and after separation using X-ray Photoelectron Spectroscopy (XPS) to determine mineral surface composition. In addition. Raman spectroscopy was performed on the JSC-1 before and after separation in vacuum to determine the mineral composition. Charge-to-mass (Q/M) measurements were performed using a fluidizing bed in air and passing the simulant through a static mixer of a particular material and collecting it in a Faraday pail grounded through an electrometer. To measure the Q/M in vacuum, a special device was constructed consisting of a heater/shaker cup that fed into a solid block of material (either PTFE, copper, or aluminum) in which a channel composed of a "zig-zag" series of inclines greater than 50 degrees has been cut. The voltage to the vibrating motor can be varied to control the amount of simulant passing through the channel. Figure I shows the Q/M measurements for JSC-1 tribocharged using the static mixers and the incline plane chargers in air, and the incline plane chargers in vacuum.

Trigwell, S.↗
NASA NTRS2020

TOI-1235 b: A Keystone Super-Earth for Testing Radius Valley Emergence Models around Early M Dwarfs

Small planets on close-in orbits tend to exhibit envelope mass fractions of either effectively zero or up to a few percent depending on their size and orbital period. Models of thermally driven atmospheric mass loss and of terrestrial planet formation in a gas-poor environment make distinct predictions regarding the location of this rocky/nonrocky transition in period–radius space. Here we present the confirmation of TOI-1235 b (P = 3.44 days, r(p)=1.738 (+0.087, -0.076) Rꚛ), a planet whose size and period are intermediate between the competing model predictions, thus making the system an important test case for emergence models of the rocky/nonrocky transition around early M dwarfs (R(s) = 0.630 ± 0.015 Rꙩ, M(s) = 0.640 ± 0.016 Mꙩ}$). We confirm the TESS planet discovery using reconnaissance spectroscopy, ground-based photometry, high-resolution imaging, and a set of 38 precise radial velocities (RVs) from HARPS-N and HIRES. We measure a planet mass of 6.91 (+0.75, -0.85) Mꚛ, which implies an iron core mass fraction of 20 (+15,-12)% in the absence of a gaseous envelope. The bulk composition of TOI-1235 b is therefore consistent with being Earth-like, and we constrain an H/He envelope mass fraction to be <0.5% at 90% confidence. Our results are consistent with model predictions from thermally driven atmospheric mass loss but not with gas-poor formation, suggesting that the former class of processes remains efficient at sculpting close-in planets around early M dwarfs. Our RV analysis also reveals a strong periodicity close to the first harmonic of the photometrically determined stellar rotation period that we treat as stellar activity, despite other lines of evidence favoring a planetary origin P= 21.8(+0.9, _0.8) days, m(p)sin i= 13.0 (+3.8,-5.3) Mꚛ) that cannot be firmly ruled out by our data.

Ryan Cloutier↗
DOE OSTI2024

Studies on the Vitrification Potential of High Risk Spent Nuclear Fuels

This research explored vitrification of U-Zr nuclear fuel that exhibits an explosion hazard when processed by common nitric acid dissolution. Glass frits were chosen based on properties that had been previously measured as well as being demonstrated successfully in production at the Defense Waste Process Facility (DWPF). Zirconium and Aluminum metal powders were chosen to represent the spent fuels after literature demonstrated that the potential phase that causes the issue for explosive reaction in the effluent stream is tied to the Zirconium-III phase field. DSC measurements were carried out on various simulants and waste forms to better understand thermal behavior of these materials. Zirconium (Zr) was tested with both nitric acid and the new effluent flowsheet that is under development by the SRNL Chemical Process Control (CPC) group. The nitric acid test did show the expected exothermic behavior as well as how the behavior is affected by particle size of the powders used. In contrast, the effluent samples did not show an exothermic peak. However, the concentration of metal in the samples was orders of magnitude lower than in the nitric acid testing and further testing of the effect of concentration on the exothermicity that could be measured confirmed a dampened signal. Tests were run that included frit, both DWPF Frit 510 and Iron Phosphate frit, exhibiting complex curves that included multiple endothermic and exothermic peaks during heating and cooling. The final crucible samples appear similarly to the bulk glasses pointing to these peaks being a part of the dissolution of the simulant into the base glasses.

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
DOE OSTI2023

A 2K Design for the Low Beta Quadrupoles Q1ApF/Q1BpF for the Interaction Region of the Electron-Ion Collider (EIC)

The forward hadron magnets of the planned electron-ion collider (EIC) at Brookhaven National Laboratory (BNL) present a set of unique challenges. In addition to the typical magnet requirements in terms of aperture, gradient, and field quality, the field leakage from the hadron magnets to the electron apertures must be negligible. Due to the close proximity of the two apertures the shielding solution for the electron beam can affect the field quality of the hadron magnets. Here, in this paper, a design for the Q1ApF/Q1BpF low beta quadrupoles based on NbTi Rutherford cable operating at 2K is presented. In this design the electron beam shielding and the required field quality in the hadron magnets are achieved using a set of cutouts in the iron yoke solely without resorting to active shielding. The chosen layout along with the key parameters are presented and their effect on hadron magnets in term of field quality and operational margins are also discussed.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2021

Effect of Polymer Removal on the Morphology and Phase of the Nanoparticles in All-Inorganic Heterostructures Synthesized via Two-Step Polymer Infiltration

Polymer templates play an essential role in the robust infiltration-based synthesis of functional multicomponent heterostructures with controlled structure, porosity, and composition. Such heterostructures are be used as hybrid organic–inorganic composites or as all-inorganic systems once the polymer templates are removed. Using iron oxide/alumina heterostructures formed by two-step infiltration of polystyrene-block-polyvinyl pyridine block copolymer with iron and aluminum precursors from the solution and vapor-phases, respectively, we show that the phase and morphology of iron oxide nanoparticles dramatically depend on the approach used to remove the polymer. We demonstrate that thermal and plasma oxidative treatments result in iron oxide nanoparticles with either solid or hollow morphologies, respectively, that lead to different magnetic properties of the resulting materials. Our study extends the boundaries of structure manipulations in multicomponent heterostructures synthesized using polymer infiltration synthesis, and hence their properties.

32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATI↗
NASA NTRS1981

Recombination coefficients for iron ions

Radiative recombination coefficients for all Fe ions are calculated by use of the Milne relation of detailed balance. Analytic fits are made to the dielectronic recombination rates computed by Jacobs (1977) and the Burgess general formula (1965). Higher level rates are treated hydrogenically by a quantum defect method based on the energies of the levels. Recombination coefficients for Fe I to Fe 26 are listed.

Woods, D. T.↗
NASA NTRS1984

Cosmic ray exposure ages of iron meteorites, complex irradiation and the constancy of cosmic ray flux in the past

While previous calculations of potassium ages assumed a constant cosmic ray flux and a single stage (no change in size) exposure of iron meteorites, present calculations relaxed these constancy assumptions and the results reveal multistage irradiations for some 25% of the meteorites studied, implying multiple breakup in space. The distribution of exposure ages suggests several major collisions (based on chemical composition and structure), although the calibration of age scales is not yet complete. It is concluded that shielding-corrected (corrections which depend on size and position of sample) production rates are consistent for the age bracket of 300 to 900 years. These production rates differ in a systematic way from those calculated for present day fluxes of cosmic rays (such as obtained for the last few million years).

Marti, K.↗
NASA NTRS1992

Asteroid core crystallization by inward dendritic growth

The physics of the asteroid core crystallization process in metallic asteroids is investigated, with special attention given to the initial conditions for core crystallization, the manner of crystallization, the mechanisms acting in the stirring of the liquid, and the effects of elements such as sulfur on crystallization of Fe-Ni. On the basis of theoretical considerations and the published data on iron meteorites, it is suggested that the mode of crystallization in asteroid core was different from the apparent outward concentric crystallization of the earth core, in that the crystallization of asteroidal cores commenced at the base of the mantle and proceeded inward. The inward crystallization resulted in complex dendritic growth. These dendrites may have grown to lengths of hundreds of meters or perhaps even as large as the core radius, thereby dividing the core into separate magma chambers.

Haack, Henning↗
NASA NTRS2007

A Hard-X-Ray Telescope Science Enhancement Package for the Constellation-X Mission

We present a science enhancement package (SEP) for NASA's planned Constellation-X mission submitted in response to a call for white papers. The call solicited proposals for either extending the bandwidth of Con-X to higher energies or enhancing the low-energy spectral resolution. The ground rules were that enhancement package should cost no more than $100M and weigh no more than 100 kg. The nickel-replicated-optics team responded with a stand-alone hard-x-ray telescope SEP concept. This consisted of two mirror modules, each with approximately 70 multilayer and iridium-coated shells, and two corresponding cadmium-zinc-telluride-based focal plane detectors. Addition of this package permits measurement of the hard-x-ray continuum up to 30-40 keV, which is essential for a quantitative measurement of the spectrum of gravitationally broadened iron lines that appear in the spectra of many black hole candidates. Full details of the instrument will be presented showing trades in energy bandwidth and effective area together with the full science justification for the enhancement package.

Ramsey, Brian↗
NASA NTRS2008

How Deep and Hot was Earth's Magma Ocean? Combined Experimental Datasets for the Metal-silicate Partitioning of 11 Siderophile Elements - Ni, Co, Mo, W, P, Mn, V, Cr, Ga, Cu and Pd

Since approximately 1990 high pressure and temperature (PT) experiments on metal-silicate systems have showed that partition coefficients (D) for siderophile (iron-loving) elements are much different than those measured at low PT conditions. The high PT data have been used to argue for a magma ocean during growth of the early Earth. Initial conclusions were based on experiments and calculations for a small number of elements such as Ni and Co. However, for many elements only a limited number of experimental data were available then, and they only hinted at values of metal-silicate D's at high PT conditions. In the ensuing decades there have been hundreds of new experiments carried out and published on a wide range of siderophile elements. At the same time several different models have been advanced to explain the siderophile elements in the earth's mantle: a) intermediate depth magma ocean; 25-30 GPa, b) deep magma ocean; up to 50 GPa, and c) early reduced and later oxidized magma ocean. Some studies have drawn conclusions based on a small subset of siderophile elements, or a set of elements that provides little leverage on the big picture (like slightly siderophile elements), and no single study has attempted to quantitatively explain more than 5 elements at a time. The purpose of this abstract is to update the predictive expressions outlined by Righter et al. (1997) with new experimental data from the last decade, test the predictive ability of these expressions against independent datasets (there are more data now to do this properly), and to apply the resulting expressions to the siderophile element patterns in Earth's upper mantle. The predictive expressions have the form: lnD = alnfO2 + b/T + cP/T + d(1Xs) + e(1Xc) + SigmafiXi + g These expressions are guided by the thermodynamics of simple metal-oxide equilibria that control each element, include terms that mimic the activity coefficients of each element in the metal and silicate, and quantify the effect of variable oxygen fugacity. Preliminary results confirm that D(Ni) and D(Co) converge at pressures near 25-30 GPa and approximately 2200 K, and show that D(Pd) and D(Cu) become too low at the PT conditions of the deepest models. Furthermore, models which force fit V and Cr mantle concentrations by metal-silicate equilibrium overlook the fact that at early Earth mantle fO2, these elements will be more compatible in Mg-perovskite and (Fe,Mg)O than in metal. Thus an intermediate depth magma ocean, at 25-30 GPa, 2200 K, and at IW-2, can explain more mantle siderophile element concentrations than other models.

Righter, Kevin↗